Sponsored By

December 1, 2001

4 Min Read
Rediscovering, unleashing the value of coinjection



This frisbee, coinjection molded on a single-barrel, 85-ton Milacron, is made of 33 percent scrap (see cross section, bottom).

The Bruderhof is a global organization of religious communes that was founded in 1920 in Berlin, Germany by Eberhard Arnold. Its members number in the thousands today, and they come from diverse backgrounds, yet they share a common faith and purpose, as well as all of their earthly possessions. Today, the Bruderhof has grown to consist of nine communities in three countries—the U.S., the U.K., and Australia. You can learn more about them at www.bruderhof.com

Hold on, IMMers. You're reading the right magazine. 

An agile, ISO 9001 commercial enterprise of the Bruderhof called Community Enterprises LLC (Rifton, NY) has been involved in captive injection molding since 1995. It has about 300 active QC-7 aluminum molds that it builds itself. The tools run on eight presses ranging from 44 to 400 tons. It produces three million parts a year, some with Hettinga's Helga liquid/gas-assist process. It has embraced lean thinking since 1989. And it presently enjoys global sales of $48 million. 

Feel more like you're reading the right magazine now? 

Community Enterprises also has developed and is now marketing a technology for coinjection molding with a press that uses a single barrel, nozzle, injection stroke, and recovery cycle—a press running unmodified molds, that is (see "Coinjection Process Promises Simplicity and Low Cost," September 2001 IMM, p. 143 for an initial report). 

Twinshot Technologies (TT) was formed by Community Enterprises to market this patented coinjection system. It has brought on board a well-known U.S. pioneer and leading coinjection molding proponent to assist it—Joseph McRoskey. 


Joseph McRoskey (right) has joined John Rhodes (center) and Joel Thomson at Twinshot Technologies to help them launch their low-cost, uncomplicated, and versatile Twinshot system to the worldwide molding community.

A Community Culture 
McRoskey was president and ceo of Co-Mack Technology (Vista, CA). Co-Mack specialized in coinjection molding. The company fell victim to the one-two punch of rising energy costs and a sluggish economy earlier this year and closed it doors. McRoskey now is president of an independent consulting firm, JMJ Management LLC (Carlsbad, CA) and has recently joined TT as a technology specialist. 

"Co-Mack's closing was in some ways a blessing in disguise," McRoskey says. "I never would have had the impetus to come to Twinshot. Also, as an outsider, I would not want to have had to compete against these guys." 

Community Enterprises helps finance the activities of the Bruderhof by designing and manufacturing furniture and different support systems for the disabled, among other things. 

John Rhodes, project manager, did not hesitate to give the green light to Joel Thomson, chief engineer and UMass Lowell grad, when he came up with the concept behind Twinshot. 

"Teamwork, consensus, creativity . . . we share all of our resources in our community," Rhodes says. "For our workforce, it's not just a job. It's a way of life. There's nothing stopping us from developing things that can improve our productivity or our bottom line—no board of directors, nor any corporate structure. We listen to our people and we use what we learn from them." 


Joel Thomson says no control or software modifications are required for the Twinshot coinjection system he invented. His two-in-one injection units run just like a standard shooter.

Coinjection Reborn 
Thomson saw coinjection as a means of reducing resin costs, consolidating parts, and improving the performance and appearance of many components molded in Rifton. But he was frustrated by the long lead times, the long ROI, and the mechanical difficulties he encountered with more traditional coinjection molding machines. 

The Twinshot system Thomson developed is coinjection in the truest sense of the word. A smaller, clutch-engaged, extruder inner screw for the core material is splined right into the motor driving a larger-diameter coaxial outer screw for the surface material. There is no relative movement between the two screws—the inner screw goes along for the ride. 

A special check valve was designed with a poppet valve inside of a check ring. The coinjection screw can be pulled for servicing just like a regular screw. The check valve is just as easy to change. 

TT intends for its Twinshot system to be royalty-free for molders. Licensed machine manufacturers will pay TT a royalty based on machine size. Systems are retrofittable to existing machines. McRoskey intends to help TT further refine its screw designs and to continue marketing the economic benefits of coinjection, in the truest sense of the word, to the world. 

Contact information
Twinshot Technologies
Community Enterprises
Rifton, NY
John Rhodes
(845) 658-7737

Joe McRoskey will present
a paper on the Twinshot
system at Molding 2002
in New Orleans March 4-6, 2002.
For more information, go to

Sign up for the PlasticsToday NewsFeed newsletter.

You May Also Like