Question:
This post has been up for 4-5 days now.  I flagged it originally when it was first posted and that flag aged away, I have now flagged it again and it's still here.  We have one user that shares part of the posters name but I am unsure if they are connected in any way or if that name references the linked user.

Do we need more moderators to handle this?  What is the process for having these removed?

Answer:
The post has now been deleted and the user destroyed due to spam, so thank you for bringing this up.
It either must have come up after I cleaned out the inbox or I must have overlooked it.
Yes, we do need another moderator. I would have loved to be at a point by now that we could have had elections as part of a fully public SE site, but we've still got a few hurdles to overcome as a community.
I'll double check what the options are for bringing on new moderators at this stage and post back to Meta.


Question:
I can't find an answer to this question on the "mother" meta website; hope this is not related to my choice of words in the search box.

The statistics of the 3D Printing on Area51 show that only few items (questions and visits per day) are not up to par and need work. Do those need to reach a level of let's say "okay" before the site can loose the Beta stage?

I'm interested to know what would be the requirements to get out of the Beta stage.

Update September 5, 2019:

It appears that the "visits per day" is "excellent" with close to three thousand visits. The "questions per day" still lack behind with a 3.0 value ("needs work") while more than 5 is considered "healthy". All further stats seem to be "okay" or "excellent".

Answer:
This post,
3D Printing SE Beta Status
, by tbm0115 highlights the
three main
sticking points (IMHO clearer than the Area 51 page):
Questions per day
Users vs Reputation
Visits per day
Once those reach the required levels then that should be it. So, there is quite a way to go...
The stats can be seen here,
3D Printing Area51 site
:
Stats progress
Note: Only
changes
are shown (no date information)
Questions per day
2.1
->
1.9
1.6
2.1
2.7
2.1
1.7
2
2.4
3.0
2.5
3.9
2.8
3.3
3
2.7
2
1.9
2.1
2.2
2.4
Answer rate
96 %
->
93 %
95 %
96 %
97 %
98 %
96 %
95 %
94 %
88 %
87 %
Users
200+ reputation
56/150
->
103/150
113/150
139/150
144/150
151/150
161/150
164/150
179/150
194/150
282/150
*
351/150
358/150
359/150
2,000+ reputation
4/10
->
8/10
9/10
10/10
11/10
12/10
14/10
17/10
19/10
22/10
*
27/10
3,000+ reputation
3/5
->
4/5
6/5
7/5
8/5
9/5
11/5
12/5
*
14/5
Answers per question
ratio is
2.0
-> 1.9
Visits per day
753
->
4
2324
2648
2675
2774
2844
3041
3707
2934
3290
8756
7146
6773
6718
6682
6627
6582
6247
6207
6081
5929
5541
5469
*
This change in the number of users with
X
reputation is, in part, due to the move from +5 to +10 reputation for upvoted questions on
13 Nov 2019
(see also
Upvotes on questions will now be worth the same as upvotes on answers
).
Alternative Stats presentation
Latest statistic shown in bold -> chronological history shown thereafter
Questions per day
2.4
->
2.1
1.9
1.6
2.1
2.7
2.1
1.7
2
2.4
3.0
2.5
3.9
2.8
3.3
3
2.7
2
1.9
2.1
2.2
Answer rate
87 %
->
96 %
93 %
95 %
96 %
97 %
98 %
96 %
95 %
94 %
88 %
Users
200+ reputation
359/150
->
56/150
103/150
113/150
139/150
144/150
151/150
161/150
164/150
179/150
194/150
282/150
*
351/150
358/150
2,000+ reputation
27/10
->
4/10
8/10
9/10
10/10
11/10
12/10
14/10
17/10
19/10
22/10
*
3,000+ reputation
14/5
->
3/5
4/5
6/5
7/5
8/5
9/5
11/5
12/5
*
Answers per question
ratio is
1.9
->
2.0
Visits per day
5469
->
753
4
2324
2648
2675
2774
2844
3041
3707
2934
3290
8756
7146
6773
6718
6682
6627
6582
6247
6207
6081
5929
5541
Additional points of note
The stats above aren't really the be all to end all... there are a few other considerations that I came across here,
in this answer
, to
“Graduation” of this Community
:
A number of 10k+ users (
n
> 3 ) are required to access mod tools
A number of 3k+ users (
n
> 10 ) are required to be able to fully vote
The final hurdle
The main sticking point, according to this meta post on Ethereum,
Congratulations! Ethereum is graduating!
, is 10 questions per day, which we are a long way from, and seems to be the last remaining issue. A link (
Graduation, site closure, and a clearer outlook on the health of SE sites
) from the Ethereum meta post to Meta.SE states:
When a site starts to consistently receive 10 questions/day, we’ll consider it for graduation.
No graduation, but losing the Beta label...
Apart from graduation, SE management has recognised that small sites (with an active community) struggle to reach the 10 questions/day consistently. For sites that have been waiting to get out of Beta by graduation for 7-8 years, SE has decided to drop the Beta label. Please see
Congratulations to our 29 oldest beta sites - They're now no longer beta!
.
CSV Format
Format:
```
heading,data,date,data,date,...,data,date
```
Date format:
```
YYYYMMDD
```
```
```
*Questions per day*,2.1,20170317,1.9,20180525,1.6,20180705,2.1,20180707,2.7,20180815,2.1,20180903,1.7,20181015,2,20181106,2.4,20190327,3.0,20190905,2.5,20191119,3.9,20210121,2.8,20210411,3.3,20210423,3.3,20210424,3,20210425,3,20210426,2.7,20210427,2,20210506,2,20210508,1.9,20210511,2.1,20210514,2.2,20210525,2.4,20210526
*Answer rate*,96,20170317,93,20180525,95,20180705,96,20180707,96,20180815,97,20180903,98,20181015,98,20181106,96,20190327,95,20190905,94,20191119,88,20210121,88,20210411,88,20210423,88,20210424,88,20210425,88,20210426,88,20210427,88,20210506,88,20210508,87,20210511,87,20210514,87,20210525,87,20210526
*200+ reputation*,56,20170317,103,20180525,113,20180705,139,20180707,144,20180815,151,20180903,161,20181015,164,20181106,179,20190327,194,20190905,282,20191119,351,20210121,358,20210411,358,20210423,358,20210424,358,20210425,358,20210426,358,20210427,358,20210506,358,20210508,358,20210511,358,20210514,359,20210525,359,20210526
*2,000+ reputation*,4,20170317,8,20180525,9,20180705,10,20180707,11,20180815,12,20180903,14,20181015,14,20181106,17,20190327,19,20190905,22,20191119,27,20210121,27,20210411,27,20210423,27,20210424,27,20210425,27,20210426,27,20210427,27,20210506,27,20210508,27,20210511,27,20210514,27,20210525,27,20210526
*3,000+ reputation*,3,20170317,4,20180525,6,20180705,7,20180707,7,20180815,7,20180903,7,20181015,8,20181106,9,20190327,11,20190905,12,20191119,14,20210121,14,20210411,14,20210423,14,20210424,14,20210425,14,20210426,14,20210427,14,20210506,14,20210508,14,20210511,14,20210514,14,20210525,14,20210526
*Answers per question*,2.0,20170317,1.9,20180525,1.9,20180705,1.9,20180707,1.9,20180815,1.9,20180903,1.9,20181015,1.9,20181106,1.9,20190327,1.9,20190905,1.9,20191119,1.9,20210121,1.9,20210411,1.9,20210423,1.9,20210424,1.9,20210425,1.9,20210426,1.9,20210427,1.9,20210506,1.9,20210508,1.9,20210511,1.9,20210514,1.9,20210525,1.9,20210526
*Visits per day*,753,20170317,4,20180525,2324,20180705,2648,20180707,2675,20180815,2774,20180903,2844,20181015,3041,20181106,3707,20190327,2934,20190905,3290,20191119,8756,20210121,7146,20210411,6773,20210423,6718,20210424,6682,20210425,6627,20210426,6582,20210427,6247,20210506,6207,20210508,6081,20210511,5929,20210514,5541,20210525,5469,20210526
```
```
Auto-generate markdown lists and CSV:
GitLab: SE3DP_PlotterScraper
/
Area51Scraper.py
Graphical representation
Graph script:
GitLab: SE3DP_PlotterScraper
/
StackExchange3DP_6.py


Question:
At the moment there are two tags related to fans:

print-fan

fans

If you look at the topics there is no distinction which fans are meant, this must be read in the questions.

Should we create separate tags for specific fan applications?

Answer:
There aren't that many topics labelled with either one of the existing tags, so re-tagging will not be a problem.
Indeed these tags are generic tags and do not cover the range of fans specifically for the application they are used for. There are 3 types of applications for fans in 3D printers,
electronics cooling fans (board/stepper/stepper drivers cooling),
part cooling fans (filament cooling after deposition), and
cold end cooling fans (extruder cold end cooling).
How about making 3 categories and re-tag? (in the same order as the previous list)
electronics-fan
,
part-cool-fan
(or
filament-fan
or
print-fan
), and
extruder-fan
.
Alternatively, we could just use a single tag and let the poster make sure that he explains clearly which fan is used.


Question:
I'm seeing a current trend towards many questions only receiving a single answer, and according the the Area 51 stats, we ought to have an average closer to 2.5. Granted that some questions are really only in need of a single (obvious) answer, I think we're missing something here.

I've seen a few questions with 'answers in the comments', which is understandable if a user wants to make a drive-by quick tip, but we should really be encouraging them to try and come back later to get the points due to them.

Are users put off by an expectation that a wrong answer might lose them rep? Or by an overly high (assumed) expectation for making an answer?

What can we do to raise ApQ, without dropping answer quality significantly?

Some thoughts from IoT meta on why more answers are good.

