Extruder Motor Problem

Hi everyone,

I'm a beginner, so excuse me for my lack of printing knowledge. I finished building my i3 a couple of days ago and have been trying to print using Repetier Host and Slic3r, as recommended by RepRap Guru.
I've tried several times now to print a simple Lego brick, but no PLA is extruded and the extruder motor is making a clicking sound. When I control the extruder manually via Repetier, the filament comes out in a fairly unpredictable manner (extruding 10mm actually gives much more than 10mm, while 5mm may not extrude anything at all), but it does extrude and the motor does not make the clicking sound.
What am I doing wrong?

Sounds like the motor may not be getting enough current. On the stepper motor driver for the extruder motor, you should find a small potentiometer that controls current to the motor. Try adjusting that up (clockwise) in small increments of about a quarter turn and see if the motor behaves differently. When extruding manually, you should definitely be able to get a consistent amount out.

When adjusting the potentiometer, make sure you either power off the printer, or use a special anti-static screwdriver designed for this purpose.

I adjusted the pot up to .6V with no better results, then went back to the recommended setting of .55V.

I should describe in more detail what is happening with the manually controlled extrusion. It seems to pull in a consistent amount of filament without any issue, but the filament that is extruded comes out quickly at first, then slows down and oozes for quite a while. When I say to extrude 10mm, I assume that means that 10mm should come out of the nozzle rather than 10mm being pulled into the extruder.

I tried to print again and noticed that as the motor clicks, it also occasionally pulls in a bit of filament and then retracts about the same amount almost immediately.

When you ask repitier or pronterface to extrude 10mm of filament it means 10mm into the extruder.
I assume it's a MK8 or 9 style extruder? Sounds like either the motor current needs to be increased or the filament is jamming in the throat because of "heat creep"

Steve

---

My updated Instructable on our Prusa i3 Build
[www.instructables.com]

Try raising the Z-axis home offset to see if that solves the extrusion problem first--the nozzle might be getting blocked if it's too close to the bed initially.

If the extruder steps continue being inconsistent, you could address this issue next.

I'm having similar issues. At first the extruder almost worked. I did get one 3D print that seemed mostly melted, but it at least looked like it was trying to work. After that I have had very little success. The extruder motor clicks a lot. I suspect the stepper motor is cogging, so I kept increasing the current through the motor. Currently I'm driving the motor with the maximum current possible. The motor and driver get very hot. The default settings for the printer suggest a 230 degree temp for the first layer and 210 for subsequent layers. On my printer, the only way to get the PLA to flow is to raise the temperature to 240. When I manually run the extruder, I get non-uniform amount of material to come out of the printer. See the video here: [youtu.be]


At this point I'm considering returning the printer.

Firstly 240C is far to hot for PLA. You should be able to print PLA at an extruder temperature of between 190 and 210C, (unless what you have is ABS or PLA+ and not straight PLA). The reason the extruder motor is missing steps is not the current, which you need to turn back down again straight away, but probably because there is an obstruction in the throat tube or damage to the PTFE liner. If this is the case then the motor simply cannot push the filament through because of the pressure build up. You should easily be able to push the filament in by hand if everything is OK and you hold down the release button.

I would invest in a new throat tube and liner, they are not expensive. Check that there is no swarf or anything else in the tube and liner before assembling. The throat tube goes into the heater block with the PTFE liner downward towards the nozzle. It wouldn't be the first time that one of these has been fitted the wrong way up. First screw the nozzle into the heater block and then back it off about 1 turn. Make sure the liner is in the throat tube and screw into the heater block by hand from the top until it hits the nozzle. Get two proper spanners, one to fit the heater block and the other to fit the nozzle. Heat the extruder and holding the block still with one spanner, tighten the nozzle with the other. Allow all to cool down and then screw into place in the extruder block and lock in position.

Don't try to remove the nozzle in future without the two spanners and without heating the extruder or you will snap the nozzle or the throat tube.

Edited 1 time(s). Last edit at 02/16/2017 12:28PM by Supermec.