Ampco Metal, Inc.; marketing the benefits of copper-base EPC.

Ampco Metal, Inc

Marketing the Benefits of Copper-Base EPC 

For Ampco Metal, a long-time producer of copper-base castings, the future of its foundry operations lies in the Evaporative Pattern Casting process.

A unique and successful application of the Evaporative Pattern Casting process (EPC) began in 1982 at Ampco Metal, Inc. The company, a 75 year old Milwaukee-based pioneer of cast aluminum bronzes, nickel-aluminum bronzes and other high-copper casting alloys, entered into a R&D project during that year to investigate EPC's potential.

Metallurgists and engineers spent five years developing the process for its family of cast bronze and aluminum alloys. A production facility was installed in 1987 and production began in 1988.

The first production run, consisting of 10,000 aluminum exhaust pipes for a manufacturer of personal watercrafts, began in 1988 and proved so successful that Ampco Metals has decided to base the future of its foundry operations in the EPC process.

Following a buyout of the company by a management team earlier this year, existing sand molding and centrifugal casting lines were shut down. Though the company retains its Garland, TX sand foundry, Kimball J. Norman, president, firmly believes that EPC offers the greatest potential for growth in the company's foundry business.

"EPC is an exciting development in our industry," Norman says, "one that has tremendous advantages over conventional casting methods."

EPC Production

Ampco Metal's EPC installation consists of a vertical sand conditioning and compaction system that automatically controls sand flow and the compaction cycle. Shown in Fig. 1, the system provides uniform precision in casting and an environmentally clean operation.

An elevator lifts sand from the shakeout to the top of the 20 ft high structure and discharges into a vibrating sand screener/classifier. Desired grain size distribution (for best permeability) is developed and fines and tramp materials are removed. The clean sand then moves through a hopper and into a vibrating sand cooler.

A sand flow and distribution unit then rains the cooled sand into the flask. During the filling process, the flask, which is supported by a three pedestal compaction table, is vibrated. Compaction is a critical operation and is closely controlled. Overcompaction can result in pattern distortion, while undercompaction can produce expansion defects. Thus, the rate of sand fill and the compaction cycle are automatically controlled and optimum values are recorded for repeatability.

Quality control efforts begin with pattern inspection, as shown on the cover of this issue. All patterns are inspected for dimensional accuracy, surface finish, pattern defects and pattern density. Refractory coatings are controlled, as well. Coating baume is monitored for consistency and coated patterns are inspected and weighed to ensure completeness and consistency of coating. A completed cluster, consisting of pattern, gates, risers and pouring cup is shown if Fig. 2.

After pouring, removing the castings from the flask is no different than for sand castings. Figure 3 depicts shakeout. The major difference between these castings and sand castings will be found in the cleaning room and machine shop.

The absence of flash, sand and resin reduces cleaning. The as-cast surface finish is typically 200-350 and this can be improved with polishing. In the machine shop, reduced stock allowances result in reduction or elimination of rough machining. The ability to provide ascast holes, flanges, grooves, etc, also means less machining. And the better finish and absence of inclusions means better tool life.

Applications

Ampco Metal's foundry unit traditionally has supplied military and industrial markets. But the success of the watercraft exhaust pipe shows that the company has the potential to become a high production producer of low cost, near net shape castings for consumer-driven markets.

The key to succeeding with a new casting process in new markets is to market the benefits of the process. Says Rob Pearson, sales manager, "EPC castings are consistently poured at closer tolerances with less stock for grinding and finishing. Dimensional variability associated with core setting, mating of cope and drag are eliminated."

But Pearson describes further advantages that EPC has over sand casting for copper-base casting alloys, notably greater design flexibility, allowing thinner walls and intricate coring; and alloy flexibility. These advantages, says Pearson, have been applied to pump impellers and pump cases used in the company's proprietary centrifugal pump line.

"Historically," says Pearson, "the aluminum bronzes and nickel-aluminum bronzes were avoided in thin-wall complex castings because of their narrow freezing range, which required special foundry techniques. By comparison, a standard tin bronze is much more fluid and its wide freezing range assures ease of casting with any standard foundry technique.

"With the EPC process," he continues, "Ampco Metal can produce pump impellers, cases and other parts with the high-alloy coppers and aluminum bronzes, which offer greater corrosion resistance, at competitive prices.

"Also," says Pearson, "in the case of impellers, shown in Fig. 4, the EPC process actually improves the product's performance over a sand cast impeller." The elimination of core prints and flash, along with little or no draft, produces cleaner and wider internal passages, he explains. A less turbulent, cleaner flow of liquid through the passages is the result. This benefit has been found to increase the hydraulic efficiency of EPC cast impellers by 5-6% over similar sand cast impellers.

A water softener valve body casting, shown in Fig. 5, illustrates the design flexibility of the process. The part has thin walls, intricate coring with clean passages and was converted from a fabrication of several components into a one-piece casting.

In Fig. 6, a near net shape water meter housing casting is shown next to its pattern. This casting requires no additional processing on the flanges and the bolt circle and holes are utilized ascast. The only machining operations are the top surface, the drain holes and meter supports inside the casting. This casting was reduced in weight by over ten lb because of the reduced section thickness.

As these examples show, Ampco Metal has found EPC to be a competitive process that allows the company to produce economical high-alloy copperbase components with improved properties, a great benefit to its customers.

[Fig. 1-6 Omitted]

Paul M. Bralower/Associate Editor