Tool Wear Progression Research Articles

Experimental studies on the performance of multilayer coated carbide tool in hard turning of high strength low alloy steel

Abstract

Investigation on the influence of tool wear upon chip morphology in end milling titanium alloy Ti6Al4V

Titanium alloys are widely utilized in aerospace, automotive, biomedical and chemical engineering, etc., thanks to their excellent combination of high-specific strength, fracture, corrosion resistance characteristics, etc. However, titanium alloys are difficult-to-machine materials. Tool wear is one of the bottlenecks restricting their machining efficiency. A systematic study on the relationships among tool wear, chip morphology, and cutting vibration is inadequate. In this study, chip morphology and cutting vibration characteristics under different tool wear stages are examined using optical microscope, SEM, and vibration test system. The mechanism of tool wear in end milling titanium alloy is also investigated. Results indicate that with the progression of tool wear, the chip segment degree becomes more and more serious. The mechanism for this phenomenon is probed. Tool wear progression enlarges the cutting vibration which causes the friction force on tool/chip interfaces to increase, and this aggravates chip edge wear accordingly. On the contrary, the increase of chip segment degree induces the progression of cutting vibration and tool wear. Therefore, the aim of the present research is to investigate the sophisticated relationship. This will benefit for improving cutting efficiency and guaranteeing machining quality in end milling titanium alloy.

Relationships of tool wear characteristics to cutting mechanics, chip formation, and surface quality in ultra-precision fly cutting

Although the occurrence of tool wear can affect cutting forces, cutting chip morphologies, and machined surface quality in ultra-precision fly cutting (UPFC), there has been no research in this area due to the complex cutting mechanism of UPFC. The theoretical and experimental research described in this paper was therefore conducted to explore tool wear characteristics in UPFC and their relationship to cutting forces, cutting chip morphologies, and machined surface quality. Results from the study reveal that tool wear characteristics in UPFC include cutting edge fractures, workpiece material welding, wear land formation, sub-wear land formation, and micro-grooves. The cutting edge fractures lead to the formation of ridges on both the cutting chips and machined surface; the material welding increases the thrust force, crushes cutting chips, and deteriorates the machined surface quality; and the formation of wear land on the cutting edge makes the machined surface burred and fuzzy, and the micro-grooves leave some traces on the machined surface. By analyzing the captured cutting force, it is found that the progress of tool wear in UPFC can increase the cutting force and its power spectral density at the natural frequency of the dynamometer. Findings from the research provide rich insight into the relationships of tool wear characteristics to cutting forces, chip formation, and machined surface quality in intermittent cutting processes.

Development of an <i>In Situ</i> Tool Wear Monitoring System Using the Cutting Sound

This paper discusses the development of an in-situ, real-time tool wear monitoring system using the cutting sound that occurs during machining. In this study, the turning of carbon steel was implemented to examine the relationship between tool wear and the waveform of the cutting sound. Characteristic waveforms were extracted by fast Fourier transform (FFT) analysis of the cutting sound. The results indicated that the sound pressure of a specific frequency range increased during the progress of cutting-tool wear. In addition, it was possible to monitor the progress of tool wear by measuring the spectrum of a specific frequency range, even if the shape of the tool rest and the shapes of the work material were different, under certain cutting conditions.

1703 Sensor-less Cutting Torque Monitoring for a High Speed Spindle Applying Disturbance Observer

High speed milling is a practically feasible operation to improve the cutting accuracy and efficiency. On the other hand, large heat generation and progress of tool wear are serious problems. In order to modify the cutting condition properly, the machining state should be evaluated according to the process information such as cutting torque. This paper presents sensor-less cutting torque estimation method for a high speed spindle with hall sensors, applying disturbance observer. Instantaneous speed observer and interpolation method are employed to estimate the cutting torque with high accuracy. The validity of the presented method is verified through a time-domain simulation, and the feasibility is experimentally evaluated by comparing the proposed estimation and measurement with a torque dynamometer.

