[adi961]

Hey together,
I am currently building my CNC machine based on the shapeoko 2 kit, but am experiencing some issues.

My current setup is:
3 axes with 4 nema23 stepper motors
3 DQ860MA drivers (from Wantai Motors)
I tried linuxCNC and now I am using Mach3.

Every time when I am doing a deep cut witch multiple passes, the machine gets out of alignment. When the end mill passes over the same part, it moved slightly to one side.
I realised that the misalignment is always diagonal on both axes, so i don´t think I am loosing steps randomly. I also don´t think that its the frame of the machine, because the misalignment happens over time.
http://www.cnczone.com/forums/attach...d=344696&stc=1
The cut on the picture should be straight down, but as you can see the cut is more like a ramp.

I got the same problem witch linuxCNC and Mach3.

Has anyone experienced a similar problem or has an idea to fix it.

Thanks in advance,
best regards, Adrian

[James Newton]

Check for mechanical binding by manually moving the axis at different positions. Measure the torque required to turn the lead screw (assuming that's what's driving it). If it changes significantly or is much higher on one axis, look deeper into the mechanics. You can also just run air jobs for hours to wear in the machine.

If it gets worse over time, check the temperature of the stepper motors... if they are getting hot enough to burn, add heatsinks. Seriously... people will poo poo this suggestion, but I've seen it make a huge difference... of course, it only applies when the heat corresponds to the problem. e.g. when cold motors are fine but as they get hot, they lose power.

Swap drivers between axis to see if the problem follows a driver.

Try moving the step and direction wires from the PC into the drivers away from any possible sources of noise. Wrap them in tin foil and ground it. Use thicker, shielded wire.

Buy better drivers, bigger motors.