Showing papers in "Machining Science and Technology in 2003"
TL;DR: In this article, the variation of workpiece surface roughness with varying pulse duration, open circuit voltage, wire speed and dielectric fluid pressure was experimentally investigated in WEDM.
Abstract: In this study, the variation of workpiece surface roughness with varying pulse duration, open circuit voltage, wire speed and dielectric fluid pressure was experimentally investigated in Wire Electrical Discharge Machining (WEDM). Brass wire with 0.25 mm diameter and SAE 4140 steel with 10 mm thickness were used as tool and workpiece materials in the experiments, respectively. It is found experimentally that the increasing pulse duration, open circuit voltage and wire speed, increase the surface roughness whereas the increasing dielectric fluid pressure decreases the surface roughness. The variation of workpiece surface roughness with machining parameters is modelled by using a power function. The level of importance of the machining parameters on the workpiece surface roughness is determined by using analysis of variance (ANOVA).
94 citations
TL;DR: In this paper, an experimental study to enhance the cutting performance in abrasive waterjet (AWJ) machining is presented, which uses the techniques of jet forward impact angles and multipass operations both individually and concurrently when cutting an alumina ceramic and a polymer matrix composite.
Abstract: An experimental study to enhance the cutting performance in abrasive waterjet (AWJ) machining is presented. The study uses the techniques of jet forward impact angles and multipass operations both individually and concurrently when cutting an alumina ceramic and a polymer matrix composite. A brief report on the effect of jet impact angle in single pass cutting is made first, which shows that the optimum jet impact angle for both the ceramics and polymer matrix composite is about 80°. It is found that the multipass cutting technique can increase the cutting capability and application domain of AWJ cutting. It can also improve the major cutting performance such as the depth of cut as compared to single pass cutting within the same total cutting time. The benefit of using multipass cutting operations is further enhanced when it is combined with a jet forward angle of 80° in cutting alumina ceramics.
69 citations
TL;DR: In this article, the authors present the results of calibrated, microscopic measurement of the temperature fields at the tool-chip interface during the steady-state, orthogonal machining of AISI 1045 steel.
Abstract: This paper presents the results of calibrated, microscopic measurement of the temperature fields at the tool–chip interface during the steady‐state, orthogonal machining of AISI 1045 steel. The measurement system consists of an infrared imaging microscope with a 0.5 mm square target area, and a spatial resolution of less than 5 µm. The system is based on an InSb 128 × 128 focal plane array with an all‐reflective microscope objective. The microscope is calibrated using a standard blackbody source from NIST. The emissivity of the machined material is determined from the infrared reflectivity measurements. Thermal images of steady state machining are measured on a diamond‐turning class lathe for a range of machining parameters. The measurements are analyzed by two methods: 1) energy flux calculations made directly from the thermal images using a control–volume approach; and 2) a simplified finite‐difference simulation. The standard uncertainty of the temperature measurements is ± 52°C at 800°C.
52 citations
TL;DR: In this paper, the closed-form solutions of surface roughness parameters for a theoretical profile consisting of elliptical arcs are presented, and a single chart is developed to present the surface Roughness parameters.
Abstract: The closed‐form solutions of surface roughness parameters for a theoretical profile consisting of elliptical arcs are presented. Parabolic and simplified approximation methods are commonly used to estimate the surface roughness parameters for such machined surface profiles. The closed‐form solution presented in this study reveals the range of errors of approximation methods for any elliptical arc size. Using both implicit and parametric methods, the closed‐form solutions of three surface roughness parameters, R t , R a , and R q , were derived. Their dimensionless expressions were also studied and a single chart was developed to present the surface roughness parameters. This research provides a guideline on the use of approximate methods. The error is smaller than 1.6% when the ratio of the feed and major semi‐axis of the elliptical arc is smaller than 0.5. The closed‐form expressions developed in this study can be used for the surface roughness modeling in CAD/CAM simulations.
38 citations
TL;DR: In this article, the feasibility of application of solid lubricants in grinding was investigated and the detailed investigations on solid lubricant integrated grinding wheels, by providing peripheral graphite sandwiching.
