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  Subjects -> MANUFACTURING AND TECHNOLOGY (Total: 259 journals)
    - CERAMICS, GLASS AND POTTERY (24 journals)
    - MACHINERY (32 journals)
    - MANUFACTURING AND TECHNOLOGY (157 journals)
    - METROLOGY AND STANDARDIZATION (3 journals)
    - PACKAGING (13 journals)
    - PAINTS AND PROTECTIVE COATINGS (5 journals)
    - PLASTICS (25 journals)

MACHINERY (32 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)
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: 1)
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
   [6 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0890-6955
     Published by Elsevier Homepage  [2571 journals]   [SJR: 2.724]   [H-I: 71]
  • 1-Shot hot stamping of ultra-High strength steel parts consisting of
           resistance heating, forming, shearing and die quenching
    • Abstract: Publication date: Available online 4 November 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): K. Mori , T. Maeno , H. Yamada , H. 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: 2014-11-24T10:00:40Z
       
  • Position geometric error modeling, identification and compensation for
           large 5-axis machining center prototype
    • Abstract: Publication date: Available online 5 November 2014
      Source:International Journal of Machine Tools and Manufacture
      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 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: 2014-11-24T10:00:40Z
       
  • Machining of hardened steel: Experimental investigations, performance
           modeling and cooling techniques: A review
    • Abstract: Publication date: Available online 12 November 2014
      Source:International Journal of Machine Tools and Manufacture
      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: 2014-11-24T10:00:40Z
       
  • 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: Available online 5 November 2014
      Source:International Journal of Machine Tools and Manufacture
      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: 2014-11-24T10:00:40Z
       
  • Assessment of spray quality from an external mix nozzle and Its impact on
           SQL grinding performance
    • Abstract: Publication date: Available online 13 November 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Shiva Sai S , Manoj Kumar K , 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: 2014-11-24T10:00:40Z
       
  • Time domain Prediction of milling stability according to cross edge
           radiuses and flank edge profiles
    • Abstract: Publication date: Available online 13 November 2014
      Source:International Journal of Machine Tools and Manufacture
      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: 2014-11-24T10:00:40Z
       
  • 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: 2014-11-24T10:00:40Z
       
  • The estimation of cutting forces and specific force coefficients during
           finishing ball end milling of inclined surfaces
    • Abstract: Publication date: Available online 15 November 2014
      Source:International Journal of Machine Tools and Manufacture
      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: 2014-11-24T10:00:40Z
       
  • Editorial
    • Abstract: Publication date: Available online 17 November 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): T.A. Dean



      PubDate: 2014-11-24T10:00:40Z
       
  • Modeling and experimental investigation of gas film in micro
           electrochemical discharge machining process
    • Abstract: Publication date: Available online 20 November 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Baoyang Jiang , Shuhuai Lan , 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: 2014-11-24T10:00:40Z
       
  • Geometric prediction of conic tool in micro-EDM milling with fix-length
           compensation using simulation
    • Abstract: Publication date: Available online 20 November 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): ZHANG Lenan , DU Jianyi , ZHUANG Xiaoshun , WANG Zhiliang , PEI Jingyu
      Micro-EDM milling is an effective machining process for three-dimension 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-dimension matrices. Second, the machining process was divided into three parts including sparking, horizontal feeding and vertical feeding respectively. 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: 2014-11-24T10:00:40Z
       
