Tool Wear Measurement Research Articles

A method for detecting tool wear on a CNC lathe using a doppler radar detector

Installing a non-contact in-process tool wear detection system on a computer numerical control lathe can help prevent product defects and improve product quality without impacting product cycle time. Many methods have been proposed for non-contact in-process tool wear detection. In particular, a recent international patent application describes a method for measuring the torque in a rotating axle using a high-frequency wireless transmitter/receiver and a vibrating string. The method has reportedly been used to detect cutting on a manual lathe. The authors present a new method for measuring tool wear using a high-frequency wireless transmitter/receiver alone, without a vibrating string. The high-frequency transmitter/receiver apparently responds to metal-metal contact noise rather than, or more strongly than, to signals generated by a vibrating string. The findings could help bring automated tool wear monitoring systems closer to the level of performance needed for practical use in industry.

Performance evaluation of vegetable-based oils in drilling austenitic stainless steel

The efficiency of six cutting oils was evaluated in drilling AISI 316L austenitic stainless steel using conventional HSS-Co tools by measurements of tool life, tool wear, cutting forces and chip formation. Seven tools were tested with each fluid to catastrophic failure. Cutting forces and chip breaking were recorded for each bore, and tool wear was measured at constant intervals. A commercial mineral-based oil was taken as reference product, and five vegetable-based cutting fluids at different levels of additivation were tested. All measured parameters were in agreement, confirming that a performing fluid produces longer tool life, better chip breaking, lower wear and cutting forces. In particular, good correlation was found between tool life and cutting forces. Differences in cutting forces due to the fluid could be measured with a higher repeatability than tool life, thus resulting in a measurement capability comparable to that obtained using tool life as a performance criterion. As a consequence, it is suggested that drilling thrust can be used to assess the performance of cutting fluids in drilling stainless steel, resulting in considerable time savings and cost reduction with respect to tool life testing. All vegetable-based fluids performed better than the reference product. The best performance was obtained with a cutting fluid yielding 177% increases in tool life and 7% reduction in thrust force.

An enhancement of the machining performance of GFRP by oscillatory assisted drilling

Glass fiber reinforced plastic (GFRP) composites are finding their way into high technology applications. The machining of GFRP composites is needed to produce near nett-shaped components. Damage free machining is necessitated for the longer inservice life of composites. The present study attempts a newer technique of the oscillatory vibration assisted drilling of GFRP composites in order to minimise the damages. For comparison, conventional drilling also has been carried out. The cutting performance is analysed through online studies such as the measurement of force, power and A.E. monitoring and through the measurement of tool wear as an offline technique.

Tool probe for measuring dimensional wear and X-coordinate of turning edge

This paper presents an original method of direct measurement of turning tool wear at the tip of the cutting edge, made automatically on an NC lathe by a probe, which also allows for determining the X-coordinate of the cutting edge. In the initial solution, this measurement, patented by one of the authors, was carried out using a special probe with two-touch trigger sensors or a one-touch trigger sensor and a displacement sensor. The improved probe has only one displacement sensor. Not only does the new solution simplify the probe, but it also makes tool wear measurement more accurate.

Effect of Laser Pre-Treatment on the Machining Performance of Aluminum/SiC MMC

Although the abrasive reinforcement in MMCs primarily controls their machining behavior, the properties of the matrix also exert an influence. A 1200 W diode laser was used, due to the large footprint (5×0.3 mm) and the short wavelength (0.94 μm) to pre-treat a 2618 (18% SiC) alloy. The laser heating and self-quenching of the material modified the matrix properties. Machining performance was then assessed by measuring tool wear and edge condition, cutting forces, surface finish, and sub-surface damage. Results indicated that pre-treatment gave less wear, lower forces, and less sub-surface damage although abrasion remained the primary wear mechanism.

