[GregGleason]

I tried cutting a hemispherical void of 0.502" in diameter in a piece of MDF. I used a 1/4" ball mill for the milling. The void looked fine, but when I placed a ball with a diameter of 0.500" in the void it sat noticeably above the equatorial plane of the ball (like the pocket was either too shallow or the sphere-shaped void's diameter was too small. Any thoughts of what went wrong?

Greg

[Lennings]

Hi Greg,

Indeed the ball in your example will not exactly fit the hole that you machined, for a few reasons:
- the STL approximates the real sphere using flat triangles, making the hole a bit smaller
- DeskProto machines using toolpaths at a certain path distance (the Precision values). DeskProto will not remove too much material, so the tolerance value will always result in some extra material left. See the Help file on "Distance between toolpaths".
- The calculation algorithm works with Z-grids (see the Help file), and as a result the void that is spherical in the STL will not be exactly spherical in the resulting part. For this reason DeskProto is not suited for toleranced mechanisms like a piston in a cylinder.

Lex.