  • Performance evaluation of Ti–6Al–4V grinding using chip
           formation and coefficient of friction under the influence of nanofluids
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Dinesh Setti , Manoj Kumar Sinha , Sudarsan Ghosh , P. Venkateswara Rao
      Nanofluid, fluid suspensions of nanometer sized particles are revolutionizing the field of heat transfer area. Addition of nano-particles to the base fluid also alters the lubricating properties by reducing the friction. In grinding process, friction between the abrasive grains and the workpiece is a key issue governing the main grinding output. It has a direct influence on grinding force, power, specific energy and wheel wear. Moreover, high friction force increases the heat generation and lead to thermal damage in the surface layer of the ground work. Hence, any effort towards the friction control will enhance the component quality significantly. In this study, nanofluid as metal working fluid (MWF) is made by adding 0.05, 0.1, 0.5 and 1% volume concentration of Al2O3 and CuO nano-particles to the water during the surface grinding of Ti–6Al–4V in minimum quantity lubrication (MQL) mode. Surface integrity of ground surface, morphology of the wheel, and chip formation characteristics are studied using surface profilometer, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and stereo zoom microscopy (SZM). Coefficient of friction was estimated On-Machine using the measured forces. The results showed that the type of nanoparticle and its concentration in base fluid and the MQL flow rate play a significant role in reducing friction. Application of nanofluid leads to the reduction of tangential forces and grinding zone temperature. The cooling effect is also evident from the short C-type chip formation. MQL application with Al2O3 nanofluid helps in effective flushing of chip material from the grinding zone, thereby solving the main problem during the grinding of Ti–6Al–4V.


      PubDate: 2014-11-24T10:00:40Z
       
  • Molecular dynamics modelling of brittle–ductile cutting mode
           transition: Case study on silicon carbide
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88
      Author(s): Gaobo Xiao , Suet To , Guoqing Zhang
      The mechanism of brittle–ductile cutting mode transition has received much attention over the past two decades. Due to the difficulties in directly observing the cutting zone during the brittle–ductile cutting mode transition by experimental techniques, many molecular dynamics (MD) studies have been conducted to investigate the atomicscale details of the phenomena, e.g. phase transformation, stress distribution and crack initiation, mostly under nanoscale undeformed chip thicknesses. A research gap is that direct MD modelling of the transition under practical undeformed chip thicknesses was not achieved in previous studies, due to the limitations in both computation capability and interaction potential. Important details of the transition under practical undeformed chip thicknesses thereby remain unclear, e.g. the location of crack formation and the stress distribution. In this study, parallel MD codes based on graphics processing units (GPU) are developed to enable large-scale MD simulations with multi-million atoms. In addition, an advanced interaction potential which reproduces brittle fracture much more accurately is adopted. As a result, the direct MD simulation of brittle–ductile cutting mode transition is realised for the first time under practical undeformed chip thicknesses. The MD-modelled critical undeformed chip thickness is verified by a plunge cutting experiment. The MD modelling shows that tensile stress exists around the cutting zone and increases with undeformed chip thickness, which finally induces brittle fractures. The location of crack formation and direction of propagation varies with undeformed chip thickness in the MD simulations, which agrees with the surface morphologies of the taper groove produced by the plunge cutting experiment. This study contributes significantly to the understanding of the details involved in the brittle–ductile cutting mode transition.


      PubDate: 2014-11-24T10:00:40Z
       
  • 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: 2014-11-24T10:00:40Z
       
  • 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
       
  • IFC - Editorial board
    • Abstract: Publication date: January 2015
      Source:International Journal of Machine Tools and Manufacture, Volume 88




      PubDate: 2014-11-24T10:00:40Z
       
  • 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: 2014-11-24T10:00:40Z
       
  • 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: 2014-11-24T10:00:40Z
       
  • 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: 2014-11-24T10:00:40Z
       
  • 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: 2014-11-24T10:00:40Z
       
  • 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: 2014-11-24T10:00:40Z
       
  • 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: 2014-11-24T10:00:40Z
       
  • Abrasive Waterjet Micro-Machining of Channels in Metals: Comparison
           Between Machining in Air and Submerged in Water
    • Abstract: Publication date: Available online 5 October 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): N. Haghbin , J.K. Spelt , M. 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: 2014-10-09T01:04:09Z
       
  • Diamond machining of silicon: A review of advances in molecular dynamics
           simulation
    • Abstract: Publication date: Available online 6 October 2014
      Source:International Journal of Machine Tools and Manufacture
      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: 2014-10-09T01:04:09Z
       
  • Straightness error compensation for large CNC gantry type milling centers
           based on B-spline curves modeling
    • Abstract: Publication date: Available online 28 September 2014
      Source:International Journal of Machine Tools and Manufacture
      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 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: 2014-10-04T00:56:36Z
       
