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February 1, 2000

8 Min Read
IMM's Plant Tour:  Attention to quality is rewarded

It is a fact often overlooked in our fast-paced culture that when a company dedicates itself to producing its wares to the highest standards of quality, the logical outcome is success. GW Plastics is no exception. The custom molding company has made a habit of attending to quality, and this philosophy shows up in both its products and the bottom line.

Founded in Bethel, VT in 1955, GW has grown by 15 to 20 percent annually since a 1983 management buyout from then-owner Sohio. In the past five years the company has doubled in size, with two plants in Vermont, one in Texas, and a fourth in Arizona.

Precision in Bethel
After passing through the front office spaces, visitors to the Bethel plant are first met by a 4000-sq-ft cleanroom set up with 10 presses ranging up to 85 tons. Although certified to Class 10,000, GW runs the medical molding area as a Class 100,000 cleanroom, with more stringent specs for air quality and contaminant reduction.

Three of the machines (50-ton Van Dorns) are placed in separate workcells that each produce parts for a blood analyzing device. Ventax robots pick up four parts at a time and drop them into tubes separated by cavity. The parts are then shipped to customers in the same tubes. A 7-ton Nissei with .23-oz shot size, also located in the cleanroom, gives GW the added ability to produce micromolded parts.

Robotics are a way of life not only in the cleanroom, but also on the general molding floor. To improve cycle time, sprue and/or part removal robots are installed on all of the 42 machines located here. Because GW focuses on high-volume, precision molding, it also uses quick-mold-change systems and an automated finished goods conveyor to expedite processing and shipping times.

On a mezzanine separated from the molding areas all materials are dried and conveyed to molding machines via two Motan material drying and handling systems. Resins are dried in a central area, then sent by dry-air vacuum to each machine’s small Motan hopper that is fitted with an autoweigh chamber.

One drying system supports the machines located in the general molding area and consists of 46 drying bins with capacities from 60 to 800 lb. The 10-machine medical molding cleanroom operates on a separate system that contains 10 drying bins. Both systems use closed loop reclaim of regrind. One outside silo feeds directly into the drying units, and gaylords below the mezzanine feed material up.

Quality Built In
All GW molding sites share integrated manufacturing and quality systems. The GW plant layout and equipment are identical at all facilities. "Although we statistically qualify all new tooling or transfer tools at our Tech Center," says Jim Symonds, director of customer service, "they must be requalified when they reach our production floor. Having a standardized approach at all facilities reduces the turnaround time required."

Rather than waiting for quality problems to arise on the molding floor, GW begins eliminating them at the start of a project. A quality engineer is assigned to work with each project engineer and with the customer during planning, design, moldbuilding, and mold qualification stages.

During this period specifications are developed, including functional testing, gauging systems and methods, dimensional requirements, aesthetic standards, and characteristics that will be monitored via SPC. Once the mold is built, engineers conduct a process capability study and a complete layout inspection to ensure products will meet requirements.

Once it hits the production floor, every job has a packet that contains its quality data and samples. After process capability is proven and final approvals are received, quality assurance and manufacturing departments continue to monitor each of the SPC characteristics with various traditional control charts. In addition, GW technical staff calculate and monitor real-time Cpk values, with a company standard of 2 or greater for all jobs.

SPC monitoring is done every four hours, and parts are checked during each shift inspection, in which up to 200 dimensions are measured. At the machine limits are set by the process capability study, and parts from any press that diverge from those limits are sent to a scrap bin via diverter chutes. "We will divert any product that is not within a 3 standard deviation limit," says Bob Carpenter, manager of quality assurance.

GW’s goal is Six Sigma manufacturing, according to Carpenter. Currently, every process must be twice as good as it needs to be, and every department establishes a continuous improvement plan to meet short and long-term goals.

Several other groups within GW contribute to overall quality levels. One, the engineering department, is located on the second floor of the Bethel facility. It provides design consultation services and program management for part design, prototyping, material selection, mold design, and mold construction issues.

