What had long been regarded as impossible has become reality: ultra-hard materials can be machined by high speed milling. It is a kind of mini-revolution that begins in the construction of moulds, tools and components for advanced applications. To be profitable, this process should however be reserved for very specific fabrications.
By “ultra-hard materials” we mean sintered carbide based metals (hard metals) and ceramics. These two types of materials are composites, which are distinguished by their extreme hardness, their high resistance to wear and in part by their ability of resistance to chemical processes. They also have in common the need to be machined to obtain the desired shape. Till today the procedures used had been grinding, polishing and EDM.
What then of high speed milling of hard metals? So far, users were not perfectly able to use that technology. Materials with hardness exceeding 90 HRC are extremely damaging both to cutters and spindles. “We believe that the optimal combination is the joint use of a suitable Kern milling machine equipped with special tools , appropriate hard metal and an adapted milling strategy”, says Martin Bräm, director of the company of the same name (Switzerland).
The parts ordered have been machined in a fine-grained hard metal, consisting in 91% of tungsten carbide with a hardness of 91.5 HRC. The tools were equipped with a new type of diamond coating and were chosen for their longevity. “Resistance of the coating was astounding: it held, held and still held. Even our milling specialists did not believe in it. Once the first envelope worn out, the tool was long time stable” says Mr. Bräm. The director adds: “We’ve also made tests of high speed machining in ceramics and the results exceed our expectations too”.
For Martin Bräm, the goal is now to convince most users of hard metal of the possibilities of this process.
For all markets
The company aims in priority manufacturers of tools, moulds and dies for stamping, but all sectors can benefit from this advanced technology, for example in the realization of cutting tools, machining of forged parts or realization of watch cases in ultra-hard materials.
Kern Mikro- und Feinwerktechnik GmbH
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