The Superior way to implement lean manufacturing

The management team at Superior Tube Co. Inc. knew that success in lean manufacturing would require input from everyone at thecompany. The main drivers of its product flow project are Clyde Walters and Jane Humphreys (left and center), members of United SteelworkersLocal 9455-0, and Jason Zaremski, right, a member of the administrative team.

The word legacy has two definitions, one a noun and one an adjective. When used as a noun, it has a positive connotation, referring to an inheritance, gift, or bequest; when used as an adjective, it’s anything but positive, referring to outdated and obsolete equipment or software. If you had visited Superior Tube Co. Inc., Collegeville, Pa., in the early 2000s, you would have found that the company had two legacies, one of each kind.

The first was the company’s expertise in drawing small-diameter tubing, a foundation that the company has continually built on since it was founded in 1934. Its first order, for vacuum tube components for the rapidly expanding radio industry, was for 25,000 lengths of 0.040-in.-OD tubing with wall thickness between 0.001 and 0.0018 in. Focusing on small-diameter tubing made from specialty alloys, the company’s knowledge of metallurgy grew broader and deeper, which positioned it to supply products for many applications that would grow exponentially in the coming decades: nuclear, medical, aviation, and space exploration.

The other legacy concerned the equipment. It was actually a two-part legacy, based on the equipment age and equipment locations. To this day the company uses the draw benches it purchased and installed in the 1940s and 1950s, and although they are still going strong, in the early 2000s they had no modern features. Some of the capabilities that manufacturers rely on these days, such as diagnostic systems for troubleshooting and monitors to measure cycle time and equipment uptime, were unavailable to Superior.

The other legacy concerned machine locations. The draw benches were clustered in one area. The pointing machines, which crimp the tube ends before drawing, were clustered in another, and they weren’t near the draw benches. The cropping and deburring machines were not co-located, even though one process feeds the other. Quality control stations were here, annealing furnaces there, and so on.

“It was a traditional layout,” said John Reinhart, the company’s director of product development. “It was organized by process, not product.”

Many of the company’s products needed several draws with intermediate annealing. Some products also needed a trip through the pickling bath to improve lubricity. Most batches of tube criss-crossed the plant many times before going to the final inspection and packing area.

In the early 2000s, the company was at a crossroads. It had exited some markets in which it had been a pioneer and had watched as competition from low-cost, foreign manufacturers chewed into its market share. The company wasn’t on its deathbed, but it wasn’t as healthy as it once was.

The future wasn’t certain. Making the company available to a buyer, either through merger or acquisition, was one possibility. Fighting its way back to regain what it had lost was another.

Two things were sure. First, lean manufacturing held a lot of promise to rejuvenate the company. Second, the company had a long way to go to put a lean manufacturing program into place. It would have to develop plans for a new shop layout, or layouts, based on product flow; it would have to test a couple of layouts to see which one yielded the biggest benefits; and then it would have to make substantial changes in the company’s processes, procedures, and culture to capture everything lean had to offer.

The phrase “hurry up and wait” may have originated in the armed forces, but the military doesn’t have a lock on this sort of thing. A time study conducted by Superior showed that, like other manufacturing shops organized by process, non-value-added time was greater than value-added time.

Superior Tube Co. Inc. used several strategies as part of its lean initiative. In addition todeveloping a new plant layout based on product flow, it designed several pieces ofcustom-made equipment and switched from large storage racks to small mobile carts(background, at left). Two members of the product flow team, Jane Humphreys and JasonZaremski, discuss a tilting table that uses gravity to drain excess ID lubricant. This taskformerly was done with one of the overhead cranes.

“When we first reviewed the data, I was shocked,” said Jane Humphreys, one of Superior’s equipment operators and a member of the bargaining unit, United Steelworkers Local 9455-0.

“We were always busy,” she said. “As soon as I finished one order, I started working on the next, but a time study revealed that we worked on the product just 10 percent of the time. The rest of the time it was either sitting or moving around the shop.” Ninety percent of the time the tube spent on Superior’s premises was unproductive, non-value-added time.

Some of the orders were handled more than 100 times and traveled 4 miles throughout the facility. The cumbersome layout was compounded by the reliance on overhead cranes. In many cases, the needed crane was at the far end of the building; the draw bench operators waited 20 minutes, on average, to move a load of tube.

Crane availability wasn’t the only problem. Sometimes crane operator availability hampered production.

“OSHA requires a license to operate an overhead crane, and on occasion we didn’t have enough licensed operators on duty,” Humphreys said.

No manufacturer would waste crane time on small loads of material, and this contributed to a related problem.

“We had a lot of work-in-process (WIP),” Humphreys said. “We had a large holding area next to the annealing furnaces. When the material came out of the furnaces, it was moved to storage racks. It then went to one of four preparation areas for end pointing and lubrication.” These areas were inventory points, and each of the 11 draw benches also was an inventory point.

In addition to providing a place for material to sit, often for lengthy periods of time, every inventory point had the potential to be a roadblock—literally in the way of traffic—contributing to congestion on the shop floor and to the 0 percent non-value-added time (see Figure 1).

