Stock Removal Rate Research Articles

Electrical Discharge Machining of Super Alloys: A Review

In the current scenario, manufacturing industries faces difficulties during machining of engineering materials-metal based, having higher mechanical properties viz. higher strength, toughness and hardness through conventional machining methods. These problems include rapid tool wear, poor surface quality of work piece material and lower stock removal rate. EDM is a single prominent what more lucrative unconventional machining procedure is, finding its prevalent functions in motorized and aerospace industries for machining of harder materials that is super alloys. Super alloys are the heat-resistant category of metals maintaining their elevated potency at superior temperature. The present paper focuses on the past work done by the researchers on machining of super alloys viz. titanium, nickel and cobalt using EDM and Wire EDM process.

Safe optimization for feedrate scheduling of power-constrained milling processes by using Gaussian processes

To set up a rough milling process with a maximized stock removal rate, an optimal feedrate schedule has to be determined without violating a given spindle power constraint. A method is presented, to achieve this by adapting the values of the feedrate schedule iteratively with every production cycle, based on predictions of a Gaussian Process model, and is validated on a face milling process of grey cast iron (EN-GJL-300). The Gaussian Process model is trained with data, measured in previous production cycles, and is used to ensure satisfaction of the given spindle power constraint during the optimization procedure.

An investigation of additively manufactured coolant nozzles for cylindrical grinding applications and progression to high stock removal

This paper explores use of Additively Manufactured features in coolant nozzles for cylindrical grinding applications. In an external cylindrical grinding process, different stock removal rate regimes are trialed to assess printed nozzle features; 3D printed nozzles with special internal features are shown to generate an improvement in key surface roughness metrics (up to 0.3 µm Sa reduction in mean area surface roughness) and superior wheel condition in Q’ ≤ 2.61 mm2/s cylindrical plunge grinding applications. In addition, use of VIPER grinding principles achieved a stable cylindrical grind at Q’ = 20.47 mm2/s using a porous wheel and hook nozzle tooling.

FEATURES OF HIGH-SPEED THE SUPER-FINISHING DISCS CERAMIC

The possibility of providing high performance of super-finishing of ceramics based on the analysis of the processes of super-finishing of metal products is proved. For conducting experimental studies, a special installation has been developed, including a sharpening machine and a device for superfinishing. For such processing conditions, the necessity of using a low-rigidity technological system is justified. Discs made of ceramic materials of various machinability with diamond bars were super-finished at a cutting speed of up to 9.1 m/s and a clamping force of up to 90 N. Experimental data on the change in the value of cut allowance on the duration of treatment, the impact speed super-finishing of ceramic disks and grit sizes of diamond bars on the magnitude and rate of stock removal, roughness and waviness of machined surfaces and consumption of the tool. The results of super finishing of ceramic materials with processing of metal products are compared.

Dry grinding of gears for sustainable automotive transmission production

Gear production for automotive transmissions is a rapidly growing market as manufacturers adapt to increasingly more stringent automobile fuel-efficiency requirements. Grinding is the preferred choice for finishing of automotive gears thanks to its high productivity and capability of machining heat-treated parts with very high geometric accuracy and surface quality. Grinding remains, however, the only machining process still to use lubricant, with significant costs, health implications and environmental risks. This paper presents a novel technology for grinding of gears without the requirement for oil, while still achieving necessary quality and production targets. The feasibility of this new dry process is assessed by firstly identifying threshold grinding parameters (70m/s cutting speed; 0.4mm/rev axial feed rate; 82% and 18% stock removed via skiving and dry grinding respectively) for avoiding grinding burn, then optimizing cutting parameters to obtain the desired gear accuracy. Gear accuracy and process productivity are found to exhibit opposing dependencies on cutting speed, stock removal and feed rate, with optimization of parameters carried out to achieve current quality and throughput standards. A comparison between results obtained with state-of-the-art wet grinding and the new process confirms the effectiveness and feasibility of dry grinding.

