I need some professional help (or so they tell me), I've read as much as I can about the issue but just keep going around in circles. I am running Mach 3 on a Vista machine controlling a G540 running steppers on an X2 mini mill, I HAD everything running smoothly until I tried to add a 4th axis (a lathe head with a 4th stepper) it worked ok except that it would randomly miss steps on the A axis and I couldn't figure out why. I had other projects piling up so I took off the A axis and set it up like I had it but now it's missing steps on the Y axis??? There is no binding in the ballscrew or ways, the X and as far as I can tell the Z axis are ok,  I reloaded Mach and tried to set everything as close to original as I had it but that didn't help, it will do it running known good Gcode or even jogging it with the Xbox controller,  seems like a program problem but if I knew what I was talking about I would be able to fix it myself?? any help would be greatly appreciated, Thanks Jim

Can you hear the motors stalling?
Hood

No stalling heard even if i push on the handle to help it along I can still watch the DRO count up/down with no movement or signs /sounds that it is trying to move the Y.

Ok so Y is not moving at all? Sounds like you have the wrong pins assigned for it in Motor Setup part of Ports and Pins, or maybe have not set the port there for Step AND Dir pins.
Hood

The Y moves but randomly misses steps/stops moving, when it does that I can watch the DRO move up/down but there are no signs the stepper is trying to move so I don't think it's mechanical, It was working fine and I was running Gcode to engrave key chain blanks but then I tried to add the 4th axis, after that I started to get the missed steps.

Ok can you attach your xml and I will look at your config and see if there is an issue.
You will find the xml in the main Mach3 folder and it will have the name of the profile you are using, so for example if you are using the Mach3Mill profile it will be a file called Mach3Mill.xml

You may need to copy it and rename before the forum will accept as it will only accept a file name once. To attach to the forum use the additional options button on the reply page.
Hood

My power supply and steppers are probably overkill for the machine and the G540 is said to be bulletproof, I changed the accel and velocity settings but that didn't help. I'm not looking for someone to fix it for me just someone to guide me along or at least point me in the right direction.

Xml looks ok so I would think your issues are hardware, especially as the DRO moves, that means Mach is sending the pulses to the port. Only thing that could potentially be wrong in your setup is the pin numbers are set wrong for the Y axis but thats unlikely if you do get movement at times. One thing I have heard on occasions is people need a wider pulse for the G540, some do, some dont and some even need Sherline mode, so may be worth a try.

Check all wiring is secure and maybe try swapping the Y onto another of the drives (remembering to tell Mach which pins)
Hood

I swapped the X and Y axis at the G540 and the miss followed meaning the problem is in the 540 , the computer or the cable (as you said, hardware). I thought I had the pulses set wider then that so I set the step and dir pulse to 3 and it seemed to be OK but I will have to wait until the weekend to test it some more, I remember having to increase them to get smooth movement when I originally set everything up and I also remember changing them when I was messing with the 4th axis, sure hope that's it. I also tried the Sherline mode but it just growled at me for doing it. Thanks for your help I'll keep you posted.

Hopefully that is it, fingers crossed
Hood