Answer:
Well done for bringing this up. I was looking at those numbers too.
Referring to
this post
, almost all of the stats are improving (albeit) slowly, except for one, the ApQ
Are users put off by an expectation that a wrong answer might lose them rep?
It seems that way. Without wishing to provide a link to the actual comment, I noticed a comment the other day that suggested as much, and a nicely detailed comment was left instead.
To be fair, I feel that way sometimes, and often hesitate (maybe rightly so to save myself from spamming the site) in posting questions on SE.Meta, as there are a number of drive-by downvoters there
1
. Unless you have a definite bug that you are able to document clearly or have a well rounded proposal that can be implemented easily, then your question may end up downvoted. This is probably rightly so, TBH, in most cases, but nevertheless it can be discouraging.
If you don't have much hard-earned rep then you may be less willing to risk it by posting a informative answer, that only answers half the question.  Is that a bad thing? Well, it is a double edged sword. It is a good thing, because that promotes good solid answers, but with the downside that you point out (a lack of multiple answers per question).
What can we do? Probably, not much other than creating a small community by promoting a friendly environment and communicating more clearly... Inviting people to chat in the chatroom, being more welcoming (with Hi and welcome), actually helping people without the old "Did you google this?" immediately.  All of these things help a lot. And which we seem to have developed of late. So we seem to be getting there.
I know that a number of members have already been adding answers to single answer questions as well as tackling the unanswered queue too. The more people that help the better...
1
Don't get me wrong, I looove (justified) downvotes, but I would like to know
why
.


Question:
Just a random thought, and if I wasn't asking the question myself I'd probably down vote it, but...  are screenshots the best way to show printer settings, or would a text version be better?

Ok, yes, a screenshot is probably easier to do and post, and will show a familiar UI and be easy on the eye and make it easy to notice errors/improvements.

However, having a (standardised) text format would make it searchable. After all, other sites always say, "please copy and paste the error rather than post a screenshot" - because the text in a screenshot is not searchable.

Yes, it could/would be a pain to enforce this rule (is it possible to easily export printer settings as a file file?) and/or edit the text version of the settings into the post.

This is probably a daft "thought experiment" of an idea... but I thought I'd float it anyway.

Answer:
The problem with settings is that there are so much settings, if OP's are asked to post certain settings the OP or the one that helps might miss some other parameters that would be visible in a screenshot. I was able to spot a few problems already using the screenshots.
Another thought: "What would you gain by searchable settings?". In case of error messages I am absolutely convinced that you should, but I do not see the advantage for searching/indexing.
What does being searchable actually add? Questions and answers are usually not that long to spot certain text when you are on a page, what does it add if it is searchable for the site? E.g. if I would search for
```
combing
```
, you now get some hits, if everyone posts the settings in text you suddenly have many more you need to scroll through...


Question:
I don't want to ask off-topic and opinion questions here, but I would like to find a cadre of others dialing in their devices.
Any ideas?

Answer:
I stumbled across this forum/group,
Original Prusa i3 MMU2S & MMU2
, amongst all of the other
Prusa printers forums
on the
Prusaprinters blog
, which seems fairly active.
In particular, the
User mods - OctoPrint, enclosures, nozzles, ...
page seems like it might be what you are looking for.


Question:
Should we really close this question:  3d printer part clones from china - legality..?

Are legal questions on topic? We have a legal section in the Game plan - What is on-topic? and a legal tag.

Answer:
I say allow them.
To let you know what's out there, I work at
Hyrel
.
Our printers can take
spindle (milling) heads and additional axes
, and even
diode
and
CO2 lasers
, and they all operate on the same gcode - we tell people E is for Emit as well as Extrude. We even have a
TIG welding
attachment.
We also run our
Fadal CNC machines
on our printer software and firmware.
To many people this is a natural progression for a well-built 3D positioning system, and I encourage a broader definition.


Question:
We should do some tag maintenance, especially regarding printers to make them easier to read. Use an answer to propose a change, merge or split. Discussions for each change should go into the comments of each change.

Some things are easier than others:

Renaming a tag can be done with mod tools.

Alias/Synonyms are reasonably quick, often follow along renaming

Some tags need manual (separation).  Sifting through what is and what isn't this tag has to be done to separate the stuff. It can be noisy to the front site but has to be done.

Answer:
Printers: Anet series
aneta2
->
anet-a2
aneta6
->
anet-a6
aneta8
->
anet-a8
Type:
renaming
Status:
Done
by
Greenonline


Question:
Every time I write "Cura" in a question or answer, it gets edited to "Ultimaker Cura", most recently resulting in awkward verbose repetition that required additional edits to fix. I don't see any justification for requiring use of official verbose names for software products that can be clearly identified by a well-known shorter name. For example on computing SE sites we don't force users to write "Microsoft Windows" or "Redhat Linux" in contexts where "Windows" or "Redhat" would be understood. And even on this site I don't recall every mention of "Ender 3" getting edited into "Creality Ender 3".

Is such a policy (it's effectively a policy, since it's enforced by edits made by a moderator) appropriate for this site?

For what it's worth, as a new-ish contributor to this SE site, having nitpicky edits to all of my posts does not make me feel welcome and appreciated.

Answer:
Printers: Anet series
aneta2
->
anet-a2
aneta6
->
anet-a6
aneta8
->
anet-a8
Type:
renaming
Status:
Done
by
Greenonline


Question:
Half a year passed since Tag Maintenance Summer 2019. A lot was done, some wasn't, so cleanup and rinse and repeat: Let's do some tag maintenance, especially regarding printers to make them easier to read. Use an answer to propose a change, merge or split. Discussions for each change should go into the comments of each change.

Some things are easier than others:

Renaming a tag can be done with mod tools.

Alias/Synonyms are reasonably quick, often follow along renaming

Some tags need manual (separation).  Sifting through what is and what isn't this tag has to be done to separate the stuff. It can be noisy to the front site but has to be done.

Answer:
Laundry list:
Open
Filled PLA
Repair vs. Maintenance
Done
e3d
Monoprice
Creality
Prusa


Question: As the question states, should bed and build-plate be merged? Basically, both tags refer to the same part of the printer; bed should be a synonym for build-plate.

Answer:
Edit: I like Trish's suggestion best.
I vote
no
. Our (Hyrel) printers have, on some models, a thick aluminum
bed
that can reach 200C, but we expect users to mount different
build-plate
s on it, depending on what material they're printing with. These can be coated with PEI, garolite, polycarbonate, or others; or they can be commercial build plates like GeckoTek or Anycubic Ultrabase.
You heat the bed. You print on the build plate. In some cases, these may be a single item.


Question:
Currently, pure CAD questions are out of scope of our Stack, but we have quite some cases that edge, where the question about the CAD is about how to make a model printable or design principles or such.

Where do we draw the line in the sand? This was once discussed in 2016, but no conclusive answer defined.

Answer:
I struggled with the same question since I saw the edit, good that you brought this to Meta! Thanks!
As the community of regular and active members is limited, I think it is okay to welcome people in a comment or an answer. It would be a shame to scare people away after their first question, resulting in abandoned questions and unaccepted answers. But, we do need to conform to the Q&A format and sometimes need to remind people this isn't a forum of threaded messages and we do have some rules to participate. We have created some
standard comments
that welcome and thank new members but at the same time lead them to the rules of the site.
It might be a good idea to approach first time (SE) members friendly. Welcoming comments can and tend to be deleted after a while when users aren't new anymore (everybody can raise a flag on a comment to vote for
”It's no longer needed"
). So option 4 would be my preferred option.
Personally I think this site is more welcoming than larger sites as SO for instance. My first experiences at SO didn't make me feel welcome.


Question:
Our site has the default Stack Exchange logo (text balloon with text 3D), is it possible to change this logo?

I was thinking of something like this:

or

If it is possible, we could try to write out a competition and vote! E.g. instead of the lines, the printed image of 3D

Answer:
Yes, we can! Or at least discuss if we like a different logo.
From
this answer
on Meta Stack Exchange question "
What's the process to change a site logo?
" we can read:
If you have an issue with a logo on a site, the best place to start is to open a discussion on that site's meta. Tag it
discussion
and
design
, and see what the overall community feeling is.
Another part reads:
Community managers
monitor per-site metas, so if/when the discussion concludes and the site's community largely supports a change, they can bring your concerns to the design team.
There is no specific mention if Beta state sites can modify the logo, Beta sites share the smae layout set out by the Stack Exchange designers:
Our designers come up with the overall site design (including the logo), with some input from the communities. (With the exception of sites that are still in beta or have only recently graduated - those all share the same design.)
However, we can start a discussion whether we would like to have a different logo/favicon. Feel free to add your thoughts ans an aswer to the question.


Question: When I've printed an object I've had to choose between high resolution and quick prints.  What techniques or technologies can I use or deploy to speed up my high resolution prints?

Answer:
You could experiment with slicing. For example, you might not need high resolution all over the object, but you can speed up some straight parts by using greater layer high there. See a
part of Slic3r manual
about such thing.
It is also possible to print thicker infill every Nth layer, see
Infill optimization
in Slic3r.
Other slicers might have those features as well.


Question:
I would like to buy a 3D printer, but I'm concerned about the health risks that are associated with its operation. Some groups of scientists say it can be harmful for humans.

What do I need to consider before buying a 3D printer if I care about my health? Are there any safe printers?

Answer:
Almost all 3D printers have issues that could cause health problems.
FDM/FFF printers heat plastic to a temperature that may cause it to off-gas, and these byproducts may not be healthy.
SLA printers often use epoxies that may off-gas, or may be somewhat toxic prior to being cured.
Powder based printers can also off-gas, in addition to the powder itself presenting a possible hazard.
Many hobbyist and small companies dance around the problem, and suggest that the machines always be used in well ventillated areas.  Professional machines often have filters and ventillation systems built in.
Rather than trying to find a "perfectly safe" 3D printer, spend some time deciding what you want to use one for, find printers suitable for your use, and expect that you'll need to provide reasonable ventilation for almost any printer.  Plan your installation for that, and you should be able to make any printer safe for your required use.
If, however, you plan on setting up a printer farm with many printers, and plan to have yourself or others spend significant time operating them, I suggest you work with a health and safety professional and have them identify possible hazards and plan mitigation.


Question: I know the minimum layer height will effect how detailed of an item you can print and the amount of time it takes to print something, but is it necessary to have an extremely low minimum layer height if you plan to print only larger objects?

