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Process Performance of Low Frequency Vibratory Grinding of Inconel 718
Available online at www.sciencedirect.com
ScienceDirect Available online atatwww.sciencedirect.com Available online www.sciencedirect.com ScienceDirect Procedia Manufacturing 00 (2018) 000–000 Available online at www.sciencedirect.com www.elsevier.com/locate/procedia Procedia Manufacturing 00 (2018) 000–000 ScienceDirect ScienceDirect 14th Global CongressScienceDirect on Manufacturing and Management (GCMM-2018) www.elsevier.com/locate/procedia Procedia Manufacturing 30 (2019) 530–535 Procedia Manufacturing 00 (2017) 000–000 14th Global Congress on Manufacturing and Management (GCMM-2018) Procedia Manufacturing 00 (2018)Frequency 000–000 Process Performance of Low Vibratory www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia Grinding Inconel 718 Vibratory Process ofofLow Frequency 14th Global Performance Congress on Manufacturing and Management (GCMM-2018) Inconel 718 E. E. Ibrahim, M. Grinding Checkley, X. of M. Sharp, W. Liang, S. Yuan**, Process Performance ofChen, Low Frequency Vibratory ** A. D.L. Batako* E. E.Engineering Ibrahim, M.Society Checkley, X. of Chen, M. Sharp, W. Liang, S. Yuan , 28-30 June Manufacturing International Conference 2017, MESIC 2017, Grinding Inconel 718 2017, Vigo (Pontevedra), Spain Available online at www.sciencedirect.com
Engineering & Technology Research Institute, Liverpool John Moores University, Byrom Street Liverpool, A. D.L. Batako* L3 3AF, UK ** E. E. Ibrahim, M. Checkley, X. Chen, M. Sharp, W. Liang, S. Yuan , **School MechanicalResearch Engineering and Automation Beihang University, Beijing 100191, Engineering &ofTechnology Institute, Liverpool John Moores University, Byrom StreetChina Liverpool, L3 3AF, UK A. Automation D.L. Batako* **School of Mechanical Engineering and Beihang University, Beijing 100191, China Abstract Engineering & Technology Research Institute, Liverpool John Moores University, Byrom Street Liverpool, L3 3AF, UK aindustryand a,* bjet engine Beijing b100191, Inconel**is used largely aerospace forAutomation the manufacturing ofUniversity, components, where high heat Abstract School of Mechanical Engineering China A.inSantana , P. Afonso , A.Beihang Zanin , R. Wernke resistance materials are preferred. Inconel has special properties such as high strength to weight ratio, low University of Minho, Portugal thermal is conductivity poor amachinability. This has led Guimarães, to numerous researches into the machinability of Inconel used largelyand in aerospace industry for the4800-058 manufacturing of jet engine components, where high heat b Unochapecó, 89809-000 Chapecó, SC, Brazil Abstract resistance materials areposes preferred. Inconeltohas special properties such as high strength to weight ratio,here, low this material that still challenges unexperienced new manufacturers. The work presented employs conductivity low frequency oscillation to induce vibratory grinding of Inconel 718 reduced coolant thermal and poor machinability. This has led to numerous researches intowith the machinability of Inconel is used largely aerospace for the manufacturing of jetwheel enginewas components, where highhere, heat application at that very lowin pressure. Aindustry porous oxide-grinding usedwork for the experimental this material still poses challenges to aluminium unexperienced new manufacturers. The presented resistance materials are oscillations. preferred. Inconel has special properties such high to weight low employs oscillation to induce vibratory grinding of as Inconel 718 with reduced coolant work withlow andfrequency without The experimental results showed that the strength superimposition of ratio, vibration Abstract thermal and poorperformance. machinability. This has led to numerous researches into forces the the machinability of improvedconductivity the process reduction of over 30% in wheel grinding was recorded, application at overall very low pressure. A porousAaluminium oxide-grinding wascutting used for experimental this still wheel poses challenges new manufacturers. The work presented here, work with an andthat without oscillations. The to experimental results showed that the superimposition of quality. vibration alongmaterial extended life, increase inunexperienced material removal rate and improved surface roughness Under the concept "Industry 4.0", production processes will30% be in pushed be increasingly interconnected, employs low frequency oscillation to induce vibratory grinding of Inconeltocutting 718 with reduced coolant improved the of overall process performance. A reduction of over grinding forces was recorded, information based on a real time basis and, necessarily, much more efficient. In this context, capacity optimization application at extended very lowwheel pressure. porousinaluminium oxide-grinding wheel wassurface used for the experimental along with an life, A increase material removal rate and improved roughness quality. goes beyond the traditional aim of capacity maximization, contributing alsothat forthe organization’s profitability and value. work with and without oscillations. The experimental results showed superimposition of vibration © 2018 The Authors. Published by Elsevier Ltd. performance. A reduction license ofapproaches over (30% insuggest grinding capacity cutting forces was recorded, Indeed, improved lean ismanagement and continuous improvement optimization instead of https://creativecommons.org/licenses/byThis an the openoverall accessprocess article under the CC BY-NC-ND along with extended wheel life, increase material removal rate andisimproved surfaceresearch roughness quality. nc-nd/4.0/ ) study © 2018 Thean Authors. by Elsevier in Ltd. maximization. The of Published capacity optimization and costing models an important topic that deserves Selection peer-review under responsibility of the scientific committee of the 14th Global Congress on https://creativecommons.org/licenses/byThis isfrom an and open access article under the CC BY-NC-ND license (This contributions both the practical and theoretical