The conventional, process-oriented floor setup created additional problems that contributed to inefficiency in other ways.

Advancing Flexibility. Conventional manufacturing relies on a small number of large-volume runs. This strategy prevails when machine setups are time-consuming and inventory space is relatively inexpensive. The drawback is that this type of system isn’t flexible. A broken tool, a machine taken out of service for repair, or a late shipment of raw material sends the supervisor scrambling to come up with a solution to keep the product moving.

Two members of Superior Tube Co.’s Kaizen Promotion Office, Clyde Walters and JaneHumphreys, review the use of the company’s custom-made material lifters. One set ofarms lifts tube by the bundle from the material handling cart. A second set of arms sets thebundle down on the other side of the lifter, next to the draw bench.

If the system could be changed so that the operator had several small orders queued, he could simply move on to the next order while the supervisor straightened out the problem that halted the first order.

Coordinating Efforts. The conventional manufacturing model relies on operators to push material through the system. This is a simple method that doesn’t rely much on communication or coordination. As long as the operators at Station A are busy and pushing inventory along to Station B, and those workers are sending a steady stream of product to Station C, and nobody is idle, the push model seems to work efficiently.

The problem is that without communication and coordination, the system doesn’t work efficiently. Without a system in place, workers often prep too little or too much material for the next production step, either leaving the next station idle or wasting a lot of time. In some cases, they work on orders that don’t have priority, thereby making the customer wait.

If the system could be changed so that all of the efforts were coordinated, the product would flow through the plant, in appropriate quantities. Orders would get filled and shipped more quickly because no time would be wasted building unnecessary inventory.

Walking Less, Working More. Another problem is a variation on “hurry up and wait.” The manufacturing industry inadvertently developed its own version: “Wander around and wait.” When the equipment isn’t arranged in a logical fashion, shared tooling isn’t stored centrally, and peripheral processes—for example, quality control inspections—are performed at too few stations that are too widely dispersed, equipment operators have to walk from one area to the next, looking for the station with the fewest number of operators waiting in line.

If the system could be changed so machines, tooling, related supplies, and peripheral processes were available in the right quantities and located conveniently, the operators would waste a lot less time on every order.

Lean manufacturing projects often take years to complete and involve countless details and refinements, but the foundation usually is just a few big concepts. At Superior, the lean manufacturing process would address five major tasks:

Superior’s lean manufacturing program wasn’t as orderly or as fast as knocking down a row of dominoes, but indeed its plan to get product to flow through the plant had the same effect: Every time the team encountered an obstacle, it eventually knocked it down.

Material Handling. A big breakthrough came when the company realized it could eliminate the stationary storage racks and replace them with mobile carts.

“We put wheels under our inventory,” Reinhart said.

It’s still WIP, but mobile WIP has little in common with stationary WIP. Wheeled carts eliminated the 20-minute wait—the average 20-minute wait—for a crane. Suddenly every operator was also a material handler. It was no longer a specialty duty restricted to the crane operators.

“Nobody needs a license to move a cart,” Humphreys quipped.

The cart concept was a big success, but Superior didn’t fill the place with carts. Congestion caused by too many mobile carts isn’t much better than congestion caused by too many stationary racks. Each prep cell has two carts, one incoming and one outgoing, and each draw bench likewise has two carts.

Plant Layout. The first proposed lean layout was a workcell that consisted of one pointer, one coating station, one draw bench, and one saw. The product flow was excellent, but from a labor standpoint, it wasn’t workable. This arrangement required two operators at the bench and one each at the pointer, coater, and saw. If the company had replicated this for all 11 draw benches, it would have had to hire many more workers to staff every cell, and most of the staff would be standing around waiting most of the time. The draw bench operators would work nonstop, but the workers at the pointer, coater, and saw would work sporadically.

“We would have increased labor and idle labor at the same time,” Reinhart said.

The team went back to the drawing board to find the right equipment ratio. It did a series of time studies on all of the machines and found that one prep station could feed two draw benches, and five draw benches could share one saw.

Next, the team looked at peripheral steps. For example, the shop floor had just three quality control stations, which could have been called hurry-up-and-wait stations. The draw bench operators wasted a lot of time in line, waiting to measure dimensions or weights. The lean team doubled the number of these stations and outfitted them with identical equipment. Even if a scale isn’t typically needed next to a particular draw bench, it has one anyway, so any operator from any workcell can use any quality control station.

“All of them are interchangeable, for all tests, regardless of the draw bench,” Humphreys said.

Color Codes and Labels. To make the big transition from a push system to a pull system, Superior supplemented the written work orders with a color-coding system. Every cart is color-coded, as is every draw bench, and the prep stations are labeled with a letter, A through D. The carts are further labeled to indicate incoming or outgoing material. The incoming material and corresponding carts are clean except for the fresh lubricant. Tubes leaving the draw benches are covered in used lubricant, metal fines, and bits of debris picked up from the drawing process, so segregating the carts prevents cross-contamination.

