Recently in manufacturing field, high precision products as well as diversified small-quantity products have been demanded and the spearhead production technologies constantly have been developed for low production cost. Therefore, a growing interest in shorter machining time with increasing cutting speed has been taken. However, the spindle speed increase of machine tools for productivity improvement also incurred the chattering, noise and heat generation of spindle bearing systems.
Since the interference between cutting tools and workpieces during machining produces high energy, the chattering of machine tools occurs if the width of cut or the cutting speed exceeds the stability limits of machine tools. The chattering which is a vibration of a cutting tool relative to a workpiece not only makes the surface accuracy of products worse but also increases tool wear. From the machine tool dynamics, it has been known that the maximum width of cut is proportional to static stiffness and damping ratio at the cutting point of machine tools and chattering occurs near the natural frequencies of machine tool structures.
Therefore, the material for the machine tool structure should have high stiffness and damping in its property to improve both the static and dynamic performances. Sometimes high specific stiffness (E/() is more important than stiffness (E) to increase the natural frequency of the structure in high speed machining. The machine tool structure can be stiffened through the use of proper materials such as composite materials for the spindle even if the properties of the other parts of the machine tool cannot be completely controlled.
As the fiber reinforced composite material has excellent properties for structures, owing to its high specific modulus, high damping and low thermal expansion, the vibrational and thermal characteristics will be improved if the proper design and manufacturing methods for the composite spindle systems are developed.
In this paper, the design and manufacturing methods as well as the static, dynamic thermal characteristics of the carbon fiber epoxy composite spindle bearing system and the aerostatic bearing system were investigated using analytical and experimental methods to improve the performance of the spindle bearing system and the aerostatic bearing system. Moreover, the design and the manufacturing methods of the steel-composite hybrid headstock were investigated.
