Tuesday, May 31, 2005


Finned extruder

As you can see in the photo below, I've looked at the possibility of using fins to keep the entrance end of the Polymorph extruder cool. I got the idea off a gas-powered soldering iron pictured on the right. The 12mm aluminium cylinder has fins carved half-way through. These were made by rotating the cylinder in a power drill and hacking away with a large hacksaw.

Heating the cylinder up to 180C with a soldering iron resulted in a 10C temperature drop across the fins. Further experiments will use more fins, wider gaps between them, and some form of variable power supply for the soldering iron. We'll need at least 60C of temperature drop across the fins in order to reach the extrusion temperature of 120C Adrian was using without prematurely melting the incoming Polymorph.

The new AS5040 magnetic sensor samples from Austriamicrosystems arrived today, and let me say that these people really know how to provide sample kits. They even provided a small, battery-powered demonstration board with the samples and a little magnet. Vielen dank, guys!

Vik :v)

You guys got a plug on fark.com, so there may be a few more visitors now. Great work, BTW. I own some polymorph and I actually made a plastic key to my home with it. I may be posting again soon.
Great work guys. I read the full report on the silver paint circuit and I can't help but wonder if there would be a way to use a metal impregnated polymorph material as the circuit traces, allowing the EXACT same extrusion process for both the insulating and conducting structures. I know there are some conductive plastics out there for ESD protection although I've never seen anything with low enough resistance for circuit traces. Also conductive grease comes to mind, I'm not sure how it can be used, but it certainly can be extruded and it's a decent conductor. Perhaps a metalic slurry made from metal powder and a conductive liquid that would dry. Or how about Wood's metal in a powder form mixed with flux paste then heated until it flows after extrusion.

Just some thoughts. Keep up the great work.

Signal Integrity Engineer
Asic Designer
Software Engineer
Mechanical Hobbiest
Yeah, I was thinking the same thing. As soon as my polymorph (from shapelock) arrives I was going to try mixing it with various powdered metals to see what happens.

Anyone know if the polymorph is ruined by heating it to melting temperature rather than just the 'moldable' temperature of 65 degrees? After it is fully melted and rehardened, does it still become moldable at 65?

Very interesting, conductive polymers are actually semiconductors, and can be made into n-type or p-type via various reactions given in the article. polymorph is an organic polymer so might be good at this. If we could create usable n and p type material, that would be the holy grail. complicated logic and chips could be FDMed just like anything else. (at much reduced density (at first) of course)

The only downside is that it would make it much harder to reuse material since you couldn't easily seperate out the various kinds of plastic after remelting. But it could still be reused for structural elements probably.

Here is a paper on some other chemicals you can mix with PCL (polymorph) to make it conductive.
So last night I was thinking, what if you extruded polymorph and Wood's metal together to make a wire-like structure. Using concentric nozzles, you extrude a tube of polymorph, inside of which you extrude (or inject) molten Wood's metal. The tube of polymorph around the metal may help it maintain a wire shape, as opposed to coagulating due to surface tension.

An additional advantage of this approach could be that the same head can extrude ONLY polymorph for structure, or add the inner condutor for electrical connections. Having only one ejection point would make the machine more simple to control, as well as calibrate.

There would certainly be complexities in creating and heating the two concentric nozzles. Perhaps the inner Wood's metal nozzle is heat electrically (nichrome wire) and the outter with a heat jacket and air.

Again, just a thought.

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