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Erwin Quarder Inc. in Grand Rapids, Mich., a mold maker and injection molder of automotive and medical parts, thinks it has found the next big thing in tooling. The eight-year-old company is among the first in the U.S. to use and to produce a new stack-mold concept that can lower part costs and add flexibility by operating each parting line separately and alternately.

The TandemMould concept was developed in Germany four years ago and marketed since then by T/Mould of Bad Salzuflen, which holds the patent rights. Quarder started using tandem tools after seeing T/Mould land more than 50 applications in Europe.

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Quarder started in 1998 as the U.S. branch of Erwin Quarder Gruppe in Espelkamp, Germany. The Grand Rapids plant began with four employees and grew to 80 workers and 20 injection presses from 66 to 330 tons. It provides services in tool and part design, process development, moldmaking, molding, and assembly. The U.S. operation generated $8.5 million last year.

Quarder is licensed by T/Mould to build tooling with two capabilities that a traditional stack mold cannot touch, says Wilhelm Kliewer, Quarder’s product manager for technical sales of tandem technologies. “The shot-size requirement from one parting line to the other with TandemMould can differ as much as 40%, allowing molding of parts with different injection and cooling profiles. This is not possible with a conventional stack tool. TandemMould also allows a molder to completely close off one parting line and run the press and tool in a single-face mode,” says Kliewer.

The key to TandemMould is a locking system that opens and closes the two mold faces in alternating sequence. Components mounted on the moving, center, and stationary platens lock one parting line while unlocking the other simultaneously. The injection press controller operates the lock/unlock mechanism.

“Since one parting line is open while the other remains closed, the daylight requirements are the same as a stand-alone mold,” explains Kliewer. “Also, alternating the shot to each mold means the screw does not need to be larger for this stack-mold approach.” A hot or cold runner can be used with the system. A tandem mold costs about 10% more than two stand-alone tools, but production savings can be realized in as little as six months, according to Kliewer. He says tandem tooling can cut floorspace requirements by 60% and overall costs by 40%.

The system has been used on presses of 20 to 2300 tons. The largest tandem mold Quarder has built in the U.S. has 4 + 4 cavities, while its German parent has used can 8 + 8 cavity tandem mold.

Saves time and space

One successful application of the technology by Quarder was a housing that holds the electronics for car-seat heating. Quarder took over two stand-alone four-cavity tools designed with hot runners and direct gating and converted them to a tandem mold using the same nozzle tips. “The customer wanted lower piece cost—that is why we converted the tools,” says Kliewer. Quarder changed the manifold of the tool so that it had an opening for melt to pass into either mold face.

“We produced both the 58-gram housing and the 39-gram cover in the same machine. You couldn’t do that with a traditional stack mold,” says Kliewer. Each mold has a cycle time between 32 and 34 sec, but overall cycle time is reduced since the cooling time of one mold face overlaps the injection phase in the other face. The machine opens one mold face after the end of holding pressure in the other face. That allows increased cooling time to improve part quality without a cycle-time penalty. “To make the parts with two conventional molds would take two machines running for two weeks, but with TandemMould we accomplished the same production goals in one week on one machine,” says Kliewer.

T/Mould plans to establish a U.S. office soon. To open the door even wider for this technology, Quarder will offer classes at a local Michigan university to teach the principles of TandemMould. Quarder will also hold “technology days” at its facility and build demonstration tools.