Secondary Injection Unit Provides Primary Benefits for Molder

One of the first to utilize Mold-Masters’ newest, largest auxiliary injection units —the E-Multi 5 (EM5) — Core Technology Molding Corp., Greensboro, North Carolina, was able to produce a 2-shot “bumper” component for a rolling toolbox cart four times faster and at half the cost compared to the prior production setup. “The previous process couldn’t make sellable parts in the same day,” explains Brandon Frederick, Core’s engineering manager. “Prior production had two different processes, two different tools and two operators. We’re half the cost — we didn’t need two machines.”

Made for a well-known American industrial tool brand, the plastic bumper component is a decorative and functional all-plastic part assembled onto a large, rolling, automotive mechanic toolbox cart. Featuring high finish and surface quality requirements, the bumper is roughly three feet in length, and incorporates two colors and clean shutoffs for a crisp, sharp imprint of the company brand, including the trademark icon. The design calls for red nylon 6/6 substrate to be overmolded with soft TPU in a 2+2 mold, with the black rubber framing the red logo.

“The logo aspect,” Frederick says, “that’s everything to the customer, and it’s really precision molding at that point. This is not a shoot-and-ship part, that’s an A surface, and we have to make sure our process is robust.”

Like Core, the customer is based in the Southeast — a region wanting when it comes to molders with 2-shot capabilities in the medium tonnage range (which is one reason Core got into multimaterial molding back in 2019). Core has a lot of exposure and expertise in automotive but serves a variety of markets beyond that, including medical, packaging and outdoor power equipment, among others.

The EM5 was used to inject the red nylon 6/6 substrate while the black overmolded rubber was injected by the machine’s primary injection unit. In the design, the EM5 injected 864 g for the nylon 6/6 substrate, while the machine’s primary injection unit delivered the 800-g TPU overmold with a total cycle time of 70 seconds for the 2+2 mold. Normally, Frederick notes that the auxiliary unit would handle the rubber overmolding, but because the nylon 6/6 could degrade if the residence time was too long, Core utilized the EM5’s smaller barrel and shot size for the nylon. Shot sizes for the EM5 range from 550 to 1,200 g, says Dave Silva, Mold-Masters’ director of product development.

The EM5 is attached to the molding machine in an L-shaped configuration on the non-operator side of the press with an injection point on the hot half, stationary half of the tool. E-Multi’s can be installed vertically, horizontally or at any custom angle to accommodate the cell. Freise says that due to the EM5’s size, Mold-Masters expect most of its installs will be horizontal.

The biggest advantage for Core in shifting this production to two-shot versus insertion and overmolding was staffing. “The biggest piece is the labor aspect,” Frederick says. “You go from taking molded substrates and placing them in the tool, dedicating half an operator for just putting parts into boxes, to now where machines do all the work in one press with one mold.”

In addition to efficiency, Core said lead time and total cost helped make the case for the EM5. When quoting a dedicated 2K injection molding machine with a rotary table, Core was given lead times of 50 to 52 weeks, compared to 14-16 weeks for the EM5, which was slightly less than the quoted mold-build time for the job, creating a scenario where the EM5 could be installed and ready for the new tool to start production on day 1.

“The EM5 supports the same concept, but costs less, has a better lead time and helps us be more competitive because speed to market these days is everything,” Frederick says.