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1、Diamond Cutting of Hardened Steel Molds,Chong Fung Fung(10902795R)Ho Hoi Chau(10664322G)Xiao Gao Bo(11900474R)Zhang Guo Qing(11901723R),Problem definition and objectivesStrategy and methodologyProject significanceConclusion,Outline,Main business of our company,Injection molded plastic optics,Hot pre
2、ssed glass optics,Nickel-plated injection molds,Hardened steel molds,Nickel plated injection molds have long been used for the injection molding of plastic optics.Established process for nickel-plated steel molds:,High speed machining of the steel mold shape.Electroless nickel coating process.Diamon
3、d cutting of the nickel layer.,Disadvantages of nickel-plated molds:nickel plating is very time and cost consuming low hardness and thus short life time low temperature stability can not be used for hot pressing of glass Therefore,Many optics need to be replicated by hardened steel molds.,Establishe
4、d process for manufacturing hardened steel molds:sculpturing of the steel mold by end milling/grinding/EDM polishing to mirror surfaceDisadvantages of this process:low efficiency and high cost polishing cause surface shape deterioration complex surface structure can not be produced,Why not use singl
5、e point diamond turning to replace these stupid processes?,The affinity between the carbon(diamond)and the iron(work piece)leads to excessive tool wear and decreased surface quality in conventional diamond cutting of steel.Therefore,diamond machining is conventionally limited to nonferrous materials
6、.,In order to overcome this problem,extensive research has been conducted in the past 30 years.Methods proposed to reduce tool wear during diamond cutting of steel:cut in carbon saturated atmosphere cryogenic cutting ultrasonic vibration assisted cutting intermittent cutting thermal-chemical modific
7、ation of surface layer,Tool wear can be reduced by up to two orders of magnitude.Diamond machining of steel is ready for industry application.,High alloyed tool steel molds(1200HV)turned by one diamond tool,The objectives of this project:to introduce the technology of diamond machining of steel into
8、 our manufacturing process to build up corresponding quality control system to ensure quality to reduce manufacturing cost and improve product quality,Problem definition and objectivesStrategy and methodologyProject significanceConclusion,Outline,Three approaches with high feasibility for industry a
9、pplication:cut in carbon saturated atmosphere cryogenic cutting ultrasonic vibration assisted cutting intermittent cutting thermal-chemical modification of surface layer,Elliptical vibration cutting,The friction between the chip and the tool rake face is drastically reduced.Cutting force and the cut
10、ting energy are reduced significantly.Intermittent cutting is effective in preventing tool wear and adhesion.,Hardened steel parts machined by ultrasonic vibration cutting,When a diamond tool is actuated in a plane by two sinusoidal waves x(t),y(t),x(t)=a cos(2ft)y(t)=b cos(2ft+)it will moves in an
11、elliptical path.,Schematic illustration of the elliptical vibration cutting.,The vibrator is resonated elliptically at ultrasonic frequency by exciting the two piezoelectric plates with some phase shift.,One type of structure:ultrasonic elliptical vibration tool.,Three organizations have succeeded i
12、n developing ultrasonic vibration cutting devices.Kobe University(Japan)Fraunhofer IPT(Aachen,Germany)SIMTech(Singapore)Both devices from SIMTech and Fraunhofer IPT are used by industry.,Equipments for ultrasonic vibration cutting,Son-X is a spin-off company of Fraunhofer IPT and specializes in prod
13、ucing the ultrasonic vibration tooling system.,The UTS one can be integrated into any commercially available ultra precision machine.Frequency:80 KHz.,SIMTech has developed a compact ultrasonic vibration module able to cut steel(hardness HRC 55)to mirror surface finish(Ra8nm).,Machining setup,Perfor
14、manceSteel workpiece with diameter greater than 40mm in diameter can be machined.Mirror finish of better than 8nm Ra can be obtained.Profile accuracy of 0.15m can be achieved for 10mm diameter samples.,Diamond cut hardened steel inserts,Intermittent cutting-raster milling,Ultra precision raster mill
15、ing is another process that can suppress tool wear during diamond cutting of steel.,5-axis setup of the machine tool,Raster milling of freeform surface,The diamond tool is rotated around the spindle axis while the workpiece is fixed.,Schematic illustration of raster milling process,In ultra-precisio
16、n raster milling,the contact time between diamond tool and workpiece is so short that it has enough time to cool the interface.Thus tool wear can be suppressed.,Machines for raster milling,Freeform 705G,Freeform 700A,Precitech designs and manufactures ultra precision machine tools for turning,millin
