What you describe is a common issue. Placing a viscous material into a syringe after you’ve vacuum degassed it generally can create air pockets. Centrifiging the material once you’ve placed it into the syringe should take care of this problem. Here is a link to the Nordson EFD centrifuge. It might take up to three minutes of centrifuging to remove the air pockets; however, the centrifuge has worked extremely well in the past for this situation.

Regarding your question about using positive displacement to minimise the air bubbles on your dispense bead: If you see air pockets in the dispense bead, that means air is trapped in the material. If that’s the case, a positive displacement dispenser will not be a benefit to you. Once you eliminate all of the air in the fluid, the air powered dispenser will work fine—the piston inside  the syringe will act as a barrier to prevent air from penetrating into your fluid.

That depends on the type of fluid you are dispensing. If you are dispensing a particle-filled material, partial clogging in the dispensing tip could cause the variations.

One of the most common factors to consider is your plant air supply. If you have fluctuations in the air-line going into the dispenser, you will almost certainly get variations in your deposit size. Make sure you have a in-line filter regulator between your plant air supply and the dispenser. If you do have plant air fluctuations, you should set the filter regulator approximately 5 to 10 psi lower than your lowest plant air fluctuation point.

Yes, we have both an aseptic dispense valve and spray valve that can be autoclaved, cleaned-in-place or steamed-in-place.  The aseptic dispense valve is used for making dots, stripes, or small volume fills of fluids. The aseptic spray valve is used for spray coating small areas with inner diameters 1/8 in. and larger. Both valves are primarily used on automated machines.