  • Corner rounding of linear five-axis tool path by dual PH curves blending
    • Abstract: Publication date: Available online 28 September 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Jing Shi , QingZhen Bi , LiMin Zhu , YuHan Wang
      The widespread linear five-axis tool path (G01 blocks) is usually described by two trajectories. One trajectory describes the position of the tool tip point, and the other one describes the position of the second point on the tool axis. The inherent disadvantages of linear tool path are tangential and curvature discontinuities at the corners in five-axis tool path, which will result in feedrate fluctuation and decrease due to the kinematic constraints of the machine tools. In this paper, by using a pair of quintic PH curves, a smoothing method is proposed to round the corners. There are two steps involved in our method. Firstly, according to the accuracy requirements of the tool tip contour and tool orientation tolerances, the corner is rounded with a pair of PH curves directly. Then, the control polygon lengths of PH curves are adjusted simply to guarantee the continuous variation of the tool orientation at the junctions between the transition curves and the remainder linear segments. Because the PH curves for corner rounding can be constructed without any iteration, and those two rounded trajectories are synchronized linearly in interpolation, which makes this smoothing method can be applied in a high efficiency way. Its high computational efficiency allows it to be implemented in real-time applications. This method has been integrated into a CNC system with an open architecture to implement on-line linear five-axis tool path smoothing. Simulations and experiments validate its practicability and reliability.


      PubDate: 2014-10-04T00:56:36Z
       
  • On-machine dry electric discharge truing of diamond Wheels for
           micro-structured Surfaces grinding
    • Abstract: Publication date: Available online 2 October 2014
      Source:International Journal of Machine Tools and Manufacture
      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: 2014-10-04T00:56:36Z
       
  • 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: Available online 2 October 2014
      Source:International Journal of Machine Tools and Manufacture
      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: 2014-10-04T00:56:36Z
       
  • Quantitative characterization and influence of Parameters on surface
           topography in metal micro-droplet deposition manufacture
    • Abstract: Publication date: Available online 2 October 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Le-hua Qi , Song-yi Zhong , Jun Luo , Dai-cong Zhang , Han-song Zuo
      Metal micro-droplet deposition manufacture has potential applications and attracts increasing attention in wide areas. By quantitatively describing and predicting the surface topography, the influence of parameters on surface quality could be studied effectively. In present work, a new approach aimed to the characterization of part surface topography was proposed and the evaluation indexes such as arithmetic average height (R a ) and stratification angle (θ) were used to characterize the surface topography. Based on the surface geometrical profile, two prediction models were developed to calculate the evaluation indexes of part surface. Then experiments for fabricating thin wall parts were conducted and the evaluation indexes were measured experimentally. By comparing the experimental values with the predicted results, the mechanism of process parameters affecting surface topography was investigated. The results indicated that the top surface was mainly affected by scan step (W d ) which also could be represented by overlap ratio (μ). While overlap ratio was larger than 25.7%, excessive overlap resulting in poor surface topography occurred and the prediction model was invalid. In another hand, the side surface was mainly affected by offset distance (W o ) which also could be represented by offset ratio (τ). If offset ratio was too large, the ending side would collapse resulting in poor side surface topography and the prediction model would fail to calculate the side surface roughness. The experiment results indicated that collapse would occur while offset ratio was larger than 54.5%. In the last, the surface roughness of a cubic object was measured and the results demonstrated that the method proposed in present work was useful for evaluating surface quality of 3D object.


      PubDate: 2014-10-04T00:56:36Z
       
  • Threshold tool-radius condition maximizing the formability in SPIF
           considering a variety of materials: Experimental and FE investigations
    • Abstract: Publication date: Available online 21 September 2014
      Source:International Journal of Machine Tools and Manufacture
      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 decease 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: 2014-09-23T00:15:45Z
       
  • A new approach to contour error control in High speed machining
    • Abstract: Publication date: Available online 16 September 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Mostafizur Rahaman , Rudolf Seethaler , Ian Yellowley
      High speed machining technology attempts to maximise 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 maximise 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 focussed 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: 2014-09-18T23:58:09Z
       
