Showing papers on "Tool wear published in 1991"

In-process monitoring of tool wear in milling using cutting force signature

Abstract: This paper presents a new approach for on-line monitoring of flank wear in milling. This approach is based on the variations of the magnitude of cutting force harmonics with flank wear. It is shown first, using computer simulations, that the sensitivity of the magnitude of various harmonics in the cutting force spectrum to flank wear, varies depending on the immersion ratio and the number of teeth in the cutter. The results of the computer simulations were verified experimentally at various cutting conditions. An on-line monitoring strategy is then proposed which uses signature features selected from the harmonics of the cutting force signals. Incorporated in this strategy is a new method for the in-process identification of the immersion ratio.

Mechanical system monitoring using hidden Markov models

Abstract: A hidden Markov model (HMM)-based approach to mechanical system monitoring is presented. The resulting system is shown to be useful for machining applications with the associated problems of tool wear detection and prediction. The approach is based on continuous density, left-right HMMs that closely match the one-way, fresh-to-worn transition process of machining tools. The Baum-Welch iterative training procedure is modified to incorporate prior knowledge of the transitions between tool wear states. Results presented demonstrate that a multisensor HMM-based system is an effective approach for tool wear detection and prediction. >

Cryogenic machining of Kevlar composites

Abstract: Previous attempts to machine Kevlar aramid fibre reinforced plastics (KFRP) with conventional cutting tools have proven to be extremely difficult. This has somewhat restricted the material's usage, often negating the advantages of its high strength to weight ratio and fatigue tolerance. The present paper describes a novel technique of machining KFRP under cryogenic conditions with remarkable results compared to those obtained at ambient temperatures. The investigation carried out with turning operation shows dramatic improvement of the tool performance and surface quality. The effects of various machining parameters such as workpiece temperature, cutting speed and tool geometry on the machinability of KFRP are presented and analyzed. It appears that care is necessary to judge the tool life as the typical tool wear growth and surface finish or cutting force may produce contradictory results. It is also suggested that, for KFRP, surface finish of the machined workpiece is a very good criterion to d...

Flank Wear Estimation Under Varying Cutting Conditions

Abstract: A model-based methodology, designed to operate under varying cutting conditions, for on-line estimation of flank-wear rate based on cutting force measurements is introduced. The key idea is to employ a model of the relationship between force and flank wear, together with on-line parameter estimation methods. This permits separation of the direct effect of changing cutting conditions on force from the indirect effect where changing cutting conditions affect the wear which, in turn, affects the force. Simulation results confirm the effectiveness of this strategy for turning with varying speed, feed, or depth of cut. Experiments, conducted for turning operations with a varying depth of cut, show good agreement between estimated wear values and the actual values of tool wear measured intermittently during the cut.

Metal injection molded rotary metal cutting tool

Abstract: A rotary metal cutting tool for forming threads on the insides of a bore, drilling a bore or otherwise shaping a bore, which tool is fabricated from a metal injection molded blank of appropriate tool steel to provide improved tool wear. The tool, which may be a tap, includes a transverse stress relief ring for reliably localizing the point of tool failure under overstress conditions. A polygonal, e.g., hex, surface on the shank provides means for engaging the shank with an extraction tool to remove the broken remains of the tool from the bore after the tool fails. A conventional O-ring seal is installed in the stress relief ring to provide protection from flying metal particles upon failure.

Optimization of Turning Process by Cutting Force Measurement

Abstract: The needs of today's complex manufacturing systems requires the use of machine tools operated by means of an adaptively controlled system. Adaptive control provides continuous monitoring of performance and adjusts the system variables in order to approach the conditions optimum for the chosen performance objectives. This investigation proposes the in-process parameter estimation method of tool life in turning, in which the force ratio of feed force to tangential force due to the tool wear is detected. The method involves the analysis of the optimum cutting conditions based on the machining cost per unit volume of metal removed under the considered cutting constraints.

