Machine Stutter / Notching Phenomenon

Hello everyone,

I am new to LinuxCNC and thanks to the help of people here and on the Facebook page i have managed to get everything working as i had it previously on my DDCSV1.1 Standalone Controller - LinuxCNC is much better for me and i love the functionality of gmocappy on my Touchscreen Display.

One problem i am facing with the machine, is that i have some kind of stutter when it is moving, im not sure if the machine losing steps, but if it is i am unable to see this in the surface finish / any dimensional indication on the (one) part i have run so far.

Abit about my setup:

Computer: static.acer.com/up/Resource/Acer/Docs/NZ...0ESS%20PPT%201.4.pdf
Drives are Leadshine AM882's Using x4 Microstepping
XY Have 1610 Ballscrews
Z Has 1605 Ballscrew
Nema 34's

G Code is from Solidworks / HSM Express using the ECM Post - Seems Fine.

I ran a latency test overnight and my max came out at ~24k, however it was not doing much at this time.

I opened Firefox etc and it eradically jumped to ~43k for a split second - i would never use this computer to online usually and especially not whilst running toolpaths.

I have the base period currently set at 40k, however this did not seem to improve anything.

I have no idea how to tune any of the Latency / Period settings.

I have disabled anything Power Saving related in the BIOS, Disabled Audio etc.

Im not sure if this computer is suitable or not. I can use another maybe.

I attached a picture and have highlighted in red where the stutters have occurred during a facing toolpath. This was a 1mm DOC Pass in HDPE @ 1250mm/min - It cuts like butter.

I also have a video but it is pretty hard to hear the notching, you can hear it if you listen closely.

This happens regardless of if the spindle is on or off, it happens both when jogging manually and also when running code.

Video: YouTube Video

Any help is greatly appreciated.

Thanks

Alex

EDIT: I have diagnosed that the machine runs buttery smooth in stepconf but once running from a GUI it loses steps.

There appears to be no latency issues

If it's mechanically rigid then maybe the step lengths in the INI are not suitable for the drives? Could also be electromagnetic interference. Is everything properly shielded and grounded?

Hi Aciera,

Yes i admit i was not sure what to fill in on those fields when first doing stepconf.

I had a look on the Wiki and found the closest match to my drivers from Leadshine for the Volt / Amps, this was the:

Digital EM806
80V
8.2A
2500
2500
10000
5000
Rising Edge

I have no idea how i would identify these values for my Drivers - Trail and Error? Also i have no idea how to update those values now.

I have made changes to my .ini and .hal and dont want to re-run stepconf

I think everything is grounded correctly, all of the motion and control wiring is done with shielded 4 Core CY Cable, i know i have an EMI Issue with the VFD, and i have a filter coming to hopefully help with that - however this problem is persistent whether the spindle is on or not.

Thanks

Alex

Can you post your hal and ini?

Yes, i have attached them, i am using gmocappy with the tool probe preset, i hope this is ok and not a bad thing to do.

I just found a a more rich version of the manual for the drivers, and it looks like maybe i can configure those values in the drivers using an RS232 Cable and some software. I also noticed this at the end of that section:

Remark:
a) t1: ENA must be ahead of DIR by at least 5ms. Usually, ENA+ and ENA- are NC (not
connected). See “Connector P1 Configurations” for more information.
b) t2: DIR must be ahead of PUL active edge by 5ms to ensure correct direction;
c) t3: Pulse width not less than 2.5ms;
d) t4: Low level width not less than 2.5ms.

Thanks

You have:

Maybe try:

[edit]
more info:
linuxcnc.org/docs/html/man/man9/stepgen.9.html
And for the other two axis as well.

Thanks very much i will try that in a little while after work, i have no idea how those values were calculated. Are they extremely low in comparison to what you would usually see? Do you think its worth me downloading that software to tune the drivers? Maybe i can match what is on the drivers and what is in LinuxCNC?

In case you missed my edit:

linuxcnc.org/docs/html/man/man9/stepgen.9.html

As to tuning the drives: For stepper motors its not usually necessary but why not have a look. I'd try the modified timings in the ini first though.

Thanks guys for the suggestions - i was worried i was going to be into something way over my head at this point.