Scallop z height toolpath not horizontal

[sendithard]

I'm doing lockwoods part from youtube and separating out the bottom and top scallop to eliminate redundant paths.  I noticed while zooming in that the z height is moving every so slightly up and down. We are talking .0003 moves so every so slight, but seems odd b/c both my input selection curves are perfectly horizontal.  I am wondering if this due to the tolerances or if this is normal behavior for z to change in those ever so slight amounts. Any ideas to eliminate this? I like the scallop operation due to its use of slope and ability to what looks to me like maintaining very similar cusips.  Thanks.

[Steinwerks · Accepted solution]

Yes this is a surface triangulation tolerance issue. If you change the internal expression to "tolerance*0.05" you'll see very little calculation time impact but a large reduction of the Z shifting that should get filtered out by the post (IE out of four decimal places in inch mode).

[sendithard]

Nick,

Thank you, I would have never known about that setting. What you said made me curious so I threw down a quick 3d contour to kind of replicate the scallop. I noticed the 3d contour does not suffer from the z height issue that the scallop did using quite similar inputs.  Do you know why this is?  Also, if you have time, is the attached file the way you would have set up the 3d contour to replicate the scallop somewhat? I'm trying to improve my skills.  Thanks again.

[Steinwerks]

Who's Nick? 😉

I wouldn't use Contour for that curve, but I would consider using Flow or Blend, or Steep and Shallow if you have the extension. The way that passes are generated is the underlying reason for the fluctuation in the Z height in this instance.

Contour essentially acts as a vertical slicer and adds passes at your specified stepdown where Scallop attempts to collapse the toolpath at a specified distance following the surface itself. Contour usually winds up with pretty poor shallow surface finish usually due to inconsistencies in stepover, where something like Parallel winds up with the opposite, so splitting the toolpaths using Slope limiting with an overlap is useful (part of what Steep and Shallow does automatically).

[sendithard]

Thanks.....lol, I have a buddy named Nick stein.....my mind was lost in space. Thanks . I just saw your name is neal...even weirder.