Detection of tool wear using multisensor readings defused by artificial neural network

Abstract: Real-time tool wear sensing is essential for machining process optimization and implementation of untended manufacturing systems. This paper proposes a tool wear model based on an artificial neural network (ANN), used as a pattern associator, that is trained using experimental data which consists of tool wear measurement and corresponding readings of a variety of sensors. During operation, the network is fed only with the sensors'' readings; it fuses this data and, according to the `model'' established during the training, provides an estimation for the tool wear. Discussion and experimental results are provided.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

On-line condition monitoring of tool wear in end milling using acoustic emission

Abstract: The monitoring of tool wear is important in maintaining the quality of workpieces produced. This paper presents a methodology to monitor on-line tool wear in end milling using acoustic emission. It is well known that the root-mean-square (RMS) value of the acoustic emission is directly proportional to the power expended in turning. A mathematical model has been developed to predict the RMS value of the acoustic-emission signal in milling. This mathematical model incorporates the machining parameters as variables. The accuracy of the model has been verified by a series of experiments. The experiments were carried out on a Bridgeport milling machine and data was collected and analysed by using an on-line computer data acquisition system. A comparison of the experimental and theoretical RMS values indicates a very good agreement between them. A control strategy similar to the moving average/moving range charts has been developed for monitoring on-line tool wear. The limits for the control charts were obtaine...

Acoustic Emission Monitoring of the Cutting Process—Negating the Influence of Varying Conditions

Abstract: Earlier work has shown tool failure monitoring using frequency-based pattern recognition analysis of acoustic emission signals to be feasible while machining under fixed cutting conditions. However, cutting conditions change quite frequently in industrial production, and since AE signals are affected by varying conditions, a model is developed based on Taylor’s expansion using experimental data obtained for various process variables and their output AE spectra, and is used to filter the influence of varying conditions on signal classification. The experimental study involved a fractional factorial experimental design which delineated effects of variables on AE generation during machining. Normalized AE spectra within the 100 to 1000 kHz range were used as system output along with the AE power. While the normalized spectra were found unaffected by changes in the depth of cut, the total AE power was also little affected by the mixed flank and crater wear, and feed rate changes. Using the model and filter designed, performance of the tool wear, chip noise and tool breakage classifier improved to 83, 99, and 97 percent classification, respectively.

Tool wear detector

Abstract: A tool wear detector is formed by applying a resistor, the resistance of which is permanently altered in accordance with a time/temperature relationship (and by change in size e.g. as a result of wear), to a tool in a manner so that the resistor and the portion of the tool to be monitored are subjected to corresponding temperatures cycles. Measuring the resistance of the resistor at any time provides an indication of the cutting conditions to which the monitored portion of the tool has been subjected and thereby an indication of the remaining life of the portion of the cutting edge of the tool being monitored.

Characteristics of Self-propelled Rotary Tools in Machining High-performance Materials.

Abstract: Machining of high-performance materials hitherto remains a major challenge in production. Cutting some of those materials by the self-propelled rotary tool is evaluated in this paper with respect to tool wear and tool life. Experimental results show that the rotary tool, characterized by the tangential motion of the circular cutting edge, enhances tool life far longer than the conventional one in turning a metal-matrix composite. Crater wear hardly occurs in rotary cutting of a titanium alloy and a high manganese steel. The inclination angle of the rotary tool is found to be an important factor which controls the relative motions between the tool and the work (chip), and hence tool wear.

Dynamic model for tool wear detection using acoustic emission

Abstract: Abstract In this paper we present a dynamic model that can be used for monitoring those processes that gradually deteriorate from an acceptable condition(process in control)to an unacceptable condition(process out of control).Monitoring of a cutting tool for detection of wear is an example of such a process, where a cutting tool is sharp until it becomes worn. The model is tested, using the spectral components of acoustic emission signals generated in an earlier work, the results are very promising.

Intelligent chip control and tool wear estimation in automated machining systems

Abstract: Chip control and tool wear estimation are two major concerns in automated machining systems. Chip control is essential for the safety of the machining operation, the maintenance of good surface finish on the machined part, the convenience of chip disposal, and possible power reduction; while tool wear estimation is vital to an effective tool change policy and quality control strategy, especially in finishmachining. This thesis first presents a new method for quantifying chip breaking and chip shapes with a fuzzy rating system, and further for predicting the chip breakability for arbitrary combinations of machining conditions through a fuzzy-set mathematical model. A predictive expert system for off-line assessment of machining performance, with chip control as a major criterion and due consideration to surface finish and power consumption, is then developed. A knowledge-based system for designing optimum chip breakers is set up with a criterion of efficient chip breaking at reduced power consumption. The method is based on the analysis of three-dimensional chip flow in oblique machining for a wide range of work materials, cutting conditions, tool geometries, chip breaker styles/sizes and restricted contact lengths. Experimental results of tool wear patterns in finish-machining show that estimation of more than one type of tool wear is required to assure the quality of a finished product. In order to achieve this, a dispersion analysis algorithm, derived from the established

