Injection-compression process details

The compression-injection process can be described according to the details outlined below.

Process Details

1. Oversized cavity; the cavity thickness is initially oversized by 0.5 to 10 mm more than the target thickness. The thickness will be reduced later.
2. Injection; plastic melt is injected into the cavity at a user-defined injection velocity. At the velocity-pressure switchover time, the pack phase starts, following a user-defined packing profile, and regardless of when press compression is programmed to start.
3. Press waiting; meanwhile, the press is moved to a pre-determined position. It will be stationary and stay in this position for a period of time. This time period is called the press waiting time (Midplane) or press compression starts (3D). The waiting time starts when the injection begins and ends when the press begins to move.
4. Compression stage; the compression stage starts when the press begins to move. (The press is sometimes called the plunger, moving mold half, or moving platen.) It includes the time during which compression is under speed control, plus the time during which the press is under force control.
   Compression can be programmed to begin

   • while the melt is being injected, resulting in simultaneous press and injection conditions
   • during the injection pack profile
   • upon completion of the injection pack stage.
     Note: In this case, cooling will start at the end of the compression stage.
   1. The user-defined Press compression time is the maximum time for press movement. Once reached, press movement stops even if the specified press speed and/ or force profiles are not yet complete.
   2. Compression under speed control; in the press compression stage, the movement of the press in initially under speed control, specified by the press compression speed at incremental distances profile. For each incremental distance, the press moves at a constant speed. This type of movement continues until it reaches a pre-set press compression force.
   3. Compression under force control; after the press force reaches the pre-set force, the press switches from speed control to force control. The press can keep moving forward, however, it will be in a constant force control mode (pre-set force).
5. Stationary press; after the press compression phase is complete, the press will stay in that position and remain stationary thereafter.
6. Cooling or Curing stage; Cooling starts at the end of the press compression time, or at the end of the injection packing stage, whichever ends later, and can be set as Specified (SCT), or Automatic (ACT).
   Note: For 3D reactive injection-compression molding, curing time can be entered only as Specified.
7. Press returns; when packing and cooling end and mold-opening begins, the press begins to move backward.