Showing papers in "Machining Science and Technology in 1999"
TL;DR: In this paper, a review of the machining of titanium and its alloys and potential research issues is presented. But, the focus shift of market trends from military to commercial and aerospace to industry has also been reported.
Abstract: Titanium and its alloys are attractive materials due to their unique high strength-weight ratio that is maintained at elevated temperatures and their exceptional corrosion resistance. The major application of titanium has been in the aerospace industry. However, the focus shift of market trends from military to commercial and aerospace to industry has also been reported. On the Other hand, titanium and its alloys are notorious for their poor thermal properties and are classified as difficult-to-machine materials. These properties limit the use of these materials especially in the commercial markets where cost is much more of a factor than in aerospace. Machining is an important manufacturing process because it is almost always involved if precision is required and is the most cost effective process for small volume production. This paper reviews the machining of titanium and its alloys and proposes potential research issues.
317 citations
TL;DR: In this article, the effect of current, voltage, pulse-on-time and duty factor on the grinding forces and material removal rate while machining high speed steel workpiece was investigated.
Abstract: A combination of two machining processes (i.e., a hybrid process) has a potential to improve process performance. This paper reports on experimental investigation of the electrical discharge diamond grinding process that combines mechanical grinding with electrical discharge machining. In this process, the workpiece is simultaneously subjected to heating, by electrical sparks bridging the gap between the metallic wheel bonding material and the work, and abrasion by diamond grains. The effect of current, voltage, pulse-on-time and duty factor on the grinding forces and the material removal rate while machining high speed steel workpiece, are investigated. The spark discharges facilitate grinding by thermally softening the work material in the grinding zone, and consequently decreasing the nromal force. It is observed that the material removal rate increases with an increase in current and pulse on-time, while it decreases with an increase in voltage and duty factor. These independent parameters ar...
56 citations
TL;DR: In this article, the machining of carbon/PEEK, a high performance thermoplastic matrix composite, was investigated to investigate the relative effects of various machining parameters on the amount of tool wear and the surface quality of the workpiece.
Abstract: Composites are generally fabricated to near nett-shape, however, there is often a need to conduct some additional machining operations such as trimming of the edges. High tool wear and the need for good surface finish are some of the major concerns in machining. This study deals with the machining of Carbon/PEEK, a high performance thermoplastic matrix composite, which is being used extensively in aerospace industries because it is light and posses high specific properties compared to conventional metallic materials. The technique of the full factorial design of experiment is used to investigate the relative effects of the various machining parameters on the amount of tool wear and the surface quality of the workpiece. Experimental results show that the cutting speed, depth of cut and feed-rate are the main factors that contribute to tool wear of the inserts. The surface finish is found to be independent of the machining parameters and much better than those obtained in the conventional machining...
40 citations
TL;DR: In this paper, three predictive models for the forces, power and chip flow angle based on the unified mechanics of cutting approach have been developed while the surface roughness models have been based on feed marks generated on the machined surface allowing for the precise tool corner profile.
Abstract: In this paper the need for reliable quantitative machining performance information for efficient and effective use of machining operations is discussed, as are the recent developments of predictive models for forces and power in practical machining operations based on the 'unified mechanics of cutting approach'. This investigation is aimed at extending this mechanics of cutting approach to turning with rounded corner plane faced lathe tools. Three predictive models for the forces, power and chip flow angle based on the 'unified mechanics of cutting approach1 have been developed while the surface roughness models have been based on the feed marks generated on the machined surface allowing for the precise tool corner profile. The first force model is based on the modified mechanics of cutting analyses for single edge tools while the two alternative models are based on the generalised mechanics of cutting analyses for single edge and multi-edge form tools for the turning cut as a whole. The predicti...
22 citations
TL;DR: The Mapping System for Grinding Wheels (MSGW) as mentioned in this paper is based on an optical scanner capable of measuring the light beam reflected from the wear flat areas on the abrasive grains over the whole wheel peripheral surface.
Abstract: The efficiency of the grinding operation is highly dependent on the grinding wheel surface topography. Several methods for the evaluation of the grinding wheel surface have been developed in the last few years. In some of these methods, the grinding wheel has to be removed from the machine for an evaluation using a microscope or a profilometer. Some other methods are able to measure the topography at the grinding machine, but they do not give detailed information about grain distribution and wear. This paper shows a new method to map the grinding wheel surface. The proposed system is based on an optical scanner capable of measuring the light beam reflected from the wear flat areas on the abrasive grains over the whole wheel peripheral surface. The Mapping System for Grinding Wheels (MSGW) is able to acquire data with the wheel running at the work speed (30 m/s)and the measurement carried out on the grinding machine without stopping. The system is applied on a surface grinding operation where an A...
17 citations
TL;DR: In this article, the critical depth of cut for MMCs reinforced with either A1203 or SiC was found to be 1 p.m and 0.2 u.m, respectively.