Abstract: The intense heat generated in grinding process, if not controlled, will lead to major quality defects. Conventional liquid coolants, employed in flood form, have many limitations from technical, environmental and economic angles. Minimization or possible elimination of cutting fluids by substituting their functions by some other means is emerging as a thrust area of research in grinding. The authors have reported the feasibility of application of solid lubricants in grinding. This paper deals with the detailed investigations on solid lubricant integrated grinding wheels, by providing peripheral graphite sandwiching. Improvement in process results has been observed with this concept.
32 citations
TL;DR: In this paper, a recently developed ultra-hard AlMgB14-20%TiB2 composite material was applied as a coating on WC/6%Co tool inserts by a pulsed laser (excimer) deposition technique.
Abstract: Despite several years of research and development, titanium machining remains a challenging task that is currently carried out by the use of straight WC/Co and polycrystalline diamond (PCD) tools. Commercially available coated tools tend to react chemically with titanium, while ceramic tools suffer from chipping and notching. Advancements in cutting tools, particularly coated carbides, are needed to reduce tool wear in machining of titanium alloys. In this work, a recently developed, ultra‐hard AlMgB14–20%TiB2 composite material was applied as a coating on WC/6%Co tool inserts by a pulsed laser (excimer) deposition technique. The coating was smooth, continuous, and fairly uniform in thickness. The average coating thickness was 0.7 μm for a deposition rate of 0.08 nm per pulse. Nanoindentation tests revealed that the hardness of the coating was approximately twice that of the WC/6%Co substrate. Dry machining tool wear tests, conducted with a CNC lathe by turning bar stocks of heat‐treated Ti‐6Al‐4V alloy, ...
25 citations
TL;DR: The aim of this research is to use artificial neural networks as the brain of grinding machine controller to achieve the desired workpiece surface roughness under grinding wheel surface topography variations.
Abstract: In recent years, artificial intelligence played an important role in machine tool automation. Artificial neural networks, as one of the artificial intelligence algorithms, has superiority in representing the relation between the inputs and outputs of the multi‐variable system. Hence, it can be applied to sophisticated operations such as grinding operation. The aim of this research is to use artificial neural networks as the brain of grinding machine controller. The target of this controller was to achieve the desired workpiece surface roughness under grinding wheel surface topography variations. The core of the system consists of two multi‐layers feed forward artificial neural networks based on back error propagation learning algorithm. The first one was used for process design to achieve the desired surface roughness. It extracts suitable process variables such as grinding wheel speed and feed rate. The second one monitors the cutting operation using sensors' readings. It extracts the different controlli...
25 citations
TL;DR: In this article, a computer-aided forward analysis of a typical automated flute grinder used in drill production has been performed, based on the intended or design flute profile of twist drills.
Abstract: A computer‐aided ‘forward’ analysis, based on a typical automated flute grinder used in drill production, has been developed to study the flute generation process and the intended or design flute profile of twist drills. It has been shown that the flute grinder involved three machine setting variables and seven wheel profile variables for generating the flute for each drill specification. Based on the recommended wheel profile and machine settings, the forward analysis has shown that the flute profile was partly generated by the ‘envelope’ of the wheel profiles and partly by the locus of the point of discontinuity on the wheel profile. Furthermore, these numerical simulation studies have shown that the intended or design lip flute profile closely approximated the ideal profile for straight lip production while the heel profile closely approximated a parabolic curve tangential to the core or web diameter and passing through the heel corner. Numerical simulation of the effect of the machine settings has sho...
25 citations
TL;DR: The present contribution approaches the problem of predicting delamination in drilling of GFRP (Glass Fiber Reinforced Plastics) in order to reduce the damage on laminates by means of feed‐forward neural networks.
