There are numerous occasions in which you will find the material comparison function handy. Whether it is to select a new material with a higher melt flow rate when short shot happens, or to determine the processing window for the sequential injection molding process, or to match the skin/core rheological and shrinkage properties in sandwich molding process, it is always easy to compare material properties using the Material Comparison function in the Material Wizard.

Here shows an example of comparing the skin/core material properties for a co-injection process. Gomes (2011) addressed that for a successful co-injection molding process, the two materials should have matching processing properties. It is suggested that the core/skin viscosity ratio should be between 0.5 and 5. Lower viscosity ratios would lead to breakthrough of core material, while higher viscosity ratios would lead to poor mold filling or a variable core thickness through the part.

Step 1. Material tab in Modify Run dialog box shows the skin and core materials.

Step 2. By clicking View/Edit, the material wizard dialog box appears and shows the materials used in the project.

Step 3. Right-click on the material and choose Add to Comparison List.

Step 4. In the Compare Material dialog box, users can select to compare by default process condition or user specified temperature range.

Step 5. Here we chose specified 230°C as the temperature for display and click OK.

Step 6. The viscosity profiles at 230°C for both materials are compared. For this case, the two materials have closely matched viscosities throughout the entire shear rate region.

Step 7. PVT properties can also be compared. This combination shows the two materials have similar shrinkage ratio as the temperature decreases. The slopes of the curve, i.e., change of volume at constant weight, for the two materials are almost identical. Serious warpage is thus unlikely to happen.