Rockwell Automation 1771-QDC, D17716.5.85(Passport) MNL. PLASTIC MOLDING MODULE - Manual (Page 14)

Overview of Inject Mode
Chapter 1
1-3
With this Profile You Control Injection With up to 11 Segments
Distributed over the
Velocity vs. Position Speed Length of the shot
Pressure-limited [1]
Velocity vs. Position
Speed, with a maximum
pressure
Length of the shot
Pressure vs. Position Pressure Length of the shot
Pressure vs. Time Pressure Time for a shot
[1] Pressure-limited velocity vs. position profile differs from the velocity
vs. position profile as follows: During any segment of a pressure-limited
profile if the pressure exceeds a preset limit, the module switches to PID
pressure control with the pressure limit as the setpoint. Then if velocity
exceeds the velocity setpoint, the module returns to velocity control.
Example Benefits of Profiling an Injection Phase
The injection phase should force the melt through the mold as fast as
possible without flashing or burning the melt at a mold gate. Here are two
examples of how you can achieve this by profiling the injection phase.
Velocity Example – As the leading edge of melt enters mold cavities, the
flow of plastic through the gate should increase or decrease accordingly to
keep the melt front at maximum desired speed without flashing the mold.
This reduces injection time and minimizes surface stress due to surface
cooling. You achieve this by shaping the injection profile to suit the mold
cavity (figure 1.3).
Figure 1.3
Velocity Example
Mold Cavity
5 4 3 2 1
Flow into mold
1 2 3 4 5
Position
Sequence of execution Back
Point
Mold
End
Injection Profile
Velocity
Gate