The challenge of using co-injection molding process lies in the undefined interface between 1st shot (skin) and 2nd shot (core) material. After the core enters the cavity, there are two materials flowing at the same time inside the cavity. The skin/core distribution is thus determined by the flow behavior of each material, not by the cavity design alone! This unique feature of co-injection process poses difficulties for product designers and process engineers. Without proper analysis tools, molders struggle to optimize the gate location and to maximize the core content.
Based on its successful 3D simulation techinique in the Gas and Water Assisted Injection Molding, Moldex3d R11 provides complete solution for the Co-Injection Process with benefits as follows:
- Design changes of gate location can now easily be verified to ensure proper skin/core distribution.
- Skin thickness results are provided; even assymetric distribution of skin material such as common cornering effect can be estimated.
- The core penetration location helps designers maximize the core content. For the controlled breakout process, the core melt front evolution after penetration can also be simulated.
- The effects of varying processing conditions such as skin/core injection speeds, temperatures, and even delay times are all incorporated into calculation.
- Warpage prediction is based on the skin/core distribution in the product and their relative stiffness. The elemental stiffness information can further be used for the built-in stress solver or even output to other structural analysis software.
- Material wizard provides material comparison tool to match rheological properties such as processing winodws and shear rate dependent viscosities. PVT behavior can also be matched to prevent severe warpage caused by asymmetric shrinkage due to uneven skin/core material distribution.
The steps of comparing material properties can be found out in the Tips and Tricks session in this issue.