Filament Colour Change Issue

[ReToxD 0]

Hi, I am using Cura 4.11.0 and a Bibo 2 dual nozzle 3D printer.

For the part I am printing I have a base and then letters on top of the base, with the base in black and the letters in green, using a purge tower to stop colour leakage. 
I have split the base and letters in to 2 parts and selected a different extruder for each part. The problem is I can't seem to do the infill for each part with the same colour as the layers around it. Well, the base is all black but then the letters have green walls but black infill, and this takes ages due to the nozzle having to cool down and reheat each time the colour is changed. (This is if infill extruder setting is set to not overridden)
Unfortunately it won't let me select nozzle 1 for the base then nozzle 2 for the lettering as the setting is linked to both extruders.

Is there an easy way to get around this problem? I thought there would be an option for change extruder at height/layer? But none of the scripts seem to do that either.

Any help would be much appreciated! 



 

[GregValiant 1,408]

I don't have a dual head printer but I have configured one in Cura to play with.  Each extruder has it's own settings and you must go through all the settings once for each extruder. 

Next to the settings search box is an icon with 3 lines.  Click on that and set visibility to "All".

Select the part you want to print with extruder 1, select extruder 1, go through all the settings.  Select part 2 and extruder 2 and go through all the settings.

Specifically I think your "infill extruder" settings needs attention but it's hard to tell from afar.

 

If you use "File | Save Project" and post the resultant 3mf file here maybe it will show something.

 

[ReToxD 0]

OK, I realise looking again that when infill extruder is set to not overridden it will do the infill correctly but the prime tower stops after the base is completed which leads to the base colour seeping in to the lettering.

Unfortunately it seems that the infill extruder settings are linked between extruders so I can't select each extruder to do the infill for each part.

I have attached the 3mf file for you to take a look at. 

B2D_RetoxD Logo.3mf

[GregValiant 1,408]

"...which leads to the base colour seeping in to the lettering."

That's one I never heard of.

It appears that the prime tower ends because there are no further color changes above layer 26.

What you are doing is really no different than when using Pause at Height to change colors.  I've never gotten "seepage" of one color into another with either PLA or PETG.

One thing I have done is to allow the base color to continue to one layer of the lettering (in your model I would have layer 26 be black and change colors for layer 27).  That insures that the second color will not be dragged across the top of the base resulting in (in your case) green scars across the black base.  Nobody ever notices that the bottom .2mm of the letters is the base color.

Using the "Per Model" settings for the lettering, and setting the Bottom Layers to "0" will result in layer 26 being just walls and infill instead of a full bottom surface on your base top surface.  That will result in much less heat being applied on top of the base and may mitigate the "seeping" you have.

Another thing you can try is to turn "Combing" off.  That will keep the print head within the letters (except for the travel moves between the letters) as opposed to traveling over the base to avoid the letters.

Edited October 1, 2021 by GregValiant

[ReToxD 0]

3 hours ago, GregValiant said:

It appears that the prime tower ends because there are no further color changes above layer 26.

That makes sense I guess, wouldn't hurt to have the option to continue to top though as I feel this would of saved my last print (see pic attached)

 

3 hours ago, GregValiant said:

One thing I have done is to allow the base color to continue to one layer of the lettering (in your model I would have layer 26 be black and change colors for layer 27).  That insures that the second color will not be dragged across the top of the base resulting in (in your case) green scars across the black base.  Nobody ever notices that the bottom .2mm of the letters is the base color.

That's a good idea, only problem is I can't seem to see a way to change extruders at height/layer. The pause at height only works for manual filament changes I think? 

 

 

4 hours ago, GregValiant said:

Using the "Per Model" settings for the lettering, and setting the Bottom Layers to "0" will result in layer 26 being just walls and infill instead of a full bottom surface on your base top surface.  That will result in much less heat being applied on top of the base and may mitigate the "seeping" you have.

I will try that too. Thank you 🙂 

[GregValiant 1,408]

Yes, Pause at Height is for manual filament changes.  You could do that, but then I saw that last picture.  I have no idea how black could have gotten into the green extrusion.  What color was the infill in that area?  Strike that.  Infill runs up and down and that color intrusion looks to run with the layers.  You have black a few mm's above where the black extruder stopped being called upon.

I can't recall how many walls you had in that file.  I generally consider 3 to be a minimum.  And then I looked at the picture again and 6 may not have helped.

The green looks to have intermittent under-extrusion.  Are you confident in the Estep calibration of that extruder?

I'll think on this some more, but right now I'm kind of baffled.  The gcode I generated looks fine.  The green extruder could not have put down black or been somehow contaminated.  It must have picked up the black from somewhere so I guess the question should be how and where from?  A likely suspect would be a blob of black it picked up on the purge tower and it took a while to ooze down the outside of the nozzle and make it into the print.