Why is constant air pressure important for piston pumps?
Constant air pressure maintains a constant force on the syringe plunger so the piston’s up stroke
timing doesn’t have to compensate for the time it would take to compress the air volume between
the air inlet and the plunger. There are other benefits to maintaining constant air pressure besides
maintaining a ready supply of material. It also reduces the number of parts needed to supply and
regulate the air pressure to the syringe.
Low air pressure – If the air pressure on the syringe is set too low there will not be
enough force on the plunger to move material into the piston chamber. The length of
time the piston is in the up stroke position is directly related to the time it takes to fill
the piston chamber. This time is adjustable in software parameters. If the piston fires
before the material has filled the piston chamber, the piston will displace an
inconsistent volume of material, resulting in insufficient or missing dots.
High air pressure – If the air pressure on the syringe is set too high it will force
material between the piston and the needle hub, causing material to drool from the
needle. Excessive air pressure can also cause the chamber to fill too quickly . The
piston up stroke timing would then need adjustment to prevent material from flowing
out the needle prior to seating the piston.