The job board, which is used to trigger and track jobs, uses the same color coding. This system provides an intuitive, immediate way for anyone to determine the status of a specific order. It also provides a quick way to review the status of all of the current orders.

Material Lifters. Replacing cranes with carts cleared the way for dozens of other improvements, but one question remained: How would the draw bench operator move an entire bundle of tube from the cart to the draw bench? Formerly a crane would deposit a bundle of 100 or so tubes into a trough next to the bench, so the company would need a new way to move the bundles.

Superior staff developed a custom lifting system that uses a series of arms to lift tube bundles from the cart (see Figure 2). After the first pair of arms lift the bundle, a second pair scoops up the bundle and deposits it onto a conveyor, which moves a few tubes at a time into the trough.

“The tube lifting system holds bundles of tubing but isn’t really a storage system,” Humphreys said. The tube doesn’t sit there long, and it’s ready to go as soon as the last tube from the previous batch is drawn. “It’s part of the bench. It’s not a storage rack. Tube doesn’t pile up there.”

The lifter has three sets of arms, so while the operator is drawing the tubes from the first bundle, a second bundle is already on the arms, staged and ready to go to the draw bench. A third job usually is nearby, on the bench’s incoming cart. One draw bench, three bundles, no waiting.

By the accounting definition, WIP is any product that is not raw material. At Superior, the phrase could be updated to work-in-motion (WIM). The color-coding and other labeling systems helped transform the old push system into a modern pull system; the material handling carts dissolved the big-loads-of-tube-in-big-storage-racks way of doing things; and the streamlined plant layout reduced the lengthy transit times needed to move the material from station to station around the plant. Taken together, these elements transformed Superior’s operations so that when an order now is posted to the job board, the system runs like clockwork. The equipment operators know where to go and what to do.

The transformation to lean manufacturing has restored the company’s health. Employees no longer question the future, wondering and worrying about a possible sale or merger. Its vitality is measured in the improvements it has achieved since starting down the lean path: 50 percent reduction in cycle time, 33 percent reduction in WIP inventories, and 50 percent increase in on-time delivery.

The lean initiative has led to other improvements, notably in quality, Humphreys said. The lifting arm system has made the operator’s job easier while improving the company’s products. Before the lean initiative, when the company was moving large loads of tube by crane, the draw bench operator had to dig through a through a big pile of tubes to retrieve the next one for drawing. The long, thin-wall, flexible tubes that are Superior’s specialty invariably would get tangled, and any slight burr on the end of a tube would scratch the OD of several adjacent tubes as the operator pulled it from the pile.

These days the operator can jog the lifter system to kick out just five or six tubes at a time onto a conveyor belt, and this motion unscrambles the tubes before they get to the operator.

The storage racks also contributed to unintentional mixing of materials.

Occasionally a load of heavy, thick-wall stock would end up on top of a load of less robust, thin-wall inventory, leading to many dings and misshapen tubes. In other cases, a few lengths of tube would end up in the wrong bundle, resulting in more than a little confusion on the part of the hapless draw bench operator. The resulting nonconforming tubes would appear to be the outcome of a quality control problem, when in reality the root cause was a logistics problem. For a company that has 80 to 150 active jobs on the floor on any given day, preventing material mix-ups is critical to getting the jobs done right and on time. Eliminating the storage racks, instituting the use of the carts, and color-codingeverything have essentially eliminated material mix-ups.

“Our lean program has improved our product segregation and identification, which in turn helps with tracking and quality,” Humphreys said.

Increasing the number of quality control stations also had an unintended yet related benefit: It spread quality control inspection knowledge further throughout the company.

“These days more people are more knowledgeable about quality control,” Reinhart said.

A separate but related project has transformed the ease with which the executive team can measure the company’s operational efficiency. Where the company once was lacking information, specifically the pull forces and cycle times of the draw benches, it now is rich in data. Before moving the benches, the staff determined that it would upgrade the drives—they were still running on the original systems—and incorporate supervisory control and data acquisition (SCADA) systems, providing a steady stream of measurements.

The company’s accomplishments are all the more impressive considering that the lean team didn’t have the luxury of starting with the proverbial clean slate. It had to work with some of the company’s legacy. It didn’t move to a new building, so it was restricted to using its existing floor space. More importantly, an evaluation early in the process determined that moving degreasing equipment and the pickling bath wouldn’t be feasible. Because these are pre- and postannealing processes, respectively, the annealing furnaces had to stay put as well.

It also had some restrictions on where it could place the draw benches. The notable restriction is that the spacing has to accommodate the turn radius of the material handling carts, which typically haul 20-ft. lengths of tube. Finally, it didn’t discard its cranes. It still uses them, but in a way that works in harmony with the lean initiative, mainly in moving large bundles from the degreasing station to the furnace and from the furnace to the pickling area.

So, despite keeping some of its prelean layout and processes, the company still has managed to upgrade and update its processes and along the way achieved many of the improvements lean programs are known for—a better on-time delivery rate, a stronger balance sheet, and a brighter future.