Extruder Motor Only Goes One Step?

So I just finished building my MPCNC yay!!

But when testing I found a problem doh!!

I printed the pieces out myself but the hardware/electronics/extruder were all purchased from vicious1.

Without any filament in the extruder it seems to only move a single step and then back again when attempting to extrude/retract. It won’t go continuously in either direction. I get the same result with the hotend cold or hot, I tested both wondering if it was Marlin’s underheat protection but that doesn’t seem to be the case. I used a multimeter on the extruder motor wires to make sure the motor coils were wired in pairs correctly and that does seem to be the case.

All the other axis/motors move normally. This is the second ramps based printer I have built so I’m not unfamiliar with the basic setup but I haven’t seen this problem before.

I’m not sure what else to check.

I just realized that maybe my problem is that the extruder stepper driver might not be set to the right voltage. I setup the electronics board months before the rest of the machine was ready and I may have missed that step. What is the recommended voltage for the motor that comes with the mk8?

I just tried a range of voltages between 0.4 and 1.0 and it still just tick tocks back and forth.

Do you have any endstops wired?

No end stops are wired but I don’t see how that would effect the extruder motor. That should only affect the xyz axis.

Do you have the resistor plugged in or the thermistor?

There is a safe extrude temp set in the firmware that needs to be exceeded before it will move, 170C.

Thermistor is currently plugged in and reports expected temperatures. Attempted to extrude at 190C and I get the same result.

I just swapped the z and extruder stepper drivers around. The extruder now runs properly and… to my surprise the z axis too. So I guess I have a solution. The voltages of both are about 0.6v so I’m not sure what the difference really is but I’ll take it.

And the next time I turned it on the z axis acted all wonky. It appears that driver is just no good. The likely postal strike in Canada is going to make replacing it a pain in the ass.