Abstract: This paper presents research results on ultraprecision machining of metal matrix composite (MMC) composed of aluminum matrix and either SiC or A12 03 particles. Ductile-regime machining of both SiC and aluminum was evaluated to improve the surface integrity of the composite. Both polycrystal-line diamond (PCD) and single crystalline diamond (SCD) tools were used to ultraprecision machine the composites at a depth of cut ranging from 0 to 1μm using a taper cut. The feedrate was normalized to the tool nose radius. A model is proposed to calculate the critical depth of cut for MMCs reinforced with either A1203 or SiC. The critical depths of cut were found to be 1 p.m and 0.2 u.m for MMCs reinforced with A12 0 or SiC3, respectively. Both depth of cut and crystallographic direction of the ceramic particles are the sufficient conditions for ductile-regime machining. Although both tools produce similar surface finish, a SCD tool removed the MMC as chips while a PCD tool simply smeared the surface. A dif...
16 citations
TL;DR: In this article, an experimental system and methodology that aims to simultaneously quantify the effectiveness of cutting fluid in thermal (cooling characteristics) and mechanical (frictional effects) terms is proposed.
Abstract: The use of cutting fluids in industrial machining is widespread, while scientific research of the performance of cutting fluids lags behind. While much has been documented about the beneficial mechanisms of tool-chip lubricity and heat transfer from varying fluid types and applications, an accurate, flexible, and expedient method for investigating cutting fluid performance lies beyond the scope of modern experimental methods. This paper proposes an experimental system and methodology that aims to simultaneously quantify the effectiveness of cutting fluid in thermal (cooling characteristics) and mechanical (frictional effects) terms. The system acquires cutting force measurements with a piezoelectric tool post dynamometer to gauge the mechanical effectiveness of the cutting fluid through the variation in friction coefficient. Thermal effectiveness is examined by comparison of thermal images of the tool flank face obtained through the use of full-field infrared imaging and a point temperature obtai...
15 citations
TL;DR: In this article, the authors carried out extensive numerical simulation and experimental verification of the predictive force and surface roughness models for turning operations encompassing the domain of cutting conditions recommended in practice and found that the three force models predicted very similar qualitative and plausible trends in the tangential, feed and radial force components as well as chip flow angle with changes in many operation variables.
Abstract: Extensive numerical simulation and experimental verification of the predictive force and surface roughness models for turning operations have been carried out encompassing the domain of cutting conditions recommended in practice. It has been shown that the three force models predicted very similar qualitative and plausible trends in the tangential, feed and radial force components as well as chip flow angle with changes in the many operation variables. The experimental testing involved about 500 turning cuts over a wide range of inclination angles, normal rake angles, major cutting edge angles, corner radius, feed and depth of cut. All the qualitative trends in the forces and chip flow angle noted in the simulation studies have been experimentally confirmed for all the three force models for both TiN coated and uncoated tools. The first two force models predictions correlated very well with the experimental results while only reasonable correlation was found with the third (approximate) model. Th...
14 citations
Abstract: Prediction of chip breaking in machining is an important task for automated manufacturing. This paper presents a study on chip breaking limits. Based on the chip breaking curve, the critical feed-rate is modeled through an analysis of up-curl chip formation, and the critical depth-of-cut is formulated through a discussion of side-curl dominant chip formation processes. Factors affecting chip-breaking limits are also discussed. In order to predict the chip breaking limits, semi-empirical models are established. Although the coefficients that occur in the model are estimated through machining tests, the models are applicable to a broad range of machining conditions. The model parameters include machining conditions, tool geometry, and workpiece material properties.
14 citations
TL;DR: A cutting device has been developed by utilizing the scanning system of atomic force microscope (AFM) in machining, which aims at clarifying the ultimately small size removal as well as observing t... as mentioned in this paper.
Abstract: A cutting device has been developed by utilizing the scanning system of atomic force microscope (AFM) in machining, which aims at clarifying the ultimately small size removal as well as observing t...
13 citations
TL;DR: In this paper, the authors used aqueous metalworking fluids and non-superabrasive grinding wheels for the purpose of optimizing the grinding process of a milling machine, and limited the material ground to two different grades of steel.
Abstract: The purpose of this study was to optimize the grinding process by the use of different types of metalworking fluids and grinding wheels. The four most important variables in the grinding process are the grinding machine, the grinding wheel, the metalworking fluid, and the type of material being ground (the part). This study limited the material ground to two different grades of steel. In most machine shops today, the grinding machine is a fixed component, as modification or replacement is too expensive. However, the metalworking fluid and the grinding wheel are relatively inexpensive and easy components to change. Therefore, this paper will only consider changes in the metalworking fluid and the grinding wheel when attempting to optimize the grinding process. Furthermore, this study will limit these two components to aqueous metalworking fluids and non-superabrasive grinding wheels.