perspectives. paper presents and discusses a mathematical © 2019 The) Authors. Published by Elsevier Ltd. nc-nd/4.0/ Manufacturing and Management (GCMM-2018). model for capacity management based on different costing models (ABC and TDABC). A generic model has been This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) © and 2018itThe byresponsibility Elsevier Selection andAuthors. peer-review under the scientific committee of the 14th Global Congress on developed was to Published analyze idle capacityLtd. andof design strategies towards the14th maximization of organization’s Selection andused peer-review under responsibility oftothe scientific committee of the Global Congress on Keywords: cutting forces, wheel wear, nickel alloy This is an vibration, open and access articlegrinding, under the CC BY-NC-ND license (https://creativecommons.org/licenses/byManufacturing Management (GCMM-2018). Manufacturing andresonance Management (GCMM-2018). value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown that capacity nc-nd/4.0/) optimization mightand hide operational inefficiency. Keywords: vibration, resonanceunder grinding, cutting forces,ofwheel wear, nickelcommittee alloy Selection peer-review responsibility the scientific of the 14th Global Congress on © 2017 The Authors. Published by Elsevier B.V. Manufacturing and Management (GCMM-2018). 1. Introduction Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference 2017. Keywords: vibration, resonance grinding, cutting forces, wheel wear, nickel alloy
Costing models for capacity optimization in Industry 4.0: Trade-off between used capacity and operational efficiency
1. Introduction Aerospace industry utilises mainly two alloys for aero-engine parts, that are titanium and nickel based alloys. Titanium alloys have excellent strength and density Keywords: Cost Models; ABC; TDABC;based Capacity Management; Idle Capacity; Operational Efficiencyenabling to be used for the Aerospace utilises mainly twocompression alloys for aero-engine are titaniumnickel-based and nickel first part of industry the turbine, where only air takes place. parts, At highthat temperatures, 1. Introduction based alloys. Titanium alloys have excellent strength and density enabling High to be used for the super alloy with muchbased higher temperature resistance is used. For example, temperature first part alloy of thelike turbine, where isonly air compression place. At high temperatures, nickel-based titanium Ti-6Al-4V employed for static takes and rotating components in gas turbine engines. 1. Introduction Aerospace utilises mainly two alloysresistance for aero-engine are titanium and nickel super alloyindustry with much higher temperature is used.parts, For that example, High temperature based alloys. Titanium based alloys have excellent strength and density enabling to turbine be usedengines. for the titanium alloy like Ti-6Al-4V is employed for static and rotating components in gas The cost idleofcapacity is a fundamental information for companies extreme importance firstofpart the turbine, where only air compression takes place.and Attheir highmanagement temperatures,ofnickel-based in modern production systems. In general, it is defined as unused capacity production potential can be measured super alloy with much higher temperature resistance is used.or For example, High and temperature in several ways: tons of production, available hours of manufacturing, etc. The management of the idle capacity titanium alloy like Ti-6Al-4V is employed for static and rotating components in gas turbine engines. * Corresponding author E-mail address: [email protected]
* Paulo Afonso. Tel.: +351 253 510 761; fax: +351 253 604 741 E-mail address: [email protected] * Corresponding E-mail Published address: [email protected] 2351-9789 © 2018 author The Authors. by Elsevier Ltd. This is an open access article under the CC BY-NC-ND 2351-9789 © 2017 The Authors. Published by Elsevier B.V. Ltd. license (https://creativecommons.org/licenses/by-nc-nd/4.0/) 2351-9789Selection © 2019 and Thepeer-review Authors. Published by Elsevier under responsibility of of thethe scientific committee of the 14thSociety GlobalInternational Congress on Conference Manufacturing 2351-9789 © 2018 The Authors. Published by Elsevier Ltd. Peer-review underaccess responsibility of the scientific committee Manufacturing Engineering 2017. This is an open article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) and Management (GCMM-2018). * Corresponding author E-mail address: [email protected] This is an open access article under theofCC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility the scientific committee of the 14th Global Congress on Manufacturing and Management Selection and peer-review under responsibility of the scientific committee of the 14th Global Congress on Manufacturing (GCMM-2018). and Management 10.1016/j.promfg.2019.02.075 2351-9789 © 2018(GCMM-2018). The Authors. Published by Elsevier Ltd.
This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of the 14th Global Congress on Manufacturing and Management (GCMM-2018).
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Ibrahim et al. / Procedia Manufacturing 00 (2018) 000–000 E.E. Ibrahim et al. / Procedia Manufacturing 30 (2019) 530–535
Fig. 1 depicts the distribution of titanium and nickel alloys employed in the manufacture of an aeroengine, [1]. Here the titanium finds its use in the cooler parts of the engine (fan and compressor) and the nickel based super-alloys run in the hotter parts of the engine (combustor chamber and turbine) [1-6]. All parts of the engine are machined using various techniques, among which grinding plays an important role. However, all aerospace materials are engineered with focus on mechanical and physical properties but with little consideration to machinability. Therefore, the achieved excellent mechanical/physical properties of the aerospace materials make them hard-tomachine, especially, the most preferred high heat resistant, such as Ti-6Al-4V, gamma titanium aluminide and Inconel 718, [2-6].
Fig. 1: Distribution of titanium and nickel alloys in an aero-engine, [1].
