View Full Version : Changing velocity setting in Mach3 (stalling)

11-04-2016, 12:39 PM
After a few successful jobs, I've had an issue with my 6040. On rapid movements from one job to another, the X axis sort of stopped suddenly, then carried on and started cutting in the wrong place. Am I right that this is a stall? It sounded like what happens when I run into a limit switch

I've been reading this thread here (http://www.mycncuk.com/threads/7006-CNC-router-occasionally-makes-jarring-noise-and-home-jumps-when-it-does-this-Help%21%21/page4) where someone has the same problem and although in the end his solution was to change all the electronics (I'm considering it possibly), I'd like to try the fix that was suggested by lowering the velocity.

My setting are:
steps velocity accel' step dir
X 320 3000 200 5 3
Y 320 3000 200 5 3
Z 320 800 100 5 3

It was recommended in the thread to try:

steps velocity accel' step dir
X 320 2000 200 10 5
Y 320 2000 200 10 5
Z 320 800 150 10 5

Is it just a case of plugging those numbers in and trying it? Or is there some maths needed beforehand?

PS. I tried the same job "run from here" after it happened, but each time it started moving to the next toolpath, it stalled. I fixed it in the end by post processing that particular job in HSMExpress on it's own. It seemed happy then.

11-04-2016, 01:18 PM
Just do a test with the velocity on the stalling axis set to half what it currently is, stalling halfway through a rapid move does sound like there's some mechanical element to the issue though. Does it always stall in the same region of movement?

11-04-2016, 02:46 PM
Well I had a program running that pocketed 3 small holes, then did a contour around the part. After doing the holes, it was moving to the contour position when it stalled.
Then I clicked emergency stop.. Homed it. Then I scrolled through the Gcode to the point where the contour job was, click run from here. And on the same move, from the posistion of the last hole to the contour position it stalled again.

Then I redid HSMExpress, to just do the contour job and not the holes (which were already done) and all was well.

However, I didn't try to repeat it this morning.. stupidly I changed something that I had read fixed this issue on somebody else's machine.. (putting the PC driver to "standard PC" rather than ACPI) and now it's not stalling there during that job (in air.. moving)

I should have tested it this morning without changing anything to make sure it was repeatable every time.

I guess I'll continue to monitor it.

There was another moment that it stalled previous to that halfway through a pocket program on the Y axis this time. Again whilst moving in air to its next hole.

12-04-2016, 12:04 AM
Nope, that didn't change anything. It stalled again.. this time even when I was jogging manually back to home.
I switched the velocity from 3000 to 2000.. (no other changes) and it finished a simple contour program ok. Will continue to monitor it like this.