Cutting tool crater wear measurement with white light interferometry

In this paper we propose the use of white light interferometry for measurement of wear craters on cutting tool inserts. It was briefly discussed interferometry principles and tool wear during dry metal cutting, after which a discussion of the application of interferometry to cutting tool wear measurement was described. A comparison of the profiler data with the cutting forces measured during the metal cutting process in orthogonal mode under different conditions was undertaken. Lastly, a comparison between the tool wear to the evolution of the friction coefficient is given.

Machinability of hardened steel using alumina based ceramic cutting tools

Alumina based ceramic cutting tool is an attractive alternative for carbide tools in the machining of steel in its hardened condition. These ceramic cutting tools can machine with high cutting speed and produce good surface finish. The wear mechanism of these ceramic cutting tools should be properly understood for greater utilization. Two types of ceramic cutting tools namely Ti[C,N] mixed alumina ceramic cutting tool and zirconia toughened alumina ceramic cutting tool are used for our investigation. The machinability of hardened steel was evaluated by measurements of tool wear, cutting forces and surface finish of the work piece. These alumina based ceramic cutting tool materials produce good surface finish in the machining of hardened steel. In this paper an attempt is made to analyse the important wear mechanisms like abrasive wear, adhesive wear and diffusion wear of these ceramic cutting tool materials and the performance of these ceramic cutting tools related to the surface finish is also discussed here.

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.

A novel approach to quantifying tool wear and tool life measurements for optimal tool management

It is a common practice in batch production to continually use the same tool to machine different parts, using disparate machining parameters. In such an environment, the optimal points at which tools have to be changed, while achieving minimum production cost and maximum production rate within the surface roughness specifications, have not been adequately studied. The tool wear index (TWI) and the tool life model developed in this study use a novel approach, analyzing wear surface areas and material loss from the tool using micro-optics and image processing/analysis algorithms. With relation to surface roughness, the TWI measures the wear conditions more accurately and comprehensively, and the tool life model enables maximum use of a worn tool and minimum risk for in-process tool failure. The TWI and a surface roughness control model are integrated into an optimal control strategy that shows potential for productivity improvement and reduction of manufacturing cost.

Intelligent Recognition of End Milling Conditions Based on Cutting Force Model (Development of Monitoring Method without Any Databases)

An intelligent method is proposed to recognize various end milling conditions by comparing simulated and measured cutting forces. Static stiffness of the mechanical structure is identified by utilizing the measured cutting forces, and it is shown that the static deformation of the structure can be taken into account for accurate calculation of uncut chip thickness in the end milling process. A cutting force equation is developed with considering cutting edge roundness, i.e. tool wear, and a milling force model is constructed. Various parameters in the model are identified so that the simulated forces fit best with the measured forces. Edge force component, tool setting angle, specific cutting force resistance, etc. are identified or recognized as the model parameters, which contain rich information about the end milling process. End milling experiments are carried out at various stages of tool wear, and the results show that the proposed index for the tool wear, i.e. the identified edge force component divided by the specific cutting force resistance, has good correlation with the measured tool wear. It is expected that the end milling conditions such as the tool wear, the static stiffness of the structure, the tool setting angle and the specific cutting force resistance can be recognized intelligently without any data bases by the present method.

Tool wear measuring technique on the machine using CCD and exclusive jig

Recently the applications of high speed machining have increased due to the need for high precision and high accuracy machining and machining of difficult-to-cut material. However, the high speed machining also accompanies problems: the product quality can be degraded due to the tool wear and the product cost can be increased due to frequent tool replacements. Therefore, it is necessary to develop a technique of quantitative tool wear measurement to determine the precise timing for tool replacement. In this respect, this study suggests a reliable technique for the reduction of error components by developing a system using a CCD camera and an exclusive jig to be able to precisely measure the size of tool wear in a direct manner, in addition to partly introducing Taguchi method.

