Study on movement forming methods for the machining of elliptic-shaped holes

Abstract

The movement forming methods for the machining of elliptic-shaped holes are presented. These methods can make the tool nose orbit, which is the synthesis of revolution of the hydrostatic shaft center around bearing center and rotation of the tool nose around shaft center, become an ellipse. Thus, the machining of elliptical holes can be achieved. Necessary conditions and sufficient conditions for forming elliptic tool nose orbit, under the condition that multiple shaft center orbits and the tool nose's rotation orbit take synchronous forward synthesis and synchronous backward synthesis, are studied. The influence of initial phase angle of the tool nose on the formation of elliptic tool nose orbit has also been investigated. Characteristics and control equations of elliptic tool nose orbit under the conditions of multiple shaft center orbits and different initial phase angles of the tool nose are given. These studies will lay a theoretical foundation for the realization of the movement forming methods. Traditional machining methods for elliptic-shaped holes require auxiliary feed mechanism installed on the machine tool, and machining efficiency is limited by the frequency response characteristic of the servo bar. The forming methods presented in this article can overcome these shortcomings and provide a new approach for precision machining of elliptic-shaped holes.

Open-loop control of elliptical shaft center orbit

“…On the basis of previous work, 13,21,22 this article simulates open-loop control movement orbits of shaft center using Eulerian method. With open-loop control method, this research can control shaft center movement orbit and make it an expected ellipse.…”

“…Comparing with the pocket of common hydrostatic bearing, the control pocket has smaller pocket area and smaller flow, so the design of control pocket can improve the system control sensitivity and control speed. Based on the previous work, 13 this article uses openloop control method to control shaft center movement orbit and make it an ellipse, which synthesizes with rotation of the tool nose around shaft center. Thus, the machining of elliptical hole can be achieved.…”

“…So it is necessary to quest a much better boring method. A new machining method for elliptical holes is presented in the literature, 13 and the conclusion is obtained: when the shaft center revolution orbit is an ellipse, the motion synthesis between shaft center revolution orbit and tool rotation orbit can form the elliptical tool nose orbit. And thus, the machining of elliptical hole can be realized.…”

“…In this article, open-loop control simulation of shaft center orbit is carried out, which proves the feasibility of hydraulic control scheme and lays theoretical basis for the application of new machining method. 13 At present, the main simulation methods of shaft center orbit are Eulerian method, 14 Hahn method, 15, 16 Holland method 17 and mobility method. 18 Eulerian method is a dynamics simulation method, but the other three ones are static methods which ignore the accelerated speed of shaft.…”

Optimal control simulation of elliptical shaft center orbit with the hydraulic servo system

“…Thus, it is necessary to find a new processing approach. The literature 14 brought up a novel and interesting boring approach for elliptical hole and obtained the following conclusion: When movement orbit of shaft center is an ellipse, motion synthesis between the shaft center’s revolution orbit and cutting tool’s rotation orbit is able to form the elliptical tool nose orbit. Elliptical hole’s processing will be realized.…”