"Weak" extruder drive

Hello,

I have a RepRapPro Fisher 1.0. I've been using it for almost a month now and noticed that in case of some filaments it needed a much higher temperature than my other 3D printer (a Huxley). It seemed to be getting worse and worse every week. I finally concluded that there was something wrong with my extruder drive.

The symptom is that during a print, sometimes the extruder drive keeps "slipping back" a quarter a rotation. It's not only the filament, I can see the little gear rolling backwards as well. It looks almost like the back move of a retraction, only that this is much faster and seems to be forced externally. As if it did not have the force to push the filament into the hot end and the tension in the bowden kicks back. So, I tried testing the force of the drive itself and found this:

If I put the extruder drive into idle hold, it does not take a lot of force to rotate the small gear. And if I remove the filament and just tell the motor to extrude a few dozen centimeter of filament slowly, it does not need a lot of force to stop it. My previous experience is that these Nema17 steppers are brutally strong. There should be no way that I could rotate the axis by bare hands when it is holding. So there is something wrong with my extruder drive. What can it be? The stepper motor? The electronics?

Hi, first post for me. I actually found this place looking for the answer to this exact question. I've just bought my first printer, an Afinibot prusa... It works well, but starts to click and retract the filament at flow rates of about 0.2mm and 50mm/s... Since I'm a newbie at 3D printing, I'm a little lost. /Stefan

edit:

Right now it´s printing an oloid shape at 0.1mm/60mm/s beautifully. The interesting part is that if I pinch the filament the stepper pulls strong, resistance alone doesn´t make it retract or skip. But when I increase the speed and thickness to 0.2 it starts clicking pretty much straight away. Is it nozzle pressure? I´ve tried temps on my PLA from 195-210 without a difference...

extremely annoying since it ruins my prints (underextrusion)

/Stefan

Edited 1 time(s). Last edit at 12/18/2015 04:54PM by Steleei.

Bear in mind that by default, after 30 seconds of inactivity the stepper motor current is reduced to 30% of normal. If you want to see how strong the extruder is in normal use, either test it within 30 seconds of extruding or retracting, or send M906 I100 to set the idle motor current to 100%.

What current is the extruder stepper set to in the M906 command in config.g?

Edited 1 time(s). Last edit at 12/18/2015 05:58PM by dc42.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

On my part, I don´t know. I´ve been looking for a way to check the extruder stepper current but I don´t know how to do it. I can access some information on teh display but I guess I´ll have to hook up a computer to the printer. What program do I need? Rookie-deluxe question I know, but I´m new at this... Also, being chinese there was no manual for the firmware included so I´m sorta learning as I go.

/Stefan

To find what the motor currents are set to, send M906 from the gcode console tab on the web interface.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Ok, thanks. Right now I only have Repetier-Host, and that has some basic printer settings in it but nothing that I can find that would allow me to send commands. The only data I can find is that maximum feedrate is set to 12 cubic mm/s. And that should be enough as far as I can tell.

So what web interface are we talking about? I apologize for being a noob

/Stefan

Quote
Steleei
Ok, thanks. Right now I only have Repetier-Host, and that has some basic printer settings in it but nothing that I can find that would allow me to send commands. The only data I can find is that maximum feedrate is set to 12 cubic mm/s. And that should be enough as far as I can tell.

So what web interface are we talking about? I apologize for being a noob

/Stefan

I think the first thing we need to be sure of is What Printer you have and what is the Electronics on it? actually you did say it was an afinibot purse so I suspect it will have a Mega2560/Ramps board or possibly a Melzi board if So then I think you are asking in the wrong area of the forum and you need to be asking in the generic RepRap or the controllers section!

Doug

Fisher (and duet):
I checked the motor currents.

Quote

M906
Axis currents (mA) - X:800, Y:800, Z:800, E:1000:1000:1000:1000:1000, idle factor 30

I already figured out the idle factor empirically when checking the strength of the idle hold. I noticed that the strength required to rotate the small gear is moderate in the first 30 seconds and much easier afterwards. Almost as easy as when the motor is completely disabled, just not as smooth.
I also tried moving the XYZ carriages up and down during idle hold and I can move those as well. Not easily, but they do move.