  • Hardness control of grind-hardening and finishing grinding by means of
           area-based specific energy
    • Abstract: Publication date: Available online 16 September 2014
      Source:International Journal of Machine Tools and Manufacture
      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: 2014-09-18T23:58:09Z
       
  • The effect of axis coupling on machine tool dynamics determined by tool
           deviation
    • Abstract: Publication date: Available online 16 September 2014
      Source:International Journal of Machine Tools and Manufacture
      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 X-axis or 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: 2014-09-18T23:58:09Z
       
  • Precise Prediction of Forces in Milling Circular Corners
    • Abstract: Publication date: Available online 18 September 2014
      Source:International Journal of Machine Tools and Manufacture
      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: 2014-09-18T23:58:09Z
       
  • IFC-Editorial board
    • Abstract: Publication date: December 2014
      Source:International Journal of Machine Tools and Manufacture, Volume 87




      PubDate: 2014-09-18T23:58:09Z
       
  • A generalized on-line estimation and control of five-axis contouring
           Errors of CNC machine Tools
    • Abstract: Publication date: Available online 24 August 2014
      Source:International Journal of Machine Tools and Manufacture
      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: 2014-09-04T22:46:10Z
       
  • Improving CNC contouring accuracy by robust digital integral sliding mode
           control
    • Abstract: Publication date: Available online 4 September 2014
      Source:International Journal of Machine Tools and Manufacture
      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 error 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 mode 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 are chosen such that the modulus of the output sensitivity function lies within robustness bounds. Resonant pole-zero filters are then used to reshape the output sensitivity function in specific frequency regions. Experiments showed that when 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 pole-zero filter also allowed the attenuation band to be expanded so that the low frequency components of the contour errors are attenuated.


      PubDate: 2014-09-04T22:46:10Z
       
  • Depth-of-cut errors in ELID surface grinding of zirconia-based ceramics
    • Abstract: Publication date: Available online 30 August 2014
      Source:International Journal of Machine Tools and Manufacture
      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 details 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 a 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: 2014-09-04T22:46:10Z
       
  • IFC - Editorial board
    • Abstract: Publication date: November 2014
      Source:International Journal of Machine Tools and Manufacture, Volume 86




      PubDate: 2014-08-18T21:40:31Z
       
  • Validation of volumetric error compensation for a five-axis machine using
           surface mismatch producing tests and on-machine touch probing
    • Abstract: Publication date: Available online 12 August 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Mehrdad Givi , J.R.R. Mayer
      In order to validate volumetric error compensation methods for five-axis machine tools, the machining of test parts have been proposed. For such tests, a coordinate measuring machine (CMM) or other external measurement, outside of the machine tool, are required to measure the accuracy of the machined part. In this paper, a series of machining tests are proposed to validate a compensation strategy and compare the machining accuracy before and after the compensation using only on-machine measurements. The basis of the tests is to machine slots, each completed using two different rotary axes indexations of the CNC machine tool. Using directional derivatives of the volumetric errors, it is possible to verify that a surface mismatch is produced between the two halves of the same slot in the presence of specific machine geometric errors. The mismatch at the both sides of the slot, which materialize the machine volumetric errors are measured using touch probing by the erroneous machine itself and with high accuracy since the measurement of both slot halves can be conducted using a single set of rotary axes indexation and in a volumetric region of a few millimetres. The effect of a compensation strategy is then validated by comparing the surface mismatch value for compensated and uncompensated slots.


      PubDate: 2014-08-14T21:30:41Z
       
  • A method of using turning process excitation to determine dynamic cutting
           coefficients
    • Abstract: Publication date: Available online 12 August 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Kuanmin Mao , Ming Zhu , Weiwei Xiao , Bin Li
      Identification of the dynamic cutting force coefficients is essential in cutting process modeling. The excitation equipment employed to produce dynamic cutting process are usually sophisticated and may lead to potential error. An alternative method of turning process excitation is proposed to simplify the procedure of cutting dynamics measurement. A cantilever workpiece used in cylindrical turning process has been modeled with a double degree-of-freedom system that supports variable dynamic parameters. The structural dynamics of the equivalent system are analyzed with the theoretical derivation and the finite element simulations. The influence of structural dynamic variation on the chatter frequency is investigated, based on which the self-excited chatter is considered as a method of the turning process excitation. This method is applied in the cutting dynamics tests. The dynamic cutting force coefficients could be measured through a single chattering turning process. Stability analysis is conducted for verification of the measured dynamic cutting coefficients.


