Alloy engineering defies gravity: by encouraging process improvement while managing three diverse casting techniques under one roof, Alloy Engineering has advanced beyond your traditional metalcasting facility.

For more than 60 years, Alloy Engineering and Casting Co. (AECCo), Champaign, Ill., has exhibited its mobility to keep up with the times. As the metalcasting industry evolved, the company seized opportunities to tap into more markets and processes and moved beyond a traditional green sand facility.

The first shift from green sand was in AECCo's centrifugal casting facility, installed in 1964, and in 1975, a nobake molding system was added to augment the green sand line. Although the company's production capabilities increased, there was still more to be gained.

The most beneficial investment for the company was the development of a counter gravity casting (CGC) operation in 1992. Through CGC, the majority of AECCo's output gradually has shifted from low-volume traditional casting to high-volume production casting, which has been consistently profitable for the company.

Currently, 60% of AECCo's production is CGC with its main market in the automotive industry, The remaining 40% splits evenly between centrifugal and green sand, both of which cast components for a variety of markets including heat treat, automotive, marine and food processing.

Because CGC is a new process (developed in 1972), AECCo has managed both old and new metalcasting facilities within one building. Even though this could pose separation within the plant, the company focus--the commitment toward continuous improvement--keeps the employees united and the facility advancing.

"Some of the employees work back and forth (between facilities), and if they need help from each other, they can get it," said Jose Gomez, GCG operations manager. "It's a good relationship between all the employees. If we don't make ourselves better, we're not going to compete."

In With the New

AECCo's jump into CGC was not achieved over night. Even though the process carries the majority of the company's production, it took nearly a decade to get it to where it is today.

AECCo first delved into the CGC process to cast low- to medium-volume stainless steel components, such as catalytic converters for the Chevrolet Camero and exhaust manifolds for the 4.6L Lincoln--Mercury engine. Officials at the company had taken note of a variety of new casting methods coming into play and saw the opportunity to take advantage of a new process to further boost the company's penetration into the automotive market.

AECCo was sold on the capabilities the Hitchiner Manufacturing Co.'s, Milford, N.H., reverse fill casting process, CLAS, could deliver. CGC allowed for castings produced at temperatures only 100F (38C) above the metals' melt temperatures, and the molten temperature from furnace to mold always is within 15F because no ladles are needed. The process also can cast sections as thin as 2 mm thanks to a smooth fill aided by vacuum suction. Further, because the CGC molds include non-traditional gates and risers, the process can achieve yields as high as 80%.

Not long after the company's first installation of a CGC line, automotive markets began gravitating to more powerful engines. Engine designs for commercial trucks demanded hotter exhaust temperatures and called for the converter to be placed closer to the manifold. This posed a problem for automotive OEMs as the current materials in ductile and high-silicon irons were incapable of sustaining such high temperatures. Stainless steel was the answer. Lighter weights and thinner walls, which could be achieved through CGC, were mandatory.

Looking to improve its capabilities in CGC, AECCo collaborated with Metal Casting Technology (MCT--a joint venture between Hitchiner and General Motors (GM), Detroit) and in 1998, as part of a $9 million investment and three months of down time, renovated its CGC system. The company's objective was to increase its throughput rate and Production volume level, and the result was a production contract with GM. At the moment, with the exception of prototype orders, AECCo's CGC production system is devoted primarily to five different manifolds for GM's 8.1L medium- and heavy-duty truck engines.

A Countering Process

Unlike a traditional gravity pour, CGC brings the molten metal from the bottom up. AECCo's CGC process begins with a coldbox molding machine that produces the cope and drag of a vertically parted mold at a rate of 100 molds/ hr. The mold halves are transferred down a conveyor system to where the shell cores are manually set (Fig. 1). Farther down the conveyor, the molds encounter an automated gluing station. Here, two robots work in tandem--one for lining a two-part epoxy glue, the other for closing the two halves together (Figs. 2 and 3). This is conducted with a visual scanning system that observes which mold is in place and transfers the information of the glue paths and closing paths to the robots.

