Machine tool and control device for machine tool

Abstract

A machine tool and a control device for the machine tool for shortening the machining time of a workpiece in a case where the relative and reciprocal vibration of workpiece holder and tool post in the radial direction of the workpiece is stopped during a period from an initial point until when the workpiece and the cutting tool come into contact with each other is provided. In the machine tool, when threading the workpiece to form a threaded portion on the workpiece by relatively moving the workpiece and the cutting tool in the feed direction while relatively rotating the workpiece and the cutting toolto perform multiple times of cutting processes along the same cutting path in a predetermined spiral form, the cutting tool is brought closer toward the workpiece in the feed direction from a predetermined initial point at which the workpiece and the cutting tool are separated from each other, the workpiece and the cutting tool come into contact with each other, and the threading is started with the contact. During the period from the initial point until when the workpiece and the cutting tool come into contact with each other, a controller stops the vibration of the cutting tool, and, in continuous cutting processes in the multiple times of cutting processes in the threading, the control means sets a phase position of the tool post in the vibration direction and stops the reciprocal vibration so that, when the workpiece and the cutting tool come into contact with each other, each of the continuous cutting processes has a predetermined phase in the reciprocal vibration relative to a rotation phase of the workpiece at the start of the threading.