Model Design Tolerances in CAD

being new to this 3d print thing i was curious about when modeling something to be made in any CAD program what tolerances should be taken into account? for example, if im making a circular hole and a plug for it; do i make that hole 6mm and the plug 6mm print it out and expect it to fit together? Using ABS? PLA?

I generally leave a +.01 tolerance for the circular hole.

If this doesn’t work, you’re probably inadvertently overextruding. The easiest fix is to lower the flow rate or extrusion multiplier depending on your slicing software. I find that 90-95% work best when printing with eSUN ABS.

The better way to adjust this is to sample the filament diameter of your spool, calibrate your e-steps.

Rather than printing the circular hole and printing the post to calibrate, print a circular hole that should fit around a known post solid. A socket cap screwhead is typically pretty good gauge. There’s should be a bunch of exposed socket heads on the machine… search online (mcmaster-carr) for the diameter of an M3 or M4 socket head…

Unfortunately, every type of plastic has different printing characteristics. As a result, if you want really tight tolerances, you need to experiment. kcchen_00 suggestion of 0.01mm is a good starting place.

Here’s a few thumbcaps that fit M3 and M5 socket cap scews. The diameters for the socket caps are 5.6 and 8.56 respectively. They should snap on to the socket head screws. Good for calibrating flow rates since they print fast.
M5 Thumbscew Cap SingleColor.stl (276 KB)
M3 Thumbscew Cap SingleColor.stl (278 KB)

Do flow rates differ from one material to the other drastically enough that you want to do an esteps calibration for each new roll you use material wise? Or does one just rough set the esteps via the free air calibration and extrusion method. Then fine tune everything from there from one roll to the next?

I haven’t bothered much with my e-steps… one of these days I will go back and calibrate. I use the flow rate percentage exclusively so far to manage the sizing.

I usually have to print black a 1-3% less than other colors of eSUN ABS. So I would say its not drastic, but some tweaking may be necessary.

ok. is it crazy to have to change the extrusion multiplier to .80? .60? …to get something to print properly? or is that more or less the norm?

i calibrated my esteps and am in the process of fine tuning with the extrusion multiplier, but i was just curious as to whats normal and whats not here

I think it would be strange to drop the flow rate below 90. Check the e-steps (as you’re doing) and sample the filament diameter.