HIGH SPPED END MILLING OF HARDENED STEEL(2ND REPORT)- COMPARISON OF HIGH SPEED MILLING MACHINE WITH AIR BEARING SPINDLE AND THAT WITH BALL BEARING SPINDLE-

摘要

This study deals with the technology of high speed end milling of hardened steel by a high speed milling machine with an air bearing spindle. In a previous paper, it was shown that use of such machine enables stable machining to be carried out. Nowadays most of high speed milling machines are equipped with ball bearing spindles. Bu basic feature differences of high speed end milling of hardened steel when using air bearing spindle and ball bearing spindle, have not been clarified. In this paper, static and dynamic stiffnesses of high speed milling machines with a different type of spindles are discussed. Basic features of high speed end milling hardened steel, vibrations ,surface roughness and tool lives are also discussed. The main results are as follows:(1) The static and dynamic stiffnesses of the air bearing spindle and the ball bearing spindle are obtained by experiments.(2)The feature of high speed end milling are obtained by experiments for each type of spindle machines.(3) In a high speed milling machine with an air bearing spindle, the static and dynamic stiffnesses are lower than those of a machine with a ball bearing spindle. But under comparatively high spindle speed conditions, tool lives are linger and surface roughness are better the an those in case of a ball bearing spindle machine.