Car panels today are mostly made by deep drawing in press tools. Recently, however, this method has begun to reach its limits due to wear caused by the use of high-strength steels.
The conventional steel grades used in many of the metal parts are now being replaced by high-strength steel because high-strength steel enables auto manufacturers to produce components that are thinner and lighter without losing any of their stability - and this weight saving delivers improvements in fuel consumption.
However, using high-strength steel complicates the forming process. Due to the heavy mechanical load, the press tool wears more quickly than with conventional sheet metals. This is a high price to pay, because the tools have to be manufactured with extreme precision - and at great expense.
A possible alternative is to replace the tooling steel with high-performance ceramics in areas that are subjected to particularly high forces. Ceramic materials are very much harder than steel and hardly wear at all. Working in co-operation with partners from research and industry, the Fraunhofer Institute for Production Technology (IPT) has demonstrated a way of producing such high-performance ceramic inserts for press tools.
The results of the Keraform project are now available. However, the advantage of the material, its extreme hardness, is also a drawback: high-performance ceramics are so hard that they can only be worked with diamond. “The complex shape of the inserts represents a special challenge,” says IPT project co-ordinator Andreas Weber. “This is where we need new process technologies.” The Fraunhofer crew has identified three conventional methods that are basically suitable for the job, and has optimised them for its own purposes. The best results were achieved with jig grinding, a method in which a small, very rapidly rotating grinding tool moves across the ceramic part to create the desired shape.
Using ceramic-reinforced forming tools is particularly beneficial when large numbers of parts are to be produced. The Fraunhofer team intends to apply the experience gained from this project to open up further fields of application for high-performance ceramics. Meanwhile, examples of extremely hard and precisely-shaped ceramic manufacturing tools were presented at Euroblech 2006.
For more information, visit www.fraunhofer.de
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