Advertisements

Archive for May 26th, 2011

Thing-O-Matic: Companion Cube Print Quality vs. Speed

Companion Cubes* being nice handouts, at least in certain circles, I printed three arrays of nine. This being an opportunity for Science, they’re printed at 25, 40, and 50 mm/s, all with 100 mm/s moves.

Cube array - 25-100

Cube array - 25-100

They’re scaled to about 16 mm on a side, making them about as small as anything you’d want to print. With a 0.66 mm extrusion width (0.33 mm thick and 2.0 w/t, they’re only 24 threads wide, which doesn’t allow for much detail. Here’s the top of one printed at 25 mm/s:

Cube top - 25

Cube top - 25

And at 50 mm/s:

Cube top - 50

Cube top - 50

Obviously, the faster cube turned out uglier. The 40 mm/s cubes look a whole lot like the 50 mm/s ones, which means the best printing quality occurs well below that.

The front at 25 mm/s:

Cube front - 25

Cube front - 25

And at 50 mm/s:

Cube front - 50

Cube front - 50

The odd shadows on either side of the central bump become more obvious at an oblique angle. At 25 mm/s:

Cube front oblique - 25

Cube front oblique - 25

And at 50 mm/s:

Cube front oblique - 50

Cube front oblique - 50

This confirms a suspicion I’ve had for a while that the XY stages don’t have the positioning accuracy required for this level of detail when printing at any reasonable speed: they tend to oscillate slightly after changing position. I think acceleration limiting would help this, but I have no way to prove that. I know a more rigid mechanical assembly would help a lot, but there’s no way to get there from here.

Obviously, slowing down will improve the overall quality. I’m printing at high speeds to see what goes wrong; I have no objection to reducing the speed to a crawl in order to wring the best quality out of the hardware.

Moving at 100 mm/s, however, definitely reduces the opportunity for ooze. Even with Reversal, sometimes the nozzle dribbles a bit and very fast moves tend to produce a hair-fine thread that’s easily removed from the finished object. In this case, all three sets of nine cubes printed with no threads at all.

These were printed with Reversal set to 25 rev/min, 110 ms in and out, and no early motion. That eliminates suck-out as the extruder reverses while the nozzle approaches the end of the thread, but still leaves a zit at the endpoint where the nozzle moves to the start of the next thread:

Cube rear oblique - 25

Cube rear oblique - 25

The zits appear identical with faster print speeds, so they don’t depend on anything other than Reversal.

The other two sides of each cube look about the same.

For completeness, here’s the bottom at 50 mm/s:

Cube bottom - 50

Cube bottom - 50

Comparing that with the top suggests that Skeinforge used bridging fill, rather than surface fill.

(*) They’re actually Weighted Storage Cubes, as they lack the hearts found on Companion Cubes. My Shop Assistant asserts that if you cuddle them enough, they’ll grow hearts…

Advertisements

26 Comments