Grinding is one of the finishing machining processes that allow the achievement of required dimensions and surface quality of the components. The above-mentioned materials are well-known for their poor machinability due to their gummy properties and bath-tub effect during grinding with inadequate coolant application, [2-6]. Consequently, it is postulated that the introduction of vibration in machining these materials would bring positive effects in terms of machinability and overall performance. The various applications of vibration in manufacturing technology were reported in the 60s by Kumabe [7] who documented the benefits of vibration in machining and other processes. Vibration, used in various technological processes to improve the performance of the machines, intelligently exploits the synergy of the oscillations, where a certain frequency at given amplitude is applied to the cutting tool, the workpiece or to both in addition to the original relative cutting motion between these two to achieve a better performance. Previous study by the authors [8-9] and others [10-12] covered the effects of vibration when applied parallel to the feed direction. Therefore, in this study, low vibration frequency was introduced in a grinding process in the axial direction of the grinding wheel (in the direction perpendicular to the feed). This was done so, as to investigate into the efficiency and performance of vibration applied into a different direction relative to cutting motion. In addition, applying oscillation perpendicular to feed rate allows ignoring the fundamental requirement for gaining the effect of vibratory cutting, that is: vw < 2πaf,
[7, 10],
Here, vw is the work speed, a- is amplitude, and, f- the frequency of the oscillation. When the vibration is applied parallel (same direction) to the feed motion, if the relationship above is true, then a disengagement or a gap is formed between the tool and the workpiece. However, the
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superimposition of oscillation in axial direction i.e. perpendicular to feed, always provides disengagement because, there is no machining motion in this direction. This forms the first advantage of applying oscillation in perpendicular to cutting motion. A fuller account on the findings of this work will be provided in an extended paper to expound the understanding of this exploration. Therefore, here, key results are presented on the study into the effects of axial vibration, which will help in the future design of optimised elliptical oscillatory stages for machining. 2. Experiment configuration This exploratory work started with the design and optimisation of a vibratory stage to generate low frequency oscillations to satisfy the fundamental relationship vw<2πaf and to provide a gap between the tool and the workpiece. The design looked at the performance of an oscillating stage in terms of setting and controlling the amplitude of the oscillation in a wide range from 1-2 m to 500 m peak-to-peak. Such a wide range of operation would be a challenge to achieve with ultrasonic oscillators, which explains the need of high frequency as employed by ultrasonic assisted machining to keep this relationship working. The concept of low frequency oscillator developed here maintains this relationship by actively controlling in real-time the amplitude of oscillation in actual cutting using a closed loop PID controller, [13-14]. This approach is also challenging to achieve in ultrasonic oscillators. The concept of the vibratory stage developed in this work cannot be fully exposed due to intellectual property aspects imposed by the collaborating partners; however, the authors are willing to discuss this with any third party that is interested in this new development. a)
b)
Vibration direction
Fig. 2: oscillator design, a:- amplitude frequency response; b:- actual experimental configuration
The oscillating system is a self-contained stage in which a piezo-electric actuator exerts an oscillatory motion on the workpiece holder in the perpendicular direction to the cutting direction. In designing low frequency oscillators for machining, one needs to consider the natural frequencies of the spindle unit and avoid running at the stage at these frequencies. Therefore, after studying the static, dynamic and frequency response of the spindle unit, key frequencies were as 127Hz and 250Hz as first and second resonance. In the experimentation, depending on the material, the work speed and the wheel type, the amplitude and frequency were selected using Fig.2a, which illustrates the amplitude-frequency response of the oscillating jig; here, 100Hz was selected as the suitable wave of 4V was used at 100Hz to induce 130 m oscillation of the workpiece during machining. To keep the oscillation amplitude constant -time closed loop controller [13-14] was developed using a target PC based on the Compact Rio of National instrument using FPGA
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that operated on the backbone of Labview. To keep a constant amplitude, the controller may use the acceleration, the cutting force or the displacement, depending on what is given as set point. Fig.2b shows the actual experiment configuration with key elements. The following parameters were used for the actual grinding experiments, using standard alumina grinding wheel. Wheel Type: Wheel Speed: Work Speed: Grinding Condition: Workpiece Material: Cut Type: Depth of Dressing: Depth of Cuts: Vibration Frequency: Vibration Amplitude:
VU33 A602HH 10VB 17m/s 250mm/s Wet Condition Nickel Inconel 718 Up grinding, 14 µm/ Single Point 15, 20, 25, 30 100 Hz 130 µm
3. RESULTS AND DISCUSSIONS 3.1 Cutting forces In this investigation, a wide range of experiments was undertaken involving three types of aerospace materials, one type of grinding wheel along with a range of process parameters. This necessitated the use of Taguchi experimental design, which was followed by a refined and detailed experiment. However, since this was a collaborative industry project only the results of the Nickel 718 are presented here. An overall observation is that the application of low frequency vibration onto grinding resulted in a reduction in cutting forces by 30-40% on average. a)
b)
Fig. 3: Grinding as function of depth of cuts: a.- Normal, b.- Tangential
Fig. 3 portrays the cutting forces in grinding the Inconel 718 as a function of the applied depth of cuts, where increasing the depth of cut led to an increase in grinding forces due to the increase in the average chip thickness. However, it is seen here that, the superimposed vibration performed better by 30-40 % over conventional grinding. In addition, the conventional grinding produced poor finishing with chatter marks and burnishing on the ground surface. The reduced cutting forces entails low power consumption, which was on average 42% less than conventional in terms of specific grinding. The vibratory grinding secured an average specific grinding energy of 19 J/mm3/mm/ 3.2 Wheel wear and Surface Roughness In machining, tool wear has an important effect on dimension holding and workpiece surface quality. Therefore, efforts are made in controlling process parameters so that not to induce tool
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wear. This is because tool wear leads to thermal damages and subsequent residual stresses that will affect the performance of the workpiece during its service. In this study, a conventional alumina (VU33 A602HH 10VB), relatively friable wheel was used. Therefore, wheel wear was looked at along with the surface roughness of the ground parts. It is true that surface roughness depends on the wheel type, workpiece material and dressing strategy. However, referring to all data recorded in this study, the superimposed vibration onto the grinding process secured 20-30% improvement in surface quality as illustrated in Fig.4.