[FIGURES 1-3 OMITTED]

From that point, the molds are carried farther down the conveyor to tip-up and centering stations, which stand the molds upright and move them in position for a refractory wash procedure (Fig. 4). This wash ensures that there are no air pockets in the mold and a better air-displacement process during casting.

[FIGURE 4 OMITTED]

After the wash coating, two pick-and-place robots pick one mold from the conveyor and place it on another conveyor, which carries the molds into a drying oven. Once the molds are dried, a transfer car takes them to an elevator that brings it up to the casting machines. When taken off the elevator, the molds are quarantined until they are lifted by one of the two casting machines that also work in tandem (Fig. 5).

[FIGURES 5 OMITTED]

As one machine casts a mold, another holds the next mold until the preceding casting is complete.

These casting machines lower the molds into one of two 7,000-lb. induction furnaces, where the molten steel will enter the molds through several hundred pingates at the bottom. The machines concurrently have one vacuum pump each, which draws the molten metal upward from the furnace into the mold (Fig. 6).

[FIGURES 6 OMITTED]

After the molds are cast, they are placed back on the elevator and another conveyor system brings them through the cooling carousel. From there, the molds are sent to shakeout and then to a plasma robotic cutting station, which removes excess material on the casting. The components are sent to a hand grinding station and then to an inline shot blast machine. The final stage is an AECCo-designed leak test that immerses the castings in an underwater bath to examine for porosity defects. The castings then undergo final inspection and are packed and shipped. The entire system, with the exception of the cooling carousel, coldbox molder (both installed in 1992) and plasma cutting station (installed in 2000), were part of the 1998 renovation.

Prior to 1998, only one casting machine was installed, which bottlenecked production. Thus, in order to meet GM's high-production demands, AECCo needed two machines operating during each run.

Ten employees work the current line from coremaking to casting--three on the molding line, three coremakers, three on the furnace deck (one taking the temperature of the baths and the other two working the furnaces) and the supervisor. Twenty more employees are involved on the cleaning and testing side of production.

"Everything can be done in a 45-50 min. cycle if things are moving accordingly," said Gomez. "We can get up to 400 cycles/day."

With this potential for 400 cycles per 8-hr. shift, AECCo can produce 800 CGC molds per clay. The company normally does not take one-shot orders for CGC, but will make prototypes for a customer. This is because it also views the operation as a problem-solving process, which assists customers in search of a casting process for intricate, high-intensity applications, such as turbo-charged engines.

"The CGC process is the best place our customers can look when their requirement is for a light-weight, thin-wall or dual-wall stainless steel casting," said Art Huge, manager of sales and marketing. "This is why we look for high temperature and high corrosion. Those needs best serve what we can do."

For a new contract to utilize the CGC process and be price-competitive, a customer likely would have to submit an order of at least 1,000 pieces, depending on the component design. Prototype casting quantities are much lower than the manifolds, but the more complicated a part is, the more cycles it will run. AECCo is looking toward current and potential customers to market the CGC process including the military, construction, marine, railroad and mining industries. "However, we are not moving away from the the transportation industry," Huge said.

Counter Adjustments

GM's interest in CGC played to AECCo's advantage in the 1998 renovation because AECCo did not have to sell this process to its new customer. GM's engineering team had been examining the benefits of counter gravity filling and sought a casting company that could tackle CGC the way they wanted. "(GM) was very familiar with (CGC) to begin with, so we didn't have that burden of trying to prove to them that it's a functional process," said Bob Stanford, general manager.

However, adapting the process to the facility has not always come that easy.

"There have been a lot of challenges with that system," said Stanford. "It's very sophisticated mechanically because it's not conducted in the traditional casting way. Sometimes you have to forget what you think you know about how to make a casting. A lot depends on the profile of the product because you are drawing the metal up from underneath the mold instead of on top of it."

A rapid molten metal filling procedure is essential in CGC to cast sections as thin as 2 mm because slow fill rates could lead to trapped atmospheres in the component. Also, it is mandatory to have one direction of flow during casting, which is contrary to several conventional gravity pour methods that can involve multiple sprues for one mold. The unidirectional flow will prevent converging gases and streams of metal from creating defects. This was evidenced when AECCo began investigating CGC processes.

