Ingemar,

In my mind the decision for air vs screw [air time-pressure vs positive
displacement] is made on the basis of just how much volumetric control you
require [and the characteristics of the material].  

If the RT time vs viscosity characteristics of the material allow you to go
with a simple time/pressure arrangement, then all you need to hang on the
end of your robot arm is a syringe and needle.  Cleanup is a snap.

I hate cleaning the screw/auger systems!!!  Things get even more complicated
with short pot-life materials.

It always seems like someone in production 'forgets' to clean the system
before leaving for the weekend ... leading to cost and delay issues the
following Monday.

I would certainly try an experiment with time vs pressure first.  If that
doesn't work, well there are other positive displacement systems that are
less cumbersome than the screws.  Asymtek and others for example [$]

Did I say that I like the old time vs pressure approach if I can get away
with it??  :-)

Best wishes

Steve



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Monday, February 09, 2009 3:54 PM
To: [log in to unmask]
Subject: [TN] robotic dispensing

Hi all,
have to buy or lease a 6axis robot for dispensing UV cured conductive epoxy 
in thousands of small tubes or channels. Strings 0.5 mm wide and 20 mm long.

Only the dispenser tip can enter, the rest of the dispenser must stay 
outside the target. Speed is of no interest, quality the more. It's a very 
small one,  only 500 pounds of weight and max payload 10 pounds. All DC 
motors, no hydraulics. Position accuracy is 50 micrometers.
Q: anyone with opinion what is best, pressurized air piston or screw? Are 
there dispensers for easy robotic hand mount?
Inge 

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