Fig.4: Surface roughness as function of Depth of Cut
To characterise the process performance in terms of wheel wear, the material removed and subsequently the material removal rated, a range of grinding tests were undertaken. After grinding over 1mm off the Inconel 718 material in several passes, it was observed that the wheel stayed clean without clogging. During these experiments, samples of titanium alloy Ti-6Al-4V were also ground for wheel wear performance. Fig. 5a depicts the material removed as a function of applied depth of cuts. Fig. 5b illustrates the wheel wear, where it is seen that nickel alloy has high wear as it sticks to the wheel, breaks and pulls out the grains more than titanium. The vibratory grinding outperformed conventional grinding 25-35%.
a)
b)
Fig. 5: Wheel wear; a.- Material Removal; b.- Grinding ratio (G-ratio)
3.3. Discussion In vibration assisted machining, be it milling, drilling or grinding, to get a positive effect of the vibration the process must fulfil the condition vw<2πaf as stated by Kumabe [7] in the 60’s. This has led to the pursuit of applying very frequency (ultrasonic), which is reaching 40 kHz from recent data. However, the authors have notice that this condition is not necessary for the vibration to bring positive effect. The supporting fact of this argument is the vibro-impact drills and construction jack hammer drill, where the tool is pressed against the medium constantly whilst superimposing
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impacts on the tool. Therefore, it is possible to achieve good results with low frequency with or without fulfilling this fundamental condition. On the one hand, the outperformance of the vibratory process over conventional one is due to the successive impulses generated by the vibration causing the material to respond dynamically rather than statically. On the other hand, the extended tool life is explained by the relief that cutting edges experience in between the cycles. In terms of thermal load, if vibration generates a gap between the tool and the medium, the coolant enters the cutting zone and removes the heat that would have been accumulated otherwise in conventional process. This understanding is one of the contributions to the knowledge of vibro-impact process. However, the further analysis of the recorded data is bringing better understanding of why vibration works. 5. Conclusion This work has shown that vibratory process at low frequency brings positive results in grinding hard-to-machine aerospace materials. The superimposed vibration provided an overall 35-40% reduction in cutting force with subsequent reduction in power requirement. In terms of surface quality 20-30% improvement was achieved and 25-35% increase in wheel life was demonstrated. References [1] D. Rugg, The Current Status of Titanium Alloy Use in aero-Engines, Proceedings of the 10th World conference on Titanium (Ti-2003). Hamburg, Germany, Vol. IV (2003) 2727-2735 [2] U. Teicher, A. Ghosh, On the grindability of Titanium alloy by brazed type monolayered superabrasive grinding wheels. Int. J of machine tools and manufacture, 46(6) (2006) 620-622 [3] M.P. Hitchiner, Technological Advances in Creep Feed Grinding of Super alloys with CBN, 3 rd International Machining and grinding Conference, SME, Cincinnati, Ohio, October 4-7, 1999. [4] W.E. Voice E.F.J. Henderson, M. Sheton and X. Wu, Gamma Titanium Aluminide-TNB, Intermetalics, 13 (2005) 959-964, ISSN:0966-9795 [5] S. T. Tawakoli, High efficiency deep grinding (HEDG) of Inconel and other materials, Super abrasives 85, conference 22-25 April, Chicago, Illinois, (1985) 4-67. [6] A.R. Zareen, Y.S. Wong, High speed machining of aerospace alloy Ti-6Al-4V, society for advancement of material and process engineering conference, (2001). [7] J. Kumabe, Vibrating Cutting, (1979, Japanese), (Russian translation), Moscow, Mashinostroenie, 1985 [8] V. Tsiakoumis, An investigation into Vibration assisted Machining – Application to surface grinding Processes, PhD thesis LJMU, (2011). [9] A. D. L. Batako, V. Tsiakoumis, An experimental investigation into resonance dry grinding of hardened steel and nickel alloys with element of MQL, Int J Adv. Manuf. Technol., (2014) 77:27–41. [10] V.I. Babitsky, A.N. Kalashnikov, A. Meadows, A.A.H.P. Wijesundarac, Ultrasonically assisted turning of aviation materials. J Mater Process Technol., 132 (2003) 157–167. [11] T. Moriwaki and E. Shamoto, Ultraprecision Diamond Turning of stainless steel by applying ultrasonic Vibration, Annals of the CIRP, 40 (1991) 559-562 [12] P.M. Mahaddalkar, M.H. Miller, Force and thermal effects in vibration-assisted grinding. Int J Adv Manuf. Technol. 71 (2014)117-1122. [13] H. Eward, Development of A closed Loop Control System for Vibration Assisted Grinding, PhD thesis LJMU, (2016). [14] W.N. Alharbi, Development of a Closed Loop Control System for Vibratory Milling, PhD thesis LJMU, (2018).
