I. Yellowley

Stress distributions on the rake face during orthogonal machining

Abstract The authors describe the design, calibration and testing of a split tool dynamometer that has been developed to allow the estimation of rake face stress in a true orthogonal machining process. The device is unique, in that force measurements can be made on the front and rear portions of the cutting tool simultaneously. The normal and shear stress distributions over the rake face of the tool have been calculated based upon cutting tests using AISI C1045 steel, SAE CA360 free cutting brass and AISI 304 stainless steel discs as the work material at a cutting speed of 130 m/min. The experiments also gave insight into the chip sticking length and comparison with scanning electron microscope (SEM) images of the rake face revealed that the dynamometer indeed provides an accurate assessment of the overall chip contact length along the rake face.

Design, implementation and validation of a system for the dynamic reconfiguration of open architecture machine tool controls

This paper discusses the design and implementation of a system and protocol for the automatic configuration and dynamic reconfiguration of distributed machine tool control systems. A novel servo controller, based on a Field Programmable Gate Array (FPGA) hardware architecture is used to demonstrate the feasibility of the configuration system.

The optimal subdivision of cut in multi-pass machining operations

The examination of the economics of multi-pass machining operations has significant practical importance, particularly in the development of algorithms for process planning, and area clearance macros for numerically controlled machine tools. The authors show that, for both turning and milling operations, the optimal widths of cut may usually be evaluated without a knowledge of the relevant tool-life equation. The exception to this finding occurs when either a power or torque constraint is active. The authors demonstrate that in the presence of such constraints the optimal widths can still be evaluated without extensive computation.

The integration of process and geometry within an open architecture machine tool controller

Abstract The authors discuss in detail the anticipated future requirements of an advanced control for metal cutting machine tools; of particular interest is the integration of process monitoring and optimization with the normal processes of interpolation and axis control. A detailed discussion of the philosophy underlying the development of the UBC open architecture machine tool controller and its current capabilities is also presented.

An upper-bound cutting model for oblique cutting tools with a nose radius

The geometry of practical cutting tools is complex, and usually involves both non straight cutting edges and obliquity. It is of great practical importance to be able to predict cutting forces and chip flow directions for such tools. The authors demonstrate the use of a simplified geometry together with an upper bound model to predict the direction of chip flow. The model proposed includes a requirement for approximate force equilibrium as a method of estimating rake face contact area. A comparison of the results with those from earlier models and with experimental data is provided. Finally a proof of the Stabler chip flow hypothesis is given: it is shown that the hypothesis is only valid for the case of zero rake face friction.

The influence of thermal cycling on tool life in peripheral milling

Abstract An analysis of the thermal strain produced in the peripheral milling process is presented. It is shown that the time in and out of cut has considerable influence on the range of thermal strain developed in the cutter teeth. The range of thermal strain and also the number of cycles of thermal strain is shown to have considerable influence on tooth life.

The Identification of Radial Runout in Milling Operations

The authors discuss a novel approach to estimation of individual tooth runout in milling. The approach is based upon a simplified linear force model and leads to good results at high values of immersion. Two variants of the approach for estimating runout are presented. The first method utilizes torque while the second considers in plane force components as indicators of runout. Simulations are used to verify the equations that were derived for relating runout to in plane forces and to allow the assessment of the influence of the spacing of the discrete force samples on accuracy. Experimental evidence validates the approach for a wide range of immersion values. Experiments also show that the approach is able to identify edge breakage in the presence of significant initial runout.

Process control and dynamic process planning

Real time machine tool control and the planning activities which precede manufacture are usually interfaced through a low level language which allows little more than position, feed, and speed information to be passed between the two systems. The higher level systems used to describe geometry and tool paths also lack an adequate capability to describe manufacturing processes. The authors discuss the provision of a much richer interface between the planning and control activities which both facilitates the identification and scheduling of suitable monitoring tasks and allows the updating of process plan data from real time measurements. The result of such integration is an improvement in the efficiency of real time optimisation, and perhaps most importantly the possibility of quasi real time process planning. A system that is able to perform both initial process planning and plan refinement based upon low level feedback must also encompass the path generation activity, such a system is referred to by the authors as a dynamic process planning system. The paper describes the fundamentals of the process models, identification algorithms, control strategies, and low level process plan generation used within such an integrated system.

FPGA-based servo control and three-dimensional dynamic interpolation

The design and implementation of a field-programmable gate array (FPGA)-based controller that employs three-dimensional dynamic interpolation (3D/sup 2/I) for process and system dynamics compensation is described. A strategy for multiple-constraint based tool deflection compensation employing the 3D/sup 2/I mechanism is also presented as an example of the utility of the approach.

The regulation of position error in contouring systems

Abstract The authors discuss the use of a novel hardware configuration in the control of position error during contouring operations. The architecture described allows real time error control in multiple axis systems; this is achieved by allowing any axis with a phase lag which exceeds that specified, to slow down the entire system until it is in conformance. The performance of the system is demonstrated by both simulation and experiment, using cornering and circular interpolation as examples. The major contribution of the work is thought to be the ability of the system to cope, in real time, with system constraints and nonlinearities.