Giáo Trình Máy CNC Và Công Nghệ Gia Công Trên Máy CNC

5/24/2018 Gio Trnh My CNC V Cng Ngh Gia Cng Trn My CNC

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Gio trnh

My CNC v cng

ngh gia cng trn

my CNC


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May CNC & Cong Nghe Gia Cong Tren May CNC

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CHNG 1

T ONG HOA QUA TRNH SAN XUAT S RA I CUA MAYCNC-----------------

Trong na thap ky qua, the gii a chng kien s ra i va phat trien nh vu bao cua KTK tong. Va nhanh chong KTK t ong a c ng dung vao cong nghe che tao san pham ckh. S phat trien cua t ong hoa QTSX co the c tom lc nh sau.

1.1/ NC (Numerical Control)1.1.1/ Lch s ra i cua NC.

Cung nh cac ky thuat tien tien khac, NC ra i vao au thap nien 50 tai phong th nghiem cuahoc vien Massachusetts. Khi mi ra i, may NC ch co the cat c nhng ng thang chnhxac va hieu qua. ieu nay gay ra rat nhieu kho khan v may phai thc hien vo so cac ngthang ngang, doc e gia cong cac bien dang cong (hnh 1.1)

Hnh 1.1

Van e nay dan en s ra i cua APT (Automatically Programme Tools). ay la loai ngon nglap trnh au tien cho NC, dung cac cau lenh tieng Anh e nh ngha ng di chuyen hnh hoc,dung cu va cac ch th can thiet khac. ay cung la tien e c ban cho s phat trien cua NC. Banau chng trnh NC c ma hoa tren cac bang uc lo, sau o dung cac bang t. Sau khi maytnh ra i, cac bang uc lo, bang t c thay the bi thiet b x ly d lieu cua may tnh.

1.1.2/ May NC la g

May NC bao gom 2 bo phan chnh.a) Bo ieu khien may (Machine Control Unit : MCU)La bo phan thc hien cac chc nang sau:- oc va giai ma chng trnh- a ra cac lenh ieu khien- Nhan cac tn hieu phan hoi va x ly. MCU bao gom 2 bo phan sau: DPU (Data processing Unit): Bo x ly d lieu CLU (Control Loop Unit) : Bo thc hien ieu khienDPU oc cac d lieu t chng trnh tren bang uc lo, a t,va giai ma cac tn hieu nay thanhcac d lieu so. Sau o gi tn hieu en CLU.

Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com


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CLU nhan cac d lieu c giai ma t DPU, a ra cac lenh ieu khien may, nhan cac tn hieuphan hoi so sanh va x ly cho en khi at o chnh xac yeu cau. DPU sau o se oc khoi lenhtiep theo.

b) May cong cu (Machine Tool):Tng t nh cac may cong cu thong thng, nhng cac chuyen ong cua cac truc c thchien bi ong c servo hoac ong c bc thong qua truyen ong vt me ai oc bi (se trnh bay chng sau).

Tren hnh 1.2 la s o cac thanh phan cau tao cua may NC

Hnh 1.2. thanh phan cua may NC

May NC a khac phuc c nhng han che ma cac may cong cu truyen thong khong thc hienc. Vi may NC, o chnh xac gia cong cao hn, tiet kiem dung cu hn, de t ong hoa hn.S ra i cua NC cung a a en s ra i cua hang loat cac phng phap gia cong hien ai,tien tien khac nh:EDMLaser CuttingElectron Beam welding

Water jet

So xungv tr cua truc

Tan so xung: toc o cac truc



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1.2/. DNC (Direct NC):Vao gia thap nien 60, vi s ra i cua may tnh, ngi ta a ngh en viec thay oi viec mahoa d lieu tren bang uc lo, bang t bang may tnh nham giam bt cac yeu cau ve phan cng,lap trnh n gian hn, nhanh chong va linh hoat hn.Vao thi iem nay, may tnh rat at tien nen ngi ta dung mot may chu (host) e ieu khienchung nhieu may NC qua mang ket noi. He thong tren goi la DNC (Hnh1.3)

Hnh 1.3. He thong DNC

1.3/. CNC (Computer Numerical Control)

Vao cuoi thap nien 60, s ra i cua cong nghe vi x ly a a en s xuat hien cua PLC,Microcomputer. Cac thiet b nay ngay sau khi ra i a c ng dung tren cac may NC, va thehe may CNC a ra i. Vi CNC, moi may NC c phuc vu bi 1 PLC hoac Computer rieng.ieu nay cho phep chng trnh co the nhap va lu tr rieng tren moi may CNC. Nhng lai xuat

hien cac van e mi o la quan ly d lieu (gia cac may khong co s lien he chat che vi nhau).Cac thnh phn c bn ca may CNC bao gom: Hnh 1.41/. Chng trnh gia cong (Part program )2/. Thiet b oc chng trnh (Program input device )3/. Machine control unit (MCU)4/. He thong truyen ong (Drive system )5/. May cong cu (Machine tool)6/. He thong phan hoi (Feedback system)



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Hnh 1.4. Cau truc cua may CNC

1.4/ DNC II (Distributed NC)

e viec quan ly d lieu gia cac CNC tot hn, he thong DNCII a c a vao ng dung trongsan xuat, la s ket hp gia DNC va CNC. He thong DNC II bao gom cac may tnh chu (Host

Computer) va cac may tnh cuc bo (Local computer) ket noi vi nhau. No cho phep cac chngtrnh gia cong c lu tren may chu nen viec quan ly tot hn. Cac chng trnh nay co the cdownload xuong cac local computer hoac PLC. Va ta cung co nhap chng trnh va dao dientrc tiep t cac may cuc bo (local). Va neu may chu b ngng th cac may CNC van co the hoatong bnh thng. ay la u iem c ban cua DNC II so vi DNC.



