Ripples in my dishes

[sunnytrails (Roy Murphy)]

When using the 3/4 dish bit to cut dish models the inside edges are left rippled. what can i do to prevent this. I have tried using smaller bits and slower feeds

[ben2ek (Brian)]

Can you post a pic? Sounds like chatter. A finishing pass would do the trick. I run into this on literally every cut because I probably go too fast and deep, but it’s a tradeoff. Here’s what I do, and what is recommended from some of the help docs.

1. Create a tool in the library for “Roughing” and make it ~0.05" bigger in diameter than the actual bit. Normal DOC and feed speeds. This makes the cg-code cut 0.05" away from the contour lines thinking that the bit in the spindle is actually bigger than it is. I cut at 120 IPM, .375" DOC with a compression bit.
2. Create a second tool in the library for “Finishing” with the actual diameter. Full DOC and faster speeds. I do 150IPM with a .25" compression bit. You can probably do the same, but do it incrementally.
3. Make a tool path the Roughing bit AND the finishing bit. Finishing obviously coming after the roughing.
4. Run your cut.

You’ll still get the rippled chatter marks on the roughing cut, but the finishing cut will take 0.05" off and leave you with a super smooth edge.

If instead you’re talking about the Bottom of the tray, then the ripples are caused by your spindle being out of plumb/square. It’s not perfectly straight up and down on all axis. You’ll need to tram the machine as best you can.