Industrial Casting Applications

Castings can range in size from a few grams (for example, watch case) to several tones (marine diesel engines), shape complexity from simple (manhole cover) to intricate (6-cylinder engine block) and order size one-off (paper mill crusher) to mass production (automobile pistons).

The desired dimensional accuracy and surface finish can be achieved by the choice of process and its control. Castings enable many pieces to be combined into a single part, eliminating assembly and inventory and reducing costs by 50% or more compared to machined parts. Unlike plastics, castings can be efficiently and completely recycled.

Today, castings are used in virtually all walks of life. The following is a partial list of applications, with transport sector and heavy equipment taking up over 50% of castings produced:

• Transport: automobile, aerospace, railways and shipping
• Heavy equipment: construction, farming and mining
• Machine tools: machining, casting, plastics moulding, forging, extrusion and forming
• Plant machinery: chemical, petroleum, paper, sugar, textile, steel and thermal plants
• Defense: vehicles, artillery, munitions, storage and supporting equipment
• Electrical machines: motors, generators, pumps and compressors
• Municipal castings: pipes, joints, valves and fittings
• Household: appliances, kitchen and gardening equipment, furniture and fittings
• Art objects: sculptures, idols, furniture, lamp stands and decorative items.

Figure 1: Metal Casting

Virtually any metal or alloy that can be melted can be cast. The most common ferrous metals include grey iron, ductile iron, malleable iron and steel. Alloys of iron and steel are used for high performance applications, such as temperature, wear and corrosion resistance. Table 1 lists the major metals in use today (by weight) along with their main characteristics and typical applications.

Metal Casting Applications in the United States

The United States are the world leader in the use of rapid prototyping processes (RP) for metal casting applications. Metal casting from RP patterns is widely used by government and industry, cross-cutting numerous markets, including those for automotive, aerospace, medical, and consumer products. The use of RP patterns for investment casting continues to increase as processes evolve and pattern quality improves.

There is already a significant number of U.S. companies applying RP to metal casting, as Table 2 shows. 3D Systems' stereolithography (SL) process is often used to fabricate patterns for investment casting. The QuickCast build style, coupled with CibaTool and other epoxy resins, is now used by many U.S. companies to fabricate complex patterns quickly for investment casting of metal parts.

Metal Casting Applications in Europe

In Europe the use of RP for investment casting is limited but increasing. As the use of Computer-Aided Design (CAD) solid modeling increases, the application of rapid prototyping for manufacturing metal investment castings will also increase. Table 3 summarizes some German-manufactured rapid prototyping systems.

Dassault Aviation (France) is a frequent user of RP patterns for investment casting. In the same manner as many U.S. companies, Dassault designs and manufactures complex metal castings using 3D Systems' QuickCast build style to fabricate patterns. Dassault engineers have worked with several foundries to develop process parameters for successfully casting RP patterns. Dassault has certified RP castings for use in testing prototype flight hardware. In addition, some German companies use the expertise of Dassault to get metal castings from RP patterns.

The European automotive industry has also had success using RP castings. Typically, a company sends a CAD solid model of the design to the United States for pattern fabrication, a U.S. foundry does the casting, and the part is delivered back to the company.

Metal Casting Applications in Japan

As in Germany, the use of CAD solid modeling in Japan is lower than in the US. Again, as the enabling technology for rapid prototyping machines, a CAD solid model must be created before a part can be fabricated.

The use of two-dimensional CAD is very common in Japan. Often a 2D CAD file is translated to a 3D CAD solid model, then fabricated on an RP machine, but the extra step of creating the solid model increases the cost of the RP part.

In Japan, rapid prototyping competes with machining for producing prototype parts. In many cases, even complex geometries can be machined as fast as parts can be fabricated using RP. There are hundreds of small machine shops in Japan, and the competition for work makes machining an attractive alternative to RP. Another reason RP competes with machining is the lower accuracy and surface roughness limitations of RP parts.

As the use of CAD solid modeling increases, the use and application of RP is expected to increase. This was evident by the use and application of RP in some of the small progressive companies that the JTEC/WTEC panel visited. Table 4 summarizes some of the RP systems in use in Japan.