Insert molding (sometimes called over-molding) consists of placing a solid insert into the mold and injecting TPV around it. If the insert and the TPV are compatible materials, a melt bond occurs at the interface between the two materials. The strength of this bond is affected by several factors, including interface temperature, cleanliness of the insert and the melt temperature of the TPV.
Bonding can be improved by preheating the insert and ensuring that the surface of the insert is free from dirt, grease or hand oils. Non-compatible insert materials such as metal can also be used, but an adhesive must be applied to the insert so that it bonds with our TPV.
Another way of combining incompatible materials is to design the part with mechanical locks so the molten TPV material flows into the locking area, creating a bond.
For low volume applications requiring insert molding, the inserts can be hand-loaded, but for higher volumes, robotic pick equipment may be a cost effective choice. Applications must be evaluated on a case-by-case basis as to which method is most cost effective.
