Back Pressure on Extruder causing voids inside the print.

Hi All,

I am starting to calibrate my RepRap,but I have a problem where I get some empty spaces at the beginning of each line..
What I noticed is that whenever the wade extruder stops, the pressure from the molten ABS filament forces the stepper to move backwards, so when it restarts extruding, it will take some time until plastic comes out again.

The obvious thing to do for me was to set the "DISABLE_E" to true in the sprinter firmware config.h, but since I am using Gen 7 electronics where all the stepper enable pins are connected, this caused the Z axis to behave strangely where it started skipping layers!! , so I set it back to false where all was back to normal (for the Z at least)

I moved my focus to Skeinforge, where I set the "Restart extra distance" to some values between 1 and 20 mm, and the retraction distance to values between 0 and 10mm, and the minimum travel for retraction to 0, 0.01, 0.1 and 1mm with no difference (I don't remember all the mixes I have used from the above, but I had a lot of attempts)..

Any help or ideas are appreciated..
** Meanwhile, I will move back to the officially supported Teacup firmware and see what happens.. but when I tried it, the heater won't turn on, knowing that when I first tried it, the heater worked

Thanks

The extruder should always be enabled and it should therefore not move backwards due to the pressure. It should however be driven backwards 1-2mm quickly, I use 10mm/s and at the start of the next line it should go quickly forwards the same distance it retracts.

Set retract distance to 2mm, Set the retract speed to 10mm/s and extra the extra distance to 0. Minimum travel can be zero for best quality but you can increase it to speed up the build.

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[www.hydraraptor.blogspot.com]

Thanx Nophead..

I used your settings, and increased the Z axis power in the pololu, and things seem to be working now.. Off to continuing the calibration..