F. Giusti

On-Line Sensing of Flank and Crater Wear of Cutting Tools

Abstract It is well known the high interest for on line sensing of tool wear with the aim of controlling machine tools productivity from the point of view of quality and quantity. Difficulties in this measurement are also known. This paper describes a sensor based upon the TV image analysis of a worn tool. The flank wear is measured observing the active cutting part from a proper direction and lighting the wearland by a fiber optic system. The crater wear is visualized by lighting the tool by a laser system developed by the authors; from the obtained image it is possible to extract the position and the dimensions of the crater and a complete mapping. By means of these system it is possible to evaluate classical parameters of tool wear and to have complete information about tool wear morphology. The paper describes also the software strategy developed for image analysis which has been studied as a compromise between measuring time and required precision. Experimental tests performed with the prototype on a NC lathe have shown good performances here described and discussed.

COATS: an Expert Module for Optimal Tool Selection

Abstract After an introduction in which the usefulness of expert systems in the field of process planning is discussed, the paper describes an expert module for fully automatized tool selection in turning operations: the module is a part of a process planning package developed by the authors. The structure of the module includes a knowledge base where production rules IF-THEN can be easily created, edited and deleted by means of an interactive program and a dictionary without being a software specialist, in order to fit the module to different industrial environments. Each rule must be written together with a “weight” evaluated upon the basis of each tool parameter and its influence on cutting process: a reference guide is given for this purpose. After consulting the rules the module proposes the best toolholder-insert couples found in properly created tool files. The “score” of each tool selected is computed by rules weight. Tests carried out have given good results some of which are here described. Then an approach to self learning is described, which allows the module to improve its knowledge base upon the basis of experience, properly evaluated by a monitoring and diagnostic program: automatic creation of new rules is so possible. The advantages of this module are flexibility and possibility to be directly connected with workshop environment.

KAPLAN: a Knowledge-Based Approach to Process Planning of Rotational Parts

Abstract This paper describes a generative CAPP system named KAPLAN (Knowledge based Approach to process PLANning) studied for the fully automatic generation of production plans of rotational parts. The program structure is based on knowledge base techniques and the knowledge required for the plan generation is represented by IF-THEN rules, easily adaptable to every workshop environment by means of an user interface. An integration between CAD and CAPP obtained by means of a design module has allowed a complete and effective management of data flow in a full automatic way up to the production plan with all the needed information. The used technique allows to generate all the possible plans for a mechanical part and to select the best one according to the selection criteria stored in the knowledge base. The program is a part of a more complex CAPP system, together with other modules for the complete planning of the work done in a FMS cell installed in the Institute of Mechanical Technology of Pisa. The paper reports some meaningful examples of cases efficiently solved by KAPLAN.

A Flexible Tool Wear Sensor for NC Lathes

Modern NC machine tools require a more and more exact monitoring and control of cutting process: this function must be per formal by simple and reliable sensors. A very important parameter is tool wear used to optimize cutting data, to control tool position and to change tools at the right time. A new type of tool wear sensor is described, whose working principle is a simple automatic analysis of the whole wearland TV image. The mechanical and optical structure of the sensor is particularly flexible to fit different kinds of tools mounted on a turret of a NC lathe. Many tests have been executed with different tools; results are reported and discussed. The good performances of this sensor make it particularly useful in the development of an ACO strategy, connected to a dynamic data bank inside the NC unit itself.

Robotized assembly of modular fixtures

Summary A prototype plant for the robotized assembly of modular fixtures for NC machining centers is described. After presenting a brief summary of the present tendencies relative to the design, preparation and management of the fixtures, the plant and its components are described in their general structure, posing particular focus on the geometric and functional features of the modular elements, designed in order to facilitate the automatic operations of manipulation and assembly. The plant is controlled by a software structured for design of fixture configuration, planning of the assembly sequence and off-line programming of the robot. Results obtained in assembly tests are also discussed, and emphasis is placed on the more critical aspects linked to the automation of this important operation. In conclusion, the possible applications of the automatic assembly of fixtures for FMS plants are proposed.

An integrated and flexible system for automatic tool assembly and disassembly

Abstract The concepts of automation and integration have now almost invaded all sectors of modern mechanical industry. The sector dedicated to the management and manipulation of tools is not exempt from this innovative process; however, important functions as the assembly and disassembly of tools from their respective innovative process; however, important functions as the assembly and disassembly of tools from their respective holders, are today still done by manual intervention. Taking into account such considerations, the possibilities of automating these operations through the use of one or more manipulating robots, was analyzed by developing and testing a prototype plant able to realize the assembly and the disassembly of tools in the toolholder for NC machining centers. Parallelly, a assembly software package was disassembly developed of in order to identify the list of objects to be manipulated, to plan the optimal sequence software package of the operations, to represent the view of the components on a graphic terminal, and to create the necessary part-program to control the robot movements. The various cases examined, from which some examples are reported, set forth the validity of the procedure followed and point out the problems encountered and the technics adopted for their solutions.