Random Z-Axis plunge

[Jonathan]

@Jonathan, could you tell me what backlash is, and what causes it/what to look for?

Backlash is lost motion when the motor driving an axis changes direction. For the majority of machines there is some clearance between the nut (ball-nut or trapezoidal) and the screw, so when the screw changes direction the nut wont move until it has moved the distance of this clearance. Better explanation here:

http://www.machinetoolhelp.com/Repai..._backlash.html

If backlash is significant you'll for instance see it if you cut out a circle - at the limits of travel (so 4 points) there would be a slight blip. However on a ballscrew driven machine generally the backlash is so small (<0.05mm) that unless you're cutting metals it wont be noticeboard.

Also, do I have to use the control program that came with the router, or can I use anything (like LinuxCNC) to control the machine? Is there a machine profile or something like that to set up the control program to work with the router? I don't really like NCStudio, and I think it's pretty buggy.

It looks like NCStudio uses a PCI card to control the machine:

http://www.erel-cnc.de/html-uk-cnc/software-uk.html

So assuming that's what your machine uses, unless there are drivers for it for Mach3/LinuxCNC, which seems unlikely, I doubt you can use any other software. That's unless you remove the card and change to a parallel port system, but that's downgrading if anything. The PCI card should be better.