ao nfim m6i 2010
Nghien cu'u phat trieif
phifcJng phap lam khuon nhanh tren cd sd cong nghe ghep tam'
VO THI RY, NGUYEN THANH CONG, NGUYEN M^^
Vien May va Dung cu Cong nghiep (Vien IMI)- eMail:imi@hn. vnn. vn
Tom tat
Tao khuon nhanh tren cd sd tam ghep la cong nghe san xuat khuon trite tiep tren cdsdgia cong theo Idp cua rapid prototyping (RP), du'dc cac nu'dc cong nghiep tien pen nhit Anh, Ditc, My... quan tam nghien cCtu trong nhufng nam gan day.
PhUdng phap lam khuon nay giai quyet du'dc cac van de: thdi gian gia cong nhanh, kich cd phoi Idn, hinh dang hinh hoc phUc tap va d$c biet kinh tedoi khuon tam thdi diing cho loat san xuat nhd. Day la nhitng van de ma bat cd' nen cong nghiep nao cung dSu mong muon cd giai phap thich hdp.
Trong nghien c&u nay, nhdm tac gia minh hoa giai phap lam khuon nhanh tren cd sd cong nghe ghep tam phat trien trong nhUng dieu kien vat chat ky thuat nhat djnh ciia Vien IMI. Viec xay dUng phan mem cat Idp cho cac may cat CNC (cSt bing tia laser va tia nUdc ap cao) cd y nghia trong viec phat trien giai phap gia cong lai: cat tam-dap Idp ma nhdm de tai se con tiep tuc nghien cihi trong thdi gian tiep theo.
1- M6 dau
Trong bdi canh "the gidi phang" tat ca cac nen kinh te deu phai chiu sff canh tranh gay gat, kinh te Cong nghiep khdng nam ngoai le. Nhu cau cung cap nhanh den ngffdi tieu dung san pham mdi ddi hdi nganh edng nghiep phai cd nhuYig giai phap edng nghe mdi. Od cung la li do ma edng nghe tao mau nhanh (RP) (rapid protptyping) ngay cang dffdc quan tam va phat trien ffng dung. Ke tff khi cac phffdng phap RP dffdc phat trien (giffa
nhffng nam 80) va nhOTig thiet bj dau tien ve tao mau nhanh dffdc dffa ra thj trffdng, nhieu nha nghien ciAi va san xuat da nghT den cac phffdng phap phat trien tao khuon nhanh san xuat theo loat.
Tren nguyen li tao mau nhanh, cac khuon nhanh bang phffdng phap Stereolithogra- phy (SLA), Selective Laser Sintering (SLS), Laminated Object Manufacturing (LOM) w... da dffdc nghien culi che tao.
Tuy nhien do dac diem cua vat lieu nen nhuYig khuon nay chu yeu la khuon gian tiep (mdc mau). Cuoi the ky 20 mot sd nghien cuU de cap den cac giai phap khac phuc nhffde diem cua RP de che tao khuon trffc tiep da dffdc edng bo. NhiJng
•giai phap cung nhff phan tich de cai thien phffdng phap thffdng tap trung vao cac van de: he thdng gia cong [1, 3-r6], sai sd va bu sai so [7-1-11], dap va ghep Idp [8-;-9], vat lieu [1,2 ]. Lam khuon nhanh bang kim loai tam la mot trong cac giai phap khac phuc nhffde diem ve vat lieu cua RT.
2. Phat trien khuon nhanh tren cd sd cong nghe ghep tarn
Tren ed sd nghien cffu edng nghe tao mau nhanh, gia edng cat bang tia laser.
ky thuat ghep noi, Vien May va dung cu cong nghiep da phat trien phffdng phap tao khuon nhanh trong khuon khd lua chpn thiet bj cd sin de cd the thffc hien phan thffc nghiem. Lam khuon nhanh tir ghep tam dffdc thffc hien trong nghien cull nay bdi each tiep can, thffc hien tuan tff tren to hdp thiet bj chff khdng phai tren 1 thiet bi td hdp. Ldi the ciia giai phap nay la giam gia thanh dau tff ban dau. Tuy nhien khd khan cua giai phap la qua trinh dien bien tren chuoi thiet bj nen nen khd giam sat cac tham so qua trinh.
