Giovanni Tantussi

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.

A Sensor-Integrated Tool for Cutting Force Monitoring

Abstract This paper describes the development of a new concept of cutting tools using strain gages for the measurement of forces in turning operations. The basic idea is the integration of the sensor within the tool shank, in order to obtain a system which is easy to use, easy to install and capable of transmitting data to the CNC through wireless equipment. In particular, the output signal of the measurement bridge is amplified and sent to an external data acquisition system by infra-red transmission. The present paper reports the design principles and the results of some machining tests illustrating the behaviour of the tool in different cutting conditions.

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.

Computer-Aided Visual Inspection in Assembly

Abstract Some of the more critical aspects for the diffusion of vision systems in assembly plants are the skill required for the system set-up, the definition of algorithms and the programming phase. In this paper a new methodology is proposed to reduce the implementation time and cost by means of a computer-aided system working off-line. The designed system named CAVIS (Computer Aided Visual Inspection System) integrates several modules as product and algorithm databases, expert system for decision support, CAD modeller to generate synthetic images and software design. Some of the modules are still at a development stage. The output are the vision devices configuration and the inspection software. CAVIS has been tested on an industrial application for error detection in assembly: a new general-purpose algorithm for visual inspection is presented and results are discussed. The main features of the algorithm are suitable with the described approach: easy programming, unnecessary vision operators experience, and off-line preliminary estimation of parameters.

On-line control of robotized Gas Metal Arc Welding

Abstract On-line control of welding and soldering is a strategic issue for the complete automation of robotized plants. The proposed control system aims to detect the most critical defects in industrial applications. It is based on the analysis of images coming from two cameras installed on the welding torch: the arc and the pool observation allow monitoring the welding process; a laser stripe is used for the weld bead inspection. The image analysis algorithms developed are based on the extraction of features, which have been selected after a long series of experiments. In addition to pre-processing, different filters have been implemented to increase the system reliability, for the high noise in images. A basic control system is also addressed. The system has been tested in weld overlay cladding.

VISION SYSTEM CALIBRATION AND SUB-PIXEL MEASUREMENT OF MECHANICAL PARTS

In this article a measuring system based on artificial vision techniques is described. Even if this problem is not new, several aspects, including sub-pixel algorithms, system programming and lighting, that are addressed in this paper, are still under study. Among them, the vision system calibration is focused. The theoretical model and the practical details of a fast method for 2-D problems are described, by comparing 3-D techniques already in the literature. The main features of the developed system are: cheap and easy to use. An example application is provided for the overall performance assessment.

Design and development of a vision based leather trimming machine

The objective of the work described in this paper is to demonstrate a laboratory prototype for trimming the external part of a hide, assuming that the resulting machine would eventually form part of a completely automatic system in which hides are uploaded, inspected and parts for assembly are downloaded without manual intervention and prior sorting. Detailed literature and international standards are included. The expected advantages of integrating all vision based functions in a single machine, whose basic architecture is proposed in the paper, are also discussed.

An Approach Study to Selective Laser Sintering (SLS) of Pre-Coated Sands for Shell-Moulding

The Selective Laser Sintering of pre-coated sands is a promising Rapid Prototyping technique for the construction of sand shells for foundry. In this article, the definition of mathematical simulation concepts and a detailed experimental analysis, performed both with conventional and unconventional techniques, is proposed. In particular, two methods to calculate the temperature distribution within the sand bed and the depth of the heat-affected zone are studied. The results obtained with the experimental methodology and those coming from previous experimental analyses have been used to validate the described mathematical models, that represent a first step for the process comprehension, control and optimisation. Two kinds of pre-coated sands, widely used in shell-moulding, have been considered: zirconia and silica. The guidelines for future simulation refinements are also given.

Monitoring critical points in robot operations with an artificial vision system

Stereo Vision for assisted robot operations implies the use of special purpose techniques to increase precision. A simple algorithm in the reconstruction of 3D trajectories by real-time tracking is described here, which has been extensively tested with promising results. If the form of the trajectory is known a priori, the interpolation of multiple real-time acquisition yields an increase of precision of about 25% of the initial error, depending on the uncertainty in locating the points within the image. The experimental tests which have been performed concern the case of a straight trajectory.