Stepper Extruder Calibration Objects: Barbie Style

After a few ranging shots, I printed coasterman’s calibration set. Much to my surprise, they came out very nicely… after the obligatory bit of tuning.

Everything printed at 40 mm/s, 0.33 mm layer thickness, 220 °C first layer / 210 °C all other layers, 120 °C aluminum platform. The first layer prints at 25% of normal speed/feed atop an aluminum plate covered with a thin layer of ABS. I’m still tweaking temperatures, first layer speeds, and ABS thickness on the plate.

All the pix have been contrast-stretched and lightly sharpened to bring out the detail. You’re going to start seeing a lot of Barbie style objects, because I want to use up that pink filament, OK?

The single-wall open box has an actual filament width of 0.55 mm, suggesting a w/t of 1.7. The Cool plugin throttled the speed down to 15 sec/layer and it’s just about perfect.

Calibration - Thin wall box
Calibration - Thin wall box

Here’s what it looked like in progress:

Calibration - Thin wall box - extruding
Calibration - Thin wall box - extruding
Calibration - 50 mm tower
Calibration - 50 mm tower

I simply didn’t believe the 50 mm tower would print until I saw it emerge intact. This is with 2 extra shells and 25% fill, at 15 sec/layer. The suck-in along the right edge comes from laying down the perimeter shell before doing the fill: that’s where the nozzle departs inward after finishing the perimeter. The distance to the fill was less than the Reversal threshold, so the stepper extruder didn’t reverse.

A few passes with the perimeter width/thickness tester resulted in a block that fits into the slot all eight ways with w/t=1.75 (with some orientations, mmm, much tighter than others, I’ll admit). The fill w/t=1.5 is obviously too low, because the top layer got overcrowded even with 25% fill on the internal layers.

The suck-out at the left corner shows where Reversal starts inhaling filament on alternate layers.  This was with 35 rpm and 100 ms, which seems too aggressive. It’s not bad-looking, mind you; I touched up the sides of the block with a bit of sandpaper to smooth out the tallest ridges.

Calibration - Perimeter Width
Calibration - Perimeter Width

The second classic 20 mm solid box looked good at w/t=1.75 and fill w/t=1.65, apart from the corner that pulled off the ABS and grew a tab that messed up half the layers. That’s what caused me to junk the ABP; about which, more later. The first one came out with the top looking a bit thin at fill w/t = 1.75.

Calibration - 20 mm solid box
Calibration - 20 mm solid box

The first hollow box just didn’t work at all, because setting w/t=1.75 built a single shell wall and the overhung top didn’t connect to the walls.

Calibration - 20 mm hollow box - failure
Calibration - 20 mm hollow box - failure

Changing to w/t=1.5 produced a reasonably good result, although the lid didn’t quite attach to the walls across the long diagonal. I always drop a scrap ball bearing inside to prove it’s hollow in there.

Calibration - 20 mm hollow box - success
Calibration - 20 mm hollow box - success

The Oozebane tests looked great, even though I’m not using Oozebane: a stepper extruder pretty much eliminates the need for that plugin. The front one had a few strings at 85 ms / 75 ms, the back one was clean at 100 / 75, but the fill got strangely thin.

Calibration - Oozebane test
Calibration - Oozebane test

Skeinforge 39 handles bridge layers oddly: no extra shells, fill parallel to one axis, and I really didn’t have it set up right. The holes look OK, albeit with poor contact with the fill.

Calibration - Precision - top
Calibration - Precision - top

The aggressive overhang didn’t work at all, but the 45 degree slope looks passable if you’re not too fussy. Small overhangs may be OK, but you really can’t do them without support material underneath.

Calibration - Precision - bottom
Calibration - Precision - bottom

All in all, the combination of a stepper extruder, spring-loaded filament tensioner, and an ABS-coated aluminum platform seems to produce good results. Maybe I can finally start printing useful objects…

However, as we all know, cranking out good calibration cubes doesn’t guarantee anything else will print the same way…