Predictive Modelling and Analysis of Process Parameters on Material Removal Characteristics in Abrasive Belt Grinding Process

The surface finishing and stock removal of complicated geometries is the principal objective for grinding with compliant abrasive tools. To understand and achieve optimum material removal in a tertiary finishing process such as Abrasive Belt Grinding, it is essential to look in more detail at the process parameters/variables that affect the stock removal rate. The process variables involved in a belt grinding process include the grit and abrasive type of grinding belt, belt speed, contact wheel hardness, serration, and grinding force. Changing these process variables will affect the performance of the process. The literature survey on belt grinding shows certain limited understanding of material removal on the process variables. Experimental trials were conducted based on the Taguchi Method to evaluate the influence of individual and interactive process variables. Analysis of variance (ANOVA) was employed to investigate the belt grinding characteristics on material removal. This research work describes a systematic approach to optimise process parameters to achieve the desired stock removal in a compliant Abrasive Belt Grinding process. Experimental study showed that the removed material from a surface due to the belt grinding process has a non-linear relationship with the process variables. In this paper, the Adaptive Neuro-Fuzzy Inference System (ANFIS) model is used to determine material removal. Compared with the experimental results, the model accurately predicts the stock removal. With further verification of the empirical model, a better understanding of the grinding parameters involved in material removal, particularly the influence of the individual process variables and their interaction, can be obtained.

Effects of Jet Pressure on the Ground Surface Quality and CBN Wheel Wear in Grinding AISI 690 Nickel-Based Superalloy

Fluid application in grinding is getting attention as higher stock removal rates, higher surface integrity and longer wheel life are required. It is necessary to define proper conditions of application for meeting high productivity goals by lowering the specific grinding energy and reducing the temperature of the contact zone. The present study investigated the capacity of the jet pressure of a spot nozzle to improve the wear of a CBN wheel when grinding the AISI 690 superalloy. Grinding experiments were conducted with an emulsion-type cooling fluid delivered at pressure ranging from 0.1 to 4 MPa. Results show that the maximum stock removal, reached at 4 MPa, is 5 times the stock removal obtained at 0.1 MPa, while the grinding ratio at 4 MPa is 8 times that at 0.1 MPa, and there is a critical pressure (Pc) around 1.5 MPa corresponding to the minimum specific grinding energy. Scanning electron microscopy of the grain tips showed that the wear mechanism shifts from breaking and dislodgment at low jet pressure to micro-fracture resulting in continuous self-sharpening of the abrasive grains. By lubricating at jet pressure close to Pc, there is less thermal damage due to plowing and sliding and the resulting lower loading of the abrasive grains favors the micro-fracture of grains and thus a longer wheel life.

A grinding force model allowing for dulling of abrasive wheel cutting grains in plunge cylindrical grinding

A mathematical model is developed for the grinding force in cylindrical plunge grinding that allows for the grinding conditions, the size of the flank wear land areas formed on the grinding wheel cutting grains, the properties of the work material, and the geometrical parameters of the grinding tool and work surface. A formula is obtained for calculating the stock removal rate as a function of the degree of dulling (glazing) of the grinding wheel. The adequacy of the mathematical model of the grinding force in cylindrical plunge grinding is established.

高硬度材(SUJ2)の精密切削加工における工具摩耗特性

In manufacturing of difficult-to-cut materials such as SUJ2, for the purpose of reducing of a tool wear and improving a machining accuracy, the searching of machining conditions become an important issue. SUJ2 is high hardness (HRC60), so the cutting stock removal rate is low. Consequently, wet cutting is adopted for cutting difficult-to-cut materials. Wet cutting uses a large amount of cutting fluid，has excellent cooling effect of the tool, and frictional heat suppression effect, the chip decoupling effect is expected. These effects, has also been confirmed in the small finish turning the cut depth, it is utilized to the improvements and processing efficiency of the tool life．In this report, we experimentally examined the relationships between cutting condition, cutting speed, cutting continuation and tool wear characteristics.

