Unique casting applications with foam patterns.

Unique Casting Applications with Foam Patterns

The FPC process offers a wide variety of casting benefits and savings when applied correctly. Here are three examples of how the process has been used successfully.

In past years, casting users, buyers and producers have viewed the Foam Pattern Casting (FPC) process as a curiosity. It was something to watch and if it proved successful for others, it may be considered.

The skeptics are now being convinced that the FPC process has a permanent and significant position in the metalcasting industry. This change in attitude has come about by proving the process in unique and innovative ways, and by finding and creating applications that have broken through the resistance-to-change barrier.

Described below are three unique applications of castings produced with FPC that are achieving significant savings through weight and cost reductions, reduced machining and increased performance. The three case studies involve a bronze casting, gray iron casting and an aluminum casting.

Bronze Pump Impeller

The first FPC application is a bronze pump impeller produced by AMPCO Metal, Milwaukee, for their proprietary line of noncorrosive pumps. Faced with difficult market conditions, AMPCO management began looking for ways to reduce costs. Their primary targets were high cleaning costs and scrap rates. In 1985, the foundry entered into a development program for this impeller and other components using FPC.

AMPCO achieved several positive benefits using FPC for their pump impeller casting. Among them were: * A 12% Increase in Pump Efficiency--This was an added benefit not initially considered when switching from green sand to FPC. The very smooth internal surfaces, added water volume available and clean edges allow this component to pump more water at a reduced energy load; * A 28% Reduction in Weight--Machine stock was reduced by two-thirds, and without the core shift previously experienced, AMPCO was able to reduce the thickness of the cast walls significantly; * A 50% Reduction in Net Completed Product Costs--The largest area for savings was achieved by eliminating 90% of the cleaning costs. A 15-20% reduction in machining costs plus reduced inspection times also contributed to the savings. These improvements, together with the savings, allowed AMPCO to cut their costs and remain competitive.

Cast Iron Spool Valve 

Another example of successfully using FPC is a gray iron hydraulic spool valve, a patented casting produced exclusively by Seisan Foundry in Kawachinagano, near Osaka, Japan. The inventor of this component tried for several years to produce it by other casting processes. Seisan Foundry, working with the inventor and Kuroso Co of Tokyo, successfully developed the casting in FPC. Dr. Takeshi Yamaguchi, a noted FPC authority in Japan, said, "No other casting method could make this casting design."

Seisan Foundry manager, Mr. Yaganisawa, confirms that the part could not be made in green sand or by shell molding. They found that the design lent itself to either the FPC process or as a completely machined fabrication which would cost much more than a FPC casting. Benefits achieved, according to Yaganisawa, include: * internal fluid passages require very little cleaning; * only 1.5 mm machine stock is required, compared with 3.0 mm in green sand; * precise repeatability of dimension is being achieved from part to part; * the cast iron hydraulic spool is now a universal design and is being used by three different manufacturers of backhoes in Japan; * FPC allowed each of the customers to reduce the number of total hydraulic valve components, significantly reducing overall costs. For proprietary reasons, exact savings were not revealed.

In this application, nine separate foam pieces are assembled to make one foam pattern. Each of the nine pieces form different fluid passages at each of eight levels.

Aluminum Exhaust Manifold 

An example of an aluminum casting produced with FPC is a water-cooled exhaust manifold produced by AMPCO Metal for Bombardier, Valcourt, Quebec. This casting was designed for the SeaDoo personal water vehicle. The manifold, as designed, could not be produced cost-effectively in green sand. After a year, Bombardier decided to try the FPC process.

Once the foam pattern tooling was completed, 12 weeks of development work was all that was needed to bring the casting to full production. It was introduced in the spring of 1989.

Following are confirmed benefits using FPC to produce this design of the water-cooled exhaust manifold. * Using FPC the casting weight was reduced from more than 12 lb per part to 8.8 lb. * Wall thicknesses were reduced from 6 mm in green sand to 4 mm with FPC. * Producing the part in green sand would have required that it be a two-piece weldment. With FPC it was cast in a single piece. * Clearance holes in the flange were able to be cast-in using FPC. * Overall cost reduction for the design in FPC versus green sand was in excess of 40%, though Bombardier did not provide exact cost figures.

Choosing FPC

The castings illustrated here, along with many others, are being successfully produced using the Foam Pattern Casting process. And while it may be tempting for casting designers, buyers and producers to assume that FPC can be applied to all cast products, caution should be used in selecting parts for production with the process.

A working knowledge and understanding of FPC is absolutely necessary in order to achieve the maximum benefits from foam patterns. With the expertise available today from the experience with FPC gained during the last several years, it is now much easier to determine which castings can be successfully produced using the process.

In considering a component that may be a candidate for production with the FPC process, benefits to look for include: reduced machining and overall weight, higher performance, multiple components cast as a single piece, tighter tolerances and uniform wall thicknesses. Any or all of these are possible with FPC and may contribute to reducing overall product cost.

The future looks bright for the Foam Pattern Casting process, but we must take care to use it wisely.

PHOTO : Produced in FPC by AMPCO Metal, the close up and cutaway views of a bronze pump impeller

PHOTO : casting show the excellent surface finish. In addition, the part now weighs 28% less than

PHOTO : it did when cast in green sand, and the company is experiencing a 50% reduction in net

PHOTO : completed costs.

PHOTO : Nine separate foam pieces are assembled to make the final pattern for a cast iron

PHOTO : hydraulic spool valve as shown in the photo at left. Righthand photo shows the finished

PHOTO : foam pattern along with the finished iron part.

PHOTO : A cast aluminum water-cooled exhaust being produced for a Canadian firm requires a four

PHOTO : pattern (left). These are assembled and produced with the FPC process. Final pattern and

PHOTO : aluminum casting are shown in the right-hand photo.