Mold filling packing

TABLE 11.4 Data Needed for Injection-Molding Simulation—Advanced Mold Filling, Packing, and Cooling Analysis of Thermoplastics and Thermoplastic Elastomers ... 

Polystyrene. There are two types of expandable polystyrene processes expandable polystyrene for molded articles and expandable polystyrene for loose-fill packing materials. 

Common problems like insufficient filling-packing and poor dimensional control are often related to the gate size and design. Similarly, gate location is another important factor. They should be located in areas having heaviest cross-section of the part to assure fill-out and elimination of sink marks. Also their position should not facilitate the residual molded stress formation in the part, knit line formation. 

Molding a product (part) involves the three stages of fill, pack, and hold. The following guide provides a simplified example for IM plastics. 

Using continuum mechanics, ceramic powder packing can be analyzed for its mold filling capability. Powder packings are different from liquids in one important way, which is described by the coefficient of pressure at rest. 

The material properties needed for simple mold filling simulation are listed in Table 11.3. The material properties essential for advanced filling, packing, and cooling simulations are listed in Tables 11.4 through 11.6. The requirements are essentially the same for thermoplastics and thermoplastic elastomers, while in the case of reactive materials, such as thermosets, the main differences are the reactive polymer viscosity in place of melt viscosity data and reaction kinetics data. 

In Eq. 7.2, q is the heat flux across the melt and mold interface, which is not known beforehand. The mold cooling analysis is essentially coupled with the transient heat transfer in the polymer melt during filling, packing, and cooling stages. 

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