FOUNDRY TECHNOLOGY OBSERVED

Daido Precision Parts

Two of the foundries visited merit special attention. The first is the Daido Precision Parts (DPP) plant in Nakatsugawa, one hour northeast of Nagoya. This plant is four years old and is, without question, the most highly automated investment casting plant in the world. It cost ¥4.5 billion ($43 million). The plant was built as part of a local government plan to create jobs for the local economy to retain young people in the area. It employs 100 people (80 hourly and 20 engineering and supervisory), and the average age of plant employees is 25 years. The plant occupies 8,000 m2 in the Daido complex in an industrial park. The plant is built on two floors: wax injection, assembly, finishing, and inspection are on the second floor while shelling, dewax, and pouring are on the first floor.

The plant produces 40,000 automotive turbocharger wheels each month, as well as printer balls and industrial castings. Most castings are small (less than 1/2 pound) and are cast in stainless steel and heat resisting alloys. A typical part is shown in Fig. 7.5.

The wax room, shown in Fig. 7.5, is almost completely automated. Patterns are injected, lifted from the wax die by a robot, and held while the gate is heated. Meanwhile another robot heats a section of the downpole, and the first robot places the pattern on the tree. This operation is carried out at the injection press: there is no separate assembly area. Finished assembled trees are placed on a conveyor that carries them down to the first floor and the shelling operation. Dies are delivered to wax presses using automatic guided vehicles. Most of the presses and assembly stations operate unattended. Operators are used only on those parts that are difficult to produce and during the period when injection procedures are being established.


Fig. 7.5. Dip line at Daido Precision Parts (left), wax room (upper right), and a typical part (lower right).

Shelling is done on two automated dip lines, shown in Fig. 7.5. The binder is colloidal silicate, and three hours are allotted for drying between dips. A total of 72 hours is required to produce the mold.

The plant has an exclusive license for the CLA/CLV process in Japan. This operation is also highly automated, with elaborate controls and display screens that show the status of the mold fill operation. Finishing and inspection are similar to American methods.

Although the plant is highly automated, DPP does not use solidification simulation to gate and riser its castings, because, in the opinion of WTEC's hosts, there are no simulation programs today that accurately predict metal flow in the thin sections of their turbocharger wheels. They also do not use rapid prototyping because the resins available in the past could not replicate the thin sections of the turbocharger wheels. (It should be noted that there was very little use of solidification modeling or of rapid prototyping in Japan in any of the foundries visited.) Only 10% of its turbocharger dimensional data is received by DPP in digitized form.

No control charts were visible (in fact, we saw no control charts in any of the foundries visited). However, scrap data was scrupulously recorded and entered into a computerized database for engineering analysis.

Yamagata Seimitsu Chuzo

This foundry was built by CADIC Corp. to demonstrate its casting technology and train licensees of the CADIC process. Today it is the fifteenth largest investment foundry in Japan. Based on technology originally developed in East Germany, the CADIC process and has been refined in Japan with additional patents. The object of the process is to lower the cost of investment casting to the point where it becomes economically attractive to the automotive industry. It has been licensed to 10 Japanese foundries and some overseas foundries, but not all of the licenses are still in effect (the process was initially offered for license in the mid-1980s). There are a number of innovations that make the process interesting. The plant employs 60 people; its product is primarily industrial poured-in stainless steel. It is located in Nagai, on northern Honshu island.

As at the Daido plant, clusters are assembled at the wax press, using press operators as assemblers. The dip line features an ingenious automation design, which does not rely on computer controls or robots, shown in Fig. 7.6. Continuous throughput is emphasized wherever possible.


Fig. 7.6. Dip line at Yamagata Seimitsu Chuzo.

A feature of the CADIC process is the use of sharply notched in-gates on its castings, as shown in Fig. 7.7. These in-gates fracture during the ceramic knock-off operation, and the castings drop to the bottom of the knock-out booth. No cutoff is necessary. Sound castings are produced by the use of strong radial thermal gradients, brought about by air or water spray on the castings after they are poured.


Fig. 7.7. Cluster design at Yamagata Seimitsu Chuzo.

The CADIC process was developed with the specific intent of targeting the automotive industry. A great deal of thought was given to the type of parts that would be needed by this industry and what the cost barriers were to making them. This approach to strategically planning the process development was very impressive.

Nippon Precision Casting Company

The foundry WTEC visited (there are two locations) was similar to most American investment foundries and was not considered to offer any new technologies. However, Nippon Precision Casting is the only foundry -- of any type -- in Japan currently constructing a new plant. One of the older plants will be closed when the new one is opened.


Published: March 1997; WTEC Hyper-Librarian