Stepper motor intermitent stops

[rcs1010]

Hi

I have Vortec Router and one of the stepper motor after couples of minutes working stops just for a second a keeps moving, I can turn the router off wait some time and cut some things then happened again. I though it was the motor that went bad and I got a new one but still does the same thing, I took the motor out and it does the same, SO it is no the gantry or anything attach to it. I do not know what can cause this.

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[awerby]

Try switching the leads from the motor that's misbehaving to another one that works okay. (Turn off the power and let the caps drain first, before disconnecting anything.) If the problem moves to the other motor, then the motor's not at fault. Then see if it's the cable that's causing the problem by switching it with a different one. If it's not the cable or the motor, then it's either a bad driver or faulty wiring.

[CoAMarcus]

Andrew is correct. The simplest way to troubleshoot problems like this is to try to isolate the problem. I typically recommend users swap drives between axes entirely (move your Y axis drive to the X axis, and your X axis drive to your Y axis); if the problem follows the drive then we know it is a drive issue. If the problem stays on a single axis regardless of what drive is connected it can be a few different things:

1.) A loose connection on the motor or motor cable. I just recently had this problem on a test fixture and narrowed it down to a frayed wire at the base of the motor from years of being moved around.
2.) A problem with your STEP and DIRECTION line going into that axis' drive. Are your connections shielded? If so, are they a twisted pair? If they are, make sure that STEP and DIR are not twisted around each other. It would most likely not cause the kind of problem you are experiencing but it can manifest as ignored direction changes, phantom missed steps, and so on.
3.) Your power supply is going south. This will likely affect all axes but it can cause a problem on a single axis if it is near its designed torque limit. You can test this by slowing your speed down to about 50% and see if the problem continues. Stepper motors are constant power motors, and power = speed x torque, so lowering the top end speed is a quick way of getting more torque out of your motor. It isn't exactly linear, but it works as a quick diagnostic.

Do you have an oscilloscope you can use to measure the STEP pulses going into the drive? You can monitor the pulses and see if there are any being sent to the drive while the motor is acting up.