Extruder stepper vibrating after upgrades and sitting

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Extruder stepper vibrating after upgrades and sitting

Postby kf4zht » 2017-Mar-Thu-21-Mar

I have an older printrbot simple, with a rev d board. Got it in trade a while back and used it a lot for a year or so but wanted more space. Did an upgrade to significantly increase print size, move to gt2 belts, etc. While I was at it I ordered the aluminum extruder.

Then it sat, new baby, changes at work, etc. Now I am getting back to it. Got the bed done, glass cut. Everything works great except the extruder motor. When you jog it it just vibrates but doesn't turn. Connected the z motor to the extruder header and it does the same. Extruder motor on z header works fine.

I extended the cable for y, but no extruder wiring. I did change the steps value for x and y, and the limits but the extruder ones all look stock.

I've tried unified v2 and v3 with no luck. Anything else to try? Did I fry the driver on the board?

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Extruder stepper vibrating after upgrades and sitting

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Re: Extruder stepper vibrating after upgrades and sitting

Postby RetireeJay » 2017-Mar-Thu-21-Mar

It certainly sounds like a hardware problem on the board. The first thing to try is to change the potentiometer setting for the motor current going to the motor. Perhaps the potentiometer is actually in the right place, but the contact is weak and needs to be refreshed by turning it back and forth just a bit. Or perhaps you bumped it and set it down low unintentionally so it needs to be raised.

If this doesn't fix it, and you are at all handy with electronics, you may be able to do some troubleshooting.

Stepper motors have two independent coils. To explain the action, if one were using 1X steps, then one might see full current going to Coil A in the positive direction, followed by full current going to Coil B in the positive direction, then A in the negative direction, then B in the negative direction, then back to A in the positive direction and so on. (To get rotation in the opposite direction, it's like A+, B-, A-, B+, A+). The Printrboard uses stepper driver chips that actually modulate the transfers from current in A to current in B according to 16 "microsteps". The stepper chip receives "enable", "direction", and "step" commands from the Atmel - but those signals seem to be OK, or you wouldn't be getting any life at all from the motor.

But all the work of controlling the current to each coil is done by a single chip per motor. There are a few resistors and capacitors that help make the system work. If, for some reason, there is never any current being sent to Coil A (or to Coil B) then the motor will simply buzz and move in small random increments or not at all. So you might have a broken lead on the circuit board conveying motor current from the chip to the header. Or you might have a broken lead or broken resistor - the "current sensing" resistors would be the first place I'd look. You can find the schematic of the board at reprap.org/wiki/printrboard.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
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Re: Extruder stepper vibrating after upgrades and sitting

Postby Mooselake » 2017-Mar-Fri-07-Mar

Did you check the steps/mm for E?

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Re: Extruder stepper vibrating after upgrades and sitting

Postby kf4zht » 2017-Mar-Fri-12-Mar

Thanks, kind of what I figured. I did adjust the pot, it just made the vibration more of less violent.

Steps are set to 94.5 iirc, which was stock. I can verify when I get home but I did check to make sure that lined up correctly

I will pull the board off and start testing components. At least I have 3 more channels to compare to. Hopefully a multimeter is sufficient for testing, I got rid of my oscope a while back. Also may be my first time doing smd work in a while.

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Re: Extruder stepper vibrating after upgrades and sitting

Postby kf4zht » 2017-Mar-Fri-21-Mar

Got the board unwired, issue was simpler than expected. At some point a splatter of solder ended up on the chip for the extruder. Little cleanup and it's working great again.

Just need to get everything calibrated and ill be back printing.

Thanks for all the help!

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