<p>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.</p>

<p>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.</p>

<p>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?</p>

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

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.