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Hnh 1.5. He thong DNCII

1.5. He thong san xuat linh hoat (FMS: Flexible Manufacturing System)

Vao gia thap nien 60, cong ty Molins Ltd (anh) a phat trien he thong 24, la tien than cua hethong FMS. Tuy nhien do han che ve ky thuat nen he thong san xuat linh hoat van ch dng lai mc o ly thuyet, y tng trong suot nhng nam 60s, 70s. vao cuoi thap nien 1970, au thapnien 1980s, vi s phat trien manh cua cong nghe ieu khien phc tap nh may tnh, he thongFMS a c ng dung thanh cong. He thong FMS dc ng dung chu yeu US trong cac lnhvc che tao o to, xe c gii, may bayHe thong FMS ien hnh bao gom:

Thiet b x ly: May cong cu, he thong lap rap, Robot. Thiet b x ly phoi: Robot, bang tai, He thong van chuyen t ong (AGV : Automated

guided vehicles) he thong lu kho t ong (AS:Automated storage) va he thong truy xuat(RS: Retrieval System)



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He thong trao oi thong tin. He thong ieu khien bang may tnh (Computer controlled system) Con ngi ( Human operator). He thong thay dao t ong (automated tool changers).

FMS tao nen mot bc tien mi hng en viec tch hp hoan toan qua trnh san xut, da trencac he thong, quan iem t ong hoa sau:

CNC DNC II He thong x ly phoi lieu t ong (Automated material handling system.) Cong nghe nhom (Group Technology) Mot so mo hnh FMS ien hnh

Hnh 1.6. Single machine cell



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Hnh 1.7. Multiple workstation Cell

Hnh.8. FMS vi he thong lu, xuat kho t ong. AS/RS



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Hnh 1.9. FMS hang san xuatVought Aircraft

1.6/ He thong san xuat tch hp (CIM: Computer Intergated Manufacturing/flexibledesign and manufacturing)- Y tng ve he thong sx tch hp c Josheph Harington e cap en vao nam 1974, nhngphai qua hang chuc nam en au thap nien 1990s, he thong nay mi c ng dung thanh cong My. CIM la he thong tch hp toan bo cac thanh phan cua qua trnh sx, c x ly va ieukhien bi may tnh. T viec phan tch th trng,thiet ke, chuan b phoi lieu, chuan b va to chc

sx, kiem tra chat lng san phm cho en ca viec phan phoi ra th trng. Vi s ra i cuacong nghe CIM, lch s phat trien cua san xuat xa hoi a trai qua cac giai oan sau:- San xuat thu cong- San xuat c kh hoa, chuyen mon hoa- T ong hoa san xuat.- Tch hp san xuat

- Cac thanh phan c ban cua he thong CIM bao gom (Hnh 1.10). CAD/CAM (Computer-aided design/Computer-aided manufacturing) CAPP (Computer-aided process planning) ERP (Enterprise resource planning) CNC machine tools



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DNC FMS ASRS( automated storage and retrieval systems ) AGV ( automated guided vehicles ) Robotics Automated conveyance systems Computerized scheduling and production control CAQ (Computer-aided quality assurance) A business system integrated by a common database. Lean Manufacturing

Hnh 1.10 Cac thanh phan cua he thong CIM.

Vi viec tch hp qua trnh san xuat, nang xuat tang len nhieu lan, giam chi ph lao ong, giamthi gian thiet ke va phat trien san pham, chat lng thiet ke cao hn, tnh linh hoat cua hethong rat cao giup ap ng nhanh nhu cau cua th trng, tang li the canh tranh. Trong hethong CIM, can co s chia se thong tin gia cac bo phan e tang tnh linh hoat va hoat ong cuacac khau hieu qua hn.



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Chng 2: MAY IEU KHIEN CHNG TRNH SO

2.1. Khai Niem C Ban2.1.1/ ieu khienLa s thay oi cua cac ai lng au ra theo quy luat nhat nh nao o cua cac ai lng auvao.

2.1.2/ ieu khien so NC ( Numeric Control )La he thong cac hoat ong c ieu khien trc tiep bi d lieu so c ma hoa bangchng trnh. Chng trnh gom cac ch th c ma hoa di dang so, k t ch, va cac k tac biet khac. Cac ch th nay bao gom:

Ch th ieu khien: c chuyen thanh 2 dang:Tn hieu xung ien (Pulse):ieu khien toc o, so vong quay cua ong c truyenong.Tn hieu ong/ngat (ON/OFF) :cung cap chat boi trn va lam nguoi, chon va thaydao, dng may, kep nha phoi

Thong tin hnh hoc ( Geometrical Information): La he thong thong tin ieu khiencac chuyen ong tng oi gia dao cu va chi tiet, con goi la thong tin ve ngdch chuyen.

Thong tin cong nghe ( Technological Information ): La he thong thong tin cho phepmay thc hien gia cong vi nhng gia tr cong nghe yeu cau. Vd: chuan hoa goc toao, chieu sau cat, toc o chay dao, so vong quay truc chnh, chieu quay truc chnh,ong hay tat dung dch trn nguoi...

2.1.3/ ieu khien so bang may tnh (CNC)nh ngha:CNC la he thong NC s dung may tnh thiet lap trc tiep tren he ieu khienmay.ac iem: c ieu khien bi cac ch th lu tr tren bo nh may tnh e thc hien mot phan

hay toan bo cac chc nang ieu khien so.

c phat trien da tren nhng thanh tu cua cong nghe vi ien t, vi x l. Cac he ieu khien CNC co kha nang thc hien cac chc nang ieu khien bi phan

mem -> n gian cac mach ieu khien, giam gia thanh , tang o tin cay.

*** Hau het cac he ieu khien so the he mi eu dang CNC.2.1.4/ May cong cu ieu khien theo chng trnh so (CNC Machine)La the he may cong cu (machine tool) c ieu khien bi bo ieu khien CNC



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2.2. Cau truc he thong may CNC:He thong may CNC gom 6 phan chnh: Hnh 2.1

- Chng trnh gia cong(part program) - Thiet b oc chng trnh ( program input device)- Bo ieu khien may (MCU) - He thong truyen ong ( drive system)- May cong cu (machine tool) - He thong phan hoi ( feedback system)

Hnh 2.1. Cau truc cua may CNCLu y: oi vi may gia cong CNC, chng trnh gia cong, thiet b oc chng trnh va bo x lyd lieu (DPU) eu c thc hien bi may tnh.

