Development of a High Speed Non-circular Machining NC-lathe for Cutting a Piston-head of a Reciprocating Engine by Use of a New Servomechanism Actuated by Electromagnetic Attractive Force

Abstract

This paper presents a new high speed and high precision NC-lathe for machining a piston-head of a reciprocating engine. In the machining of a piston-head, a cutting tool positioning servomechanism is needed, because the machining of a piston-head is the non-circular machining, in which the stroke of the cutting tool positioning is 0.1-0.5 mm. Previously a new servomechanism actuated by electromagnetic attractive force was developed as a cutting tool positioning mechanism. But a prototype of this servomechanism did not make a high speed non-circular machining possible, as the response performance was not at a satisfactory level. Thus, to enhance the response performance, the prototype has been redesigned with the use of some plate springs, the decrease in mass, the restraint of eddy-current loss and so on. Also the periodic learning control method with the inverse transfer function compensation has been applied to the positioning control for the high accurate positioning. These modifications lead the developed NC-lathe for a piston-head to the achievement of practical machining with an accuracy of 2 μm at 3000 min^-1.