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  Subjects -> MANUFACTURING AND TECHNOLOGY (Total: 264 journals)
    - CERAMICS, GLASS AND POTTERY (25 journals)
    - MACHINERY (33 journals)
    - MANUFACTURING AND TECHNOLOGY (160 journals)
    - METROLOGY AND STANDARDIZATION (3 journals)
    - PACKAGING (13 journals)
    - PAINTS AND PROTECTIVE COATINGS (5 journals)
    - PLASTICS (25 journals)

MACHINERY (33 journals)

Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9)
Advanced Energy Materials     Hybrid Journal   (Followers: 16)
Applied Mechanics Reviews     Full-text available via subscription   (Followers: 26)
BER : Consumer Goods Industries Survey     Full-text available via subscription  
BER : Intermediate Goods Industries Survey     Full-text available via subscription   (Followers: 1)
BER : Manufacturing Survey : Full Survey     Full-text available via subscription   (Followers: 2)
CORROSION     Full-text available via subscription  
Electric Power Components and Systems     Hybrid Journal   (Followers: 6)
Engenharia AgrĂ­cola     Open Access  
Foundations and Trends® in Electronic Design Automation     Full-text available via subscription  
High Temperature Materials and Processes     Full-text available via subscription   (Followers: 4)
International Journal of Machine Tools and Manufacture     Hybrid Journal   (Followers: 4)
International Journal of Machining and Machinability of Materials     Hybrid Journal   (Followers: 5)
International Journal of Manufacturing Technology and Management     Hybrid Journal   (Followers: 7)
International Journal of Precision Technology     Hybrid Journal  
International Journal of Rapid Manufacturing     Hybrid Journal   (Followers: 1)
International Journal of Rotating Machinery     Open Access   (Followers: 1)
ISRN Mechanical Engineering     Open Access   (Followers: 5)
Journal of Machinery Manufacture and Reliability     Hybrid Journal  
Journal of Machinery Manufacturing and Automation     Open Access   (Followers: 1)
Journal of Mechanics     Hybrid Journal   (Followers: 16)
Journal of Strain Analysis for Engineering Design     Hybrid Journal   (Followers: 5)
Journal of Terramechanics     Hybrid Journal   (Followers: 1)
Machine Design     Partially Free   (Followers: 10)
Machines     Open Access  
Materials     Open Access   (Followers: 5)
Mechanics Based Design of Structures and Machines: An International Journal     Hybrid Journal   (Followers: 2)
Micromachines     Open Access   (Followers: 2)
Practical Machinery Management for Process Plants     Full-text available via subscription  
Pump Industry Analyst     Full-text available via subscription  
Russian Engineering Research     Hybrid Journal  
Sensor Review     Hybrid Journal   (Followers: 1)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 5)
Journal Cover International Journal of Machine Tools and Manufacture     [SJR: 2.724]   [H-I: 71]
   [6 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0890-6955
   Published by Elsevier Homepage  [2582 journals]
  • Model Predictive Control to Mitigate Chatters in Milling Processes with
           Input Constraints
    • Abstract: Publication date: Available online 13 January 2015
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Hai-Tao Zhang , Yue Wu , Defeng He , Huan Zhao
      Due to the rigidity-flexibility coupling and self-excitation mechanism, chatters are often encountered in machining processes. They severely limit the productive capacity of machine tools, and lead to inferior work piece quality, cutting disturbances and quick tool wear. In recent years, the increasing industrial demand of high quality and high efficiency machining motivates us to develop a niche active control method to mitigate the chatter dynamics with input constraints. In this work, an active model predictive control (MPC) method for the milling process is developed such that the chatter-free domain of stable operation is substantially enlarged and a higher efficiency can be thus achieved. Therein, the complex perturbation dynamics including time-delay and periodical excitation is transformed into a linear time-varying (LTI) system, and afterwards both model-based prediction and receding horizon optimization are implemented by the proposed MPC scheme to address the system uncertainties and input constraints to guarantee the chatter-free stability and feasibility. Effectiveness and superiority of the proposed MPC are finally demonstrated by means of illustrative examples.


      PubDate: 2015-01-23T16:30:20Z
       
  • Spindle speed ramp-up test: A novel experimental approach for chatter
           stability detection
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): N. Grossi , A. Scippa , L. Sallese , R. Sato , G. Campatelli
      Chatter is one of the most limiting factors in improving machining performances. Stability Lobe Diagram (SLD) is the most used tool to select optimal stable cutting parameters in order to avoid chatter occurrence. Its prediction is affected by reliability of input data such as machine tool dynamics or cutting coefficients that are difficult to be evaluated accurately, especially at high speed. This paper presents a novel approach to experimentally evaluate SLD without requiring specific knowledge of the process; this approach is called here Spindle Speed Ramp-up (SSR) test. During this test spindle speed is ramped up, and chatter occurrence is detected by the Order Analysis technique. As result one single test ensures optimal spindle speed identification at one cutting condition, while if few tests are performed the entire SLD could be obtained. Results of the method applied to slotting operation on aluminum are provided and a comparison between different measurements devices is presented. This quick, easy-to-use and efficient test is suitable for industrial application: no knowledge of the process is required, different sensors can be used such as accelerometer, dynamometer or microphone.


      PubDate: 2015-01-23T16:30:20Z
       
  • Modeling the mechanics and dynamics of arbitrary edge drills
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): K. Ahmadi , A. Savilov
      This paper presents a new approach for modelling the cutting forces and chatter stability limits in drills with arbitrary lip geometry. The oblique cutting geometry at each point on the drill lip is modelled using parametric curve equations. The cutting force and process damping coefficients at different parts of the drill lip are identified empirically; the cutting force coefficients are identified from non-symmetric drilling tests, and the process damping coefficients are identified from chatter-free orthogonal turning tests. The presented approach provides a practical method for modelling the cutting forces and vibration stability without needing the detailed geometry of drill lips. The accuracy of presented model in predicting lateral and torsional-axial chatter stability limits is verified by conducting drilling tests using drills with various edge geometries.


      PubDate: 2015-01-23T16:30:20Z
       
  • Influences of chip serration on micro-topography of machined surface in
           high-speed cutting
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Guosheng Su , Zhanqiang Liu , Liang Li , Bing Wang
      Saw-tooth chip changes from macroscopically continuous ribbon to separated segments with the increase of cutting speed. The aim of this study is to find the correlations between chip morphology and machined surface micro-topography at different chip serration stages encountered in high speed cutting. High strength alloy steel AerMet100 was employed in orthogonal cutting experiments to obtain chips at different serration stages and corresponding machined surfaces. The chips and machined surfaces obtained were then examined with optical microscope (OM), scanning electron microscope (SEM), and white light interferometer (WLI). The result shows that chip serration causes micro-waves on machined surface, which increases machined surface roughness. However, wave amplitudes (surface roughness) at different serration stages are different. The principal factor influencing wave amplitude is the thickness of the sawed segment (tooth) of saw-tooth chip. With cutting parameters in this study, surface roughness contributed by chip serration ranges from 0.39μm to 1.85μm. This may bring on serious problems in the case of trying to replace grinding with high-speed cutting in rough machining. Some suggestions have been proposed to control the chip serration-caused surface roughness in high-speed cutting based on the results of the current study.


