Magnitude Of Cutting Force Research Articles

Investigation of influence of tool rake angle in single point diamond turning of silicon

This paper presents an investigation of the effect of tool rake angle in single point diamond turning (SPDT) of silicon using experimental and simulation methods. Machining trials under the same cutting conditions were carried out using three different rake angle tools. In order to delve further into the rake angle effect on the output parameters including material removal, stresses and crack formation, at the onset of chip formation and steady-state conditions, a simulation study using smoothed particle hydrodynamics (SPH) approach was performed. The simulation results were incorporated and found in good agreement with experimental observations. The results indicate that diamond tool wear rate and surface generation mechanism significantly vary using different rake angle tools. The continuance of compressive and shear deformation sequence at the chip incipient stage governs the high-pressure phase transformation (HPPT) as a function of rake angle and tool wear. The capability of diamond tool to maintain this sequence and required hydrostatic pressure under worn conditions is highly influenced by a change in rake angle. The proportional relationship of cutting force magnitude and tool wear also differs owing to disparate wear pattern which influence distribution of stresses and uniform hydrostatic pressure under the tool cutting edge. This subsequently influences structural phase transformation and therefore frictional resistance to cutting. Mainly frictional groove wear was found dominant for all diamond tools in machining of silicon.

Finite Element Analysis Of Influence Of Flank Wear Evolution On Forces In Orthogonal Cutting Of 42CrMo4 Steel

Abstract This paper presents analysis of flank wear influence on forces in orthogonal turning of 42CrMo4 steel and evaluates capacity of finite element model to provide such force values. Data about magnitude of feed and cutting force were obtained from measurements with force tensiometer in experimental test as well as from finite element analysis of chip formation process in ABAQUS/Explicit software. For studies an insert with complex rake face was selected and flank wear was simulated by grinding operation on its flank face. The aim of grinding inset surface was to obtain even flat wear along cutting edge, which after the measurement could be modeled with CAD program and applied in FE analysis for selected range of wear width. By comparing both sets of force values as function of flank wear in given cutting conditions FEA model was validated and it was established that it can be applied to analyze other physical aspects of machining. Force analysis found that progression of wear causes increase in cutting force magnitude and steep boost to feed force magnitude. Analysis of Fc/Ff force ratio revealed that flank wear has significant impact on resultant force in orthogonal cutting and magnitude of this force components in cutting and feed direction. Surge in force values can result in transfer of substantial loads to machine-tool interface.

Modelling of dynamic cutting force coefficients and chatter stability dependent on shear angle oscillation

Productivity of high-speed turning operations is limited by the onset of self-excited vibrations known as chatter. Unless avoided, chatter vibrations may cause large dynamic loads damaging the machine spindle, cutting tool or workpiece and leave a poor surface finish behind. Cutting force magnitude is proportional to the thickness of the chip removed from the workpiece. This paper presents a new procedure to determine dynamic cutting force coefficients (DCFC) required for process simulation by mechanistic modelling. In this study, a two degree of freedom complex dynamic model of turning with an orthogonal cutting system is considered. The complex dynamic system consists of a dynamic cutting system force model based on shear angle (φ) oscillations and penetration forces caused by the tool flank’s contact with the wavy surface. The dynamic cutting force coefficients are identified by operating a series of cutting tests at the desired frequency, while changing φ oscillations and penetration forces. It is shown that the process damping coefficient increases as the tool is worn, which increases the chatter stability limit in cutting. The chatter stability of a dynamic cutting process is solved using the Nyquist law and time domain simulation (TDS) techniques and compared favourably against experimental results at low cutting speeds. Finally, comparisons among the proposed mechanistic model and experimental results show a good agreement with the analytically established SLD and, thus, validate the effectiveness of the proposed model.

