Saturday, August 23, 2008


Even More feed rollers.

I have been trying various options with my 'rolling nut' filament feed design with much learning and many questions arising. More detail here.

I have also had an idea for making teeny weeny nozzle holes. Rather than drilling them in metal nuts etc (and the latest aluminium one from is rather nice) how about this :

I purchased some brass tube - 2mm OD, 1.4mm bore - from B&Q. I snipped off a short section, inserted the leg of a resistor and squashed the end with my wirecutters. Pull out the resistor leg leaving an almost perfect 0.5mm hole. Its not clear in the photo but the hole passes through the nearest part. The result is almost round with a small slot. I will experiment further.

Mounting it will not be simple, I have considered flairing the top end and simply dropping it into a bigger (2mm) hole, or using silver solder (melts well above 250 C).

Copper would be better as it is more malleable, but B&Q didn't have any small enough. I will check to see what capillary tubing I can get from my local laboratory supplier.

STOP PRESS : I just had another thought - we used to get tiny carburettor jets, made by a company called AMAL - for use in gas engine conversions (Calor gas, not gasoline gas). These are weeny nozzles - I just dug out some and the hole is 0.35mm in a brass body with a 1BA thread. The 1BA male thread just about works with an M6 nut. From what what I remember they were cheap AND available from our local Calor gas depot. Why re-invent the wheel?

I love this idea for making nozzles-- i think i'll try it next time i'm making some.
Not sure what sizes you're talking about, but how about those "needles" they use to inflate footballs and basketballs and the like?
Half a milimeter. I would think the football inflators are a fir bit bigger than that.
Why don't you just use a standard hypodermic syringe needle. You can buy them at any veterinary supply business. Most feed stores have them. Mind, if you're in the US whatever you do DON'T try buying them at your chemist's. It's one of those huge holes in American law that makes this such a bizarre place to live. Chemists can't sell you needles. It's a felony for both the chemist and you. Doctors can't get them for you, either. Same laws.

Now if you go into a IV drug support center in a major metro area they will give you clean needles even though doing so is a felony and using recreational IV drugs is, too.

Veterinary suppliers, however, stock them and the worst I've ever seen them ask is that you sign a register pledging that you won't be using them to give yourself injections of illegal drugs.

Anyhow, they come in all gauges down to very fine holes. File the needle off of one of those up near where it goes onto the syringe and you've got your extruder. :-)

I got acquainted with 'em trying to blow bubbles into molten HDPE a few years ago.
FOrrest, dont they come with a plastic adapter at the top end?
If this is cut off too then we may be able to use the bit of fine tube somehow.
How about mechanical pencil tips? They're metal, fairly strong, come in .5mm and .7mm, are already threaded and "nut like" for interchangability, and they have a short tube so the plastic doesn't come out to fast which can be filed a bit to adjust the feed stoppage. Even more readily available than needles. Probably cheaper. And the only challenge is getting somebody to cut appropriately sized threads in your heater barrel.
I correct myself. They have .3mm mechanical pencils too. here you can buy one for $1.89, ~$9 including shipping (for me, anyway). That's really steep on the shipping, so I'll be going to my local office supply / art supply shop instead.
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