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Issue with rounded edges

nontiveros86
Observer

Issue with rounded edges

nontiveros86
Observer
Observer

I've been having a problem cutting my rounded edges correctly.  I'm working on a guitar model and when I cut the pieces out there's always a lip round the edge where it should be flush.  This has happened on the backs of necks as well as bodies.  Here is the process I use:

 

1.  3D Adaptive Clearing

 

I usually leave the default settings here.  1/2" flat endmill.

 

2.  3D Parallel

 

1/4" ball end mill, stepover of 1.5 mm, perpendicular passes added.  I usually use Silhouette and tool center on boundary, otherwise the endmill goes all the way to the bottom of the model and tries to move with a significant portion of the non-fluted shaft in the wood.

 

3.  2D Contour

 

Selected contour is the outline of the piece I am cutting.  1/2" flat endmill.  Multiple depths with maximum roughing stepdown at 6 mm.  Everything else is left at the defaults.

 

I've tried different settings on the 3D Parallel and 2D Contour toolpaths all to no avail.  Maybe there's a simple solution I've missed, or I need to reorder the toolpaths?  Maybe even use different toolpaths?  I've noticed that the lip is present on the simulations as well.  Any advice would be appreciated.

 

I've included pictures of the body model, CAM simulation, and result from the CNC router.

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Anonymous
Not applicable

Just spit-balling here for some suggestions:

 

1) Try using a smaller stepover on your parallel pass.

 

2) Try using a larger ball mill (perhaps 1/2") as well as a smaller stepover.

 

3) Try using a different toolpath -- I've had really good finishes with the scallop pass on aluminum.

 

 

Everything said, I'm about 99% your issue is the the 1.5mm stepover. That's quite a large leap, approximately 0.060". I do parallel finishing passes of 0.005-0.010" on aluminum plastic injection molds. I would suggest first trying to change your stepover somewhere between 0.250-0.350mm and perhaps even work it down further from there.

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nontiveros86
Observer
Observer

Looking at the simulations, changing the stepover seems to have aided a lot.  The furthest down I had gone before was 0.7 mm, the 0.25 seems to make a significant difference.  I'll know for sure when I cut it out.  However, the machining time goes way up... on the longest path the time went up to 8 hours when adding perpendicular passes.  Without, its more manageable.

 

I'll also look into getting a 1/2" ball endmill.

 

Thanks for the help!

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Anonymous
Not applicable

Well that's good news. It's entirely up to you as far as time goes--it's your job and your program. You can bump up the feeds/speeds or you can increase the stepover slightly to get a "close enough" finish and then, I'm assuming, do some sanding. You'll just have to find that happy medium between machining and hand finishing. Glad I could help.

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