How to Mold This ‘Impossible’ Part

First of all, it breaks a cardinal rule of injection molding: Flow from thick to thin, right? Well, this polypropylene part has a thick sprue that feeds two long, thin filaments, which feed into thick tunnel gates and relatively thick-wall, box-shaped parts (only one of which is shown here). Thick-to-(very) thin-to-thick again. Shouldn’t be done. Looks like it shouldn’t be possible.

And those filaments—talk about a flow-length to thickness (L/T) ratio! The filaments are 3 in. long × 0.030 in. diam. That’s a 100:1 L/T ratio.

Featured Content

5 Ways Resin Conveying Systems are Getting Smarter

Understanding—and Using—Decompression to Your Advantage

In-Depth Guide on How to Measure Color in Plastics

So why do this at all? It’s a demonstration part handed out by iMFLUX, the six-year-old subsidiary of Procter & Gamble that developed a molding process that uses constant low pressure to overcome many of the drawbacks of conventional injection molding. The result is said to be higher part quality, with lower molded-in stresses, and faster cycles—not to mention savings from lower injection and clamp pressures.

This part demonstrates the degree of control engineered into the iMFLUX process to ensure constant low-pressure filling. Any hesitation in flow through those long, thin filaments would cause instant freeze-off.

Got you interested yet? Learn about the latest developments in this novel process and what molders, machine suppliers, and consultants are saying about it in a feature in the upcoming September issue, written by Gene Altonen, chief technology officer of iMFLUX. In the meantime, you can read an article he wrote for us last year, introducing the process.