3D adaptive clearing with rest machining needs axial stock to leave

[andrewbarton]

Hi,

I came across what appears to be something odd using 3D Adaptive Clearing, rest machining and progressively smaller end mills.

I have attached a sample file showing the problem (if indeed it is a problem).  There are two CAM setups which are identical except for the last operation with a 1mm end mill.  In TEST2 with the 1mm end mill I needed to add 0.0026mm axial stock to leave in order for the tool path not to include the the already cleared floor of the part.  In TEST1 with 0.0025mm (or anything from 0.0 to 0.0025) axial stock to leave, the tool clears already machined areas.  I tried the three options in the rest machining "Adjustment" but none made any difference.

Am I doing something wrong??  Is there something significant about 0.0025mm being close to a tenth of a thousandth in inches?

[seth.madore]

Your Tolerance in all the toolpaths is set to .1mm. The thing about tolerance in 3D Toolpaths, is that it's applied in 3 axis. Thus, your toolpaths can vary in the Z axis as much as .1mm. The result of this is that when using Rest Machining, the "rest" function checks against an STL that is created behind the scenes. With that much tolerance applied, it's quite likely that the generated STL actually does have material on those sections.

One of thing to do (after tightening the tolerance) is to right click on the toolpath(s) and select "Compare and Edit".

At the bottom of the new window that opens, key in "tria" and it will give us this result:

Change that to 0.05, this will create an even tighter STL model. You can also right click on that value and "Save as User Default" which will retain that value for any Adaptive toolpaths created later.

[andrewbarton]

Thank you Seth,

Once again a perfectly logical explanation!

I sort of assumed that the tolerance was only applied to curves and as the floor was perfectly flat, any STL triangles on that plane would also be perfectly flat.

Anyway, I am now educated...
Thanks again

[seth.madore · Accepted solution]

@andrewbarton hey, I (and a lot of others) learned these things in the same manner, so those of us that do know these things try to pass on what we've learned 🙂