Answer:
As with any manufacturing process, you'll need to learn to "use the right tool for the job". It depends on the requirements of the part. To answer your question, I would suggest using a larger layer height for the sheer fact of reducing print time on larger objects.
However, it depends on the part and how small the details are on the part. If your part has sharp edges that are required for the proper functionality of the part, then you'll want to use a smaller layer height. Or if your part fits into another part, you'll probably want to use a smaller layer height.
Another variable might be whether or not post-processing is necessary. Is this part going to be purposefully printed larger/rougher with the idea to use a Dremel later to smooth everything out? If yes, then use a larger layer height.


Question:
Plastic is used in 3D FDM/FFF printing partly because it had a wide temperature range for its glass state - where it can be flowed with some force, but won't flow due only to gravity.

Most metals have a very narrow, or non-existant, glass state.  They transition from solid to liquid with almost no flowable-but-not-liquid state.

Are there any metals or alloys that display a glass transition state?

Answer:
I"m no expert on this, but the article at
https://en.wikipedia.org/wiki/Amorphous_metal
may be relevant for you.
There are some special alloys, such as gold/silicon and various titanium-based ones, that become "bulk metal glasses" if cooled extremely quickly (for example, by sputtering onto a spinning cold surface). The speed of cooling prevents crystal formation. Early BMGs were quite strong but brittle; improvements have reduced brittleness and required cooling speed.


Question: What are the main differences when using ABS over PLA and vice versa?

Answer:
Paraphrasing
this
site. Feel free to add suggestions in the form of comments and I will try to incorporate them.
Summary
ABS: Stronger, machinable, more flexible, and more temperature
resistant than PLA. Typically printed on a heated bed. Warping is a common problem when printing ABS.
PLA: Wider range of filaments available, easier and in some cases faster to print. Not as strong as ABS and the fact that its biodegradable could be seen as both a benefit and a drawback.
Material Properties:
ABS: Strong plastic with mild flexibility. Naturally beige in color. Can be filled and sanded. Higher temperature. Easy to recycle.
PLA: Not as strong as ABS but more rigid. Naturally transparent. More difficult to fill and sand. Can sag in hot temperatures. Sourced from organic matter so it can be broken down in commercial compost facilities.
Part Accuracy:
ABS: Part warping is a significant issue. Sharp corners will often be rounded.
PLA: Less heat required contributes to less warping. Becomes more liquid at common extruder temperatures so finer details can be printed.
Safety and Handling:
ABS: Strong burning/melting plastic smell is present when printing ABS. Health concerns have been raised regarding airborne ultrafine particles generated while printing with ABS (
ref
). ABS will absorb moisture causing popping when the moisture enters the hot end. This leads to discontinuities in the print job.
PLA: Doesn't smell as strongly when printing due to its organic nature. Moisture can also be absorbed into PLA and can irreversibly damage it.


Question:
My MakerBot printer supports only two filaments at the same time.

What are techniques to print objects with more than two colors for one object?

Answer:
The most obvious solution is to pause the print and swap filament for another color.
Another option is to
splice pieces of filament
together, though this does not allow very precise control of when the switch happens. There is also a device that can automatically slice filament this way.
Finally, another option that uses very little external equipment is to
use (permanent) markers to colorize light-colored filament
.
Other options include upgrading to a printer with more hotends, or installing a hotend with multiple filament inputs and one outputs, but these options would involve significantly changing your printer setup.


Question: I'd like to print modifications for my bird feeder, both to patch over the hail damage from last summer and to try to deter the neighborhood squirrels.  I have an FDM printer (and experience with nylon, ABS, and PLA, though don't restrict answers to those if there's something else that's better), what kind of filament would stand up best to daily exposure to sun, rain, snow, etc?

Answer:
PET(G) is a strong contender. It is very strong and water-resistant, and as such is often used to make pop bottles.
PLA has a reputation for being "biodegradable" and therefore it is often discouraged to use PLA outside and/or in contact with water. However, PLA only biodegrades under very specific conditions which it won't generally be exposed to so it can be used (though, as a harder and less flexible material it is more likely to be damaged by hail).
ABS and Nylon are good choices as well. Basically, any plastic you have on hand will last for years, even in an outside application.


Question:
The surfaces of my printed parts using PLA plastic look rough and uneven.

Would changing filament to a better one make any difference?

If not, what kind of methods can I use to achieve a smoother finish for my for 3D-printed objects?

Answer:
It is called
Acetone Finishing
Basically the 3D printed part stays in acetone vapor and the outer shell turns to smooth surface. I have heard that it works better with ABS.
This article shows how
with videos
:
(
Acetone Finishing on PLA
- dead link).
New link:
Acetone Finishing on PLA


Question:
With an ABS or PLA extrusion 3D printer, are there any potentially negative quality differences that could occur if I try to print at a higher resolution?

I am not concerned about print time as the equipment is not under high demand.  I am, however, worried the device may be more prone to fracture, likely to have defects, or have other issues I cannot currently imagine.

Answer:
The biggest effect I've see on resolution is due to plastic stress due to thermal gradients.
The higher resolution prints build up more layers of material, and each layer has a cumulative effect on thermal stress.  The upper layers pulling up more as they cool, and the lower layers curling up more strongly as the layer count is increased.
To counteract this, a heated (or even just a draft free) enclosure makes a big difference.  Having a heated print bed helps significantly, as long as the bed itself resists deformation (a sheet metal or PCB bed will bend more than glass under the same tension, for instance).
The actual plastic strength, however, appears increased.  Laying down thinner layers of material appears to increase the bond strength between layers.


Question:
I would like to print parts (e.g. jewellery) for use which I don't want to look or feel like a plastic, but metal-like, so briefly people won't see much difference.

Are there any specific type of home-printers that can achieve that? Or it's rather kind of filament that you should use?

Answer:
If you'd like to print on RepRap like
FDM printers
, you cannot print from metal, but you can use some filament that tries to look like metal. I have good experience with
Bronzefill
, but there are plenty of others, just Google for
metal filament 3d printing
. Note that sometimes the parts need to be post-processed with a
rock tumbler
. There are
several open source DIY tumblers
you can build and use.
If you actually want to print from metal, you would need SLS (
Selective laser sintering
) printer, which is much more expensive.


Question:
My printed parts consist rafts, supports and other extraneous filament when printing with ABS or PLA.

What are efficient general techniques of removing them?

Answer:
The best way to get rid of them is to change the design of the printed object to make them unnecessary.
Instead of printing the one part with support material, the piece can be split into two or more parts which can be printed without support material and assembled after the printing.
Given that this is not always fully possible, a convenient way to get rid of additional structures is to use a different fillament for them that can be removed easily.
This list of printing materials
includes Polyvinyl Acetate (
PVA
), which is water soluble. You can wash the support material away given that your actual printign material is not water soluble. Here's a quote from the website (emphasize mine):
PVA (Polyvinyl Acetate) filament prints translucent with a slightly yellow tint and is
primarily used as a 3D printing support material
because it is water-soluble, meaning that
it will dissolve when exposed to water
(and so MUST be kept dry prior to use). PVA is most often used with 3D printers capable of dual extrusion: one extruder printing a primary material (such as ABS or PLA) and the other printing this dissolvable filament to provide support for overhanging features. PVA 3D printer filament is available in 1.75mm and 3mm.


Question:
I would like to understand the differences between rafts, skirts and brims. They appear in the software which I'm using to edit my 3D objects.

Can anybody elaborate what are these and what are the main differences between them?

Answer:
All three of these features are used to improve the quality and success rate of prints, especially those failing due to issues on the first few layers, or due to the small size of the first layer.
Raft
A raft is a horizontal feature made as the first few layers of a print, and is used to help with bed adhesion issues, primarily used with ABS. The first few layers printed are the brim (typically prismatic), with the part itself on top of it (with a small separation distance to aid in separation, to allow the part to be removed from the raft). This separation distance needs to be adjusted to allow the first layer of the actual part to adhere, but also for the raft to be removed easily.
Skirt
A skirt is a single-layer feature designed to help extruder priming and to establish a stable filament flow for an optimal first layer. They are generally a few passes around the first layer "footprint" in the rough shape of the first layer, but they do not touch the part itself or help adhesion directly (although having a primed and ready extruder helps extrusion on its own).
Brim
A brim can be considered a skirt touching the first layer shape. It is used to help adhesion, and increases the first layer surface area (thus having more area to adhere to the bed). Brims are best used for parts with small first layers that fail to adhere properly. They are generally done as perimeters (as opposed to the crosshatching of infill) to be easily removable without damaging the part.


Question:
There is a 3D desktop printer RepRap which can print most of its own components.

Assuming each printed printer will print the next one and so on. Are there any limitation how many times this can be achieved?

For example somebody printed for me printer and I do the same for my friends and they do the same for theirs. Can this go forever (since 3D model stays the same), or there are any serious side-effects/disadvantages of doing that continuously?

Answer:
As long as you maintain each printer and keep a proper calibration, go for it, this is what they were designed to do, I've even made replacement parts for myself.
Unfortunately the
RepRap project just shut down on 1/15/16
due to their lack of sales.
I have a reprap that came from a reprap, and has made another reprap.
Just make sure that when printing out the pieces for the next you are properly calibrated, otherwise the next machine might be built crooked;
Your only limitations will be the electronics pieces and the small amount of hardware that you will need to buy.


Question:
I have a few kg of 3 mm filament when I only have use for 1.75 mm.

How can I make 1.75 mm from 3 mm filament?

Answer:
The best option is to find somebody in need of 3 mm filament and trade them for it (either in exchange for 1.75 mm filament or in exchange for legal tender with which to buy said filament).
The next best option would be to cut it into small pieces, and feed those into a filament extrusion system such as the
filastruder
.


Question:
I am printing a print using PLA on a Prusa i3 printer and an MK8 extruder, at 210 degrees celsius, 60 mm/sec, sliced with slic3r. The print consists of a base, with 4 tower-like projections that then join with a near-vertical overhang slope that isn't posing a problem for my printer.

However, even before the overhang begins, I am getting large amounts of strings as the extruder head jumps between the four towers in the print, leading to a "spiderweb" effect between them. How can I deal with these strings, and are they a warning that there might be something amiss with my printer, or possible other failures in other parts of the print?

