Friday, April 15, 2011

Extruder Hot End

The hot end of the extruder is working. I can successfully melt ABS (thanks Neil!), I still need to make something to push the filament through it. I'm using old-school MakerBot technology right now: a Mk3 heater barrel, nozzle and thermal barrier. The heater is driven by their PWM board and temperature monitored by their thermistor board. All this was bought a couple of years ago, so it’s now a couple of generations old :-)

My test sketch in my Arduino uses the PID library to keep the temperature constant.  Once the temperature was stable I pushed some 1.75mm filament in, and eventually I got some ~0.5mm coming out the bottom. It took quite a bit of force, but it did work. Next step: the extruder motor.

Wednesday, April 13, 2011

RepRap Progress

I have all four stepper motors connected mechanically (this design, just like the Prusa Mendel, uses a motor on each side of the Z axis) and driven by EasyDriver boards. I built carrier boards with screw terminals for the motor connection and 12V supply and a 10pin shrouded header to connect to the RepRap motherboard – I used the same pinout as the standard RepRap, no need to reinvent. I wrote a test program to move every axis back and forth one revolution and they all move. OK, I haven’t put the Y axis conveyor belt on yet, and the X axis belt slips. But still....

I then tried to install one of the various firmware packages so I could test more complex patterns that just a diagonal line between opposing corners of a cube. Unfortunately my Arduino sports a 168, which is too small for any of the packages (even Teacup, despite what they claim). I've ordered a 328 from Adafruit, which will double the amount of flash I can use. I will eventually need to buy an Arduino Mega or Uno, but for now I'll get by with a $6 upgrade.

So I've started working on the extruder, which will need it's own controller (so my existing Arduino will not go to waste). I finally managed to get my thermistor and Makerbot temperature sensor board working (more) sanely. And I found some teeny tiny butt crimp connectors to join my NiChrome wire together. This means that I should have a hot end. Now I need an extruder to push the filament through the hot end. But progress nonetheless.

I will be doing the mechanical construction of the hot end today, and maybe try to energize it too (trying not to burn my fingers, literally).

Sunday, March 20, 2011

Polyhedra Construction Kit

When I was building the Valentine’s Dance decorations I thought a tab-A-in-slot-B type of construction would be cool for polyhedra. This idea has been stewing in my mind for a month or so, here is the prototype for a polyhedra construction kit. I will have triangles, squares and pentagons with common edge lengths so you can build whatever polyhedron you wish (although I think you are limited to convex polyhedra, because these pieces are chiral). I started with triangles because they’re the easiest to cut out. I used SymmetriSketch to draw what I thought would be an interlocking edge style. Then I printed it out and glued it (a glue stick works great) to some aluminum flashing, then cut out the aluminum with snips. This became a template for cutting out recycled HDPE from the sides of 4L milk jugs. Then I lightly scored where the folds would be.

I didn’t have enough faces to do a full icosahedron, but I managed to put 5 together. I had to use tape as the faces did not have positive locking as I hoped. That’s what prototypes are for, though. I then tried a tetrahedron, with tape on the outside. It really didn’t want to stay together.

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For the next prototype, I am going to create a slot and tab on each edge instead, so there will be locking on both ends of the edge (right now these faces want to twist apart). Actually, V2 would look very similar to SlideTab (ok, exactly like). In fact, here is the PDF of what I had in mind. So, no need to do a V2 prototype, proceed directly to making the polyhedra.

Hmm, I wonder whether the laser cutter at the makerspace can cut HDPE?

Note to self: drink more milk.

Saturday, March 12, 2011

1x2 RepRap

I've been trying to build a RepRap for quite a while now. The problem is that to make its parts you need to print them on a RepRap — a bit of a bootstrapping problem. Then I started to work on a RepStrap. I've done two designs based on the Contraptor system, never getting full X-Y-Z control. I always got stuck on how to control the Z axis. I had been planning on building an SAE Prusa Mendel, carefully building the printable parts out of wood, but recently I saw the 1x2 RepRap posted on Thingiverse. It’s very similar to a Prusa, with some advantages:

  • all connectors are made of wood
  • all 90° cuts and holes
  • non-metric hardware
  • hand-made drive belts
The only tools you need are a drill press and a hand saw! 

Contraptor used 1/4" threaded rod (which is flimsy), this RepRap uses 5/16" (also very close to the 8mm of the official metric RepRap); the Contraptor system uses NEMA 23 stepper motors (large), whereas I have NEMA 17s. Coincidentally the 1x2 RepRap uses them too! And finally, working in wood is a lot faster than working in aluminum. 

So here's an out-of-focus picture of what I have so far. I need to order at least one more stepper motor before I can get full X-Y-Z control, but I can move all axes by hand right now.
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Monday, February 28, 2011

Day 28: Light table from scanner enclosure

We had an ancient SCSI-1 scanner lying around, from which I had already scavenged all the good bits, so all that was left was the enclosure. I realized that a little light table would be a handy thing to have, so voila:

Small light table from ancient SCSI-1 scanner enclosure.

It needs some frosting on the glass, and another light (Canadian Tire didn't have enough sockets). But it's good enough (for me) to finish off  Thing-A-Day 2011.

Friday, February 25, 2011

Day 25: QubeRs

Here is my latest artwork. I call it “QubeRs,” it’s 144 cubes that can be assembled into (small) QR codes. Each cube has the 6 possible combinations of 4 black and white pixels on it. One could also use these blocks to do B&W pixel art (welcome to the 1980s!)

I originally wanted to call this the “QR construction set,” but QubeRs sounds cooler.

Some assembly required.

Thursday, February 17, 2011

Day 17: Oblique Strategies Deck

I've been wanting a physical Oblique Strategies deck (by Brian Eno and Peter Schmidt) since I first heard about them. I used to have a Palm app that would give you a random strategy from the deck, but I never used it because the physical experience was lacking. The idea of making my own has been running through my head for months, but I couldn't find the right weight of paper to use. Inspiration struck, and I've been working on this deck since Monday. I used a double-blank deck of cards from Murray's Trick and Joke Shop, although I really wanted to use two blank-faced decks (they were sold out). I whittled the 3rd Edition down to 104 strategies and then transcribed them onto the deck.