2.3 . Kha nang cua may CNCVe c ban, may gia cong CNC co the thc hien c cac cong viec sau:

+ Nhap d lieu+ Bien tap chng trnh, lap trnh+ Lu tr chng trnh+ Kiem tra chng trnh+ Chan oan loi+ Hien th chng trnh va mo phong bang o hoa qua trnh gia cong+ Tien ch giao tiep+ Quan l d lieu+ Cai at he toa o va he n v

+ Co kha nang tnh toan, x ly so lieu



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+ Bu tr ng knh va chieu dai dao+ Noi suy hnh hoc

2.4. u va nhc iem cua CNC u iem cua CNC+ o chnh xac va o chnh xac lap lai cao+ ap ng nhanh nhu cau th trng, gia cong nhieu be mat phc tap+ Nang cao nang suat ac biet la trong san xuat n chiec cac chi tiet phc tap+ Giam gia thanh ieu hanh gian tiep+ Ha gia thanh san xuat+ Thuan li cho viec t ong hoa qua trnh san xuat

Nhc iem cua CNC.+ Chi ph au t ban au cao.+ Chi ph lap trnh va may tnh kem theo.+ Chi ph bao tr cao va can phai co th bao tr chuyen nghiep.

2.5. Cac loai may CNCNgay nay, nhieu loai may CNC a c ngien cu va ng dung rong rai trong che tao c khnh:

- May phay CNC- May tien CNC- May gia cong tia la ien CNC dung ien cc nhung- May gia cong tia la ien CNC dung day cat- May khoan CNC- May mai CNC- May gia cong dung tia laser CNC- May gia cong tia nc CNC- May han CNC- May o toa o CNC (CMM: Coordinate Measuring Machine)



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Hnh 2.2. May Phay CNC ng (CNC Vertical Milling Machine)

Hnh 2.3. Trung tam phay ng CNC (CNC Vertical milling center )



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Hnh 2.4. Trung tam phay CNC ngang (CNC Horizontal machining center )

Hnh 2.5: May khoan ngang CNC (horizontal Drilling CNC)



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Hnh 2.6. May tien CNC

Hnh 2.7. May tien CNC hai au dao (CNC Dual turret turning center )



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Hnh 2.9. May o toa o CNC ( CNC Coordinate Measuring machine)

Hnh 2.10. May gia cong tia la ien EDM Wire Cut.



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2.6. Mot so bo phan c ban cua may CNC

2.6.1/ He thong ieu khien truyen ong CNC (CNC drive systems)

He thong ieu khien CNC bao gom mach ieu khien toc o (velocity loop) trong he thongong c truyen ong va mach ieu khien v tr(position loop control) ben ngoai he thong ongc truyen ong.He thong ieu khien CNC co the la he thong ieu khien h (open loop) hoac hethong ieu khien kn (closed loop). S khac nhau c ban la he thong ieu khien kn co phan hoinham am bao o chnh xac yeu cau.

a. He ieu khien h (Open Loop System) hnh 2.11.

He thong ieu khien h khong co mach phan hoi, bo ieu khien may xem nh s di chuyen banmay ung nh mong muon. He ieu khien h rat nhay cam vi s thay oi cua tai trong. Cac sai

so v tr va toc o co the xay ra khi cat vi lc cat ln. Tuy nhien he ieu khien h co u iem lan gian, re tien. Do vay, he ieu khien h ch nen dung trong di chuyen iem-> iem (PTP)hoac trong cac may cong suat cat nho.

Hnh 2.11. He ieu khien h (Open loop System)



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b. He ieu khien kn (Closed Loop System)

Vi he ieu khien kn, mach phan hoi c s dung e theo doi ap ng thc cua ai lng ieu

khien va a ra tn hieu sa oi khi co s sai lech gia gia tr mong muon va ga tr thc. Hethong phan hoi co the la he tng t (analog) hoac so (digital).

Analog systems: o s bien oi cua tn hieu ieu khien (v tr, van toc) di dang tn hieu hieuien the. ien hnh la dung may phat toc (Tachometers) e o van toc va resolvers e o vtr.

Hnh.2.12. Mach ieu khien kn tuan t (Analog type closed loop CNC drive system)

Digital feedback systems: Dung bo xac nh v tr so (digital position transducers ) trong machphan hoi. Bo ma hoa (Encoders) c s dung pho bien nhat. Con mach phan hoi toc o vangiong nh he phan hoi tng t. Hnh 2.13

Hnh 2.13. Mach ieu khien CNC kn so (Digital type closed loop CNC drive system)



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Ngay nay a so he ieu khien may CNC eu la he kn, S o ieu khien may CNC kn tongquat c mo ta nh hnh 2.14.

Hnh 2.14 . S o ieu khien CNC

2.6.2/ Truyen ong vt me ai oc bi (recirculating Ball Screw).

Trong may CNC, he thong truyen ong c s dung la vitme ai oc bi (hnh2.15). e thay rou nhc iem cua he thong vitme ai oc bi so vi cac he thong truyen ong khac ta xem bang2.1

Tn hieu phan hoi toc

Tn hieuphan hoiv tr

Cnd o, hieu ien thee ieu chnh toco

Tn hieu ieuchnh v tr

He thong ieukhien truc

ai oc biVt me bi ong ctruyen ong

May phat toc



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Hnh 2.15 . Truyen ong vtme ai oc bi

Bang 2.1 : u iem cua truyen ong vt me ai oc bi.Vt meai oc bi

Vt methng

Thuy lc Xch, ai Brang &thanhrang

Cam Kh nen

Ga thanh re X X X X XKha nang cong suatnho

X X X X

Chi ph bao tr thap Xo chnh xac cao X Xo tinh cay cao XHieu qua cao XKha nang truyen tailn

X X X

Ket cau gon X X X



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2.6.3/ ong c bc (Stepper Motor)

Hnh 2.16 mo ta s o nguyen ly dung ong c bc cung cap ieu khien so khong phan hoi ve

v tr cua ban may khi gia cong tren may CNC. Bo ieu khien nhan tn hieu ve chieu quay vatnh hieu xung ien e ieu khien goc quay cua ong c. ng vi moi tnh hieu xung ien, boieu khien se a ra tnh hieu cng o hoac hieu ien the e lam cho ong c quay mot gocnhat nh nao o (one step). Truc vt me ai oc bi se bien chuyen ong quay thanh chuyen ongtnh tien cua cac truc.

