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^- -^ ^ M ^' \ ^ J NGHIEN c t r u ANH HUOWG CtJA CAC THONG SO CONG N G H ? ^ ^ ^ ^ ^ CHINH XAC GIA CONG TREN MAY PHAY CNC THEO PHU'ONG PHAP THIET KE THU'C NGHIEM RESEARCH THE EFFECTS OF TECHNOLOGICAL PARAMETERS TO ACCURACY IN PROCESSING THE CNC MILLING MACHINE BV DESIGN OF EXPERIMENTS METHOD Nguyen Trgng Hung', Nguyen V i n Phii^ Truong Dgi hgc Supham Ky thugt Hung Yin Trudng Cao ddng nghe Dong Nai Tom tit: Bdi bdo ndy trinh bdy phuong phdp nghien euu dnh hudng ciia cdc yiu td cdng nghe din dp chinh xde gia eong tren mdy phay CNC theo phuong phdp thief ke thuc nghiem (DOE), ldm gidm so lugng thue nghiim, tgo sdn phdm chdt lugng eao voi ehi phi thdp cho cdc nhd sdn xudt Kit qud nghien euu cho quy lugt phdn bd kich thuoc chi tiet gia cong vd quan h? giira sai lieh kich thuoc gia cong vai cdc thong so cong nghe gom van toe cat vd lugng chgy dao vd xdc dmh dugc thong sd cong nghe tdi uu cue bo (trong pham vi khdo sdt) co sai lech kieh thude nhd nhdt gia edng tren mdy phay CNC Do ndng cao dg chinh xdc vd nang sudt gia cong Tir khoa: Anh hudng yeu to edng nghi Do ehinh xac gia cdng, Thiet ke thue nghiem Van toe cat, Lugng chgy dao Mdy phay CNC Mddiiu Viec nghien cuu quy luat phan bo kich thudc va anh hudng eac thong s6 eong nghe dgn chinh xac gia cong tren may phay CNC, theo phuang phap thiet ke thuc nghiem (DOE) sir dung ma tran true giao cap I, de xay dung m6i quan he giiia sai lech kich thude gia cong vdi eae thong so cong nghe gom van toe cat va lugng chay dao, dam bao dp chinh xac gia eong tren may phay CNC Do do, nang cao dp chinh xac va nang suat gia cong Day la van de hien dang duac dng dung nghien ciru d nude ngoai va hien chua co cong trinh nghien eiiu mpt each day du ve van d l ITnh vuc che tao may duge, cdn true tung la tan suat ciia cac kich thudc xuat hien moi mpt khoang Qua nghien cihi thay rang, kieh thude phSn b6 ciia ca loat chi tilt eat thu tap trung d khoang giua, so chi tiet cit thir mpt lan dieu ehinh may cang Idn, thi dudng eong cang co dang tiem can d i n dudng cong phan bo chuan Gauss (hinh la, b) Tan suat ^R' Qua nghien euu nit nhiing van dg co tinh quy luat, kiem chiing tren thue te Tir do, xay dung thu vien che eong nghe gia cong cho qua trinh san xuat tuang tu, giup cho ngudi thao tae dl dang ling dung, nham toi uu cac thong so cong nghe cong nghe pham vi khao sat Cff sd phuwng phap nghien cmi dd chinh xac gia cong 2.1 Phu-omg phap xac suit thdng ke |4| Gia cong loat thii tir 50 ^ 100 chi tilt mpt lan dieu chinh may Do kich thudc thuc cua timg ehi tiet ca loat, xac dinh gia tri gidi ban ldn nhat, nho nhat Chia khoang gidi han tir ldn nhat den nho nhat mpt s6 khoang ( > 6) Xac dinh so lugng chi tiet cd kieh thudc n i m moi khoang va xay dung dudng eong phan bd kich thudc thuc nghiem, ed true hoanh la kieh thudc dat 10 Hinh la Dirang cong phdn bo thuc Hinh lb Dudng cong phdn bd kich thude chudn Gauss Khoa hoc & Cong nghe - So 02/2014 Phuang trinh dudng cong phan bo chuan Gauss CO