G&F Medical hikes capacity in LSR overmolding niche

Oct 18, 2012

G&F Medical has added two injection molding machines to its three-year-old 15,000-sq-ft facility in Danvers, MA this year and is in the planning stages to add two more in 2013.

The sister company of G&F Industries in Sturbridge, MA is racking up consistent annual gains in sales due to its focus on specialized liquid silicone rubber (LSR) molding, particularly overmolding on substrates ranging from polypropylene to nickel titanium alloys.

One example is a polypropylene housing for a filtration assembly used by pharmaceutical companies. G&F Medical overmolds a silicone gasket onto the housing that normally would have to be fastened with an adhesive in a secondary operation. Another part with significant potential is a silicone overmolded polypropylene check valve that could be used to replace an all-silicone assembly in an intravaneous system.

G&F Medical has tested different types of polypropylene and LSR to determine exactly the right match. Then specialized tooling needs to be designed so that the high heat of the LSR molding process does not degrade the polypropylene. G&F Medical mold engineers often specify inserts made from low thermally conductive materials that insulate the PP from the intense heat in the tool.

Patel said that the concept is very design dependent. "It's not possible to do this in every possible case because of the product design," he said.

Other materials that the company uses as substrate for LSR overmolding include nitinol nickel titanium alloy, copper, stainless steel, polysulfone, polycarbonate, and titanium.

Some of the metal alloys can only be overmolded with a specialty primer, and that's another area where G&F Medical has done its own testing and research.

More than 95% of the company's business is in medical. The remainder is defense-related.

G&F Medical operates 10 molding machines. The two machines bought this year were 55- and 110-tonne electric Engels for LSR molding. The company has 30 employees, up from 20 when the new plant opened in 2009.

The new facility has an ISO Class 8 clean room with the flexibility to add modular Class 7 or better clean rooms for special assembly projects. It has an open floor plan to improve production efficiency. The company is ISO 9001:2008 certified and is working to become ISO 13485 certified next year.

G&F Medical molds most of the thermoplastic parts used for its overmolding projects. A few made with more specialized plastics, such as Ultem amorphous thermoplastic polyetherimide are made by its sister company in Sturbridge. John J. Argitis is owner and president of G&F Industries and G&F Medical.

G&F Medical dates to 1973 when it was founded as UPCOA. The Argitis family bought UPCOA in 2007.

Growing interest in replacing PVC is a factor creating increased interest in LSR. Silicone use is also growing for medical applications partly due to advances in material technology, such as self-sealing LSRs. Suppliers working with G&F Medical include Bluestar Silicones, Wacker Silicones, Dow Corning, Shin-Etsu Silicones, Momentive Performance Materials, and Nusil.

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