Tool Wear Characteristics in Near-Dry Cutting of Ni-Based Superalloy

Recently, high-combustion-efficiency jet engines have become required in the aircraft industry. High burning temperatures are necessary to maximize the combustion efficiency of jet engines. Inconel 718, which has excellent mechanical and chemical properties, has been selected for use in many jet engine parts. However, Inconel 718 is a difficult material to cut because of its low thermal conductivity. Consequently, wet cutting is typically used to reduce the heat generated in cutting Inconel 718. Wet cutting, which uses a large amount of cutting fluid, is costly and requires considerable energy for maintenance and disposal of the cutting fluid, making this cutting method environmentally unfriendly. To reduce the associated cost and environmental load, the near-dry cutting method, which uses a very small amount of cutting fluid, may be preferable for cylindrical cutting of Inconel 718. However, this method has some drawbacks, such as the cutting stock removal rate and the wear on cemented carbide tools. For example, the cutting stock removal rate is lower than with wet cutting because cutting edge fracture occurs easily in near-dry cutting. In this study, we conducted experiments to examine the relationships between the tool materials, cutting speed and tool fracture in near-dry cutting and wet cutting, and we compared the results obtained using the two cutting methods. We found that an S05-type cemented carbide coating can reduce tool wear. We also found that in the early stages of cutting, between cutting speeds of V = 50 and 90 m/min, the tool wear can be comparatively reduced.

Tool Wear Characteristics for Near-Dry Cutting of Inconel 718

In recent years, high-combustion-efficiency jet engines are required in the aircraft industry. Inconel 718, which has excellent mechanical and chemical characteristics. However, Inconel 718 is difficult to cut material because of its low-thermal conductivity. Consequently, Wet cutting is ordinarily adopted to reduce the heat on cutting heat edge in Inconel 718 cutting. Wet cutting which uses large amount of cutting fluid requires much cost and energy on maintenance or disposal of cutting fluid, and this method is environmentally-unfriendly. From the view point of reducing cost and environmental load, we examined the method of Near-Dry cutting which uses very small amount of cutting fluid for the cylindrical cutting of Inconel 718. However, this method has some problems, such as tool wear and cutting stock removal rate. In this report, we experimentally examined the relationship between cutting speed, tool materials, and tool fracture of near-dry cutting of Inconel 718. We compared these results with those of wet cutting, a method which is more expensive, requires significantly greater amounts of energy, and is less environment-friendly. The results indicate that when cutting speed is 100 m/min, tool fracture occurs at a cutting distance of 200 m. When cutting speed is 50 m/min, tool fracture does not occur and near-dry cutting distances can continue beyond 600 m. Moreover, tool wear could be reduced when S05 tool material, which has high bending strength, was used.

S132021 Ni基耐熱合金のニアドライ切削における超硬合金の工具摩耗特性([S132-02]先進切削加工技術(2))

In recent years, high-combustion-efficiency jet engines are required in the aircraft industry. The high burning temperature is necessary for upgrading combustion efficiency of jet engines. Therefore, Inconel 718 which has excellent mechanical properties and chemical properties are selected for many jet engine parts. However, Inconel 718 is difficult to cut material because of its low-thermal-conductivity. Consequently, Wet cutting is ordinarily adopted to reduce the heat on cutting heat edge in Inconel 718 cutting. Wet cutting which uses large amount of cutting fluid requires much cost and energy on maintenance or disposal of cutting fluid, and this method is environmentally-unfriendly. From the view point of reducing cost and environmental load, we examined the method of Near-Dry cutting which uses very small amount of cutting fluid for the cylindrical cutting of Inconel 718. However, this method has some problems, such as tool wear and cutting stock removal rate. For example, the cutting stock removal rate is reduced because of cutting edge fracture occurs easily on this method. In this report, we experimentally examined the relationship between cutting speed, tool materials and tool fracture on Near-Dry cutting.

J111011 チタン合金のニアドライ切削加工に関する研究 : 第3報 超硬合金工具における工具摩耗特性

Generally, wet cutting which supplies a lot of cutting fluid is adopted as cutting of the titanium alloy used at the airplane or parts for medical equipment. When near-dry cutting is used as this processing, it will be easy to cause tool damage and stock removal rate and machining accuracy will worsen. So, in this study, it is target at clarification and development of the reduction method of the generating mechanism of the cutting-edge fracture in cylindrical cutting of titanium alloy. This paper examined the relation between cutting distance and cutting tool wear, such as a cutting force, a coefficient of friction on a rake face and tool wear when using MQL cutting of the Ti-6AC-4V material.