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ScienceDirect Available online atatwww.sciencedirect.com Available online www.sciencedirect.com ScienceDirect Procedia Manufacturing 00 (2018) 000–000 Available online at www.sciencedirect.com www.elsevier.com/locate/procedia Procedia Manufacturing 00 (2018) 000–000 ScienceDirect ScienceDirect 14th Global CongressScienceDirect on Manufacturing and Management (GCMM-2018) www.elsevier.com/locate/procedia Procedia Manufacturing 30 (2019) 530–535 Procedia Manufacturing 00 (2017) 000–000 14th Global Congress on Manufacturing and Management (GCMM-2018) Procedia Manufacturing 00 (2018)Frequency 000–000 Process Performance of Low Vibratory www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia Grinding Inconel 718 Vibratory Process ofofLow Frequency 14th Global Performance Congress on Manufacturing and Management (GCMM-2018) Inconel 718 E. E. Ibrahim, M. Grinding Checkley, X. of M. Sharp, W. Liang, S. Yuan**, Process Performance ofChen, Low Frequency Vibratory ** A. D.L. Batako* E. E.Engineering Ibrahim, M.Society Checkley, X. of Chen, M. Sharp, W. Liang, S. Yuan , 28-30 June Manufacturing International Conference 2017, MESIC 2017, Grinding Inconel 718 2017, Vigo (Pontevedra), Spain Available online at www.sciencedirect.com
Engineering & Technology Research Institute, Liverpool John Moores University, Byrom Street Liverpool, A. D.L. Batako* L3 3AF, UK ** E. E. Ibrahim, M. Checkley, X. Chen, M. Sharp, W. Liang, S. Yuan , **School MechanicalResearch Engineering and Automation Beihang University, Beijing 100191, Engineering &ofTechnology Institute, Liverpool John Moores University, Byrom StreetChina Liverpool, L3 3AF, UK A. Automation D.L. Batako* **School of Mechanical Engineering and Beihang University, Beijing 100191, China Abstract Engineering & Technology Research Institute, Liverpool John Moores University, Byrom Street Liverpool, L3 3AF, UK aindustryand a,* bjet engine Beijing b100191, Inconel**is used largely aerospace forAutomation the manufacturing ofUniversity, components, where high heat Abstract School of Mechanical Engineering China A.inSantana , P. Afonso , A.Beihang Zanin , R. Wernke resistance materials are preferred. Inconel has special properties such as high strength to weight ratio, low University of Minho, Portugal thermal is conductivity poor amachinability. This has led Guimarães, to numerous researches into the machinability of Inconel used largelyand in aerospace industry for the4800-058 manufacturing of jet engine components, where high heat b Unochapecó, 89809-000 Chapecó, SC, Brazil Abstract resistance materials areposes preferred. Inconeltohas special properties such as high strength to weight ratio,here, low this material that still challenges unexperienced new manufacturers. The work presented employs conductivity low frequency oscillation to induce vibratory grinding of Inconel 718 reduced coolant thermal and poor machinability. This has led to numerous researches intowith the machinability of Inconel is used largely aerospace for the manufacturing of jetwheel enginewas components, where highhere, heat application at that very lowin pressure. Aindustry porous oxide-grinding usedwork for the experimental this material still poses challenges to aluminium unexperienced new manufacturers. The presented resistance materials are oscillations. preferred. Inconel has special properties such high to weight low employs oscillation to induce vibratory grinding of as Inconel 718 with reduced coolant work withlow andfrequency without The experimental results showed that the strength superimposition of ratio, vibration Abstract thermal and poorperformance. machinability. This has led to numerous researches into forces the the machinability of improvedconductivity the process reduction of over 30% in wheel grinding was recorded, application at overall very low pressure. A porousAaluminium oxide-grinding wascutting used for experimental this still wheel poses challenges new manufacturers. The work presented here, work with an andthat without oscillations. The to experimental results showed that the superimposition of quality. vibration alongmaterial extended life, increase inunexperienced material removal rate and improved surface roughness Under the concept "Industry 4.0", production processes will30% be in pushed be increasingly interconnected, employs low frequency oscillation to induce vibratory grinding of Inconeltocutting 718 with reduced coolant improved the of overall process performance. A reduction of over grinding forces was recorded, information based on a real time basis and, necessarily, much more efficient. In this context, capacity optimization application at extended very lowwheel pressure. porousinaluminium oxide-grinding wheel wassurface used for the experimental along with an life, A increase material removal rate and improved roughness quality. goes beyond the traditional aim of capacity maximization, contributing alsothat forthe organization’s profitability and value. work with and without oscillations. The experimental results showed superimposition of vibration © 2018 The Authors. Published by Elsevier Ltd. performance. A reduction license ofapproaches over (30% insuggest grinding capacity cutting forces was recorded, Indeed, improved lean ismanagement and continuous improvement optimization instead of https://creativecommons.org/licenses/byThis an the openoverall accessprocess article under the CC BY-NC-ND along with extended wheel life, increase material removal rate andisimproved surfaceresearch roughness quality. nc-nd/4.0/ ) study © 2018 Thean Authors. by Elsevier in Ltd. maximization. The of Published capacity optimization and costing models an important topic that deserves Selection peer-review under responsibility of the scientific committee of the 14th Global Congress on https://creativecommons.org/licenses/byThis isfrom an and open access article under the CC BY-NC-ND license (This contributions both the practical and theoretical