Modeling of tool wear during hard turning with self-propelled rotary tools

In this paper, an attempt is made to evaluate the self-propelled rotary carbide tool performance during machining hardened steel. Although several models were developed and used to evaluate the tool wear in conventional tools, there were no attempts in open literature for modeling the progress of tool wear when using the self-propelled rotary tools. Flank wear model for self-propelled rotary cutting tools is developed based on the work-tool geometric interaction and the empirical function. A set of cutting tests were carried out on the AISI 4340 steel with hardness of 54–56 HRC under different cutting speeds and feeds. The progress of tool wear was recorded under different interval of time. A genetic algorithm was developed to identify the constants in the proposed model. The comparison of measured and predicted flank wear showed that the developed model is capable of predicting the rate of rotary tool flank wear progression.     

Cutting force and diamond tool wear in stone machining

Stone machining by diamond tool is a widespread process to manufacture both standard products, such as tiles, slabs, kerbs, and so on, and design shapes. Cutting force and energy may be used to monitor stone machining. Empirical models are required to guide the selection of cutting conditions. In this paper, the effects of cutting conditions on cutting force and cutting energy are related to the shape of the idealized chip thickness. These effects are put into relationship with the diamond tool wear too. The empirical models developed in this paper can be used to predict the variation of the cutting energy. Therefore these models can be used to guide the selection of cutting conditions and to predict when it is needed to change the tool. The chip generation and removal process has been quantified with the intention of assisting both the toolmaker and the stonemason in optimizing the tool composition and cutting process parameters, respectively.     

The effects of progressive tool wear and tool restricted contact on chip breakability in machining

Chip breakability plays an essential role in automated machining systems. This paper presents an experimental investigation of the effects of progressive tool wear and the resulting formation of the tool restricted contact on chip breakability in a turning operation. Six parameters of tool wear, namely, major flank wear (VB), crater wear depth (KT), crater wear length (KK), crater wear width (KB), wear retract of cutting edge (KS) and nose wear (N), are shown to contribute to the variations of chip breakability with tool wear progression. The results show that the chip breakability varies significantly with tool wear progression, especially with the combined crater and flank wear progression, and contributes to the development of a restricted rake face land, making the tool behave like a restricted contact grooved tool. The chip curling and breaking action is largely influenced by the nature and magnitude of the restricted contact and the groove profile being developed on the tool face. The results presented in this paper are also intended to provide guidelines for designing effective chip grooves on the tool face.     

Effects of cutting fluid application on tool wear in machining: Interactions with tool-coatings and tool surface features

Minimal Quantity of Lubricant (MQL) application of cutting fluids (CFs), or near-dry machining, is being proposed as an environmentally and economically viable alternative to conventional flooding under conditions where dry cutting is not feasible. However, several issues related to CF application effects on cutting tool wear need further clarification, especially, the interactions of CF application with tool-coatings and chip-breakers, both of which are widely employed in industrial cutting tools, need further study. This paper presents the results of an experimental study into the effects of different CF application methods on tool wear during machining of AISI 1045 steel using flat-faced and grooved, coated carbide cutting tools. The results provide insight into the mechanisms of tool wear in the presence of CFs, as well as the influence of chip-breaking geometric features, and tool-coating systems, on CF action. The wear mode was observed to be dictated by thermal considerations, rather than by any friction reduction capability of different CF application methods, and forced attempts at achieving lubricating action were negatively affecting tool life under some conditions.     

Cutting forces and wear in dry machining of Inconel 718 with coated carbide tools

In the machining of heat resistant super alloys used in aeronautical applications and classified as difficult-to-machine materials, the consumption of cooling lubricant during the machining operations is very important. The associated costs of coolant acquisition, use, disposal and washing the machined components are significant, up to four times the cost of consumable tooling used in the cutting operations. To reduce the costs of production and to make the processes environmentally safe, the goal of the aeronautical manufacturers is to move toward dry cutting by eliminating or minimising cutting fluids. This goal can be achieved by using coated carbide tools at high cutting speeds. To achieve this goal, different coated tools and different cutting conditions were tested in dry conditions. The elementary orthogonal cutting process was chosen, the cutting and feed cutting forces components were measured and the cutting force ratio calculated. This ratio is shown to be as an interesting indicator of tool wear. The tool wear mechanisms tool were analysed by using white light interferometer and scanning electron microscopy coupled to an energy-dispersive X-ray spectroscopy EDS-system. The EDS was very useful to analyse the elements deposited on the cutting tool faces. The ability of the different coatings to increase the carbide tool performance were analysed, the main wear modes were depicted. An optimisation of the cutting conditions was finally proposed and the efficiency of the coatings was shown. The results coming from uncoated tools were compared with those obtained with coated tools under the same conditions of machining. At the end, a choice of coatings is proposed and an extension of this study to an industrial machining operation is presented for future developments.     

