Problem with jerky cutting

71taa

What CAM/postprocessor is being used? Helical moves are disabled?

Had severe stepper shakes before in case of different/wrong settings of pulses per mm for X and Y. Haven't tried to solve it - as it was test setup with random settings for drives not attached to ball screws.

Also it would be helpful if you are able to share some of your test files (smallest ones).

71taa

I've runned the attached code on my test rig (ddcsv2.1 + closed loop stepper on X). Spent some time to rule out problems with interference (unshielded cables laying everywhere) and received similar picture. Not full stops though, but clear reduction of the speed (sometimes till the zero), esp. when it comes to the middle of the programm.
As PPRINT earlier, I've suspected problems with micromoves and arc interpolation alghoritms of the controller. So I've played with settings, and for 8000 subdivision of steps on driver, 1280 pulses per mm and 300mm/s2 in controller I've received stop-free execution, but still with clearly seen heavy decelerations while in problem spots. 100mm/s2 had much more stops/decelerations, for example.BTW while I had problems with interferences I had a lot more shakes and stops on the stepper, probably controller is sensitive to them.

71taa

enjoy_cnc Posted at 2018-5-8 22:07
Hello Androcles

In case if it will help - added a video of my test setup as well: https://youtu.be/9QCczdX6cAs
Timing (video):
3.51-3.52
4.01
5.34
Hiccups before/aftter the vertical center of the scallop in the part there is no significant changes of X coordinate. That's the most strange thing here. As there is no mechanics - the tonality of the stepper sound could be used to locate those spots easily.

8.00
8.08
8.23
... and so on (the closer to the end of the programm - the more prominent slowdowns). Here we have clear corellation with the moment then the X axis steps betwen minimum negative coordinates and minimum posotive coordinates. Probably it's expected, but maybe not:

X-0.117 Y-20.354
X-0.003 Y-20.86
X0.002
X0.171 Y-20.101
X0.332 Y-19.343

And later it starts to slow down in different parts of the programm.

The settings are:LCDA357H+LC57H3100 on the X axis only.
24V/5A dedicated for the controller, 36V/12A for the stepper driver. No limit switches/probe/etc
Switching off the encoder on the stepper doesn't change the picture (checked as well)/
The driver is 5000 pulses/rev. Tried different subdivisions on driver/pulses per mm in the controller - slowdowns are present, but change in scale/time. Tried 91 and 93 builds, tried enabling of the soft arc - no difference