Hnh 2.16. Dung ong c bc e truyen ong trong may CNC

Ve c ban ong c bc c chia lam 3 loai sau: ong c bc t tr thay oi (Variable-reluctance), ong c bc nam cham vnh cu (Permanent-magnet ) va ong c bc ket hp(hybrid stepper motor).

(a)C bc t tr thay oi (b) C bc nam cham vnh cu (c) C bc hybridHnh 2.17



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ong c bc t tr thay oi ra i sm nhat, tuy nhien ngay nay khong c s dung rong raiv o phan giai va cong suat khong cao. e nang cao cong xuat ta co the dung ong c bcnam cham vnh cu. Tuy vay, loai ong c nay o phan giai cung khong cao (48-24 bc/vong).ong c bc c dung rong rai nhat trong cong nghiep hien nay la Hybrid stepping motor.ong c bc hybrid co Roto t tr thay oi vi nam cham vnh cu gan trong cac ranh t cuano. T hybrid muon ch en s ket hp cua 2 nguon t trng: tr trng t cac cuon day Statova t trng cua nam cham vnh cu. Hybrid Stepping Motor thng c dung khi yeu cau cacbc quay goc nho. ong c bc vi bc goc 1.8 o (200 bc/vong) la ong c tieu chuanc dung nhieu nhat trong cong nghiep t ong hoa.

00360 360; 200 / ; 1.8 /

200N step revolution step = = = =

ieu khien ong c bc co the dung ieu khien ay bc (full step) hoac khong ay bc

(micro step).a. ieu khien ay bc.Bang viec ieu khien cng o dong ien cung cap lan lt cho tng cuon day tren Stato cuaong c bc ta se co c cac v tr chnh xac tng ng cua Roto (nam cham). Toc o quaycua ong c bc phu thuoc vao tan so xung ien cung cap cho cac cuon day. Trong trnghp nay, o phan giai v tr cua truc vt dan ong c tnh nh sau.

N

lu = Vi: l(lead): bc ren (mm/vong hoac inch/vong)

b. ieu khien khong ay bc(vi bc).Bang viec ieu khien cung cap cng o dong ien ong thi cho cac cuon day stato ta cothe nh v tr cua Roto cac v tr trung gian giua cac cuon day tng ng, phng phapieu khien ong c bc theo cach nay c goi la ieu khien vi bc. ieu khien vi bcthng c s dung khi yeu cau o phan giai cao hn, do vay o chnh xac cao hn. Tuynhien viec ieu khien phc tap hn. Cac vi bc thng c s dung la 1/10, 1/16, 1/32,1/125. Trong trng hp ieu khien vi bc o phan giai c tnh nh sau.

m

lu

.= ; m: so vi bc trong mot ay bc

Lu y: ay ch neu len nhng khai niem chung nhat ve ong c bc, viec nghiencu ky cau cao, cach ieu khien cac loai ong c nay noi chung kha phc tap va sec hoc trong cac mon hoc khac.

Mot so u iem cua ong c bc la.

Gia thanh re (Low cost ) Co the ieu khien mach h (Can work in an open loop , no feedback required) Duy tr mo men rat tot (khong can thang, bien toc) Mo men xoan cao toc o thap Chi ph bao dng thap (khong co choi quet) (Low maintenance , brushless) nh v chnh xac Khong phai ieu chnh cac thong so ieu khien



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Nhc iem.ong c lam viec khong eu, ac biet la toc o thap (ieu khien ay bc)Tieu thu dong dien khong phu thuoc vao taikch c han chelam viec viec onMo men giam theo toc okhong co phan hoi nen co the xay ra cac sai so.

2.6.4/ ong c Servo.S khac nhau c ban nhat cua ong c servo so vi ong c bc la ong c servo co mach ieukhien kn (close loop control).Nh vay trong ong c servo can phai co he thong phan hoi enhan biet cac thong so ve v tr, toc o mong muon. Co nhieu phng phap ieu khien vong kn

trong o phng phap dung bo ieu khien PID la c s dung rong rai nhat.u iem c ban cua ong c servo so vi ong c bc la. Mo men tren truc eu hn (High intermittent torque ) Toc o cao hn (High speeds ) Mach ieu khien toc o chnh xac va eu hn (Work well for velocity control) Co nhieu kch c hn (Available in all sizes ) Lam viec em hn (Quiet) o chnh xac cao hn

Nhc iem c ban cua ong c servo so vi ong c bc la.

at tien hnKhong lam viec tot che o mach ieu khien h, yeu cau phai co he thong phan hoiYeu cau phai ieu chnh cac thong so vong ieu khien.Bao dng ton kem hn, ac biet la ong c DC servo

Hien nay a co ong c DC servo va AC servo. ong c DC servo ra i trc va a c sdung rat rong rai. Nhng sau ray vi kha nang cua viec s dung cac Transistor vi cng o lamviec ln , cac ong c AC servo a c che tao va c s dung ngay cang rong rai.

Hnh 2.18. ong c servo nam cham vnh cu



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Hnh 2.19. Hnh cat cua ong c Servo

2.6.5/ He thong phan hoi

Cac loai c cau phan hoi- Bien tr (potentionmeter)-

o goc quay (resolvers)- Bo ma hoa (Encoder)- May phat toc (Tachometers)

a. Bien tr (chiet ap): Co 2 loai c ban. Bien tr thang tuyen tnh (linear) va bien tr goc(Rotary). Nguyen ly hoat ong cua chiet ap c mo ta nh hnh 2.20.

