Syringe needle and soldering iron idea

I am working on a delta robot 3D printer.
This is a light weight device costing about £20 in parts (excluding electronics).
I build delta robot already [www.enemygadgets.com]
But now I need a really light weight extruder.
I'm thinking of a syringe needle and a light weight SMT temperature controlled soldering iron.
Lead solder can bathe the needle in a jacket of molten lead and temperature
control is built into the soldering iron!

Will the idea fly? (I don't know enough about FDM heads.)
If it could, this type of head would cost about £60 to build and look out Gada prize, here I come!

We usually wrap our extruder nozzles in nichrome wire and either kapton tape or ceramic glue to heat them. We also try to keep the thin section of the nozzle very short, ie less than 1 mm long, as long thin nozzles require very high extrusion pressures. Molten lead is less viscous than molten plastic though.

I'd say just try it and see if it works. What kind of resolution, speed and build volume do your delta robots have? My Mendel has 0.1 mm res, 200 x 200 x 100 mm build area, and can move the ~0.5 kg extruder around at 50 mm/s.

Hmmm... extruding molten lead would be better than extruding molten plastic because of the viscosity!!

I take on board your point about having short section of thin nozzle to keep the pressure down.
Never occurred to me!

I should be able to grind the needle after fitting to 1mm or less. But that sounds like wasted effort because it would be easier
to drill with say a 3mm drill most of the way and drill the last mm with a 0.1mm drill as recommended in
some of the construction notes.
The nichrome wire heater assembly would make the whole thing bulky for a delta robot - so thought best to
get a light weight temperature controlled soldering iron to become the heater. That way you just heat up
some lead and bath the metal container which would melt the plastic. I'm hoping to keep the metal part of the head
less than 5mm cubed otherwise the soldering iron is just not going to get hot enough unless you make it with a big iron
but that then adds weight again which this fragile light weight delta robot can't handle. It might mean having to preheat
and extrude the fuse through a 1mm die to reduce its diameter down a bit before it ends up in the injector.

The delta robot accuracy you can trade for speed and length of the servo arms - typically 0.3mm is about the best achievable.
I don't have very fine control from one servo position to next at this moment in time, but that is not difficult to get
the software modified to get that going. I have two deltas at the moment and the one in the picture has a reach of about 100mm diameter with about 50mm height before it has 'problems'. The other delta has shorter arms but greater accuracy.

The alternative to carrying a heavy injector head is to keep the head fixed and move the work piece using an upside down delta robot (similar to what a Stewart platform achieves). But the issue then is that as the work piece grows bigger, it weighs down the delta robot and makes it more sluggish and more inaccurate as the printed part gets bigger.