Graco VPM 12, Instructions Manual

Page: 33 / 88

Operation
313875J 33
Machine Operation Overview
Ramp Up Feature
The purpose of the ramp up feature is to enable dis-
pensing at the correct ratio but at a reduced flow rate
when materials are too thick to dispense at the correct
flow rate. As the fluid warms up due to the friction of
moving through the system, the Ramp Up feature will
slowly increase the flow rate until the desired flow rate is
achieved. After a period of idle time the system will cool
down and the fluids will not be as warm while dispens-
ing, which may result in the Ramp Up feature being acti-
vated.
While the system is dispensing, the ramp up feature
monitors the torque supplied to the B (Blue) pump to
verify it does not apply more torque than the pump can
handle. If it does, it will reduce the flow rate in both
pumps to maintain the required dispense ratio. As the
system warms up and material thickness decreases, the
ramp up feature will increase the flow rate until the
desired flow rate is achieved.
NOTE: Because the B (Blue) side is the high volume
side, it is closer to its maximum flow rate capacity than
the A (Red) side pump.
Because a base purge is done before the system is shut
down, the first dispense after the system is turned on is
always initiated at a reduced flow rate. The ramp up fea-
ture will then increase the flow rate as described in the
previous paragraph. Also, after ten minutes of idle time
the first dispense will be at a reduced flow rate followed
by the flow rate ramp up.
When the ramp up feature reduces the flow rate, a “Sys-
tem Dispensing Below Requested Set Point” advisory is
generated and the yellow advisory lamp on the light
tower is illuminated. If the system is able to achieve the
desired flow rate the advisory is cleared.
Learning Mode
When a flow rate or dispense ratio is requested that the
machine has not learned, the system will use the pump
volume of each pump to estimate the pump velocities
needed then Learn mode will be used to adjust them to
the correct flow rates. The system will begin dispensing
at the estimated pump velocity and each stroke per-
formed will be used to gather information and adjust the
velocity. After a number of strokes, the system will have
sufficient data to accurately dispense at the desired set-
point and Learning mode will be exited.
When Learn mode is active, a “Learning New Set Point”
advisory is generated and the yellow light on the light
tower is illuminated. After Learn mode is complete, the
advisory is cleared.