Performance enhancement of cryogenic machining and its effect on tool wear during turning of Al-Ticp composites

The current research is to focus on developing a liquid nitrogen diffusion system to optimize the usage of liquid nitrogen and maximizing cooling and lubrication capability by effective penetration. An atomized liquid nitrogen spray system was developed to diffuse liquid nitrogen effectively at a low flow rate (10–12 L/h) and as a high velocity (8–50 m/s) droplet jet to the machining zone. Using coated carbide tool with varying tool geometry (rake angle, approach angle, and nose radius), an investigation was performed to study the role of atomized liquid nitrogen spray-assisted machining, on performance of tool and surface quality of the machined workpiece during turning of Al-TiCp composite. To analyze the performance of liquid nitrogen spray-assisted machining, various experiments were conducted. The results obtained from the experiments reveal that the effective use of atomized liquid nitrogen spray machining is a feasible alternative to dry, wet, and cryogenically chilled argon gas. This technique significantly reduces heat generation in machining zone. The study also emphasizes the influence of tool geometry on the machinability of Al-TiCp metal matrix composites.     

Investigations on model-based simulation of tool wear with carbide tools in milling operation

This paper deals with tool wear in milling operation using carbide tools. The main purpose of this work is to define a model-based procedure for forecasting tool-wear progression during cutting operation by using machining simulation. Firstly, a multi-axis machining simulation algorithm is proposed based on DEXEL model and local area update method. NC milling machining process simulation software NCToolWearSim is realized by using Visual C++ and OpenGL. The developed process simulation software is used to simulate the cutting process. Secondly, tool-wear simulation algorithm in the machining process is presented with tool-wear model and machining simulation algorithm and is implemented into the machining simulation software NCToolWearSim in order to evaluate the tool wear and to update the tool geometry. The tool-wear value is estimated according to the established tool-wear model from experienced tool-wear data. Thus, tool-wear progression can be visualized in milling operation by using NCToolWearSim. Finally, experimental tests, performed milling integral wheel with carbide tools, were used to calibrate and validate the correctness of tool-wear simulation process based on the tool-wear model.     

Employing preheating- and cooling-assisted technologies in machining of Inconel 718 with ceramic cutting tools: towards reducing tool wear and improving surface integrity

The International Journal of Advanced Manufacturing Technology - This paper is motivated by the fact that machining of Inconel 718 involves rapid tool wear and poor surface integrity. We...     

Experimental investigation of tool wear and machining rate in rotary ultrasonic machining of nickel alloy

Nickel alloys possess the excellent potential at high temperature and resistance to oxidation/corrosion owing to its high nickel content. These materials necessitate non-traditional machining methods. The rotary ultrasonic machining (RUM) process comes into existence as a superior alternative to the conventional machining of nickel alloys. The processing of these alloys using RUM needs attention. This article details the multi-response optimization in RUM of nickel alloy using the desirability concept. The present work is carried out with two shapes of the tool: (i) Plain tool and (ii) lateral slotted tool. During RUM, the process parameters—power rating tool rotation, abrasive diamond grit size and feed rate are varied. Compared with the plain tool, the lateral slotted tool shows the more efficient machining rate (MR) with less tool wear (TW). The micro-graphs disclose the mechanism of MR and TW during RUM.     

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.     

纯钒车削刀具磨损表面形态及机理研究

对金刚石刀具、涂层刀具及硬质合金刀具车削纯钒时刀具磨损形态及其磨损机理进行观察和分析.结果表明,在所选取条件下,不同刀具材料对工件材料切削时表现出的刀具磨损形态主要为前刀面磨损、后刀面磨损、微崩刃、剥落和粘结等.刀具的前刀面主要是沿切屑流出方向的沟槽形月牙洼磨损,而后刀面以粘结磨损为主.CD10刀具和H10非涂层刀具具有较佳的切削性能,而H13A非涂层刀具和GC1025涂层刀具不适于纯钒车削.     

The analysis of tool life and wear mechanisms in spindle speed variation machining

Regenerative chatter vibrations generally limit the achievable material removal rate in machining. The diffusion of spindle speed variation (SSV) as a chatter suppression strategy is mainly restricted to academy and research centers. A lack of knowledge concerning the effects of non-stationary machining is still limiting its use in real shop floors. This research is focused on the effects of spindle speed variation technique on tool duration and on wear mechanisms. No previous researches have been performed on this specific topic. Tool wear tests in turning were carried out following a factorial design: cutting speed and cutting speed modulation were the investigated factors. The carbide life was the observed process response. A statistical approach was used to analyze the effects of the factors on the tool life. Moreover, the analysis was extended to the wear mechanisms involved during both constant speed machining and SSV. The worn-out carbide surfaces were examined under a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. Significant differences were appreciated. It was observed that SSV tends to detach the coatings of the inserts, entailing a mechanism that is quite unusual in wet steel turning and thus fostering the wear of the tool. The performed analysis allowed to deduce that the intensified tool wear (in SSV cutting) is mainly due to thermo-mechanical fatigue.     