Tool wear determn. from friction with dressing tool - is measured by one or more vibration parameters

Abstract: To determine wear caused on a rotating grinder tool (4), the worn tool is brought into contact with a dressing tool (8), and the extent and/or nature of the wear are expressed by one physical parameter related to the friction between the two tools. Possible parameters include the amplitude/frequency/intensity/speed/pressure amplitude of the resilient vibrations produced by the contact, the temp. produced in at least one tool by frictional heat, or the torque increase in at least one tool needed to maintain constant rotation speed. A wear profile is produced which relates to data measured over the axial width and/or profile of the grinder tool, based on sensed vibrations. The comparison unit employed incorporates data related to the value of a work-piece being ground. ADVANTAGE - Wear is simply and quickly measured.

Ultrasonic Waves Method for Tool Wear Sensing - In-process and Built-in Type

Abstract: With the advance of FCIMS (Flexibly Computerised-Integrated Manufacturing Structure), the in-process measurement becomes more important. In the flexible machining system, the major purpose of such an in-process measurement is to detect or to recognise the states of machining and also related environment. Of these, the measurements of the tool wear and failure are basically important; however, there are few measuring methods applicable to the actual machining environment, although having been carried out a lot of concerned research activities. In consideration of such situations of the present, this paper deals with a new proposal for detecting the tool wear. The proposed method utilizes the reflection characteristic of ultrasonic waves, instead of the reflected time, at the contact surface between the cutting edge of tool and the work. From the experimental results, it can be verified that the proposed method shows fairly good performances in the machining procedure without the cutting fluid.

In-process Monitoring of Machining Environment by Heat Flux Sensor. Sensing of Tool Wear.

Abstract: It has become very important to develop an in-process monitoring system for machining environment to materialize fully automated and unattended machining. Various monitoring systems have so far been proposed by different researchers. However, most of the systems are not yet effective for practical use except those of AE and piezoelectric types. A new in-process monitoring system for machining environment has, therefore, been proposed which is based on heat flux sensing. Heat flux can be expressed as a time derivative of temperature, thus, this is more sensitive to the variation of temperature. It can be expected that the sensing of heat flux is suitable for the recognition of the machining environment. In this paper, the in-process monitoring of the tool wear has been tried to estimate the potential of the proposed method. The results of actual cutting tests ascertain that the output signal of heat flux sensor is useful and effective for in-process monitoring of tool wear.

Consequence of Orientation on the Single Crystal Diamond Cutting Tool

Abstract: The single crystal diamond tools having various orientation are prepared in which the rake face is lapped to identify with the {100} and {110} plane respectively, and the direction of cutting edge is coincided with the direction coresponding to the max. or minimum values of the coefficient of friction. Cutting aluminum alloy by these diamond tools are examined from the view points of the cutting force and tool wear.

Drilling method by using laser beam

Abstract: PURPOSE:To prolong the life of a tool by making a hole with a drill as a material to be worked is irradiated with laser beam from the tip part of the drill through a hole which is opened in the tip center of the drill and penetrated along the central axis in the lengthwise direction of the drill CONSTITUTION:The laser beam 2 emitted from a laser oscillator 1 enters the hole 5 installed by an optical mirror 3 in the drill 4 of a machine tool The hole 5 is penetrated from the center of the tip of the drill 4 along the central axis in the lengthwise direction and the laser beam 2 passes through the hole 5 and irradiates the material 6 to be worked A part of the material 6 to be worked being a range of irradiation of the laser beam 2 is heated and melted This melted part is the central part of the hole made by the drill 4 and the position containing this melted part is worked by the drill 4 The force to work this melted part with the drill 4 is very small Thus, the tool wear is reduced and the tool life can be prolonged greatly in this part