Giai phap nay bao gom cac cong doan:
Thiet ke CAD-3D; Cat tam/ Idp; xep chong , gan ket; gia cong lai (neu can) nhff hinh 1.
Theo nguyen li tao khuon nhanh, hinh dang vat li cua khuon dffdc xay dffng tff dff lieu CAD-3D, thffc hien phan Idp ao va gia cong trong mdi trffdng CAD/CAM, trffc tiep tren kim loai tam bang may cat laser C02 CNC cua phong thi nghiem dac biet IMI. Oay la cong doan dang chu y do tinh tich hdp cua edng nghe. Tren thffc te, may CNC laser khdng cd tinh nSng phan va cat Idp ao nhff may tao mau nhanh nen day la phan viec dffdc thffc hien bdi phan mem "c3t Idp" off line -slicing IMIl xay duYig bdi
Thiet ki3D Cat tam tren may laser
Chi tiet ket Qua Thu khuon (tren may
Hinh I:Ppht3t trien lam Ichuon nhanh tam ghep
36 TU OpNG HdA N G A Y NAY •• {S6 1 +2«310)
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Begin File STL Tai tao mo hinh 3D
khong dong nhat
I
Cat lop mo hinh 3D
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Xac dinh cac duimg bien 2D khep kin tir cac mat cjl
DO li?u tap hpp duong bien 2D khep kin
S5p xep c4c l<!rp cat 2D tren di$n tich phoi tim Chuyen doi dii li?u thanh
ma nguon GNC
Chuong trinh gia cong
Hinh 2 :LUXJ do thuat toan cat idp deu ciia phan mem slicing IMIl
Cac tam cat cd the dffdc ghep bdi cac edng nghe khac nhau [10,11].
Trong nghien cffu nay, khuon Iffa chpn la khudn dap udn va vuot nen ghep ndi bang chot djnh vi va bu long, dai de la mot giai phap ddn gian, cd the cd tinh hieu qua cao. Trong trffdng hdp nay, cac tam cat dffdc xep chong theo thff tff Idp va dffdc ep sd bp bdi cac bu long thiet ke sin de khff"khoang khdng"
giffa cac Idp. Sau khi ep chat, cac bu long cua khudn dffdc ndi long de dffa chot djnh vj- lap trung gian vao vi tri thiet ke sin. Sau dd cac bu long dffdc xiet dan deu cho den khi xiet chat.
Viec xiet va ep chat nay dffdc thffc hien nhSm tdi thieu khoang khdng giffa cac tam, tao khdi dong nhat nhff cd the. Cac khudn nhanh (hinh 5), nhdm tac gia cua de tai. Lffu do thuat
toan cua phan mem (hinh 2) the hien hinh khoi 3D vat the dffdc tai tao, phan Idp va s3p xep hdp li len tam trffde khi dffdc chuyen thanh chffdng trinh NC gia edng. Chat Iffdng gia cong thep tam bang tia laser phu thudc vao cac tham sd edng nghe gia edng nen mot nghien CUXJ thffc nghiem tim md hinh toan hpc dp rpng mach c3t tren cd sd ham vat lieu, chieu day vat lieu, edng suat laser, dffdng kinh dau phun va ap khi thdi, bd sung vao cd sd dff lieu dieu khien edng suat laser-tdc dp c3t, mot ndi dung da dffdc nghien culj long ghep tff nhieu nSm nay d trung tam cac edng nghe d3c biet IMI de lam cd sd bii sal sd mach cSt cho kich thffdc hinh hpc gia edng theo nguyen li bu cua cac bp CNC thffdng mai . Nhff vay, sau khi chpn cac che dp edng nghe eSt laser, dp rpng mach c3t dffdc tff ddng tinh va link Veio gia tri (hinh 4), de bu tff ddng dffdng chay tia. Cac file dff lieu "c3t ldp"dang chffdng trinh NC dffdc truyen vao bd dieu khien CNC cua may cSt laser de thffc hien gia edng cac Idp thff tff ho3c tuy chpn, mpt Idp, nhieu Idp hoSc tat ca cac Idp theo yeu cau cua ngffdi thiet ke.
