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Cutting circles with CNC
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Cutting circles with CNC
Should a CNC be able to cut a perfect looking circle? I’m trying to make solid wood rosette rings. I made the tool path a profile cut. The top and bottom of both Y positions come out uneven in width than the rest of the ring. I’ve tried slowing down the feed and plunge rate, but it doesn’t seem to make any difference. I have an old second generation Nextwave CNC shark and use Aspire for CAD and CAM. Linear cuts seem to be accurate, but circles always give me trouble.
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3 Replies
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The answer to your first question is yes.
Eccentricity at only the top and bottom of the arcs makes me wonder if your post processor is perhaps interpreting the arcs incorrectly (assuming your circles are properly drawn arcs showing only the nodes necessary to create a perfect circle). Are you sure you are using the latest/greatest post processor that exactly matches your machine? And have you double checked the vectors you are using to see if the nodes look exactly right?
Another possible suspect is your hold down mechanism: a) to make sure the piece isn’t moving on the table; and b) using tabs to ensure your piece doesn’t move when the cut through completes.
Assuming you are only cutting a millimeter or two of wood, it is highly unlikely that tool flex is the issue, even if you are using a very small end mill for the profile cut. Hopefully it is not a mechanical issue like lead screws.
As you may know, Vectric has a forum that is very good. If you post the file there (along with the g-code that is being generated by the post processor) and a statement of the problem, you are very likely to get more helpful input. And there are a lot of the folks on the forum who use the Nextwave Shark.
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Thanks Michael,
It may be a mechanical issue. My machine is about 12 years old and has seen a lot of use. I’ve only recently started making my own wood rosette rings. I used to buy them premade from LMI. I’ll chime in on the NextWave forum and see if I can resolve this.
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Scott,
I am certainly no expert on the technical aspects of cnc. However, i have been running cnc’s to aid my guitar building a long time, and over the years, I have owned 3 or 4 different Next Wave machines. I was always able to cut perfect circles. That said, early Next Wave machines were no the most heavy duty things. The best thing I found about Next Wave was great support. I bet you have a worn part, or something like that, and next Wave support will be able to help you.
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