User Manual

Troubleshooting 37
Table 7-2 DJ-9500 Troubleshooting – Set-up Based
Set-up Variable Effect Notes
Fluid
Properties
Dispense
Volume and
Quality
If this is a new process, contact Nordson ASYMTEK for
assistance in process development. If this is a qualified process,
fluid properties may have changed. The fluid may have
exceeded its pot life, or been mishandled or set-up incorrectly.
In addition, air bubbles are a common problem in mixed, high
viscosity fluids. Improper thawing can introduce air to the fluid
supply, which results in intermittent shots. De-gas the fluid if
possible in a vacuum chamber.
Fluid Pressure
Dispense
Volume
Verify that the fluid supply has been set up correctly and that
fluid is free to flow to the jet chamber. Verify the pressure setting
is correct. Insufficient fluid pressure results in small shot
volumes or no shots. Too much fluid pressure leads to larger
shot volumes.
Valve Pressure
Dispense
Volume
Needle assembly travel is affected by valve pressure. Lower
valve pressure increases jet reaction time. In high duty-cycle
applications, sufficient valve pressure is required to meet
performance specifications.
TCA
Temperature
Dispense
Volume and
Quality
Typically, higher temperatures lead to decreased fluid viscosity
and a higher fluid flow rate. Test the sensitivity of the fluid to a
small temperature change. Verify the Temperature Control
Assembly – TCA, is holding at the desired temperature through
the Fluidmove Temperature Control Window.
Both the heater element and RTD are 2-wire devices. Failure
modes include “open” and “short”. The “open” mode occurs
when either of the two wires is broken. The “short” mode occurs
when there is zero resistance across the two wires, or between
either wire and the TCA body.
Cooling occurs by circulating compressed air through the TCA.
Check that adequate air pressure is present at the transparent
green pneumatic line, and that the coolant passage is
unobstructed.
Body
Temperature
Dispense
Volume and
Quality
The body temperature is usually set to the same temperature as
the TCA temperature.
Cooling occurs by circulating compressed air through the body.
Check that adequate air pressure is present at the green
pneumatic line, and that the coolant passage is unobstructed.
Jet On/Off
Time
Dispense
Volume
The time the solenoid control signal is held on is termed “On
Time”. The time between “On” signals is termed “Off Time”.
On/off times that are too small will not allow the needle
assembly to fully open or fully close. On times set too large may
cause excess fluid to flow through the jet.
Dispense Gap Dispense Quality
A jet with the dispense gap set too low will “plow” through the
dispensed fluid and accumulate fluid on the nozzle tip. Dispense
gaps set too high will result in poor shot shape with a higher
frequency of dispense “satellites.”