      PubDate: 2015-01-23T16:30:20Z
       
  • The influence of speed on material removal mechanism in high speed
           grinding with single grit
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Lin Tian , Yucan Fu , Jiuhua Xu , Haiyan Li , Wenfeng Ding
      In this paper, the effect of speed on material removal was investigated by single grit grinding of the GH4169 super alloy which is difficult to machine, with a new test method. During the tests the whole material removal process, was observed and then the critical thickness of chip formation was quantitatively analyzed. In order to provide insight into the speed effect, the grinding forces, chip formation and pile-up ratio were investigated. It was found that the stages of material removal process changed with the grinding speed, and the graphical relationships between grinding speed and the critical thickness of chip formation, grinding forces and the pile-up ratio were found to have a common characteristic, namely a common turnover point which was about 100m/s. This trend in the results is attributed to alternating predominance between the strain hardening and thermal softening effects. The results of this study demonstrated that the grinding speed has a significant impact on material removal mechanism, and also provide a basis for sound understanding of the high speed grinding process of difficult to cut materials.


      PubDate: 2015-01-23T16:30:20Z
       
  • Identification and compensation of geometric errors of rotary axes on
           five-axis machine by on-machine measurement
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Qingzhen Bi , Nuodi Huang , Chao Sun , Yuhan Wang , Limin Zhu , Han Ding
      The geometric errors of rotary axes are the fundamental errors of a five-axis machine tool. They directly affect the machining accuracy, and require periodical measurement, identification and compensation. In this paper, a precise calibration and compensation method for the geometric errors of rotary axes on a five-axis machine tool is proposed. The automated measurement is realized by using an on-the-machine touch-trigger technology and an artifact. A calibration algorithm is proposed to calibrate geometric errors of rotary axes based on the relative displacement of the measured reference point. The geometric errors are individually separated and the coupling effect of the geometric errors of two rotary axes can be avoided. The geometry error of the artifact as well as its setup error has little influence on geometric error calibration results. Then a geometric error compensation algorithm is developed by modifying the numeric control (NC) source file. All the geometric errors of the rotary errors are compensated to improve the machining accuracy. The algorithm can be conveniently integrated into the post process. At last, an experiment on a five-axis machine tool with table A-axis and head B-axis structure validates the feasibility of the proposed method.


      PubDate: 2015-01-23T16:30:20Z
       
  • Accuracy enhancement of five-axis machine tool based on differential
           motion matrix: Geometric error modeling, identification and compensation
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Guoqiang Fu , Jianzhong Fu , Yuetong Xu , Zichen Chen , Jintao Lai
      This paper presents the precision enhancement of five-axis machine tools according to differential motion matrix, including geometric error modeling, identification and compensation. Differential motion matrix describes the relationship between transforming differential changes of coordinate frames. Firstly, differential motion matrix of each axis relative to tool is established based on homogenous transformation matrix of tool relative to each axis. Secondly, the influences of errors of each axis on accuracy of tool are calculated with error vector of each axis. The sum of these influences is integration of error components of machine tool in coordinate system of tool. It endows the error modeling clear physical meaning. Moreover, integrated error components are transformed to coordinate frame of working table for integrated error transformation matrix of machine tools. Thirdly, constructed Jacobian is established using differential motion matrix of each axis without extra calculation to compensate the integrated error components of tool. It makes compensation easy and convenient with reuse of intermediate. Fourthly, six-circle method of ballbar is developed based on differential motion matrix to identify all ten error components of each rotary axis. Finally, the experiments are carried out on SmartCNC500 five-axis machine tool to testify the effectiveness of proposed accuracy enhancement with differential motion matrix.


      PubDate: 2015-01-23T16:30:20Z
       
  • Integral design of contour error model and control for biaxial system
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Jianhua Wu , Zhenhua Xiong , Han Ding
      This paper focuses on the contour following accuracy improvement for biaxial systems using cross-coupled control (CCC). It proposes an integral design method including contour error model, contour control effort distribution and the CCC algorithm. First, a contour error model using the contour algebraic equation and its partial derivatives is established without the small tracking error assumption. This model satisfies the condition that it equals to zero if and only if the real contour error value vanishes, which makes perfect contour following become possible in theory. Then, in order to decouple the contour following the feed-direction tracking, contour control effort distribution is decided to be in line with the normal vector at the desired point. Through expanding the proposed contour error model with Taylor series to make it be related to tracking errors of both axes, the stability condition of CCC is analyzed by the contour error transfer function (CETF). Experiments are carried out on an X–Y motion stage to verify the proposed method. The results show that it improves the contour following accuracy greatly in various conditions, even when large tracking errors occur.


      PubDate: 2015-01-23T16:30:20Z
       
  • A method of testing position independent geometric errors in rotary axes
           of a five-axis machine tool using a double ball bar
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Xiaogeng Jiang , Robert J. Cripps
      Ensuring that a five-axis machine tool is operating within tolerance is critical. However, there are few simple and fast methods to identify whether the machine is in a “usable” condition. This paper investigates the use of the double ball bar (DBB) to identify and characterise the position independent geometric errors (PIGEs) in rotary axes of a five-axis machine tool by establishing new testing paths. The proposed method consists of four tests for two rotary axes; the A-axis tests with and without an extension bar and the C-axis tests with and without an extension bar. For the tests without an extension bar, position errors embedded in the A- and C-axes are measured first. Then these position errors can be used in the tests with an extension bar, to obtain the orientation errors in the A- and C-axes based on the given geometric model. All tests are performed with only one axis moving, thus simplifying the error analysis. The proposed method is implemented on a Hermle C600U five-axis machine tool to validate the approach. The results of the DBB tests show that the new method is a good approach to obtaining the geometric errors in rotary axes, thus can be applied to practical use in assembling processes, maintenance and regular checking of multi-axis CNC machine tools.


      PubDate: 2015-01-23T16:30:20Z
       
  • Position geometric error modeling, identification and compensation for
           large 5-axis machining center prototype
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Gaoyan Zhong , Chaoqun Wang , Shoufeng Yang , Enlai Zheng , Yanyan Ge
      This paper presents a position geometric error modeling, identification and compensation method for large 5-axis machining center prototype. First, regarding the prototype as a rigid multi-body system, a geometric error model has been established, which supports the identification of position geometric error associated with a translational axis by using laser interferometer, and a rotational axis by using laser tracker. Second, based on this model, an improved identification approach named as virtual rigid-body is put forward for calculating positioning error of each large translational axis. Detailed derivation of a generalized matrix equation is given. Third, analytical models based on the least-squares theory were adopted to compute error values at an arbitrary position for error compensation. Finally, the identified position geometric errors were compensated by using recursive software-based error compensation method. The results show that the position accuracy of large machining center prototype has been improved with compensation and up to the design requirements.


      PubDate: 2015-01-23T16:30:20Z
       
  • Assessment of spray quality from an external mix nozzle and its impact on
           SQL grinding performance
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): S. Shiva Sai , K. ManojKumar , A. Ghosh
      Spray quality is the critical factor which decides the efficacy of Small Quantity Lubrication (SQL) technology in a high specific energy involved machining process like grinding. Yet, the understanding about spray quality, the actual process mechanics and its effect on machining performance is inadequate. The present work is an attempt to establish a correlation between the spray input variables, quality of the spray and machining performance of SQL grinding through modelling and experiments. Using computational fluid dynamic techniques, the variation of droplet size, droplet velocity, number of droplets and heat transfer coefficient have been analysed at different input parameters and the computed trends have been verified and validated. CFD modelling of spray indicates that it is possible to produce aerosol medium with high heat dissipation ability at moderately high air pressure and low flow rate. It also shows that any increase in atomising air pressure favourably leads to notable increase in wetting area and also results in substantial enhancement in heat dissipation ability. Reduction of residual stress is thus remarkably good. On the other hand, grinding fluid flow rate, if increased, offers significantly better lubricity and reduces the grinding force which also reduces tensile residual stress. Short spell grinding test results are found to be in good agreement with CFD results.


