Rockwell Automation 1771-QDC, D17716.5.85(Passport) MNL. PLASTIC MOLDING MODULE - Manual (Page 12)

Chapter
1
1-1
Overview of Inject Mode
This chapter presents an overview of the 1771-QDC Plastic Molding
Module in the Inject mode. We present a summary of Inject features
followed by sample applications.
Important: This manual assumes you have already read your Plastic
Molding Module Application Guide, publication 1771-4.10, and have
chosen Inject as your QDC module’s mode of operation.
The Inject mode controls the following actions of your molding machine:
Shoots hot plastic into the mold
Packs and holds the plastic until cured
Reloads for the next shot
When you select the Inject mode, you can use the following phases:
Table 1.A
Phases of Inject Mode
Inject Phase Description
Injection The ram (screw) injects plastic into the mold. You can vary the velocity of the ram (screw), or the pressure
driving it, to fill areas of the mold cavity at different rates to achieve uniform quality of the molded part.
This phase can be critical to part quality. The pattern of velocity or pressure variation during injection is
called the injection profile.
Transition Detects when injection is complete.
Pack
(optional)
Packing pressurizes the plastic to a specified density which determines the flexibility of the molded part.
To achieve uniform density, you can release or increase pressure in steps according to cooling gradients
across the mold. Thus, as the plastic cools unevenly, the pack profile can compress the plastic uniformly.
Hold Holding lets the plastic cool and shrink slightly from the mold cavity in preparation for ejection. The affect
is similar to packing. You can hold at predetermined pressures for predetermined lengths of time
throughout the hold phase.
Pre-decompression
(optional)
This single, backward movement of the ram (screw) separates plastic solidifying in the mold from molten
cushion remaining in the barrel prior to plastication. This phase is also referred to as sprue break.
Plastication The machine reloads by drawing plastic beads into the barrel containing the ram (screw). The mechanical
action of the rotating ram (screw) grinds and melts the beads. The longer it grinds, the hotter it melts. You
can vary the screw RPM or backpressure on the ram (screw) causing it to remain longer in an area. Thus,
you can induce any desired temperature gradient along the length of the shot.
Post-decompression
(optional)
This single, backward movement of the ram (screw) guards against drooling molten plastic into the open
mold during ejection prior to the next injection. This phase is also called melt pullback or suckback.
Chapter Objectives
Inject Mode Operation