Growing interest in medical molding has spurred plastics molders to check out liquid silicone rubber, according to speakers at Boy Machines Inc.'s open house.
Boy focused on LSR and medical molding during the event, held April 24 and 25 at the injection press maker's headquarters in Exton.
``We made a conscious decision to center on medical molding, and a big part of medical molding today is LSR,'' said Boy Machines President Robert Koch.
Darrel Hill, national sales manager, said Boy has built LSR machines for more than 30 years. Another strength, he said, is the fact that Boy makes only small-tonnage machines, maxing out at 100 tons, since many parts for medical devices require insert molding on small-cavitation molds
Boy demonstrated medical molding on four of the five presses it ran at the two-day open house. One press ran LSR - a vertical Boy 22AVV molded small medical O-rings on a 16-cavity press.
LSR is gaining attention from plastics molders, as they look to medical molding to offset declines in other U.S. markets, according to officials from the materials, molds and pumping equipment sectors at the open house.
``We do see in the marketplace, with a lot of the traditional business, the only growing business seems to be the medical market,'' Hill said in a presentation. ``More people are inclined to start now looking at LSR molding or medical device molding, to build their business because the plastic is going offshore and down south. So they're more open to looking at the technology more.''
Although liquid silicone rubber - a liquid that gets pumped in through a water-cooled nozzle, and is cured to a thermoset inside the heated mold - seems to be the opposite of thermoplastics, which are cooled down in the mold, the machinery is basically similar, said Robert Pelletier, sales and marketing vice president at Fluid Automation Inc. The company in Wixom, Mich., makes pumping systems for LSR.
Pelletier said centers of the LSR industry are California for medical and industrial parts, the Minnesota-Milwaukee area for medical and the Ohio Valley for automotive. Traditional compression molding rubber companies move into LSR, because it offers fast cycle times and cuts out labor for trimming parts. But Pelletier said most of the new customers for LSR are coming from the plastics industry.
Plastics newcomers need a high level of technical support for rubber molding, said William Inman Jr., technical service representative with Dow Corning Corp., which supplies LSR materials.
Hill said some plastics molders are unsure about the technology. ``But it's really not a black art,'' he said.
Pelletier said a lot of plastics molders ``get their feet wet'' by retrofitting an existing injection molding machine to run LSR. If they win new business, the molders often buy new LSR presses.
Good, specialized molds are the key to successful LSR molding. Rick Finnie II, president of M.R. Mold & Engineering Corp. in Brea, Calif., gave a presentation on ``flashless'' molds. A vacuum pump removes air from the mold before final clamping.
Boy's Mike Lemon outlined a conversion to LSR molding at Dialight Corp.'s plant in Roxboro, N.C. Dialight specializes in light-emitting-diode technology used in traffic signals, cell phone towers and lights for heavy-duty vehicles.
Dialight is a Boy customer for injection presses to run plastic. But when the LED maker got into an epoxy material for a high-volume optical lens, it invested in transfer molding machines. The company was running a 400-cavity mold on a 4½-minute cycle, with a high scrap rate of 65 percent, said Lemon, Boy's regional technical sales manager for the Southeast.
The parts, with lots of flash, dropped into a tray under the machine, where an operator had to pick through them to sort good parts from bad.
``The parts were actually quality checked three different times, and after the part was assembled, they had a 25 percent reject rate,'' Lemon said.
Boy converted Dialight to liquid silicone, installing a Boy 35A LSR press with 38.5 tons of clamping force and a 1-ounce shot size. The turnkey system included a mold from Kipe Molds Inc. of Placentia, Calif.
Lemon said the Boy machine turns out the same number of parts on a 10-cavity mold, running a 28-second cycle, with no flash. ``There is no wasted material. It's completely automatic,'' he said.