With competition becoming increasingly tough, management at Atlas Precision Molding (Arden, NC) knew that being a me-too molder just wouldn't cut it when trying to grow a custom injection molding company. That, coupled with a downturn in the markets the company serves, gave Atlas president Johann Hofschuster a new mission: to diversify and add new processes to establish the company as a niche OEM supplier.

Robert Bulla, sales manager for Atlas, which operates a 70,000-sq-ft facility with 34 machines ranging from 38 to 720 tons, notes that the company "saw the downturn coming" in the automotive and electronics markets, "but we still got hit." Bulla began doing some research on new processes and came upon wood-filled materials. He also found that the construction market was a prime candidate for what wood-filled polymers could offer. "I saw what was happening with decking products, which are mostly extruded," says Bulla. "So, I asked myself, why can't we injection mold this material?"

Armed with this knowledge, Bulla began seeking out customers in the construction market. He toured one cabinet-making facility and was amazed to see a large dumpster used to hold scrap wood. "They used six woodworking machines to make two parts, plus all this scrap," Bulla says. "I asked them, 'What if I could give you something that would take all this away?'"

Bulla quoted one job, and the injection molded part came in cheaper than its all-wood predecessor, which amazed the woodworking company. When Bulla showed the company how to amortize the savings of the eliminated machines, labor, inventory, and scrap, the return on investment for the mold was just 12 months.

Typically, the purpose of using wood-filled polymers is to add stiffness and enhance HDT (heat deflection temperature) in a commodity resin such as polypropylene, polyethylene, HIPS, or ABS. "The wood flour allows you to put added value into a resin, which typically you can't get unless you use higher-priced additives like glass or talc," explains Bulla.

The wood filler also increases creep resistance and gives plastic parts a wood-like appearance, while offering many of the qualities of working with wood. "It saws like wood and drills like wood, and at certain levels you can paint and stain it like wood," Bulla says.

Meeting the Demand
Bulla has found "a tremendous need" for wood-filled polymer products in the construction and furniture industries. "That's where it provides a lot of value," he notes. Although the extrusion process is cheaper, it also limits the types of products that can be produced using a wood composite material.

"With injection molding you can get complex shapes and provide a lot of added value that typically, when you're replacing wood parts, takes a lot of machining, routing, and other hand operations that can be built into an injection molded part," Bulla explains.

For example, instead of routing or drilling holes and other secondary operations generally required by traditional woodworking, snap features or even other mating parts can be molded into the part. "Wood-filled materials eliminate a lot of labor," says Bulla.

One thing Atlas can do with wood-filled materials is mold cabinet components, such as a one-piece drawer or a cabinet front panel, which is then fitted with an oak veneer or PVC film over the top for the white gloss look. Bulla points out that most cabinets are manufactured from treated compressed wood or particle board. These can easily be replaced by wood-filled polymer materials, providing a part that is stronger and cheaper, eliminates wood scrap, and is consistent in terms of quality.

Other projects Atlas is working on include wood composite thresholds for doors, spindles for deck railings, and fence post caps. "Wood composites provide added value, give customers the wood-like look they want or any color they want, while getting the added value of wood composites in a cheap resin like PP," Bulla notes.

Mold Requirements
Tooling for the wood-filled products Atlas molds comes from the company's moldmaking facility, Atlas Precision Tooling, located 6 miles from the molding plant. The facility employs 50 toolmakers and five design engineers, who are available to the company's OEM customers for part design assistance.

"We specialize in tools with multiple inserts, so we can build tooling that can accommodate various styles of the same product," says Bulla. "There are so many possibilities, especially in the furniture industry, for internal wood parts such as gliders inside a recliner, or anything painted to have a wood look, like sofa feet. It's a big market."

Bulla notes that at 40 to 50 percent loading, the material has a higher viscosity. That means a larger runner system is needed, but Bulla says Atlas has had success with hot runner systems as well. "We've found with wood-filled composites that we don't have the mold wear that we do with glass-filled and talc-filled materials," Bulla says. "But we do have to be generous with runner systems." The company has successfully injection molded parts that are up to 60 percent wood filled.

Molding with Wood
In process, wood-filled materials are no more shear sensitive than a calcium-filled PP, for example. "We've found that we're able to flow the material across parts up to 37 inches long and with a wall thickness of .085 inch with no problem," Bulla adds.

The material also lends itself to foaming. For example, a product with a 30 percent loading of wood filler can have a specific gravity of 1.05 to 11; foaming the product can bring this down to .8 to .9, depending on part design. "This allows us to mold large parts in smaller presses," says Bulla. "You don't wear out the press maxing out the tonnage. We mold a part 36 inches long in a two-cavity mold using 90 tons of a 500-ton press." Foam technology also gives the customer many added benefits, such as lower part cost due to weight reduction, lower cycle times, and better nailability.

Wood flour is compounded into a concentrate, allowing molders to use material with various particle sizes depending on the application and requirements. Atlas can tailor the mix to the customer's application based on wood requirements in a homopolymer, copolymer, or wide-spec material. The molder can also vary the wood mesh size for different looks. Using a special blender, Atlas adds colorant, foam, wood, polymer regrind, nucleating agents, and impact modifiers to create the desired material. It can also take crystal styrene, add a front-impact modifier, put the wood filler in, and come out with a low-cost resin with good gloss and paintability features.

Wood filler comes in a variety of types depending on which kind of wood is desired. These include pine, oak, white oak, or even materials like hemp or rice hulls. "Pine is easier to color than oak, but oak gives greater tensile strength and flex modulus," says Bulla.

Material costs for the wood filler vary, but typically average from $.38 to $.48/lb for a 40 to 60 percent loaded product. "Depending on what loading you're using, cost varies, but it's still a good price for a reinforced commodity resin," Bulla says.

Atlas' venture into the wood-filled polymers niche for injection molding is paying off for the company. Bulla notes that the moldmaking division has been booked solid since last September, and the molding division is looking to buy more presses. "You have to find a unique niche with all the competition from the Chinese," Bulla says. "We started out small but we're going gangbusters now."