Dual extruder questions - trying to figure out logic

  • I am trying to learn dual extruder operation. I designed a simple square little sign. The bottom layer is background colour (white) and is a solid print. The next layer is black and has the word 'World' cut out of the solid layer. The last layer is white and only has the word 'Hello' (just the letters, nothing else).
    The end result is a sign with the word 'world' in white seen through the cutout in the black layer and the word 'Hello' printed in white letters on top of the black layer.
    When I used the term 'layer' above, each layer consists out of multiple print layers.

    I am using Cura and I have configured the model with a brim and the white extruder is configured to print the brim. The use of a priming tower is selected.

    What I get is the white brim as expected, then the printer goes to the prime tower location and prints a white brim even though the option of a brim on the tower is deselected.
    It then goes back to the model and prints the bottom in white as expected and this is where I loose any understanding of what happens next.
    Shortly after the bottom of the model starts printing (this is happening with the second extruder), The printer heats up the first extruder (black). It does so way early and I have modified heat up and cool down settings without being able to modify the fact that heating start way early. The result is contamination of the current layer.
    Now the next thing that then happens is that a black outline is printed around the brim of the model, a black outline is printed around the brim of the tower that isn't supposed to even be there and then the printer decides to print the tower bottom in black .... wtf ???
    I have been unable to find any setting in Cura that would override the tower adhesion layer to be the second extruder and I find it odd that I can choose the brim extruder but not the extruder for the bottom. There is a top/bottom extruder but that doesn't change the extruder used to print the prime tower floor.

    So, my two questions are .... what setting controls the prime tower floor extruder and what setting do I have to adjust in Cura to delay the onset of heating of the next used extruder.

    Bonus question: When my little sign is shown in the Cura preview, all looks good but when I look at the simulation, the 'e' and 'o' of the word 'Hello' (white letters sitting on a black background) are filled in but the 'o' in 'World' is printed as it should be with black in the middle.

    OK, so yet another bonus question .... what is the best way to have the printer wait, after the nozzle change, for the just inactivated nozzle to cool down before it continues printing (to avoid contamination) .... is putting a 'wait' command in tpost0.g and tpost1.g the best way to do this ?

  • The first bonus question has been solved .... under 'Mesh fixes' in Cura one must disable 'remove all holes'. It must have been active as a default at some time because I never changed that setting before.

  • Success on the heating up part of the question .... turns out that I was too careful when I adjusted the heat up and cool down figures. When I put in nutty figures like 20 degrees per second it makes a difference. I thought 5 degrees per second was nutty (actual is more like 1.5 - 2 degrees per sec) but it just wasn't nutty enough. I just need to dial it in now.

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