Nearby to the Bethel site is a 27-acre compound in Royalton, VT, where the Mold Making Div. and Technical Center are located. Both buildings were inaugurated in June 1998. Adjacent to the Tech Center is the newest plant (Plant 4), which is operated under procedures similar to an actual cleanroom.

Royalton Resources
With its staff of 50, the 12,000-sq-ft Mold Making Div. operates 24/7, and during half of that time machines are attended by just enough staff to make sure they keep running as they should. That’s because most of the equipment is CNC-controlled. This includes a Makino high-speed machining center outfitted with an 80-position tool changer. Machine tools are tied to Unigraphics (20 seats) and SDRC I-deas CAD/CAM systems with 3-D solid modeling and translation capabilities for IGES, DXF, and Parasolid.

Roughly 50 percent of the tools that GW runs are built here. "We typically receive CAD data from customers via e-mail, an ftp site, or DAT tape," explains Scott Rosen, director of the division, "and most often, these are not manufacturing-ready—no draft, seals, or clearances. We work with both our engineering department and customers to create a solid model with manufacturing and moldability changes—draft, ejector pins, bosses, and other modifications aimed at bringing down cycle time. Customers then review this version prior to moldbuilding. We find that the system helps to cut down on back-end engineering changes."

Four years ago tool designers at the division switched to 3-D solid modeling and found an exponential improvement in productivity. All EDM electrodes are now solid models, according to Rosen. "There are no pencil sketches any longer," he says. "Solid models allow us to check whether or not a tool’s dimensions are the same as the customer’s CAD file. And it is much faster to put the part geometry into the tool design and subtract the part to create the tool."

Molds are next sent to the Tech Center to be qualified on one of three Van Dorn presses (80 to 300 tons). That means producing a robust, consistent process that will be repeatable on the shop floor. Every mold and part receives a viscosity vs. flow rate curve to determine optimum fill times. Many of the mold designs undergo moldfilling analysis as well.

First runs are often conducted at the material manufacturer’s suggested settings, and then a window of high and low parameters is set. Taking the midrange, or nominal, set of process parameters, parts are then run for dimensional consistency. Results, charted from highs to lows, help the Tech Center zero in on the optimum process.

Plans at the Tech Center include bringing in a 110-ton two-shot press in a joint venture with Van Dorn to prove the feasibility for production. GW recently decided to specialize in two-shot molding, and is building quality into this process as well.

In adjacent Plant 4, two-shot applications are already under way. Currently, the shop floor houses 10 presses, but the plant was built to hold 14 machines and will probably reach that level by the end of this year, according to Symonds. Technicians run this plant using cleanroom procedures—hair nets and no floor storage. Jobs here are cross functional. Two people are responsible for materials handling, running the machine, and setting up the tools. The ultimate goal for this facility is to be a 12-hour, two-shift, lights-out operation.

Planning Ahead
Talking with Symonds after the tour is over, it’s clear that GW has no plans to rest on its laurels. At Plant 4, new presses continue to be added. "We may build another cleanroom as well," he says.

As for the end markets, Symonds and other GW management believe that the health care market will grow quickly along with the automotive and consumer/industrial markets. "We’re focusing our sales and marketing efforts and production capabilities to meet this growth," adds Symonds. "As companies within these markets consolidate and reduce their supplier base, we hope to be the beneficiaries." In fact, a focus on marketing segments on the plant floor seems to make sense at GW, and Symonds foresees that this will continue.

What about forecasts for additional facilities? "We are looking seriously at Mexico," he says. "This is where many of our customers are, and we can seed the new plant with this business."

On the process side, GW plans to specialize in micro-, lights-out, multishot, and insert molding. It will also focus on precision gears. As expected, there will be no letting up on process control. "It is vital that we target improvements in our response time to customers," says Symonds.

Contact information
GW Plastics Inc.
Bethel, VT
Jim Symonds
Phone: (802) 234-9941, ext. 128
Fax: (802) 234-9940
Web: www.gwplastics.com

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