Prototype lesson learned: Always check for mirror images — one costly mistake led to a checklist update that saved future molds!  Source: ChatGPT

Many years ago, after spending about a decade in the plastics industry, I was hired as a project engineer and mold designer by a custom molding and mold manufacturing company. Since I had no prior experience in mold design, I faced a steep learning curve. One of the first molds I designed was a single-cavity prototype mold for an automotive rear window release rod. The rod featured two bends: the top connector was bent toward the front, while the bottom was bent toward the rear.

We usually held a design review before starting the mold build, but my supervisor informed me that it wasn't necessary this time since it was just a prototype. I went ahead and designed the mold, which was a simple open-and-shut design with two steps along the parting line. After the mold was built and the sampling took place, I was shocked when the toolroom supervisor presented me with a newly molded rod. The top connector was bent toward the rear, while the bottom connector bent toward the front, creating a mirror image of what the part should have looked like!

Featured Content

How is an Aluminum Mold Energy-Efficient? READ MORE

Your Guide to Smarter, Faster Mold Design READ MORE

What You Should Know About Injection Mold Safety Straps READ MORE

Toolmakers are sometimes blunt. He told me, “You shouldn’t be a mold designer! You should be working at McDonald’s!” with a few other choice words added!

I later met with the toolmaker who built the mold and my supervisor to

 

 

 

 

Sharing Manufacturing's Most Human Moments  

Canon Virginia Inc. celebrates the real-world moments that unite shop floors everywhere. We hope that by sharing industry stories together, we can all laugh, learn and grow. After all, even in world-class operations, things don’t always go according to plan — but that’s where the human side of manufacturing shines. So, the next time you’re stuck or something throws a wrench in your plans (perhaps even literally), reach out to us because Canon might be the moldmaking and manufacturing partner you need.
cvi.canon.com

discuss how to correct the error. They were able to cut out the center stepped rod from the cavity and core blocks, remove material from the backs of one A-side block and one B-side block, create two spacers, and make new center blocks with the correct steps. This approach saved the most time-consuming and expensive connector ends. The mold was sampled again, and the prototypes were accepted by the customer, which led to a multi-cavity production mold being built correctly the first time!

After this learning experience, we added a line to our mold design checklist: “Will the part, and not its mirror image, be produced?” I also decided that, even if I have a simple mold and no mold design meeting is scheduled, I will always go through the mold design checklist personally to ensure that I don’t forget or overlook any details.

It was an expensive mistake I made, but it could have been worse. That simple addition to the checklist later saved at least one other costly error related to mirror images!