Stepper extruder - help please!

Hi All,

I'm new to all this, so I hope I'm posting in the right place. I've had bits in boxes for years, and am finally getting round to putting it all together. I'm running MakerBot Gen3 electronics, a darwin, and a pinch wheel stepper driven extruer (which is where my problem lies).

For context, my setup is…
RepRap darwin
Generation 3 electronics (Motherboard v1.2, Stepper Driver v2.3, Extruder Controller v2.2)
Pinch wheel extruder (with Nema 17 stepper motor)
ReplicatorG 0024 software (set to Cupcake CNC)

So I've got all 3 axes working, and the input & feedback for the extruder temperature seem to work fine.

My problem is with the control of the stepper. It is getting an input, and attempting to turn, but doing so very slowly (almost as if the coils are working against each other, although I've checked the wiring to make sure this is not the case).

The software & firmware setup is as follows…

ReplicatorG set to cupcake CNC (I can't work out how to change it to anything else, so if someone could point me in the right direction to change it to reprap that would be great).

Latest firmware on the motherboard (v2.4)

Firmware v2.3 on the extruder board (which says it is the one for a stepper).

I haven't changed any other parameters in the machine xml or anything as according to MakerBot guidance, that should all be done by the v2.3 firmware.

I'd really appreciate it if people could suggest things to try so I can get it working. (Let me know if I need to give any more information for people to assess the situation).

Thanks in advance

Sam Saunders

You might be better off posting this in one of the electronics support forums. And I'm a bit new to this to be able to help you much. However, have you tried demounting the extruder stepper and seeing if it works correctly without load? If not, it would imply a problem with the wiring; either it's not getting enough current (I don't know if Gen3 has trim pots to change the current), or there is a problem with the wires to the stepper. You'll probably need a multimeter to check these. If it is working properly, then the stepper motor may not have enough torque to turn the extruder - could be something is catching, or perhaps even the temperature is not high enough to extrude - can you push it through by hand? Hope that helps.