View Full Version : Looking for simple validation/refutation:

Alan Reilly
10-14-2013, 11:15 AM
I purchased a used Helix about a year ago, and it has worked perfectly until yesterday.

Halfway thru a small job, it stopped and displayed:
It would not rehome. I powered off, then on and Y homed, then X started moving very jerkily towards the home position then it stopped and again displayed:

After reading thru the manual, I thoroughly cleaned and lubricated the X axis rail. The lens assemble moves smoothly along the rail, with only a very slight "cogging" feel as you move the lens assembly along the X axis. I re-assembled the cover and powered up. Again, Y homed, then X started moving very jerkily towards the home position then it stopped and again displayed:

I powered down again, then powered on and using 2 fingers tried to stop Y axis from homing. The strength of the Y axis motor was very strong against my fingers, but it did error out with the display:

I repeated this process but used my fingers to stop the lens assembly from moving to the X axis home position. The strength of the X axis movement was VERY weak, requiring only a light touch to immediately stop the X axis from homing and giving the "X/Y DISABLED: X" error message.

I believe this is a simple case of the X axis motor being bad. Do you agree, or could it be something else?

Kev Williams
10-14-2013, 1:15 PM
The motor could be bad, but your description "the X started moving very jerkily" is an indication you MIGHT have an electric issue. I've had a few steppers go bad, usually they just start skipping or losing places, which seems to be a "lost horsepower" issue from simply wearing out. I recently replaced the X stepper on a friends Vision engraver, it was nearly seized up. But in my 32 years of stepper-controlled machines, I've found when they start jerking, it's due to the stepper not knowing what to do because it's getting conflicting information-- in other words, either a connection is bad or there's some issue with the XY driver board. Because you also stated the rail "moved smoothly" after lubing the rail, that may rule out a seized stepper. I could barely move the spindle head on the Vision with the bad stepper.

Best way to troubleshoot this is to swap the stepper motors, assuming they're identical. If the X repeats the problem, it's not the stepper motor. If the Y repeats the problem, it IS the stepper--

Alan Reilly
10-14-2013, 1:23 PM
Would the fact that my machine has DC servo's make any difference in your reply?

Bill Cunningham
10-14-2013, 1:40 PM
Not sure if that laser is using brushes in the x-motor or not. If a brush is worn out, it would act that way.. The brushes can't be replaced, and the motor is scrap.. You may also smell a burnt smell around the motor. I keep a spare X motor on hand, just in case. I've gone through 3 in ten years.. I keep a spare, because Epilog stopped using DXL overnight, and now ships 3 day UPS. 3 days is about 2 days too long to be down. This factor alone may decide what laser I replace my current one with probably sometime next year.

Kev Williams
10-14-2013, 1:43 PM
I've never had the pleasure of servo motors, but my reply as a whole still seems plausible, especially the swapping motors part to troubleshoot-

Chuck Stone
10-14-2013, 4:13 PM
that 'cogging feel' might indicate it is slipping a notch on a belt, too.
Are the belts tight enough?