      PubDate: 2014-08-14T21:30:41Z
       
  • A new error measurement method to identify all six error parameters of A
           rotational axis of A machine tool
    • Abstract: Publication date: Available online 11 August 2014
      Source:International Journal of Machine Tools and Manufacture
      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: 2014-08-11T21:20:44Z
       
  • Feed speed scheduling method for parts with rapidly varied geometric
           feature based on drive constraint of NC machine tool
    • Abstract: Publication date: Available online 11 August 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Zhenyuan Jia , Ling Wang , Jianwei Ma , Kai Zhao , Wei Liu
      Parts with rapidly varied geometric feature are widely applied in the fields of aerospace, energy power, and automobile, and are difficult to process because of the more special structure and the higher requirement of machining precision. As the existence of rapidly varied geometric feature and during the NC manufacturing process of this kind of parts, the actual moving speed of the workbench of the NC machine tool cannot reach the feed speed set in the NC program timely due to the drive constraint of NC machine tool. Furthermore, the machine tool would vibrate violently with the drive constraint when employing the constant machining parameter to process the parts with rapidly varied geometric feature, which seriously restricts the improvement of processing this kind of parts with high quality and high efficiency. In order to manufacture such parts with high quality and high efficiency, a sub-regional processing method with variable machining parameters is proposed. Firstly, the generation mechanism of the machining error is studied, and its mathematical model is built. Then the change rule of the machining error influenced by the curvature and the NC programmed feed speed is found out. Finally, taking the drive constraint and the machining error requirement into account, the relationship between the programmed feed speed and the curvature is established, and the corresponding programmed feed speeds to different curvatures are obtained. Taking the NC machining of the edge line of spiral microstrip antenna, which is an equiangular spiral, for example, the experiment results show that compared with the machining result with constant machining parameter, the maximum machining error of the sub-regional processing method with variable machining parameters decreases by 35.51% and the average value of the machining error decreases by 46.65%. For another example, the clover rose line is machined and the processing quality is also improved. This study proves that the method distributing the programmed feed speeds based on the curvature variation can improve the machining precision and ensure processing efficiency, and provides an effective method to manufacture parts with rapidly varied geometric feature.


      PubDate: 2014-08-11T21:20:44Z
       
  • Experimental and numerical studies of the solution heat treatment,
           forming, and in-die quenching (HFQ) process on AA5754
    • Abstract: Publication date: Available online 1 August 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Omer El Fakir , Liliang Wang , Daniel Balint , John P. Dear , Jianguo Lin , Trevor A. Dean
      An FE model of the solution Heat treatment, Forming and in-die Quenching (HFQ) process was developed. Good correlation with a deviation of less than 5% was achieved between the thickness distribution of the simulated and experimentally formed parts, verifying the model. Subsequently, the model was able to provide a more detailed understanding of the HFQ process, and was used to study the effects of forming temperature and speed on the thickness distribution of the HFQ formed part. It was found that a higher forming speed is beneficial for HFQ forming, as it led to less thinning and improved thickness homogeneity.


      PubDate: 2014-08-05T21:02:35Z
       
  • Mechanics and dynamics of thread milling process
    • Abstract: Publication date: Available online 29 July 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Min Wan , Yusuf Altintas
      This paper presents the mechanics and dynamics of thread milling operations. The tool follows a helical path around the wall of the pre-machined hole in thread milling, which has varying tool-part engagement and cut area during one threading cycle. The variation of cut area that reflects the kinematics of threading as well as structural vibrations is modeled along the helical, threading path. The mechanics of the process are first experimentally proven, followed by the formulation of dynamic thread milling which is periodic in threading cycle, in a semi-discrete time domain. The stability of the operation is predicted as a function of spindle speed, axial depth of cut, cutter path and tool geometry. The mechanics and stability models are experimentally proven in opening M16×2 threads with a five-fluted helical tool on a Steel AISI1045 workpiece.