Abstract: The present contribution approaches the problem of predicting delamination in drilling of GFRP (Glass Fiber Reinforced Plastics) in order to reduce the damage on laminates. For this purpose, a software system has been developed and tested with the scope of performing an on‐line prediction of the entity of the damage both at the entry side of the tool (peel‐up damage) and at the exit side (push‐out damage). The prediction is made possible by means of feed‐forward neural networks, which are able to give a “measure” of the incipient damage process in function of the cutting conditions such as: feed rate, tool size, cutting forces, etc. In order to find the best solution in terms of performances, two architectures of neural networks have been proposed and investigated: the former is able to sort the predicted delamination in four categories (no damage, low, medium and high damage), the latter is able to directly predict an average value (in mm) of the damage. After a brief survey on related works, the paper d...
25 citations
TL;DR: In this paper, the effect of laser pulse energy on the geometric quality of the machined parts in terms of accuracy, precision, and surface quality was investigated experimentally, and the geometrical parameters were measured and statistically analyzed with respect to incident pulse energy.
Abstract: In laser precision machining, process parameters have critical effects on the geometric quality of the machined parts. Due to the nature of the interrelated process parameters involved, an operator has to make a host of complex decisions, based on trial‐and‐error methods, to set the process control parameters related to the laser, workpiece material, and motion system. The objective of this work is to investigate experimentally the effect of laser pulse energy on the geometric quality of the machined parts in terms of accuracy, precision, and surface quality. Experimental study of formation of machined craters on thin copper foil with variation in laser pulse energy, the geometry and the surface topology of craters is presented. The geometrical parameters were measured and statistically analyzed with respect to incident pulse energy. Statistical analysis including pattern recognition was employed to analyze the experimental data systematically and to serve proper selection of the process parameters to ach...
18 citations
TL;DR: In this paper, the problem of minimizing the peak compliance of a high speed machining (HSM) spindle's thrust axis is examined, and both complex and mixed μ synthesis is used to design controllers.
Abstract: Many practical problems in magnetic bearing control concern essentially the minimization (maximization) of the dynamic compliance (stiffness) of the rotor. In this paper, the problem of minimizing the peak compliance of a high speed machining (HSM) spindle's thrust axis is examined. Experimental results are presented which demonstrate that μ synthesis provides an excellent tool for tackling this problem. Both complex μ and mixed μ synthesis are used to design controllers. The performance of the μ controllers is compared to that of an optimized PID controller. Under μ control, the dynamic stiffness of the system was increased by more than a factor of two over that obtained with the optimal PID controller. Careful attention was given to developing an accurate system model and uncertainty description, especially related to the transfer function of the magnetic actuators with solid stators and thrust disk.
TL;DR: In this paper, the rotor profile manufacturability is evaluated from three aspects: the required minimum tool profile radius, the range of valid setup conditions, and the severity ratio which is a measure of relative tool profile load distribution.
Abstract: Effective evaluation of rotor profile manufacturability becomes a necessary step in the design stage to reduce rotor development cycle This paper is concerned with analyzing screw rotor manufacturability using rotor profile design data The rotor profile manufacturability is discussed from three aspects: the required minimum tool profile radius, the range of valid setup conditions, and the severity ratio which is a measure of relative tool profile load distribution With this analysis, the rotor profile manufacturability can be quickly evaluated in its design stage It can also be used as a design criterion to design rotor profiles for better manufacturability
TL;DR: In this article, a computer-aided backward analysis based on the contact curve method has been developed to determine the required grinding wheel profile for generating a given drill flute profile design and fluting machine settings.
Abstract: A computer‐aided ‘backward’ analysis based on the contact curve method has been developed to determine the required grinding wheel profile for generating a given drill flute profile design and fluting machine settings. The required grinding wheel profile was expressed in digitised form as well as in terms of two curve‐fitted circular arcs whose radii and centre coordinates represented the required wheel dresser settings on the typical flute grinder modelled. The ‘backward’ analysis was integrated with the ‘forward’ analysis from the first paper to form a CAD/CAM package with graphics modules. Simulation studies have shown that only a portion of the required digitised wheel profile was physically feasible so that only the portion of the flute profile generated by an enveloping process precisely matched the design flute profile while the flute profile in the web region, generated by the locus of point of discontinuity on the wheel profile, approximated the design flute profile. Furthermore, the typical dril...
