Kit's Machine

[Neale]

When I first built my machine, using proximity switches, I had similar problems and immediately worried about noise issues. Turned out to be a completely different issue - lack of hysteresis in the switches. All the reading I had done suggested that there was significant hysteresis - having approached its trigger, the switch would operate but it would then need to be moved a measurable distance away before releasing. Definitely not the case with these cheap Chinese switches - hair-trigger stuff around the switching point. So, Z axis homes, Mach3 sets it back from homing to limit switch mode, and Y starts moving. The vibration was enough to trigger the Z (now limit) switch and everything stopped. Sometimes homing would work and the machine would trip when I started moving away from home position at the start of a cut. The fix was simple - the Mach3 setting that moves the axis just off the home position once homing is complete.

I'm just glad that I didn't need to go hunting around with a 'scope, which I suspect throws up more worrying measurements than you really want to deal with!

[Kitwn]

I've fitted the mains filter and installed it in the machine. I can now power the whole beast including the controlling PC running LinuxCNC, controller with BOB, stepper controllers and motor supplies, water pump and VFD from a single mains socket. I haven't yet got the scope out to see how much noise is still visible on the controller wiring but at least it works!

The filter is a standard, two stage filter from RS which I linked to earlier. I've also added a ferrite ring to the earth wire since this is a probable route for high frequency noise to escape.