Unable to get a smooth transition when changeing color at height

[Raymond Bakken 0]

Hi there

 

I am trying to change color at a spesific layer (height), but I have a problems that after the "pause" the printer feed out filament just before it wants to start printing again, makeing my print ugly.

I am working with Ultimaker Cura (versjon 3.2.1) and ultimaker 3 Extended (version 4.0.1.20171023).

 

I have tried a lot of options to prevent this. Among Post processing Scripts: "Color Change" and "Pause at height". without any luck.

 

I am now trying to "hack" the gcode manually (the attached photo is from 2 attemt of hacking gcode).

The two best results are in fact at the attached photo, but you clearly see that there has been feed to much filament at the "t".

 

Strange things happened when I hacked the gcode.

Somewhere at the normal code:

• ...
• ;LAYER:18
• G0 X128.604 Y103.191 Z2.07
• ...

Hacking attemt 1

• ...
• ;LAYER:18
• M0; A break for changeing filament (my hacking)
• G0 X128.604 Y103.191 Z2.07
• ...

Hacking attemt 2

• ...
• ;LAYER:18
• M0; A break for changeing filament (my hacking)
• G1 E-5.000000 F1500.000000; pull back filament 5mm (Also my hacking)
• G0 X128.604 Y103.191 Z2.07
• ...

 

At attemt 1:

1. The printer stops, and goes to a fine posistion for changeing filament. I belife also it cools down the print head(s) because they need time to heat up again when I want to change filament.
2. I change the filament and I press the resume button.
3. The printer starts to extrude some filament while it moves towards the print, and even on top of the print it extrude filament. I try to take away as much as posible, but when the build plate gets to close to the print I am unable to proseed. The rest of the exsess filament gets attached to the print (as you can see in the photo).
4. It waits (propably for printheads to heat up), then it starts to print normally.

 

Attemt 2:

Same as attemt 1 on 1. 2. and 3.

And then:

First then it retracts the filament, but then it is (obviously) to late. And in adittion it retracts filament back almost half the guide tube. And then again it feeds filament back in the extruder.

After that (and waiting for preheating) it prints normally again.

 

What is the best solution when you want to change color at a specific layer, without exsess filament that destroys your print?

And why does the printer react in this way? It seems so unpredictable (regarding what I expected in attemt 1 and 2).

 

Regards

Raymond