Swift... "shuddery" operation

I’m having trouble doing a contour cut that I’ve done a several times before - it’s making a loud mean noise (on a new bit)… and so I reduced the step down height and feed rate. On restart of the job, I’m cutting some air as it passes over areas it cut on the previous attempt and I’m noticing that when it is running along certain paths of the contour it has a very slight “shudder” under no load whatsoever. I am guessing this is bad? Is this “known and ok” - or does this sound like red tag offense?

I can try to take a video I guess…

I experienced the same thing on swift a few weeks ago. It only happened once and then I couldn’t reproduce it, so I figured I had done something wrong and didn’t report it. I was boring some 1” holes in plywood; toward the front of the bed, it seemed like it was slow and “shudder-y”, but was performing fine toward the rear of the bed.

Here’s a photo of the resulting cuts

I was able to get through the cut fine with more conservative settings. I’m doing flat pockets now and it seems completely fine. Odd - well…. I guess - consider it “logged”…

I’ve run into that issue before on aggressive curved toolpaths. While I haven’t done any verification testing, it is likely a result of vibration occurring due to deflection in the bit as moves across the material faster than it can cut. This could also happen with an overly aggressive step over / step down, or a dull bit even at more conservative feed rates. Another thing to check is how the curve is shaped as a vector. What may initially appear to be a smooth curve might be a series of very short straight lines or angled node points when zoomed in closely. The machine will follow this path and make jerking movements at each node intersection.

The shuddering was happening even cutting air - so not a material/speed problem…. But that is a super interesting thought on the model node points. I will investigate that when I sit down at fusion next time