      PubDate: 2015-01-23T16:30:20Z
       
  • 1-Shot hot stamping of ultra-high strength steel parts consisting of
           resistance heating, forming, shearing and die quenching
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Ken-ichiro Mori , Tomoyoshi Maeno , Hiroaki Yamada , Hayato Matsumoto
      A 1-shot hot stamping process consisting of resistance heating, forming, shearing and die quenching was developed to produce small- and medium-size ultra-high strength steel parts. A rectangular sheet was resistance-heated to obtain a uniform distribution of temperature, and just after the end of heating, a sequence of forming, shearing and die quenching was performed by one shot to prevent the drop in temperature. An ultra-high strength steel spur gear having a hardness of 540 HV2 was produced by 1-shot hot stamping composed of heating, blanking and die quenching. The rollover was improved by partial compression of the blanked gear. An ultra-high strength stainless steel part having a hardness of 580 HV2 was produced by 1-shot hot stamping consisting of the heating, bending, shearing and die quenching, and no springback and quenching distortion of the produced part were observed by holding at the bottom dead centre of the press. An operation for thickening the edge of the punched hole was included in 1-shot hot stamping to improve the strength of a product.


      PubDate: 2015-01-23T16:30:20Z
       
  • The estimation of cutting forces and specific force coefficients during
           finishing ball end milling of inclined surfaces
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Szymon Wojciechowski
      The majority of cutting force models applied for the ball end milling process includes only the influence of cutting parameters (e.g. feedrate, depth of cut, cutting speed) and estimates forces on the basis of coefficients calibrated during slot milling. Furthermore, the radial run out phenomenon is predominantly not considered in these models. However this approach can induce excessive force estimation errors, especially during finishing ball end milling of sculptured surfaces. In addition, most of cutting force models is formulated for the ball end milling process with axial depths of cut exceeding 0.5mm and thus, they are not oriented directly to the finishing processes. Therefore, this paper proposes an accurate cutting force model applied for the finishing ball end milling, which includes also the influence of surface inclination and cutter's run out. As part of this work the new method of specific force coefficients calibration has been also developed. This approach is based on the calibration during ball end milling with various surface inclinations and the application of instantaneous force signals as an input data. Furthermore, the analysis of specific force coefficients in function of feed per tooth, cutting speed and surface inclination angle was also presented. In order to determine geometrical elements of cut precisely, the radial run out was considered in equations applied for the calculation of sectional area of cut and active length of cutting edge. Research revealed that cutter's run out and surface inclination angle have significant influence on the cutting forces, both in the quantitative and qualitative aspect. The formulated model enables cutting force estimation in the wide range of cutting parameters, assuring relative error's values below 16%. Furthermore, the consideration of cutter's radial run out phenomenon in the developed model enables the reduction of model's relative error by the 7% in relation to the model excluding radial run out.


      PubDate: 2015-01-23T16:30:20Z
       
  • Machining of hardened steel—Experimental investigations, performance
           modeling and cooling techniques: A review
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Satish Chinchanikar , S.K. Choudhury
      The researchers have worked on many facets of machining of hardened steel using different tool materials and came up with their own recommendations. Researchers have tried to investigate the effects of cutting parameters, tool materials, different coatings and tool geometry on different machinability aspects like, the tool life, surface roughness, cutting forces, chip morphology, residual stresses and the tool–chip interface temperature under dry and/or semi-dry and/or flood cooling environment during machining of hardened steels while many of them have ventured to characterize the wear phenomenon. Good amount of research has been performed on an analytical and/or numerical and/or empirical modeling of the cutting forces, tool–chip interface temperature, and tool wear under orthogonal/oblique cutting conditions during machining of hardened steels. This paper presents a comprehensive literature review on machining of hardened steels using coated tools, studies related to hard turning, different cooling methods and attempts made so far to model machining performance(s) so as to give proper attention to the various researcher works.


      PubDate: 2015-01-23T16:30:20Z
       
  • Geometric prediction of conic tool in micro-EDM milling with fix-length
           compensation using simulation
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Lenan Zhang , Jianyi Du , Xiaoshun Zhuang , Zhiliang Wang , Jingyu Pei
      Micro-EDM milling is an effective machining process for three-dimensional micro-cavity of high hardness materials. However, tools wear sharply in micro-milling, thus several compensation methods are applied. The present study examines the fix-length compensation method, and the initial experiments show that a cone-shaped tool end is formed with this compensation method. Because the cone angle is of great importance in the determination of the fix-length compensation parameters in the machining procedure, a clear explanation of the forming mechanism and precise prediction are of great necessity. First, the tool and the workpiece were geometrically and mathematically modeled as two-dimensional matrices. Second, the machining process was divided into three parts including sparking, horizontal feeding and vertical feeding. Finally, a series of experiments were conducted in order to verify the accuracy of the simulation. The results show that the relative error of the simulation compared to the experimental data is within 4% under most machining conditions. The developed model can thus be used to predict the machined surface of the tool and the workpiece and can also provide a better understanding for the mechanism of the cone shaped tool end.


      PubDate: 2015-01-23T16:30:20Z
       
  • Modeling and experimental investigation of gas film in
           micro-electrochemical discharge machining process
    • Abstract: Publication date: March 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 90
      Author(s): Baoyang Jiang , Shuhuai Lan , Kevin Wilt , Jun Ni
      Electrochemical discharge machining (ECDM) is a promising machining technology that effectively machines non-conducting and brittle materials, featuring good material removal rate, flexibility, and accuracy of machining. ECDM makes use of the electrochemical discharge phenomenon to trigger the discharging by the gas film surrounding the tool electrode. As the fundamental of electrochemical discharging, gas film is essential to the machining quality and efficiency. However, modeling of gas film in electrochemical reaction is not well established. This paper presents analytical modeling of the gas film, involving bubble growth and departure on electrode, gas film evolution, and electrolysis characteristics. Experiments were carried out to compare models to the actual discharging phenomenon. High speed camera imaging demonstrated the formation of a gas film on the tool electrode. The range of thickness of gas film found in experiments indicated good consistency with the range of film thickness estimated from analytical models. Experiments on critical voltages and currents further revealed the characteristics of the gas film in electrochemical reaction.


      PubDate: 2015-01-23T16:30:20Z
       
  • Energy aspects and workpiece surface characteristics in
           ultrasonic-assisted cylindrical grinding of alumina–zirconia
           ceramics
    • Abstract: Publication date: March 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 90
      Author(s): Ali Zahedi , Taghi Tawakoli , Javad Akbari
      Ultrasonic assisted grinding is a novel method for improving the grinding process of difficult-to-cut materials. In the present research a novel setup has been designed and manufactured for utilizing ultrasonic vibrations in external cylindrical grinding. The designed ultrasonic head vibrates a rotating workpiece in axial direction. An alumina–zirconia ceramic (AZ90) has been selected as the workpiece material. Energy aspects and workpiece surface characteristics of ultrasonic assisted cylindrical grinding (UACG) and conventional cylindrical grinding (CG) processes have been analytically modeled and corresponding grinding experiments have been performed. The combined kinematics of the cylindrical plunge grinding process and axial ultrasonic vibrations provide a unique surface treatment conditions, which leads to reduced peak heights and increased valley depths of the surface topography. The main axial vibration mode provides the overlap of the adjacent cutting traces and consequently smoothens the surface topography in cylindrical plunge grinding. It has been analytically and experimentally shown that, applying ultrasonic vibrations, grinding energy can be reduced up to more than 35% depending on the process parameters. The surface characteristics of the ground workpieces have been investigated in terms of four surface roughness parameters and the roundness error.


