CupCake Wants a Heated Build Chamber

I’m doing fairly well printing on my CupCake now that I have (1) my heated build platform (2) levelable with (3) a bearing-supported axle on my filament drive motor. Still need (4) a stepper filament drive and (5) roller-bearing X-Y guides.

My workshop temperature has been pleasantly cool for humans lately (currently about 67°F). The heated build platform keeps the first layer from shrinking and pulling up off the platform; but at 67°F ambient, upper layers shrink also and deform the build.

Uneven shrinkage of ABS plastic object printed on MakerBot CupCake

I’ve been combating upper-layer shrinkage by leaning things against the openings in the CupCake walls while printing; it traps the heat of the build platform and significantly reduces the shrinkage.

Here you can see shrink in early layers from the front of the CupCake being open while I was removing the test extrusion before the print (long recovery time for the build platform to reheat the chamber) and dramatically less shrink in the upper layers (because eventually it recovered after I blocked the front with my laptop screen). It doesn’t take very high temperatures to reduce shrinkage.

(The bottom of the object is shiny from the heated build platform, doodled with a marker for revisions, and holding a screw as an experiment with acetone and mounting boss thread durability.)

I’m (still) thinking of cutting acrylic pieces to cover the CupCake’s windows. The challenges are

  • How best to attach the acrylic for easy removal for service? Hinges? Magnets?
  • How to route the heated build platform cables out the back window so they don’t snag? Maybe I should rotate it 90° CW and bundle them with the Y drive and X-Y endstop cables?
  • How to remove the test extrusion before printing? An auto-scrubber would be lovely, but in the short term I might get a loooong tweezer and leave an access hole in the front window, biohazard gloves sandblaster style.

Why Does It Do That?

The ABS all cools to room temperature eventually (okay, we could talk asymptotes, but I’d rather not), but it appears that only rapid cooling makes it shrinkalot. Interesting, n’est-ce pas?


Devil bunny needs a ham.

3 Responses to “CupCake Wants a Heated Build Chamber”

  1. Robert says:

    I’d think about Velcro(tm) tabs to fasten the “windows”. Put one “fuzzy” tab on each corner of the window and one “scratchy” tab on the corners of your cupcake’s openings (sounds dirty). Quick and easy removal of the windows and no drilling of acrylic.

  2. Stephen Hill says:

    Heavy clear vinyl sheets, velcro’d at the top and just hanging down over the openings? Then you could just lift it up to reach in the front to clean off the test scrap.

  3. Edward Wingate says:

    Foam core board cut exactly to the window size should press fit in and do the trick.

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