      PubDate: 2014-08-01T20:44:30Z
       
  • Dynamics of Ultra-High-Speed (UHS) Spindles used for Micromachining
    • Abstract: Publication date: Available online 30 July 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Bekir Bediz , B. Arda Gozen , Emrullah Korkmaz , O. Burak Ozdoganlar
      Micromachining dynamics commonly dictate the attainable accuracy and throughput that can be obtained from micromachining operations. The dynamic behavior of miniature ultra-high-speed (UHS) spindles used in micromachining critically affects micromachining dynamics. As such, there is a strong need for effective techniques to characterize the dynamic behavior of miniature UHS spindles. This paper presents a systematic experimental approach to obtain the speed-dependent two-dimensional dynamics of miniature UHS spindles through experimental modal analysis. A miniature cylindrical artifact with 5mm overhang is attached to (and rotating with) the spindle to enable providing the dynamic excitations to and measuring the resulting motions of the spindle. A custom-made impact excitation system is used to reproducibly excite the spindle dynamics up to 20kHz while controlling the impact force. The resulting radial motions of the spindle are measured in two mutually-perpendicular directions using two independent fiber-optic laser Doppler vibrometers (LDVs). To ensure the mutual orthogonality of the measurements, the two lasers are aligned precisely using an optical procedure. A frequency-domain filtering approach is used to remove the unwanted spindle motion data from the measurements, thereby isolating the dynamic response. The spindle dynamics is then represented in the form of frequency response functions (FRFs). A global curve-fitting technique is applied to identify natural frequencies and damping ratios. The developed approach is demonstrated on a miniature UHS spindle with aerodynamic bearings, and dynamic characteristics are analyzed at different spindle speeds and collet pressures. The spindle speed is shown to have a significant effect on dynamic response, especially at higher spindle speeds, while the collet pressure is observed not to have any significant effect on the spindle dynamics. It is concluded that the presented approach can be used to characterize the dynamics of miniature UHS spindles effectively.


      PubDate: 2014-08-01T20:44:30Z
       
  • Development and implementation of a NURBS interpolator with smooth
           feedrate scheduling for CNC machine tools
    • Abstract: Publication date: Available online 22 July 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Min Liu , Yu Huang , Ling Yin , JianWen Guo , XinYu Shao , GuoJun Zhang
      Parametric interpolation for Non-Uniform Rational B-Spline (NURBS) curve has become more important than ever before in the control of CNC machine tools. An effective NURBS interpolator not only can obtain accurate contour trajectories, but also have smooth dynamics performance. This paper proposes a numerically efficient NURBS interpolation scheme which consists of two stages namely preprocessing and interpolating. In the stage of pre-processing, the parameter interval is split into several blocks at breakpoints and an iterative numerical quadrature method is applied for each block. By means of the iterative quadrature method, the initial parameter intervals of each block are divided into several subintervals according to the arc length approximation error. Meanwhile, the curvature of each knot and the cubic polynomial coefficients of each subinterval are obtained. Then the critical points with large curvature of each block are found from the candidate points and the tolerated speed of each critical point is calculated according to the constraints of chord error and centripetal acceleration. Hence, the feedrate scheduling based on the S-shaped acceleration profile for each block can be preplanned via the approximate arc length of each subinterval, the tolerated speed of each critical point and kinematics characteristics such as acceleration/deceleration and jerk limits of the machine tools. In the stage of interpolating, the parameter of the next interpolation point can be calculated directly using the cumulative arc length and the cubic polynomial coefficients of each subinterval. Finally, a series of numerical simulations and real machining experiments are conducted , and the simulation and experimental results have showed the good performance of the proposed NURBS interpolator both in efficiency and accuracy.
      Graphical abstract image Highlights