      PubDate: 2015-01-23T16:30:20Z
       
  • The interactive effects on deformation behavior in laser thermal
           adjustment of two-bridge actuators
    • Abstract: Publication date: March 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 90
      Author(s): Hong Shen , Jun Hu , Zhenqiang Yao
      Laser thermal adjustment of two-bridge actuators by heating one bridge attracts much attention. However, the interactive influence of heating two bridges on the in-plane and out-of-plane deformations of actuators has not been explored. In this study, a 3D thermo-mechanical analysis is conducted to study the laser thermal adjustment of actuators under heating two bridges. The effects of the time gap between the heating two bridges on temperature, stress distribution and deformation behavior are investigated. The results show that there are some interactions between stress and temperature in the two heating bridges, which can significantly affect the deformations of actuators. To validate the present numerical model experimental work is also performed and reported in the paper.


      PubDate: 2015-01-23T16:30:20Z
       
  • Time domain prediction of milling stability according to cross edge
           radiuses and flank edge profiles
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Jeong Hoon Ko
      This article proposes a time domain model for predicting an end milling stability considering process damping caused by a variety of cross edge radiuses and flank profiles. The time domain model of calculating indentation areas, as well as regenerative dynamic uncut chips, is formulated for the prediction of the stabilizing effect induced by interference areas between the edge profiles and undulation left on a workpiece. The interference area generates forces against the vibration motion, which acts as a damping effect. In the model, the present and previous angular position of cross radiuses and flank edge profiles are located to calculate the dynamic uncut chip as well as indentation area based on a time history of the dynamic cutter center position. The phenomenon that chatter is damped according to cross edge radiuses and flank edge profiles is successfully simulated with the proposed dynamic model and validated through the extensive experimental tests.


      PubDate: 2015-01-23T16:30:20Z
       
  • In-process tool point FRF identification under operational conditions
           using inverse stability solution
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): O. Özşahin , E. Budak , H.N. Özgüven
      Self-excited vibrations of machine tools during cutting result in process instability, poor surface finish and reduced material removal rate. In order to obtain stability lobe diagrams to avoid chatter vibrations, tool point frequency response function (FRF) must be determined. In classical machine tool studies, tool point FRF is obtained experimentally or analytically for the idle state of the machine. However, during cutting operations, discrepancies are frequently observed between the stability diagrams predicted by using the FRFs measured at the idle state and the actual stability of the process. These deviations can be attributed to the changes in machine tool dynamics under cutting conditions which are difficult to measure. In this study, a new identification method is proposed for the identification of in-process tool point FRFs. In this method, experimentally determined chatter frequency and corresponding axial depth of cut are used in order to identify tool point FRF. The proposed method is applied to a real machining center and by using chatter tests it is demonstrated that the tool point FRF can be accurately identified under operational conditions.


      PubDate: 2015-01-23T16:30:20Z
       
  • Effect of grinding-induced cyclic heating on the hardened layer generation
           in the plunge grinding of a cylindrical component
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Mei Liu , Thai Nguyen , Liangchi Zhang , Qiong Wu , Dale Sun
      This paper discusses the effects of the grinding-induced cyclic heating on the properties of the hardened layer in a plunge cylindrical grinding process on the high strength steel EN26. It was found that a multi-pass grinding brings about a uniform and continuous hardened layer along the circumference of the cylindrical workpiece. An increase of the number of grinding passes, leads to a thicker layer of hardening, a larger compressive residual stress and a deeper plastic deformation zone. Within the plastic deformation zone, the martensitic grains are refined by the thermo-mechanical loading, giving rise to a hardness of 12.5% higher than that from a conventional martensitic transformation. The coupled effects of heat accumulation and wheel wear in the multi-pass grinding are the main causes for the thickening of the hardened layer. A too small infeed per workpiece revolution would result in insufficient grinding heat, and in turn, bring about an undesirable tempered hardened layer and a reduction of its hardness.


      PubDate: 2015-01-23T16:30:20Z
       
  • Size effect and minimum chip thickness in micromilling
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Fernando Brandão de Oliveira , Alessandro Roger Rodrigues , Reginaldo Teixeira Coelho , Adriano Fagali de Souza
      This paper compares the size effect behaviour in micro- and macromilling by applying Analysis of Variance on the specific cutting force (k c) and relating it with the tool edge radius (r e), workpiece roughness (R a), cutting force and chip formation when cutting slots in AISI 1045 steel. Size effect is observed in micromilling through hyper-proportional increase of the specific cutting force for feeds per tooth (f) lower than endmill edge radius, reaching levels of grinding process (∼70GPa) when f≅r e/10. This particular milling condition does not produce chips. The minimum uncut chip thickness (h min) varied between 22% and 36% of the endmill edge radius. This range was determined by proposing a curve (k c/R a versus f/r e) where specific cutting force becomes amplified (size effect) due to workpiece roughness association. In addition to the minimum uncut chip thickness, there is a cutting thickness between h min and r e that optimizes workpiece surface integrity and not only forms the chip completely. This thickness may be as important as h min. Besides this, a relation between deformation mechanisms during chip formation and cutting force oscillations is proposed for micromilling and also related to tool tip radius (r ε). This cutting force behaviour enables the determination of certain characteristic chip thicknesses including h min. Finally, it is concluded that minimum uncut chip thickness varies practically from 1/4 to 1/3 of tool cutting edge, regardless of workpiece material, tool geometry, mechanical machining process and technique used for measuring or estimating h min, i.e. numerical, analytical or experimental.
      Graphical abstract image

      PubDate: 2015-01-23T16:30:20Z
       
  • On ultrasonic assisted abrasive flow finishing of bevel gears
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): G. Venkatesh , Apurbba Kumar Sharma , Pradeep Kumar
      Finishing of bevel gears is an important requirement in many machining shop floors. Variants of abrasive flow machining (AFM) could be plausible solutions for finishing such parts with intricate geometries. In the present work, a relatively new variant of AFM called ultrasonically assisted abrasive flow machining (UAAFM) technique was employed to finish bevel gears made of EN8 steel. An analysis of the process has been presented with suitable illustrations. A finite element simulation of the behavior of the medium during finishing of bevel gears using the UAAFM process has been presented. A 3D model was constructed to simulate the flow of medium through the outer wall of the gear tooth surface using computational fluid dynamics (CFD) approach. The velocity, pressure and temperature values along the length of the workpiece were computed for both UAAFM and the conventional AFM processes. Further, the effectiveness of the process was investigated through experimental trials by conducting a comparison study between classical AFM and UAAFM. Ultrasonic frequency, extrusion pressure, processing time and the media flow rate were considered as the input variables while improvements in surface finish and material removal were considered as the monitored outputs. Results confirm that improvements in surface roughness and material removal are significantly higher than those obtained with conventional abrasive flow machining. The study further reveals that, the applied high frequency (ultrasonic) vibration to the workpiece has the maximum influence on the process responses among the variables considered.


      PubDate: 2015-01-23T16:30:20Z
       
  • Real-time tool wear monitoring in milling using a cutting condition
           independent method
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): Mehdi Nouri , Barry K. Fussell , Beth L. Ziniti , Ernst Linder
      This paper describes a new method to monitor end milling tool wear in real-time by tracking force model coefficients during the cutting process. The behavior of these coefficients are shown to be independent from the cutting conditions and correlated with the wear state of the cutting tool. The tangential and radial force model coefficients are normalized and combined into a single parameter for wear monitoring. A number of experiments with different workpiece materials are run to investigate the feasibility of tool wear monitoring using this method. We show that this method can be used in real-time to track tool wear and detect the transition point from the gradual wear region to the failure region in which the rate of wear accelerates.