Hnh 2.20-Chiet ap



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Chiet ap kha pho bien v gia thanh re, khong can cac ieu khien x ly tn hieu ac biet. Nhngchung b gii han ve o chnh xac, thng khoang 1% va hao mon c hoc.

b. EncoderEncoder la cam bien xac nh goc xoay tn hieu au ra la tnh hieu so. Theo cach nhan tnh hieuta co cac encoder sau: quang hoc (optical), ien dung (capacitive), t (magnetic), ban dan. Theonguyen ly xac nh v tr ta chia ra: Encoder tuyet oi va Encoder gia so.

Encoder tuyet oi (Absolute Encoder)Encoder dang Absolute co ngo ra la tn hieu c ma hoa nh phan. Ben trong Encoder bao gommot da tron ben tren co khac cac vach trong suot va cac vach toi xen ke theo ng tron ongtam. Tuy theo o phan giai cua Encoder ma so ng tron ong tam o nhieu hay t.

Xet tren mot ng vach tron, mot diode phat quang se phat chum tia i xuyen qua cac

vach trong suot va b chan lai nhng vach toi. Ben kia mat a, song song vi diode phat lamot diode thu co nhiem vu nh mot cam bien, ghi nhan cac tn hieu do diode phat a ti. Cobao nhieu ng vach tron th co bay nhieu diode thu tn hieu.Cac tn hieu oc c t diode thu se c a ra ngoai di dang tn hieu ien. Cac tn hieuien nay se co dang ma nh phan phan anh v tr cua truc quay Encoder. Thong thng e dedang trong che tao ngi ta ma hoa cac vach trong suot va vach toi theo ma Gray v vay e ngdung c trong cac he thong s dung ma Binary th ta phai co chng trnh chuyen oi t maGray sang ma Binary. Mot u iem na cua ma Gray la moi v tr ke nhau th ch co mot bitc thay oi, do o sai so ngo ra ch co the toi a la mot n v. Con ma Binary th co thegay sai so ln v khi thay oi v tr th co the ch co mot bit co trong so cao c thay oi con cacbit tren hang khac cha kp thay oi.

H2.24.Cau tao va nguyen ly hoat ong cua Optical Absolute Encoder



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Bang 2.2. ma Gray

Encoder loai Incremental:- Encoder loai Incremental co t kenh ngo ra hn loai Absolute, v the cau tao cua no ngian hn. Tren be mat da tron ben trong Encoder co hai ng tron ong tam. Moing co cac vach trong suot va cac vach toi xen ke nhau. Cung nh loai AbsoluteEncoder, diode phat quang se phat tn hieu i xuyen qua vach trong suot en diode thu.Hai diode thu nay se chuyen oi thanh tn hieu ien va a ra ngoai.- V tr cac vach trong suot cua hai ng lech nhau mot goc 090 va da vao goc lechpha gia hai tn hieu ra la sm pha hay tre pha ma ta xac nh chieu quay la thuan haynghch.- Nguyen ly hoat ong cua encoder nh sau

- ng tnh hieu ben ngoai (outer track) dung e xac nh v trng tnh hieu gia (middle track) dung xac nh hng quay- ng tn hieu trong (inner track) dung xac nh so vong.- Bo em se em so xung (canh len hoac xuong) e xac nh v tr.



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Hnh 2.23. Nguyen ly hoat ong cua Incremental EncoderDang xung ngo ra :

B

A

A

B

Quay theo chieu thuan

Quay theo chieu nghch



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c. ResoverLa thiet b tao ra cac tnh hieu ien theo ham so v tr cua goc quay. S o nguyen ly nh

hnh 2.26.

Hnh 2.26. Nguyen ly hoat ong cua Resolver

Stato bao gom 2 cuon day, cuon E1 va cuon E2 at vuong goc nhau. Roto gan cuon day E3 ccap ien bang hieu ien the bien oi hnh sin va quay tron. Tn hieu trong cuon day E3 b camng bi tn hieu trong cuon day E1va E2. Khi quay cuon E3 se gay len s khuech ai tn hieucam ng va bien thien theo ham so goc quay. ng vi moi v tr se tao nen mot gia tr ket hpkhac nhau gia hieu ien the cuon E1 va cuon E2 nh hnh 2.27.

Hnh 2.27.ien ap cuon E1la 1 sin( )iV V t = + , cuon E2la 2 cos( )iV V t = + .

Vi= hieu ien the vao = van toc goct = thi gian = dch pha

Ta co the xac nh goc quay da vao tng cap gia tr cua VE1va VE2. ong thi cung co the xacnh toc o quay da vao tan so cua xung.Tnh hieu ra cua Resolver la tng t, ta thung phai bien thanh tnh hieu so e x ly.



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d. Bo o van toc goc (Tachometer)Bo o toc o goc quay o lng van toc goc cua truc quay. Ta co the dung phat toc DC

(phat ta hieu ien the DC theo toc o quay) hoac phat toc AC(phat ra hieu ien the AC). Ngoaira ta con dung phat toc xung (Frequency type tachometer,Ky thuat pho bien la gan nam chamtren truc quay. Khi nam cham di chuyen qua loi cam bien co nh, dong ien c sinh ra. Moivong xoay cua truc tao ra mot xung ien ap, x ly tnh hieu xung nay ta se biet c toc oquay) . Hnh 2.28

Hnh 2.28o van toc goc



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2.7/ Chuyen ong noi suy

2.7.1/ Phng thc di chuyen daoco 2 phng thc di chuyen dao trong ieu khien so

+ Di chuyen iem ti iem (PTP)+ Di chuyen theo bien dang (Contour)

a. Di chuyen iem ti iemTheo phng thc nay, dao di chuyen theo cac hanh trnh thang ti v tr yeu cau. Chuyen ongnay c s dung e di chuyen nhanh - nh v.