perspectives. paper presents and discusses a mathematical © 2019 The) Authors. Published by Elsevier Ltd. nc-nd/4.0/ Manufacturing and Management (GCMM-2018). model for capacity management based on different costing models (ABC and TDABC). A generic model has been This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) © and 2018itThe byresponsibility Elsevier Selection andAuthors. peer-review under the scientific committee of the 14th Global Congress on developed was to Published analyze idle capacityLtd. andof design strategies towards the14th maximization of organization’s Selection andused peer-review under responsibility oftothe scientific committee of the Global Congress on Keywords: cutting forces, wheel wear, nickel alloy This is an vibration, open and access articlegrinding, under the CC BY-NC-ND license (https://creativecommons.org/licenses/byManufacturing Management (GCMM-2018). Manufacturing andresonance Management (GCMM-2018). value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown that capacity nc-nd/4.0/) optimization mightand hide operational inefficiency. Keywords: vibration, resonanceunder grinding, cutting forces,ofwheel wear, nickelcommittee alloy Selection peer-review responsibility the scientific of the 14th Global Congress on © 2017 The Authors. Published by Elsevier B.V. Manufacturing and Management (GCMM-2018). 1. Introduction Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference 2017. Keywords: vibration, resonance grinding, cutting forces, wheel wear, nickel alloy
Costing models for capacity optimization in Industry 4.0: Trade-off between used capacity and operational efficiency
1. Introduction Aerospace industry utilises mainly two alloys for aero-engine parts, that are titanium and nickel based alloys. Titanium alloys have excellent strength and density Keywords: Cost Models; ABC; TDABC;based Capacity Management; Idle Capacity; Operational Efficiencyenabling to be used for the Aerospace utilises mainly twocompression alloys for aero-engine are titaniumnickel-based and nickel first part of industry the turbine, where only air takes place. parts, At highthat temperatures, 1. Introduction based alloys. Titanium alloys have excellent strength and density enabling High to be used for the super alloy with muchbased higher temperature resistance is used. For example, temperature first part alloy of thelike turbine, where isonly air compression place. At high temperatures, nickel-based titanium Ti-6Al-4V employed for static takes and rotating components in gas turbine engines. 1. Introduction Aerospace utilises mainly two alloysresistance for aero-engine are titanium and nickel super alloyindustry with much higher temperature is used.parts, For that example, High temperature based alloys. Titanium based alloys have excellent strength and density enabling to turbine be usedengines. for the titanium alloy like Ti-6Al-4V is employed for static and rotating components in gas The cost idleofcapacity is a fundamental information for companies extreme importance firstofpart the turbine, where only air compression takes place.and Attheir highmanagement temperatures,ofnickel-based in modern production systems. In general, it is defined as unused capacity production potential can be measured super alloy with much higher temperature resistance is used.or For example, High and temperature in several ways: tons of production, available hours of manufacturing, etc. The management of the idle capacity titanium alloy like Ti-6Al-4V is employed for static and rotating components in gas turbine engines. * Corresponding author E-mail address: [email protected]
* Paulo Afonso. Tel.: +351 253 510 761; fax: +351 253 604 741 E-mail address: [email protected] * Corresponding E-mail Published address: [email protected] 2351-9789 © 2018 author The Authors. by Elsevier Ltd. This is an open access article under the CC BY-NC-ND 2351-9789 © 2017 The Authors. Published by Elsevier B.V. Ltd. license (https://creativecommons.org/licenses/by-nc-nd/4.0/) 2351-9789Selection © 2019 and Thepeer-review Authors. Published by Elsevier under responsibility of of thethe scientific committee of the 14thSociety GlobalInternational Congress on Conference Manufacturing 2351-9789 © 2018 The Authors. Published by Elsevier Ltd. Peer-review underaccess responsibility of the scientific committee Manufacturing Engineering 2017. This is an open article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) and Management (GCMM-2018). * Corresponding author E-mail address: [email protected] This is an open access article under theofCC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility the scientific committee of the 14th Global Congress on Manufacturing and Management Selection and peer-review under responsibility of the scientific committee of the 14th Global Congress on Manufacturing (GCMM-2018). and Management 10.1016/j.promfg.2019.02.075 2351-9789 © 2018(GCMM-2018). The Authors. Published by Elsevier Ltd.
This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of the 14th Global Congress on Manufacturing and Management (GCMM-2018).
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Fig. 1 depicts the distribution of titanium and nickel alloys employed in the manufacture of an aeroengine, [1]. Here the titanium finds its use in the cooler parts of the engine (fan and compressor) and the nickel based super-alloys run in the hotter parts of the engine (combustor chamber and turbine) [1-6]. All parts of the engine are machined using various techniques, among which grinding plays an important role. However, all aerospace materials are engineered with focus on mechanical and physical properties but with little consideration to machinability. Therefore, the achieved excellent mechanical/physical properties of the aerospace materials make them hard-tomachine, especially, the most preferred high heat resistant, such as Ti-6Al-4V, gamma titanium aluminide and Inconel 718, [2-6].
Fig. 1: Distribution of titanium and nickel alloys in an aero-engine, [1].