The performance of coated tungsten carbide drills when machining carbon fibre-reinforced epoxy composite materials

This paper is concerned with the effect of coatings on the performance of tungsten carbide (WC) drills in the drilling of carbon fibre-reinforced epoxy. Although composites are becoming increasing popular, there is a deficit in the existing knowledge of drilling composites, and in particular carbon fibre-reinforced epoxy resins. Two coated drills, namely titanium nitride (TiN)-coated and diamond-like carbon (DLC)-coated drills, were investigated and for comparative purposes an uncoated drill. The testing involved drilling a series of consecutive holes. During these tests the thrust forces and torques were monitored, following which the tool was inspected for flank wear and the workpiece inspected for damage in terms of hole tolerance, delamination and spalling. For all three tool types (uncoated, TiN coated and DLC coated), only a small number of drilled holes were found to satisfy an H8 tolerance criterion. An investigation of the hole diameter through the thickness of the composite revealed that it was the outermost plies that caused the hole to fail this tolerance criterion. The effect of tool wear caused the measured thrust forces and torques to increase over the life of the tool. While the degree of measured tool wear was small by comparison with that associated with drilling conventional materials, the effects were found to result in unacceptable damage to the composite. The damage was apparent in the form of spalling, chip-out and matrix cracking. The coatings were not found to reduce either tool wear or damage to the composite.

An empirical survey on the influence of machining parameters on tool wear in diamond turning of large single-crystal silicon optics

We conducted a series of screening experiments to survey the influence of machining parameters on tool wear during ductile regime diamond turning of large single-crystal silicon optics. The machining parameters under investigation were depth-of-cut, feed rate, surface cutting speed, tool radius, tool rake angle and side rake angle, and cutting fluid. Using an experimental design technique, we selected twenty-two screening experiments. For each experiment we measured tool wear by tracing the tool edge with an air bearing linear variable differential transformer before and after cutting and recording the amount of tool edge recession. Using statistical tools, we determined the significance of each cutting parameter within the parameter space investigated. We found that track length, chip size, tool rake angle and surface cutting speed significantly affect tool wear, while cutting fluid and side rake angle do not significantly affect tool wear within the ranges tested. The track length, or machining distance, is the single most influential characteristic that causes tool wear. For a fixed part area, a decrease in track length corresponds to an increase in feed rate. Less tool wear occurred on experiments with negative rake angle tools, larger chip sizes and higher surface velocities. The next step in this research is to perform more experiments in this region to develop a predictive model that can be used to select cutting parameters that minimize tool wear.

Tool wear evaluation by stereo vision and prediction by artificial neural network

The main objective of this work is to develop a method to study the contour of crater wear and measure it in three dimensions. A new technique for the measurement and visualization of tool wear has been presented in this paper. This method provides visualization of the tool wear geometry using a pair of stereo images. In addition, prediction of tool wear using artificial neural network is presented. A multilayered perceptron with back-propagation algorithm has been used for tool wear estimation, which could be trained using much less data than that is required in a normal mathematical simulation. Speed, feed, depth of cut and cutting time were used as input parameters and flank wear width and crater wear depth were output parameters. Training and testing of the network were carried out and the results are presented and analyzed in this work.

Correlation of cutting force features with tool wear in a metal turning operation

Interrupted turning has been conducted and the cutting forces recorded on-line while measurements of the cutting tool wear forms were made. The acquired data were analysed in the time and frequency domain for cutting tool wear correlation. The method employed was geared towards developing an understanding of the spectra energy content of the dynamic cutting force signals and how it could be used as an input sensor signal in the development of a tool wear monitoring system. Analysis of the data indicated that the spectra energy content correlated well with the measured tool wear at certain frequencies.

Crater wear mechanisms of tin coated high speed steel tools

This paper examines the crater wear characteristics of TiN coated high speed steel tool inserts during dry turning of steel workpieces over a wide range of machining conditions. Scanning electron microscopy shows that cracking and attrition of the TiN coating on the rake face result in coating loss soon after machining begins. The subsequent wear of the exposed high speed steel substrate occurs via attrition, diffusion, and high temperature shear. A wear mechanism map linking the observed crater wear mechanisms to machining conditions reveals that transitions from one dominant mechanism to another may be related to variations in measured tool wear rates.