      PubDate: 2015-01-23T16:30:20Z
       
  • Laser ablation of titanium alloy under a thin and flowing water layer
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): V. Tangwarodomnukun , P. Likhitangsuwat , O. Tevinpibanphan , C. Dumkum
      Underwater laser ablation has become an alternative machining process that is able to reduce the thermal damage in work materials caused by lasers. However, the disturbance of water to the laser beam is a crucial concern for the ablation performance in water and cut surface quality obtained. In this study, a new laser ablation technique has been proposed, in which a waterjet was applied to impinge the top workpiece surface in order to form a thin and flowing water layer. With the assist of such water layer during the laser ablation, the redeposition and heat-affected zone can be minimized. Titanium alloy (Ti–6Al–4V) selected as a work sample was grooved by using a nanosecond-pulse laser under different machining conditions. The cut geometry and heat-affected zone were observed and analyzed to justify the process performance. The metallurgical change and cracks that occurred on and underneath the groove surface were also investigated in this study. The experimental results revealed that a clean cut with less thermal damage can be obtained when the workpiece was ablated by a laser under the flowing water layer. In addition, a narrower and deeper groove can be fabricated when a higher waterjet flow rate was applied. The laser ablation under the flowing water layer developed in this study could be a potential method for machining titanium alloy or even other thermal-sensitive materials.
      Graphical abstract image

      PubDate: 2015-01-23T16:30:20Z
       
  • Editorial
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89
      Author(s): T.A. Dean



      PubDate: 2015-01-23T16:30:20Z
       
  • IFC - Editorial board
    • Abstract: Publication date: February 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 89




      PubDate: 2015-01-23T16:30:20Z
       
  • A method for stiffness tuning of machine tool supports considering contact
           stiffness
    • Abstract: Publication date: March 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 90
      Author(s): Daisuke Kono , Syuya Nishio , Iwao Yamaji , Atsushi Matsubara
      A methodology for tuning the stiffness of machine tool supports is described based on a stiffness model using the contact stiffness approach. Using this model, the mathematical relationship between the load of the support and its stiffness is established. The relationship is separated into three regions. When the total stiffness of all supports is maximized, the load must be tuned so that the stiffness–support load relationship is in the critical region, whereby the contact stiffness is slightly larger than the bulk stiffness. Correspondingly, a placement method of supports is proposed that increases their stiffness without anchor bolts. The effectiveness of the proposed method is verified in two experiments. In the first experiment, the natural frequency of a small machine tool prototype is compared for several placements of three supports. The lowest natural frequency of the machine tool under the proposed placement scheme is maximized. In the second experiment, the proposed method is applied to increase the lowest natural frequency of a horizontal milling machine. The lowest natural frequency with a distinct arrangement of three supports is increased by 15–55%, compared to other popular placements of these three supports. The experimental results show that the proposed placement method is effective for enhancing the stiffness of machine tool supports.


      PubDate: 2015-01-23T16:30:20Z
       
  • Vibration frequencies in stable and unstable milling
    • Abstract: Publication date: March 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 90
      Author(s): Mahdi Eynian
      Vibration frequencies in machining may be employed for calculation of natural frequencies of the dominant modes in chatter and selection of chatter-free spindle speeds with large material removal rates. In this approach, it is important to investigate the relationship between the vibration frequencies, the natural frequencies, spindle speeds and depth of cuts for both stable and unstable cutting conditions. In this paper, the dominant poles of the closed loop time delay differential equation of a milling operation are calculated by successive sectioning of the complex plane and using Cauchy's argument principle. Vibration frequency and damping ratio of the closed loop machining system for each cutting condition is calculated based on the position of the dominant pole on the complex plane which provides 3D plots of the vibration frequency and closed loop damping ratio over any range of depth of cuts and spindle speeds. Finally, the findings of the analytical approach are compared to a machining experiment and a time domain simulation and differences and similarities in their predictions are discussed.
      Graphical abstract image

      PubDate: 2015-01-23T16:30:20Z
       
  • An integrated prediction model including the cutting process for virtual
           product development of machine tools
    • Abstract: Publication date: March 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 90
      Author(s): Chang-Ho Lee , Min-Yang Yang , Chang-Won Oh , Tae-Weon Gim , Jae-Yong Ha
      Recently activities for shortening the development time of machine tools and demands for high-value products are consistently being increased. As a result, many studies for predicting the performance in design stage have been conducted to solve these issues. So far, most manufacturers of machine tools have verified designs excluding the cutting process, even though the main performance is the machining quality of the workpiece. Therefore, it has been required to consider together the cutting process model for analyzing the machining quality before the manufacturing of the prototype. This paper presents an integrated dynamic model considering the all interaction of the machine structure, the control system, and the cutting process. The modal truncation technique using the steady-state dynamic analysis in a selected location and frequency range of interest is applied to increase the efficiency of mechatronics simulations including the cutting process. In particular, this proposed prediction model allows accurate design verifications for high-speed machines because it reflects the influences of the high inertia forces and the contour errors caused by high feed rate. Several peripheral milling applications were demonstrated in order to show the feasibility of the proposed prediction model, and we confirmed the superiority of prediction by comparing the simulated and measured results in high feed milling.


      PubDate: 2015-01-23T16:30:20Z
       
  • The effect of the welding parameters and tool size on the thermal process
           and tool torque in reverse dual-rotation friction stir welding
    • Abstract: Publication date: April 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 91
      Author(s): L. Shi , C.S. Wu , H.J. Liu
      Reverse dual-rotation friction stir welding (RDR-FSW) is a novel variant of conventional friction stir welding (FSW) process. The key feature is that the tool pin and the assisted shoulder are separated and rotate reversely and independently during welding process, thus it has great potential to improve the weld quality and lower the welding loads through adjusting the rotation speeds of the tool pin and the assisted shoulder independently. A 3D model of RDR-FSW process is developed to analyze the effect of welding parameters and tool size on the thermal process and the tool torque quantitatively. The model considers the effect of the welding parameters on the dimensionless slip rate and the friction coefficient between the tool-workpiece contact interfaces. It is found that with an increase of the radial distance, the locations of peak and valley values of heat generation rate at the shoulder-workpiece contact interfaces vary from the retreating side (RS) to the advancing side (AS) and from the AS to the RS, respectively. Although the reverse rotation of the tool pin and the assisted shoulder has little effect on the total heat generation, the corresponding material flow pattern and the distribution of heat generation rate lead to a more homogeneous temperature distribution and a much lower torque exerted on the workpiece in RDR-FSW process. The model is experimentally validated by comparing the measured thermal cycles with the calculated data.


      PubDate: 2015-01-23T16:30:20Z
       
  • Effect of grinding wheel spindle vibration on surface roughness and
           subsurface damage in brittle material grinding
    • Abstract: Publication date: Available online 9 January 2015
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Jianbin Chen , Qihong Fang , Ping Li
      The external interference and vibration can seriously affect the machining errors in brittle materials grinding process. This paper proposes a new model to analyze the relationship between surface roughness (SR) and subsurface damage (SSD) depth on the basis of grinding kinematics analysis and indentation fracture mechanics of brittle materials taking the wheel spindle vibration into account. The basic equations, for example, equations of grain trajectory and penetration depth are derived in new forms. Based on the basic equations above, the existing SR and SSD formulae are modified for further study. The effects of grinding and vibration parameters on SR and SSD are respectively analyzed in detail. Results show that both SR and SSD increase with the increase of table speed and vibration amplitude resulting in bad surface and subsurface quality. On the other hand, both the increasing grinding speed and decreasing vibration frequency can improve the quality of ground surface and subsurface with small SR and SSD. In addition, the increase of initial grinding depth and vibration initial phase increase the depth of SSD but have little effect on SR. The penetration depth and distance between grain's tip and finished surface are the two main factors considered to cause the different effect laws on SR and SSD among these parameters. Experiment is carried out to validate the rationality of proposed model. The effect trends of various grinding parameters on SR obtained by our model consist with measured experimental data. The typical subsurface crack system is clearly revealed through the experimental observation on SSD using SEM. Finally, the relationship between the two is fitted utilizing quadratic polynomial. Results show that the SSD depth is nonlinear monotone increasing with SR and the fitting accuracy is more or less affected by both grinding and vibration parameters.