Co 3 che o di chuyen PTP (hnh 2.29):

+ Di chuyen hng truc ( axial path )Dao c di chuyen tuan t theo cac truc : theo phng X, sau o theo phng Y, hoac ngclai

u iem: he ieu khien n gian, di chuyen theo cac truc oc lap+ Di chuyen theo phng xien 450:Dao di chuyen theo phng xien 450cho en khi at c mot trong hai thanh phan toa o ( Xhoac Y), sau o di chuyen theo mot truc e at c v tr yeu cau+ Di chuyen trc tiep(linear path):

Dao di chuyen theo hanh trnh ngan nhat ti iem ch.

Hnh 2.29. Cac phng phap di chuyen PTPb. Di chuyen theo bien dang (contour)

Dao di chuyen theo bien dang yeu cau e thc hien quy trnh gia cong. Bien dang (contour)

bao gom chuoi cac ng cong(curve), tuy thuoc vao hnh dang cua cac ng cong trong khonggian ta co the phan ra ng cong 2D, 2.1/2D, 3D, 4D, 5DHnh 2.30->2.33



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Hnh 2.30. He thong tao bien dang 2D

Hnh 2.31. He thong tao bien dang 2.1/2 D

Hnh 2.32. He thong tao bien dang 3 D

Ch tao ra cac ng cong trong matphang xy, truc z c ieu khien oclap vi xy

Co the ieu khien ongthi theo hai truc bat ky etao nen cac ng congtrong mat xy, yz, zx,phng con lai thng laphng tien dao

Co the ieu khien ongthi theo 3truc e tao nencac ng cong trongkhong gian. Thng dunge gia cong cac be matphc tap



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Hnh.2.33. He thong tao bien dang 4 DCac loai ng cong thng gap trong chuyen ong gia cong CNC la:

ng bac 1 (linear) : ng thang

ng bac 2 (conic) : cung tron, elip, parabol, hyperbolng bac 3 (cubic)

Cac ng bac cao hn . Thc hien: Cac ng cong bac cao c xap x bi chuoi phan thnh hoc c ban bi 3 nhom tren.# Trong ieu khien so, cac di chuyen c ban nay c goi la chuyen ong noi suy.

2.7.2/ Chuyen ong noi suy+ ieu khien so s dung 5 che o noi suy:- Noi suy ng thang, noi suy cung tron, noi suy ng xoan, noi suy parabol, noi suy bac 3+ Bo noi suy:

La thiet b ien t ( oi vi he NC), la phan mem ( oi vi he CNC) co cac nhiem vu :- Tm ra v tr trung gian cho phep hnh thanh mot bien dang cho trc trong mot gii han

dung sai xac nh trc- Noi suy mot cach thch hp cac yeu to bien dang oi hoi.- Toc o a ra v tr trung gian phai phu hp vi toc o chay dao cho trc.- i ti mot cach chnh xac cac iem ket thuc chng trnh a a ra trc trong chng

trnh.He thong CNC thc hien noi suy hai mc:- Noi suy tho: xac nh toa o cac iem au va iem cuoi cua oan bien dang.

- Noi suy tinh: thc hien tiep noi suy tuyen tnh gia cac iem trung gian nayTrong hau het cac may CNC thong thng ch s dung noi suy ng thang va noi suy vongtron cac dang noi suy khac nh parabol, hyperbol hay bac cao hn khong thc hien v chunghau nh khong co trong oi hoi thc te. Vi noi suy thang va noi suy vong, co the thc hienc nhng kha nang sau:

Noi suy thang theo 2 trong n trucNoi suy thang theo n trong n trucNoi suy vong theo 2 trong n trucNoi suy vong theo 2 trong n truc ong thi vi noi suy thang theo truc vuong goc ( noi suy

ng xoan oc)

Ngoai 3 truc ieu khien x, y,z conthem vao truc ieu khien goc quaycua ban may



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2.7.3/ Phng phap noi suy:

e xac nh gia tr can ve v tr tren cac truc rieng le, ngi ta ng dung cac phng phap noisuy khac nhau.Neu phan loai theo thuat toan s dung, ta co the phan bo noi suy theo 2 nhom:

- Nhom 1: cac thiet b lam viec theo nguyen tac ham anh gia va bo phan tch vi phan so- Nhom 2: cac thiet b lam viec theo nguyen tac tch phan so

Neu phan loai theo phng phap thc hien, co 2 loai:- S dung mach cng- S dung chng trnh

a. Phng phap noi suy ng thang (linear interpolation)+ Khai niem:

Dao c di chuyen t iem au ti iem cuoi hanh trnh theo chuoi oan thang. H.2.34+ Thc hien:Noi suy ng thang theo 2 hay 3 truc rat thong dung

+ Cac thong so yeu cau:Toa o iem au, toa o iem cuoiToc o di chuyen tren moi truc

+ Kha nang:Ve l thuyet, noi suy ng thang co the lap trnh quy ao cong bat k, nhng lng d lieu

can x l rat ln. S dung noi suy cung tron, parabol, ng xoan lam giam ang ke lng dlieu can lap trnh.



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Hnh 2.34. Noi suy ng thang

V du: Noi suy t iem A en iem ES dung phng phap Phan tch vi phan so DDA ( Digital Differenttial Analyse)Xet mot dao can chuyen ong t:

PA(iem khi xuat) en PE(iem ket thuc) theo mot ng thang vi mot toc o chaydaou xac nh. (hnh ve)

Goi L: oan ng t PAen PE.Vay trong thi gian T = L/u cac oan ng thanh phan (xE-xA) va (yE-yA) phai c thc hien.

