Extruder Stepper Motor Stripping filament

Hi Guys,
I have built a RepRap Kossel and when it prints the extruder motor starts to print and the motor slows down it then speeds up, and once it speeds up it strips the filament, so then you have to push it by hand to get it going again, any advice on what i can do?

Edited 2 time(s). Last edit at 11/25/2015 02:11AM by IKE323.

Did the question change?
I had a similar issue and it was because I had my calibration for extruder wrong. I then calibrated it such that 20mm on the program gives 20mm in real life, worked better.

about motor going back and forth non-stop:
Is your retraction length is set to a large number? I have it at 2mm now but had it at 20mm before... it was doing just what you describe.

Edited 1 time(s). Last edit at 11/25/2015 02:15AM by djtrance2.

Is this situated in the firmware?

This is in the slicer configuration. under printer settings-->extruder

Yes for some reason my retraction length is on 2mm which is weird

I will try disable retraction and see if it works

Reduce extruder current until it skips steps instead of stripping.
But the main thing is to adjust steps/mm.
-Olaf

Would i do this in repetier or in firmware? And if so where?

Edited 1 time(s). Last edit at 11/25/2015 05:40AM by IKE323.

Leave the current setting where it is supposed to be and tighten the spring tension on the pinch wheel. It should be so tight that it almost crushes the filament.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Ok thanks that worked, but now i have other issues to sort out such as the top will not close and the layers are atrocious!

I just went through this. My bearing was applying to much pressure on the filament. That and to much retraction was causing jams. I set retract to 1mm and 100mm/sec retract speed and adjusted bearing to minimum pressure. My stripping generally happened when printing lettering and support material. The constant in and out was damaging the filament.

Changing the steps/mm is probably your problem here if you loaded straight whatever came with the Kossel (other than the firmware being for another type of printer instead of delta!).

This can be changed in the firmware, however, you can change it using some commands on repetier instead to set the steps/mm and write it to eeprom.

Here is a page with all the awesome commands:
[reprap.org]

Our printer uses the Marlin firmware, so only the commands that are Marlin: YES will work.

In particular:
M665 will set your curvatures, such that you can print flat on the print bed.
M666 sets the distance from the endstops
M92 sets the steps/mm for a specific axis, in this case, you want to play with E axis which is the extruder.

Make sure when you type
G1 E100 F1000
the PLA should move by 100mm. This is a little easier if you disconnect the teflon tube from the hotend so you can see the filament feed in and out
If it is incorrect, measure how much came out and adjust your M92 E...

To write to EEPROM, it is M500
To read from EEPROM, it is M501

The value for E should be updated with the new one you entered and saved.

Oh another thing.

Are you using Slicer in Repetier?
It was pointed out to be that the new version that comes with Repetier has a bug, which overextrudes!!

I downgraded to Slicer 1.1.7 and it printed WAY better!

Yes i am using Slicer 1.2.9, its driving me crazy as the infill and pattern wont change, it wont close the top of the item and sometimes is very bad

Edited 1 time(s). Last edit at 11/26/2015 04:33AM by IKE323.

definitely try Slic3r 1.1.7 and let us know if it fixes your problems

Ok so i have tried the Slicer 1.1.7 and it seems to be better but the infill and side are still very bad? I have used a 50% honeycomb infill.
Any other suggestions?

I'd say that is a pretty piece if the jumble in the middle is supposed to be there.