Blob on color change - Retraction Issue?
 
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3d person
(@3d-person)
New Member
Blob on color change - Retraction Issue?

I have been doing color changes using M600. Through this, the printer prompts me to change filament, purges the filament, and then moves into position and starts printing. When it gets to position, it dumps a blob of material onto the print.

I think this is due to the M600 command being created inside of a retraction cycle. Here is a gcode sample:

;BEFORE_LAYER_CHANGE
M117 INDICATOR-Layer3
;0.6


G1 E-3.50000 F3600.000
;WIPE_START
G1 F7200.000
G1 X157.063 Y99.757 E-0.21011
G1 X157.063 Y99.178 E-0.27503
G1 X156.581 Y99.659 E-0.32330
G1 X156.274 Y99.388 E-0.19486
G1 X156.901 Y98.760 E-0.42170
;WIPE_END
G1 E-0.07500 F3600.000
G1 Z0.600 F9000.000
;AFTER_LAYER_CHANGE
;0.6
;COLOR_CHANGE,T0
M600
@Object Frantic Rottis-Waasa.stl id:0 copy 0
G1 X118.370 Y105.847
G1 E5.00000 F2400.000
;TYPE:Perimeter
;WIDTH:0.45
G1 F1500.000
G1 X117.280 Y109.042 E0.11425

You can see the layer end - retract - M600 - move to position, then G1 E5.00000 F2400.000 filament "blob" squirting onto the print. The nozzle is already primed due to the M600 purging.

To fix this for myself, I added custom G-code for layer changes

M600
G1 E-5 F3600.000

The question for the forum is: should the slicer correct for this? There was a bit of troubleshooting for me to find this - is anyone else having this issue?

This topic was modified 2 years ago by 3d person
Posted : 13/02/2021 10:34 pm
JoanTabb
(@joantabb)
Moderator
RE: Blob on color change - Retraction Issue?

Most folk just use M600, change the filament, check the new filament is the correct colour, hold the waste pile, complete the change sequence and watch in awe, as the extruder squirts a little more filament and progresses back to the job at hand, neatly detaching both the main purge and subsequent purge, in one action. 

but if your process pleases you, and is successful, then there is no issue with modifying gcode. 

regards Joan

 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 13/02/2021 11:12 pm
3d person
(@3d-person)
New Member
Topic starter answered:
RE: Blob on color change - Retraction Issue?

@joantabb

Thanks for the reply. The issue is that the blob happens on top of the print, not off to the side. It doesn't seem like that's a desired function.

Posted : 14/02/2021 12:39 am
Gary Mackey
(@gary-mackey)
New Member
RE: Blob on color change - Retraction Issue?

@joantabb

I am having the same issue in that the extruder deposits a blob on the part when starting after a color change.  The blob is on the part and ruins the part.

I have tried wiping the  nozzle with a paper towel as the extruder moves to the start location, with no result.

This issue is on my Mini,  never had this issue with my MK3.  Any thoughts on how to fix?  I am not experienced enough to modify G code yet.

Also, having minor stringing issues that I never had on my MK3.

thank you.

Posted : 31/03/2021 2:45 pm
3d person
(@3d-person)
New Member
Topic starter answered:
RE: Blob on color change - Retraction Issue?
Posted by: @gary-mackey

@joantabb

I am having the same issue in that the extruder deposits a blob on the part when starting after a color change.  The blob is on the part and ruins the part.

I have tried wiping the  nozzle with a paper towel as the extruder moves to the start location, with no result.

This issue is on my Mini,  never had this issue with my MK3.  Any thoughts on how to fix?  I am not experienced enough to modify G code yet.

Also, having minor stringing issues that I never had on my MK3.

thank you.

Hi Gary,

I'm also interested to hear if there's any more discussion on this. It seems like a bug and that's why I posted it here. Since I added the custom G code for layer changes, this has been a lot better. 

M600
G1 E-5 F3600.000

 

Posted : 31/03/2021 6:16 pm
NickRno77
(@nickrno77)
Trusted Member
RE:

 

Posted by: @3d-person
Posted by: @gary-mackey

@joantabb

I am having the same issue in that the extruder deposits a blob on the part when starting after a color change.  The blob is on the part and ruins the part.

I have tried wiping the  nozzle with a paper towel as the extruder moves to the start location, with no result.

This issue is on my Mini,  never had this issue with my MK3.  Any thoughts on how to fix?  I am not experienced enough to modify G code yet.

Also, having minor stringing issues that I never had on my MK3.

thank you.

Hi Gary,

I'm also interested to hear if there's any more discussion on this. It seems like a bug and that's why I posted it here. Since I added the custom G code for layer changes, this has been a lot better. 

M600
G1 E-5 F3600.000

 

I’ve started getting this blobbing again, possibly because I’m printing 4 item on the plate. 1 item I haven’t had an issue. Where in the layer change gcode section do you put this line, before or after ? Thanks .

BTW I have "Retraction when tool is disabled" to 0 for all extruders which is meant to stop the blobbing ?

This post was modified 4 months ago by NickRno77
Posted : 09/06/2022 12:46 pm
JoanTabb
(@joantabb)
Moderator
RE: Blob on color change - Retraction Issue?

I now make the colour change 1 layer higher than it needs to be.
the M600 colourchange process starts as I have mentioned above, then when it returns to the model, it goes back to the exact point at which it initiated the colourchange and then moves to the new start point for the new colour. 
IF you have gone up, one layer into say the text you are trying to hilight, any point where the previous layer finishes, will be beneath the new colour, so a sot of new colour, will not be a problem

regards Joan

 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 09/06/2022 12:52 pm
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