Optimization of the dressing parameters in cylindrical grinding based on a generalized utility function

The existing studies, concerning the dressing process, focus on the major influence of the dressing conditions on the grinding response variables. However, the choice of the dressing conditions is often made, based on the experience of the qualified staff or using data from reference books. The optimal dressing parameters, which are only valid for the particular methods and dressing and grinding conditions, are also used. The paper presents a methodology for optimization of the dressing parameters in cylindrical grinding. The generalized utility function has been chosen as an optimization parameter. It is a complex indicator determining the economic, dynamic and manufacturing characteristics of the grinding process. The developed methodology is implemented for the dressing of aluminium oxide grinding wheels by using experimental diamond roller dressers with different grit sizes made of medium- and high-strength synthetic diamonds type ??32 and ??80. To solve the optimization problem, a model of the generalized utility function is created which reflects the complex impact of dressing parameters. The model is built based on the results from the conducted complex study and modeling of the grinding wheel lifetime, cutting ability, production rate and cutting forces during grinding. They are closely related to the dressing conditions (dressing speed ratio, radial in-feed of the diamond roller dresser and dress-out time), the diamond roller dresser grit size/grinding wheel grit size ratio, the type of synthetic diamonds and the direction of dressing. Some dressing parameters are determined for which the generalized utility function has a maximum and which guarantee an optimum combination of the following: the lifetime and cutting ability of the abrasive wheels, the tangential cutting force magnitude and the production rate of the grinding process. The results obtained prove the possibility of control and optimization of grinding by selecting particular dressing parameters.

Development of a mechanistic cutting force model for wavy-edge bull-nose helical end-milling of inconel 718 under emulsion cooling strategy

This paper presents the results of the development of a mechanistic cutting force model to predict cutting forces in high-speed end-milling of Inconel 718 using a wavy-edge, bull-nose, helical endmill (which hereafter will be abbreviated as WEBNHE). The model incorporates the effects of emulsion cooling strategy into the mechanistic cutting force model through the experimental determination of six specific cutting force and edge force coefficients. The cutting force is predicted as three components (Fx, Fy, and Fz) and the resultant cutting force FR. The mechanistic cutting force model depends on a mathematical model to represent the geometry of this endmill, which is also developed in this research. The mechanistic model also depends on three cutting force coefficients in the tangential, radial, and axial directions (ktc, krc, kac, respectively), and on three edge force coefficients (kte, kre, kae), also in the tangential, radial, and axial directions. These coefficients are determined experimentally in a separate work in which “emulsion” was applied as the cooling strategy. MATLAB codes were developed and used to simulate the developed mathematical and mechanistic cutting force models. Finally, to validate the mechanistic cutting force model, machining experiments were conducted and real cutting force components were measured and compared with the predicted cutting force components. The predicted values agree fairly well with the experimentally measured values in both magnitude and shape. The percentage of the prediction error for the highest peak force magnitudes at 93 rpm were 11.38%, –0.46%, and 11% for the Fx, Fy, and Fz components respectively, while the percentage prediction error for the lowest cutting force magnitudes are 15.25%, 17.84%, and 10% for Fx, Fy, and Fz components respectively. The developed mechanistic cutting force model can be used to investigate the effect of tool geometry and machining parameters on cutting forces, machining power, machine tool vibration, and to simulate the end-milling process to improve machinability and productivity, and also to understand more fully the end-milling process using WEBNHE.

Intelligent toolpath selection via multi-criteria optimization in complex sculptured surface milling

A new approach is presented the first time in the literature to generate multi-criteria optimized toolpaths for the complex sculptured surface machining. This is achieved by developing a mathematical solution that consists of the physical relationship between the mean resultant forces, cycle times and scallop heights. These three critical process outputs in machining are conflicting with each other. In other words, there are tradeoffs between cutting force magnitudes, cycle time and scallop height. This triple bounded problem in machining is solved in this article by using the objective weighting based algorithm. The multi-criteria toolpath optimization method introduced here for sculptured surface machining increases the controllability of the process with the specified criteria. The method also allows determining all pareto optimal solutions and all possible weights of each criteria. Moreover, the method eases to observe and analyze the trade-off between each criterion, facilitate the limitation and minimization of each criterion and determine corresponding toolpath for each solution. This solution produces optimized toolpaths according to preset constraints for mean cutting force, cycle time and scallop height. The method is a generalized solution for determining optimized toolpaths based on given constrains in free-form surface machining. In order to validate the multi-criteria toolpath optimization method, experiments at various conditions are performed on free-form machining and an example is presented in this article.

