MANUFACTURING AND TESTING THE FLEXIBLE FIXTURE WITH THE ACTIVELY ADJUSTION OF WORKPIECE VIBRATION IN MILLING PROCESS

Abstract

A flexible fixture system to actively adjust the structure parameters of the machine - cutting tool - workpiece
vibration system was successfully designed, manufactured, and tested. The flexible fixture was designed and
manufactured with the integration and balanced arrangement of 4 springs, 2 dampers in the X direction, 4 springs, 2
dampers in the Y direction and 4 springs in the Z direction. The stiffness of the springs is adjusted by loosening or
tightening the spring tensioning nuts. Adjusting the stiffness of the spring leads to a change in the natural frequency of
the system and influence on the vibration and cutting force in the machining process. Under the normal nut tightening
conditions, the cutting force and vibrations are both smaller than when the using the normal fixture or when using the
flexible fixture with the nut to be tightened more. When using this flexible fixture, if the spindle speed is increased from
750rpm to 4000rpm, the vibrations and cutting forces increase gradually at first, and then, both cutting force and
vibrations are all decrease. In this study, the natural frequency of the system is between 67 - 100Hz. At the spindle
speed of 4000 rpm, the cutting forces and vibrations are both small and stable because the frequency of the cutting
forces is far from the natural frequency value of the system. When the spindle speed is 3000rpm, the cutting forces and
vibrations are large and unstable because the cutting force frequency is close to the system's natural frequency value.