Answer:
Stringing is often a result of too-high a temperature, or insufficient retraction. When there is highly liquid filament in the nozzle tip, it can adhere to the remainder of the print while dripping as the nozzle moves, leading to a thin string of the filament forming. As further travel moves are performed in each layer, this turns to a web.
The high temperature causes filament to be very liquid, causing it to move downward in the nozzle chamber easily, as opposed to having to be extruded forcefully due to viscosity. The temperature setpoint of 210 was high enough to cause this to happen.
A second possible cause, insufficient retraction, can also be blamed for this issue. Retraction is a process in which the extruder reverses its movement to pull filament back up the hotend, preventing it from dripping at the tip, and forming a string. Most slicers will allow specifying a numeric value in millimeters of filament to be retracted. Remember that printers with Bowden tubes between nozzle/hotend and extruder motor will require increased retraction and priming (extrusion when starting to print after a retract-and-move). Note that too much retraction can cause other problems, such as insufficient plastic in the hotend chamber at the start of the next printing move, which can cause gaps and other issues.


Question:
I want to print a model of an animal cell.

What I have so far: I managed to use different colors to print out the different parts of the cell.

My question is: what is the best way to connect plastic 3d printed parts?

Glue? Melted plastic? I need it to have a strong connection and not very visible when used well, and preferable dries fast.

Answer:
For ABS print, I recommend
acetone
. It is not a glue, but it will dissolve the plastic a bit and if you apply it to both connecting parts and push them together, they will stay connected after the acetone dries. However, it does not dry very fast and you have to be careful not to destroy the object.
For PLA I usually use regular super glue (
Cyanoacrylate
).


Question:
Is it possible to re-use ABS or PLA filament material from printed parts?

If so, what is the techniques to reform it?

Answer:
There are a few options.
Machines are available which grind the used plastic into fine pieces, melt it down, and extrude it as filament to be reused.
Filabot
is perhaps the most well known.
Depending on where you live the local recycling programs may accept PLA or ABS. They will then shred it and melt it down for reuse.
PLA is bio-degradable so you can put it in the compost.
I put scrap ABS in acetone which results in a slurry which can be used as a glue to attach ABS parts, fix cracks, and hold parts to the bed.


Question:
I made a test print for a small gear (~ 1.5 inches in diameter) a few months ago, with a hole through the center. On the first try, the filament (ABS) fused to the print bed, meaning that I had to spend ten minutes scraping off material to loosen it. One solution to this is to use painter's tape spread across the print bed.

This yielded a good print during the next run. The problem with this method was that some of the tape subsequently fused to the backside of the gear; it was so tight that I had to discard the prototype. Multiple varieties of tape made no difference.

Is there a way to continue using this tape without having it fuse to the filament?

Answer:
This can highly depend on the slicer you are using. Some software such as Makerware and Slic3r allow you to adjust the settings for the first raft/part layers. I might suggest adjusting this "Z0" point to about 1/4-1/2 of your layer height. Essentially the first layer (or two) will not adhere as well.
This is just one suggestion of many solutions. Here are some other variables I could think of off-hand:
Type of build plate tape (ie masking, painters, kapton, etc.)
Type of material. I've noticed that PLA is very stubborn if you let the part completely cool after printing and that it's much easier to remove the part from the build plate/raft right after it's complete.
Type of build plate. Are you applying too much heat (if you have a heated bp) for the material such as PLA?
Try lowering your layer height. This will ensure that each strand does not have too much surface area and therefore less chance that it will create a vacuum affect with the build plate. This can, however, result in a worse surface finish.


Question: Acetone can be used to smooth ABS prints.  What safety precautions should be taken during its use?

Answer:
There are a few main safety precautions you should consider.
Make sure the area is well-ventilated.
Acetone is flammable. A buildup of acetone gas could quickly get concentrated, meaning that a single spark could lead to disaster. Using a fan is good; angle it towards an open window. This is also to prevent exposure to acetone because of its toxicity.
Be prepared to fight a fire.
Should vapor ignite, you may need to fight the fire. If it is large enough, then you should clearly evacuate the area. If it appears to be small, use dry chemical powder to snuff out the fire. Alcohol foam, water spray, and/or fog may be used on slightly larger fires. Acetone is not likely to cause a large inferno to rip through the building. But there's always the chance of a small fire. Be careful.
Create a vapor chamber.
This is another way to stop a potential fire from spreading. It can also reduce contamination.
Wear gloves.
This can minimize any potential transfer toxic effects. However, skin exposure is unlikely to cause major issues.
Acetone is toxic, as I mentioned before, but it is not highly toxic. Exposure via
the eyes and nose/mouth
is the main risk. Skin effects may occur (e.g. mild irritation), but they are minor and generally arise only after long-term exposure (hence the recommendation of gloves in some cases).
Acetone exposure is only a serious problem when a person is repeatedly exposed to levels
greater than 1,000 ppm
(severe effects only arise at much higher levels). It seems unlikely, given a proper ventilation system, that this will be an issue
In addition to all this, basic safety precautions such as wearing a ventilator mask and goggles should definitely be taken. When working with any such chemicals with the potential for bodily harm, these should absolutely be used.


Question:
I would like to print multiple parts continuously (non-interactively), so
I can leave the printer alone for a longer time. So after finish, parts could be moved somehow out from the printing area, so the next can start.

Are there any methods of achieving that with standard desktop printers without having to use multiple printers?

Answer:
The only thing I can think of off hand is an old mod for the early MakerBot machines. It first was released for the Thing-O'-Matic I believe, but is compatible with Replicator 1 machines (and its knock-offs). Here's the
Thingiverse page
, but look up Automatic Build Plate.
Essentially, you can use the Replicator G slicing program and there is a setting for "ABP" or Automatic Build Plate. This will basically tell the ABP to run its routine after the controller receives the response that the printing program is done and roll the finished part off the edge of the build plate, then start the same program over again.
Drawbacks:
I don't think it's easily compatible with newer machines/slicers. But, it's open source
Pretty sure you have to use Replicator G, which is outdated now and may make your machine sound like it's going to fall apart (I know from experience)
Going off of @Pete's answer about solenoids. It reminded me that someone integrated a
solenoid "ejector"
(aka Boxing Glove) for their machine.
Update (06/08/2016):
Forgot to mention that if you choose to create your own "Boxing Glove" or conveyor belt, some software such as Octo-Pi and Repetier-Host allow plugins. So, you could interface with your hardware via customized code and integrate the functionality directly into the slicing application for the full closed loop operation.


Question: For standard ABS and PLA filament, most distributors recommend storing the filament in an airtight bag.  Does not doing this actually make print quality worse?  I have left mine in the open for a year and have had no noticeable problems.

Answer:
Humidity may be the problem.
Humidity tends to degrade filament, making it weaker.
If you leave a coil of filament out, over time it will be exposed to humidity. I have yet to hear of this happening over a short period of time - the real threat comes if you leave it out for weeks or months - but it can happen nonetheless.
Contamination with other materials is possible but unlikely. The odds of some sort of impurity developing from nearby particles is extremely low unless the filament is actively exposed to some other material.
In most cases, though, things should be just fine.


Question:
I want to fabricate a sample holder and shadow masks to use in vacuum chambers. The type of printing material is not important to me PLA/ABS/PC-ABS/nylon).

I'm worried that 3d printed objects (FDM) would degas under high vacuum. Is that an actual concern?

Answer:
Almost all of the FDM materials outgas even at normal atmospheric pressure, and, in fact, most plastics outgas.  Further, FDM and many other printing processes do not guarantee no internal voids - meaning that putting a 3D printed object into a vacuum may result in breakage, cracking, and possible explosion hazards.
For this reason I would focus only on SLA, as the model is printed within the liquid resin pool and should have a reduced possibility of internal voids.
Finding a resin that has a low out-gas rate after curing, though, is still going to be difficult.
For this to be answered more completely, you need to specify your tolerable outgassing rate, and the processes used inside the vacuum chamber.  For instance the answer would be completely different if you are discussing an electron microscope vs a sputtering chamber. As a start you might consider companies that specialize in
engineered materials intended for vacuum use
. They may be able to provide guidance as to which of their materials might be 3D printed and usable in your setup.


Question: Assuming you have a high quality printer with a fast processor, will you see a noticeable improvement by upgrading from 16X/32X microstepping drivers to 64X/128X microstepping drivers? (e.g. smoother surface finish).  In what ways do they perform differently from the more common 16X or 32X stepper drivers.  I'm thinking the RAPS128, Silencioso, and Trinamic drivers vs the DRV8825, A4988 and A4988.

Answer:
Prints benefit from higher microstepping in two ways:
Noise level
Using microstepping reduces noise from your printer's operation.
Print quality
Using higher resolution microstepping does not increase the physical accuracy of your prints meaningfully, but it can reduce surface artifacts such as
moire
.


Question:
What materials which are commonly used in 3D printing, are food-safe?

Are there any certifications/grading process for such materials, which can help me with my cross-checking and selection?

I have been using an FDM printer.

Answer:
Food safety is a property of both the process and the material. You can't stick food-safe material in a printer that has previously been used to print something food-dangerous and expect the result to be food safe.
The only way to know if a given material is food-safe is to ask your supplier, but a lot depends on how you then process it. For instance, FDM printers often have brass nozzles, which contain lead. To print food-safe materials, you need to use a stainless steel nozzle.
Food safe materials can be identified by mean of
an universal symbol
.
Moreover, to ensure food-safety of a 3D printed model you may need to further process it (for instance, by vapor smoothing or coating with a food-safe lacquer). Some claims circulate on the internet that 3D printed models may have surface porosity in which bacteria can grow, but I've not been able to find a reliable source for this claim. Still, you need to be cautious.


Question:
Suddenly, my printer has started producing prints that have a very pronounced layering. Normally, the alignment between layers is very good, and the prints look very smooth. Suddenly, the prints have become much worse and the layers are misaligned with respect to each other.