17、g,and grinding.Their machines can produce rotationally symmetric,asymmetric,freeform and sculpted geometries.,Form tolerances in the sub-micron range and nanometer surface finishes can be achieved when equipped with diamond tooling.,Moore Nanotechnology Systems,Nanotech 350FG,The Nanotech 350FG is a
18、ble to perform raster fly cutting of freeform,linear diffractive,micro-prismatic optical structures.,Basic idea:avoid chemical reactions between the carbon and iron by establishing a chemical bond between the iron and another chemical element.,Thermal-chemical modification of the surface layer,Nitri
19、ding process has been developed for the thermal mechanical modification of steel and steel alloys.,Cross section of a nitrided 42CrMo4 steel.,Through nitriding the unpaired electrons in the d shell of the iron,which are responsible for the catastrophic diamond tool wear,will be bonded.,Effects of ni
20、tridingDiamond tool wear can be reduced by more than two orders of magnitude.The surface roughness obtained in single point diamond turning of carbon steel was better than 10nm Ra.,Two aspherical hard steel molds diamond turned with one diamond tool.,Nitriding is a surface-hardening heat treatment t
21、hat introduces nitrogen into the surface of steel.,Schematic diagram of plasma nitriding equipments,IONITECH LTD provide a full series of nitriding facilities.,Overview of the nitriding system,Plasma generator,Typically a nitriding system consists of vacuum chamber,plasma generator,vacuum system and
22、 the control system.,Method for quality control,In-situ error measurement and compensation,Ultracomp module for Nanoform 250,In-situ measurement using air bearing LVDT metrology probe,Profile error analysis,In-situ error compensation,In-situ error measurement and error compensation for hardened stee
23、l mold insert.,Diamond cutting of hardened steel would make the pricing and time consuming process of nickel plating unnecessary.,Cost is a major consideration in the modern manufacturing industry.,Take a 30mm diameter mold for example,One diamond tool is able to cut two molds.The diamond tool cost
24、HK$6,000.So the cost for one mold is HK$3000.,One diamond tool is able to cut 200 molds.So tool cost per mold is HK$30.The nickel coating for a 30mm mold is about HK$3000.So the total cost per mold is 3000+30=HK$3030.,Whats more,comparison of average insert molding life,In this sense,one steel mold
25、will bring a total cost reduction of about HK$10,000 in the whole manufacturing process of injection molded optics.,The life time of hardened steel molds is about 35 times longer than nickel plated steel molds.,A nitriding system costs about HK$800,000.This means that the equipment cost will be cove
26、red after producing about 800,000/10,000=80 steel molds.,A ultrasonic tooling unit costs about HK$700,000.The equipment cost will be covered after producing about 700,000/10,000=70 steel molds.,Equipment cost,A 5-axis UPM machine costs about HK$5,000,000.The equipment cost will be covered after prod
27、ucing about 5,000,000/10,000=500 steel molds.,Advantages and limitations of each approach,Recommendation,Ultrasonic vibration assisted cutting has the best performance.Best surface roughness and surface quality achieved.Excellent performance in reducing tool wear.Cheapest cost for equipments.,Theref
28、ore,Ultrasonic vibration assisted cutting is recommended for adoption in our manufacturing process.,Problem definition and objectivesStrategy and methodologyProject significanceConclusion,Outline,Advantages of hardened steel molds:Manufacturing period can be reduced to 1 day from 2 to 4 weeks.The fr
29、equently caused damages by nickel plating within the mould die can be avoided.Higher scratch resistance;no peeling off;no chipping/cracking on sharp edges.Life time is 35 times longer.Higher temperature stability.Molds can be repaired efficiently and without external coating steps.Lower manufacturin
30、g cost.,Significance of this project,Advantages of diamond cutting over conventional processes(grinding and finishing)for producing hardened steel molds:Higher form accuracy.Hardened steel molds with more complex surface structures and small radii cavities can be produced.Higher efficiency and lower
31、 cost.,In summary,with the higher efficiency,lower cost and greater capability brought by the new technology,the competence of our company will be greatly improved.,Problem definition and objectivesStrategy and methodologyProject significanceConclusion,Outline,Conclusion,Three approaches for enablin
32、g the diamond machining of hardened steel molds are introduced and ultrasonic vibration assisted cutting is recommended for adoption.The adoption of this technology will bring higher manufacturing efficiency,lower manufacturing cost and greater manufacturing capability.In conclusion,the adoption of
33、this new technology will give us a decisive lead over our competitors.,1 B.Larisch,U.Brusky and H.J.Spies,Plasma nitriding of stainless steels at low temperatures,Surf.Coat.Technol.,vol.116/119,pp.7,1999.2 E.Brinksmeier and R.Glbe,Advances in Precision Machining of Steel,CIRP Ann.Manuf.Technol.,vol.
