Wednesday, June 08, 2005


Nozzle made of solder

I had a successful run on the 'Afghan Lathe', and managed to bore a beautiful 3mm hole in an M6 bolt, right down the middle. To avoid the use of fine drills for the nozzle, I tried out an idea we'd had on using solder. I propped a piece of 0.32mm nichrome wire vertically in the hollow brass bolt - I'd only drilled the last 2mm out to a 1mm hole on that end - and soldered around it. When the solder was cold, I pulled it out with pliers to leave a 0.32mm hole in the solder. Nichrome is very handy here as it can't be wetted by standard solder.

Tests with a syringe show it squirts water in a straight, true jet. If it works with Polymorph, it'll be a very simple way of making nozzles of varying sizes. This first one will be incorporated in a Polymorph extrusion nozzle similar to the one Adrian just made, and we'll see how well it ejects Polymorph.

What is thought to be an ideal nozzle diameter?

I can imagine that there would be a huge trade-off between precision and speed here.

Would it be worth considering interchangeable nozzles - or perhaps even some kind of computer-controlled variable diameter nozzle? (Although it's hard to imagine a good way to build such a thing).
When I read this, the first thing that came to mind was a microscope turret.
Commercial FDM machines use about 0.4mm. One has a tradeoff: precision against speed. I suspect that having a big nozzle for fill and a little one for finish would be enough - say 1mm and 0.2 mm. But one has to be a little clever - remember they all have to produce the same vertical thickness.
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