The part on the left is my "normal" quality, while the part on the right show the deterioration. Here is another picture (in which the good part is on the right):

The parts are both printed with 0.1mm layer height, and identical slicer settings/filament. I am printing on a custom-built FDM printer; the mechanism is roughly similar to that of an Ultimaker.

Answer:
There are many factors, here are a few things to check:
I'd first suspect filament feeding.  This type of ridging can be caused by a filament coil that is binding occasionally, or a filament that doesn't have an even diameter or volume per length.  Binding within the filament feeder and feeder tubes can also be a cause. Bubbles in the filament, or sometimes a mismatch between the filament ideal temperature and the head temperature could create results like this, but it probably wouldn't vary so much between the layers.
Next I'd look at the print head.  If it has blockages, or poor temperature control this could result.
Lastly, I'd check the mechanisms - disconnect the motors and see if all the carriages slide smoothly without any binding, particularly the Z axis.  It doesn't look like you're missing steps, but binding here may result in greater backlash, which could result in similar ridges. Make sure any belts and gears are tight.


Question:
I am working on a robotics project and need to print some gears. These will probably by under a LOT of pressure. Which material/filament should I choose so that the gears don't wear off easily?

PS: Newbie here...

EDIT:
According to my instuctor, it has to be some sort of plastic (not metal).
It also has to be lightweight...

Answer:
So, as you say you want to materials for printing robotics parts. And as you have not given any budget constraint, I would give you a list of materials which would help you achieve the task, and you can choose amongst them accordingly.
Plastics: Basically used for building prototypes. Nylon Polyamide should be a choice for you.
Polyamide 3D printing is achieved through SLS 3D printing. It offers
  strong and flexible prints. The upside of this material is that the
  printing technology requires minimum preparation of the 3D file before
  printing. There is no need for support. And it also offers the
  possibility to create intricate shapes and moving part in just one go.
  After the print the polyamide can be polished and dyed.
Metals: Metals like Brass, Alumunium and Steel should be a good choice.
But, if I were to achieve your task, I would select carbon fiber. some details about it:
Carbon fiber consists of 90% carbon atoms, each fiber is 10 times
  thinner than a human hair. Carbon is especially prized for its lack of
  combustibility and infusability but also by its incredible strength
  (stronger than steel) and ability to create flexible structure, light
  weight and corrosion resistance. Its melting temperature is 1500, this
  heat there are only carbon.


Question:
I am currently working on parts for a custom prosthesis.

My main concern at the moment is to find biocompatible materials that can be 3D printed from a UP or a Reprap.
The piece would need to be in contact with the skin for extended periods of time, probably around 17 hours a day on average.

The main concerns I have are:

Skin reactions caused by prolonged contact

Skin reactions and bruising caused by friction

Degradation of the materials due to prolonged exposure to skin secretions and sweat

Risks of toxicity in the compounds generated by the aforementioned material degradation

Which materials can you recommend?

Any extensive data (from testing) would be greatly appreciated.

Answer:
There are printers designed for medical use, and the manufacturers supply them with varying levels of
certification and testing
, however I've not seen a filament manufacturer certify their material as bio-compatible separate from the printer. The printing process changes the material slightly in the best case (and significantly with poor temperature control or badly set parameters), so even if bio-compatible filament were found, the resulting product might not achieve the same level of bio-compatibility.
If your intent is to use hobbyist level machine for medical purposes, you might simply want to use an interface, such as a sock or a molded/cast polymer that you know to be bio-compatible between the printed part and the skin.


Question:
I would like to print edible cookies or ornamentation for a cake.

Is printing with edible materials achievable by standard thermoplastic-like 3D desktop printer? Or you need to buy a special printer to do that?

Answer:
You can, but that doesn't mean it's very easy.
You don't have to buy a special printer, but you need a special extruder (such as
http://www.structur3d.io/
). Most of these systems can print anything with the consistency of Nutella. However, many parts of the printer may not be food safe.
Another option (if you simply want 2d designs) is something like the
PancakeBot
. It can probably also "print" with anything that has the same consistency of pancake batter.


Question:
I would like to print fancy plastic cutlery sets or plastic glasses.

Is it safe to do it? Or bad for your health, if so, why?

Answer:
Having performed a quick search through all the resources at the FDA Food Contact Substance resource, I cannot find PLA in any list except an occasional notification that a specific manufacturer has obtained approval for use in specific circumstances, with the notice that such notifications are only valid for that manufacturer and cannot be used to validate another use of a substance.
There are companies that have received approval for their specific formulation and use of PLA as a food contact substance.  You may wish to discuss this further with your material supplier to find out if they have approved PLA product available.
Without specific product approval, though, PLA is not on the lists of generally recognized as safe, nor approved for food contact use.
Regulations in other countries may differ, so you may want to search the EU directives, for instance, to find out their opinion on PLA as an FCS.


Question:
I'm interested in designing & 3D printing as a hobby (e.g. printing chess sets, small toys for family etc.)

Conducting a Google search has brought up a range of small, cheap printers, but beyond that I don't know how to differentiate them.

E.g. selling points include:

"liquid light-sensitive resin"

"partially assembled" with "very few parts and minor configuration"

"Wi-Fi enabled"

My question is, which features are going to benefit a small-scale, new enthusiast to 3D printing?

PS. The software I intend to use is Windows 10 3D design

PPS. I'm not a graphic designer by any means, just a new enthusiast.

Answer:
Here are few things to consider from my point of view
Printing technology
The first thing that you need to take into account is printing technology. The most common[citation needed] right now is Fused Filament Fabrication. "Liquid light-sensitive resin" is being used in Stereolitography and Digital Light Processing - the SLA printers I found are less common and more expensive than FFF ones.
Price
Need to decide on budget. You can buy printer for 60k USD and 400 USD. Quality is somehow linked to price but that's not a rule. You can buy a shitty printer for a lot of money.
Printing area
Bigger allows you to print bigger things. You need to ask yourself how big things you really want to print. Remember that 3d printing is quite slow process - how often you will want to print big things that will take 60hrs+ to finish?
Printing materials
What kind of materials you want to print with? Some materials will need higher temperatures so check the max hot-end temperature, some will require heated bed.
Assembled or DIY kit
You can usually get kits for self-assembly cheaper than Ready-To-Print machines. However, it will require additional skills (i.e. soldering), tools and time to assemble. I am not sure if I would buy DIY kit for commercial use, but as an enthusiast I immensely enjoyed putting my Rostock Max together.
Reviews and reputation
It is generally safe to buy printer that already has some users. Beware of new magical Kickstarter printers which will "change the 3d printing forever".
Reddit /r/3dprinting suggests that your new printer should meet 3 criteria:
Printer passes the youtube test - has lots of youtube evidence that this particular printer is working.
Printer is out of the pre-order phase. This means that all pre-orders have been delivered.
Printer has a reputation of working well among current users.
I found it to be a very good set of rules.
Upgrade capabilities
That's very user-dependent, but this point is very important to me. I want to be able to change and improve certain parts of my printer. Check if you can switch the extruder, replace the hot-end etc.
Support
I think one of the most important points. See if you can find a forum for your printer and how active community is. It will be immensely helpful if something goes wrong (and it will).
Also, company support is very important. What will happen if you need a replacement part or your printer will stop working altogether?
This list is definitely not complete.
There are many more things that might be taken into account like configuration (delta or XY), multiple extruders, closed cases etc.


Question:
I'm reading about wiring up the electronic components to my Prusa i3 using an Arduino Mega 2650 and Ramps 1.4.

I have step sticks, a heated bed, and a Switching Power Supply 12v Dc 30a 360w  (more details on that later when I can add which ones to the post).

I've heard that if you wire it wrong and plug it in, you can do anything from starting a fire to burning out your boards.

What are some tips of things to check before plugging it in? Are there any common mistakes that I can avoid?

Answer:
I'd say polarity and voltage are the biggest things -- about all you can do is double- and triple-check everything; then check again....
Be very careful about where you feed in 12V power (mainly for heaters and fans), vs. 5v (for the Arduino).
In many cases I found it unclear which way +/- went going
out
from the board (the
inputs
on my boards were at least marked clearly!). I found that if I plug in a limit switch connector backwards, that connects 5v straight to ground, which will probably make your power supply cut out (assuming it's properly protected -- otherwise it could potentially catch fire). Stepper motors, on the other hand, just run the wrong direction if you plug them onto RAMPS backwards (good design!).
Another thing to watch for only comes up if you're powering the Arduino via USB (I do that a lot, since I'm plugged in anyway to send files and such). A short can try to draw too much power from USB. In that case my Mac shuts down USB and gives a message; I don't know what would happen with other hardware.
I have heard that plugging a stepper-driver board onto RAMPS backwards is likely to fry a board, and that plugging or unplugging a stepper motor while powered is also risky. But I haven't messed those up yet, so I don't now for sure. :)
I may be overly cautious, but I never leave the power supply plugged in when I'm not around.
Best wishes!
Steve


Question:
Printer: FDM printer  (FDM == Fusion Deposition Modelling).

Raw Material: Thermoplastics.

How do I do multicolor printing? What changes should I make to the printing process/to the raw material used?

(Answer in the context of printing a basic 3X3 Rubix cube)

Bonus: What are the best practises while doing multi-colour printing?   (<-- This is opinion based and/or broad, so pl add an answer to this point as an extra to your answers if you can. It would greatly help people getting started/practising with multi-colour printing)

Answer:
There are a few different approaches I've seen which you could look into.
The easiest and most common is multiple extruders, each with a different color of thermoplastic. Tools like Pronterface and Slic3r have built-in support for multiple extruders. With multiple extruders you can get one color per extruder; there's no clear way to mix colors and get a color between the input materials' colors.
Another, more complicated approach is to use a single extruder with three inputs, like
this one
, where thermoplastic from the three inputs can be mixed in varying amounts to get color gradients between the input colors. With red, yellow, and blue filament, you could get a rainbow of colors...albeit without any control over value (white to black) or saturation (bright vs dull color).


Question:
A fellow maker has tried printing a 3D model in clear PLA (<5% infill, 1 or 2 perimeters), burying it most of the way into casting sand, and then pouring molten aluminum. This melts and burns the PLA, and the aluminum takes the space that the printed model used to take.

