Inserts are parts of the mold that are created separately from the mold cavity block. Inserts are inserted in the block to achieve a desired cavity shape or cooling effect.
The effect of inserts on heat transfer
An insert will only assist heat transfer if a cooling channel is located in or near the insert. Inserts can be used to modify the rate of cooling in specific areas of the mold. A common example is a part with ribs that are thinner than the main surface. There is a natural tendency for the part to deflect away from the thinner ribs as the main surface has higher area shrinkage. By running the rib area hotter (conductivity insert), the part can be deflected back to the required shape. In some cases, an insert of lower conductivity or containing a separate cooling circuit, can be used to form the ribs. This gives better control of the rib temperature.
Modeling inserts
Inserts are modeled with regions representing each of the faces of the insert. In its simplest form, the complete insert is effectively a closed volume defined by the six surfaces of a cube. Inserts can have complex cross-sections to match features on the cavity model, in which case they consist of more than the basic six surfaces. Inserts can be added to inserts to create more complex shapes. When small inserts abut onto larger inserts, the surface of the larger insert must have an internal boundary for the smaller insert to connect with.
When the edge of a plastic surface runs across an insert surface, the insert surface should have an internal boundary added to ensure that the mesh on the plastic surface and the mesh on the insert surface are compatible. Inserts must not contact the mold outer surface.