I was once treated to lunch by an older engineer whom I greatly admire. He holds many complex patents and co-founded a plastics company that he sold to a large industrial conglomerate. As we talked our discussion turned to injection molding simulation software such as SOLIDWORKS Plastics simulation software.
He believed the software was unnecessary, and that the results rarely provided information that couldn't be gained from a conversation with an experienced mold maker. He thought that in choosing software over an experienced human, the “richness of the dialogue was lost”, a phrase that has stuck with me for many years.
This man could speak lengths about the paintings of Dutch masters, the intricacies of mechanical engineering in things as small as DNA molecules, and as vast as the universe. Any conversation with him was bound to be full of the richest dialogue. Any participant in that conversation was wiser and richer from the discussion.
Can simulation software replace human observation?
To some degree, he was correct that software cannot completely replace human observations. Life isn’t only numbers or color images on a computer monitor. The best engineers and the most interesting people understand not only how something works — but why.
Many of you, by visual inspection, can tell which areas of injection molded parts are prone to sink, and where to gate a part to avoid weld lines in certain areas. Large transitions in wall thickness will always cause sink and warpage because unequal thickness causes uneven cooling and shrinkage. Weld lines will always form when two flow fronts come together. Instead of relying on simulation software, these basics are best known and understood and are perhaps best learned from an interesting teacher.
Unfortunately, there comes a situation in every career where one has to disagree with those he or she admires, and those whose judgment is trusted. In many situations, a rich conversation with a mold maker might give valuable insight on where to gate an injection molded part, and that one should avoid rapid transitions in wall thickness. But what about when a part can’t be gated in the best location, or a rapid change in thickness is necessary? What problems will arise from a non-ideal gating location? How can a knit line be moved a few millimeters? How drastic will the shrink marks and warpage be?
SOLIDWORKS Plastics Simulation saves time by producing accurate predictions
With SOLIDWORKS Plastics, these questions can be answered. (Our upcoming webcast dives into these topics in further detail). In far less time than it takes to cut a gate and load a mold into a press for samples, SOLIDWORKS Plastics can simulate a dozen different gate locations and report air traps, sink locations, knit lines, fill times, fill pressures, warpage and shear. Such information greatly reduces time to market and the cost of product launch. So much information in such a short time is just too much to ignore.
In conclusion, part designers bring design intent to the conversation. A part designer should know why a part has to be thick where it is thick and thin where it is thin, or when a rib can be moved and when it needs to stay where it is. On these points, a good designer should be able to explain and defend the needs of the design. On other points, part designers aren’t the experts. On these points seek out the advice of mold makers and injection molders - their insight is invaluable.
When you have their advice, use SOLIDWORKS Plastics simulation software to verify it, then incorporate their advice and your simulation results into your design. Apply what you’ve learned and share your new found richness with the next young engineer looking for a bit of wisdom over lunch.
About the Author
Nathan Sneller is a mechanical engineer, entrepreneur, and adjunct professor. Before joining Fisher Unitech, Nathan graduated from Michigan State University, taught Mechanical Design at Grand Rapids Community College and ran an engineering firm where he specialized in the development of electro-mechanical products. In his current role, Nathan advocates for incorporating simulation software into the design process to shorten the development cycle, improve product performance and maximum profitability.