Profiles are used to ensure that the simulation matches the actual molding process as accurately as possible.
Ram speed, velocity or filling profiles are used in the filling phase to control the movement of the screw. Pressure or packing/holding profiles are used in the packing/holding phase to control the packing and holding pressure applied to the mold. The change from velocity to pressure profile control occurs when the velocity/pressure switch-over point is reached. Both types of profiles help reduce mold defects such as flashing, short shots, jetting, burning, sink marks, warpage, flaking, and more.
Temperature profiles are used to simulate the surface temperature of zones of the mold through the injection cycle.
Gas profiles are used to control the injection of gas when simulating gas injection molding.
Changes in the filling profile are typically set to correspond with changes in the mold geometry taking into account the flow restrictions inside the mold. The aim of profiling is to maintain a constant flow front. When the flow front reaches a cross sectional constriction within the mold, the rate of injection (screw velocity) should be reduced. It should be increased when the cross sectional area at the flow front increases. This is important when the flow front reaches the gate. If the melt is injected too fast, it can result in jetting, burning, flaking, melt degradation and surface defects. A common approach is to use a high screw velocity while the melt is moving through the runner system to avoid cooling of the flow front, reduce the velocity when the flow front approaches the gate, and finally increase the velocity once the melt is filling the part.
The velocity should be reduced when the flow front reaches the end of filling to prevent overpacking of the cavity, which may cause stress problems, warpage, and flashing. This facilitates a smooth transition to the packing phase where a pressure profile is used to ensure uniform shrinkage, reduce warpage, and to pack the part well without overpacking.
Linear and constant profiles can be used in the filling phase and the packing phase.
You can also choose to use a relative or absolute velocity profile.