Rockwell Automation 1771-QDC, D17716.5.85(Passport) MNL. PLASTIC MOLDING MODULE - Manual (Page 15)

Overview of Inject 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 (part 2) 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. Segment pressures in part 4 are optimum for the
velocity vs. position profile in part 3.
Figure 1.4
Flash Prevention Example
1. Initial Velocity Profile 2. Resulting Pressure Profile
b a
Flash
Point
c b c a
Velocity
Pressure
Position Position
Velocity
Position
3. Final Velocity Profile
b c a
Pressure
Position
4. Resulting Pressure Profile
b a
Flash
Point
c
As an option, you may select pressure-limited velocity vs. position
injection control. With your pressure-limit setpoint below the flash point,
the module switches to pressure control prior to flashing the mold.