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Blobs from undone retraction at start

Posted by BenZ 
Blobs from undone retraction at start
September 27, 2014 10:49AM
Hi
My Skeinforge (latest version) adds a "undo retraction" step (positive value) right at the beginning of the print. I found in dimension.py that the "undo retraction" is added after a M101 command. Well, I didn't looked too long.
The effect is, there are large blobs at the first layers since the extruder has pumped 3mm too much filament into the hotend.
If I remove the retraction command manually in the gcode, I get good prints.

In the Skeinforge generated code below, two line before the first M101 command there is a "G1 E3.15" WITHOUT preceeding retraction ==> too much filament.

What is wrong? The M101 command or the added "undo retraction"? Shall I file a bug? My settings wrong?

Sample code
G21
G90
M83
M206 X-9 Y-5 Z-0.07
M92 E892
M140 S40
M104 S175
G28
M190 S40
M109 S175
G1 Y15.0 F8000
G1 X123.0
M109 S210
G1 X142.0
G1 F600 E5
G1 Y25.0 F8000
G1 X10.0
M104 S210
M113 S1.0
M108 S0.96
G1 X56.039 Y70.245 Z0.05 F9000.0
G1 F1200.0
G1 E3.15
G1 F9000.0
M101
G1 X56.611 Y73.99 Z0.05 F57.6 E0.0974
G1 X58.305 Y77.623 E0.1031
G1 X60.566 Y80.299 E0.0901
G1 X63.488 Y82.333 E0.0916
G1 X65.832 Y83.325 E0.0654
G1 X69.436 Y83.955 E0.0941
G1 X71.814 Y83.831 E0.0612
G1 X75.308 Y82.922 E0.0928
G1 X78.422 Y81.132 E0.0924
G1 X80.766 Y78.917 E0.0829
G1 X83.14 Y74.553 E0.1278
G1 X83.34 Y70.764 E0.0976
G1 X83.009 Y66.582 E0.1079
G1 X81.567 Y62.948 E0.1005
G1 X79.36 Y60.118 E0.0923
G1 X77.77 Y58.765 E0.0537
G1 X75.495 Y57.431 E0.0678
G1 X71.912 Y56.328 E0.0964
G1 X69.513 Y56.135 E0.0619
G1 X65.879 Y56.663 E0.0944
G1 X63.575 Y57.616 E0.0641
G1 X60.549 Y59.712 E0.0947
G1 X58.114 Y62.699 E0.0991
G1 X56.474 Y66.598 E0.1088
G1 X56.039 Y70.245 E0.0944
G1 F1200.0
G1 E-3.2
G1 F57.6
M103
M108 S0.96
G1 X63.168 Y61.603 Z0.05 F9000.0
G1 F1200.0
G1 E3.15
G1 F9000.0
M101
G1 X63.933 Y61.004 Z0.05 F57.6 E0.025
G1 X65.243 Y60.248 E0.0389
G1 X66.648 Y59.685 E0.0389
G1 X68.12 Y59.364 E0.0387
Re: Blobs from undone retraction at start
March 07, 2015 01:00PM
For the records. I solved it by changing the python code.
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