      PubDate: 2014-07-27T20:26:40Z
       
  • A systematic optimization approach for the calibration of parallel
           kinematics machine tools by a laser tracker
    • Abstract: Publication date: November 2014
      Source:International Journal of Machine Tools and Manufacture, Volume 86
      Author(s): Jia-Feng Wu , Rui Zhang , Rui-He Wang , Ying-Xue Yao
      Parallel kinematics machine has attracted attention as machine tools because of the outstanding features of high dynamics and high stiffness. Although various calibration methods for parallel kinematics machine have been studied, the influence of inaccurate motion of joints is rarely considered in these studies. This paper presents a high-accuracy and high-effective approach for calibration of parallel kinematics machine. In the approach, a differential error model, an optimized model and a statistical method are combined, and the errors of parallel kinematics machine due to inaccurate motion of joints can be reduced by this approach. Specifically, the workspace is symmetrically divided into four subspaces, and a measurement method is suggested by a laser tracker to require the actual pose of the platform in these subspaces. An optimized model is proposed to solve the kinematic parameters in symmetrical subspaces, and then arithmetical mean method is proposed to calculate the final kinematic parameter. In order to achieve the global optimum quickly and precisely, the initial value of the optimal parameter is directly solved based on the differential error model. The proposed approach has been realized on the developed 5-DOF hexapod machine tool, and the experiment result proves that the presented method is very effective and accurate for the calibration of the hexapod machine tool.
      Graphical abstract image

      PubDate: 2014-07-27T20:26:40Z
       
  • Fabrication of hybrid micro/nano-textured surfaces using rotary ultrasonic
           machining with one-point diamond tool
    • Abstract: Publication date: November 2014
      Source:International Journal of Machine Tools and Manufacture, Volume 86
      Author(s): Shaolin Xu , Keita Shimada , Masayoshi Mizutani , Tsunemoto Kuriyagawa
      A novel rotary ultrasonic texturing (RUT) technique is proposed to fabricate hybrid periodic micro/nano-textures on flat surfaces. Different from conventional rotary ultrasonic machining, a tailored one-point diamond tool was manufactured and employed for RUT on surfaces of electroless nickel–phosphorus (Ni–P) plating. A one-dimensional longitudinal-vibration mode is used. The combined effect of ultrasonic vibration, rotation and feed motion leads to high-frequency periodic change of cutting edge׳s motion, which is the basic principle for the RUT process. Therefore, to accurately predict and control the texturing process, the cutting locus is firstly mathematically calculated. Hybrid periodic micro/nano-textures comprising linear grooves at the micrometer scale and sinusoidal grooves at the micrometer or nanometer scale were successfully fabricated on machined surfaces, which are in compliance with the results of the mathematical calculations. Different types of surface textures were generated by changing machining conditions. The surface generation mechanism of RUT is illustrated and discussed by analyzing the surface textural features, the cutting locus and the tool tip׳s geometry, including various tool faces, cutting edges, and the cutting corner. The requirements for RUT technique are concluded.


      PubDate: 2014-07-27T20:26:40Z
       
  • Experimental investigation of drilling damage and stitching effects on the
           mechanical behavior of carbon/epoxy composites
    • Abstract: Publication date: Available online 17 July 2014
      Source:International Journal of Machine Tools and Manufacture
      Author(s): Yosra Turki , Malek Habak , Raphaël Velasco , Zoheir Aboura , Kamel Khellil , Pascal Vantomme
      The main purpose of composite materials drilling is the need to put together different parts of a structure, in aeronautics for example. Machining generates damages which affect mechanical properties and have to be taken into account during manufacturing process. The objective of this study is to experimentally analyze the influence of drilling on a carbon/epoxy composite, to investigate the relationships among damages, cutting forces, mechanical properties of the drilled specimens and crack propagation. Stitching and a range of spindle speed and feed have been tested when drilling with a classic twist drill. The effect of each parameter has been assessed in terms of thrust force, moment (during machining) and defects, and then linked to mechanical test results. Experimental results have shown significant influences of feed and composite configuration on delamination. Furthermore, cyclic tensile tests have shown that reducing damage and using stitching help increasing tensile strength.


      PubDate: 2014-07-27T20:26:40Z
       
 
 
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