      PubDate: 2015-01-23T16:30:20Z
       
  • IFC - Editorial board
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88




      PubDate: 2015-01-23T16:30:20Z
       
  • A new error measurement method to identify all six error parameters of a
           rotational axis of a machine tool
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Zhenya He , Jianzhong Fu , Liangchi Zhang , Xinhua Yao
      This paper presents a new error measurement method, a Dual Optical Path Measurement Method (DOPMM), to identify error parameters of the rotational axis of a machine tool along its error sensitive directions. The method development was carried out on a motorized rotary stage equipped with a Doppler laser instrument. An error measurement experiment and a machining experiment were conducted on a five-axis machining center with a titling rotary table. It was found that the DOPMM can identify all of the six volumetric error parameters with the simple algebraic operations. Compared with the existing ball bar tests, which need a mathematical error modeling of machine tools to separate the error parameters, the identified process of DOPMM is more simple and easier to understand. And the operation of machine tools during the measurement is much easier than that of the existing ball bar tests. The experimental results showed that the part precision can have a significant improvement of 68% when the identified error parameters are used for error compensation. Hence, the measurement method established in this study is sensible and efficient, and could be used for the error compensation on a wide range of machine tools to improve their machining precision.


      PubDate: 2015-01-23T16:30:20Z
       
  • A generalized on-line estimation and control of five-axis contouring
           errors of CNC machine tools
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Jixiang Yang , Yusuf Altintas
      Nonlinear and configuration-dependent five-axis kinematics make contouring errors difficult to estimate and control in real time. This paper proposes a generalized method for the on-line estimation and control of five-axis contouring errors. First, a generalized Jacobian function is derived based on screw theory in order to synchronize the motions of linear and rotary drives. The contouring error components contributed by all active drives are estimated through interpolated position commands and the generalized Jacobian function. The estimated axis components of contouring errors are fed back to the position commands of each closed loop servo drive with a proportional gain. The proposed contouring error estimation and control methods are general, and applicable to arbitrary five-axis tool paths and any kinematically admissible five-axis machine tools. The proposed algorithms are verified experimentally on a five-axis machine controlled by a modular research CNC system built in-house. The contouring errors are shown to be reduced by half with the proposed method, which is simple to implement in existing CNC systems.


      PubDate: 2015-01-23T16:30:20Z
       
  • Hardness control of grind-hardening and finishing grinding by means of
           area-based specific energy
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): U. Alonso , N. Ortega , J.A. Sanchez , I. Pombo , B. Izquierdo , S. Plaza
      The grind-hardening process uses the heat generated within the grinding zone in order to produce surface hardening of the workpiece. However, after the process, workpieces present dimensional inaccuracies and poor surface roughness. Thus, a final grinding operation has to be performed. For an industrial implementation of the whole process, two problems need to be solved. On the one hand, on-line control of the hardness penetration depth (HPD) should be achieved. On the other hand, excessive softening of the workpiece has to be avoided during the finishing grinding. This paper, firstly, investigates the feasibility of using the area based grinding energy ( E c ″ ) for the prediction of the HPD. Surface grind-hardening tests carried out on 100Cr6, 42CrMo4 and AISI 1045 steels have shown that, for all the tested parameter sets, a linear correlation exists between E c ″ and HPD. Furthermore, the slope of this linear relationship can be estimated from the chemical composition of the hardened steel based on the equivalent carbon number. On the other hand, the influence of varying wheel dressing conditions on the E c ″ –HPD relationship is analysed. Secondly, it has been found that a relationship exists between E c ″ and the surface softening during the finishing grinding operation. This relationship is independent of the grinding parameter combination when the maximum undeformed chip thickness is over a threshold value. Thus, E c ″ is a very appropriate parameter to control both the hardening and the finishing process of grind-hardened workpieces.


      PubDate: 2015-01-23T16:30:20Z
       
  • Depth-of-cut errors in ELID surface grinding of zirconia-based ceramics
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): H. Tang , Z.H. Deng , Y.S. Guo , J. Qian , D. Reynaerts
      Based on the analysis of a surface grinding system and the material removal mechanism, a mathematic model has been proposed to predict the accumulated error between the total set depth-of-cut (DoC) and the total actual depth-of-cut (ADoC) in multi-pass surface grinding of zirconia-based ceramic materials. Design of Experiments (DoE) approach has been implemented to carry out experiments. The influence of the set DoC of each grinding pass, the total set DoC, and the grinding wheel velocity on the accumulated errors in ADoC has been investigated in detail in surface grinding of zirconia-based ceramics both with electrolysis in-process dressing (ELID) and without ELID. It has been observed that the accumulated DoC errors increase faster in the first few passes and gradually reach a saturation after a certain total DoCs (about 8–10 grinding passes) and a higher step DoC leads to a faster (fewer passes) saturation of the accumulated DoC errors. Compared to grinding without ELID, it has been found that ELID-grinding is characterized with better process stability and ELID offers positive effects on material removal rate (MRR), especially in case of removing large volume of material with the same grinding parameters.


      PubDate: 2015-01-23T16:30:20Z
       
  • A new approach to contour error control in high speed machining
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Mostafizur Rahaman , Rudolf Seethaler , Ian Yellowley
      High speed machining technology attempts to maximize productivity through the use of high spindle speeds and axis traverse rates. The technology is dependent upon the development of suitable mechanical hardware, electrical drives and associated control software to ensure that all components are used to maximum advantage. The role of the control software is particularly demanding since one needs to maximize traverse rates while providing the necessary accuracy, and indeed providing a margin of safety to deal with unexpected changes in process, or system parameters. There have been relatively few improvements in commercial CAD or CAM systems that would help machine tool users to take maximum advantage of high speed machining; rather the majority of the approaches have been undertaken at the machine tool controller level. This paper uses circular interpolation and corner tracking to compare several such control techniques, (Cross Coupled Control (CCC), Zero Phase Error Tracking Control (ZPETC), and Realtime Frequency Modulated Interpolation (FMI)), each of which have been proposed in the literature order to improve machining accuracy. None of these approaches are found to be universally successful when used alone and the authors, in this paper, examine the use of these systems in combination. Particular attention is focused upon an extension of a simplified version of cross coupled control together with Frequency Modulated Interpolation. It is shown that the combined system performs extremely well, and is easily actuated at high frequencies with conventional hardware. A custom built high speed x-y table is used to confirm system performance with multiple constraints present.


      PubDate: 2015-01-23T16:30:20Z
       
  • Improving CNC contouring accuracy by robust digital integral sliding mode
           control
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Xue-Cheng Xi , Wan-Sheng Zhao , Aun-Neow Poo
      Integral sliding mode control (ISMC) has been employed and shown to improve contouring accuracy in the presence of external disturbances and model uncertainties. An ISMC controller directly reduces the tracking errors of each individual axis, thereby reducing the overall contour errors indirectly. An ISMC controller drives the system dynamics back onto the sliding surface if there exists a deviation from the predefined surface. In the design of an ISMC controller, it is crucial to choose an appropriate sliding surface as this has a great impact on system performance and on chattering. In current approaches, the sliding surface is chosen largely based on a rule of thumb which is only applicable for systems with open-loop poles having imaginary parts. In this paper, an approach is presented to design the sliding surface using principles of robust digital control so that both the regulation and robustness requirements can be satisfied. The natural frequency of the dominant closed-loop poles is chosen such that the modulus of the output sensitivity function lies within the robustness bounds. Resonant pole-zero filters are then used to reshape the output sensitivity function in specific frequency regions. Experiments showed that when the modulus of the output sensitivity function is kept within the robustness bounds, chattering can be avoided and the contour errors resulting from vibrations can be reduced. The introduction of a resonant pole-zero filter also allowed the attenuation band to be expanded so that the low frequency components of the contour errors are attenuated.


