Need Help with Mach-3?

[woody8750]

I have just finished my first cnc router and seem to be having problems with the Mach-3 portion of the controls. I am using BobCad v23 with the verifing program and all looks good there when I proof run the G-codes. When I run the program on my machine the "Z" axis seems to keep on lowering the "Z" "0" and going deeper into the part. I have everything that I know of set to G90 and absolute, and am able to run small parts less than 1000 lines of G code, but when I get to larger programs the problem shows up. After trying to run and stopping the program due to nearing the lower limit on "Z" If I "Z" zero the tool it will actually be lower than the point of program stoppage. When looking thru the programs I dont find any "G" codes reseting the "Z" zero or changing the mode to incremental. Need advise on what could be going on or where to look next. This is not limited to just one program, but happens on all larger ones that I've tried.

[LeeWay]

Sounds like it might be backlash in the Z axis. When it is switching direction up to down and vice versa, it is loosing steps and not gaining them back due to the weight of the router.

[GaryCorlew]

Your most likely losing steps, things I would check are:
Something binding
Something loose(coupling, belts, what ever your driving it up and down with)
motor too small(lower acceleration, RPM too attempt to resolve)
Amperage to low
Incorrect step calculation
resonance
This is a problem in every program you run, its just on the shorter ones the step loss is less noticeable

[jalessi]

I am assuming you have stepper drives, what type are they?

Several factors may be a problem.

1: a timing issue
Cure: enable Sherline Mode

2: Missing steps
Cure: Slow down feed or install larger stepper motor or some sort of torque multiplication.

3: Not enough computer cpu resources.

Cure: Use faster computer, optimize Windows

Disable the tool path preview.

4: Kernel speed to slow
Cure: Raise the kernel speed

See attached images for more help.

More information about your machine will help diagnose this issue.

Jeff...

[woody8750]

I went back to motor tuning and turned down the accel on all of the axises. This appears to have resolved the problem? I have been able to run through a 25,000+ line program and return to zero on my dial indicator. I'm running Gecko 201 driven stepper motors with ball screws and timing belt connections so I don't think backlash should be an issue(yet). I did disable the tool path preview but this didn't seem to make a noticeable difference, so I enabled it back on. I've got a lot to learn about this stuff and you guy's are a real asset!!! Thanks for the prompt help!