Processing and fiber content effects on the machinability of compression moulded random direction short GFRP composites

The random direction short Glass Fiber Reinforced Plastics (GFRP) have been prepared by two compression moulding processes, namely the Preform and Sheet Moulding Compound (SMC) processes. Cutting force analysis and surface characterization are conducted on the random direction short GFRPs with varying fiber contents (25∼40%). Edge trimming experiments are preformed using carbide inserts with varing the depth of cut and cutting speed. Machining characteristics of the Preform and SMC processed random direction short GFRPs are evaluated in terms of cutting forces, surface quality, and tool wear. It is found that composite primary processing and fiber contents are major contributing factors influencing the cutting force magnitudes and surface textures. The SMC composites show better surface finish over the Preform composites due to less delamination and fiber pullouts. Moreover, matrix damage and fiber protrusions at the machined edge are reduced by increasing fiber content in the random direction short GFRP composites.

Linear analysis of chatter vibration and stability for orthogonal cutting in turning

The productivity of high speed milling operations is limited by the onset of self-excited vibrations known as chatter. Unless avoided, chatter vibrations may cause large dynamic loads damaging the machine spindle, cutting tool, or workpiece and leave behind a poor surface finish. The cutting force magnitude is proportional to the thickness of the chip removed from the workpiece. Many researchers focused on the development of analytical and numerical methods for the prediction of chatter. However, the applicability of these methods in industrial conditions is limited, since they require accurate modelling of machining system dynamics and of cutting forces. In this study, chatter prediction was investigated for orthogonal cutting in turning operations. Therefore, the linear analysis of the single degree of freedom (SDOF) model was performed by applying oriented transfer function (OTF) and \ au decomposition form to Nyquist criteria. Machine chatter frequency predictions obtained from both forms were compared with modal analysis and cutting tests.

A new method for detecting tool wear and breakage in milling

In machining, tool condition monitoring (TCM) is one of the major trends of development of process efficiency. By monitoring tool wear and detecting tool-teeth break, TCM is able to protect tool, machine and workpiece, which corresponds to important savings. Cutting forces are often considered as the best indicator for detecting tool wear and damage, but they are very difficult and expensive to measure directly in industrial cases. The aim of this work is to develop a new method using standard transducers available on actual machines for a better monitoring of cutting process. This method analyses instantaneous variations in rotational frequency so as to observe milling operation. Experimental cutting tests were performed on a milling machine. On one hand, cutting forces were acquired through common dynamometer. On the other hand, signal from spindle integrated rotary encoder is acquired using specific angular-sampling methodology. Spindle rotational frequency is then easily computed using rudimentary signal processing tools. Correspondence between cutting force magnitude and variation in spindle rotational frequency is noted: when a tooth goes in material, cutting force suddenly increases, and rotational frequency starts to decrease until cutting force becomes low enough. Thus, apparition of tool wear can be observed by monitoring variations in rotational frequency according to the different teeth of the tool. Moreover, a sudden variation in the amplitude of slow-down due to a tooth allows detection of tooth breakage. Instantaneous variations in spindle rotational frequency are shown to be very effective indicators for tool condition in comparison with cutting force, so they must be very useful for TCM systems.