Tool wear measurement in turning using force ratio

The aim of this work was to develop a reliable method to predict flank wear during the turning process. The present work developed a mathematical model for on-line monitoring of tool wear in a turning process. Force signals are highly sensitive carriers of information about the machining process and, hence, they are the best alternatives for monitoring tool wear. In the present work, determination of tool wear has been achieved by using force signals. The relationship between flank wear and the ratio of force components was established on the basis of data obtained from a series of experiments. Measurement of the ratio between the feed force and the cutting force components ( F f/ F c) has been found to provide a practical method for an in-process approach to the quantification of tool wear. A series of experiments was conducted to study the effects of tool wear as well as other cutting parameters on the cutting force signals, and to establish a relationship between the force signals, tool wear and other cutting parameters. The flank wear and the ratio of forces at different working conditions were collected experimentally to develop a mathematical model for predicting flank wear. The model was verified by comparing the experimental values with the predicted values. The relationship was then used for determination of tool flank wear.

A predictive mapping system for tool wear in metal cutting

Abstract In this paper, a new approach to generate wear maps representing the rates of tool wear in a two-dimensional space defined by the machining conditions in metal cutting is presented. This is to be done through theoretical modelling and simulation of the cutting processes. The predicted rates of tool wear are then used to generate the wear maps. This approach aims to establish a predictive mapping system for tool wear under a range of machining conditions. It is also intended to integrate a simulation system for metal cutting into this mapping system for tool wear prediction. As a first step in the development of this predictive mapping system, a theoretical tool wear model is modified for the prediction of the rate of tool flank wear in terms of tool and workpiece material properties, tool geometry and cutting conditions for uncoated tungsten carbide tools in the cutting of steels. The predicted wear rates are then presented in the form of a wear map. Comparisons between the wear maps generated by this approach and those obtained experimentally show good agreement in the trends of wear-rate variation against machining conditions. It is noted that further work is necessary to refine the theoretical models to improve the agreement between predictions and the actual measurements of tool wear. However, the good match in terms of wear-rate trends obtained presently suggests that this is a viable approach to achieve the objective of developing an integrated predictive system for tool wear in metal cutting.

Wear of TiC-coated carbide tools in dry turning

This paper examines the flank and crater wear characteristics of titanium carbide (TiC)-coated cemented carbide tool inserts during dry turning of steel workpieces. A brief review of tool wear mechanisms is presented together with new evidence showing that wear of the TiC layer on both flank and rake faces is dominated by discrete plastic deformation, which causes the coating to be worn through to the underlying carbide substrate when machining at high cutting speeds and feed rates. Wear also occurs as a result of abrasion, as well as cracking and attrition, with the latter leading to the wearing through of the coating on the rake face under low speed conditions. When moderate speeds and feeds are used, the coating remains intact throughout the duration of testing. Wear mechanism maps linking the observed wear mechanisms to machining conditions are presented for the first time. These maps demonstrate clearly that transitions from one dominant wear mechanism to another may be related to variations in measured tool wear rates. Comparisons of the present wear maps with similar maps for uncoated carbide tools show that TiC coatings dramatically expand the range of machining conditions under which acceptable rates of tool wear might be experienced. However, the extent of improvement brought about by the coatings depends strongly on the cutting conditions, with the greatest benefits being seen at higher cutting speeds and feed rates.

The influence of working parameters on the response of a capacitive sensor used in-process for the measurement of tool wear

In a previous research work, a no contact capacitive sensor was obtained which could check superficial characteristics of workpieces during working. This sensor can relate variations of capacity to superficial finishing of the workpiece directly. The present study aims at finding a method for interfacing the capacitive sensor to a system of data acquisition and for deciding the substitution of the tool, automatically. It has been necessary to value the influence of cutting parameters on sensor's response in order to find the threshold value, characterizing by itself an anomalous working state owed to regular or irregular tool wear.