TL;DR: In this article, experiments involving the orthogonal machining of precipitation hardened aluminium alloys, principally 2014, have been carried out in controlled low pressure environments in which, for a given feed (that is the depth of cut), speed and temperature have been varied while using a variety of lubricating species in vapour form in combination with high speed steel cutting.
Abstract: Friction between the rake face of a cutting tool and the freshly formed chip surface plays a vital role in influencing both the ease of cutting and the quality of the resultant machined surface. The existence of clean surfaces together with the high local hydrostatic stresses favour the formation of strong adhesion between the cutting tool or insert and the machined component. These adhesive bonds can lead to poor surface integrity although their extent can be limited by the provision of a suitable machining lubricant. In an effort to identify the essential lubricating aspects of fluid activity, as opposed to any role as a coolant, experiments involving the orthogonal machining of precipitation hardened aluminium alloys, principally 2014, have been carried out in controlled low pressure environments in which, for a given feed (that is the depth of cut), speed and temperature have been varied while using a variety of lubricating species in vapour form in combination with high speed steel cutting i...
TL;DR: In this paper, the authors derived the concept of laser machining in a cryogenic environment and analyzed the anisotropic heat affected zone (HAZ) associated with cryogenic parameters for both principal-axis and non-principal-axis grooving.
Abstract: The traditional cutting of fiber-reinforced plastics causes serious concern of tool wear. The merits of narrow cuts and flexible path of lasers lead to the application of the shaping operation of composite material after curing. However, laser-induced thermal damage is often produced. It leads to poor assembly tolerance and long-term performance deterioration, The current study derives the concept of laser machining in a cryogenic environment. The anisotropic heat affected zone (HAZ) associated with cryogenic parameters is experimentally and analytically investigated for both principal-axis and non-principal-axis grooving in the example of unidirectional Carbon/Epoxy laminates. In principal-axis grooving, an analytical model based on a moving point heat source with a Mirror Image Method and immersed heat source can illustrate the effect of cryogenic surrounding on HAZ, while Finite Difference Method (FDM) is applied for prediction in the case of nonprincipal-axis grooving. The results reveal that...
TL;DR: In this article, an approach for simulation and production implementation of centerless grinding of transformation toughened zirconia using vitreous bond diamond grinding wheels is presented, and a set of grinding tests are designed and conducted to identify the effects of abrasive product (diamond grit size), work-material, and operational factors (stock removal, thru-feed rate, number of thrufeed passes and truing and dressing methods) on grinding performance.
Abstract: An approach for simulation and production implementation of thru-feed centerless grinding of transformation toughened zirconia using vitreous bond diamond grinding wheels is presented. A set of grinding tests was designed and conducted to identify the effects of abrasive product (diamond grit size), work-material, and operational factors (stock removal, thru-feed rate, number of thru-feed passes and truing and dressing methods) on grinding performance. Evaluation parameters of surface finish, grinding forces and C-ratio were utilized to determine machine tool features. Very fine surface finishes, in the order of 0.05 to 0.1 u.m Ra range, could be achieved using vitreous bond micro-grit diamond wheels, without additional part processing. Such a level of surface finish on ground ceramics has traditionally been generated only by using resinoid bonded diamond wheels. These test results were used to design and manufacture a full-size composite or sandwiched diamond grinding wheel. This grinding wheel ...
TL;DR: In this article, an analytical assessment of this procedure demonstrates that this procedure is fundamentally incorrect for materials, like zinc, which exhibit high strain rate sensitivity, however, for materials which are strain rate insensitive however the procedure is valid.
Abstract: One suggested procedure for determining parasitic cutting loads is to conduct cutting tests at different feeds, measure the cutting forces, plot the forces as a function of feed and extrapolate the data to zero feed. The intercept obtained at zero feed is identified as the parasitic cutting load. This procedure has been tested against cutting data for zinc and shown to give incorrect results. Further an appreciable non-zero intercept was obtained even when the known parasitic cutting forces were subtracted from the measured data. An analytical assessment of this procedure demonstrates that this procedure is fundamentally incorrect for materials, like zinc, which exhibit high strain rate sensitivity. For materials which are strain rate insensitive however the procedure is valid. The validity of the procedure is essentially insensitive to the work hardening behavior of the work piece.
TL;DR: In this article, an analysis of the entry process and tool fracture in the milling operation is presented, which reveals that the direction of the cutting force and the initial location on the rake face determine the entry fracture in milling cutters.
Abstract: This paper presents an analysis of the entry process and tool fracture in the milling operation. Equations representing different types of initial contacts are derived. Experimental and theoretical results reveal that the direction of the cutting force and the initial location on the rake face determine the entry fracture in milling cutters.