Increasing Cutting Tool Efficiency When Machining Regulatory Spindles Made from Ion Nitrided Nimonic 901 for Steam Turbine Valves

This article deals with issues during production of nimonic spindles used for controlling the volume of steam in the valves of steam turbines. With more extreme operating conditions in the power plant block with ultra-super-critical parameters of steam, the production of a conventional steel spindle is not suitable. This article describes machining technology for nickel alloy Nimonic 901. Ceramic or carbide cutting tools were used for the machining process. The text deals with progress of tool wear of the cutting edge. It describes the machining process to reduce tool wear during cutting. The second part of the report describes the process of ion nitriding nimonic spindles. The main aim was to get the best sliding properties on the surface of the spindle. The experiments confirmed the correctness of the solution. After nitriding several tests were performed, for example progress of microhardness of the nitrided layer and analysis of track wear after pin on disc test.

Cutting Tool Crater Wear Measurement in Turning Using Chip Geometry and Genetic Programming

Tool wear prediction plays an important role in industry automation for higher productivity and acceptable product quality. Therefore, in order to increase the productivity of turning process, various researches have been made recently for tool wear estimation and classification in turning process. Chip form is one of the most important factors commonly considered in evaluating the performance of machining process. On account of the effect of the progressive tool wear on the shape and geometrical features of produced chip, it is possible to predict some measurable machining outputs such as crater wear. According to experimentally performed researches, cutting speed and cutting time are two extremely effective parameters which contribute to the development of the crater wear on the tool rake face. As a result, these parameters will change the chip radius and geometry. This paper presents the development of the genetic equation for the tool wear using occurred changes in chip radius in turning process. The development of the equation combines different methods and technologies like evolutionary methods, manufacturing technology, measuring and control technology with the adequate hardware and software support. The results obtained from genetic equation and experiments showed that obtained genetic equations are correlated well with the experimental data. Furthermore, it can be used for tool wear estimation during cutting process and because of its parametric form, genetic equation enables us to analyze the effect of input parameters on the crater wear parameters.

Prognosis of the probability of failure in tool condition monitoring application-a time series based approach

Tool condition monitoring (TCM) system serves as the link between the cutting tool condition and the maintenance decision. The recent prognostic system employs highly complex models, which might need long calculation time. This long calculation time is acceptable for machine health prognostics, as machines’ maintenance interval is in the unit of month. However, a cutting tool’s life varies between minutes to hours. The calculation time might be critical to achieve a valid prognosis. In this paper, a novel prognostic system is proposed for TCM prognostics. This system consists of two parts: (1) online cutting force prediction part and (2) tool wear estimation part. The first part predicts the future cutting force segmentation by projecting the embedded historical cutting force with function approximation methods. Three function approximation methods are compared in the aspect of prediction error and calculation time. It is found that the Saucer’s local linear model could achieve the lowest prediction error (4.71 %) and calculation time (2.717 s) compared with global linear model and nonlinear model. The second part estimates the tool wear by inputting the predicted cutting force to a Bayesian-multilayer perceptron. It is found that this system can trace the progress of tool wear accurately (95 % successful rate has been achieved). Moreover, good generalization for different cutting conditions is also achieved.

English

The objective of this study is to develop a better understanding of the effects of spindle speed, cutting feed rate and depth of cut on the surface roughness and to build a suitable mathematical model. Such an understanding can provide insight into the problems of controlling the finish of machined surfaces when the process parameters are adjusted to obtain a certain responses like surface finish and power consumption. Also, the demand for high quality and fully automated production focuses attention on the surface condition of the product, especially the roughness of the machined surface, because of its effect on product appearance, function, and reliability. For these reasons it is important to maintain consistent tolerances and surface finish. Also, the quality of the machined surface is useful in diagnosing the stability of the machining process, power consumption, MRR, progressive tool wear, cutting tool chatter, etc.

Cutting Force Evolution and its Power Spectrum Analysis with Tool Wear Progress in Ultra-Precision Raster Milling

In this paper, cutting force and its power spectrum analysis at different tool wear levels are explored. A dynamic model is established to simulate the measured cutting force compositions, and a series of cutting experiments have been conducted to investigate the cutting force evolution with the tool wear progress. Research results reveal that in the time domain, the cutting force in UPRM is characterized as a force pulse follows by a damped vibration signals, the vibration can be modeled by a second order impulse response of the measurement system. While in the frequency domain, it is found that the power spectrum density at the natural frequency of dynamometer increases with the progress of tool wear, which therefore can be utilized to monitor diamond tool wear in UPRM.

