CVD‐Diamantschleifstifte für den Werkzeug‐ und Formenbau. Abrasive Pencils for Tool and Die Making Coated by Diamond CVD

Recently developed compeDIA®‐ abrasive pencils have been produced and tested for the machining of cemented carbide molding tools. In order to produce abrasive pencils, carbide base plates have been grinded and coated with a diamond layer by a Hot‐Filament‐CVD‐process. The testing of the abrasive pencils took place with an ultra‐precision grinding machine on carbide workpieces. Surface roughness of the workpiece and its wheel life were the criteria for evaluation. For the specific adjustment of the grain size of the abrasive pencils, the adequate coating parameters were worked out, and the dependencies on basic influencing variables at coating procedures, such as nominal diameter and grinding length, were calculated. In order to be able to coat the grinded base plates with enough film adhesion, a practical pre‐treatment method was developed and tested, which removes the fringe zone, that was damaged during the grinding process. At present, the costs for the coating process are uneconomically high, though. By means of large‐scale production in connection with an automated pre‐treatment and coating it would be possible to lower the costs so far that they are on the same cost level with other coatings like TiN or TiAlN. The CVD‐Diamond abrasive pencils are very appropriate for tool and die making. It is to be expected that through further development of tools and through process optimization, the quality of the wrought workpiece can be ameliorated and surface finishes of R_a < 0,3 μm can be reached. The wheel life could be increased to appropriate values by optimization of the coating technology. The range of the machining parameters, in which the grinding process can be accomplished expediently without leading to a broken die, have been worked out. Afterwards, a die‐casting component with typically shaped elements was designed and an adequate molding tool prototype was crafted. With that, the basic conditions for tool‐ and die‐making were worked out in order to put into practice a fast and flexible machining of cemented carbide molding tools with the aid of those innovative abrasive pencils. In contrast to the traditional molding tool material made of brass, clear advantages in tool life can be made in the production of miniature serial‐parts by drawing, deep‐drawing or extrusion.