Blob when printer restarts after manual color change.
 
Notifications
Clear all

Blob when printer restarts after manual color change.  

  RSS
Michael
(@michael-14)
New Member
Blob when printer restarts after manual color change.

PrusaSlicer 2.4.0 adds a "G1 E4" command after M600 for manual color changes. This has the effect of placing a blob of plastic on the part when it restarts after the color change. I can manually edit the gcode to remove it but I have to remember to do this every time I do a multi color, single extruder print. Also, this extra command doesn't get added for every color change, nor does it seem consistent for each extruder/T1/T0 command. I've had some prints that only did it twice for 10 color changes, and other prints do it every time the color is changed.

;WIPE_END
G1 E-3.6125 F2100
G1 Z.8 F10800
; Filament-specific end gcode 
;END gcode for filament
M600
T0
M104 S210 ; set temperature
; Filament gcode
; printing object jars cap labels id:0 copy 0
G1 X58.553 Y70.899
G1 Z.4
G1 E4 F2100

This issue has been brought up in the past but it doesn't appear to have a resolution yet. Maybe there is an if/then statement I could add to the custom gcode area of slicer? something like if "g1 e4" exists, get rid of it?

 

Thank you.

 

Posted : 30/01/2022 8:24 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
RE: Blob when printer restarts after manual color change.

development suggestions are best put on the Prusa Git Hub page for the relevant product.  where the developers spend a lot of time. 

I think the printer stops where it sees an M600 command, wanders off to change the filament, after successful filament change, it extrudes an additional squirt of filament to prime the nozzle, as it moves away from the filament change area. (which irritates some folk... )
then the printer returns to the place where it received the M600 command, and usually, immediately relocates to a new position to start a new section of the model. 
if it didn't return to the place it finished, these deposits would not happen... 

 

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 : 30/01/2022 11:07 pm
towlerg
(@towlerg)
Noble Member
RE: Blob when printer restarts after manual color change.

Use a post processor?

Posted : 31/01/2022 12:21 pm
Michael Casson
(@michael-casson)
New Member
RE: Blob when printer restarts after manual color change.

I might be necromancing the thread, but I'm experiencing the same issue as the OP with PrusaSlicer 2.5.0. It's not merely the oozing of the freshly primed nozzle leaving a spot on the last point of the old color, as mentioned by JoanTabb. (That does happen, too, though, yes.)

When manually changing colors, the printer is actually expelling a big blob right at the start of the new color, as if it's un-retracting after a move, but without having retracted before. What's even more curious is that it only does this one some color changes, not all.

So at the very least, OP is not alone (this was the only mention of this phenomenon I found) and it's still a thing in current versions. I'll hit up the GitHub later though as suggested.

Posted : 15/09/2022 9:22 pm
Tom in MN
(@tom-in-mn)
New Member
RE: Blob when printer restarts after manual color change.

I solved this problem by gluing (with blue glue stick) a piece of aluminum foil over the ending spot of the previous layer before completing the filament change.  I hoped to make it easy to remove the blob but the foil thickness seems to keep a blob from forming.  Once the nozzle moves away to start the new layer, I removed the foil.  I also needed a temperature change with the color change and waiting for the temperature change, which is done at the ending spot on the previous layer, also results in a blob that removing the g-code as suggested above, can't help.

Posted : 13/12/2022 11:25 pm
James Brown
(@james-brown)
New Member
RE: Blob when printer restarts after manual color change.

I solved this by specifying 2 additional small objects with the same colors as the main object. And then move them around on the platter until one prints before it prints on the main object and the other prints after the main object. The first one acts as a purge area and second one gives it a ending spot for the color so that the blob that occurs after the filament change will always be there instead of on the main object.

Posted : 30/12/2022 9:17 am
Area51 and fuchsr liked
ZeeKay
(@zeekay)
Active Member
RE: Blob when printer restarts after manual color change.

Was there ever a issue opened for this? I couldn't find one but I have this same issue even on my brand new (single tool) XL.

Seems like quite an oversight to leave a blob on my part that just took 2 hours to print when changing colors.

Posted : 06/07/2023 8:22 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
RE: Blob when printer restarts after manual color change.