There's plenty of room for improvement in his process, but I'm asking about what he can do in terms of the 3D printing process to make his prints more casting-friendly.

What print settings are (generally) best for use in this sort of casting?

What materials, if any, would work better than unpigmented PLA? (Must be a material that a typical thermoplastic FDM printer can handle.)

Any other tips or considerations?

Answer:
I believe casting typically uses a wax for the positive when using casting sand. So, I would suggest using
wax filament
in your 3D printer.
I would try to shy away from hard polymers like PLA/ABS/Nylon (all typical 3D printing filaments) if the goal is to "melt it away" because a certain amount of the plastic material will either bind itself with the metal or large chunks of plastic will cause inclusions in your part. Both of these side effects will potentially degrade the quality/strength of your part.
I haven't personally used wax filament, so I can't tell you what the correct setting are. However, you can get most of the necessary information from whichever supplier you go through. I might suggest running your machine slower when using a low-melting filament such as wax or PVA (water soluble).


Question:
How do I determine how much an individual print costs?

I'd like an answer including support material, failed prints, and (ideally) wear and tear / printer maintenance costs.

To clarify, I'm not asking how to predict the cost before printing, but rather how to calculate the actual cost after printing. Though predicting the cost beforehand is useful as well.

Answer:
For
FDM
printing:
Both Cura and Makerbot Desktop (and perhaps others I'm not as familiar with) will give you a preview of both the length and weight of your print, including supports/rafts. Once the print is done you can weigh it on a kitchen scale.
PLA Filament currently runs about \$23/kg on Amazon, which works out to \$0.023/g. Multiplication can then give you a good estimate of materials costs for a print.
Only experience with your specific printer will give you an idea of how often you're going to hit a failed print, and how often you're going to need to replace parts. For wear and tear you could try using a depreciation model of 2-3 years, but that's only an estimate.


Question:
When the print head changes direction, the printer must accelerate and decelerate the print head. When calibrated correctly, the printer is able to do this quickly and without causing the printer to shake too much, without drastically slowing down the print process.

If I set it too high, my printer shakes violently, especially during infill. If I set it too low, print times are doubled or tripled.

What process can I follow to determine (or how can I calculate) the fastest acceleration value my printer can use without causing problems in my print?

I'd prefer a process I can follow over a formula I can plug values into, especially if the formula includes magic numbers.

Answer:
A tool that you might find useful for experimenting with acceleration is
RepRap Centrals Acceleration Calculator
(at the bottom).
By setting an
acceleration
,
length of travel
and
target speed
, you can see:
The theoretical speed that can be achieved during the travel with your set acceleration (yellow line).
The distance required to reach your target speed, and for how long it will hold that speed before slowing down (blue line).
For instance, setting
```
acceleration = 3000, length = 30 and speed = 150
```
means it will travel 4 mm before reaching its desired speed of 150 mm/s, while that same acceleration theoretically could give a speed of 300 mm/s for the given distance:
Calculating speed, acceleration and jerk:
In many cases your printer will have some limitation in maximum speed or settings given by your provider that can be used as a starting point. If not, trial and error is the most straightforward way of doing it.
I would separate speed calibration into three task:
First find the
maximum speed
your printer can tolerate. One way of doing this is to print an object with long travel distances, and vary the maximum travel speed.
Using the calculator above, increase the
acceleration
for various traveling distances until you get suitably smooth acceleration curves for your desired speed for medium to long traveling distances.
Adjust your
jerk
setting to allow for quick speedup on short traveling distances. Jerk speed is the speed that the printer will immediately jump to before taking acceleration into account. With a jerk of 20mm/s, the printer will make an immediate jump from 0 to 20 mm/s, and thereafter speed up to the desired speed by following the acceleration profile.
As a rule of thumb, it might be smart to then set the actual speed, jerk and acceleration approximately 20% below the the maximum found as a safeguard when printing.
Also, bear in mind that
the strength of stepper motors lowers for higher speeds
, so that the nozzle will not hold its path very well if obstructed. If this becomes a problem, consider lowering the speed.


Question:
Using a thermoplastic MDF printer with a 0.4mm extruder nozzle, I frequently have trouble with the nozzle getting clogged.

I am not sure what's causing the clog, but my guesses are dust and/or burnt filament (from leaving the hot end on without extruding).

What can I do to prevent, or at least minimize, the extruder nozzle getting clogged?

Bonus question: What other common causes of clogs are there? (ie what should I watch out for besides dust and leaving the hot end on?)

Answer:
Lubricating the filament is the most common solution I've heard of to stop filament jams and clogs. Lubricating makes for a smoother ride through the print head. While you're at it, make sure that the filament is clean. The best way to stop jams from dust is to get rid of the dust in the first place.
Some people recommend
canola oil
, which I've heard works reasonably well for both ABS and PLA (though especially for PLA). You can even
3D-print dust filters/lubricators
, if you think this could be a serious issue.
I personally try to clean the print head regularly, after every couple prints or even after each print, if I have time. Something sharp, like tweezers, can pick off bits of filament near the tip of the nozzle. I haven't tried other utensils yet, but there are certainly other tools that would work. I've also heard of people regulating temperature with a fan, in order to prevent partially melted bits of filament clogging up the inside of the nozzle, but I don't know if that's effective.
In some cases, the problem could even be as mundane as a support issue. I once set up a spool of filament, only to have a jam when the support for the spool failed, leaving the line of filament tugging at the nozzle and clogging it. Taking steps to prevent this from happening can be simply and effective. Whatever the cause, preventative measures are always my choice.


Question:
My thermoplastic FDM printer has a heated bed and uses glass as the printing surface. Sometimes the glass will chip or break entirely when I'm removing my print. This happens most often when the print has a large area in contact with the glass.

What can I do to keep this from happening?

Answer:
Some things I've tried that have helped:
Lay down a layer of masking tape. Most people who do this use blue painter's tape. The plastic should stick nicely during printing, yet release reasonably easily when you remove the print from the heated bed.
Lay down a later of Kapton tape. The principle is the same as masking tape, but Kapton tape has a smooth surface and is more durable than masking tape. The down side is Kapton tape is far more expensive, and applying it correctly is a LOT more work, since you have to use water and you have to keep bubbles from getting underneath it.
Put some ABS scraps into a bottle of Acetone, and allow the acetone to break down the ABS til you have a slurry. Spread this slurry as evenly as possible across the build plate, and allow the acetone to evaporate away. This leaves a thin film of ABS on the plate, and will release much better than if you print directly onto the build plate. I recommend using clear ABS if you can, since some of it will stick to your print and clear will be the least visible. You'll need to re-apply it regularly, since it will come off with your print where it touches the build plate.
WARNING
: Use proper ventilation and avoid contact with acetone. That stuff's not good for you. Also it's flammable, so keep a fire extinguisher nearby.
I prefer the ABS/acetone slurry method, but it requires good ventilation and a handy fire extinguisher. Also note that you don't have to print in ABS to use an ABS/acetone slurry; I print primarily in PLA and it makes no difference.
I've also heard of others using a glue stick or some other surface treatments that allow for good adhesion during printing while still allowing for easy removal.


Question:
For a science project, I'm 3D-printing some custom pipes and tubes to regulate the flow of gas (a combination of ethyl alcohol and water vapor) through an apparatus. They need to be pretty small, as the entire experiment is designed on a small scale. I'd also like the use a little filament as possible.

How thin can I make the walls of these pipes and tubes before either they collapse or gas leaks out? I know that's possibly an engineering issue, but I'd also need to take resolution into consideration. Ideally, the pipes would be about two centimeters in diameter, possibly a little larger or a little smaller in some parts. I'd most likely use ABS, but PLA is my backup in case there's some unforeseen reaction between the gas and the pipes.

The printer I'm using is an FDM printer, a version of the MakerBot Replicator.

Answer:
The thinnest wall your printer can print is determined by its nozzle size, and will be a little thicker than that nozzle size.
A great challenge when dealing with thin, hollow cylinders is that the cross-section has very little surface area and it can delaminate easily, especially if the tube is long.
You could try printing the tube with a very thick extrusion with, and using only a single perimeter. That would give better gas-tightness and layer adhesion than two, thinner perimeters, but it may turn out too fragile for your application. In that case, you'll need to print additional perimeters. Sticking to thicker extrusion widths would still be beneficial.
At a two centimeter diameter I'd say the single perimeter has a decent chance of working if you handle them gingerly.


Question:
I often switch my print material, i.e. ABS / PLA / Wood / Flex,

How can I best clean out my extruder between them to ensure I don't contaminate my next print?

Answer:
In most cases, removing the old filament from the printer, inserting the new filament in, and running the new filament through the printer for a short period of time will clean the nozzle.  The skirt of the print can also be a time during the actual print for the old filament to be flushed.  Assuming the skirt is long enough, all that needs to be done is the new filament inserted and the print started.
Assuming that extruding new filament does not fix the problem, there is a more serious problem such as a clogged extrusion head that needs to be fixed with other methods.


Question:
After multiple jams from bulging filaments on two spools I'm getting frustrated.  One, right before a job was done.

Is there something I can do to prevent these bulges in filaments from ruining jobs?

What can I do to prevent this from happening in the future before it's a disaster?

He's a picture of one I found using google.

Answer:
How to catch
and
fix these on the fly? That would be difficult..
But this is an issue you really should not have.
Could it be an issue with filament storage?
Or is it coming from the manufacturer with these bulges? If so, I would try contacting ( you may have gotten a bad batch? ), or finding a new retailer if this happens often.
I have gone through a lot of pounds of both ABS and PLA and never come across this.


Question:
I am operating a laser sintering machine, using polyamide 2200 powder (with a grain size of approximately 50 micrometers). During a print, a lot of powder goes unsintered and can theoretically be reused. However, using purely recycled powder degrades print quality to an unacceptable level.

Mixing a little used powder into a larger amount of fresh powder seems to work well though. What is the greatest ratio of used to fresh powder that still gives good results, and is there anything I can do (pre- postprocessing) to allow more powder to be reused?

