Extruder stepper clicking in place

Hi,
I'm finishing up a build but ran into a problem: the stepper motor on the extruder just clicks in place (goes back and forth in small jerks) rather than extruding. Using a different motor works. Trouble is the wiring color (black, green, red, blue) on this motor is different from the ones I usually use (blue, yellow, green, red), so I thought it might be wired differently, but a multimeter shows about the same resistances across the non-working and working motors. To top it off, 2 of these identical motors don't work. I can't easily replace them with the working motor due to the extruder housing dimensions (working motor is too long).

Any ideas if these motors can be fixed? It will be monumentally easier to finish this project if I can get them to work. E.g. maybe the wiring check I performed is insufficient? Or should I give up on the motors and redesign the whole gantry/hit ebay for a working version of same size?

Update: different permutations of wires don't seem to help: it either clicks in place or doesn't move. So it really doesn't look like wiring is the problem.

Edited 1 time(s). Last edit at 04/03/2016 12:58AM by anvoice.

It sounds to me that you have an ungeared extruder with an underpowered motor. This is a common problem. Short of installing the longer, more powerful motor, the best you can do is turn the extruder motor current up to about 90% of the rated current for that motor, if your drivers can take that.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

In my experience a clicking extruder motor, where it extrudes in some areas of the bed and just clicks in others without extruding is more a sign of an uneven bed. The motor is clicking because it cant extrude any filament because the nozzle is too close to the bed. Try increasing your head gap by 0.1 or 2 to see if this makes any difference. The only other clicking I've had from a motor is when one of the phases is not present, e.g a broken wire, but then this is consistent across the whole bed not just in some areas. Alternatively it could be a fault in the umbilical to the print head and when it is in a certain position a damaged part of a wire goes open circuit and then closes as the cable bends in a different direction. Some alternative thoughts for you

Clarification: it's clicking in place without any filament/force on it, so bed is not the problem, neither is it being underpowered (at least not yet). Turning up the current produces no visible change.

Upon closer inspection, the motor does occasionally move somewhere, but then just continues moving in jerks. Bad wiring after all? But then do I have to check all 24 permutations? Also, the shaft moves easily by hand even when the motor should be powered, e.g. when it's doing its stutter I can lead it clockwise or counterclockwise no problem.

Edited 2 time(s). Last edit at 04/03/2016 06:47PM by anvoice.

Sounds like your motor wire pairs are incorrect. Use a multi meter on continuity test to determine the pairs of wires, not the relative color. HTH

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Just an Artist, Musician, Designer, Programmer, Maker

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Yes, could be bad wiring. I had something similar when one of the wires to my extruder stepper broke.

Try switching the extruder and (say) X axis connections at the RAMPS board. Now tell your printer to move the X axis. Does the extruder turn? (NB: If you home the "X axis", you'll need to hit the X-axis endstop manually. Also try "extruding" (again, beware that you could crash into X axis the endstops).

This should at least tell you whether the problem is in the motor+wiring or whether it's a firmware/hardware/current problem on the RAMPS board.

If you identify a motor/wiring issue, then a multimeter across the pairs of wires should tell you which wire is broken. You should find that pins 1&2 are connected together (a few ohms resistance), and pins 3 & 4 are connected.

Yes, the problem is the motor (2 identical ones): using a different one works.

I tried different permutations of wires to no avail. It either stutters, or doesn't move at all. Continuity tells me wiring should be fine (the pairs are where they should be).

For now I hacked the extruder to fit the bigger motor. Works but isn't aesthetically pleasing at all.