Modern Machining of Advanced Aerospace Alloys - Enabler for Quality and Performance

Advanced Aerospace alloys are designed to withstand high loads at extreme temperature conditions in their specific applications. These advanced alloys are more demanding in terms of machinability as their structure and material properties are focused on improved resistance to dwell crack growth, environmental damage (hot corrosion and oxidation) and creep strain, as well as higher levels of microstructure stability and high temperature yield stress. Machining of these alloys therefore focuses on high stock removal rates in roughing processes as well as in high surface finishing rates and good surface finish and surface integrity in finish machining. High performance machining methods will enable the aero engine manufacturing industry to meet increasing future requirements supported by an improved understanding of processes and process control factors. In addition to the technical challenges a number of other elements have to be considered to meet future business requirements, which include robustness of machining solutions and control of boundary conditions to be met in order to ensure acceptable surface and subsurface conditions in machining. Modern machine tool concepts, advanced machining processes and methods are key enablers to achieve overall quality and productivity goals to meet future market requirements.

707 チタン合金の基礎的切削特性の研究 一加工能率一定における切削特性一(OS11-2機械加工の高速・高精度化)

707 チタン合金の基礎的切削特性の研究 一加工能率一定における切削特性一(OS11-2機械加工の高速・高精度化)

Evaluation Technique for Determining Wheel Performance in the Grinding of Aerospace Materials

Nickel-based super alloys are used in a variety of applications in which high-temperature strength and resistance to creep, corrosion, and oxidation are required, such as in aircraft gas turbines, combustion chambers, and automotive engine valves. The properties that make these materials suitable for these applications also make them difficult to grind. Grinding systems for such materials are often built around vitrified cBN (cubic boron nitride) wheels to realize maximum productivity and minimum cost per part. Conditions that yield the most economical combination of stock removal rate and wheel wear are key to the successful implementation of the grinding system. Identifying the transition point for excessive wheel wear is important. The aim of this study is to compare the performance of different cBN wheels when grinding difficult-to-grind (DTG) materials by determining the ‘wheel wear characteristic curve’, which correlates the G-ratio to the calculated tangential force per abrasive grain. With the proposed methodology, a threshold force per grit above which the wheel wear rate increases rapidly can be quickly identified. A comparison of performance for two abrasive product formulations in the grinding of three materials is presented. The obtained results can be applied for the development of grinding applications for DTG materials.

Optimizing of Turning Parameters Using Multi-Objective Genetic Algorithm

In this research, the turning parameters of steel are optimized via multi-objective genetic algorithm and multi-objective harmony research algorithm. These two algorithms are known as strong and powerful tools in optimization of engineering problems. The stock removal rate and surface roughness, as two main of output parameters are the target function and have been considered to be optimized. Since, there are two functions here; we can not use the ordinary optimization method with single-objective algorithm. In steel machining, the stock removal rate usually decreases with the surface finishing and visa versa. Therefore, it is necessary to define the weight of these parameters. In this paper the importance of each of these parameters are determined with weight sum method. In this research, the optimization methods to solve the problems via these two algorithms are discussed first. Then, the steel samples are machined and the output data are analyzed and optimized.

重畳超仕上げに関する研究 : 第3報,重畳振動砥石の損耗現象(機械要素,潤滑,設計,生産加工,生産システムなど)

The objective of this investigation is to clarify a new and high efficient mirror machining process with using ultrasonic and low frequent vibrations, that has been named "superposition superfinishing (SSF process)". In the first report, it was confirmed that a stock removal rate of superposition vibration cutting as cutting process on this SSF process can be higher than that of low frequent superfinishing, and that a high efficient mirror machining can be practically achieved. In the second report, by analysis and consideration on superposition cutting track, it was found that cutting length of this superposition vibration cutting strongly influence on a stock removal amount. In this report, as one reason of obtaining a high stock removal rate, we have adopt equivalent grade characteristics of ultrasonically vibrated abrasive stone. It has be shown that the grade of abrasive stone decreases according as amplitude incleases. On the result of some experiments, it is found that this phenomenon can be controlled by an amplitude value of ultrasonic vibration, and that a rate of abrasive stone ware per one meter of superposition superfinishing is lower than that of low frequent superfinishing in the case of large maximum cross angle.