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a) Hinh khdi 3D Hinh}.
ket qua cua de tai la chay va coi khudn udn U, V 90o, coi khudn vudt tru, eon va mot khudn cdn tien lai de so sanh ket qua.
Cac khudn ghep dude dffa len may ep 25 tan de kiem nghiem thdng qua ep thff chi tiet (hinh 6).
Kiem tra cac chi tiet dap cho thay, cac kich thffdc hinh hpc va cac be mat chi tiet cd tiep xue vdi khudn (chay hoac edi) khdng cd vet sffdt, dam bao chat Iffdng gia edng ban thanh pham.
3. Chat Iffdng thffc nghiem cua khudn gia edng nhanh tff tam ghep Kiem tra cac kich thffdc tao be mat edng tac cua khudn: De khao sat chat Iffdng gia edng bang tia kic- Bv ffde gia edng cua "Idp"
chat che nhat. Do yeu cau lap rap trung gian tren chieu dai mdi ghep tffdn p tru thi tff d laser ddi vdi phffdng phap gia edng theo "dap Idp", tat ca cac thffdc hinh hpc quan trpng cua "Idp" anh hffdng dac biet tdi be m i t edng tac (the hien trong hinh 7) cua tat ca cac khudn dffdc do kiem, tuan tff theo true Z vdi thffdc cap sd cua Mitutoyo Model- CD-8"CSX vdi thang do: 0,01-200mm, dp phan dai :0.01mm. Trong bao cao nay neu vi du ddi vdi edi vudt tru. Tai mot Idp, hinh 4.8 thi: - a l , a2: kich thffdc long edi, tao nen
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(S6l+2/2010)<Tl/DONGHOANGAY NAY 37
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Hinh 5: cac khuon gia cong ap li/c theo nguyen li khuon nhanh ghep tam
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Hinh 6: Chi tiep gia cong tren may dap 25t
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Hinh 7: kich thudc hinh hoc cua 1 Idp - tam ghep coi vuot tru
dffdng kinh ngoai cua chi tiet vudt, dude thiet ke vdi kich thffdc danh nghia la 050 b2
- f l l , f l 2 , f l 4 , f24: dffdng kinh lo chot ( 0 8 ) va f l 5 : kich thffdc ndi suy khoang each gi&a 2 chot djnh vi (095);
cac kich thffdc nay quyet djnh den dp chinh xac cua khudn thdng qua djnh vj lap ghep tam. bl,b2: dffdng ki'nh ngoai cua tam ghep (0110), quyet djnh den kich thffdc lap ghep vao than coi cd sd.
Bieu do dao ddng kich thffdc hinh hpc cua eae Idp thupc edi udt try dffdc hien thj d hinh 8.
Khao sat f - kich thffdc lo chot 0 8 , la kich thffdc be nhat cua day kich thdong thdi yeu cau mien dung sai ddi Idn nen thiet ke chpn dung sai lap rap Js8/h7. Vdi dung sai nay, kich thffdc lo cat de lap chot cd dung sai ±0,011 [28]. Tff bang ket qua do cua coi vudt tru cd the nhan thay dp dao ddng Idn nhat cua cac kich thffdc f l l la: 18,014,08-1-; f l 2 la: 18,012,08-1- f l 4 la: 18,016,08-1— va f24 la:
14,018,08-1—, ket qua nay cho thay do dao dpng gia cong kich thffdc lo chot d cac tam vffdt qua yeu cau thiet ke du la khdng Idn. Neu ap vao mien dung sai he lo lap gheng gian dng dffdng vi dp chinh xac gia edng cap 10-rl2, la cac 120
4. Ket luan
Oe thffc hien viec do kiem kich thffdc hinh hpc chinh xac nhff cd the, 5 khuon dap ngudi hinh hpc ddn gian: khudn V, U, vudt tru, cdn va cdn nhanh tien lai da dffdc gia edng thffc nghiem nh§m minh hoa cho giai phap phap trien lam khuon nhanh tren cd sd tam ghep cua nhdm nghien cffu Vien IMI. Giai phap lam khudn nhanh theo phffdng phap nay c6 the cac bffdc nhff sau:
- Thiet ke khudn dang CAD-3D solid - Lffa chpn thiet bj cat 2D CNC, gia cong "Idp" vdi sff trd giup cua phan mem cat Idp
- Tuyen chpn va thffc hien phffdng phap ghep Idp, tao khudn vat li cd hinh dang hinh hpc tffa khudn lien khdi
- Gia edng tinh lai be mSt cong tic khi cd yeu cau ve dung sai kich thffdc khSt khe.