Toa o v tr cac iem trung gian c tnh theo ham thi gian:

Chia thi gian T thanh cac khoang t= T/N u nho, phep tch phan cho phep thay bi phep congso:



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Vi moi bc cong, gia tr ve v tr lai tang them mot bc bang hang so. e am bao o chnhxac cua bien dang noi suy, cac bc cong phai nho hn suat n v f cua truyen ong chay dao.Thong thng f = 0,001 mm.

b. Noi suy cung tron+ Khai niem:

Dao c di chuyen t iem au ti iem cuoi hanh trnh theo mot cung tron bi mot caulenh (block) n gian, thay the cho rat nhieu cau lenh noi suy ng thang. Hnh 2,35+ Thc hien:

Noi suy ng tron theo 2 truc+ Cac thong so yeu cau:

Toa o iem au, toa o iem cuoi, tam hoac ban knh cung tron.Toc o di chuyen tren moi truc

+ Kha nang:Noi suy cung tron hay toan bo ng tron.

+ Phng phap thc hien:

Phng phap noi suy DDA cung c ng dung trong noi suy cung tron.

Hnh 2.35. Noi suy cung tronvdu: Noi suy cung tron t PAen PE:Noi suy vongPA: iem khi xuatPE: iem chP: iem thuoc ng congT: tg t PA en PEt: tg t PA en P



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T hnh ve:Muon chay cat theo ng cong, nhng iem trung gian tren bien dang phai c xac nh t

bo noi suy trong moi quan he phu thuoc vao thi gian chay cat.Theo o:

x = Rcosy = Rsin

vi = 2t/T;T: thi gian chay het toan vongth:

Lay tch phan theo thi gian, ta co toc o thanh phan tren tng truc rieng le:

=> dx = -(2/ T)y(t)dt; dy = -(2/ T)x(t)dt;Vi o chnh xac u dung, phep tch phan tren co the thay the bi phep cong cac gia so ngdch chuyen. Do o:

c. Noi suy xoan oc (Helical Interpolation).La phng phap noi suy ket hp gia noi suy ket hp gia noi suy cung tron theo hai truc va noi

suy tuyen tnh theo truc th 3. (hnh 2.36)



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Hnh 2.36. Noi suy xoan oc

d. Noi suy parabol (Parabolic Interpolation)Dung iem khong thang hang e xap x ng cong co bien dang t do. Laoi noi suy nay thngdung trong tao khuon mau khi ma cac ng cong bien dang t do(free shape) c yeu cauthay v la cac ng cong co bien dang chnh xac. Ta co the dung noi suy Parabol e tao cacng cong bac cao. So vi noi suy ng thang, noi suy parabol giam khoang 50 lan so caciem can lu tr. Hnh 2.37

Hnh 2.37. Noi suy ParabolTa co: x = xv+ Au2; y = yv+ 2Au=> Xn+1= xn+ (yn yv)Au + (Au)

Yn+1 = yn+ 2Au

e. Noi suy bac 3 (Cubic)La phng phap xap x bien dang bang ng cong bac 3. phng phap nay thng c dungtao cac be mat rat phc tap nh khuon vo xe hi, may bay

A

PF(Focus)

Pv

PH

PL

uL= yL/2A, uH= yH/2Au = (uH/N -> uL/N

n = 1 : N



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40

Chng 3: C S LAP TRNH NC------------------------------

3.1/ Mot so khai niem c ban.

3.1.1/ Chng trnh NC:Bao gom chuoi ch th di chuyen dao, ch th ong ngat va phu tr can thiet e ieu khien may tong thc hien cong viec gia cong.

3.1.2/ Lap trnh NC:Xac lap tien trnh di chuyen dung cu cung cac ch th lap trnh cu the va lu tr cac thong tin naytren thiet b mang tin di dang ma lenh phuc vu cho qua trnh oc d lieu t ong bi he ieukhien

3.1.3/ nh dang cua mot chng trnh NC:nh dang pho bien nhat la nh dang a ch lenh (word address format). nh dang nay baogom cac ma lenh (commands) c truyen en he thong servo, rle, cong tac e thc hien cactac vu gia cong. Cac ma lenh lien ket nhau tao thanh khoi lenh (Block). Bo ieu khien may sethc hien cac thao tac ieu khien theo tng khoi lenh mot. Ket thuc mot khoi lenh se co dau ketthuc khoi (EOB). Cau truc cua mot chng trnh CNC c minh hoa nh hnh 3.1.

Hnh 3.1. Cau truc chng trnh NCa. a ch lenh:La ch cai alphabet au lenh, ch th v tr lu tr d lieu so theo sau. Cac ch cai c dung

trong ma lenh c the hien tren bang3.1.



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Bang 3.1. Cac ma lenh NC

Nhom lenh a ch Y ngha

So hieu chng trnh O So hieu chng trnhSo th t khoi lenh N So th t khoi lenhLenh G G Phng thc noi suy chuyen ongKch thc X,Y,Z Truc chuyen ong tnh tien chnh

U,V,W Truc chuyen ong tnh tien phuA,B,C Truc quay chnhI,J,K Toa o tam cung tronR Ban knh cung tron

Toc o chay dao F Toc o chay daoToc o truc chnh S Toc o quay truc chnhChon dao T So hieu daoLenh phu M Lenh ong/ ngat (ON/OFF)

B ieu khien ban xoaySo hieu thanh ghi dchchnh

D,H So hieu thanh ghi dch chnh

Dng tam thi P,X Thi gian dng tam thiLenh goi chng trnh P So hieu chng trnh con;

So lan lap lai chng trnh con

Tham so P,Q Tham so cua chu trnh

b. Cau Lenh ( Word):La chuoi k t, so, ch th mot ai lng ieu khien nhat nh.V du: N10 : so th t khoi lenh; G01 : noi suy ng thang; X2.0: toa o phng X; F300 toc ochay dao; T07 : so hieu dao; M09 : ngat thiet b chat lam nguoi

c. Khoi lenh (Block) :La chuoi cac lenh ay u e thc hien mot thu tuc di chuyen hoac mot tac vu hoat ong cuamay. Khoi lenh c coi la n v c ban cua chng trnh CNC. Cau truc ien hnh cua khoi

lenh nh sau:N__ G__ X__ Y__ M__ S__ T__ EOB(;)

Th du:N05 G21; :he metN10 G90 G00 X0 Y0; : toa o tuyet oi, chay dao nhanh en (0,0)

3.1.4/ Cau truc chng trnh CNC:Cau truc tong quat cua chng trnh CNC bao gom:

- au tap tin ( Tape start): k t (%) khai bao bat au tap tin chng trnh.