Progressive tool-wear in machining of room-temperature austenitic NiTi alloys: The influence of cooling/lubricating, melting, and heat treatment conditions

This study investigates the effects of fabrication (vacuum arc remelting (VAR) melted vs. vacuum induction melting combined with VAR (VIM+VAR)), processing (hot rolled+fully annealed vs. cold worked+superelastic anneal) and machining conditions (dry, cryogenic, and minimum quantity lubrication (MQL)) of NiTi alloys on their progressive tool-wear behavior. Experimental findings reveal that cryogenic machining substantially improves the performance of cutting tools by reducing the progressive tool-wear in machining of the room-temperature austenitic NiTi alloys. Therefore, cryogenic machining could result in improved productivity and reduced manufacturing costs compared to dry and MQL machining. Experimental evidence suggests that cold working did not alter the progressive tool-wear substantially; however, the presence of carbide inclusions increased the progressive tool-wear in machining NiTi. Surface quality of machined samples under cryogenic machining presents promising improvement upon short-duration machining compared to dry and MQL machining, but all three techniques resulted in comparable quality after 4min of machining.

Research on Tool Wear of PCD Micro End Mill in Machining of ZrO<sub>2</sub> Ceramics

This paper presents a study on the tool wear of micro PCD end mill when machining ZrO2 ceramics. The cutting tool used was a self-designed PCD micro end mill with 1 mm in diameter and single flute. Experiments were conducted on a self-developed micro-milling machine tool. The tool wear characters and progress during the groove milling has been observed. The cutting force and machining accuracy of the grooves also have been studied. Based on the results, it is found that tool wear is mainly on the bottom surface; the cutting force increases with the progress of tool wear; tool wear also affect the width of machined grooves due to the decrease of effective tool diameter.

Determination of friction in metal cutting with tool wear and flank face effects

This paper studies friction for oblique cutting when using turning chamfered Si3N4 ceramic tools with a large negative rake angle. In particular, friction on the flank face is incorporated in the tribological balance. The values of force components recorded during tool wear tests at different cutting speeds were used as input data. The usual force components were transformed into the tool-in-use coordinate system to enable computing the friction and normal forces acting on the rake and flank faces and finally the relevant friction coefficients. It was revealed that both friction coefficients change substantially during tool wear progression and differ from those determined for orthogonal friction model. The new friction model was tested for the machining of spheroidal cast iron (SCI) using coated nitride ceramic inserts and additionally validated by cylinder-on-disc tribo-testing.

Monitoring the tool wear, surface roughness and chip formation occurrences using multiple sensors in turning

Tool wear, chip formation and surface roughness of workpiece under different cutting conditions have been investigated in machining using acoustic emission (AE) and vibration signature in turning. The investigation has shown that the AE and vibration components can effectively respond to the different occurrences in turning including tool wear and surface roughness. The AE has shown a very significant response to the tool wear progression whereas the resultant vibration (V) represented the surface roughness in turning. The vibration components Vx, Vy and Vz described the chip formation type and are found to have the most significant response to the change of feed, depth of cut and cutting speed respectively. The amplitude of vibration components, Vx, Vy and Vz increased with the increase of feed rate, depth of cut and cutting speed respectively. Even though the frequency of different signal components fluctuated at the different stages of tool wear and at different cutting conditions, the frequency of vibration components was always within a band of 98–40kHz, and the AE has varied between 51kHz and 620kHz.

Cutting forces and tool failure in high-speed milling of titanium alloy TC21 with coated carbide tools

TC21 alloy is a new alpha–beta damage tolerance titanium alloy with high strength and high toughness. Little work has been done in the field of machinability analysis since this alloy was developed. The cutting forces and tool wear in high-speed milling of TC21 alloy with physical vapor deposition ((Ti, Al)N-TiN)-coated carbide tools under different cutting conditions were investigated in this article. The results showed that the cutting force component Fx was more dominant of the three components, and the cutting forces presented an increasing trend with the tool wear progress, which in turn deteriorated the cutting condition and accelerated the tool failure progress. The major tool wear modes in high-speed side-milling TC21 alloy with coated carbide were adhesion and chipping on the rake face along with chipping and transverse crack on the flank face. Moreover, there was obvious nose depression from both the rake face and the flank face. Chipping along the flank and rake faces was identified as the main factor responsible for the failure of the coated carbide tools during the milling of titanium alloy TC21.

