Addressing the challenge of injection molding regrind

The plastics industry continues to seek solutions to help it meet circular economy demands. As pressure builds for the industry to increase the amount of recycled plastics used in manufacturing, Imflux, a company based in Hamilton, Ohio, is helping to make this possible for injection molders. The company is partnering with machine and resin manufacturers and mold makers to incorporate its low-pressure injection molding technology.

Reduced variability

Oftentimes, as recycled content increases, injection molded part quality can decrease because of material variability. Imflux, a low, constant pressure molding technology, is designed to automatically adjust to material variability to maintain part quality. This ability to adapt to material variation is known as autoviscosity adjust within the Imflux software.

Historically, processing recycled resins has been a challenge for the injection molding industry. In conventional injection molding, a predetermined amount of material is injected at a fixed velocity to a set transfer location, with no allowance for material variability. Conventionally processing highly variable regrind can generate significant scrap as well as result in low repeatability, unbalanced tools, defects and downtime. With this technology, however, a conventional injection molding press can handle this variable material without the traditional unwanted outcomes.

Imflux, a wholly owned subsidiary of Procter & Gamble Co., Cincinnati, is helping its customers achieve their recycled content goals while maintaining quality and creating other improvements. Rather than relying on a constant velocity profile and predetermined transfer position, autoviscosity adjust uses proprietary algorithms to continually adjust and maintain low, constant pressure during injection. The technology is designed to be dynamic, adjusting in real time to material changes without operator intervention.

Demonstrated benefits

To demonstrate the capability of autoviscosity adjust, a conventional process and the Imflux process were compared during a conversion from virgin acrylonitrile butadiene styrene (ABS) to reprocessed ABS. No process adjustments were made during conventional or Imflux processing. Imflux outperformed the conventional molding process for dimensional consistency, demonstrating its ability to dynamically adjust to large material variations. Aesthetic improvements also were observed throughout the run, resulting from continuous optimization of filling pressure. Figure 1, above, provides an overview of the study while molding a standard American Society for Testing and Materials (ASTM) sample.

The technology’s success has transferred from the laboratory setting to the production floor as experienced by AGS Technology Inc., Batavia, Illinois. For the past 25 years, AGS has specialized in molding recycled resins. The company leads the industry in using recycled plastics to make high-functioning, quality parts for automotive and other durable goods manufacturers by directly molding up to 100 percent regrind. To improve its processing of this complex, problematic recycled material, AGS partnered with Imflux.

“The reality of the marketplace is such that OEMs (original equipment manufacturers) are averse to utilizing materials that will increase the cost of their products,” George Staniulis, vice president at AGS Technology, says. “In fact, with recycled, they expect a cost down from virgin resin.

“By utilizing Imflux, AGS efficiently processes 100 percent regrind, which is formulated to meet OEM specifications, thus bypassing the expense of reprocessing the recyclate and eliminating that cost, with the added benefit of saving a heat history,” he adds.

The technology also provides AGS with additional cost savings that are realized by a reduction in injection pressure. The company originally used a 720-ton injection molding machine to fill a two-cavity mold for an interior automotive part. Using the low-pressure molding technology, and without any mold modifications, AGS now uses a 500-ton press to mold the same part. Lower tonnage and injection pressure result in less wear and tear on the machine and mold and, even more importantly, lower energy use.

Additionally, this lower pressure processes at a faster cycle time, allowing AGS to produce the part at a 51-second cycle time as opposed to the original 55 seconds for conventional molding.

Reduced scrap generation

Using Imflux technology also significantly reduced AGS’ scrap generation, as the process now automatically adjusts to the variation in material, maintaining part quality.

The highly variable material, coupled with the high pressure of conventional molding, created intermittent flashing or short shots as well as read through from a back-side rib.

However, Imflux adjusts injection speed to prevent flashing and short shots and actually packs the part as it fills, eliminating read through. This is all done with no changes to the mold, meaning a cavity pressure transducer is not required. By employing the technology, AGS has reduced the scrap it generates from molding this part from 20 percent to less than 3 percent.

“Imflux is a game changer for AGS,” Staniulis says. “Lower costs and a better product: What more could one ask for?”

One of the largest obstacles to using regrind in injection molding applications is the high scrap rates and unacceptable part quality created by material variability inherently found in regrind. Innovations like low-pressure molding can help the plastics industry reach recycled-content objectives, establish a circular economy and provide energy savings.

Kelly Santini is safety and sustainability manager for Imflux, Hamilton, Ohio. She can be contacted at santini.kl@imflux.com. More information on Imflux is available at www.imflux.com.