      PubDate: 2015-01-23T16:30:20Z
       
  • On-machine dry electric discharge truing of diamond wheels for
           micro-structured surfaces grinding
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Bing Guo , Qingliang Zhao
      Precision grinding with diamond wheels gives a promising alternative to achieve high quality micro-structured surfaces on optical molds. However, it is difficult to true these diamond wheels efficiently, because of the remarkable resistance property and the geometrical limitation of small wheel profile. In this paper, an on-machine dry-EDT method to precision shape and prepare diamond wheels with various profiles was proposed for micro-structured surface grinding. Firstly, the fundamental truing errors were analyzed based on the dry-EDT kinematics. And then the capabilities of dry-EDT truing for high abrasive concentration metal bonded diamond wheels were presented. Next, the effects of kinematic parameters variables on trued wheel profile accuracy were investigated. Finally, the micro-structured surfaces on SiC ceramic and tungsten carbide WC were ground by these trued diamond wheels. The experiments results showed that the arc-shaped diamond wheel (diameter of 200mm) with 4μm profile error (PV) and 1.0023mm profile radius, and the V-shaped diamond wheel with 22.5μm V-tip radius and 120.03° profile angle could be obtained by on-machine dry EDT. The kinematic parameters of dry-EDT have an important influence on truing profile accuracy of diamond wheels, especially for the tip of V-shaped wheel. The subsequent grinding show that the edge radius of V groove array on SiC is less than 2μm, while the radius of included corner is around 55μm. The PV error of ground arc groove array on WC is less than 5μm. The surface roughness of ground micro-structured surface R a is 142nm and 97nm for SiC and WC, respectively.


      PubDate: 2015-01-23T16:30:20Z
       
  • The effect of axis coupling on machine tool dynamics determined by tool
           deviation
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Lei Wang , Haitao Liu , Lei Yang , Jun Zhang , Wanhua Zhao , Bingheng Lu
      High acceleration forces of machine tool with kinetic coupling as the dominating coupling forces may deform the machine structure and result in the tool deviation. In this paper, a dynamic model of a three-axis gantry milling machine tool considering axis coupling effects is proposed to model the varying dynamic behavior and evaluate the Tool Center Point (TCP) position deviations. The effect of axis coupling force on the stiffness changes of kinematic joints is analyzed. The variations of the frequencies and frequency response functions with respect to position parameters are calculated. And the TCP deviation affected by axial coupling in real-time motion state is discussed in detail. The results show that it is able to obtain an excellent match between the simulations and the measurements. The simulation and experimental results show that: (1) the natural frequencies and the receptance are greatly changed when the TCP is moving along the X-axis or the Z-axis, where the maximum changing of natural frequencies is up to 10% and response magnitude up to 2 times; (2) the elastic deformation and vibration of machine tool are caused by the coupling forces in acceleration and braking, which detrimentally affect dynamic response of the TCP. Thus, the model proposed in this paper represents the important effects for comprehension of machine dynamic behavior and for further compensation in future.


      PubDate: 2015-01-23T16:30:20Z
       
  • Threshold tool-radius condition maximizing the formability in SPIF
           considering a variety of materials: Experimental and FE investigations
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): K.A. Al-Ghamdi , G. Hussain
      In the current study, a new level of understanding on the influence of using small tool radii on the formability (θ max ) is identified for single point incremental forming (SPIF). The relative value of tool radius and blank thickness (i.e., R/T B , where R is the tool radius and T B is the blank thickness) was varied over a range (from 1.1 to 3.9), and a formability diagram in the R/T B –θ max space was obtained. The formability was observed to show an inverse V-type pattern which revealed that there is a critical radius of tool (R c ) that maximizes the formability in SPIF. Further, this radius which was found to be independent of the material type (or property) is a function of blank thickness related as, R c ≈2.2T B . This radius was termed as threshold radius. The formability, in agreement with general opinion in the literature, was noticed to increase with the decrease in the tool radius above the threshold value. However, contrarily it reduced with the decrease in the tool radius below the threshold value. In fact, undue surface cutting and metal squeezing was detected when the tests were performed with pointed tools, i.e., below threshold radius. This unstable deformation, which according to the FE analyses was found to be an outgrowth of in-plane compression under the tool center, increasingly weakened the material by inducing corresponding increase in damage (quantified by stress triaxiality) with the decrease in the tool radius. On the other hand, the damage was also observed to increase due to decrease in compression with the increase in the tool radius above the threshold value. This revealed high compression with low damage constitutes the most conducive condition that maximizes the formability in SPIF, which is realized when R≈2.2T B .


      PubDate: 2015-01-23T16:30:20Z
       
  • Tailoring surface quality through mass and momentum transfer modeling
           using a volume of fluid method in selective laser melting of TiC/AlSi10Mg
           powder
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Donghua Dai , Dongdong Gu
      A selective laser melting (SLM) physical model of coupled radiation transfer and thermal diffusion is proposed, which provides a local temperature field. A strong difference in thermal conductivity between the powder bed and dense material is taken into account. Both thermo-capillary force and recoil pressure induced by the material evaporation, which are the major driving forces for the melt flow, are incorporated in the formulation. The effect of the laser energy input per unit length (LEPUL) on the temperature distribution, melt pool dynamics, surface tension and resultant surface morphology has been investigated. It shows that the surface tension plays a crucial role in the formation of the terminally solidified surface morphology of the SLM-processed part. The higher surface tension of the lower temperature metal near the edge of the melt pool and the thermal-capillary force induced by the surface temperature gradient tend to pull the molten metal away from the center of the melt pool. For a relatively high LEPUL of 750J/m, the molten material in the center of the melt pool has a tendency to flow towards the rear part, resulting in the stack of molten material and the attendant formation of a poor surface quality. For an optimized processing condition, LEPUL=500J/m, a complete spreading of the molten material driven by the surface tension is obtained, leading to the formation of a fine and flat melt pool surface. The surface quality and morphology are experimentally acquired, which are in a good agreement with the results predicted by simulation.


      PubDate: 2015-01-23T16:30:20Z
       
  • Abrasive waterjet micro-machining of channels in metals: Comparison
           between machining in air and submerged in water
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Naser Haghbin , Jan K. Spelt , Marcello Papini
      Abrasive water jet technology can be used for micro-milling using recently developed miniaturized nozzles. Abrasive water jet (AWJ) machining is often used with both the nozzle tip and workpiece submerged in water to reduce noise and contain debris. This paper compares the performance of submerged and unsubmerged abrasive water jet micro-milling of channels in 316L stainless steel and 6061-T6 aluminum at various nozzle angles and standoff distances. The effect of submergence on the diameter and effective footprint of AWJ erosion footprints was measured and compared. It was found that the centerline erosion rate decreased with channel depth due to the spreading of the jet as the effective standoff distance increased, and because of the growing effect of stagnation as the channel became deeper. The erosive jet spread over a larger effective footprint in air than in water, since particles on the jet periphery were slowed much more quickly in water due to increased drag. As a result, the width of a channel machined in air was wider than that in water. Moreover, it was observed that the instantaneous erosion rate decreased with channel depth, and that this decrease was a function only of the channel cross-sectional geometry, being independent of the type of metal, the jet angle, the standoff distance, and regardless of whether the jet was submerged or in air, in either the forward or backward directions. It is shown that submerged AWJM results in narrower features than those produced while machining in air, without a decrease in centerline etch rate.