- Thff nghiem /sff dung khudn gia edng chi tiet
Cac khudn nay da dff(?c sff dung 6i dap hang nghin chi tiet. Qua thff nghifm ed the ket luan, khudn nhanh dang nay rat phu hdp cho gia cong ban thanh pham. M3c dij cdn cd nhuTig han chfi
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T A I L I E U T H A M K H A O [1] Collaboration of Warwick, Loughtioroug, De Montfort Univer- sities Innovatibve Manufacture of Rapid Die_Casting Tooling by Lami- nated for the Automotive Industry, Review Report (Radical) GR/M75068/01
[2] Walczyk D.F, A new Rapid Tooling Methode for Sheet Metal Forming Dies. Proceedings of the 4th International Conference for Rapid Prototyping p 275-289,1994, [3] T. Himmer, E. Stiles, A.
Techel, S. Nowotny, E. Beyer, Re- cent development in Metal Lami- nated Tooling by multiple laser Processing, Report 3/2005 at www.moldmaking technology,
[4] H Muhler, Experiencies using Rapid Prototyping Techniques to manufacture Sheet Metal Form- ing Tools, Report at ISATA, Dublin Ireland Sep 25-27, 2000
[5] Metal laminated tooling, www. iws. fhg. de/~metalo/
[6] M Philpott, RA. Green, An Error Compensation Strategy for replication by rapid prototyping, Jourbnai of Engineering for Indus- try, Aus 1995 Volum 117
[7] Z. Lechniak, A. Werner, C.
Skalski, K.Kedzior, Methodology of off-line software compensation for errors in the machining process on the CNC machine tool, Jornal of Ma- terials Processing Technology 76(1998) pag 42-48
[8] Drian Apelian, Bruce Board- man, Introduction to Furnance Brazing, Air Products and Chemicals Inc2001
[9] S.H. Yoon, S.J. Na, Rapid Laminated Tooling by a Brazing and Soldering Processing, Society of Manufacturing Engineer (SME) , Sept 2003
Hinh 9: Do nhap nho cua khuon dap V
nhat dinh nhff can thffc hien thi nghiem vdi Id Idn hdn, thff nghiem them cac
\ phffdng phap ghep tam khac va dac biet [ can sff dung nhuTig phffdng tien do kiem ' tdi tan hdn de ed the ed nhffng ket qua mang tinh djnh Iffdng. Nhffng nhuTig ket qua trong nghien euli nay phan nao da [ minh chffng va md ra mot hffdng lam I khudn nhanh day trien vpng, nhat la ddi
vdi cac loai khudn sieu trffdng, sieu trpng, hinh hpc long khudn phffc tap, can dap ffng nhanh nhu cau thay doi cua khach hang ma tinh kinh te cua khudn vTnh cff\j khdng cho phep. Dae biet, viec phat trien phan mem cat Idp (slicing- I M I l ) thffc hien gia edng tam cd y nghia rat quan trpng trong viec xay dffng giai phap edng nghe, thiet ke che tao khudn nhanh tff
tam ghep. Phan mem nay cdn cd y nghia trong viec xay dffng phffdng phap luan de phat trien giai phap RP mdi (thiet bi, edng nghe) do xu hffdng phat trien ciia thiet bi che tao RP la gia edng tff ddng vdi sff ho trd cua phan mem cat Idp, ed nhffng nguyen tac va edng nSng ma phan mem Sliee-IMIl dang thffc hien.
(36 1+2J2O10) < TV O^NG H<JA N G A Y NAY (39
