Why are these men smiling?

"We never work on Sunday, and we don't like to work on Saturday," Greg Stepeck admits cheerfully. Stepeck, general manager of the plastics group at Wiremold in Rocky Hill, Conn., is playing golf on a sunny Saturday with his three set-up men. Thanks to just-in-time manufacturing, they escape work on most Saturdays, even though summer is the busiest time of year for Wiremold, a proprietary maker of electrical parts and components.

Wiremold's plastics group runs a lights-out plant with 22 injection presses and 12 extruders. It makes over $40 million worth of products annually, while keeping only $600,000, or four hours' worth, of inventory. JIT at Wiremold was set up seven years ago with the help of Japanese consulting firm Shingijutsu Ltd. It affects extrusion of PVC profiles, injection molding of 500 different small parts, and ordering of parts from outside vendors. Molded-part orders can be as small as six pieces. Orders for extruded profiles (used for cable raceways) may be as few as 50 pieces.

Masters of quick change

To run this lean, Wiremold has mastered injection mold changes as swift as 40 seconds from last part to first good new part. Hot-runner tool changes and color changes can take five minutes. Switching extrusion dies, downstream calibrators, and water baths take just 5-15 minutes, depending on the complexity of the profile. Different products are permanently assigned to specific machines. The appropriate molds sit on specially constructed storage racks with rollers and rails directly behind the molding press or extruder.

All of plastics production runs with a technical team of only three set-up men. To maintain their JIT pace, they must be sure that new jobs start up without a hitch. "There are no bad parts," Stepeck says. "We lose only two or three press cycles every time we change a tool. That's why we can afford to make only six parts before a tool change."

Extrusion changeovers are simplified by piggybacking one tool onto another. For example, building an embossing roller onto the first calibrator means both can be installed at once, saving a half-hour. A large flow chart behind the extrusion machines charts how much time has been taken out of the process.

Even a five-minute extrusion die change isn't fast enough for Wiremold. The company has embarked on an ambitious program over the next several months to get extrusion set-up times down closer to injection mold tool changes. Team leader Stepeck is so confident that they will hit their target that they plan to reduce the number of extrusion lines and still increase output. The plan is to replace a dozen smaller extruders (2.5-in. and 3.5-in. single-screws plus GCH conical twins, all from Davis Standard) with eight of Davis-Standard's new GC-94 high-output parallel twin-screw machines, which are designed for up to 1100 lb/hr of PVC profiles.

Follow the colored magnets

An elaborate "kaisan" product-tracking system is critical to Wiremold's JIT operation. It uses a visual identification system of fiat colored magnetic squares that are moved from one tracking board to the next to indicate progress of a parts order.

When finished goods are shipped from one of Wiremold's two warehouses in Tennessee and Nevada, a "pick ticket" is taken off the order and scanned by a barcode reader. The coded ticket indicates all the parts and profiles used in that product. Scanning the ticket starts the process of replacing those components back in Rocky Hill, where magnetic squares for those parts are placed on a large stock-supply board.

When inventory of a given component is four hours from being exhausted, the work order moves to a board representing the work cell where it will be molded or extruded. Each machine in the cell is represented on the board with a row of six 40-minute time slots, adding up to four hours of production time. Orders are color-coded for priority, so operators can decide which parts to make next.