Retraction problem

Hi,

I have a problem with extruder motor while retractiong. The motor just stutters. I have Sanguinololu 1.3a with Sprinter firmware and I use Slic3r and Printrun.
I thought the problem could be caused by overheating the Pololu, overloading the motor, bad wiring, damaged motor or damaged Pololu. I tried to eliminate these possible causes but it did not help.

I noticed that the problem occures only while I am printing. I can run the motor using Printrun in both directions in high speed (higher than 6000mm/min) without having the problem. But when I run a "print" ( I have plugged only the extruder motor ) the problem occures again and again and in the same sections of g-code.

For example, this section of g-code does not cause the problem:

...
G1 X87.900 Y74.358 E2.12886
G1 X88.620 Y74.249 F6000.000
G1 F2400.000 E0.87886
G92 E0
G1 X52.232 Y56.482 F6000.000
G1 F2400.000 E1.25000
G1 X129.268 Y56.482 F1260.000 E3.50253
G1 X129.268 Y64.982 E3.75107
...

But this section does cause the problem:

...
G1 X52.232 Y123.518 E8.67943
G1 X52.232 Y56.580 E10.63669
G1 F2400.000 E9.38669
G92 E0
G1 X72.234 Y108.921 F6000.000
G1 F2400.000 E1.25000
G1 X72.077 Y108.831 F1080.000 E1.25531
G1 X72.254 Y108.000 E1.28014
...

What could be the pest? Am I missing something?

Thank you for help.

Edited 1 time(s). Last edit at 01/25/2014 08:12AM by ncq.

Retraction speed is too high. I had the same problem, just set it lower (for me it was at 40mm/s and changing it to 35mm would already improve, but at 30mm/s it just works flawlessly )

Thank you for your reply Ohmarinus!

Your are almost right ! If I lower the retraction speed to 35mm/min it seems to work, but 40mm/min unfortunately does not work for me. It is really suprising because I have been printing with 50mm/min for a half year without any problems and this problem occured three days ago when I solved another problem with overloading y-motor because of damaged bearing.

It seems to me that something is broken or something has changed, but I do not know what.

I really thank you Ohmarus because it works (I have not tested it much) but I am still confused about the change of behaviour.

Any more ideas?

The retraction speed is in mm/s. The default in slic3r is 30 mm/s. If it works at that speed, why do you need to run it faster at 40 mm/s? Just curious.

Ou, my fault, everything is ok. I need more sleep Thank oyu guys and I am sorry for my stupid questions!

There are no such thing as a stupid question.

Quote
brnrd
The retraction speed is in mm/s. The default in slic3r is 30 mm/s. If it works at that speed, why do you need to run it faster at 40 mm/s? Just curious.

In Cura, standard was 40mm/s
But you're right, I forgot he was using Slic3r.

So 30mm/s would be the right speed I guess.