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Stahl Specialty Co.: success in cellular casting.

By embracing the principles of cellular manufacturing, this permanent mold foundry has increased production and efficiency of its finished cast components.

Lean manufacturing. Cellular manufacturing. Just-in-time delivery.

To many foundrymen, these manufacturing industry terms of the 1980s and 90s are blue-sky ideas that can't be applied to a process as complex as metalcasting.

But as Stahl Specialty Co., Kingsville, Missouri, sees it, that statement would be wrong.

"Cell manufacturing has been a tremendous asset to our company by involving our people in the total process of making the product versus only a segment of the operation," said Jack Moore, president and CEO.

"Cellular manufacturing has eliminated the hassles of inventory and stockpiling of cores and castings and allowed us to achieve, in some cases, just-in-time delivery," said John Fleeman, Kingsville South foundry manager-processing.

For Stahl Specialty, a 960-employee aluminum caster, cellular manufacturing is a way of life that has allowed it to grow from a 700-sq-ft facility in 1946 to today's 500,000-sq-ft manufacturing operation that is one of North America's largest producers of permanent mold castings. By combining the benefits of this lean manufacturing approach with its value-added services, customers such as Caterpillar, General Motors (GM), John Deere, Mercury Marine and Bosch have turned to Stahl Specialty as their complete answer for finished cast components.

Diversified Growth

Stahl Specialty was founded by Glen Stahl in 1946 in Kingsville, Missouri, to produce items, such assanding drums and lathe faceplates, for home workshops. Operating out of a 20 x 35-ft rented building, the company's big break into metalcasting came when a local lawn mower producer, Goodall Manufacturing, asked it to cast a "G" insignia to attach to its lawn mowers. This initial relationship proved to be the launching pad.

In 1949, Goodall contacted the firm about casting a lawn mower deck for a new rotary mower. Unaware that the rest of the foundry industry believed lawn mower decks were too big to cast in permanent mold, Stahl Specialty built the tooling. A few years later, this type of casting represented 95% of the foundry's production.

But Stahl knew that long-term growth for his organization wasn't going to be only in lawn mower decks.

"Stahl Specialty started seeing the market for permanent mold aluminum castings develop in the 1960s and began positioning itself to be a producer of a broad range of aluminum casting products," said Moore.

Throughout the 1960s, Stahl began casting gas grill housings, cooking pans, truck parts, macro-computer components, playground equipment - "anything we could put our hands on." The diversification Stahl Specialty was searching for didn't stop at the foundry door. In 1960, it became one of the first aluminum foundries to offer in-house heat treating services. In 1963, the foundry completed construction on a tool and die facility and, in 1965, it added a building for steel fabrication and machining. Stahl Specialty became a one-stop supplier for its customers by providing value-added services.

Accompanying these service additions was a growth in the casting business. In the 1950s, Stahl Specialty was pouring less than 20,000 lb of aluminum per day. By 1967, it was pouring 42,000 lb/day and by 1973, 100,000 lb/day. Stahl Specialty continued to add production space in Kingsville and opened a new 10,000-sq-ft foundry in Warrensburg, Missouri, in 1970. But, as production continued to increase, core and casting inventories also increased, and efficiency and casting quality began to suffer. The traditional approach to manufacturing wasn't satisfying the diversity of parts (more than 300) it was suddenly casting.

"In the 1970s, we recognized that to become more efficient, reduce lead times and inventories, and to attain higher quality levels, the lean manufacturing approach of casting cells was the way to go," said Milford Cunningham, vice president and COO.

Cellular Structure

According to J.T. Black in his book, The Design of the Factory with a Future, a manufacturing cell is a collection of production machines arranged to produce part families or parts that share similar operation processes. By arranging their facilities into cells, manufacturers can obtain higher efficiencies at lower labor costs.

Today, Stahl Specialty has 40 casting manufacturing cells - 15 at the Warrensburg facility and 25 at the Kingsville site.

The pinnacle of Stahl Specialty's cellular manufacturing was achieved last year with the start-up of its casting cell at Kingsville for the production of an inboard V6 exhaust pipe for Mercury Marine Corp. The foundry designed an all-inclusive 900-sq-ft manufacturing cell, where a semi-permanent mold part is fully cast, processed and ready for shipment every four minutes [ILLUSTRATION FOR FIGURE 1 OMITTED].

