Check out MAKE’s Day of Making and Maker Pledge!

MAKE Magazine (which I’ve subscribed to since it first started, and which I’m a huge fan of) has organized a national Day of Making for tomorrow, June 18th, alongside the White House Maker Faire. As part of this program, they’re asking Makers to sign on to a pledge promising to support the development and growth of a vibrant, inclusive Maker community. I’ve signed the pledge, and wanted to make a plug for it here as well: I firmly believe that “bringing the tools to the people” is one of the best ways to promote technological literacy, economic development and help nurture the next generation of engineers, scientists and artists.

Sign the Maker Pledge here!

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Disassembling the Uni Kuru Toga Roulette

As an engineer, I do a lot of sketching, and need high-quality pencils. One of my favorite is the Uni Kuru Toga Roulette, which incorporates a small mechanism to automatically rotate the pencil lead so it maintains a point. The mechanism is good for drawing (some people complain about mushiness, but I don’t find it to be a problem), great for writing, and the Roulette is a solid, well-made pencil.

Unfortunately, the Roulette is only available in a 0.5 mm lead thickness, even though other versions (like the Kuru Toga High Grade) are available in 0.3 mm. I decided to try taking apart the Roulette, to see if I could combine 0.3 mm guts with the Roulette body.

There’s only limited information on how to disassemble the Kuru Toga, so I thought I’d post this for future users. Here’s a photo of the Kuru Toga Roulette, fully disassembled:

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To take the pencil apart:
- Unscrew the silver tip from the black metal pencil body. This will reveal a black plastic tip, which can be pulled off of the pencil body.
- Grab the plastic section of the pencil body, and pull it away from the metal knurled section. This may take some force/twisting. It will eventually slide off of the polished metal section. The actuator plunger for the pencil (the plastic clicky part, for lack of a better technical term) will remain attached to the plastic section, and a spring will fall out of the section.
- (Hard Part) Unscrew the polished metal section of the pencil from the knurled metal section. This requires some force (since there’s some type of glue/thread lock between the components), and is not easy to do without marring one of the components. I held the knurled section in a collet in a lathe, grabbed the polished section in the tail stock chuck, and then gently twisted them apart by hand.
- Once you’ve done this, the plastic “guts” of the pencil – the lead carrier, the rotation mechanism, and the clutch – should fall out of the knurled barrel easily.

And that’s it! You can now reassemble any combination of Kuru Toga parts you’d like.

More 3D-Printed Thermoforming

Recently, I’ve been playing around more with 3D-printed thermoforming tools. After having some limited success earlier in the year making 2-part thermoforming molds using SolidWorks’ mold tools, I decided to try something a little more complex: a 3-part mold, incorporating a spring-loaded pinch plate. By pinching the sheet against the upper half of the mold, the pinch plate is intended to allow heated plastic sheets to be directly placed in the mold, without needing a custom frame.

Some images of the prototype mold:
- Hot off the printer:

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- Mold Parts:

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- Mold and product:

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I tested the mold with .030 scratch-resistant acrylic (hard to form) as well as .020 and .030 clear PETG. Some lessons learned:
- The pinch plate concept only works passably. The compressive force provided by the springs I included isn’t consistent across the pinch plate, and the guide pins require me to punch holes in the plastic sheet or shape it strangely, making the tool less easily adapted to different plastic sheets.
- Additionally, heating thermoforming sheets without a frame isn’t reliable. It seems to work acceptably with Kydex, but both the acrylic and PETG tended to curl or warp, especially when there were holes or uneven cuts in the material.
- Finally, this particular mold had a few issues that are particular to it. The part I was trying to form is a straight-sided cup, which has a very low draft angle (0.5 deg), leading to a lot of friction between the mold and the sheet during the press. Additionally, the core tool was printed with a 10% infill, which is too low for this particular geometry – the protruding part of the core compressed significantly, around 3-5 mm, before the two halves of the mold met. The cup that was produced looks nice, but is consequently about 5 mm too short.