KENTWOOD, MICH.—Thin is officially in.
Thin-wall injection molding is the star attraction at Kentwood-based Plastic-Plate Inc. Workers there watch in wonder as a new thin-wall injection press, the first of its kind at the plant, produces electronic housing components at a breakneck pace that would make Carl Lewis proud.
The high-speed, high-pressure machine shoots out slimmed-down parts in less than half the cycle time of the plant's other 20 presses.
Still, Plastic-Plate engineering manager Garry Van Houten approaches the new machine cautiously. Like several other processors, the company straddles the fence about thin wall — at least today. The process breaks many rules of conventional injection molding.
``There's not necessarily a call for every part to be thin wall right now, but we know it's coming soon,'' Van Houten says as he picks up a computer shell piece. ``This buys us some time to get used to the technology before we decide whether to use it more extensively.''
Like it or not, thin-wall molding is entering the mainstream. The process, once thought to be an expensive and unproven novelty, now is getting a second look — especially by molders that, like Plastic-Plate, make their living from the consumer electronics industry. It is an industry where a product's low weight can trigger high sales.
In that industry, product pressures dictate ultrathin parts as narrow as 0.02 inch. That requires special equipment to mold resins at speeds higher than 35 inches per second and with pressures of more than 35,000 pounds per square inch.
The caution molders show for the emerging technology butts against the need by manufacturers of electronics equipment for thinner shells. To stay competitive, many shops molding electronic parts are folding thin-wall molding into their plans down the road.
But for an electronics industry in hyperdrive, down the road could mean tomorrow.
``You wouldn't recognize some of the products today from those of a few years ago,'' said Ed Korenman, spokesman for the Consumer Electronics Manufacturers Association in Arlington, Va. ``And thinner boxes are definitely a trend. That helps [manufacturers] fit more technology into each piece while keeping their products light in weight. Demand should keep growing.''
The $72.7 billion industry will mushroom to about $97.5 billion in sales by 2001, according to the association. Leading the charge are such products as wireless telephones, which have penetrated 43 percent of all U.S. homes, and personal computers, which have a 41 percent penetration.
Those figures might give manufacturers cause to celebrate, but they also give the plastics industry cause to pause. Work still must be done to understand thin-wall technology and know how to use it effectively, according to President Victor Valentine of Triple S Plastics Inc. in Vicksburg, Mich.
``People in the [electronics] industry don't quite understand what it means to make a part that's only 0.02- to 0.04-inch thick,'' he said. ``There are certain [speed and pressure] requirements that are crucial. And special design considerations around the part and for the tool must be met to handle production demands.
``Because of that, there's quite a learning curve that we must still go through.''
In fact, many European companies have shifted back to thicker parts after finding the engineering time too great to make the slender components, said Mark Matsco, manager of innovative technologies for Pittsburgh-based Bayer Corp.
``In thin-wall molding, you can see a lot of goof ups in surface quality,'' Matsco said. ``When you want a three-month turnaround to take a product from concept to production, you can't afford extra time to fix problems. What we've found in troubleshooting injection molds is that there are limitations to wall thicknesses and how far you can go.''
Performing the job effectively takes special, high-modulus resins that flow through the mold under the duress of extreme speed and pressure. It takes robust, multicavity tools with sequential valve gates that will keep their shape under those requirements.
And it takes customized presses that can cost at least 25 percent more than traditional injection molding machines. Parts from those machines must be made without cooling times needed for normal molded parts.
All of which make it a process still in its infancy, said Kurt Weiss, program leader for thin-wall molding at GE Plastics in Pittsfield, Mass.
``The plastics industry has developed pretty advanced thin-wall technology and parts that really push the envelope,'' Weiss said. ``Like anything else, it's an evolutionary process as well as a revolutionary one. We've been able to take small steps forward in the fast-paced [electronics] market.''
Companies such as Plastic-Plate, a division of Grand Rapids, Mich.-based Lacks Enterprises Inc., and Triple S Plastics in Vicksburg, Mich., are exploring the new molding frontiers. Both firms now have a single thin-wall press on which to learn the craft.
Plastics-Plate shifted to thin-wall production in August. The company, which operates three plants in the Grand Rapids area, purchased a high-speed press with a clamping force of 185 tons. The machine uses servo-driven robotic arms and special dryers and thermolator units to help process parts in under a minute.
The company, which specializes in parts for cellular phones, computer network hardware and hand-held electrical devices, has made parts as slim as 0.03 inch. Doing that has meant the use of special polycarbonate, ABS, glass-filled nylon and PC/ABS blends.
``There are definite advantages to thin-wall molding,'' General Manager Daniel Savickas said from the firm's 70,000-square-foot plant. ``We can get more shots per hour for our production runs and sell consumer parts with less weight. We're originally focusing on one machine, but we'd consider adding another four to five machines in the future.''
Including the new machine, the company has 21 injection presses with clamping forces of 50-1,000 tons at its Kentwood facility.
A few molders, such as Shieldmate Robotics Inc. in Itasca, Ill., are no strangers to thin wall. The firm, one of the largest North American producers of electronic housings, has made thin-wall parts for at least six years, said President Steve Matecki.
The thinnest part the company has made is 0.017 inch, Matecki said. Consider that a normal part thickness is 0.1-0.14 inch, or more than five times as thick. With more than 40 high-speed presses equipped for thin-wall work, the company does not expect much competition, Matecki said.
``At least we hope not, although we see more suppliers stepping up to thin wall,'' he said. ``But I think the investment to change over to thin wall could keep some companies out of it, at least to the degree that we're doing it.''
Equipment suppliers want to make certain that more molders try the new technology. Nafels, Switzerland-based Netstal Machinery Inc. built its first high-speed precision press in 1973.
The equipment maker's most important new feature has been to add a thinner screw and barrel that allow a smaller shot size covering the same projected area, according to Daniel Morris, director of sales and market development at Netstal's Fort Devens, Mass., office.
While the equipment can be more expensive, suppliers can gain a return on investment from both resin savings and higher production volumes, Morris said.
However, entering the market can be a bit difficult, he noted.
``Thin wall has taken on a greater and greater role during this decade,'' Morris said. ``But the part is more difficult to mold than a standard-fit part. When you fill in a part in a short period of time, you have to be careful of aesthetics and the geometries needed for snap fits and bolt lugs.''
Several new products could make a difference. Bayer is pursuing the use of film insert molding as a companion to thin wall. The laminated PC film would personalize a product, hide surface defects and add impact resistance, Matsco said.
``It's a beautiful way to hide [defects],'' he said.
Another possibility is the use of thermosets, currently a priority for equipment maker Hull/Finmac Inc. of Warminster, Pa. Together with Fiberite Inc. and its Enduron carbon-filled thermoset, the firms plan to sell a lower-pressure, compression molded alternative.
``The low pressures don't place as much stress on a part,'' said sales manager Mark Bahmueller of Hull/Finmac. ``The parts are more durable than with thermoplastics and they don't need coating, painting or a separate shield.''
The plan to install a thin-wall compression press at Fiberite's Winona, Minn., plant by year's end and begin offering demonstrations to customers.
One disadvantage of the process: Cycle times are considerably slower, taking as long as a minute. ``But the other benefits more than make up for that,'' Bahmueller said.
Whatever the future holds, one thing is certain: Processors are going to need to find ways to make thin-wall parts if they want to work for electronics firms.
``There are economic drivers for thin-wall parts,'' Weiss said. ``Besides, I don't think you're going to see anyone wanting to carry around a heavier laptop and cell phone or work on a larger PC. That's a safe bet.''
