First of all this type of device is common in precision assembly lines
for dispensing glues. Pumping fluids long distances through very narrow
pipes is extremely inefficient so a high pressure hose feeds a manifold
with capillary tube size nozzles. For two part resin/catylist systems
two hoses feed a mixing chamber at the manifold.

Capillary tube is available in copper, aluminum, stainless steel and
several plastics. There are even some aramid capillaries with ODs
smaller than a human hair. Refrigeration thermostats use a very small
ID capillary tube to connect sensor bulbs to a pressure switch. It is
relatively thick walled compared to the ID so that it can be bent
without crimping.

Metal and thermoplastic tube is made with water cooled a die.
(Thermoset plastics use a heated die.) The die has a hole the size of
the tube OD. A pin the size of the ID is centered in the hole. A metal
alloy or thermoplastic polymer just at the liquidus point is extruded
through under high pressure and solidifies as it exits the other side.

Allan Adler wrote:
One can regard the needle of a syringe as a very thin pipe, but it is also
a very short pipe. Syringes are used in microscale organic chemistry labs
to transfer small quantities of fluids. If one wanted to avoid syringes
and instead transfer the same quantities of liquids along a pipe from a
small tank of the liquid, I imagine one would need a pipe as thin as a
syringe needle. At any rate, one can choose to do so at the design level.
(I realize there might be more resistance along the pipe and considerable
difficulty clearing a blocked pipe and possible problems due to sagging of
the pipe, but never mind.)

I have no laboratory and no shop and have no plans to actually do any of this.
I'm just thinking about how it might be done. Since the solution involves
a problem in metal work, I think it is appropriate to ask about it here.

The questions a
(1) How would one make a long metal pipe (e.g. a few feet) which is as thin
and as hollow as a syringe needle?
(2) And what if one wanted the pipe to follow some path other than straight?
Probably it is too thin to bend without closing it off, no matter how
carefully one tries to do it. Maybe one has to make miniature versions
of all of the standard plumbing fixtures and, to make sure the connections
are strong enough, one allows the outer diameters of the pipes to increase
where the threads are. So that feature of the pipe design would also have
to be included.

Ignorantly,
Allan Adler


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* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
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--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
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