Toshio Sata

The Integration of CAD and CAM by Application of Artificial-Intelligence Techniques

This paper reports on the development of a new type of process planning system by application of two artifical-intelligence techniques: “Production system” and “Backtrack search”. This system can automatically generate the optimum machining sequence for the finished geometry in the data base given as the out-put from the CAD system. This system uses empirical knowledge about machining stylized into Production Rules, and a separate deductive algorithm. The system is written in PASCAL which permits use of user-defined data structures and recursion. These features bring flexibility, generality, and simplicity to the system. The results are put into an EXAPT part program which is ready for execution. This allows for the integration of COMPAC and EXAPT.

A Cutting Simulation System for Machinability Evaluation Using a Workpiece Model

Abstract This paper describes a cutting simulation system to be used in the evaluation of machinability of products at various stages of the manufacturing processes. The system developed consists of geometric simulation and physical simulation. The geometric simulation is performed by using extended Z buffer models representing a workpiece and a tool swept volume. In the physical simulation, instantaneous cutting force vectors acting on a square end mill are computed based on the am of chip element removed by a thin divided section of a flute. The tool deflection induced by the cutting force is then calculated. The result is used to estimate the machining error caused by tool deflection. A series of cutting experiments are conducted to verify the effectiveness of the system.

Operation Planning Based on Cutting Process Models

Abstract This paper describes model based operation planning for pocket milling operations. The tool path and cutting conditions are determined based on the geometric model of workpieces and the physical models of the cutting process. The tool path is generated by using the Voronoi diagram of a cutting area. Cutting conditions to achieve the maximum metal removal rate are determined by evaluating the physical models of cutting torque, chatter vibration, and machining error. To maintain a favorable cutting state, the radial depth of cut is controlled by modifying the tool path distance at the circle path segment and by adding additional tool path segments at the corner. Examples are shown to demonstrate the effectiveness of the method.

Analysis of surface roughness generation in turning operation and its applications

Summary Surface roughness generation in a turning operation is examined by using a FFT analyzer. It is found that the roughness profile of a workpiece is composed of several periodical components: the cutting tool feed component, the spindle rotational error component, and the chatter vibration error component. A block diagram of surface roughness generation in a turning operation has been drawn to give a clear illustration of the process. To examine the origin of these error components, a series of cutting tests were carried out with different spindle bearing arrangements and with different types of workpiece material. It has been shown that the method presented in this study is very helpful in evaluating the machinability of workpiece material and also in diagnosing the conditions of the machine tool spindle system.

Development of a Personal CAD/CAM System for Mold Manufacture Based on Solid Modeling Techniques

Abstract The paper deals with the development of a cost-effective CAD/CAM system for producing molds by means of a 16-bit microcomputer. The solid modeling technique containing four kinds of primitives. rotational body and sculptured surface as shape elements is employed to construct complex mold shapes in the computer. The solid model of molds is converted into a kind of spatial array, Z-map. to easily obtain the offset surface by means of the inverse offset method. The system with several functions such as cavity-core conversion and simplified fillet processing is found to provide an effective tool for mold manufacture.

A System for Monitoring the Machining Operation by Referring to a Predicted Cutting Torque Pattern

Summary A system for predicting the cutting torque by using a geometric modelling system, and its application to verification of NC data and monitoring of the cutting process are described in the paper. The cutting process is simulated geometrically in a modelling system. Based on data obtained from the geometrical simulation and on technological data of the NC program, the cutting torque is estimated, by using an empirical equation, as a linear combination of the volume of the removed material and of the tool-workpiece contact surface area. The torque measured in the experiments was in good agreement with the preliminarily estimate. The system also proved to be applicable when machining a cast part with geometrical inaccuracies within a few millimeters.

Improvement in the working accuracy of an nc lathe by compensating for thermal expansion

Abstract This study proposes a practical and economical way of improving the working accuracy of an nc lathe by predicting and compensating for the thermal expansion of the tool during machining, a phenomenon which greatly affects the machining accuracy. The thermal expansion can be calculated accurately by the program in which the amount of heat generation is represented as a function of cutting condition and cutting time. As the program judges that the expansion of the tool exceeds or falls below a certain value, tool offsets are made in the direction of cut in advance of operation. Cutting tests on an nc lathe with this compensation have shown a marked improvement in the machining accuracy

Generation of NC Commands for Sculptured Surface Machining from 3-Coordinate Measuring Data

Summary A system to generate the geometric information needed for NC machining of a sculptured surface is presented. In this system the geometric model of a sculptured surface is generated in the computer from 3-coordinate measuring data of a solid model made of clay, wood, or plastics. To describe the sculptured surface mathematically, Hasakas method for a Bezier surface is used. A cutter path for NC machining is generated from the geometric model of the surface. Some experiments were performed to measure a sculptured surface by use of a NC 3-coordinate measuring machine and also to generate the geometric model of the surface. Geometric information for NC machining was produced and the machining was successfully carried out.

Fractal Path Generation for a Metal-Mold Polishing Robot System and Its Evaluation by the Operability

This paper suggests a new method of Fractal path generation in a robot system of polishing metal molds It is conducted through the generation of a planer Peano curve in the X-Y domain and its orthogonal projection onto the free-form surface of a workpiece The orientation of the end-effector along the path is set perpendicular to the surface By calculating the sum of operability of the robotic linkage along the path the path can be evaluated from the ease of the rebots’ motion The experiments inclusive of the polishing force control are illustrated and a brief conclusion made.

Prediction of Chatter Vibration by Means of a Model-Based Cutting Simulation System

Abstract This paper describes a system for predicting charter vibration in ad milling operation. The system estimates instantaneous cutting force vectors based on geometric models of a workpiece and a tool. The vibration of the tool induced by cutting forces is calculated by using a lumped-parameter model with two degrees of freedom. Considering changes in cutting volume due to tool deflections and regenerative effects, the numerical simulation of dynamic tool movement is conducted to check the occurrence of chatter vibration. To reduce the evaluation time, a simplified stability criterion is introduced to exclude apparently stable conditions. A number of cutting experiments were carried out to verify he effectiveness of the system.