Machining accuracy of machine toolsDownload Now
Productivity and accuracy of machine tools are important competition aspects. Rapidly changing operating conditions for machine tools, however, make it difficult to increase productivity and accuracy. In the manufacture of parts, increasingly small batch sizes have to be produced economically, and yet accurately. In the aerospace industry, maximum cutting capacity is needed for the roughing processes, whereas the subsequent finishing processes must be executed with maximum precision. For milling high-quality molds, high material removal rates are required during roughing and excellent surface quality must be obtained after finishing. At the same time, maximum contouring feed rates are necessary to realize the required minimum distances between the paths within acceptable machining times.
Thermal accuracy of machine tools is becoming increasingly important considering the strongly varying operating conditions in manufacturing. Especially with small production batches that require constantly changing machining tasks, a thermally stable condition cannot be reached. At the same time, the accuracy of the first workpiece is becoming very important for the profitability of production orders. Constant changes between drilling, roughing and finishing operations contribute to the fluctuations in the thermal condition of a machine tool. During the roughing operations, the milling rates increase to values above 80%, whereas values below 10% are reached during finishing operations. The increasingly high accelerations and feed rates cause heating of the recirculating ball screw in linear feed drives. Position measurement in the feed drives therefore plays a central role in stabilizing the thermal behavior of machine tools.