Punching on demand
Heating system manufacturer punches what's needed - and nothing more
Until about a year ago, the staff at King Electrical Mfg. Co. manufactured parts by the thousands without much consideration of the actual demand for those parts. This doesn't happen anymore.
Dean Wilson has never been afraid of taking on a challenge. As executive vice president of manufacturing for King Electrical Mfg. Co., the heating products company that his father founded in 1958, he has tackled his share. But none has been greater than transforming the company's manufacturing into a leaner, demand-driven process.
Seattle-based King Electrical started making baseboard wall heaters 50 years ago when the accepted manufacturing approach was to produce as many parts as possible to minimize the cost per part. As the company grew, it expanded and evolved its product line to include fan heaters, cabinet heaters, and large commercial units, including the largest ventilating heater on the market at over 250 kW.
Until about a year ago, the fabricating staff manufactured parts by the thousands without much consideration of the actual demand for those parts. If a heater required 15 parts to build, the shop would carry out 15 large-batch operations of varying quantities, which created inventory imbalances. To build 500 heaters, they might make 2,000 of one part, 500 of another, 8,000 of another, and so on.
"We were a batch shop with too much of everything and not enough of anything. We'd have overruns of one part and shortages of another. We were always scrambling to get in balance," explained Wilson (see Figure 1), an industrial engineer with a master's degree in technology management and former General Electric technical sales manager.
Batched parts traveled first through a turret punch press, then a shear, then to bending—and before each, they got in line for processing. Nowhere was this more evident than the press brake area. Different forms within these batches required separate tooling setups. So, an operator would bend one set of forms using one tooling set, change tooling, reprogram the brake, then send the entire batch through again. With more customers expecting faster deliveries, King Electrical had to outsource a significant portion of sheet metal fabrication just to meet demand.
"Press brake operations were much more time-intensive than the turret press, so we'd have a queue of parts waiting to get on the brake," recalled Wilson. "That alone could add three to 10 days to lead-times. It was not an ideal situation."
Realizing that King Electrical needed to change to remain competitive, Wilson decided to overhaul the shop's manufacturing last year and move away from large batches to adopt lean principles, where customer demand triggers manufacturing, and the shop produces only what is needed, just in time. Machines, often grouped in cells, produce low volumes of different parts kitted together. Consider that order for 500 heater units again. Instead of running a batch of 2,000 of one part, followed by 500 of another, 8,000 of another, machine cells manufacture all the parts necessary for a group of heating units. This reduces work-in-process (WIP) and finished parts inventory, because the assembly department isn't waiting for the huge logjam of large batches making their way through the cutting and bending centers. Instead, as kits are completed, they can be assembled into the final product and shipped out the door.
That's lean basics. Shops may implement different iterations, but one underlying principle remains immutable: Lean must shorten the time between receiving an order and getting cash for it—and to do that, a job can't dwell on the shop floor for long. Unfortunately, Wilson saw too much dwelling on the floor.
Dwelling No More
The fewer times parts are handled the better, and on King Electrical's shop floor, parts were handled a lot, particularly in the bending area. So the shop considered options. To be lean, the company would need to flow parts through the floor in smaller batches, but with existing technology, the improvement would be incremental at best. The shop could have increased capacity by refining material flow alone. But in King Electrical's case, customers demanded even more capacity.
King Electrical first analyzed forming, its biggest bottleneck, including press brakes and other secondary operations. New brakes may have increased throughput, but not by much. Eliminating a portion of those bending operations entirely, though, was another story.
The company first tackled inefficiencies in making a 43⁄4-inch louver, which at the time required a secondary press operation. Wilson wanted to create that louver on the turret. This led him to a Finn-Power C5 Express hydraulic turret punch press with automatic sheet loading and tooling from Wilson Tool International® (see Figure 2). This included a custom toolholder that allowed a special 43⁄4-in. tool that fit in a standard 31⁄4-in. hydraulic upforming station.
The shop invested in other turret press form tools that eliminated additional press brake operations. A wheel tool, for instance, now creates the stiffening ribs necessary to improve the heaters' strength and durability. Before the machinery upgrade, parts were punched and then taken to a press brake.
"We've made great speed gains by doing ribs on the punch press because you eliminate the queue time and the parts are ready to ship," noted Wilson, explaining that WIP used to queue up at the press brake. "It would take five guys to do the same amount of work on a press brake. That's where we've found the biggest lean improvements."
Though the wheel tool eliminated the rib bending at the brake, several other press brake operations remained, including joggle bends that require the operator to bend one angle and then flip the part over to bend the reverse angle—a challenge when handling larger parts, not to mention time-consuming. It took 16 hours to put two joggles in 500 parts per month. The company now uses a rolling offset tool in the turret press that forms the joggle bend. It descends to the surface and traverses the part to apply the form. According to Wilson, this saves the company 192 hours a year.
"The rolling offset added some punch press time, but our new turret was only running about 60 percent capacity," Wilson said.
A wheel tool eliminated another, years-old bottleneck: The company had previously punched parts and then cut them individually on a shear, a secondary operation ripe for elimination. With a wheel tool, the company's turret press now can cut the necessary slits and shears under the turret without moving the part to a second machine (seeFigure 3).
The new system not only eliminated secondary operations, but made the primary cutting operation more efficient. For instance, the company faced challenges when fabricating venturis for certain large heaters. The venturis required round fan blade holes with diameters from 8 to 16 in. These were created on a punch press by nibbling in a circular motion, but this left scallops and took numerous hits to complete. Today the company uses the roller wheel tool to cut shears cleaner and faster. Holes that had taken up to five minutes are now cut in 20 seconds or less.
The wheel "acts like a large can opener; it cuts circles and we drop them out through a trap door," said Wilson.
Fabricating on Demand
Turret press form tools weren't the only alternative to improve efficiency. With enough tonnage, press brakes could have been fitted with special tooling, such as joggle die sets, that could make some of those forms with one hit of the ram. But the bends still require operator handling, and with lean practices, the less a part is handled, the better.
Today King Electrical manufactures parts as needed to meet demand, and WIP has dropped to almost zero. Moreover, the company no longer needs to outsource. Wilson said that he's working hard to get his work force onboard with the lean mindset, showing employees that making surplus parts isn't the same as being productive. It's actually a cost and an inefficiency.
"We still have plenty of work to do," Wilson said, "but the pieces are in place to make the transition complete.
"I'd rather have the right number of parts run and have some downtime than invest money in parts that we can't sell," he added. "Our biggest challenge has been moving from a labor-driven to a financially driven operation where parts are made only when needed."
The FABRICATOR is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971.