dang: {JV27t Trong do: e - Co so eua logarit tu nhien - Sai lech binh phuang trung binh N Vdi: X | - d j - d ^ X = d, - d" Nhu vay, muon biet gid tri ciia de viet phuang trinh dudng cong phan bo, tien hanh gia eong thli va thong ke cac tri so dj, d^, d^, , d^^ = 24 (z) Y = bp + b|X^+ bjX, + b,jX|Xj Trong do: bp - he so hoi qui b - he so tuyen tinh b^ - he so mang tae cap - Thuc hien N = 2'' thi nghiem, roi tinh toan eac he so hoi quy b bang phuang phap binh phuang nho nhat - Kiem dinh su co y nghTa ciia cae he so hoi quy bj theo tieu chuan Student, bang each thuc hien cac thi nghiem tai tam quy hoach hoac su dung eac thi nghiem song song, lap lai Loai bo cae he so b khong eo nghTa, tinh toan lai cac b va kiem dinh Iai cho tdi chi cac b co nghia - Kiem dinh su co nghTa cua phuang trinh hoi quy vdi ehuan Fisher 2.2.2 Thirc nghiem yeu to to^n phan N = 2" - Phuong phap to chiic thi nghiem true nghiem true giao cap I: + So thi nghiem can thue hien: N = 2'' + Miic ca ban (tam phuang an): n _ zr'+zr'" Gia tn cua ham (z) va ( z ) duge tinh sin bang ham Laplace [4] Tir bang thay ring, z = — — , tiic la x — o , thi ham * ( z ) = 0,9973, k p t h u a t c o t h l coi bang Vi vay, CO the ndi rang xac suat xuat hien chi tilt c6 sai lech ki'ch thude so vdi kich thudc trung binh (d^) khoang -3 -^ +3 0(khoang a) b i n g l ("hoac 100%) Trong dd: 2j — Z, + /I, _ Miic tren (miic cao); Z™" — 7J]~ A- Miic dudi (mue thap); = 111 til - Khoang bien thien theo true Z 2.2 Phu-ong phap quy hoach thirc nghifm [2] Phuang trinh hdi quy (mo hinh toan hgc) n h ^ dugc bing phuong phap quy hoach thuc nghiem co the diing de xac dinh cac thong so dau vao toi uu muon dat thong so dau cue trj (Idn nhit hoae nhd nhat) 2.2.1 Phircmg phap quy hoach trvc giao cap I - Biin khong thii nguyen x : Ma hoa dugc thuc hien nhd viee chgn tam Zj ciia mien nghien cdu lam goc he true tga _ z r ' - Z? j = l,2, ,k - Mien bien thi^n: " Z r " < Zj < Z " " - Tam quy ho^ch: z;-o.5(z,'^+z,"") - Phuang phap phan tich h6i quy: Cac phuong phap phan tieh hoi quy gom co Phuong phdp binh phuong nho nhdt; Hoi guy tuyin tinh mpt biin: Hdt quyparabol; Hoi guy hdm sd mii vd Hoi quy nhieu biin Chii y rdng, su- dung ham nhiiu bien tong qudt va cho kit qua vdi ^ chinh xdc cao Hon Khi CO hai thong sd nghien ciiu, ham hoi quy nhilu biSn co dang nhu sau: /ll _ Zj - z? - Xay dung ma tran thuc nghiem' + s thi nghiem xae djnh theo cong thirc N = 2'', cot Xp luon bang + Lap cho tirag yeu to anh hudng va lan lugt tii X| den x^; + Dua cac thi nghiem d tam vao ma trSn 2.2.3 Y nghia cua he %h b phinrag trinh hoi qui Tinh y nghTa ciia cac he so b dugc kiem dinh theo chuin Student (t) xac dinh nhu sau: Khoa hoc & Cong nghe - So 02/2014 11 Sd yiu t6 anh hudng din dp chinh xac kich thudc gdm yiu tl la van tde eat va ehieu sau cat: k=2 S6 thuc nghidm t^i tam: Trong do: N„ = b - He s6 thli j phuang trinh h6i qui Suy ra, tong sd thuc nghiem: S^ - Sai lech binh phuang trung binh ciia he N i = N , + N„=4H-3-7 so/ - Muc CO ban: O day chgn' XSy dyng