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More holes with each tool
Tool wear has always been a big problem when drilling in abrasive materials like CFRP. In some cases just a few holes can be drilled before the cutter has to be scraped or re-ground. Different type of coating and cutters has improved the lifetime but still the process is very expensive and time consuming. Especially in complex stacks with material combinations like CFRP/Ti or CFRP/Al, the process parameters will be a large compromise and even more reduce the lifetime of the cutters.
Novator has developed a new method to compensate for tool wear when drilling in stacks of complex materials. The method combines the unique feature to dynamically adjust the drilling diameter in very small steps in an Orbital drilling End-effector and a new type of software algorithm to predict and compensate for the tool wear in different materials. The combination of Orbital Drilling and tool wear compensation makes it possible to drill a large number of holes with tight tolerance and to significantly increase the lifetime of the cutting tool.
When drilling in complex stacks such as CFRP/Al, both the wear factor and compensation curve are totally different in the two materials. The wear in Aluminum is very small but the necessary compensation could be rather large. The Orbital Manager software and the compensation algorithm makes it possible to create a recipe that dynamically adjust the offset and other process parameters during the drilling process to compensate both for the different material characteristics and tool wear.
As shown in the left example above, the average diameter, defined as the mean value of all measured points for each hole, gets about 60 µm smaller during the drilled series of 300 holes. This is the actual wear of the cutting tool during the drilled series of holes. The same example as but with an implemented tool wear compensation algorithm, the variation in average diameter stays within a tolerance of 7 µm. If the accepted tolerance band is 55 µm the Cpk value will be 2,974.
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