Hi all,

This is my first post here - thought that since I lived in the UK I should support this one rather than some overseas ones .

I'm part way through my second cnc router build (I will post this at some point for interest) and thought I'd take the opportunity to resolve an issue with one of the stepper motors. The x axis was basically glitching quite frequently during traversing. My set up is:
Driver board System3 all in one - Roy DIYCNC
3Nm steppers x & y - ArcEuro
1.8Nm stepper z - (sorry,can't remember where from)
Power supply 350W 33V - Roy DIYCNC
Desktop PC with parallel port.

After doing extensive testing (step width, pulse width, ramp rates, swapping motors, axes etc. different step rates etc.) I concluded that it was the X axis driver circuit. The charge pump signal had also stopped working some time ago, and needed to be overriden to get the board going again. I wrote to Roy and he suggested sending the board back to replace the allegro chip. It is now back with me, as a complete new board , and bench testing shows that now all 3 axis are glitching!

I started to wonder about the data from the PC so have borrowed an oscilloscope and checked the pulses out of the end of the parallel cable (i.e not connected to the driver board). During a steady traverse (me pressing the left arrow for example) they show square regular spaced pulses (I'm triggering off the pulse to make it easier to read), but quite often the spacing of the next pulse varies considerably. This means that the PC is the source of the glitching.

I've only discovered this tonight, so have alot of things to check, but though I'd ask for ideas on this one?

The PC had a fresh XP install, with only Mach3, a CAD program, Vectric Cut2D, and AVG (virus checker). It is on the internet, but it still glitches even it is not. I've not checked all the processes which are running in the background, but the Mach3 diagnostic screen shows 'Int time' around 10. Sorry this info is a bit sketchy, I need to do more on this.

I'm sure someone else must have had this issue. Reason for pursuing it is because complex jobs seemed to be loosing steps in the X direction and the 2 issues seemed linked.

p.s. Also have an extra parallel port in the PCI slot which I've not used yet (was intended for further inputs etc). I briefly had a play with this to see if I could run it all from here in case the main parallel port was broken, but could not get motion. Didn't have time to investigate tonight. Thoughts on trying this route welcome.

Thanks
Barry