Cura 4.0 beta not purging 1st color

[Steverc1572 3]

I have noticed that on a 2 color file that the 1st color swap that it does not go to the prime tower and purge the 1st color. It works fantastic on the 2nd swap and on. I have to add a brim large enough to purge all the old color out or it will contaminate the other color on the 1st swap. Has anyone else noticed this problem? This may be specific to a 2 in and one out nozzle. This is on a Creality CR-X.

[almannaei 0]

hi Steverc1572  I have the same issue with my Creality CR-X ,it prints great single color but when using dual extrudes mode ,its exactly what you talked about 

[nallath 630]

Well, we've had no such reports for any of the dual Ultimaker printers, so I'm guessing it's a profile/configuration issue. Since we don't actually maintain the profiles of third party printers (we only check if they don't break anything in Cura, not if they actually produce decent prints), there is not much I can help you with. 

[Steverc1572 3]

On 1/21/2019 at 2:32 PM, nallath said:

Well, we've had no such reports for any of the dual Ultimaker printers, so I'm guessing it's a profile/configuration issue. Since we don't actually maintain the profiles of third party printers (we only check if they don't break anything in Cura, not if they actually produce decent prints), there is not much I can help you with. 

The only problem with that is I installed the exact same profile/configuration in 3.4.1 and it works perfectly. Not sure what has changed and I understand that you concentrate mainly on Ultimaker printers but something has.

[PaulK 9]

On 1/21/2019 at 3:32 PM, nallath said:

Well, we've had no such reports for any of the dual Ultimaker printers, so I'm guessing it's a profile/configuration issue.

 

Well, the UM doesn't need to purge the head on color swap, so it is a different problem set. If I read it correctly, he is using a dual-in head with a single nozzle. That would mean it would require more then the math to change, but have different g-code then would be generated with a full dual head machine like the UM

[beckbw 0]

I've noticed 3 things impacting CR-X dual printing with Cura 4.0.0 Beta (OSX):

1) Extruder Start/End Gcode isn't inserted on tool change. My workaround was two post-processing scripts, which is kludgy but works fine. Through trial-n-error I figured out that retraction on Extruder End Gcode needs to be more than -60 mm (Creality recommends -80) and re-priming after tool swap needs to similarly be >+60 (I used +80 again).

2) The default prime-tower-volume is WAY WAY too small to purge between tools. I had set it to >80 mm3 on each extruder and 90 might be safer. (FYI, I use a 30 mm circular tower). For reference, S3D profiles seem to use 91 mm3.

3) the tower often topples over so I use a brim whether I need it or not for the tower.