EFD Ultra 325TT User Manual page 71

Ultra TT User's Guide
®
Version 1.2
A NORDSON COMPANY
Multishot Delta
This is the Z-height that the dispensing head will retract between each shot at the same X/Y
location. It is used in conjunction with Number of Shots. Note that the Dwell Time parameter is
applied between shots. The units are in inches or millimeters.
In a potting application, the use of the Number of Shots and Multi-Shot Delta keep the dispense
tip above the potting compound as part is being filled.
Dwell Time
Dwell Time measures how long the dispensing head stays at the final position after the end of
dispensing before retracting multishot delta. This may be necessary to give the fluid a chance to
detach from the tip and onto the substrate i.e. increasing the Dwell Time can reduce "stringing" of
material. The units are in seconds.
For most solder pastes and adhesives, 30 ms is sufficient. However, the Dwell Time can be set as
long as 6 seconds for very elastic fluids.
Reverse Time
This parameter is only required when the 790 Auger valve has been selected in the Setup mode.
At the end of dispensing a dot, the valve is reversed for the specified time period to remove any
material from the tip of the needle. The Reverse Time value should be set according to fluid/paste
viscosity. Generally, 10 ms (0.010 sec) is sufficient.
Retract Speed
This is the speed of the dispensing head while moving the Retract Distance (valve moving up). This
parameter is useful in breaking off stringing material i.e. slowing retract speed. The units are either
in inches/second or mm/second. Typically, 2 in/sec or 50.8mm/sec is sufficient.
Retract Distance
This is a vertical distance that the dispensing head moves after dispensing. The Retract Distance
must be high enough to clear any obstacles on the work-piece during the movement to the next
point. The Retract Distance can be reduced to increase throughput. The units are either in inches
or millimeters. Typically, 10mm or 0.4 in is sufficient.
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