Robert Joyce says gas-assisted molding is the best way to solve tough challenges of injection molding wood-plastic composite balluster spindles - the long pieces that run down vertically to support a railing on a deck or stairway.
``It's the perfect application for gas,'' he said June 16 at an open house for Gain Technologies Inc., which is supplying gas-assist technology for the project.
Gain could get into the spindle molding business if Joyce wins commercial orders. Gain would handle initial molding at its new, 34,000-square-foot headquarters in Shelby Township, near Macomb, Mich. Gain has six injection presses available for mold tryouts and limited production.
Joyce said he is working with some large decking companies, but he declined to give any details. His firm, Innovative Plastics and Molding, introduced the spindles at DeckExpo 2005 in Tampa, Fla., in February. The spindles contain plastic and wood flour, but they have a contoured shape resembling milled woodwork that was turned on a lathe. Decking companies were impressed with the rich wood surface appearance and IPM's ability to match colors and fade rates of specific brands of deck, he said.
Although extruded wood composite decking has enjoyed explosive growth, the spindle application marks an advance in the newer area of injection molding the material.
Gas-assisted molding uses gas, usually nitrogen, to push out melted plastic against the mold walls and create a hollow, finished part. Gas-assist cuts resin costs, but in the case of the long, wood-filled spindles, the gas is needed just to fill the part properly, Joyce said.
The spindles are made of high density polyethylene and polypropylene filled with 40 percent wood flour. That highly loaded material has to pack into a very long, thin spindle up to 36 inches long.
Joyce said wood composites cool down quickly once inside the mold. If the melt sets up too fast, that can cause problems with flow marks, or even lack of flow, when using traditional injection molding.
``It's cooling before you're even starting to push it,'' he said. ``But with the gas-assist process, you have the ability to push that material right into the mold.''
The gas quickly packs out the part, giving a good surface appearance. The wood is encapsulated in the plastic.
As sales rocket for wood composite decking, demand also has grown for matching railing. Other wood-plastic spindles are made by first extruding or blow molding the basic shape, then post-forming it into a contoured spindle. But Joyce said that process can tear the wood fibers or create condensation inside the part.
Some suppliers extrude a solid spindle shape, but Joyce said those shapes can't be given an ornamental look.
As for ornamental, Joyce visualizes exotic post-caps in the shape of pineapples, lions heads, golf balls, all made by gas-assisted injection molding to look like carved wood pieces.
An enthusiastic inventor, Joyce brings a background in machine technology, materials and wood-plastic composites to the spindle product. In the early 1990s, he left Allen-Bradley for Plastic Machinery Enterprises, where he tried to develop a way to extrude sheet made with waste wood and polypropylene for thermoforming. After attempting to get financial assistance from Michigan, Joyce closed the business in 2002 and worked for compounder Asahi Thermofil Inc., where he was assigned an account for gas-assisted molding appliance handles.
As Joyce learned more, he thought gas-assist would be ideal for making spindles for railing. He left Asahi in 2004 to work on the spindle full-time, and start Innovative Plastics and Molding in Lambertville, Mich.
Before Joyce made contact with Gain, he took the spindle idea to another gas-assist supplier. ``But they couldn't do it,'' he said. ``I had surface appearance issues, I had mold flow marks, dispersion issues, you name it.''
Gain molded IMP's sample parts. In addition to spindles and post-caps, Joyce thinks gas-assist molding of wood composites could make other thin, hard-to-fill parts, such as steering wheels for boats and riding lawn mowers.
Gain has focused on plastic auto parts and the spindles are a ``fantastic'' opportunity to help it diversify beyond automotive, said Gain Vice President and General Manager Jim Byrd.
``What we want to do is, with proprietary products like Bob's, we can take it from the idea to a finished part,'' Byrd said.
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