Multi material print

  • Every so often I get my jollies by frustrating the hell out of myself with a multi material setup. The last week was spent on such a fools errand and I thought that maybe I could run this issue up the flag pole and see what the fallout is.

    The setup is a Chimera clone setup with two volcano hot ends, one is set up for PLA and with a 0.8 mm nozzle and one is set up for petg with a 0.4 mm nozzle.
    For the purposes of this question, let's assume both are 0.4 mm nozzles.

    The model in question is one half of a 1.5 inch cable clamp so basically a half circle. I would like to print it with support in the middle where the half circle basically runs horizontal.

    I can print this item with support as a single material print, either PLA or PETG and it prints just fine but of course has crappy finish in the area where the support was peeled off.
    I run 0.1mm layer height and let's say 0.2 mm between support and the actual model.

    I have this now set up (with Cura) to print as primarily a single material with the second material being used as a separation layer between the support and the model. I have the support roof set up as 100% density so I am expecting to see the bottom of the model to basically look like a copy of the 100% support separation layer.
    I have tried PLA as the main material with PETG as the support separation layer as well as the other way around. I have separation of the model to support set to '0'.
    What I get is a very crappy layer that is filled with holes and mangled material in the are where the support is located.
    I should add that this supported area is fairly small, maybe 10 square millimeters.

    Anyway, what I see in Cura's preview window is perfect and what I see when the model is printed is an unusable piece of crap.

    After lots of swearing, I bounced this issue by a friend and he suggested that maybe the PLA and PETG end up inter-mingling causing a layer of some mutant crap.

    I know that PETG with PLA (or the other way around) is not an officially supported separation material but the two don't seem to stick to each other too well so it should (in theory) work. This was confirmed by reading what others have posted on the internet.

    So the question is, why am I getting crap? WIth zero separation, does one material mix with the other material? Should I have a separation zone rather than having zero separation? Should I crank up the parts cooling fan for either Petg or PLA? I am running the PLA at 195 and the PETG at 235.

    What am I missing?
    How do other people use separation layers? Any special trick ? Is it only because I am not willing to pay three times the money for the 'approved' separation layer material ?

    Thanks in advance!

  • Moderator

    @jens55 said in Multi material print:

    Should I crank up the parts cooling fan for either Petg or PLA?

    I think I'd want the cooling fan on for the separation layer for sure.

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