Extruder Runs in Reverse... but only sometimes

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Extruder Runs in Reverse... but only sometimes

Postby DaveG » 2015-Feb-Sat-14-Feb

Not sure if this is software or hardware related but figured this was as good a place to post as any.

My new Metal Simple has been running great up til now. Everything moving in the right direction. Now, sometimes, but not all the time, at the beginning of the print the extruder will run in reverse, not stop, retracting the filament until I hit the Kill Print command. The printer first runs through the auto leaving sequence without a problem, moves to the center of the bed and then the extruder goes into reverse. At first I though it might be a G-code issue but I can re-run the exact same code a second time and the error doesn't repeat.

Could this be a sign of a defective Printer Board?

Any help would be appreciated!
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Extruder Runs in Reverse... but only sometimes

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Re: Extruder Runs in Reverse... but only sometimes

Postby RetireeJay » 2015-Feb-Sat-17-Feb

If you try to Extrude some filament using manual control, or try to Retract, does it always do what you tell it to do?

At a hardware level, the chips that drive the stepper motors have three control signals coming from the CPU chip:
1) Enable
2) Direction
3) Step

In your case, clearly the Enable and Step signals are getting through. But sometimes the Direction signal is not correct. The Direction signal is wired directly to the CPU chip with no other components in between. (If you are into electronics, you can find documentation and schematics on the RepRap wiki site, along with a link to more complete schematic and board documentation in Eagle format on Github.)

So, how could this fail?
(A) The stepper chip itself could be bad.
(B) The Direction connection between the CPU chip and the stepper chip could be bad
(C) The firmware in the CPU chip could be bad.

Re-flashing your firmware is not terribly difficult, and it's free. That would eliminate possibility (C)
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Re: Extruder Runs in Reverse... but only sometimes

Postby evanalmighty » 2015-Feb-Sat-22-Feb

I have this same issue on one of my printers running on Ramps 1.4 and stock Marlin. It used to happen at the beginning of prints, but lately it happens midway into the prints. It used to be random and sporadic, but now it happens with every print. I replaced the stepper driver but the problem did not go away. I'll try to load the firmware again. If that doesn't work I'll try replacing the board.
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Re: Extruder Runs in Reverse... but only sometimes

Postby DaveG » 2015-Feb-Sun-10-Feb

Thanks for the detailed answers guys! Jay, yes, manual commands sent to the extruder always work correctly. Evan, at least I know I'm not alone! The anomaly has only occurred a couple of times. If it continues or gets worse I'll try reloading the firmware, if that doesn't work, I'll contact PB for a new board. It's a brand new machine, still under warranty.
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