I don't have an XL, 

Colour change (M600) usually causes the printer to stop, and move the extruder to a safe place, and ejects the old filament, 
this should be removed from the extruder and replaced with the new filament, following the LCD prompts
the printer then squirts out a worm cast of purge filament as the new filament  clears the old colour out of the extruder. the printer then typically asks if the filament colour is correct... AT THIS POINT, it is tempting to pull off the waste material, and instruct the printer to continue. 
DON'T DO IT... instead, hold the wormcast of waste material, onto the build plate and then instruct the printer to continue, the printer will typically move the extruder back to the print, and it may well prime the nozzle as it goes...  tis extra prime filament will remain attached to your waste pile and pull off the nozzle as it moves. 

Failure to do this, will leave you chasing the extruder trying to catch the extra filament, or the extra filament will cause a blob on the print object. 

It is worth noting, that typically an M600 action, causes the printer to return to the exact spot where it finished printing, before the M600 command was actioned, 
this can leave a spot of the wrong colour, in the wrong place. 
If you are doing colour change by layer height, you may consider making the colour change say, one layer higher than normal, so that the extruder is already over the area where the new colour will be deposited, in which case a spot of the new colour on top of the old colour, will not be noticed. 

If you are doing colour change within an existing layer, you could consider using a purge tower and using say a piece of paper to catch the spot, before the printer moves to the purge tower(pulling the paper away as soon as the spot has happened) . (I typically do this, if I am doing labels, I print them face down and with minimum thickness to minimise waste and colour changes)

 

good luck, 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 : 06/07/2023 10:25 pm
James Brown
(@james-brown)
New Member
RE: Blob when printer restarts after manual color change.

I appreciate your suggestion and I do have a work-around. But wouldn't it make sense that at the point that you're making a color change that the first location printed after changing filament and purging should be in the new color instead of having the return point at the old color location? I make name tags and coasters and also print face down. It's just an annoyance that should be solvable in the slicer by retrieving the next location after the M600 as a return point from the gcode file instead of the current location. If Prusa does not feel it is important enough for a new feature, then I'll just fix it myself. I'm just curious. If I were using a multi-filament extruder, would it still return to the old location possibly leaving a blob of the new color? It could also be fixed by leaving the Z height above the old layer and insuring that if the next G1 or G3  command does not have a Z parameter, the previous Z should be inserted. Since I do use a Repetier-Server, I can intercept the M600 and provide the necessary coding in the server. But I shouldn't have to. Another solution may be to post process each M600 and insert a G0 prior to the M600 to move to the next location before processing the M600.

After thinking this through, you are probably right. Since I print face down, the blob of the new color will actually be behind (on top of) the previous color and shouldn't be noticeable unless it is a big blob. I actually noticed the blob a couple of years ago and I have been using a work-around since then. But I have learned a lot in the last 2 years about retraction, Z-hop, and Linear Advance. If I stop doing the work-around, I may not have an issue anymore.

Posted : 06/07/2023 11:33 pm
ZeeKay
(@zeekay)
Active Member
RE: Blob when printer restarts after manual color change.

Yeah, the two main problems are the return to last coordinate and the prime extrude. Return to last makes sense if you're replacing filament mid print because you ran out. However the color change function in PrusaSlicer is per layer, meaning it finishes a layer, does the M600, which makes a blob from the prime extrude, and goes back to the end of the last layer before starting the next one.

Sure I can edit the gcode to go to the next layer start before the M600 so that it returns to the correct place. Deleting the prime extrudes works too (thanks for the tip, didn't realize it was doing a random extrude and assumed it was ooze). But the whole logic of these lines being added in the order they are doesn't make much sense with modern extruders and speeds.

Posted : 07/07/2023 12:27 am
TD
 TD
(@td)
Active Member
RE: Blob when printer restarts after manual color change.

Can't believe this old problem has not been resolved yet. 

Posted : 20/02/2024 7:00 am
fuchsr
(@fuchsr)
Famed Member
RE: Blob when printer restarts after manual color change.

Apparently it is being addressed in the new slicer version that is in alpha 

Posted : 20/02/2024 12:14 pm
TD
 TD
(@td)
Active Member
RE: Blob when printer restarts after manual color change.

thank you, I did a test run on 2.7.2. alpha2 but the problem persists. I will try to do some more testing. has anyone tested yet?

Posted : 20/02/2024 2:42 pm
Share: