slathrop@BINNEY-SMITH.COM on fri 30 jun 00
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We have used several air assisted liquid applicators here in Research
and Development. They all suffer the same malfunction to some
degree. Only mechanically driven syringe barrels can give an even
application. But mechanical applicators like JG machine, Filamatic and
others are cost prohibitive. Several of the air assisted plastic syringe
type of barrels like the Airpen all have rubber plungers in a plastic
barrel. The plungers require frequent disassembly and cleaning then
applications of silicon oil to work properly. A less satisfactory lubricant
like Vaseline which causes the plunger to swell over time and bind in the
barrel requiring more frequent replacement should be avoided.
Mineral or Glaze raw materials scratch the barrels after a short time and
cause the plunger to stick no matter how carefully you clean and
lubricate. Scratched barrels in tern cause more dramatic intermittent
stops and starts. Very awkward when you are trying to lay down a
continuous width bead or line. Plastic systems are primarily designed
for very thin solutions that don't contain gritty suspensions and are really
disposable. The large surface of the plunger invites solids to
become trapped and scratch the barrel.
If you plan to use an applicator on a semi production bases or more than
say an hour a week then costs of replacement barrels/ plungers will
become a cost consideration long term. The best of the plastic type we
have found is metal barrel with a replaceable poly film liner; It is also an
air operated syringe. Using inexpensive replaceable O rings as
plungers and replaceable poly liners to work far better, smoother, longer,
and require less maintenance with gritty materials than a standard syringe
based applicator like an Airpen.
However, the initial cost is more than double the Airpen, but the long term
cost and aggravation is considerably less. I have only replaced 2 poly
liners and 2 O-rings in 6 years of moderate use (8-10 hours a week).
The dispenser we use for relatively small volumes is a Precision
dispenser. It holds 20 cc or 0.68oz. It does require an external air source
like a bicycle pump or compressed air.
A metal barrel/O-ring plunger trigger operated Precision Dispenser Kit
costs $236.61 plus extra cartridge and cap sets $29.26 a dozen and
dispensing tubes $25.33 a dozen. If you are interested in the system
we have been using for the last 6 years you can find it in
McMASTER-CARR catalog-102. Part number 7455A62. page 2668.
You can call catalog sales if you don't have the catalog (732)329-3200.
They ship UPS.
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