Simplify3D User Forum

I hope this is not a stupid question, but let's say I printed a 30mm cylinder with a 10 mm hole, and then I added a 1mm value.

I think I'm right if I say that the outer cylinder will then be 32mm, but then I don't know what will happen to the 10MM hole?

I guess it can only become 12mm?

No, it goes inward. If you put a positive value in for the size compensation, then the part grows outward everywhere. So the hole would become 8mm.

If you put in -1mm for the size compensation, then the outer cylinder would become 28mm and the hold would become 12mm

This feature can be a bit confusing at first.

The way I like to think of it is as if your part was a sponge. If you use a positive value for Horizontal Size Compensation it's like wetting the sponge: it grows in all directions, with the outer perimeters moving outward and the inner perimeters moving inward. If you use a negative value it's like drying out the sponge: it shrinks in all directions, with the outer perimeters moving inward and the inner perimeters moving outward.

Hope this helps!

Also, because the dimensions are changing everywhere (in X and Y) you usually want to use very small values, like 0.1mm or even less. If you need to overcome a larger fit issue than that you may be better off just scaling the entire model.

Yes... positive inflates and negative shrinks. Sponge is good analogy.

Best way to understand this may be to see it for yourself. Load up a captive planetary gear, slice, view the preview... then re-slice and preview using different horizontal size compensation.