Hole and Shaft Test question

How are folks orienting these two Formlabs parts in Preform? I’ve tried orienting them flat, but that resulted in the pin not fitting in any of the hole sizes.

diagonal orientations generally offer better dimensional tolerances- but even then, you are going to have to allow a certain slop between close fitting parts.
The laser is only SO accurate and the Z height is even less so. Add to that that the laser can REFRACT and reflect slightly - and the resin shrinks just a little and you will find that small holes print consistently smaller than modeled… and shafts usually come closer to correct dimension, but still have a range of variance.

Formlabs has a white paper somewhere that deals with close fits and the approximate tolerances you should model in to ensure a better fit.

1 Like

I designed and printed up some GO, NO-GO gauges to give me an idea of what kind of clearances I need to consider when designing close fitting parts. As I recall, I made them with 0.5mm, 0.4mm, 0.3mm, 0.2mm, 0.1mm, 0.05mm, and 0.025mm clearances.

I’d upload pictures; but Formlabs says my files are too big. GRRR!

So I’ve been using the Hole and Shaft test that I printed flat out of clear material, as the Durable material print, again, doesn’t fit anything. I’m using the actual clearance I want, .05, and take into account .05 for each part, and .01 for each part for the change to .STL from a Solidworks file. So far it has made for a tighter clearance than it should, but still works for this particular application. Threads however have been a different story. I have to go big on those, and sometimes its a rather loose thread, and other times it will not even fit they are so close.

I’ll print the test on a diagonal and see what happens.