Grinding is one of the finishing machining processes that allow the achievement of required dimensions and surface quality of the components. The above-mentioned materials are well-known for their poor machinability due to their gummy properties and bath-tub effect during grinding with inadequate coolant application, [2-6]. Consequently, it is postulated that the introduction of vibration in machining these materials would bring positive effects in terms of machinability and overall performance. The various applications of vibration in manufacturing technology were reported in the 60s by Kumabe [7] who documented the benefits of vibration in machining and other processes. Vibration, used in various technological processes to improve the performance of the machines, intelligently exploits the synergy of the oscillations, where a certain frequency at given amplitude is applied to the cutting tool, the workpiece or to both in addition to the original relative cutting motion between these two to achieve a better performance. Previous study by the authors [8-9] and others [10-12] covered the effects of vibration when applied parallel to the feed direction. Therefore, in this study, low vibration frequency was introduced in a grinding process in the axial direction of the grinding wheel (in the direction perpendicular to the feed). This was done so, as to investigate into the efficiency and performance of vibration applied into a different direction relative to cutting motion. In addition, applying oscillation perpendicular to feed rate allows ignoring the fundamental requirement for gaining the effect of vibratory cutting, that is: vw < 2πaf,
[7, 10],
Here, vw is the work speed, a- is amplitude, and, f- the frequency of the oscillation. When the vibration is applied parallel (same direction) to the feed motion, if the relationship above is true, then a disengagement or a gap is formed between the tool and the workpiece. However, the
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superimposition of oscillation in axial direction i.e. perpendicular to feed, always provides disengagement because, there is no machining motion in this direction. This forms the first advantage of applying oscillation in perpendicular to cutting motion. A fuller account on the findings of this work will be provided in an extended paper to expound the understanding of this exploration. Therefore, here, key results are presented on the study into the effects of axial vibration, which will help in the future design of optimised elliptical oscillatory stages for machining. 2. Experiment configuration This exploratory work started with the design and optimisation of a vibratory stage to generate low frequency oscillations to satisfy the fundamental relationship vw<2πaf and to provide a gap between the tool and the workpiece. The design looked at the performance of an oscillating stage in terms of setting and controlling the amplitude of the oscillation in a wide range from 1-2 m to 500 m peak-to-peak. Such a wide range of operation would be a challenge to achieve with ultrasonic oscillators, which explains the need of high frequency as employed by ultrasonic assisted machining to keep this relationship working. The concept of low frequency oscillator developed here maintains this relationship by actively controlling in real-time the amplitude of oscillation in actual cutting using a closed loop PID controller, [13-14]. This approach is also challenging to achieve in ultrasonic oscillators. The concept of the vibratory stage developed in this work cannot be fully exposed due to intellectual property aspects imposed by the collaborating partners; however, the authors are willing to discuss this with any third party that is interested in this new development. a)
b)
Vibration direction
Fig. 2: oscillator design, a:- amplitude frequency response; b:- actual experimental configuration
The oscillating system is a self-contained stage in which a piezo-electric actuator exerts an oscillatory motion on the workpiece holder in the perpendicular direction to the cutting direction. In designing low frequency oscillators for machining, one needs to consider the natural frequencies of the spindle unit and avoid running at the stage at these frequencies. Therefore, after studying the static, dynamic and frequency response of the spindle unit, key frequencies were as 127Hz and 250Hz as first and second resonance. In the experimentation, depending on the material, the work speed and the wheel type, the amplitude and frequency were selected using Fig.2a, which illustrates the amplitude-frequency response of the oscillating jig; here, 100Hz was selected as the suitable wave of 4V was used at 100Hz to induce 130 m oscillation of the workpiece during machining. To keep the oscillation amplitude constant -time closed loop controller [13-14] was developed using a target PC based on the Compact Rio of National instrument using FPGA
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that operated on the backbone of Labview. To keep a constant amplitude, the controller may use the acceleration, the cutting force or the displacement, depending on what is given as set point. Fig.2b shows the actual experiment configuration with key elements. The following parameters were used for the actual grinding experiments, using standard alumina grinding wheel. Wheel Type: Wheel Speed: Work Speed: Grinding Condition: Workpiece Material: Cut Type: Depth of Dressing: Depth of Cuts: Vibration Frequency: Vibration Amplitude:
VU33 A602HH 10VB 17m/s 250mm/s Wet Condition Nickel Inconel 718 Up grinding, 14 µm/ Single Point 15, 20, 25, 30 100 Hz 130 µm
3. RESULTS AND DISCUSSIONS 3.1 Cutting forces In this investigation, a wide range of experiments was undertaken involving three types of aerospace materials, one type of grinding wheel along with a range of process parameters. This necessitated the use of Taguchi experimental design, which was followed by a refined and detailed experiment. However, since this was a collaborative industry project only the results of the Nickel 718 are presented here. An overall observation is that the application of low frequency vibration onto grinding resulted in a reduction in cutting forces by 30-40% on average. a)
b)
Fig. 3: Grinding as function of depth of cuts: a.- Normal, b.- Tangential
Fig. 3 portrays the cutting forces in grinding the Inconel 718 as a function of the applied depth of cuts, where increasing the depth of cut led to an increase in grinding forces due to the increase in the average chip thickness. However, it is seen here that, the superimposed vibration performed better by 30-40 % over conventional grinding. In addition, the conventional grinding produced poor finishing with chatter marks and burnishing on the ground surface. The reduced cutting forces entails low power consumption, which was on average 42% less than conventional in terms of specific grinding. The vibratory grinding secured an average specific grinding energy of 19 J/mm3/mm/ 3.2 Wheel wear and Surface Roughness In machining, tool wear has an important effect on dimension holding and workpiece surface quality. Therefore, efforts are made in controlling process parameters so that not to induce tool
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wear. This is because tool wear leads to thermal damages and subsequent residual stresses that will affect the performance of the workpiece during its service. In this study, a conventional alumina (VU33 A602HH 10VB), relatively friable wheel was used. Therefore, wheel wear was looked at along with the surface roughness of the ground parts. It is true that surface roughness depends on the wheel type, workpiece material and dressing strategy. However, referring to all data recorded in this study, the superimposed vibration onto the grinding process secured 20-30% improvement in surface quality as illustrated in Fig.4.
