I'm in the process of upgrading an old cnc lathe with all new electronics. Everything was fine when I first installed and wired everything up. I'm still in the process of wiring other small things but for whatever reason whenever I turn the power on my stepper motors decide to start moving on their own. They keep moving until I jog either motor then they hold. If I keep jogging the axis, it sometimes goes smooth in one direction but the other direction is very rough. Does this sound like a wiring issue or possibly a weird setting in mach3. My setup is just ebay nema 23 motors, c10 breakout board, gecko g251x and 24v power supply for the drivers. Also if I was to turn the power on the electronics without going into the mach3 software then the motors hold without moving at all.

I would suspect a wiring issue, namely noise. Check you have shielded cables and they are correctly grounded.

What is the correct way to ground the shielded cables? I just about ran out of patience on this thing. The x and z both move fine in one direction but are all choppy in the opposite direction. I even changed the bob to see and I still have the issue.  I've been struggling with this issue for a couple weeks now and I can't even use this machine.

The power supplies I'm using for my machine are 24v and a 5v. The ac power goes to the 24v psu then from there goes to the 5v psu. The 24v is used for the motor drives and the 5v feeds the bob. Can that be causing interference? Should I run a separate ac line to each psu? I'm just running out of ideas here.

What is the correct way to ground the shielded cables?

There is no absolute 'correct way' but a method that works is...

Create a single point (star) earth tag at your controller end. This star should be connected to your incoming Earth. The shields of all screened cables should be connected to this star and those shields left unconnected at their other end. Any other components Earths should also be connected to this star point.
Do not create any Earth loops or GND loops - single point connection is the way to go.

Tweakie.

Today I grounded all my shielded wires from the motors and from the drives to the bob. I turned the machine on and the motors now hold steady and don't move on their own which is great! However I still have an issue. The x motor will move back and forth perfectly, the z motor will move back and forth perfectly. I can move the z motor away from the chuck while moving the x motor in either direction perfectly. When I move the z motor towards the chuck and move the x+(away from part) it starts to squeal and twitch out but will work perfectly if I go x-.  I checked every single wire and retightened all my connections to the board,drivers. What am I missing? Why is it perfect only until I move z- and x+ at the same time?

Now could this be an issue? According to the manual for my c10 bob, it says that the jumper for the "com" should be set to +5v instead of ground if using a geckodrive which I am. But I believe in the gecko 251x manual it uses a common ground. Who do I believe haha? Currently the jumper is set to ground

Is your power supply have enough power for both stepper at the same time?

Jeff

I've checked the power supply and it appears to being able to handle both at the same time. I Just find it very odd that everything works great , including moving the motors separately and also together with no issues until I try going z- and x+ at the same time. I took the buffers/optoisolators off my c10 bob today since they do sell replacements online but I'm not too sure if there is any way of testing them to rule them out before I buy. This is really stressing me out haha I can't believe it