Retraction Value

[lamina]

Hi - I have been experimenting with varying the print parameters in Creator 1.1.5 and have noticed some odd effects with the retraction values.
Whenever I increased the value from zero to say, 1.0, the printer would leave a largish blob after each movement. The greater the retraction value, the larger the blob.
This seemed the wrong way round - I thought retraction would 'suck' the material back up the extruder so avoid blobs - so I looked at the Gcode.
This is a part of the code for a 40mm test cylinder with no retraction set,

G92 E0
G2 X87.605 Y109.882 I12.395 J15.118 E5.5591 F1182
G0 X87.661 Y109.965 F18000
G92 E0

and this is the same item with a 1.1mm retraction:

G92 E0
G1 E1.1 F360
G2 X87.591 Y109.894 I12.409 J15.106 E6.6594 F1182
G1 E5.5594 F1200
G0 X87.661 Y109.965 F18000
G92 E0

Question: shouldn't the G1 E1.1 F360 be G1 E-1.1 F360?

Any help would be much appreciated.

Richard

[jimc]

Why would there be a dash? I look at all the other gcodes in the list and none have dashes. I was getting a similar problem with the retraction. It was retracting and doing its thing however. What the issue seems to be though is that the extruder stops, retracts then moves so it adds some time as well. I found for a correct blobless move it required a combination of retract, coast and a -.2 in the restart distance. My blobs would always be at the beginning if each line and that took care of it.

[dalew8abz]

Richard,

Here's how I interpret the G-code you posted (my comments added to code). Let me know if this makes sense....

G92 E0 ; zero the extruder at current position
G1 E1.1 F360 ; extrude 1.1 mm filament --- this is the RETURN from the previous retraction, which would be two lines before the G92 E0 line...
G2 X87.591 Y109.894 I12.409 J15.106 E6.6594 F1182 ; move X/Y and extrude 5.5594 mm filament --- this is laying down filament, going from the 1.1000 above to 6.6594, thus 5.5594 mm
G1 E5.5594 F1200 ; extrude -1.1 mm of filament --- this is moving the filament from +6.6594 to +5.5594, thus -1.1000 mm
G0 X87.661 Y109.965 F18000 ; we retracted the filament, now do the X/Y rapid
G92 E0 ; zero the extruder. Next step will be to extrude 1.1 mm to RETURN from the retract two lines up...

I think they have it right. And if we put in an offset for return from retraction, it would be added to the G1 E... F360 line.

Dale

[lamina]

Hi Jmic and Dale - all makes sense but put it this way - when I enable G2/G3 codes I get an almighty great lump of plastic shooting out of the nozzle and when I put the retract value to zero
I don't get an almighty great lump of plastic at each reversal. I like the G2/G3 code - its neater and I'd like to play around with retraction settings.
I just like to know why 'things' do what they do and I shall continue to 'experiment' with settings to find out why
Richard

[jimc]

haha wow i must have breathed in too many paint fumes when i posted that:? you meant -1.1mm lol. the way it was written just seemed like a dash. the old came on eventually haha. well in any case my retraction is set to 1.2 and it does retract not push out. i can visibly see that happening before the jump. i have spent alot of time testing the retract setting to decrease the blob and have mine pretty much going perfectly now with my abs settings. im not sure if your using abs or pla but if abs try and use the last fff settings i posted in the m2 configuration thread. if you have not read that thread then i suggest you do. lots of good info there.


http://forum.simplify3d.com/viewtopic.p ... 9&start=20

[lamina]

Hi Jimc, I am printing ABS and the fff settings I use work beautifully so long as I don't select G2/G3 arc commands in Creator. As soon as I select that option and have retract set to anything, the extruder head goes merrily on a beautiful arc, stops, extrudes a blob of plastic, lifts, ploughs its way through the blob and so on. When I say a blob I mean a blob - this is a serious lump of plastic - not a little blip.
But when I get time I will fiddle about (experiment) some more and hopefully isolate the problem.
Richard

[lamina]

Hi, this is a problem with Marlin firmware, apparently. Gcode is correct so about to dig into the firmware

[jimc]

yes not sure if your running a m2 or not but apparently only the newer ones can handle the g2/g3 codes. atleast thats what im told. i have tried the g2/g3 option on mine and saw no difference either way so i just left it off.

[dalew8abz]

And (as jimc will tell you because I told him) I switched on G2/G3 in Creator for my M2 (which I received in 04/2013) and it made a NOTICABLE improvement in the cylindrical columns on the MAKE Magazine "torture test" object. MUCH smoother columns, more consistent diameter/circularity and layer-to-layer alignment.

Dale

[whoDat]

Curious which "retraction value" you guys are talking about?

In Creator 1.1.5, I see "Retraction Distance", "Extra Restart Distance", "Retraction Vertical Lift", and "Retraction Speed" all under the Retraction area. I am having problems with little dimples where the print head stops and starts, and thinking I need to adjust one of these settings?