4654957 - Flexible machining apparatus with single shank tool and multi-spindle tool head changing and operating capabilities

Abstract

This paper presents a new method and its analysis to suppress regenerative chatter vibration in simultaneous multiple milling with a flexible mechanical structure. Precision steel plates are conventionally finished by one-sided face milling with a rigid electro-magnetic chuck. However, it is difficult to obtain the desired flatness with this method since the thin workpiece deforms to fit the chuck surfaces when chucked. The authors have solved this problem to realize both high accuracy and productivity by applying the simultaneous double-sided milling technique utilizing the developed speed difference method, in which the regenerative chatter is cancelled by rotating two milling cutters at different speeds on both sides of the workpiece. The present study represents an analytical model of the simultaneous double-sided milling including the regenerative chatter vibration effect on the process. Machining experiments are conducted to validate the developed analytical model. Experimental results match with the analytically predicted ones proving that the proposed model accurately predicts the regenerative stability limits in double-sided milling. The results also show that the developed speed difference method can provide great advantage to increase the chatter stability and carry great potential to enhance the productivity in machining of flexible thin workpieces. Furthermore, simultaneous multiple-spindle machining methods have become much desired in mass manufacturing systems as they prove higher manufacturing efficiency. The proposed speed difference method is extended and generalized to those multi-spindle simultaneous milling operations with flexible mechanical structures. Analytical derivations and the foundation are presented here on how to calculate the necessary speed differences between milling spindles to suppress regenerative chatter vibrations.