Monday, April 16, 2007


Mechanical Nozzle: Promising

I made a trip to Staples today after work, and was pleasantly surprised when I found some mechanical pencils with *just* the right tip. It is an all-metal 0.5mm tip with ~1/4" female threads. I couldn't find the right thread exactly, as they didnt have a good selection of screws. The 1/4" coarse threads did jam in there just fine... nothing a bit of force and jbweld cant make work. ;) However, I'm pretty sure that fine-thread 1/4" screws will work just fine... which means easy interchangeability.

One other thing that might pose a challenge is that the 0.5mm part is quite long... I'll be attempting to cut it closer (or flush) when I get to the shop tomorrow. I think with a dremel it should survive pretty well. My plan is to dremel it down flush, use a thumbtack to de-burr it / clear it out, and then bolt it onto the end of a 1/4" jbweld heater barrel. from there i just attach it to the extruder and its smooth sailing!

Also, one final experiment I did was to try and make interchangeable nozzles with jbweld. The process I used was this: Wrap plastic over threaded rod. Thread nut onto rod, until the tip of the rod is *almost* flush with the nut. Then, spread some jbweld into the small depression, and let it sit. (its important to let this setup vertically, as jbweld slowly settles and may run). The results look pretty good. I'm going to attempt to drill them tomorrow too. Hopefully if the mechanical pencil works out, this technique can be abandoned. The molding process was pretty easy, and simple. The upside of these is that they are very cheap and can be easily *made* at home. also, they are naturally flat on the bottoms, as opposed to the pointy tip of the mechanical pencils. I dont know if that will matter at all.

How are you going to keep that thing hot? You've got LOT of exposed surface there.
nichrome wire + current?
You going to wrap that ogive shape with nichrome? Good job if you can manage it.

Hey! Don't mind me, I'm just picking at the idea to see if there are any holes. I certainly don't have an inside track on whether it will work or not by any means. It would certainly solve a LOT of problems if it does work and is well worth trying.

Just a suggestion, though. If you're going to grind that tip down you might want to just leave the lead in it when you do. That should keep any metal burrs from getting into the channel and it should be no trouble pushing the remains of the lead out with a needle afterwards.
You should check if it's metric threads rather than a 1/4" one, given that it's a 0.5mmm tip.
nice suggestion forrest... i'll definitely try that. i realize there is alot of surface area. the only way to know if it will work is to actually try it. i'll let you know once that happens. if this does end up working, it would be a huge win for the project.
I've got a Berol automatic TL5 here with a metal tip that has a 6mm diameter with a .5mm threads (very close to a 1/4"-40 but not)
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