Thing-O-Matic: Hole Thread Separation

Even after printing nice calibration objects, real-world projects sometimes don’t come out quite right.

This set of fairing plates for my Esteemed Wife’s bike was a test case to see if the hole threads would stick together better than before. As it turned out, no, they didn’t:

Upper mount - hole separation
Upper mount - hole separation

The Infill w/t=1.75 setting seems to be slightly too high (meaning Skeinforge thinks the threads occupy slightly more space than they actually do), so the top isn’t quite as nicely packed as it should be.

The threads around the holes aren’t sticking together at all. A closer look:

Hole details
Hole details

The first layer of the upper-left and lower-right holes didn’t adhere to the ABS covering the aluminum plate and tangled with the remaining layers. In various combinations: the perimeter didn’t bond to the extra shells, those shells didn’t bond together, and the fill didn’t bond to the shells.


  • Infill overlap = 0.3
  • Infill solidity = 0.25
  • Infill w/t = 1.75
  • Feed = 40 mm/s

I could dial back the perimeter feed ratio a bit, but that won’t affect the infill-to-shell problem. Adhesion to the build plate depends critically on the initial height of the first layer and the speed of the nozzle across the plate; those I can adjust.

Another mechanical cause: slightly loose drive belts. That usually shows up as backlash causing oval circles, but for small circles a pair of loose belts might just produce a too-small circle. I’m about to take the whole XY stage apart for another purpose, so adjusting the belts will come naturally.

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