Extruder motor burnt out?
After getting my MK2S to MK3 upgrade kit, I was totally over the moon. I printed out the required parts for the printer then upgraded the machine to the MK3. All was good including doing a few test prints and honing for the z-axis.
This was until I decided to start printing something properly. Everything seemed fine until about 5mm into the print, then I started hearing a clicking sound, then it went away and continued to print normally. Then after a few more milimetres I heard more clicking sound and found that the filament wasn't catching, however that wasn't the only issue.
After a few more minutes the Extruder motor seemed to stop rotating altogether, in fact, the Extruder motor now makes a wine sound when trying to load the filament and the axel does not rotate at all. I have tried to load the filament without any filament to see if it is rotating correctly, but alas there is still no movement despite the motor getting very hot and a whining coming from the motor upon initial loading.
I've attached a video to show you where the filament enters the Extruder and the non-movement of the motor. Could this be a burnt out motor or shall I try swapping it with the X-axis motor first to see if that has the same issue?
Re: Extruder motor burnt out?
It is possible that you have a broken wire between the EINSY board and the motor, or that the motor cable is not plugged into the board completely.
It is also possible that something has jammed the shaft so it can't turn. For example, if the setscrew is not completely tightened, it can stick out and run into the plastic Extruder body.
It's extremely unlikely that the motor has burned out. They can operate all day long at 100C without failing. Inside, the only parts are stationary coils of wire and rotating permanent magnets with "teeth" that establish the steps per revolution. Add bearings at each end, and that's about it.
The way that stepper motors work, is that there is constantly a current through one or the other or both of the two coils whenever the motor is in use. Even if it's not moving, there can be electricity flowing. So stepper motor heating is not really a function of whether they are turning or not (or whether they are jammed and prevented from turning); the heating is determined by the setpoint current being sent to the motor. If your motor reaches temperatures over 80C, you can turn down the current a bit with G-codes because too much heat can result in the Bondtech gears getting warm and softening the filament.
Re: Extruder motor burnt out?
It is possible that you have a broken wire between the EINSY board and the motor, or that the motor cable is not plugged into the board completely.
It is also possible that something has jammed the shaft so it can't turn. For example, if the setscrew is not completely tightened, it can stick out and run into the plastic Extruder body.
To test everything I decided to swap the X and Extruder motors around with no sleeving or anything, simply bare. The wires are also spotless with no pinching or cuts anywhere. Every wire on the PCB was also tugged to see if they were clipped into position and neither were loose. In the end the X motor could pull the filament without a hitch, but now the X-Axis no longer worked because the Extruder motor simply isn't spinning. Again I can hear a whining sound like it's trying to turn, but nothing is actually moving.
I have even set the X and Extruder motors side-by-side without being attached to anything and can see that the X-Axis motor can work in both the X and Extruder PCB slots, yet the Extruder motor simply gives a whine. Again the wires on the Extruder motor are not defective anywhere.
It gives the impression that the motor is broken somehow and I don't know why.
Re: Extruder motor burnt out?
You have done a very good job of isolating the problem, and it does certainly sound like the motor (including cable and connector) has a problem somewhere.
If there is no power applied, do the two motors turn equally easily by hand? If the defective motor is very hard to turn, you may have a bad bearing or something loose inside the motor that is jamming it. If they turn equally easily, then you definitely have an electrical problem.
If you have a way to check resistance (ohms), you could measure from the plug end of the cable and see if you have continuity. There should be two independent circuits each with low resistance (ohms or tens of ohms), and infinite resistance between the two circuits. The two circuits should have very close to the same resistance. So if one circuit is, say, 10 ohms and the other circuit is either infinite ohms or zero ohms, that's the one with the problem. I'm pretty sure that one circuit is on the two adjacent pins on one end of the connector and the other circuit is on the two adjacent pins on the other end of the connector. If only one circuit is correct, the motor will whine and stutter but not move correctly.
If it were my motor, I'd poke around until I found the exact cause. But I'm an electrical engineer with good test equipment and lots of patience. If you don't have a good electronics workbench or the time to fuss with this, then the best solution is to just buy a new motor. If you get it directly from Prusa, it will be wired with the correct length of cable, connected in the right pattern. Otherwise you may have to do some soldering and/or crimping and connector assembly to get a generic motor hooked up correctly. Prusa might offer you some credit for returning the old motor, since they can probably diagnose it and recondition it for much less than the cost of a new motor.