bai toan nghien cihi \h thirc nghiSm V^,^ = 61 m/ph; S^,„ = 0,15 mm/v6ng; t_^,^ 3.L B^i toan nghiSn cihi 1/ Nghien ciiu quy luat phan b6 kich thude 0,2 mm chi tilt eiia loat gia cong thu tren may phay CA^C V^^ = 81 m/ph; S ^ = 0,45 mm/vdng; t^^ lira chgn chi dp cdng nghe van toe cat, lugng = 1,0 mm chay dao va chieu sau cat t Suyra:Vf = 71m/ph; S? ^ 0.3 mm/vdng; 2/ Nghien euu anh hudng eua viec thay doi t° = 0.6 mm van t6c cit va lugng chay dao den dp ehinh xac kich - Khoang bien thien: thudc chi tilt gia cong tren may phay CNC Al ^ 10 m/ph ; A^i = 0.15 mra/vong; A\ = 0.4 mm 3.2 Lira chon gia tri cic thdng so cong nghe - Cac biin khdng thit nguyen: Qua nghien cim vdi muc dich nang cao cong + Bien khong thir nguyen van toe: chinh xac gia cong tren may phay CA'C, cac thong ^v„^j;xr""=-l;x:- = so eong nghe dugc lua chgn va quy doi nhu sau [5], [6]; + Biln khdng thu nguyen lugng chay dao: S t V Thong so 7.]-'=V' x f " ' ' - l ; x f = tj = (m/min) (mm/vong) (mm) Mire cao; 81 0.45 1,0 Muc trung binh: 71 0.3 0,6 cdng nghe b Ma tran thuc nghidm Tu phuang trinh hoi quy lua ehgn: Y = b(, + b|X,+ bjXj + b,2X,Xj Trong do: bg - he so hoi qui 0.15 0.2 61 Miic thap: b - he sd tuyen tinh b - he so tuong tac cap 3.3 Thuc nghiem Suy ra, ma trSn thi nghiem vdi k = va - Vat lieu phoi: thep cacbon C45 thuc nghiem tai tam phuang an vdi cac thdng so dau - Kich thudc ehi tiet: h = 19* ' '' mm vao (V, S) va cac bien ma hda la X^, X, v^ X^ dugc - Sir dung may phay true CA'C - DMC635V chi dan tren bang Hang DECKEL MAHO Cgng Hda Lien Bang Trong do: Dire chi tao, he dieu hanh FANUC32i Xg- bien ao dugc dua them vao ma tran; X^ - bien ma hoa iing vdi van toe cat; 3.3.1 Thilt ke thuc nghiem nghiSn ciru quy luat Xj - bien ma hoa iing vdi lugng chay dao phan bo kich thirdc Bang Trong qua trinh thuc nghiem se khong thay doi gia tri cac thdng so cdng nghe doi vdi loat eac TT X X, X, x,.x V S mau gia cong - Van tde cit: V - 71.0 m/phiit; -1 -1 61 0.15 - Lugng chay dao' S = 0.3 mm/v; -1 -1 0.15 81 - Chieu sau cat: t = 0.2 mm 3.3.2 Thiet kl thyc nghidm nghiSn cfru anh hudng ciia thSog so cong nghe den dg chinh xac gia cdng a Phieang phdp td churc thuc nghiem true giao cap I - So thuc nghiem: N-2'^ 12 Khoa hoc & Cong ngh? - So 02/2014 -1 -1 61 0.45 1 SI 0.45 0 71 0.3 0 7/ 03 0 71 0.3 Chu y rdng chiiu sdu edt lua chpn d ehi dp phay tinh t^ 0.2 mm Neu chgn so lugng gia tri eua khoang chia: _ 45 = 9tim 3.3.3 Lira chgn phuang phap, dyng cu - Phuang phap do: kich thude theo phuang phap tuyet d6i va true tilp - Dung cu do: Pamne chi thj s6, co bg phan ghi ket qua ciia Hang Mitutoyo (Nhat ban); Pham vi do: ^ 25 mm; Do chinh xae 0,001 mm Tu bang va gia tri khoang chia lap bang phan bd thue nghiem ciia x, d6ng thdi tinh tin sd thuc nghiem f {sd lugng chi tiet) nim cac khoang chia Qua tinh toan va bing phin m i m Microsoft Excel ta ve duge dudng cong phan bo ly thuyet cua quy luat phan b l chuin ciia mlu gia cong (hinh 3) Quy luat phan bo chuan l
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