richardwheeler

My $0.02: Printed holes are smaller mostly because they are NOT circles. The holes are modeled as polygons that have short chords along the perimeter of the desired bore size. It is these chords that make the hole "smaller" more than any shrinkage or elephant foot. higher resolution STLs will help mitigate this somewhat but as was mentioned elsewhere it is better to model the hole slightly oversize to make the opening the right size for a bolt. Remember that a pin will make contact on only three points inside a bore. with very small holes it is sometimes better just to make it triangle-shaped if you need it accurately printed. Shrinkage DOES have a dimensional effect on linear dimensions that becomes stronger as the footprint gets larger on the bed. For prints under 200mm square I use .6% (as in .006) for ABS and .3% for PETG and PLA. under 100mm square I use .5% and .2% respectively. I make parts that are used in machines and fit together precisely, I normally can achieve dimensional accuracy within .010mm-.020mm without too much problem but that usually requires a test print to evaluate first, especially over 200mm. This is true for both my MassPortal Grand Pharaoh XD and FlashForge Creator Pro