Effects of abrasive type cooling mode and peripheral grinding wheel speed on the AISI D2 steel ground surface integrity

In this work the AISI D2 steel ground surface integrity was evaluated at different grinding conditions. Two sets of experiments were conducted. The first and the second sets are referred to as conventional grinding tests (CGTs) and high-speed grinding tests (HSGTs), respectively. For the CGTs two different types of abrasives (aluminium oxide and sol–gel alumina) and two cooling modes (oil-based grinding fluid and cryogenic cooling) were tested at a peripheral wheel speed v s =22 m/s. For the HSGTs, an electroplated cBN grinding wheel was used at a peripheral wheel speed ranging from 60 to 260 m/s. Experimental results show that the grindability and the surface integrity of the AISI D2 steel could be substantially improved by using the sol–gel grinding wheel and cooling by liquid nitrogen comparatively with conditions using aluminium oxide and cooling with oil-based grinding fluid. These conditions reduce the grinding force components, lower the level of tensile residual stresses and expand the range of stock removals rate for which compressive residual stresses can be obtained. In this case the stock removal rate could be increased 7 times and still having compressive residual stresses. These experimental results were further explored and it was possible to establish linear relationships between the specific energy and the amplitudes of the surface residual stresses when grinding under the CGTs conditions. This relationship is very useful for process control and optimization. Results of the HSGTs show that the highest levels of the compressive surface residual stresses were obtained at a peripheral wheel speed v s =120 m/s ( σ ∥=−520 MPa, σ ⊥=−770 MPa). These values are much higher than those measured at the ground surface generated using the sol–gel grinding wheel and cooling by liquid nitrogen ( σ ∥=−295 MPa, σ ⊥=−250 MPa). Further, the CGTs and HSGTs results were used to establish the burn-free and burn conditions in relation with the specific grinding energy. It was shown that condition using the sol–gel grinding wheel and cooling with liquid nitrogen and condition using cBN grinding wheel at peripheral wheel speed up to 180 m/s generate specific grinding energy that are significantly lower than the burning threshold energy.

Coolant effect on grinding performance in high-speed deep grinding of 40Cr Steel

High-speed deep grinding (HSDG) technology was developed based on high-speed and creep-feed grinding techniques. What mainly distinguishes HSDG from creep-feed grinding is its employment of a significantly higher wheel speed. Because the higher wheel speed results in a decrease in the undeformed chip thickness, HSDG is thus capable of achieving high stock removal rates and producing a high surface quality throughout the workpiece. However, the increase in wheel speed leads to the formation of a strengthened air barrier around the grinding wheel periphery, which is a great obstacle to the impinging of coolant into the grinding zone. Additionally, the higher wheel speed will also generate greater grinding heat in the grinding zone, thus resulting in a higher temperature.'This increases the risk of thermal damage on the workpiece, such as burns and cracks, especially when grinding metals and alloys. In order to take advantage of the full potential of HSDG technology, effective cooling must be employed. Great research efforts have been directed toward investigating effective coolant supply technologies for the HSDG process. 71° Previous works focused on the development of coolant nozzles for high-speed grinding, which could block the air barrier formation and help smoothly guide the coolant entering the grinding zone. There are several drawbacks regarding these nozzles. First, a gap between the wheel and the air-wiper in the nozzle still exists, which affects the coolant supply when operating at an extremely high speed. Second, the air blocking alters the coolant flow direction, thus resulting in an increase of 30-50% in spindle power. Third, special grinding wheels are required if there is direct contact between the wheel and the air wiper. This article will report on the development of a closed coolant shoe, which can overcome the limitations of previous coolant nozzles, and the effect of the new nozzle on the grinding performance in HSDG of 40Cr steel.