Answer:
You'll find generally that mixing 40% new polyamide with 60% recycled polyamide will result in a reasonable finish and part. You will obviously want to use all new for parts requiring the best possible finish and mechanical properties, but this mixture will be very difficult to tell apart from a fully new mixture part:
http://www.paramountind.com/pdfs/eos_pa2200_mds.pdf
This is more detailed research showing how used powder changes and how that affects print quality here:
http://www.emeraldinsight.com/doi/abs/10.1108/13552540910960299
Searching for the research paper title may find a free source, but the linked resource does require a subscription or payment to that service.


Question: Usually it will either will rip the tape, or break the print somehow. Currently using ABS on a taped glass bed with a layer of hairspray for adhesion.

Answer:
I moved to a plain glass heated bed with a brush applied acetone and ABS mixture. Using an old emptied nail polish bottle with brush, I added some acetone and then threw in ABS pieces until it reached a brush-able consistency. I then brush it on the glass build plate where I believe the print will occur, and it works very well. On removal of the part the coating comes with it.
I just found previously that ABS would adhere to my kapton taped heated bed too strongly to use, and so while this involves a little work before each print, it's overall better than kapton for me.
I did experiment with sheet metal beds coated with kapton, but they curl during printing due to the ABS thermal stress, allowing my parts to be concave on the bottom side. Easy to remove from the plate, though, since it flexed. There may be a good middle ground material but I didn't experiment further.


Question:
Why do we have two standard filament sizes, 1.75 mm and 3 mm? Does it really make a difference when printing? Or is the 1.75 mm just for smaller printers?

In what situations should I be using 1.75 mm?

When should I be using 3 mm?

Answer:
There's no appreciable difference. Just use the filament that fits your particular printer.
If you don't yet have a printer, then I'd get one that uses 1.75 mm filament:
1.75 mm is increasingly becoming the "standard", thus being easier to get. Some filaments are not available as 3 mm.
1.75 mm filament allows for finer control, because feeding in 1 mm of filament corresponds to less plastic extruded.
1.75 mm filament requires less force to extrude. Compressing 1.75 mm down to 0.3 mm takes less force than doing the same to 3 mm filament.
However, the advantages are fairly minor. I don't see any reason to replace a functioning 3 mm extruder with a 1.75 mm one (yet).


Question:
As an extension from this question, is there any reason that you would not be able to use 1.75 mm filament in a printer that takes 3mm filament?  I know you would have to change the filament size in the slicing of prints but would there be any other problems?

Also, would using 1.75 mm filament be possible if the nozzle diameter was greater than 1.75 mm but less than 3 mm?

Answer:
It may work for a short time but you're going to fill the melt chamber quickly and possibly overflow to a point where the filament isn't constrained causing a messy jam.  All the molten plastic will likely flow backwards to a point where the diameter isn't 3mm any longer (probably next to your drive gear) but depending on the length it may just flow up, cool down and jam the extruder.
No, the filament would just pass through unheated and not do anything.


Question:
There must be a trick to doing a good job of applying Kapton tape on a printer bed plate…

We built a Bukobot and even with a great deal of care ended up with bubbles under the tape and occasional overlaps. I'd appreciate any pointers.

Answer:
There are several things you could try without spending much but even PLA will warp on an unheated bed.  I had a Legacy Kossel that I switched to an acrylic bed and had many issues with warping and prints pulling off the bed.
Some cheap things to try would be...
Adding a brim to the print.
Blue painters tape on the acrylic, remove the other material if doing this.
Place cheap piece of glass/mirror on bed and use hairspray/gluestick.
Use hairspray/gluestick directly on acrylic.  You must be careful here because first layer height is very critical to prevent damage to the acrylic from the plastic welding.  A layer of hairspray or glue should prevent it but dial in your height before printing.
If you aren't currently using a fan, you could try sealing the sides to prevent drafts.  I doubt this would change much since you are using PLA but it's an option.
If these are your designs, there are steps you can take to reduce warping as seen
here.
Also many other suggestions
here.


Question:
This article states that 3D printing has been accomplished in outer space, on the International Space Station.

I'm curious as to how this works differently from 3D printing on Earth. Are there any extra measures that needed to be taken to ensure that the filament would be correctly extruded onto the print bed, or during other steps?

Answer:
Most likely, the 3D-printers used on ISS does not incorporate some fundamental difference that allow them to print in zero gravity.
Some people over at
3Dprint.com
raised a very similar question, and figured that when turning their 3D-printer upside down and on it's side:
there’s not really much difference at all. It’s quite interesting to see how the orientation has little effect on the quality.
One of the early 3D-printer models - the
Bukito
printer - demonstrated that their printer was so portable it even could print on the move, and
upside down
.
In other words, some consumer 3D printers already print upside down, and so they would probably print in zero gravity as well!
(That's the short story anyway. Have a look at Ryan's post, who gives a great description of the more intricate parts of space printing!)


Question:
Are there any techniques for getting a smooth finish for parts printed with co-polyester (PET) filaments? More specifically, I am looking for an alternative that does not roughen the look of the part - such as using sandpaper - but rather works like acetone baths for ABS.

In particular, I want to treat ColorFabb's XT filament made from the Eastman Amphora™ 3D polymer (datasheet). This is also the polymer is also used in:

ColorFabb nGen and XT

Taulman3D n-vent

TripTech Athiri 1800

3DXTech 3DXNano

Answer:
I've found a
chart
which covers several plastics and solvents and only two of them (
Chloromethane
and
Chloroform
) are rated "D" which includes dissolving the material and both seem to be quite nasty and I doubt you will be able to purchase them without being placed on several lists.
Is it possible that something like
XTC-3D
from Smooth-On would work for you?
Also some more information on dissolving PET
here
, several sources also mention PET is affected by Hydrogen Peroxide but they do not mention to what degree the plastic is affected.


Question:
Common 3D printers (read "cheap") may be used to print masks for PCBs (printed-circuit boards) which use PTH (through-hole) components.

But can they be used to print PCBs which use SMD components? I'd like to make boards at least for Arduino-like SMD chips.

Answer:
In theory, I imagine you can, but there are some practical considerations that might need some thought:
If you have a desktop printer with multiple extruders, you could probably print with both one
conductive
and one
structural
filament, and thereby build circuits in 3D.
One concern would be the low melting points of most 3D printed filaments, since one would have to limit the heat generated by the mounted components and connections so that the structure of the "board" would not be melted.
Mounting components to the board would also differ from a normal PCB, since you would have to connect the components with the conductive filament without melting the structure of the board. In other words, you probably would have to use conductive filament as "solder", and melt components into place.
Whether you could use typical tools used for mounting SMD components with conductive filament as solder is beyond my knowledge.


Question:
When designing parts that should either fit with external objects or other printed parts, what measures can one take to ensure that the dimensions of the final print are accurate and fit the other object?

To my knowledge, you at least have two options to account for printer inaccuracy and shrinkage:

Adjust the space around joints in your CAD model

Adjust dimensional offsets in your slicer software

Are there any good workflows one can use to design and print 3D-models accurately without resorting to trial and error?

Answer:
I think the best way to go about this would be to calibrate your printer and slicer as best you can.  One of my pet peeves is when people upload STLs that have been adjusted to fit their printer/material.  There are many suppliers of material that vary in quality as well as many materials and different printers that the tolerances shouldn't be built into the part because in the end it usually just makes it harder for others attempting to print the model.
If you aren't sharing models then all I can say is you are still better off to calibrate your printer and tune your slicer to your material.  You'll have more luck with models from other people and have an easier time designing your own.
If you still have trouble then modifying the model is probably the last option.  I don't know of any CAD programs that can work with problems 3D printers have so experience is going to be your only help.  I know in Inventor you can go around and Thicken/Offset individual surfaces of the model to compensate or if you had a percentage for your shrinkage you could get creative with formulas in the sketches.


Question:
I upgraded to a dual Mk9 extruder, and quickly discovered how critical it is to get the ends of both nozzles exactly level with each other -- that is, equally distant from the build plate at all times. Otherwise the lower one will crash against the plastic just extruded by the higher one.

So, what's a good procedure for getting the nozzles accurately level? About all I've figure out is to move the heads down close to Z=0, and then run X and Y back and forth and eyeball and adjust; then move even closer to Z=0 and repeat. Is there a better / more efficient way?

Answer:
Make sure that the
bed is level
. As the saying goes, a level bed is next to godliness or something like that. Pay extra attention to the direction the nozzles are offset by (if one nozzle is offset on the X-axis, pay extra attention to the bed leveling along the X-axis).
This can be done with just one nozzle and a business card or piece of paper
.
Use a
bubble level
to get the nozzles about right. Move your z-axis up a bit and put a bubble level against the nozzles. Adjust as necessary so it's exactly level. The nozzles should be level enough that the bubble stays in the middle.
Fine-tune it with a
business card
. When you home the z- axis, you should be able to just fit a business card under both nozzles with a moderate amount of resistance. Don't force the card. If sliding the business card under produces a different amount of resistance for one nozzle than for another, adjust the nozzle a
tiny
amount. You can also use an index card or playing card.
Once it passes the card test, try a test print. If it doesn't work, make sure your bed is level, your nozzle offset is correct in the slicing software, and try calibrating with an index card again. If the nozzles become way off, try the bubble level again.
As for physically adjusting the level, another answer suggests shims made from aluminum foil, which work well. Personally, my extruder was off-level by almost exactly 1mm, so a pair of washers worked nicely for that.
Happy printing!
Leveling with a bubble:


Question:
I just received this printer and while it seems to talk to Makerbot Desktop software I'm not sure if I should be trying to update the firmware.

The printer comes with firmware v7.2 and while Makerbot Desktop offers an upgrade to v7.5 I'm not sure if it's a good idea with this non-Makerbot branded printer.

I've also seen information on upgrading this printer to Sailfish v7.5, is this the same thing as Makerbot firmware v7.5?

