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How can Plastics users check for quality of adhesion in two-shot or insert overmolded parts?

Damon Tordini

See the following articles for background information:

Overmolding guide (www.polyone.com)

Six steps to ensuring bond strength in rubber to metal bonding (www.flexan.com)

How to Optimize Adhesion in Hard-Soft Overmolding (www.ptonline.com)

The synopsis of these articles is that there are a larger number of factors that can affect the quality of adhesion, and many of these are the chemical composition of the two materials (and their compatibility), the surface quality and cleanliness of an insert, and other properties that are not directly simulated by SOLIDWORKS Plastics.

However, two large factors are the temperature of the materials, and the fill speed/injection pressure. Materials such as TPE have an ideal adhesion temperature- too hot or too cold compared to this temperature and the strength of the bond between the two polymers (or polymer and insert) goes down.

This would be best viewed by a cross-section of Temperature (using solid mesh); making sure to assign the correct material properties to the inserts will improve the realism of these results. See slides 10 and 12 for visual examples of these plots in the presentation "Plastics_Examples.pptx", located in the HRS vault under Engineering\Presentations\Demos\Simulation\Plastics

Temperature could also be plotted over time using the XY Plots capability (with nodal results) to determine if desired temperatures are maintained long enough during cooling.

Additionally, molding setups with higher pressure (shorter fill time) will improve adhesion. Pressures at end of fill will show this result most clearly.

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