M. Sortino

Application of statistical filtering for optical detection of tool wear

The application of automated tool condition monitoring systems is very important for unmanned machining systems. Tool wear monitoring is a key factor for optimization of the cutting processes. Basically, tool wear monitoring systems can be subdivided into two classes: direct and indirect. Currently direct tool wear monitoring systems are most frequently based on machine vision by camera. Several approaches have been studied for tool wear detection by means of tool images, and an innovative statistical filter proved to be very efficient for worn area detection. A new approach has been implemented and tested in order to develop an automatic system for tool wear measurement. This new approach is described in this paper and the main topics related to tool wear monitoring using wear images have been discussed.

Compensation of geometrical errors of CAM/CNC machined parts by means of 3D workpiece model adaptation

In modern industry conditions, it is very important to develop methodologies for reducing costs and achieving the maximum quality of machined parts, especially considering the dimensional accuracy of workpieces. Geometrical and dimensional inaccuracies are due to several factors, such as workpiece and tool deformation during machining, thermal distortions, tool wear, and machine tool inaccuracy. There are two main approaches used to improve the accuracy of workpieces: mapping the tool-workpiece displacement and altering the finishing tool path or the interpolated tool position to compensate the dimensional errors. The aim of this paper is to propose a new compensation approach, based on adaptation of the geometrical 3D CAD model used to generate trajectories by CAM software. The concept is to produce a first workpiece using a CAM-generated tool path. Then, the workpiece is measured using optical methods and the displacements between the ideal workpiece model and the measured point-cloud are calculated. Eventually, the displacement vectors are applied to calculate a compensated workpiece model. Such model is then used as a reference by CAM software to calculate the compensated tool path, which is applied for production of subsequent workpieces. The mathematical background and implementation details are given together with an example of application to a benchmark workpiece purposely machined with inaccurate tools. As the results show, the new approach was able to compensate the geometrical inaccuracies of the benchmark workpiece.

Application of a Rotating Dynamometer for Cutting Force Measurement in Milling

The measurement of the cutting force is important from the theoretical and practical point of view. An investigation of cutting forces and torque in milling with a rotating dynamometer is described. Rotating dynamometer is more practical for milling, drilling and taping than the plate dynamometer, since it is mounted on the spindle of the machine tool independently of the size of the workpiece. The experimental results have been compared to estimated instantaneous forces computed by using Kronenberg’s approach. The measurement system has been tested. Also, the dynamic and static characteristics of the rotating dynamometer are presented.

Some Approaches in the Machining Research

The paper discusses some approaches in machining research. Development of empirical technology, as well as of science-based (predictive) technology, and development of computer-based technology are presented. The application of mathematics of statistics and design of experiments, simulation of machining processes such as analytical simulation, geometrical simulation, finite element simulation, and supervision systems in machining are discussed. Also, the importance of machining research for computer integrated manufacturing enterprise in global market conditions is discussed.

A New Approach to the Use of Vibration Signals in Tool-Wear Monitoring in High Speed Metal Turning

Tool wear monitoring plays a very important part in production quality, volume and downtime of a machine tool. In order to reduce scrap levels, tool wear must be monitored and cutting tools changed when they might adversely affect the product quality. The investigation reported in this paper was aimed at furthering our understanding of the relationship between cutting tool wear and vibration signatures. A series of turning tests were conducted using double-coated insets to machine alloy steel. The prevailing wear forms on the cutting tool were measured while the vibration signals were recorded. An analysis of the vibration signals indicated that there was significant correlation between some peak frequencies of the vibration signal and tool wear.