Design and manufacture of composite high speed machine tool structures

The high transfer speed as well as the high cutting speed of machine tools is important for the productivity improvement in the fabrication of molds/dies because non-machining time, called the air-cutting-time, amounts to 70% of total machining time with complex shape products. One of the primary reasons for low productivity is large mass of the moving parts of machine tools, which cannot afford high acceleration and deceleration encountered during operation. Moreover, the vibrations of the machine tool structure are among the other causes that restrict high speed operations. In this paper, the slides of high speed CNC milling machines were designed with fiber reinforced composite materials to overcome this limitation. The vertical and horizontal slides of a large CNC machine were manufactured by joining high-modulus carbon-fiber epoxy composite sandwiches to welded steel structures using adhesives and bolts. These composite structures reduced the weight of the vertical and horizontal slides by 34% and 26%, respectively, and increased damping by 1.5-5.7 times without sacrificing the stiffness. Without much tuning, this machine had a positional accuracy of +/-5 mum per 300 mm of the slide displacement. (C) 2003 Elsevier Ltd. All rights reserved.