Machining Accuracy of Machine Tools
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 fi rst workpiece is becoming very important for the profi tability of production orders. Constant changes between drilling, roughing and fi nishing operations contribute to the fl uctuations 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 fi nishing 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.