      PubDate: 2015-01-23T16:30:20Z
       
  • Study on micro-topographical removals of diamond grain and metal bond in
           dry electro-contact discharge dressing of coarse diamond grinding wheel
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Y.J. Lu , J. Xie , X.H. Si
      A coarse diamond grinding wheel is able to perform smooth surface grinding with high and rigid grain protrusion, but it is very difficult to dress it. Hence, the dry electro-contact discharge (ECD) is proposed to dress #46 diamond grinding wheel for dry grinding of carbide alloy. The objective is to understand micro-topographical removals of diamond grain and metal bond for self-optimizing dressing. First, the pulse power and direct-current (DC) power were employed to perform dry ECD dressing in contrast to mechanical dressing; then the micro-topographies of diamond grains and metal bond were recognized and extracted from measured wheel surface, respectively; finally, the relationship between impulse discharge parameters and micro-topographical removals was investigated with regard to grain cutting parameters, dry grinding temperature and ground surface. It is shown that the dry ECD dressing along with spark discharge removal may enhance the dressing efficiency by about 10 times and dressing ratio by about 34 times against the mechanical dressing along with cutting removal. It averagely increases grain protrusion height by 12% and grain top angle by 23%, leading to a decrease 37% in grinding temperature and a decrease 46% in surface roughness. Compared with the DC-25V power along with arc discharges, the Pulse-25V power removes the metal bond at 0.241mm3/min by utilizing discharge energy by 73% and diamond grain at 0.013mm3/min through surface graphitization, respectively, leading to high and uniform grain protrusion. It is confirmed that the impulse discharge parameters are likely to control the microscopic grain protrusion topography for efficient dressing according to their relations to the micro-removal of metal bond.
      Graphical abstract image

      PubDate: 2015-01-23T16:30:20Z
       
  • Diamond machining of silicon: A review of advances in molecular dynamics
           simulation
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Saurav Goel , Xichun Luo , Anupam Agrawal , Robert L. Reuben
      Molecular dynamics (MD) simulation has enhanced our understanding about ductile-regime machining of brittle materials such as silicon and germanium. In particular, MD simulation has helped understand the occurrence of brittle–ductile transition due to the high-pressure phase transformation (HPPT), which induces Herzfeld–Mott transition. In this paper, relevant MD simulation studies in conjunction with experimental studies are reviewed with a focus on (i) the importance of machining variables: undeformed chip thickness, feed rate, depth of cut, geometry of the cutting tool in influencing the state of the deviatoric stresses to cause HPPT in silicon, (ii) the influence of material properties: role of fracture toughness and hardness, crystal structure and anisotropy of the material, and (iii) phenomenological understanding of the wear of diamond cutting tools, which are all non-trivial for cost-effective manufacturing of silicon. The ongoing developmental work on potential energy functions is reviewed to identify opportunities for overcoming the current limitations of MD simulations. Potential research areas relating to how MD simulation might help improve existing manufacturing technologies are identified which may be of particular interest to early stage researchers.


      PubDate: 2015-01-23T16:30:20Z
       
  • Straightness error compensation for large CNC gantry type milling centers
           based on B-spline curves modeling
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): W.L. Feng , X.D. Yao , Arynov Azamat , J.G. Yang
      Fast and accurate modeling for the straightness errors of machine tools is significant important for the implementation of error compensation. To decrease the straightness errors which generally exist in gantry type milling centers, a novel approach for real-time compensation of straightness errors is presented, including an accurate spatial straightness error model which based on B-Spline curves method and a real-time errors compensation system which can compensate multiple errors at the same time in real-time. An experiment is carried out to measure the straightness errors of a gantry type milling center by using a laser interferometer. There are two straightness errors for one direction movement of an axis. As a result, there are six straightness errors for a three-axis milling center. The straightness error model is established by the B-Spline curves method. According to these six straightness error models, a spatial straightness error model is obtained by superposition of these straightness error models. In addition, an external real-time errors compensation system is developed based on the function of external mechanical origin offset in Fanuc CNC systems. The compensation experiments are conducted to verify the accuracy of the spatial straightness error model and the effectiveness of the error compensation system. The experimental results show that the straightness errors of the machined work-pieces are proved to have been decreased over 90% compared with that of non-compensations. The B-Spline curves modeling combining the errors compensation system can be utilized as an effective approach to improve the accuracy of the CNC gantry type milling centers.


      PubDate: 2015-01-23T16:30:20Z
       
  • Precise prediction of forces in milling circular corners
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Xiong Han , Limin Tang
      Pocket corner is the most typical characters of aerospace structure components. To achieve high-quality product and stable machining operation, manufacturer constantly seek to control the cutting forces in pocket corner milling process. This paper presents the cutting force in corner milling considering the precision instantaneous achievements of tool engagement angle and undeformed chip thickness. To achieve the actual milling tool engagement angle in corner milling process, the details of tool–corner engagement relationship are analyzed considering the elements of tool trajectory, tool radius, and corner radius. The actual undeformed chip thicknesses in up and down milling operations are approached on account of the trochoid paths of adjacent teeth by a presented iteration algorithm. Error analysis shows that the presented models of tool engagement angle and undeformed chip thickness have higher precision comparing with the traditional models. Combined with the cutting force coefficients fitted by a series of slot milling tests, the predicted cutting force in milling titanium pocket with different corner structure and milling parameters are achieved, and the prediction accuracy of the model was validated experimentally and the obtained predict and the experiment results were found in good agreement.
      Graphical abstract image

      PubDate: 2015-01-23T16:30:20Z
       
  • Theoretical and experimental study on rifling mark generating phenomena in
           BTA deep hole drilling process (generating mechanism and countermeasure)
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Kenichiro Matsuzaki , Takahiro Ryu , Atsuo Sueoka , Keizo Tsukamoto
      Boring and Trepanning Association (BTA) deep hole drilling is used for producing holes with high aspect ratios. In this process, chatter vibration sometimes occurs, and a rifling mark is formed on the bore surface. The rifling mark generating phenomenon is considered to be a result of self-excited vibration caused by time delay. An analytical model is proposed considering the supporting condition of the boring bar in detail. In a real machine for BTA drilling, the boring bar is supported at the oil pressure head and the supporting pad, as well as at the base. The stability of the self-excited vibration is analyzed numerically, and the result is compared with the experiment. The theoretical and experimental results agree well with each other. Furthermore, the effect of an additional guide pad proposed by the authors as a countermeasure is evaluated theoretically and experimentally.


      PubDate: 2015-01-23T16:30:20Z
       
  • A study of an improved cutting mechanism of composite materials using
           novel design of diamond micro-core drills
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): P.W. Butler-Smith , D.A. Axinte , M. Daine , A.R. Kennedy , L.T. Harper , J.F. Bucourt , R. Ragueneau
      Core drilling at small diameters in carbon composite materials is largely carried out using diamond electroplated tools consisting of hollow shafts and simplistic geometries that are likely to work in an abrasional/rubbing mode for material removal. The paper reports a step change in the performance of small diameter core drilling by facilitating a shearing mechanism of the composite workpiece through the utilisation of a novel tool design. This has been achieved by laser producing core drills from solid polycrystalline diamond, incorporating controlled cutting edges where the geometries are defined. To evaluate the efficiency of the shearing vs. abrasion/rubbing cutting mechanisms, a critical comparison between the novel (defined cutting edges) and the conventional electroplated tools (randomly distributed micro-grains) has been made with reference to thrust forces, tool wear mechanisms and their influences on the hole quality (e.g. delamination, fibre pullout). This work has been augmented by studies using high-speed thermal imaging of the two tool types in operation. The examinations have shown that, based on the concept of defined cutting edges in solid diamond, there is the possibility to make significant improvements in core drilling performance, (ca. 26% lower thrust force, minimal tool surface clogging, lower drilling temperatures) resulting in improved cleanliness of fibre fracture and a reduced tendency of material delamination.


      PubDate: 2014-11-24T10:00:40Z
       
 
 
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