A few members of our simulation team recently attended a 2-day plastic injection molding seminar at California State University Chico taught by Joseph Greene, Ph.D. who is a Department Chair and Professor in their engineering department. This is a great seminar that has been attended by other members of the simulation team in the past. We went back to get some hands on experience in the injection molding process and to test whether the solver enhancements for SOLIDWORKS Plastics 2016 improved accuracy.

After some basic instruction on the different types of plastic materials that are used in the industry as well as an overview of some of the manufacturing processes that are used to create plastic parts, it was time for hands-on experience in their lab. We were able to make parts using the blown film and blow molding machines and then finished the day with making a license plate frame using the injection molding machine.

Back in the office, I wanted to use SOLIDWORKS Plastics to simulate the injection molding process for the license plate frame we created during lab for the seminar. In class, Joe mentioned that he has his students use Plastics to predict injection pressures, the flow profile as the melted plastic flows through the part, and weld lines in order to minimize cosmetic defects and prevent structural failures.

To set up the analysis in SOLIDWORKS Plastics 2016, I started by creating virtualized runners from a sketch, specifying the injection location, and defined the same parameters used during lab:

Sketch For Runners, Virtualized Runners, And Injection Location

Material: Polypropylene

Fill Time: 30 seconds

Melt Temperature: 446 °F

Mold Temperature: 122 °F

Injection Pressure Limit: 7977.08 psi

The result for the injection pressure at the end of fill of 2732.88 psi, was close to the pressures we were seeing during lab.

Pressure At End Of Fill

Looking at the results for the flow profile, we can see that as the flow field passes over the mounting hole locations on the license plate frame, 2 fronts are beginning to come together which will result in weld lines. Weld lines will also be occurring towards the end of filling the top and bottom halves come together. The results in the flow profile closely matched the results we were getting in the physical part with visible weld lines in the locations where 2 fronts were coming together.

Flow Profile in SOLIDWORKS Plastics

Flow Profile from a short shot

Weld lines

Although small, if we take a look at the sink mark results which are depressions on the surface of the molded part, we can see the same areas of depression in the physical part.

Sink marks

I would like to thank Professors Joe Greene at CSU Chico for giving us the opportunity to take their Introduction to Plastics seminar and use their state-of-the-art plastics lab. If you are interested in learning more about plastics and the plastics industry in their 2-day seminar, you can contact Joe Greene by email at jpgreene@csuchico.edu.

For more information, contact us today at Hawk Ridge Systems, get a SOLIDWORKS Plastics quote or check out our YouTube channel. Thanks for reading!

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