Stretchy Bracelets

Inspired by some similar designs, I designed a pair of customizable bracelets. They get their flexibility from their many folds. Even printed in relatively brittle PLA (the brown material), the small amount of flex that can be coaxed out of each kink adds up to make the whole thing pretty elastic. The blue material is a PLA/PHA compound that is even more flexible and durable.

Posted on Thursday, April 24th, 2014.

Shadow Casting Photo Panels

I designed a customizable thing that converts a photo to a printable panel. The size of each pixel in the panel varies according to the brightness of the corresponding pixel in the image. The pixel shapes are connected and held in place by thin strips, kind of like beads on a string. The idea is that when viewed at a distance, or as a cast shadow, the connecting strips are blurred and the image appears more clearly. Here’s the picture of me I printed as a test:

The script isn’t very efficient – it evidently takes hours to process images much larger than the icon-sized 20×20 default – but it is rewarding to see people use it nonetheless. Here are two beautiful examples, both modified to print higher resolution images:

Posted on Monday, April 7th, 2014.

F-86

Today I printed this airplane model designed by Dolf Veenvliet, based on the F-86 Sabrejet.

Thanks to my dad for the link. My grandfather’s unit, the Boys from Syracuse, flew the F-86. Today was his birthday.

Posted on Wednesday, March 26th, 2014.

Bézier Bowl

One more vase-type-thing: a customizable “Bézier bowl”. It produces models by rotating a cross section around an axis, just like my chalice lathe. The difference is that instead of drawing the cross section directly, you draw control points to define the path of a smooth Bézier curve.

Bézier curve tools are found in many drawing programs. Normally they feature a live preview of the line with interactive handles for the control points. Since the Thingiverse drawing widget wasn’t exactly designed for this sort of [mis]use, a bit of imagination is required to visualize how the customizer works. I annotated this screenshot with labels and the correct Bézier curve overlayed with Inkscape. It’s linked to a video clip showing the customizer in action:

I printed the bowl shown in that example. It was the first thing I’ve printed with ColorFabb woodfill, a filament composed of conventional PLA infused with wood fiber. (I got mine in a sample pack from Printed Solid.) Here are the results:

I had some trouble getting started with the woodfill because it is much runnier than regular PLA. As a result, it really oozes out of the extruder when idle, and seems prone to jamming/clotting if not extruded continuously. However, after increasing retraction (to compensate for ooze during travel moves) and boosting print speed (to keep up with the flow), it prints quite reliably.

The finish is pretty remarkable, too; definitely woodlike, but of course with an artificially uniform fine grain. Thin-walled woodfill objects almost feel a little unearthly – like wood to the touch, but translucent and feather-light.

Posted on Wednesday, March 26th, 2014.

Printrbot Tensioner

As a followup to my post about making printable models from PDF part diagrams, here is a replacement Printrbot tensioner I made using that method. (The original did not need to be replaced; I just chose this part as a simple test case. It’s working great.)

The original tensioner is assembled from two laser-cut wood parts, numbered 21 and 22 in the Printrbot Simple’s diagram. I exported the patterns per the process described in the post linked above and combined them using the following OpenSCAD script. Note that part 22 has a partly recessed socket for a hex nut, which I exported separately.

module part_22() {
	difference() {
		
		// Part 22, with bolt holes
		linear_extrude(height=6) import("part-22.dxf");
		
		// Subtract the hex nut socket from part 22
		translate([398.15 - 394.29, 525.66 - 489.21, 3])
		linear_extrude(height=3) import("part-22-hex.dxf");
	}
}

module part_21() {
	// Part 21, not including hole through which 22 goes
	linear_extrude(height=6) import("part-21-solid.dxf");
}

union() {
	part_22();
	translate([0, 36, 458.88 - 462.4]) rotate([90, 0, 0]) part_21();
}

The parts are aligned using positions reported for each feature in LibreOffice. The actual position on the page doesn’t matter; only the difference between them is used to get things centered.

The STL exported from this script could be used to make an exact replacement for the original assembly. Instead, I imported it into SketchUp using the SketchUp STL plugin and made a few changes to simplify the part and make it easier to print without supports. This is the final version published on Thingiverse.

Posted on Tuesday, February 11th, 2014.

Mystic Crystal

Printed a sphere inside a tiny cube. How cool is that?

With this plain translucent plastic, the inner contours are visible when the object is backlit. I think this has pretty cool artistic potential.

Posted on Wednesday, January 29th, 2014.