Original Date: 10/07/2002
Revision Date: 01/18/2007
Information : Composites Machining
General Tool Company has made great strides in the machining of non-metallic or composite materials. Through controlled experimentation of cutting speeds and feeds, and intensive investigation of tool types and geometry, the company has been able to develop affordable machine processes and products for its customers.
The machining of composite materials, both conventional “lay ups” and filament wound materials, presents unique challenges to the manufacturing community. The composites exhibit different machining characteristics than common metal alloys normally encountered in manufacturing. They respond differently to conventional machining processes and, due to their abrasive nature, greatly reduce the useful life of standard cutting tools.
General Tool Company (GTC) has been able to overcome some of the obstacles of machining composites. Working together with different cutting tool manufacturers and through much experimentation, GTC has been able to develop standards and processes that enable it to successfully machine composite materials for its customers. Some of the key solutions for success include high spindle speeds, light or shallow depth of cuts, and aggressive feed rates approaching 140 inches per minute in some cases. Part geometry and holding fixture rigidity dictate the correct speeds and feeds.
A real key to successfully machine these composites at an affordable cost lies in the cutting tools used. Several attempts with special carbide and high speed steel tools have produced varied results in both tool life and varying degrees of delamination of the composite structure. One of the most promising cutting tools used for drilling is an eight-faceted, thinned web, diamond tipped carbide drill. This tool enabled GTC to reduce cycle times and greatly increase tool life in small hole drilling. Milling of composites is generally accomplished with diamond mesh end mills. This operation is more of a grinding operation in lieu of milling.
Through ongoing investigation of tool types and tool geometry, GTC has found that more improvements are attainable. Continued experimentation with speeds and feeds will find the best way to produce quality parts on a consistent basis. GTC has made process improvements and changes in tool specifications, which have resulted in reduced cycle times and improved tool life.
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