Thermoplast Extruder v1.1 Nozzle - Is the "nose" necessary?

Looking at the extruder's nozzle construction instructions [reprap.org], I see that a 1.5mm diameter "nose" with a 0.5mm hole drilled through is used at the tip of the nozzle. Is this necessary, or could I just drill the 0.5mm hole directly in the center of the 8mm rod?

Edit:
Furthermore, could I not simply drill the 0.5mm hole directly in the M6 studding barrel, eliminating the need for a separate nozzle? It would be less configurable, but for a RepStrap this is not a major concern.

Edited 1 time(s). Last edit at 07/20/2008 01:51PM by Joshua Merchant.

IMHO, it is better to have a cone shape at the end of the nozzle. That was the original design and I found it gave the best surface finish.

A completely flat ended nozzle would interfere with the filament already laid down. The nozzle runs at a height above the workpiece slightly less that the filament diameter so it has to squash the filament slightly without rucking up adjacent lanes. This makes the shape quite critical.

The reason for having it removable is to allow unblocking of jams which some people find necessary (but I never have), as well as allowing changing the nozzle aperture. Also it is quite hard to drill the barrel to exactly the right length inside so that the small hole in the end is not too short or too long.

In practice I have found it near impossible to unscrew without the heater barrel turning in the PTFE and breaking the heater wires, YMMV.

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[www.hydraraptor.blogspot.com]

Hm. With these limitations, I'm thinking that you could take the suggested 8mm rod, drill and tap it as described, stopping a certain distance before the end. Then, put it on a lathe and use some sort of file (or other tool, I'm not really hardware-knowledgeable) at a certain desired angle to make the tip of the rod a pointed cone. Then take a countersink with a slightly sharper angle and drill from the inside, until a tiny tip of the cone comes off. Then continue drilling until the desired aperture is formed. Would look much cooler and (I think) be more effective than the pictured nozzle on the extruder mechanical parts page [reprap.org].

I think it's feasible, provided you can precisely control the relative positioning between the countersink and rod while drilling (I think this could be done by clamping the countersinking device, and then moving the rod slowly towards it; I could probably rig up some simple contraption for doing this).
The aperture size can be easily controlled by measuring the angle of the countersink and keeping track of the distance between the countersink tip and the rod tip while drilling.

I just figured that the current design uses a lathe already anyway, so why not do this?

There have been four nozzle designs you can see two here: [hydraraptor.blogspot.com]

You need to get the length of the hole correct. Too short and the extruder oozes a lot, too long and it will be hard to push the plastic through.

The first was a one part nozzle turned from a brass rod. It works well but you need a lathe.

The easiest one to make is the acorn nut version but it is a bit too flat and the exit how a bit short. It does work however and it doesn't need a lathe.

Then there is the the one with the nose on it which is what I am using at the moment. It works pretty well but you need a lathe. I think a cone shaped end with the same hole depth would work better.

There is a fourth design, which also has the anti-ooze value but I have not tried that yet.

I would suggest, for a first attempt you try the acorn nut version, as all you have to do is drill a small hole in the end.

Edited 1 time(s). Last edit at 07/22/2008 12:18PM by nophead.

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[www.hydraraptor.blogspot.com]

Alright, thanks.

Now, time to work on that "studying" thing I was supposed to start doing yesterday....