AECCo's staff sampled various fill methods, such as opposing flow lines in one mold, but trapped atmospheres, particularly gas pockets, were continuously found inside the castings. Much effort went into gating and risering evaluation, which concluded a one-directional metal flow was needed for defect-free components. "We could get (a quality casting) a number of times, but that's not good enough," Stanford said. "After a considerable amount of time, you work through the defects because like any other casting process you're talking about molten metal, so the metal has its own characteristics--mold-metal interface, gas filtration from binding elements and weather, such as heat and humidity, to play with."

In addition to the filling methods, another trial-and-error effort the company endured in the CGC development was attaining the proper mold coating before casting. Gomez said one of the most critical aspects (which could lead to high scrap levels) of the CGC process is maintenance of the refractory wash. Because a proper wash coating does not permit air to leak into the mold from the outside, the vacuum evacuates the air easily from within the cavity.

Discovering an efficient coating did not come easy for AECCo. The staff tested multiple manufactured washes on the molds, a cumbersome task, as none of the washes were effective because of their inabilities to sustain high temperatures. They turned to latex paint, which had its problems, and even plastic wrap, which they found to completely evaporate during casting.

Thanks to discussions with its sand resin supplier for the coldbox system, the company ridded itself of the coating dilemma and has used a clay and mica wash since the mid-90s.

Planning Ahead

Although the main focus has been on the CGC facility in both recent installations and as a revenue builder, AECCo does devote resources to continuous improvement for the green sand and centrifugal facilities. In fact, the CGC process has served as a blueprint to follow for the other casting operations.

Currently, AECCo, a certified Minority Business Enterprise, is shifting its two other operations from a job shop environment to a low-order quantity casting facility, which takes a more scientific approach of production. "This does not mean that different products all will be produced the same way," said Stanford. "What it means is that we use data generated from the process to control parameters, reduce defects and use the lessons learned on one product across a wide range of products (where applicable). Our intention is to make the product better, faster and at less cost."

Through this attitude shift, AECCo has planned a three-phase overhaul of the green sand facility, which produces austenitic nickel-base castings. The renovation includes replacing the manual molding lines with both manual and automatic conveyors; replacing a 6,000-lb. electric arc furnace with two 1,500-lb. induction furnaces (alloys will remain); and removing four manual jolt molding machines for two jolt-squeezers. The advantages this will give the company are more floor capacity and increased throughput rates; hence, the green sand runs, which produce 1-100 of a particular casting per day, will be less restricted due to more floor space.

Further, the centrifugal facility, which also will benefit from the new furnaces to cast the same alloys as the green sand facility, will have an automated tube-pulling system in the making to replace its manually operated tube-removal process. The centrifugal casting machines will remain.

After the revamping, the company will retain its current customers, continue marketing to new customers and continue casting prototype components. "Some of our competitors go into a variety of different markets, and we would like to enter some of their markets," Huge said.

The facility reconfigurations will not be complete for at least two years, but they follow the guidelines that the company has run with since 1940. "Even though the traditional facility has been here a long time, AECCo has always been interested at looking at new things," Stanford noted. "Our predecessors were always looking to see if there was a market-driven type process to adapt or augment.

"We hope to be similar in our approach to this. We are not going to go out and buy all new technology, but we are never going to stand still."

For More Information

"Hitchiner Manufacturing Co.--Turning the Casting World Upside Down," A.T. Spada, MODERN CASTING, July 1998, p. 39-43.

Alloy Engineering & Casting Co., Champaign, Illinois.

Year Founded: 1941.

Metals Cast: Superalloys, corrosion-resistant alloys, heat-resistant alloys, wear-resistant alloys, steels, low-alloy steels, nickel-base.

Mold Processes: Nobake, coldbox, permanent centrifugal mold, green sand.

Coremaking: Shell.

Melt Capabilities: Induction and electric arc.

Casting Processes: Counter gravity casting, centrifugal casting, gravity pour.

Size: 130,000 sq. ft.

Key Markets: Automotive. heat treat, steel mill, construction, marine, industrial, railroad, food and chemical processing.

Employees: 140.