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Archive for November 19th, 2013

Dummy 9 mm Luger Cartridge: 100 μm Layers

As you might expect, changing the layer thickness to 0.1 mm = 100 μm dramatically improves the appearance of the dummy 9 mm Luger bullet on the left, compared to the 0.25 mm = 250 μm layers on the right:

Dummy 9 mm Luger cartridges - 0.1 mm layer - overview

Dummy 9 mm Luger cartridges – 0.1 mm layer – overview

The inside edge of the translucent skirt around the quartet measured 90 to 110 μm, so the layer height is spot on:

Dummy 9 mm Luger bullets - 0.1 mm layer - overhead on platform

Dummy 9 mm Luger bullets – 0.1 mm layer – overhead on platform

That required no adjustments to the M2 at all; It Just Works. Admittedly, that’s with a custom platform and firm supports replacing the springs, plus better Z-axis homing, but the overall structure was fine to start with.

I used the same Slic3r settings as before, with the only change being the layer thickness. Letting it pick the layer width might produce better results, but a 0.35 mm nozzle won’t go much narrower than 0.40 mm anyway.

A closer look at the bullet show the thinner layers provide a better rendition of the stretched sphere forming the nose; it’s less pointy than the one assembled from thicker layers:

Dummy 9 mm Luger bullets - 0.1 mm layer - side

Dummy 9 mm Luger bullets – 0.1 mm layer – side

The nose closes better with thinner layers:

Dummy 9 mm Luger bullets - 0.1 mm layer - nose

Dummy 9 mm Luger bullets – 0.1 mm layer – nose

None of that really matters for this application, but it’s a useful data point.

The downside is that printing with thinner layers requires more time: a single bullet (of 16) requires 2.2 minutes at 250 μm and (of 4) 9 minutes at 100 μm. The simple ratio of layer thicknesses predicts a factor of 2.5, not 4, but the skirt requires a larger fraction of the total time. The estimated time for a 4×4 array at 100 μm comes out at 5.2 minutes each, a factor of 2.4, which is close enough.

Although 100 μm certainly looks better, it doesn’t really improve anything for most of the blocky stuff I make…

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