TL;DR: In this article, a method for robust design of a neural network (NN) model for prediction of delamination (Da), damage width (Dw), and hole surface roughness (Ra) during drilling in carbon fiber rein...
Abstract: In this paper, a method for robust design of a neural network (NN) model for prediction of delamination (Da), damage width (Dw), and hole surface roughness (Ra) during drilling in carbon fiber rein...
TL;DR: In this article, a model-based simulation is presented to analyze the influence of manufacturing process variations on rotor profile, by varying machine parameters within their tolerance bands, the simulation predicts rotor profile errors caused by various process parameter errors.
Abstract: A model‐based simulation is presented to analyze the influence of manufacturing process variations on rotor profile. The simulation servers as a virtual machine tool to virtually machine rotors. By varying machine parameters within their tolerance bands, the simulation predicts rotor profile errors caused by various process parameter errors. The input to the simulation includes designed rotor profile data, lead, diameters, and machine setup and machine capability expressed in terms of parameter accuracy. The output is the ‘manufactured’ rotor profile. The simulation can be used to evaluate if a machine or process is capable of making the designed profile with the required tolerance. It can also be used to check and validate rotor clearance distributions in the design stage.
TL;DR: In this article, a method for solving the nonlinearity errors problem in five-axis CNC machining is presented, based on the machine type-specific kinematics and the machining motion trajecto...
Abstract: In the machining of sculptured surfaces, five‐axis CNC machine tools provide more flexibility to realize the cutter position as its axis orientation spatially changes. Conventional five‐axis machining uses straight line segments to connect consecutive machining data points, and uses linear interpolation to generate command signals for positions between end points. Due to five‐axis simultaneous and coupled rotary and linear movements, the actual machining motion trajectory is a non‐linear path. The non‐linear curve segments deviate from the linearly interpolated straight line segments, resulting in a non‐linearity machining error in each machining step. These non‐linearity errors, in addition to the linearity error, commonly create obstacles to the assurance of high machining precision. In this paper, a novel methodology for solving the non‐linearity errors problem in five‐axis CNC machining is presented. The proposed method is based on the machine type‐specific kinematics and the machining motion trajecto...
TL;DR: In this article, the authors discuss the development of an effective electrolytic in-process dressing technique for high speed grinding and an innovative foil electrode has been designed and tested, and the performance of a hydrodynamic foil electrode is discussed.
Abstract: This paper discusses the development of an effective electrolytic in‐process dressing technique for high speed grinding. An innovative foil electrode has been designed and tested. The performance of a hydrodynamic foil electrode is discussed. Experimental investigations confirm that foil electrodes show significant improvement on electrolytic in‐process dressing even when the electrolyte supply rate is low.
TL;DR: In this article, hot pressed AlMgB14 was employed in lathe turning tests cutting exterior surface material from 6061 aluminum, 304 stainless steel, Inconel, and concrete at various cutting rates.
Abstract: Tool specimens of hot pressed AlMgB14 were employed in lathe turning tests cutting exterior surface material from 6061 aluminum, 304 stainless steel, Inconel, and concrete at various cutting rates. Performance was measured via analysis of mass change (removal rate), wear mechanisms, surface chemistry (reactivity), and fracture mechanisms. Preliminary results indicate that this new family of ultra‐hard materials exhibits good cutting performance against all four workpiece materials, while combining favorable toughness with an unusual absence of tool heating, leading to minimal wear and anticipation of long life in application for sectioning of ferrous‐based metals and structures such as reinforced concrete containing such metals. The potential value of these new materials for use in disassembly of decommissioned nuclear reactor pressure vessels is discussed.
TL;DR: In this article, a neural network is trained to reconstruct the stress-strain curve of the work material on the basis of experimental tensile tests in a wide range of temperature and strain rate values.