Answer:
The Monoprice Architect is is a bare-bones FlashForge Creator that has been re-badged for Monoprice. The Creator line is a very popular set of printers, so there is lots of good advice out there. The FlashForge Google Group is a good community to join:
https://groups.google.com/forum/#!forum/flashforge
The entire FF Creator line, in turn, is cloned from the original Makerbot Replicator 1. So you can use Makerbot slicing profiles for the Replicator 1. Just keep in mind that Makerbot does not generally test new software revs with their older printers, and DEFINITELY does not test new software revs with competitor knock-offs. Sometimes they appear to break functionality for non-Makerbot machines on purpose. So recent versions of Makerbot Desktop may not "play nice" with your FlashForge.
The most recent "known good" free slicer you should use with this printer is Makerware 2.4.x. You can find links by searching the FF Google Group.
On that note, you may have received instructions to use ReplicatorG with your printer. But RepG is abandonware: development stopped years ago. It should only be used for firmware updates, not as a slicer. You should also only use the most recent version posted on the Sailfish page on Thingiverse:
http://www.thingiverse.com/thing:32084
Using older versions of RepG with newer firmware revs will corrupt your EEPROM! Only use the version downloaded from the link above.
The firmware that comes with the printer is FlashForge's slightly-customized build of either Sailfish or Makerbot's Replicator 1/2/2x firmware. But here's the trick: Makerbot's Rep1/2/2x firmware is just an old, out-of-date, slightly customized version of Sailfish. Makerbot stopped keeping up with bug-fixes and feature additions a long time ago.
Everything is Sailfish:
just different versions. You should use the most recent official release version listed at:
http://www.sailfishfirmware.com/
Follow the instructions in the Sailfish manual from the link above, and RepG will automatically pull the right builds from the official mirror and populate a list of printer options to choose. The trick here is which build to download. As of 1-21-16, there is not an official Monoprice Architect build yet. Which would mean editing a machine xml profile to avoid the firmware throwing warnings. I STRONGLY recommend getting used to the printer using factory firmware before trying to fight with custom machine profiles... But here is the basic process to pick a Sailfish firmware build when you're ready:
First: which Atmega processor version do you have? The large chip in the middle of the control board will either say 1280 or 2560. You need to know which version you have. Bad things happen if you load the wrong version.
Second: What is the tooth count on the X and Y drivetrain pulleys? To my knowledge, FF always uses 17-tooth pulleys, which matches the Replicator 1 and FF Creator profiles. The Rep2 and 2x use 18t pulleys, so only use those builds if you have those pulleys. People often mess this up and their prints end up with dimensions ~5% off in X and Y.
Third: The Architect has one extruder and no heatbed, so firmware builds that expect those to be connected (Rep 1 Dual, Creator, etc) will throw errors if loaded. You can fix this from the LCD screen or RepG, but that's a whole separate question. Do some printing and learn about the printer before attempting any firmware update so you'll know what to do if you pick a build with the wrong parts.
Fourth: This one is just for the sake of completeness. Some FF models were shipped with off-spec heatbeds that require special firmware builds to prevent drawing too much current and overheating / overloading the power supply. The Architect doesn't have that, but firmware builds for those printer models (eg I believe the FF Creator 2560) will under-power regular heatbeds. This is just something you need to know with the Architect if you decide to install a heatbed later. But it's a really critical safety warning for people with those off-spec heatbeds.
If this all seems complicated, that's because FlashForge (and in turn Monoprice) relies heavily on the open source Sailfish project to maintain the software ecosystem behind this line of printers. FlashForge has some internal builds that they use for flashing new bots, but these are not kept particularly up-to-date. Nor does FlashForge release the source files, so it's quite opaque where exactly the stock firmware differs from mainstream Sailfish. In the long run, you should install mainline Sailfish. But it's ok to stick with the factory firmware until you get used to the printer.
To summarize: Because there is not an existing Sailfish build, you're going to need to do some investigating and some experimenting to figure out which build will work. Don't try that until you're familiar with the printer. Post on the FlashForge Google Group when you're ready for help.


Question:
I found a story about someone 3D-printing equipment for their Lego minifig, using an Ultimaker. (Article is in Dutch, but accompanied by photographs).

I noticed that what they made weren't the actual connecting bricks, but the tools used by the minifig. And that even so, some filing and a dremel were needed afterwards to make them fit properly.

I'm told that to make something connect properly with real Lego, the machine needs to be tuned very precisely.

So, what resolution is needed to print bricks that will connect with normal Lego bricks?

Answer:
It's really more about calibration than resolution -- a poorly calibrated printer will have dimension errors that prevent mating with true LEGO bricks or other printed bricks.
Also, "resolution" is an incredibly loaded term for 3d printers, because it can mean a lot of different things. But we don't need to get into that right now. There are really two big things to worry about: layer height and extrusion width.
Layer heights of 0.1mm or 0.2mm should be fine. Coarser layers may run into surface finish issues that make the bricks difficult to put together or take apart. There probably isn't much reason to go finer than 0.1mm for this application. Almost all FFF printers can do 0.1mm layer heights as long as it is reasonably well-tuned.
Any typical household FFF printer with a "normal" nozzle size can print fine enough for the bricks to work. It just needs to be tuned well.
The smallest "must have" feature in a standard lego brick is the 1.6mm thick wall around the sides. The typical minimum printable feature size for an FFF printer is 2x the extrusion width, because the slicer will place a path on the inside edge of the shape and the outside edge of the shape. (Some slicers will allow single-extrusion features, but this is not generally recommended because it makes weak parts.)
So, how wide is the extrusion width? It's adjustable, and different slicers auto-recommend different values, but as a safe rule of thumb it needs to be between 1x and 2x your nozzle size. There are some volume calculation quirks in different slicers that may encourage larger or smaller sizes, so sometimes people recommend [extrusion width = nozzle size + layer height] particularly with Slic3r. This is very system-specific.
Assuming you have the most common stock nozzle with a 0.4mm orifice, and also set the extrusion width to 0.4mm, the slicer should put four strands in the walls of the LEGO brick. That's good.
Where it gets tricky is if you have an extrusion width that does not evenly divide into 1.6mm. Say you are printing with an extrusion width of 0.6mm. There is enough room in the wall of the part to place two full 0.6mm perimeter strands... but then a gap 0.4mm wide will be left in the center. You can't put another 0.6mm strand into that 0.4mm gap. Different slicers handle this different ways. Some will leave an empty space between the walls, and you get a very weak print. Some will mash an excessive amount of plastic into the gap, causing poor print quality as excess material builds up more and more on each layer. Some will push a smaller-than-commanded strand to try to properly fill the volume.
So, the general advice with small features is to make sure your extrusion width goes into the part's minimum thickness a reasonable number of times.
[Feature size / extrusion width < 2] is BAD
[Feature size / extrusion width = 2] is GOOD
[2 < Feature size / extrusion width < 3] is BAD
[Feature size / extrusion width > 3] is GOOD
Although these will vary somewhat by slicer -- older slicers like Skeinforge tend to have more issues with this than newer slicers. What you should do in practice is check your slicer's print previewer to see whether it is leaving a gap between the strands. Then adjust extrusion width and perimeter/shell count to try to get an intelligent output. There's some trial and error involved.


Question: I was just shopping for filament, and saw some glowing claims about PETG being as easy to work with as PLA, but as strong as ABS, and less brittle. Anyone know if that's actually true, or what the tradeoffs are?

Answer:
PETG is great stuff to work with. It is stronger than ABS also. It prints slower than ABS and PLA. The formulas vary quite a bit from vendor to vendor. I have used 3 brands, and each of their properties vary.
From my experience you do have to be careful with moisture. You'll be able to tell you have moisture in your filament if you start hearing a slight hissing and popping and an increased number of structural zits on the object. Moisture will also increase the problem listed in Mark's post below regarding the accumulation of filament on the nozzle.


Question: Stereolithography produces parts by projecting ultraviolet light on the top of a vat of liquid photopolymer, causing it to harden.  CLIP produces parts by projecting ultraviolet light through the bottom of a vat of liquid photopolymer, causing it to harden.  This seems like a minor difference, yet CLIP is reportedly much faster (I've seen numbers as high as 100x).  Why is this?

Answer:
It's important to understand what specifically is being compared.
CLIP is much faster than bottom-up technologies that require a peel step between every layer.
For example, the Form1 galvo SLA printer tilts the resin vat to separate the transparent bottom from the print. That is, by far, the slowest part of SLA/DLP printing with most modern light sources. Where the speed comes in is that without a peel, a continuous "movie" can be used to cure the resin rather than a series of alternating images and peels.
Top-down printers can print dramatically faster than bottom-up-and-peel printers. CLIP is not necessarily faster than top-down. For example, the Gizmo 3D line of top-down printers are very similar in print speed to CLIP. (
http://www.gizmo3dprinters.com.au/
)
Most "consumer" SLA printers these days use bottom-up-and-peel techniques, because this has some practical advantages over top-down printers:
Way less resin is required to fill the printer when the part is pulled out as it builds rather than being lowered into the tank (along with the Z stage) as it builds. Resin is expensive. This also means bottom up printers can be smaller and have fewer mechanical parts such as leveling devices submerged in resin.
Standard resins contain an inhibitor chemical that prevents polymerization in the presence of oxygen, which causes the surface layer exposed to air (and low-level stray light) to not cure. So top-down printers must shoot light through a non-curing layer before reaching curable resin. This makes the tuning more sensitive and can somewhat reduce detail compared to a bottom-up printer curing right on the window.
Replacement vats or windows for bottom-up printers may be seen by manufacturers as a profit-generating consumable, since they have to be replaced somewhat frequently.
Top-down printers have to worry somewhat more about resin flow rates as the part is lowered. Air bubbles may be pulled into the resin or the fresh resin layer above the part may vary significantly in thickness if the part is submerged too fast for the resin viscosity. (Admittedly, bottom-up printers will experience excessive suction forces and potentially break off bits of the print at high peel speeds.)
CLIP is a bottom-up technique that doesn't require a peel step, because the vat creates an oxygen layer over the window that keeps the resin from curing directly on the surface and sticking. In that way, it arguably performs more like a top-down printer than a bottom-up printer.
Top-down printers that are designed to overcome the above issues and use high-intensity light sources can achieve exceptionally high print speeds. This includes similar "continuous" build techniques used as in CLIP.