[sjubs]

Purchased a 6040z Chinese CNC in 2016 to teach myself the ropes of baisc CNC craft. Two years later, I feel much more confident and skilled but the learning experience took its toll on Y stepper with the Z starting to follow. I could go with the same size but was wondering if I could stretch its legs a bit and go slightly more powerful steppers without having to perform significant upgrades to the controller.

Below are the specs for what I currently have and what I would like to replace. However, I'm still a newbie when talking parts so I would like some guidance. I am willing to gut the controller if needed but hoping to keep the repair costs down so I can continue to learn.

Current:

FRAME: 57BYGH76/4A1.8N.m (aka Nema23)
LENGTH: 76 mm
A/PHASE: 3A
TORQUE: 1.89N.m (270 oz-in)
LEADS: 4

.

Proposed:

FRAME: Nema23
Length: 115 mm
A/PHASE: 3A
TORQUE: 425 oz-in

I can provide other specs from the controller if required

[ger21]

Stepper motors almost never fail, so I'm curious what is wrong with yours? It may not be the steppers at all.

Regarding larger motors. Without changing anything else, moving to larger motors can often reduce performance. But it's hard to say without knowing all the specs of your machine.
Stepper motors rated torque is holding torque, when they are not spinning. As Rpm increases, torque decreases. With larger motors, the torque decreases faster. SO it's possible the smaller motors will have more torque at higher rpm than the larger ones.

[sjubs]

The problem started when I was making the third copy of a pattern in 3/4 wood. The Y axis performed a significant deviation from the normal profile path and crashed the head into a metal hold down clamp. I was on the back side of the CNC vacuuming chips so it took me a couple of seconds before I could initiate the emergency shut down button. All this time, the Y axis was screaming. Since then, the Y axis has two issues.

First, it follows the g-code path when under no load but the minute the cutter enters the material, the y axis lacks torque to push it through the material. It is also noted that I can now spin the Y axis adjustment knob with the unit powered. There remains < 10% resistance whereas I could not move them at all prior to the event.

The second problem occurs when I use the keyboard to shuttle the spindle across the y axis. Sometimes it moves correctly and sometimes it moves in the opposite direction. Results are totally random and can change by simply releasing the keyboard and tapping it again..I validated and re-seated all of the wiring connections with no improvement. Then I read where NEMA23 steppers can lose their permanent magnetism if too much power is drawn. I swapped Y with X and re-tested. The problem followed the stepper.

I am looking for a well written diagnostic process, Can anyone point me to some helpful information

[ger21]

Then I read where NEMA23 steppers can lose their permanent magnetism if too much power is drawn.

I've never heard ofthis. Unless you have the drives set to deliver more current than the drives are rated for, you won't damage the steppers.

You're problem is most likely either mechanical, or electrical. But not likely to be the motors.

Simply swap the X and Y axis motors, and see if the issue follows the motor. If not, then it's not the motor.

If not the motor, swap the drives.

[Gojira]

Bit late of a reply, but I had a similar issue not long ago.. Turned out to be a bad connection on one of the wires to the stepper motor plug... sometimes It was connected and all would be fine, other times one wire was coming out and the stepper would go in the wrong direction. Not sure if its the same issue for you.