Fig.4: Surface roughness as function of Depth of Cut
To characterise the process performance in terms of wheel wear, the material removed and subsequently the material removal rated, a range of grinding tests were undertaken. After grinding over 1mm off the Inconel 718 material in several passes, it was observed that the wheel stayed clean without clogging. During these experiments, samples of titanium alloy Ti-6Al-4V were also ground for wheel wear performance. Fig. 5a depicts the material removed as a function of applied depth of cuts. Fig. 5b illustrates the wheel wear, where it is seen that nickel alloy has high wear as it sticks to the wheel, breaks and pulls out the grains more than titanium. The vibratory grinding outperformed conventional grinding 25-35%.
a)
b)
Fig. 5: Wheel wear; a.- Material Removal; b.- Grinding ratio (G-ratio)
3.3. Discussion In vibration assisted machining, be it milling, drilling or grinding, to get a positive effect of the vibration the process must fulfil the condition vw<2πaf as stated by Kumabe [7] in the 60’s. This has led to the pursuit of applying very frequency (ultrasonic), which is reaching 40 kHz from recent data. However, the authors have notice that this condition is not necessary for the vibration to bring positive effect. The supporting fact of this argument is the vibro-impact drills and construction jack hammer drill, where the tool is pressed against the medium constantly whilst superimposing
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impacts on the tool. Therefore, it is possible to achieve good results with low frequency with or without fulfilling this fundamental condition. On the one hand, the outperformance of the vibratory process over conventional one is due to the successive impulses generated by the vibration causing the material to respond dynamically rather than statically. On the other hand, the extended tool life is explained by the relief that cutting edges experience in between the cycles. In terms of thermal load, if vibration generates a gap between the tool and the medium, the coolant enters the cutting zone and removes the heat that would have been accumulated otherwise in conventional process. This understanding is one of the contributions to the knowledge of vibro-impact process. However, the further analysis of the recorded data is bringing better understanding of why vibration works. 5. Conclusion This work has shown that vibratory process at low frequency brings positive results in grinding hard-to-machine aerospace materials. The superimposed vibration provided an overall 35-40% reduction in cutting force with subsequent reduction in power requirement. In terms of surface quality 20-30% improvement was achieved and 25-35% increase in wheel life was demonstrated. References [1] D. Rugg, The Current Status of Titanium Alloy Use in aero-Engines, Proceedings of the 10th World conference on Titanium (Ti-2003). Hamburg, Germany, Vol. IV (2003) 2727-2735 [2] U. Teicher, A. Ghosh, On the grindability of Titanium alloy by brazed type monolayered superabrasive grinding wheels. Int. J of machine tools and manufacture, 46(6) (2006) 620-622 [3] M.P. Hitchiner, Technological Advances in Creep Feed Grinding of Super alloys with CBN, 3 rd International Machining and grinding Conference, SME, Cincinnati, Ohio, October 4-7, 1999. [4] W.E. Voice E.F.J. Henderson, M. Sheton and X. Wu, Gamma Titanium Aluminide-TNB, Intermetalics, 13 (2005) 959-964, ISSN:0966-9795 [5] S. T. Tawakoli, High efficiency deep grinding (HEDG) of Inconel and other materials, Super abrasives 85, conference 22-25 April, Chicago, Illinois, (1985) 4-67. [6] A.R. Zareen, Y.S. Wong, High speed machining of aerospace alloy Ti-6Al-4V, society for advancement of material and process engineering conference, (2001). [7] J. Kumabe, Vibrating Cutting, (1979, Japanese), (Russian translation), Moscow, Mashinostroenie, 1985 [8] V. Tsiakoumis, An investigation into Vibration assisted Machining – Application to surface grinding Processes, PhD thesis LJMU, (2011). [9] A. D. L. Batako, V. Tsiakoumis, An experimental investigation into resonance dry grinding of hardened steel and nickel alloys with element of MQL, Int J Adv. Manuf. Technol., (2014) 77:27–41. [10] V.I. Babitsky, A.N. Kalashnikov, A. Meadows, A.A.H.P. Wijesundarac, Ultrasonically assisted turning of aviation materials. J Mater Process Technol., 132 (2003) 157–167. [11] T. Moriwaki and E. Shamoto, Ultraprecision Diamond Turning of stainless steel by applying ultrasonic Vibration, Annals of the CIRP, 40 (1991) 559-562 [12] P.M. Mahaddalkar, M.H. Miller, Force and thermal effects in vibration-assisted grinding. Int J Adv Manuf. Technol. 71 (2014)117-1122. [13] H. Eward, Development of A closed Loop Control System for Vibration Assisted Grinding, PhD thesis LJMU, (2016). [14] W.N. Alharbi, Development of a Closed Loop Control System for Vibratory Milling, PhD thesis LJMU, (2018).
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