Evaluation of machining performance in cryogenic machining of Inconel 718 and comparison with dry and MQL machining

There has been significant work on establishing relationships between machining performance and the cutting parameters for various work materials. Recent trends in machining research show that major efforts are being made to understand the impact of various cooling/lubrication methods on machining performance and surface integrity characteristics, all aimed at improving process and product performance. This study presents the experimental results of cryogenic machining of Inconel 718, a high-temperature aerospace alloy, and comparison of its performance in dry and minimum quantity lubrication machining. Experimental data on force components, progressive tool wear parameters such as flank wear, notch wear, crater wear, cutting temperature, chip morphology, and surface roughness/topography of machined samples are presented. New findings show that cryogenic machining is a promising research direction for machining of high-temperature aerospace alloy, Inconel 718, as it offers improved machining performance in terms of reduced tool wear, temperature, and improved surface quality. It was also found that the number of nozzles in cryogenic machining plays a vital role in controlling cutting forces and power consumption in cryogenic machining of Inconel 718.

FRICTION MODELLING IN METAL CUTTING WITH INTEGRATED TOOL WEAR EFFECTS

S u m m a r y In this paper, friction in longitudinal turning operations when using chamfered uncoated ceramic tools is investigated. Both tool-chip and workpiece-tool interactions are integrated in the friction model. The values of three force components were consequently measured during tool wear tests at different cutting speeds they were used as input data for computing the friction and normal forces acting on the rake and flank faces and, as a result, for determining the relevant friction coefficients. It was observed that both friction coefficients are sensitive to tool wear progression depending on the cutting speed used. For comparison the values of friction coefficient were determined for orthogonal (2D) friction model. The 3D friction model was tested for the machining of spheroidal cast iron (SCI) using uncoated nitride ceramic inserts.

I-Kaz<sup>TM</sup>-Based Analysis of Cutting Force Signals for Tool Condition Monitoring in Turning Process

Cutting force is an important signal in machining process and has been widely used for tool condition monitoring. Monitoring the condition of the cutting tool in the machining process is very important to maintain the machined surface quality and consequently reduce inspection costs and increase productivity. This paper utilizes I-kaz-based analysis of cutting force signal to monitor the status of tool wear. The cutting force signals are measured by two channels of strain gauge that were mounted on the surface of tool holder. Experiments were carried out by turning hardened carbon steel and cutting force signals were analyzed using I-kazTM technique by integrating two component of signals (I-kaz 2D, Z2), I-kaz of cutting force (Z of Fy), and I-kaz of feed force (Z of Fx). The results show that I-kaz of feed force can be effectively used to monitor tool wear progression during turning operation.

Microscale Drilling of Bulk Metallic Glass

The microscale drilling performance of a Zr-based bulk metallic glass (BMG) is investigated in this paper. Crystallization, drill temperature, axial force, spindle load (SL), acoustic emissions (AE), chip morphology, hole diameter, and entry burr height are measured and analyzed with varying cutting speed and chip load. The progression of tool wear is assessed using stereo-microscopy techniques. At small chip loads, minimum chip thickness (MCT) is observed to shift cutting mechanics from a shear-dominated to a ploughing-dominated regime. Consequently, evidence of drill instability and larger burr height are observed. As drilling temperatures rise above the glass transition temperature, the BMG thermally softens due to the transition to a super-cooled liquid state and begins to exhibit viscous characteristics. In the tool wear study using tungsten carbide microdrills, rake wear is found to dominate compared to flank wear. This is attributed to a combination of a high rate of diffusion wear on the rake face as well as lower abrasion on the flank due to the decreased hardness from thermal softening-induced viscous flow of BMG.

Surface Roughness Modeling and Prediction by ANN when Drilling Udimet 720

Article deals with design of artificial neural network (ANN) for prediction of the surface roughness as one of the important indicators of machined surface quality. Back propagation neural network was trained and tested for prediction of the machined surface roughness. Cutting conditions, selected monitoring indices and tool wear parameter were given as inputs to the ANN. Test sample was nickel based super alloy Udimet 720, which is used as material for highly stressed jet engine components. Experimental data collected from tests were used as input into ANN to identify the sensitivity among cutting conditions, monitoring indices and progressive tool wear and machined surface roughness.