<p>When modelling for 3D printing, can I distinguish somehow the type of infill in various areas of the model? Say there may be some areas in the model where I want 100% infill (maximum strength) but some areas where the infill can be less (maybe 25%).</p>

<p>I am new to 3D printing, doing my first model (enclosure for electronics - camera module). Using tinkercad.com only so far. Places where 100% infill is wanted are usually walls of the case and "threads" for the bolts but I want to make the enclosure as stiff as possible as a whole so I am thinking about using some sparse infill in the "free space" inside of the enclosure (so that it does not break so easily when it falls to the ground etc). I just do not know how to define this within the model.</p>

I found out I misunderstood some principles of designing/modelling for 3D printing.
I designed my object for 100% infill which is not really necessary. It turned out that one does not mostly have to take care of the infill % and just model the object for example as solid 3D cube and the printing service will then take care of it to print well, hopefully slicing it well for printing and choosing the correct infill percentage.
So instead of designing a "hollow" cube with 3mm thick walls filled with 100% infill and free space inside, one can design a solid cube and the printing service will then print it "somehow" - they may make the walls only 1 mm thick but fill the inside of the cube with 10% infill which may work just fine for final object stiffness etc.