With a $30,000 investment, Stahl Specialty combined existing equipment - a 4500-lb dry hearth reverberatory furnace, a 42 x 42-in. tilt pour casting machine, a S[O.sub.2] core station, a pneumatic vibratory shakeout system, a pressure test system, a cutoff saw and a belt buffer - with a new monorail conveyor to produce a manufacturing cell, or an "all-inclusive foundry." The four-employee cell is capable of producing 1800 exhaust pipes per week.

"This cell is successful because the workers take ownership of the cell and the castings it produces," said Fleeman, one of the designers of the cell. "The operators have a hand in the casting from beginning to end so they are able to work through and solve all problems that may arise. In addition, we have eliminated that mindset that 'once my job on a part is complete, it isn't my problem.'"

Each of the exhaust pipe cell operators are qualified to work in any of the cell's stations, and welcome the variety, said Fleeman. In the near future, a reclamation system will be added to the cell for core sand reuse.

"Before, when we cast a part similar to this, forklift operators were constantly transporting cores and castings back and forth from the warehouse, and we could only guess production figures within 100 castings. But now, if a customer wants an exact count of where production is, I can walk over to the cell and give them an exact count within minutes," said Fleeman.

The workers' ownership of the cell and its castings and the simplicity the production process has provided has been vital in the successful casting of difficult to produce exhaust pipes. Because it is a semi-permanent mold casting (15% of Stahl Specialty's castings are cored), a new defect - sand inclusions - is a concern. In addition, since the 356.2 aluminum part is pressure tested, Stahl must pay particular attention to gas porosity and shrinkage for fear of leaks. Also, the large size of the part (3 x 2 ft), in conjunction with thin wall thickness (0.2 in.), make feeding the casting difficult.

"In the design of the manufacturing cells, the more upfront thought that is given to the layout, the better," said Fleeman. "We make paper dolls and CAD/CAM designs of the layout to teach the workers how the cell will operate. It is vital to bring the workers in on the early stage of design to solicit their input and foster those feelings of ownership so the result is an optimal casting."

The Mercury Marine cell is the foundry's only all-inclusive cell. The majority of the casting cells perform many of the casting-related duties, yet stop short of the value-added services Stahl performs elsewhere within its facilities.

Another cell at Kingsville produces 40-lb brake housings for John Deere via semi-permanent mold casting [ILLUSTRATION FOR FIGURE 2 OMITTED]. Within this cell, one employee melts aluminum in a 4500-lb dry hearth reverberatory furnace, operates two tilt-pour casting machines, sets the S[O.sub.2] cores, performs visual inspection and removes the sand core. Due to the part's complexity and volume, final cleaning, finishing and machining is performed in Stahl Specialty's production machining department in Kingsville.

The 2-year-old John Deere cell can produce 950 brake housings per week in a 600-sq-ft manufacturing space. Prior to the cell, two operators, each with their own furnace and casting machine, produced the parts. Now, by automating the pouring and providing the operator with the air balancing manipulator to handle the cores and castings, the foundry has freed up labor and equipment without losing production. If more manufacturing space around the cell is opened up, said Fleeman, a core machine can be added, eliminating another outside step from the process.

Tilt Pour Automation

"In the perfect manufacturing situation, we would cast each part and pack it for shipment in the foundry in its own cell," said Cunningham, "but the reality is that with heat treatment, machining and all the other value-added processes we provide, this isn't possible on every casting."

The typical Stahl Specialty cell contains a dry-hearth reverberatory furnace for melting, either single, multiple machine or a carousel tilt pour casting system, manual or robotic pouring, a cutoff and buffing station, and no more than two operators. But, the foundry has developed them for high production and also developed the value-added service facilities to handle that production. Although not lean manufacturing in its truest sense, it helps the foundry maintain low inventories and efficiency.

The focus for high production revolves around the automated tilt-pouring casting technology (see sidebar "Automated Tilt Pouring Eliminates Human Element").

"The automation of the casting process and, in some cases, the automation of the pouring process releases workers to perform other tasks within the cell, such as cutoff and inspection," said Cunningham.

The development of the automated tilt pour process, according to Cunningham, was due to "natural evolution." During the 1950s, in pursuit of a more tranquil mold fill (thus lessening turbulence and its related defects), Glen Stahl and his foundrymen began to manually tilt the molds at a 45 [degrees] angle. At that point, the evolution was to slowly pivot the book molds during pouring from 45 [degrees] to the stationary 90 [degrees] position. From there, it was "simply" automation of the manual tilting. In 1959, Stahl Specialty built the first of its Autocast tilt-pour permanent mold casting machines. In 1970, the foundry built its first high-volume eight-station rotary permanent mold system.

