I'm running LinuxCNC on one of the Chinese CNC3040 machines (I know, but it's what I could afford for now). If I try to mill out a pocket with multiple passes, the layer shifts about 1-2 mm (towards 0 on the X and Y axis) with each pass. I'm cutting acetal with a two flute .125" end mill at a low feed rate (200mm/min) and only .5mm per pass.
The weird thing is that if I run a file to cut openings in a plate (single pass) the cutouts are in the correct places. In other words, it doesn't look like it's missing steps when cutting a single pass?
The diagram shown in the GUI looks fine. Each "version" of the shifted cutout has the correct dimensions, so again it doesn't seem like it's missing steps.
I'm very new to running a machine like this, and I don't know where to start troubleshooting. I would greatly appreciate any suggestions anyone might have.
Re: A problem with designs shifting with each layer
Could be you're losing one step each time those axes reverse. I'd had that issue with a cheap driver board I had years ago. I ended up just trashing the board, as I found other issues with it.