Site:               Ryobi Shizuoka Plant
                    5215-1 Kanbara-cho, Ihara-gun
                    Shizuoka-ken 421-32, Japan
Date Visited:       January 9, 1996

WTEC Attendees:     D. Apelian (report author), D. Bertram, G. Holdridge

Hosts:              Shizuoka Plant
                    Shoji Osawa, Plant Manager, Die Casting Division
                    Tatsuyoshi Mochizuki, Manager Die Casting, 
                      Die Casting Division

                    R&D Division
                    5-2-8 Toshima, Kita-ku
                    Tokyo 114, Japan

                    Tsutomu Kakuma, General Manager, R&D Division, 
                      Die Casting Division
                    Tsutomu Mori, Adviser, R&D Division, 
                      Die Casting Division
                    Naomi Nishi, Manager, R&D Division, 
                      Die Casting Division
                    Hiroyuki Omura, Group Leader, R&D Division, 
                      Die Casting Division


The Ryobi Group is a conglomerate of 40 companies which forms the backbone of Ryobi Ltd. Ryobi Ltd. is built upon advanced technological capabilities, innovative product development, and progressive marketing. It also has plants at Hiroshima, Mirasaka, Mitsugi, Saitama, Hyogo, Shelbyville, Indiana, in the United States and Co. Antrin in the United Kingdom. Much of the R&D takes place at the Hiroshima plant and the Tokyo R&D office with some limited R&D at the other plants.

The Shizuoka operation began in 1962 and is intensely invested in die casting. In 1984, a joint venture with Ford Motor Co. was formed with the goal of producing transmission cases. Four 3,500 ton machines were used for this. Production for Ford is now being done in the United States in a 100% Ryobi-owned plant. The 3500-ton machines at Shizuoka have been diverted to domestic products.

The Hiroshima plant produces 2,100 metric tons of aluminum per year. The Shizuoka plant produces 2,600 metric tons of aluminum, and the Mirasaka plant produces 2,400 tons of aluminum per year. The Mitsugi plant produces 190 tons of aluminum and 80 tons of zinc. Plastic injection throughout all of the Ryobi die casting plants is about 200 metric tons per year. Overall, Ryobi produces 7,290 metric tons of aluminum, 80 tons of zinc, and 200 tons of plastic each year.

The Shizuoka plant has 35 die casting machines with the following breakdown -- four 3,500-ton, one 3,300-ton, one 2,250-ton, five 1,650-ton, one 1,250-ton, two 1,200-ton, one 1,000- ton, ten 800-ton, two 650-ton, seven 500-ton, and one 350-ton machines. Of the products made by the Ryobi die casting operations, 72.3% of die castings are used in four-wheel automotive applications and 8% in two-wheel (motorcycle) applications. Clearly a majority of these products go into the transportation sector. At the Shizuoka plant, 70.7% of the output is for the four-wheel automotive industry, while 16.9% goes into two-wheel applications. In other words, nearly 88% of all the Shizuoka plant's products are used in the automotive industry.

Regarding the dies that are manufactured, 10% of all of Ryobi's dies are made at the Shizuoka plant. The remaining dies (90%) are manufactured at the Hiroshima plant.

The Shizuoka plant employs 327 people -- 40 engineers, 200 factory workers, 8 managers, and 79 clerical workers.

During the plant tour the WTEC team saw die manufacturing and die refinishing shops, the metal melting operation, die casting machines, inspection, and shipping. The operations in that organization were impressive, particularly the cleanliness of the plants. It is most inspiring to see a die casting operation that looks so organized and so clean. The manufacturing infrastructure is very strong.


Most of the composites that are die cast are being used for wear applications, but the cost of production, particularly machinability as well as the recycling and raw material costs (e.g., carbon fiber), are major barriers. Composites also have interesting and appropriate uses in applications where creep strength and heat resistant concerns are critical. Ryobi managers believe that cylinder liners will be specified to be produced from composite materials by automotive engineers of the future. Brake components are another possible application. They have developed the RX1000 composite metal matrix material for die casting operations (see Table 3.1, p. 22).

They foresee little change in the alloy chemistry field. Ryobi's W2 alloy, which has higher strength and ductility than the conventional alloy (i.e., 380), seems to be well received.

Ryobi representatives expressed the view that squeeze casting may be better than conventional die casting for higher performance components. However, the squeeze casting process is more expensive. At present, wheels, cross members, and certain components for high performance cars like the Mazda RX7 are being produced by squeeze casting. There are no specific weight reduction goals in Japan (such as CAFE in the United States), and thus WTEC's Ryobi hosts could not comment on targets for weight reduction. They indicated that many of their customers are no longer as willing to pay for reduced weight as they were a few years ago. Ryobi has not embraced squeeze casting as a whole; however, a Ryobi-associated company (Tokyo Light Alloy) has two 1600-ton squeeze casting machines made by Toshiba. These are medium-pressure casting machines. In addition, there is a smaller squeeze casting machine at the Mitsugi plant.

Ryobi is not pursuing semisolid materials processing technology in an aggressive way; however, Ryobi engineers are studying it. When asked whether the automotive sector is pushing to use semisolid processing, they said no, citing cost as a barrier.

At Ryobi's Shizuoka plant, the molten metal is neither degassed nor filtered, however the sleeve-filling decanter did have a fiberglass fishnet filter, which mitigated the surface dross getting into the shot sleeve. Ryobi does not do grain refinement nor does it modify the melt prior to casting. Phosphorous is added to aluminum 390 alloys.

Ryobi is beginning to employ on-line control and intelligent processing within the plant. Plant managers are monitoring speed and all the details of the process and computerizing these data. These are used to monitor defects. The temperature of the die is also being monitored. When using a slow shot speed which produces a more laminar flow, they find that the castings thereafter are easier to heat treat and are free of holes and defects. An expert system (ES) was in use to monitor die temperatures for the Ford transmission case line. However, the ES system is not in use at the new U.S. plant.

The WTEC team viewed a video in which RIC cores were shown being used in the operations. (RIC cores are sand cores that have a special resin coating, which prevents the liquid metal from impregnating into the core.) RNC is Ryobi's version of squeeze casting. Computer-aided Engineering (CAE) is being used throughout Ryobi. The company also is utilizing the SOLDIA modeling software developed by Komatsu to simulate solidification as well as to predict shrinkage formation.

Twenty percent (by weight) of all of Ryobi's aluminum die casting products were being exported to Ford Motor Co at the time of the WTEC visit.

Ryobi employees receive extensive training and education. When new people are hired, they are assigned to all of the sections of the plant for one month. During the next two months, they are trained in the particular section they are assigned to. Once they are established in the plant, they participate in a continuous learning program.

Environmental issues are certainly of concern. Oil mist is definitely an issue; however, it was pointed out that noise is a greater environmental issue than oil mist.

Published: March 1997; WTEC Hyper-Librarian