First real “failed” print. The extruder started skipping steps. I noted a potentially loose wire where the stepper plugs into the board. Also remembered people saying steppers loose steps if hot. So I tightened the wire and crazy glued a couple heatsinks to the motor.
Next print worked!
I wonder how well that glue conducts heat. If it is a poor conductor then it will capture heat inside the motor and prevent any of the previous airflow from reaching it.
Good point - I had heard elsewhere of people crazy gluing heatsinks to the chips on the Polulu drivers, so I figured it should work here.
It makes a lot more sense to make sure your motor current is set properly than to try to band-aid the situation by gluing heat sinks on it.
People often have the current to their stepper motors set too high. This can cause the motor to get hot and skip steps so that, counter-intuitively, reducing the current can effectively make the motor produce more torque.
Locate the potentiometer for the motor in question on your motor controller board. Issue a command to your printer to turn the motor in question(ie. extrude, or move an axis). While the motor is turning turn the potentiometer counter-clockwise to reduce the current supplied to the motor until it cannot turn. When the motor cannot move, turn the potentiometer clockwise until the motor begins to move again- then turn it just a tiny bit more. Now your current is set for optimal performance.
IF you still have problems with the motor heating up, heat sinks may be required but even if they are, setting the motor current properly will make your printer operate more consistently and reliably.
Yup, I did that current adjust procedure a while ago - at first the extruder motor was very warm, after adjusting, not so much. But still warm.
If you can touch the motor and leave a finger on it, I don’t think the heat sinks will have much useful effect. I’d suspect it was more likely the loose wire. But they won’t hurt anything, either. 
Adjusting the current is true in most cases, but not with the printrbot and their aluminum direct extruder. Many of us have already been down this road and the only effective remedy is the heatsink or heatsink/fan combo.
Yes. Not just the aluminum extruder, the wooden direct one as well. I’ve never gotten PLA feeding through reliably without cooling the E motor.
(The problem isn’t that the motor gets hot, it’s that it heats the PLA)
So, if I do decide to add a fan to this, it would seem that the goal should be to blow on the extruder to cool it and the PLA down?
I’ve had really good luck with cheap CPU cooler fans on motors. Temperature reduction on long runs is rather amazing.
