Site:               Buhler Ltd.
                    CG-9240 Uzwill
                    Switzerland

Date Visited:       April 3, 1996

WTEC Attendees: D. Apelian (report author), M.C. Flemings, P.H. Mikkola

Hosts: Stefan Fritsche Andre Notter Ruedi Beck Sebastian Hirschberg Leo Iten

BACKGROUND

Buhler is a worldwide engineering group active in the design and construction of plants and equipment with headquarters in Switzerland. It has vast technological expertise and engineering know-how in plant engineering, with capabilities covering key technologies for major production processes including food as well as metal -- ranging from chocolate manufacture to die casting. Buhler was established in 1860, and the company has been owned by the Buhler family since its inception. It started out as an iron foundry and soon shifted its main activity to the design and construction of flour mills. Today, Buhler supplies systems and plant equipment for a variety of industries including pasta manufacture, grain milling, animal feed, waste processing, bulk handling, and high pressure die casting. It can be seen that Buhler has a presence in a variety of process technologies.

The Buhler group has 6,000-7,000 employees worldwide. Annual sales are on the order of 1.2 billion Swiss Francs. The food industry makes up about 70% of sales, die casting about 12% (including the die casting foundry in Winken), and non-food businesses provide the rest.

RESEARCH AND TECHNOLOGY

The WTEC team visited the headquarters in Uzwil and, in particular, visited the group responsible for the die casting sector. Buhler is a well-known die casting equipment manufacturer. It has a long tradition and a strong reputation in high quality equipment. Buhler has several strengths and assets:

Figure 4.1 from Buhler portrays gate velocity as a function of casting pressure, wherein various die casting technologies are displayed. Specifically, one can see gravity die casting and low pressure die casting at the bottom left hand corner at lower gate velocities and lower gate casting pressures whereas squeeze casting and semisolid casting (SSM) require higher casting pressures but not significantly higher gate velocities. Buhler has a very good understanding and a corporate philosophy of having a holistic view of the industry, providing equipment to the industry that enables flexibility in the application of gate velocity and casting pressure. In other words, Buhler equipment removes many of the constraints on the user in that a variety of technologies can be applied.

Buhler's "SC" series of machines sets it apart from the rest of the die casting equipment manufacturers. The SC machines feature real-time, closed-loop control systems that reflect many years of Buhler experience. Through this technology, Buhler enables the die caster to successfully heighten the level of quality with the use of properly located valves on the discharge side of the cylinders, in conjunction with control of the injection curves. The process can thus be adapted to match the part to be cast according to the exact setup requirements. In 1989 at the Gifa Show, Buhler introduced the first real-time, closed-loop controlled machine. In 1996, Buhler introduced a second generation of SC machines incorporating real-time closed-loop controls.

The SC series includes three different models: SCD, SCF, and SCN (Fig. Buhler.1). The SCD has a small-shot cylinder for high dynamics, and the machine operates at high-shot velocities. It provides pressure intensity for high final compression, and it is suitable for a wide range of components requiring high integrity die casting. The SCF (F standing for flexible) uses a large shot cylinder for high filling forces. This machine is suitable for flexible applications up to and including squeeze and SSM casting, especially for parts with special requirements. SCN (N stands for Newtech) has a large shot cylinder for high filling forces and a pressure intensifier for high final compression. This machine is aimed at the most exacting new applications of semisolid metal casting and squeeze casting.

Moreover, upgrading of SCF to SCN is possible because of the modular design of the Buhler machines. The pressure intensifier can be retrofitted depending on the need. The flexibility provided by SC technology can be seen in Table Buhler.1 where SC characteristics and casting technologies are outlined. For example, the table shows applications of SC technology in squeeze casting as well as for thin, large area castings. The details of the SC series and the range of locking forces, as well as the velocity curves, are shown in Figures Buhler.2, Buhler.3, and Buhler.4. At the shot end the distribution of the velocity in the shot sleeve can be seen for SCD as well as SCF. It is quite apparent that the Buhler machines provide a tremendous amount of flexibility and operational maneuverability for the die caster, up to and including high integrity castings.

Table Buhler.1
SC Technology

[Table]

[Figure]
Fig. Buhler.1. SC technologies.

[Figure]
Fig. Buhler.2. Details of the SC series (SCD).

[Figure]
Fig. Buhler.3. Details of the SC series (SCF).

[Figure]
Fig. Buhler.4. Details of the SC series (machine concept).

The WTEC team members spent quite a bit of time discussing die design with the Buhler hosts. They have much expertise in the intricacies of die design. The WTEC team then visited their pilot plant where squeeze casting as well as semisolid casting of aluminum was taking place and semisolid processing was demonstrated. The manufacture of automotive components via SSM was in pilot production. All in all it was a most impressive operation.

It is clear that Buhler has a lead position in the die casting industry because of its ability to provide modular design, process control, real-time closed loop control, and insight into the casting technologies of the future.


Published: March 1997; WTEC Hyper-Librarian