34、50,pp.385-388,2001.3 E.Brinksmeier,R.Glbe and J.Osmer,Ultra-Precision Diamond Cutting of Steel Molds,CIRP Ann.Manuf.Technol.,vol.55,pp.551-554,2006.4 E.Brinksmeier and R.Glbe,Basic studies on the wear behaviour of modified and coated diamond tools for precision machining of ferrous materials,in Init
35、iatives of Precision Engineering at the Beginning of a Millennium,I.Inasaki,Ed.Springer US,2002,pp.174-178.5 M.A.Davies,C.J.Evans,R.R.Vohra,B.C.Bergner and S.R.Patterson,Application of precision diamond machining to the manufacture of microphotonics components,in 2003,pp.94-108.6 E.Brinksmeier,Preci
36、sion Machining of Steel with Ultrasonically Driven Chilled Diamond Tools,Proceedings of the 17th Annual ASPE Meeting,pp.275-278,2002.7 E.Brinksmeier,Elliptical vibration cutting of steel with diamond tools,Proceedings of the 14th Annual ASPE Meeting,pp.163-166,1999.,References,8 H.Kim,S.Kim,K.Lee,D.
37、Lee,Y.Bang and K.Lee,Development of a programmable vibration cutting tool for diamond turning of hardened mold steels,The International Journal of Advanced Manufacturing Technology,vol.40,pp.26-40,2009.9 F.Kimura,K.Horio,E.Brinksmeier,O.Riemer and R.Glbe,Merging technologies for optics,in Towards Sy
38、nthesis of Micro-/Nano-SystemsAnonymous Springer London,2007,pp.1-9.10 Norikazu Suzuki,Ultraprecision sculpturing of hardened steel by applying elliptical vibration cutting,.11 J.Osmer,R.Glabe,O.Riemer,E.Brinksmeier,S.Butepage and F.Hoffmann,Diamond milling of nitrided steels for optical mold making
39、,in 2009,pp.1238-1240.12 P.Schellekens,N.Rosielle,H.Vermeulen,M.Vermeulen,S.Wetzels and W.Pril,Design for precision:current status and trends,CIRP Annals,vol.47,pp.30,1998.13 P.Schellekens,N.Rosielle,H.Vermeulen,M.Vermeulen,S.Wetzels and W.Pril,Design for precision:current status and trends,CIRP Ann
40、als,vol.47,pp.30,1998.,14 A.Pramanik,K.S.Neo,M.Rahman,X.P.Li,M.Sawa and Y.Maeda,Cutting performance of diamond tools during ultra-precision turning of electroless-nickel plated die materials,J.Mater.Process.Technol.,vol.140,pp.308-313,9/22,2003.15 A.Sahu,B.B.Nayak,N.Panigrahi,B.S.Acharya and B.C.Moh
41、anty,DC extended arc plasma nitriding of stainless and high carbon steel,J.Mater.Sci.,vol.35,pp.71-77,2000.16 E.Shamoto and T.Moriwaki,Ultraprecision Diamond Cutting of Hardened Steel by Applying Elliptical Vibration Cutting,CIRP Ann.Manuf.Technol.,vol.48,pp.441-444,1999.17 Shi Meirong,Thermo-chemic
42、al Tool Wear in Orthogonal Diamond Cutting Steel and Stainless Steel,.18 Y.Song,K.Nezu,C.Park and T.Moriwaki,Tool wear control in single-crystal diamond cutting of steel by using the ultra-intermittent cutting method,Int.J.Mach.Tools Manuf.,vol.49,pp.339-343,3,2009.19 N.Suzuki,A.Nakamura,E.Shamoto,K
43、.Harada,M.Matsuo and M.Osada,Ultraprecision micromachining of hardened steel by applying ultrasonic elliptical vibration cutting,in Micromechatronics and Human Science,2003.MHS 2003.Proceedings of 2003 International Symposium on,2003,pp.221-226.,20 Y.Tohme,Trends in ultra-precision machining of freeform optical surfaces,in 2008,pp.OThC6.21 http:/http:/www.son-http:/pe-coi.sg/machiningtechnology_inner_1.php24 http:/http:/www.simtech.a-star.edu.sg/simcorp/loadAchievementDetail.do?id=1.1&currId=1.1.4&cid=2162697&pid=4653062,Thanks for your attention,