Value-Added Components

The diversification thrust of the 50s, 60s and 70s developed Stahl Specialty into a full-service manufacturing company. With a recent $2 million investment to further automate the production machining department, an upcoming investment to further automate tool and die manufacturing, and its heat treating operations, the organization will be better able to deliver the value-added services to the more than 38 million lb of castings expected to be shipped in 1998.

"Being a full-service source for our customers allows us to work with them on the design of the part, build the tooling, produce the casting, fully machine the part in-house and assemble it to a finished component," said Moore.

These value-added services follow the same philosophy of cellular manufacturing. If one supplier has full responsibility (casting, heat treating, machining and assembly), it then takes on a natural ownership for the entire part.

A casting that illustrates Stahl Specialty's value-added services is a lower control arm [ILLUSTRATION FOR FIGURE 3 OMITTED] the foundry produces for GM's Pontiac Grand Am and Oldsmobile Alero automobiles. Beyond the casting, machining and heat treating of the A356.2 aluminum part (and three other similar part numbers), the foundry assembles the part to a ready-to-use state for the customer's assembly line.

"We perform value-added services on 60% of the castings we produce," said Dick Kneip, sales manager. "Assembly is just another way to respond to the needs of the customer."

The foundry rivets a ball joint and installs two bushings (purchased from an outside vendor) in the fully-machined casting to provide GM with a finished component. It also has been performing sub-assembly for Caterpillar since 1988 as well as several other customers.

Casting a Future

The manufacturing cell environment has allowed Stahl Specialty to successfully diversify its product base and value-added services, while increasing production and efficiency. The future will have to be more of the same.

According to Moore, as OEMs continue to look for ways to reduce their products' weight, they increasingly turn to aluminum castings for answers.

"There clearly has been a movement over the last 10-15 years to substitute lighter material for heavier material, and aluminum has benefited," said Moore. "Although Stahl Specialty sees this direction sustaining itself for the next 10 years, we also recognize that competitive processes or materials also will play a future role in these same markets.

"We must be prepared to look for new opportunities, as the one thing that is commonly heard around Stahl Specialty is 'The only thing constant is change."

Stahl Specialty Co. Kingsville, Missouri

Facilities: Kingsville and Warrensburg, Missouri.

Manufacturing Space: 500,000 sq ft.

Casting Data: aluminum (primary alloys: A356.2, 256.2, 256.1, 357.1, 319.1 and A444.2).

Expected 1998 Shipments: 38 million lb.

Molding Processes: permanent and semi-permanent mold casting.

Value-Added Processes: engineering design, tool and die making, heat treating, machining and sub-assembly

Markets Served: automotive, diesel engine, trucks, food industry, marine and construction.

Major Customers: Caterpillar, General Motors, John Deere, Outboard Marine Corp., Ridge Tool, Detroit Diesel, Mercury Marine and Bosch.

Employees: 960.

Year Founded: 1946.

Top Staff Officials: Jack Moore, president and CEO; Milford Cunningham, vice president and COO.

RELATED ARTICLE: Automated Tilt Pouring Eliminates the Human Element

Stahl Specialty developed its automated tilt-pouring technology to eliminate the human element from the existing permanent mold process. With tilt pouring, the casting cycle begins by introducing the molten aluminum into a pouring basin, which is attached to the permanent mold. The casting machine then tilts the mold, generally through a 90 [degrees] arc, allowing the metal to flow consistently from the pouring cup into the runner system. The mold opening has a tapered entry into the runner system to create a damming effect to hold the surface oxides and impurities in the pouring basin and an angle plate is added to the other half of the mold directly across from the pour cup to prevent metal spillage.

The automated tilt-pour process promotes a controlled rate of metal entry into the mold and directional solidification, which results in minimized metal turbulence and a well-vented casting with less oxide inclusions, porosity and flash. In addition, the process allows for a simplified gating system. In many cases, the casting cavity can be part of the filling and feeding system, thus the process lends itself not only to bottom and side filling, but also to direct or top gating.

"The tilt-pour process is easier to design for because you are given a way to minimize the influence of filling rate - a major problem with casting aluminum," said Rick Bain, engineering supervisor. "We design with that in mind and it opens up opportunities in yield, size of part and tolerances."
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Article Details
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Title Annotation:includes related article on automated tilt pouring
Author:Spada, Alfred T.
Publication:Modern Casting
Article Type:Company Profile
Geographic Code:1USA
Date:Dec 1, 1998
Previous Article:Enlist a casting 'champion.'.
Next Article:Controlling the production of compacted graphite iron.

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