METAL CASTING APPLICATIONS IN JAPAN

As in Germany, the use of CAD solid modeling in Japan is limited. 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 10.3 summarizes some of the rapid prototyping systems in use in Japan.

Table 10.3
Japanese Rapid Prototyping Manufacturers' Applications for Metal Casting

INCS, Inc., is the largest service bureau in Japan. It uses 3D Systems stereolithography machines to build QuickCast patterns for investment casting. This accounts for approximately 15% of its work. INCS engineering staff and technicians are very knowledgeable about RP, and the parts that they displayed to the panel are of excellent quality. The company has worked with investment casting foundries to cast the CibaTool 5180 epoxy QuickCast patterns. According to INCS' staff, there are five foundries in Japan capable of casting RP patterns. They also stated that investment casting in Japan is a $600 million industry.

Nakamura Pattern Company is a small pattern making company that has 20-25 employees. As a traditional sand casting pattern builder, most of its employees are skilled pattern makers. However, this group of skilled pattern makers is advancing in age (the average age is 50 years), and the company is having trouble attracting replacement workers to be trained as skilled pattern makers. As a result, Nakamura Pattern Company owners decided to investigate RP as a limited alternative to traditional hands-on pattern making. They visited the United States and attended the SME/RPA Rapid Prototyping and Manufacturing Conference and Exposition in Dearborn, then toured several U.S. companies, including Helisys. After thorough investigation of several rapid prototyping processes, Nakamura chose to purchase a Helisys LOM machine.

Nakamura has integrated the LOM machine into its manufacturing base, using it for fabricating complex patterns for sand casting. It is run on a 24-hour basis. Right next to it is a CNC (computer numerical control) wood-milling machine. Depending on accuracy requirements, the company chooses between CNC machining and the LOM machine for pattern fabrication. CNC is used for greater precision, but the LOM machine is easier to use. Company representatives estimate that using the LOM machine has increased business by 50% (Sites, 1996, 92-94).

One of Nakamura's advantages in using rapid prototyping to fabricate sand patterns is that it is actively using CAD solid modeling. The company uses several types of CAD solid modeling software, and its staff is well trained. This company has been very progressive in its use of new technology (RP and CNC); at the time of the JTEC visit, its management intended to look into purchasing another LOM machine within the next year or so.

Toyota Motor Corporation is in the process of evaluating rapid prototyping for metal casting. It has done some benchmarking with selective laser sintering and stereolithography as well as LOM, and it is just now looking at metal casting applications. Preliminary results of Toyota's benchmarking indicate that there are limitations to each of the RP processes it is investigating. It, too, is comparing CNC machining to rapid prototyping.

Hino Motors, Ltd. is a user of 3D Systems stereolithography apparatus (SLA-500). It is currently in the process of upgrading its machine to build investment casting patterns using QuickCast software and CibaTool 5180 epoxy resin. Its engineers also see potential in the use of solid stereolithography patterns for sand casting applications. Evaluation of this application is underway.

Tokuda Industries uses the Kira Solid Modeler to make paper patterns for sand casting. Tokuda representatives stated to JTEC/WTEC panelists that there were some drawbacks to this process, in that it requires attended operation, and the accuracy and surface quality are less than desirable. They also stated that although the Kira process is less expensive, it is slower than CNC milling.

Research and Development

As previously stated, research and development for metal casting applications in Japan is primarily focused on materials and software development for pattern fabrication. There has been some R&D done by Professor Nakagawa in the area of casting and computer simulation. This work is documented in a paper "Applications of Laser Stereolithography to Casting and Computer Simulation" (Nakagawa et al. n.d.).

Conclusion

In Japan, CAD solid modeling is not widely used. In many cases, part designs have to be translated into solid models before fabrication by a rapid prototyping machine. This increases the cost of RP parts. Rapid prototyping is compared to (and competes against) CNC machining with respect to cost, scheduling, and quality. Insufficient accuracy and surface quality of parts fabricated using RP processes are limiting their use in Japan. Small progressive companies like Nakamura Pattern Company and INCS are aggressively and successfully using rapid prototyping for metal casting applications.

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Published: March 1997; WTEC Hyper-Librarian