Abstract: The fully integrated use of a neural network (NN) paradigm for material rheological behaviour modelling and a FEM code for the simulation of orthogonal metal cutting is illustrated. A NN is trained to reconstruct the stress‐strain curve of the work material on the basis of experimental tensile tests in a wide range of temperature and strain rate values. The learned NN is capable of predicting work material properties in the whole range of temperature and strain rate values utilized for training. The material rheological behaviour, modelled by the NN, is used in the FEM simulation to provide the work material properties to the FEM code for each node of the workpiece mesh during the simulation. To achieve this result, a continuous information exchange between the learned NN and the FEM code during each iteration is devised.
TL;DR: The present paper deals with the preliminary study and the prototypical implementation of an expert system to quickly define an high level manufacturing sequence able to produce the assigned part tolerances.
Abstract: The present paper deals with the preliminary study and the prototypical implementation of an expert system to quickly define an high level manufacturing sequence able to produce the assigned part tolerances. To do so, the expert system simulates the human reasoning process by applying specific knowledge and inferences. An assembly that is widely used to test the performances of different design methods represents the case study. This module belongs to a flexible and integrated environment that aims to automatically define both the tolerance specifications and the related process plan. Its aim is to support the designer during the definition of a functional project.
TL;DR: MAGIC (MAGnetic Intelligent Compounds) grinding stone as discussed by the authors is a new bonding type grinding stone and introduces its manufacturing process and characteristics, which can follow die shapes using shape transfer method.
Abstract: Although the full automation of die manufacturing has recently developed markedly, manual polishing is still necessary for die because precision dies have in general three‐dimensionally complicated shapes. Complicated and narrow areas of the die are difficult to be polished with the conventional grinding stone. This study proposes a new bonding type grinding stone and introduces its manufacturing process and characteristics. Here, the new bonding type grinding stone is called MAGIC(MAGnetic Intelligent Compounds) grinding stone. MAGIC grinding stone has many advantages as follows: 1) Manufacturing such grinding stone that can follow die shapes using the shape transfer method is possible, 2) Grinding stones in which abrasive grains are uniformly dispersed can be manufactured using magnetic particles and a magnetic field, 3) It is possible to reshape the grinding stone by heating since the binder is made of a thermoplastic resin, 4) Every process can easily be carried out. Stabilized polishing characteristi...
TL;DR: In this paper, a fuzzy logic theory is proposed to build up a k-layer model for water jet cutting of composite materials of lightweight structures, which can have various types of cover layers (defined by e.g., sheet thickness and material).
Abstract: The process of water jet cutting has advantages over laser beam cutting, especially in the case of temperature‐sensitive materials. Together with the foam and cellulose material processing, the processing of composite materials of lightweight structures is becoming more and more important. In order to meet given requirements, these sandwich constructions can have various types of cover layers (defined by e.g., sheet thickness and material) and consist of core materials (differing e.g., in geometry or in structure). Unlike simple sheets, multilayer structures have greater influence on the cutting result. When the process is planned, the CAD/CAM‐systems must take all sheets of the composite material into account in order to avoid manufacturing problems. Due to the great variety of composite materials and desired contours, the necessary knowledge or experience must be efficiently represented. There is no universal system model for all these variations. This paper suggests a fuzzy‐logic theory to build up a k...
TL;DR: In this paper, a software system is proposed which adapts the CAD models to their corresponding real workpiece by compensating deviations in shape and location, as a result cutting quality and accuracy are improved.
Abstract: Due to its high flexibility and its high accuracy laser machining has become the common process to perform three‐dimensional cutting on deep‐drawn workpieces especially when small lot sizes are to be machined. In the last few years the programming of laser machines has changed from teach‐in to off‐line programming, where the tool path definition is done in a CAM system based on a CAD model of the workpiece. Owing to tolerances in workpiece geometry and positioning, the off‐line programmed tool paths often do not fit exactly the surface of the real workpiece. In this publication, a software system is proposed which adapts the CAD models to their corresponding real workpiece by compensating deviations in shape and location. As a result cutting quality and accuracy are improved.