Carat – a success story

26.11.2008 How has the market accepted the new Carat two-platen die casting machine? Beat Müller carefully observed the market launch. The result: The Buhler two-platen technology has met with wide acceptance. New equipment, new production installations, new organizations – this often gives rise to a certain amount of caution in the marketplace, to the point of open rejection. We are all the more pleased to report about the exact opposite, where initial skepticism and reserve vanished within a matter of a few hours. That is how we experienced the start-up of the first Carat die casting machine at the TCG Unitech company in Kirchdorf an der Krems in Austria at the end of March 2007. Of course, we must admit that we did not receive such a response to all the machines we have supplied to date. But after a certain “induction time,” all the operators of the Carat are highly satisfied with their new die casting systems. In the field of die casting, “satisfied” means nothing else than the fact that the machine fulfills all customer expectations and objectives: a maximum number of accept components per time unit at minimum cost. Among other things, these goals are achieved by reducing cycle times, producing components of a more consistent quality, and slashing costs during production changes. Beside these factors, higher capacity utilization rates and a lower space requirement of the new manufacturing cell also have a positive impact on cost-cutting.

Higher production process stability
Apart from the efforts we have always made to reduce the cycle time, the new Carat product line offers additional technical design features supporting this endeavor. Under similar operating conditions, production runs with the new Carat compared very favourably with those on a conventional toggle-joint die casting machine using a given die. The new two-platen technology applied in the Carat tends to reduce flash and thus improves the stability of the casting process. This goes to show that both the rigidness of the die closing system and the distribution of the locking forces have been substantially improved. The system better offsets die parallelism errors, which increases the die life expectancy and reduces the need for remachining the die cast components.

Reliable production changes and shorter secondary process times
During production changes, things usually become hectic in a die casting foundry. High die temperatures and die release agent deposits contribute to this commotion. A good machine design gives consideration to this fact. The design of the Carat is such that no tie bars will project into the die zone during production changes. Dies can be hoisted into the die area without restrictions; there is no danger of the moving die colliding either with projecting tie bars or any existing protective pipes and causing damage. In addition, the locking grooves and threads of the tie bars are always completely guarded and sealed off by the platens during production. This prevents contamination of the grooves and threads by die release agent and flash. In the manufacture of flat components, the enlarged die opening stroke allows the spray robot to spray the fixed die half without any risk of colliding with the extraction robot withdrawing the component. This improves the cycle time by several seconds.

Lower space requirement
When a foundry replaces an old 900-ton machine, the existing space can be easily filled with a new Carat machine with a locking force of at least 10,500 kN, usually even 14,000 kN, and this applies also to larger units. This offers the advantage of allowing larger components to be cast on a given surface area or, say, to switch from a single-cavity die to a doublecavity die.

Popular Carat shift
These benefits have been confirmed in the field. TCG Unitech in Kirchdorf works 16 weekly shifts. Capacity utilization of the system is well above 80 percent. Production manager Michael Thieser explains that most downtimes are caused by die changes, die problems, and operating trouble of the peripheral equipment. Only in rare cases are downtimes attributable to the die casting machine. It is therefore not surprising that the “new Buhler” is highly popular with the operating personnel, who are highly pleased when they are assigned to the Carat shift.

Left: Mr Friedrich Wegerer holding a support for steering rod <br />
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Right: Mr Markus Hintermüller holding a bed plate part Left: Mr Friedrich Wegerer holding a support for steering rod

Right: Mr Markus Hintermüller holding a bed plate part