Abstract The paper describes details of the development of a new CNC lathe tooling mechanism with on-line adjustable cutting edge inclination angle, which is one of the major tool geometry parameters in machining operations。 The mechanism is based on the combination of (i) three linkages which adjust the tool incli- nation angle automatically and continuously, (ii) three curved slots which work simultaneously to compen- sate the tooltip deviations accurately, and (iii) an input link driven by a linear stepping motor that converts the linear stroke into tool angle rotation。 The prototype developed provides a new tooling mechanism for the prospective open architecture-based CNC machines。 2000 Elsevier Science Ltd。 All rights   reserved。87919

Keywords: Tool inclination angle; Tool geometry; CNC  machining

1。 Introduction

Tool geometry parameters play an important role in determining the overall machining perform- ance, including cutting forces, tool wear, surface finish, chip formation and chip breaking [1,2]。 The importance of optimizing tool geometry has been highlighted recently to be of enormous economic significance in maximizing tool life in machining [3]。 Over the past few decades, many investigations have been made to study the important effects of tool geometry, including tool inclination angle, on machining performance。 It is well known that the tool inclination angle is a major factor in determining the chip flow direction in machining [4] and has been used in various mathematical models of chip flow [5,6]。 In finish turning process, a well-controlled tool inclination angle can effectively guide the chip to flow in a desired direction to reduce the risk of chip entanglement [7,8] and protect the machined surface, thus achieving effective chip control

in automated machining systems。 Tool inclination angle has also been included in some researchers’ machinability models [9,10] due to its significant effect on cutting forces。

CNC machines are the core of CIM。 With the recent worldwide R&D efforts in developing new- generation CNC machines equipped with open-architecture control systems which allow modular integration of sensors, process monitoring and control units with CNC machines, not only the cutting tool path but the machining process performance could be programmed and controlled in real-time CNC machining operations [11–13]。 However, no  successful work  has been  reported on development of the tooling mechanism with on-line controllable tool geometry that can be used in CNC machines。 There are only two relevant reports based on a recent literature survey in the field。

The first one, published by Kolder and Ber in 1990 [14], is a mechanical universal toolholder which allows the user to set up the optimal tool geometry parameters through continuous change of the tool angles。 However, the prototype they developed is not applicable to real-time control requirements or CNC machining operations due to the following two major limitations,

1。 The mechanism for setting the tool angles is based on the off-line manual operation。

2。 The resulting tooltip deviations have to be adjusted manually by the try-and-see method。

The second one, published in 1996 by Fang and Najmossadat [15], has the ability of automatic control of the tool inclination angle, however, their prototype also has limited applications, mainly due to the following two  reasons:

1。 The tool angle changing mechanism is based on three linear slopes to approximately compen- sate tooltip deviations, thus results in limited changing range of the tool inclination angle  (only

5) and limited compensation accuracy of tooltip   deviations。

2。