[acelcobra]

Hello, I'm fairly new to the CNC world, but despite being self-taught through trial and/by error, I am getting the hang of it without major problems. However, I do have one consistent "glitch" that has plagued me since the beginning. When milling, 3 axis or 2, my x axis will shift negative by one "step over" (whatever I set as my step-over setting when writing the g-code) when dropping to the next z level pass. If I'm running a 1\8 in bit at a depth of .0625 and a step over of .0313, it cuts great until it starts the next pass. In this example, it will be negative .0313 on the x axis as it cuts. If I use a step over of .1, the shift will be negative .1.
I have gotten to where I just "hold feed" and reset my zero coordinates before each pass (which leaves me babysitting the machine constantly). I have tried changing the acceleration on the motor tuning tab, but it doesn't seem to help. All of the screws, nuts, bolts, guides, and motors have been tightened and have no play. Also I have no binding on the drives. This only happens on the x axis. It does also occur after a manual tool change.....so I reset zero coordinates at that point and "run from here" each time.
The machine is a cheap eBay CNC 6040DJ (or TJ, DT, TZ or something....don't quite remember). I am using BobCAD as my CAD program and GCode writer. Registered Mach3 for milling. Using a Dell computer with 32 bit Windows 7 installed. The CNC is the only thing run on this computer. I do all my CAD stuff on a separate computer and transfer the files over. (though, when I used them off the same computer, I would still get the axis shift).
Any help is appreciated.....I'm getting near to the "BFH" stage of fixing this.
Thanx
C

[Welder2022]

Post the code you're running and I'll have a look.

[awerby]

It sounds like the backlash compensation in Mach3 is overcompensating. Try turning it off, measure your backlash, and reintroduce it cautiously.