Cutting forces,tool wear and surface finish in high speed diamond machining

We have investigated the cutting forces, the tool wear and the surface finish obtained in high speed diamond turning and milling of OFHC copper, brass CuZn39Pb3, aluminum AlMg5, and electroless nickel. In face turning experiments with constant material removal rate the cutting forces were recorded as a function of cutting speed between v_c = 150 m/min and 4500 m/min revealing a transition to adiabatic shearing which is supported by FEM simulations of the cutting process. Fly-cutting experiments carried out at low (v_c = 380 m/min) and at high cutting speed (v_c = 3800 m/min) showed that the rate of abrasive wear of the cutting edge is significantly higher at ordinary cutting speed than at high cutting speed in contrast to the experience made in conventional machining. Furthermore, it was found that the rate of chemically induced tool wear in diamond milling of steel is decreasing with decreasing tool engagement time per revolution. High speed diamond machining may also yield an improved surface roughness which was confirmed by comparing the step heights at grain boundaries obtained in diamond milling of OFHC copper and brass CuZn39Pb3 at low (v_c = 100 m/min) and high cutting speed (v_c = 2000 m/min). Thus, high speed diamond machining offers several advantages, let alone a major reduction of machining time.     

The effect of machining parameters on tool electrode edge wear and machining performance in Electric Discharge Machining (EDM)

The main purpose of this study is to investigate the variation of tool electrode edge wear and machining performance outputs, namely, the machining rate (workpiece removal rate), tool wear rate and the relative wear, with the varying machining parameters (pulse time, discharge current and dielectric flushing pressure) in EDM die sinking. The edge wear profiles obtained are modeled by using the circular arcs, exponential and power functions. The variation of radii of the circular arcs with machining parameters is given. It is observed that the exponential function models the edge wear profiles of the electrodes very accurately. The variation of exponential model parameters with machining parameters is presented.     

卧式车床精度对加工质量的影响及其调整方法

机床故障可从其加工零件的缺陷来判定,从普通卧式车床常见加工零件故障出发,总结了几类常见的由于卧式车床精度引起的加工零件的故障缺陷,并且详细地介绍了这类车床精度的调整办法。     

The dependence of tool overhang on surface quality and tool wear in the turning process

In the turning process, the importance of machining parameter choice is increased, as it controls the surface quality required. Tool overhang is a cutting tool parameter that has not been investigated in as much detail as some of the better known ones. It is appropriate to keep the tool overhang as short as possible; however, a longer tool overhang may be required depending on the geometry of the workpiece and when using the hole-turning process in particular. In this study, we investigate the effects of changes in the tool overhang in the external turning process on both the surface quality of the workpiece and tool wear. For this purpose, we used workpieces of AISI 1050 material with diameters of 20, 30, and 40 mm; and the surface roughness of the workpiece and tool wear were determined through experiments using constant cutting speed and feed rates with different depth of cuts (DOCs) and tool overhangs. We observed that the effect of the DOC on the surface roughness is negligible, but tool overhang is more important. The deflection of the cutting tool increases with tool overhang. Two different analytical methods were compared to determine the dependence of tool deflection on the tool overhang. Also, the real tool deflection values were determined using a comparator. We observed that the tool deflection values were quite compatible with the tool deflection results obtained using the second analytical method.     

An investigation of heat partition and tool wear in hard turning of H13 tool steel with CBN cutting tools

This paper presents results of an investigation into the tool life and the tool wear behaviour of low content CBN cutting tools used in hard turning of hardened H13 tool steel. The approach followed here required both experimental work and finite element thermal modelling. The experiments involved measuring the cutting forces, cutting temperatures, tool wear, and the contact area. Using the measured cutting forces and the contact area in the orthogonal cutting model, we calculated the heat flux on the tool and applied it in the FE thermal analysis. The temperatures history from the analysis was matched with the experimental data to estimate the fraction of heat entering the tool for both conventional and high speeds. The heat partition into the tool was estimated to be around 21–22% for conventional speeds, whereas for high-speed turning, it was around 14%. The tool wear, however, was found to be dominated by chipping for both cutting speeds and could be reduced considerably by reducing the amount of heat entering the tool.     

Development of a tool wear observer model for online tool condition monitoring and control in machining nickel-based alloys

Online monitoring and in-process control improves machining quality and efficiency in the drive towards intelligent machining. It is particularly significant in machining difficult-to-machine materials like super alloys. This paper attempts to develop a tool wear observer model for flank wear monitoring in machining nickel-based alloys. The model can be implemented in an online tool wear monitoring system which predicts the actual state of tool wear in real time by measuring the cutting force variations. The correlation between the cutting force components and the flank wear width has been established through experimental studies. It was used in an observer model, which uses control theory to reconstruct the flank wear development from the cutting force signal obtained through online measurements. The monitoring method can be implemented as an outer feedback control loop in an adaptive machining system.