Characteristics of chip formation in micro V-grooving using elliptical vibration cutting

The chip and burr formation in micro V-grooving using elliptical vibration cutting (EVC) was investigated. Elliptical vibration of the cutting tool was achieved by employing two parallel piezoelectric actuators excited with two sinusoidal voltages of 90° phase difference. Changes in the shape of the chip and the cutting force, and the surface texture in micro V-grooving with EVC were investigated. It was observed that the reversal of the direction of the frictional force and the marked increase in the shear angle, which are two major characteristics of the EVC process, changed the shear flow inside the chip and reduced the cutting force, the chip thickness and the radius of curvature of the chip. When the excitation frequency of the tool was increased to an ultrasonic frequency of 65 kHz, more pronounced characteristics of EVC were observed. The cutting force in micro V-grooving with EVC at 65 kHz was reduced to approximately 10% of the cutting force magnitude under ordinary cutting. Low cutting force in the EVC process suppressed plastic deformation on the workpiece, thereby creating a micro V-groove free of burrs, which contributed to significant improvement in the form accuracy of a micro V-groove.

A passive adaptor to enhance chatter stability for end mills

A design procedure is suggested in this paper to enhance the chatter stability of an end mill cutter. Tool chatter is a well recognized self-excited vibration problem where the excitation force is the cutting force required to machine a workpiece. The cutting force magnitude is proportional to the thickness of the chip removed from the workpiece. The thickness of the chip, on the other hand, is affected by two distinct sets of events, namely, the instantaneous oscillations of the tip of the cutter and the undulations left on the surface from the earlier passes of the cutter. Hence, the excitation force, which is the cause of the oscillations, feeds on the oscillations. In this investigation, an end mill is simplified to be a beam cantilevered from a relatively rigid spindle. A local structural modification technique of the authors is then applied to this beam to suppress its proneness to excessive resonance vibrations. An add-on passive adaptor is developed for this purpose. Numerical simulations with random tip excitation and experimental verification with a scaled model are discussed. Suggested designs promise to enhance the chatter stability of a cantilevered cutter. Cutting tests are being planned for the next stage of work.

Mechanics of machining of face-milling operation performed using a self-propelled round insert milling cutter

There has been a renewed interest in the technology of rotary tools because of their ability to perform more productive machining and the concurrent evolution of a number of new ‘difficult-to-machine’ materials. This paper presents an investigation into the application of rotary tools in a face-milling operation. The work involved analysis of cutting forces and chip characteristics, and the development of analytical as well as conceptual models to predict the cutting forces. It was evident that the proposed model predicts cutting force magnitude with a fair accuracy.

Orthogonal cutting forces in juvenile and mature Pinus taeda wood

The distinct characteristics of juvenile and mature woods, which are observed particularly in softwoods, have an influence on processing due to their different mechanical resistance properties in relation to cutting operations. In the past, when most of the wood used industrially came from adult trees of natural forests, little importance was given to a distinction between different zones of the tree stem. At present, however, as the supply of mature trees with large diameters from native forests is constantly decreasing, the use of short-cycle trees has become a common practice, through the adoption of species that grow relatively fast, such as pines and eucalyptus. In both softwoods and hardwoods, juvenile wood cells are generally smaller and thinner than in mature wood, and this reflects on their density and mechanical resistance, which should have an effect on the cutting forces developed during processing. The main object of this research was to evaluate orthogonal cutting forces in juvenile and mature Pinus taeda woods. Cutting force magnitude differences were observed for those two regions of the trunk, with parallel cutting forces being 33.4% higher, on average, at the mature wood region for 90-0 cutting, and 12% higher for 90-90 cutting. This result is consistent with the distinct anatomical structures of the material, since the forces developed during machining depend directly upon its properties.

