Stepper motor help...STM5776

[paulus.v]

First check if the vibration is not mechanical.

Second and easiest to do, I would swap the X and Y motor plugs from the drives, the 6 wire connector, assuming two motors are identical and powered by the same psu. Now when you jog the X axis, the Y will be moving and vice versa. If the other axis is vibrating then the drive is faulty. NEVER unplug the motor and power plug from the drives before turning off the power!!
I cannot see if there is a plug at the motor end. If it has a plug, you could easily swap the motors as John said and this way you find if it's the stepper, cable or drive faulty.

Third but most likely, I would check/replace the motor cable, if your Y axis cable is the one that is moving inside a cable chain.

The stepper motor is the last thing I would suspect to fail.

[SweetAs]

Ok guys, I have just swapped the 6 cable plugs over and its the same issue. The x is running as smooth as and the Y jolts when it moves and stops so violently that the machine visibly shakes.

I'm going to check the connections at the motor end on the Y in a second, the machine will need to be disconnected and pulled out which is why I haven't done it just yet.

Any tips on checking the wiring at the stepper?

The Y wiring is static, the motor is fixed at the end of the axis and doesn't move so unless something has come loose I wouldn't have thought that the wire would have failed but who knows!

[paulus.v]

Have you checked it mechanically? Check for any play of the motor shaft first and then the pulleys, belt, rails, etc.

edit: Could be the stepper rotor rubbing against the stator... Try turning the motor by hand and see if it is turning smooth.

[SweetAs]

Hi Paulus,

Yes all checked manually. I've just taken the belt off again and checked the following..

No discernable play in the shaft of the stepper motor.
Pulley grub screw is tight
Moved the Y axis back and forth with the pulley to stepper belt off, everything felt smooth, checked the bearings as best I could but they look fine. They are 6001Z and the shaft is supported twice, either side of the belt pulley at both ends if that makes sense.
Ill take the main Y belts off in a second and see how the axis moves without any resistance at all.
Couplings adjacent to the motor seem fine, no play in them.

Here is a pic of the set up....

[paulus.v]

How is the cable connected at the motor end? Is there a connector? Or are the wires soldered? Does the motor have 4 or 8 wires? If you disconnect it you can check the impedance of each winding with a multimeter on ohm reading and see if you get same values on each pair. Then connect with another cable or 2 cables with 2 wires, anything you may have around.

[SweetAs]

By the looks of it at the rear of the motor there is a black block connected to it which has a single black sheathed cable going through the panelling and straight down to the controller unit.

The wire has 4 strands, black, blue, green/yellow and brown. Black and brown are linked together in the controller, green/yellow and blue are on their own. I've attached a picture of the controller unit so you can see how they enter.

Can I just take the connecter block off and check or does it need to be at the stepper end?

[SweetAs]

Just as a heads up.

Took the Y axis belts off.

The Y axis free wheeled and had no resistance
The shafts did not free wheel however they moved smoothly
No movement in any of the bearings from what I could see

[paulus.v]

Those are not the wires going to the motor but the signal wires going to the drives. The motor wires are connected to the black drives from your first post picture (A+; A-; B+; B-)