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Over extrusion after filament change.  

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Lazypug
(@lazypug)
Active Member
Over extrusion after filament change.

Hi,

I have been using PrusaSilcer 2.2's filament change settings (m600) and have noticed after the change is complete and the oozing is dealt with, the printer will extrude a large about of filament as part of its normal movement on the printed piece. This causes ton of issues as you can imagine. I am fairly new to gcode but savvy enough to navigate it and found this interesting piece (the problem)

M600
G1 X126.879 Y103.121
G1 Z2.625
G1 E5.00000 F1800.00000 

The bolded code is what is causing the issue. I have commented it out and the printer no longer "spits" out filament once printing continue. However, I have to edit the gcode manually after every slice so its not too much work but I rather have it built in to the slicer.

My question is, why is after a M600 operation, the slicer tells the extrude a large amount of filament? Is this a bug if so, how can I report it?

Thanks for the help!

 

Posted : 19/08/2020 2:53 am
Lazypug
(@lazypug)
Active Member
Topic starter answered:
RE: Over extrusion after filament change.

Here are some screen shots of pre and post G1 E5.00000 F1800.00000 commenting.

Circled yellow is with this gcode

M600
G1 X126.879 Y103.121
G1 Z2.625
; G1 E5.00000 F1800.00000 

Circled red is with the gcode untouched

Posted : 19/08/2020 2:42 pm
3DPrintBurgas
(@3dprintburgas)
New Member
RE: Over extrusion after filament change.

@lazy_pugz

Hi there, I have the same issue with my prints and I am forced to edit the G-Code manually.

Did you manage to find a solution of the issue?

 

Regards and many thanks in advance for your kind cooperation.

Posted : 04/09/2020 8:25 am
Neophyl
(@neophyl)
Illustrious Member
RE: Over extrusion after filament change.

Issue can be reported over on github. Slicer ones here https://github.com/prusa3d/PrusaSlicer/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc

I believe from reading previous posts and github issues that the action is deliberate.  The correct sequence for user intervention is to not remove the excess from the nozzle but to grip it with a pair of tweezers, then hit the continue button,  then when it extrudes the 5mm to re-prime the extruder pressure before printing when it moves the excess is pulled away as you have it in the tweezers. 

Most seem to be removing the strand, hitting go and then having trouble removing the extra prime bit.  

Posted : 04/09/2020 8:37 am
Lazypug
(@lazypug)
Active Member
Topic starter answered:
RE: Over extrusion after filament change.

@neophyl

Thank you for the insight. I will test out the "hold the excess" method and see if it makes a different. Though I do not think it will as when it reprimes the extruder, it does it directly on the print. I will check.

Posted : 04/09/2020 2:18 pm
Lazypug
(@lazypug)
Active Member
Topic starter answered:
RE: Over extrusion after filament change.

@ivan-k9

No solution found just yet except editing out the repriming gcode. I will have to try out the method mentioned by @neophyl.

Posted : 04/09/2020 2:19 pm
Lazypug
(@lazypug)
Active Member
Topic starter answered:
RE: Over extrusion after filament change.

One of the thing I wanted to try is adding a wipe tower. I am fairly new to this hobby but I have been hearing a lot about it.

What I expect to happen is the extruder repriming will be done over the wipe tower instead of the print. I just need to figure out how to set one up.

Posted : 04/09/2020 2:27 pm
bobstro
(@bobstro)
Illustrious Member
RE: Over extrusion after filament change.

I recall reading that the bit of extrusion was deliberately added to counter a problem of under-extrusion when the print restarts. The thinking was that grabbing a bit of filament with tweezers was preferable to a print with a visible gap.

My notes and disclaimers on 3D printing

and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

Posted : 04/09/2020 5:04 pm
prusanewuser
(@prusanewuser)
Prominent Member
Pile of unwanted extra filament at a corner

Here is one problem. At each layer, the print started at the same corner of a box and I needed to change filament each layer. Even I used tweezers to remove the over extruded filament, when the nozzle reached the same corner, it seems to have extruded more than it was supposed to. After several layer changes, that corner became an ugly triangle shaped pile of unwanted filament. What can be done to avoid this?

Posted : 13/09/2021 2:52 am
Xanthe
(@xanthe)
Trusted Member
Semi-automatic editing of gcode

On Windows you can use FNR.exe to automate repeated edits such as this - setup a Windows command file with the required edit command and run this on the gcode file - saves manual editing.

Posted : 13/09/2021 9:56 pm
EsotericMaker
(@esotericmaker)
Trusted Member
RE: Over extrusion after filament change.

 

Posted by: @neophyl

The correct sequence for user intervention is to not remove the excess from the nozzle but to grip it with a pair of tweezers, then hit the continue button,  then when it extrudes the 5mm to re-prime the extruder pressure before printing when it moves the excess is pulled away as you have it in the tweezers. 

Why is re-priming necessary? It's just been PRIMED.

After all by definition of a filament change, the extruder has just been primed by the new filament. Indeed, unless you see new filament coming out properly, you shouldn't be confirming "yes" that the filament change was successfully completed.

It's hard to believe that the extruder becomes "unprimed" in the second or two between hitting "yes" and the new extrusion. If this were the case, then you would have this problem in spades every time you "paused" a print -- and the extruder does not "re-prime" when it resumes.

Posted : 27/04/2023 6:37 pm
Neophyl
(@neophyl)
Illustrious Member
RE: Over extrusion after filament change.

You want a definitive answer then go ask a Prusa dev over on github to explain.  Its not my logic, just passing on what I've learned of the 'correct' way to do this with PS.  However I have seen slight gaps in perimeters after a normal pause, at full printing temp filament can leak out in just a few seconds, its what gives stringing on travels after all.  

Take the advice or don't.

Posted : 27/04/2023 6:46 pm
EsotericMaker
(@esotericmaker)
Trusted Member
RE: Over extrusion after filament change.

I did file it as a "bug" report on github - maybe a compromise could be to make the extrusion length a configurable parameter - anywhere from 0 to however long you want it.

Posted : 27/04/2023 6:49 pm
Neophyl
(@neophyl)
Illustrious Member
RE: Over extrusion after filament change.

If you are the user 'puterboy' on github who opened an issue about this a couple of hours ago you should be aware that the extra purge of filament is NOT generated by Prusa Slicer but by the printers firmware.  As such putting a bug in there wont get you very far.

Assuming you are using a Prusa Printer (given the forum we are currently in) then it needs to go into the Mk3 forum.  You are in luck though cause there has been an issue there regarding this for years.  https://github.com/prusa3d/Prusa-Firmware/issues/197   opened in 2017.   Several opened in fact. 
Given the age of the Mk3 and limitations on the memory space available in the 8 bit board and that Prusa has gone to a 32 bit board on the new printers then I'd rate the chances of this being altered in the Mk3 firmware in the region of slim to snowballs chance in hell.

 

 

Posted : 27/04/2023 8:57 pm
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