I’m new to CNC machining and am wondering about cusps. Is it possible to remove cusps in later toolpaths, such as a Pencil toolpath? Or are cusps just a reality of machining and I’ll need to sand those off by hand?
I have a fairly simple part with a fillet - please see the below link. The fillet always ends up with cusps. I’ve tried adjusting tools, using different toolpath options, adjusting stepover, adding a Pencil path, but always end up with cusps. Any tips? Or do I need get out the sandpaper?
This is in Fusion 360 — you should be able to exert sufficient control there to get a part which is ready to go save for maybe a quick pass w/ a file or deburring tool.
OK. Thanks. It’s essentially at the point it only needs a quick pass with a file now. I was just wondering whether I might be missing some way to produce a super smooth finish.
I don’t have Fusion, and have no idea what your part looks like,
Typically you would want to cut with the largest ball mill you have that will cut that fillet. i.e. same radius or slightly smaller. Cutting along the fillet instead of across it will also help a lot. Smaller stepover should always mean smaller scallops (cusps). If you are zig-zag/lace/raster cutting, a finish pass at the opposite angle (± 90°) will help clean up scallops. A path that just cuts along fillets like a flowcut or pencil cut will save a lot of time & yield a nice finish.