Rockwell Automation 1771-QDC, D17716.5.93(Passport) PLASTIC MOLDING MODULE - Manual (Page 16)

Overview of Inject, Clamp, and Eject Mode
Chapter 1
1-4
Flash Prevention Example - With a velocity profile (Figure 1.4 part 1),
the pressure may reach a peak and flash the mold at ram (screw) position
segments that correspond to events such as:
the initial surge (2.a)
when the melt front enters a constriction in the mold cavity (2.b)
You can remedy this (part 3) by decreasing the ram (screw) velocity at
segments (3.a) and (3.b) that correspond to flash points. Conversely, you
can boost velocity at segment (3.c) where the resulting pressure is well
below the flash point.
Figure 1.4
Flash Prevention Example
1. Initial Velocity Profile 2. Resulting Pressure Profile
b a
Flash
Point
3. Final Velocity Profile
c
b c a
b c a
Velocity
Velocity
Pressure
Position Position
Position
Pressure
Position
4. Resulting Pressure Profile
b a
Flash
Point
c
Optionally, you may select pressure limited velocity versus position as
your method of injection control. With your pressure limit setpoint just
below the flash point, the module switches over to pressure control prior to
flashing the mold.