Hakan, what Inge refers to is: when cleaning the needles ,
i objected to inside steps :
the needle inside even if tapered (should have a paper cut sharp tip edge)
should have continuous ONE angle straight line inner walls,
either conus or parallel ,
that way cleaning broach can wipe ALL surface clean
(with side leaned motion if conical inside) .
Also the sudden dia decrease does aid inner wall drag,
which work two ways - slows the side flow (gloriously brakes G's),
but slips the center flow .
As we exchanged with Inge , conical carbide tips from jet nozzles,
like Nordson's, are best (for some applications),
if modified with foot for dispensing,
pending what at what speed you dispense on what ;
with low viscosity the upZ acceleration is less dripping with
Inge's recommended type (reduced dia acts as a brake to fluid fall).
For denser viscosity this would be a wrong choice.
In Inge's application (silver in thin polymer)the wide tube small exit did
make a sense,
as he did need a room for silver flakes suspended in polymer,
despite potential cleaning difficulties the extra wide barrel
did accommodate for the silver particles irregularities .
With religious h.pressure cleaning it's true dl 's fine indeed.
Also obviously the speed of exit from narrowed tip is that much faster,
as the wider hydraulics move the center flow mass with less drag easier,
using side mass as an slide buffer .
The cad models of tubular rheology are endless,
simple models you can make 10:1 in cast clear acryl,
and view with flakes (japanese lacquer supply)and stream (inner/mid/outer)
dyes(food) suspended in calibrated fluids,
if yo'd want to see
suma sumarum, there's no hook ;
just needles are lateral relative as anything else,
as Inge successfully combated in a classic grand OEM style.
(ask him for pdf's)
For low speeds we use ESD's , as they're good,cheap,throwaway's,
mix kits good for initial R&D .
paul
-----Original Message-----
From: Ingemar Hernefjord (EMW)
[mailto:[log in to unmask]]
Sent: Thursday, 25 May 2000 22:46
To: [log in to unmask]
Subject: Re: [TN] Tapered needles
Dear Mr Tornkfist,
my proposal is that you contact DL-people. During certain combat with
clogging dispensers etc I found a company with a very flexible program. I
studied some needles from them and found they were outstanding. At least in
our point of view. His Eminency P. Klasek had some critical words about the
inside radius from D2 to D1, maybe there is a hook. why not visit DL's page:
<http://www.dltechnology.com/>.
Hope this helps
Ingemar
-----Original Message-----
From: Håkan Törnqvist (EMW) [mailto:[log in to unmask]]
Sent: den 25 maj 2000 12:52
To: [log in to unmask]
Subject: [TN] Tapered needles
Hi,
Does anyone know of any supplier of tapered needles for fluid dispensers.
I'm interested in 25-30 gauge needles.
Best regards,
/Håkan Törnqvist
Microwave MCM, Design & Production Support
Ericsson Microwave Systems AB
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