Cut Quality Issues with Clearpath Servo

[carboncymbal]

All,

I am running an Avid Benchtop Pro with clearpath servos and am having poor cut quality.

I'm wondering if someone could help point me in the right direction. These scalloped edges are programmed as straight cuts that are running approximately 45 degrees. The cut is moving the X and Y axis simultaneously. Previously I have noticed a pretty visible "stuttering" of the X axis, but haven't noticed it on the Y axis. I have attempted to tune in a way that reduced the positional error as viewed from the scope in the MSP.

Upon closer inspection, it seems that I need to stiffen up the table prior to running the autotune procedure. I can see some "rocking" present during X axis movements of the benchtop machine.

I'll start by trying to stabilize the structure, but figured I'd see if anyone had any pointers generally.

[Markostojic]

Hi ,I had the same problem with my clearpaths as i have diy router based on on your cnc, i disconnected one of the axis on my y axis and autotuned the motor and transfered the settings to the other y axis motor and to my x axis and stiffened up the motors on fine tuning and cut quality on circles were spot on. Hope it helps

[cnckeith]

the machine has to be in good mechanical condition (rigid, straight, square, free moving (no drag or sticktion), and low lash for good cuts that is just as important as having the cnc setup properly. post a fresh report.zip and photos of the machine and we may be able to help you.

[RichMaple]

I've never experienced this with my clearpath machine but I will say it does seem to be a mechanical issue or (related) a servo tuning issue. Not sure how you tuned your motors to begin with (what intensity level, what torque level, what range of movement, etc) but something is funny for sure. Have you tried just jogging your servo from the USB software? (IE taking Centroid out of the loop)? That said, you mention "rocking" and such.... have you investigated the mechanics? IE the state of the ballnut/rack, the linear guides, tried to push your machine by hand to see if there is noticeable lash, etc, etc?

[carboncymbal]

All,

Thanks for the suggestions from everyone. The feedback aligns with my own thoughts of likely issues.

I did make the changes I discussed, specifically stiffening the table the machine rests on significantly. Upon closer inspection, I found that I could (with some effort) create an oscillation of about .060" in the table. After I stopped "rocking" the table it would keep oscillating for several periods before stopping. I welded in cross members on the table, ensured the leveling feet were in firm contact. I redid the clearpath autotune procedure (100% torque). This significantly improved the cut quality! It is definitely fully usable now, and could probably be improved slightly with some additional attention to the stiffness of the table and tweaking of the servos.

Thanks everyone for your feedback!