Influence of Consolidation Process on the Drilling Performance and Machinability of PIXA-M and PEEK Thermoplastic Composites

In this paper, the drilling performance of two composite systems, namely graphite-PIXA-M (PIXA-M) and graphite-PEEK (PEEK) induction heat-pressed thermoplastic composites, are compared with their counterpart from autoclave processing. Machinability is evaluated in terms of drilling forces and hole quality. Hole quality characteristics are evaluated in terms of geometric accuracy and surface finish. The experimental observations discuss unique chip characteristics during drilling both autoclaved and induction heat-pressed thermoplastic composites. The mechanism of material removal in drilling of thermoplastic composites is investigated through the further calculation of the specific cutting energy. The induction-processed composite material produced equivalent or better holes than the autoclave-processed composites although it required larger cutting force magnitudes and protruded fibers on the bottom ply are produced. The induction heat press may be a viable alternative for the processing of thermoplastic composites in terms of drilling performance.

Static and dynamic cutting force analysis when high speed rough milling hardened steel

Abstract This paper elucidates and compares the employment of up milling and down milling using static and dynamic cutting force and analysis of variance analysis in order to gain an in-depth understanding on its effects on tool life results obtained via the parametric study of alternative cutter path strategies when high speed milling hardened steel. The study further evaluates the three-dynamometer cutting force components in order to identify which component is the most sensitive to tool wear and cutting conditions applied. It was shown that as the cutter gradually wore out, comparison of the static normal force FY and resultant cutting forces between the milling orientation at all axial depths of cut showed that up milling gave a similar if not lower cutting force magnitude as compared to a down milling orientation. Static and dynamic cutting force analysis suggested that the FY is the most sensitive to tool wear and cutting conditions imposed.

Optimized feed scheduling in three axes machining. Part I: Fundamentals of the optimized feed scheduling strategy

An optimized feed scheduling strategy is proposed in this paper to maximize the metal removal rate in 3-axis machining while guaranteeing the machining accuracy. The tool path is assumed defined by a cubic parametric form. In part I of this paper, the fundamentals of this strategy are presented. This strategy integrates the feed drive dynamics, described by the acceleration/deceleration (Acc/Dec) profile, with the minimum-time trajectory planning in order to achieve the desired feed rate at the appropriate position. An optimum use of the feed drive capabilities is considered to track the changes in the cutting geometry along the tool path and to ensure an acceptable contour error. Therefore, this strategy combines different constraints and various criteria in modifying the feed rate to maintain a near-constant cutting force resulting in a highly non-linear problem. The constraints include the cutting force magnitude, the feed rate boundaries, the contour error and the characteristics of the (Acc/Dec) profile of the different feed drive systems. The criteria are the maximum production rate, the machining accuracy and safety. In part II of this paper, the effectiveness of this strategy is demonstrated using ball end mill operation on a workpiece that provides variable cutting geometry along a non-linear tool path. The performance of this strategy in terms of productivity, machining safety, and machining accuracy, is compared to a feed scheduling strategy based on control points as well as to milling with constant feed rate.

低速流れ形切削における応力,ひずみ分布

Under assumptions of isotropic hardening and equivalence of plastic work, the strain hardening slip-line theory is applied to analysis of a slip line field in slow speed, two-dimensional and flow-type machining, which is obtained by means of visioplasticity.The stress field obtained is almost compatible and consistent with boundary conditions except the boundary on back-surface of chip produced. The resultant cutting forces calculated on tool-face and second slip-lines, however, do not well coincide each other in magnitude although they do fairly well in direction and force acting point. The reason may be attributed to the assumption of equivalence of plastic work or the arising anisotropy.The analytical results in cutting force magnitude, coefficient of tool face friction and tool-chip contact length are verified to be in fairly good agreement with experimental results.While frictional stress along tool-face increases gradually toward cutting edge, saturating to the maximum shear stress value, the normal stress distribution is almost uniform or minor increasing toward the cutting edge. At the cutting edge, however, the normal stress showed a sudden drop, although this has been not yet ascertained in other examples.Normal stress distribution along lower boundary of the plastic field is almost similar to the P.L..B. Oxley's result except near cutting edge, where the normal stress is strongly compressive.