- Nhan tap tin (Leader section): Tieu e tap tin chng trnh.



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- au chng trnh (Program start) : k t khai bao bat au chng trnh.- Than chng trnh (Program section): Cac lenh gia cong- Chu thch (Command section): ch dan hoac chu thch cho ngi van hanh- Cuoi tap tin (Tape end): k t khai bao ket thuc tap tin chng trnh.

Co 2 loai chng trnh:Chng trnh chnh (main program)Chng trnh con (subprogram): La chng trnh phu c goi t chng trnh chnh, thng

dung khi trong chng trnh chnh co nhieu oan lap lai.

3.2. Phng thc lap trnh NC

3.2.1/ Lap trnh trc tiep:Ngi lap trnh co the t bien soan chng trnh NC tren c s nhan dang hoan toan chnh xactoa o chay dao. Thng s dung cho cac trng hp gia cong n gian. Truyen chng trnh NCc lap vao he ieu khien may bang 2 phng phap (xem hnh 3.2):

- Nhap t cac thiet b ngoai: a mem, bang t, cong giao tiep- Nhap t Panel ieu khien theo che o MDI (Manual Data Input)

Hnh 3.2. Phng phap lap trnh trc tiep.

3.2.2/ Lap trnh T ong:

Ngi lap trnh s dung ngon ng ho tr lap trnh hoac phan mem CAD/CAM nh cong cu tr

Khoi lenh 1

Khoi lenh 2

...Goi chng trnh con

Khoi lenh n

Khoi lenh n+1

Khoi lenh 1Khoi lenh 2

...Tr ve chng trnhchnh



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giup e chuyen oi t ong d lieu hnh hoc va d lieu cong nghe thanh chng trnh NC. Co 3phng phap lap trnh t ong:

- Lap trnh bang phan mem NC (NC Editor)- Lap trnh bang ngon ng x l hnh hoc- Lap trnh bang phan mem CAD/CAM

Hnh 3.3. Phng thc lap trnh t ong

3.2.3/ Lap trnh theo cong nghe Cad/Cam

Laphng phap lap trnh t ong co rat nhieu u viet. Phng phap lap trnh nay cho phep ta taonen c cac chng trnh gia cong nhng chi tiet rat phc tap mot cach de dang, chnh xac. Dovay lap trnh theo cong nghe CAD/CAM ngay nay c s dung rat rong rai trong cong nghe gia

cong CNC. Ve c ban, CAD/CAM bao gom 2 thanh phan.CAD : xac lap hnh hoc chi tiet gia cong, tao nen mo hnh vat the can gia cong bao gom caciem, ng, be mat, khoi.CAM : s dung d lieu hnh hoc c tao, e tao ng chay dao va thc hien chc nang quan lva ieu khien san xuat nh lap trnh che tao, lap ke hoach san xuat, quan l chat lng, hoachnh nguon lc san xuat

Quy trnh lap trnh NC theo cong nghe CAD/CAM gom cac bc c ban sau:a.Thiet ke mau gia cong tren phan mem CADb.Xac lap tien trnh gia cong

c. La chon cong nghe gia cong NC (phng thc chay dao) cho tng bc gia congd. Xac lap thong so NC cho chc nang gia cong NC tng nge. Thc thi trnh x l oi vi chc nang gia cong NC e tao ng chay dao (toolpathgeneration)f. Thc thi trnh hau x l (post processing) bien dch d lieu chay dao thanh chng trnh NC



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CHNG 4: CONG NGHE PHAY NC---------------------

4.1. May phay CNC4.1.1. Phan loai:Viec phan loai may phay CNC ch mang tnh tng oi. Tuy thuoc vao tnh van nang, so dao cothe tch trong o tch dao (tool magazine) ta chia may phay CNC thanh cac loai c ban sau.

a. May phay CNC (CNC Milling machine)May phay CNC thng dung e ch cac may phay co 1 hoac mot vai dao trong o tch dao, thongthng o tch dao khong cha qua 12 dao va co dang mam xoay (Turet). Da vao cau truc may

ta phan may phay loai nay lam 2 loai.Loai th 1:spindle thang ng (vertical CNC milling machine), Hnh 4.1.a.Loai th 2: spindle ngang (Horizontal CNC milling machine), Hnh 4.1b.

Hnh 4.1a. may phay CNC ng Hnh 4.1b. May phay CNC ngang

b. Trung tam phay CNC (CNC Milling Center)La loai may phay CNC co tnh van nang cao hn, thong thng so dao co the tch trong o tchdao t 12 en hang tram dao. O tch dao (Tool Magazine) thng co dang xch quay, dao cthay t ong hoac dung Robot cap dao.Hnh 4.2



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Hnh 4.2. Bo tch dao trong trung tam phay CNC

Tng t may phay CNC, trung tam phay co the la trung tam phay ng (vertical MillingCenter) hoac trung tam phay ngang (Horizontal Milling Center)

c. Trung tam phay-tien CNC (Milling-Turning Center)La trung tam phay CNC tch hp va co kha nang lam viec nh may tien CNC. Loai may nay cotnh van nang rat cao. Tuy nhien ket cau rat phc tap, at tien.

Ngoai ra tuy vao kha nang ieu khien theo cac truc ta con chia ra may phay CNC 2 truc,2.1/2 truc, 3 truc, 4 truc va 5 truc.

4.1. 2. Quy nh cac truc tren may phay CNC

Nhng may cong cu thong thng co 3 truc chnh X,Y, Z co chieu nhat nh.Tuy nhien co may4,5 truc. Them 3 truc quay xung quanh cac truc tng ng ky hieu la A, B hoac C. Tuy theo loaimay ma cac truc bo tr khac nhau va do o co chieu khac nhau. Phng chieu cua cac truc mayc xac nh theo quy tac ban tay phai. Hnh 4.3a mo ta phng phap xac nh phng chieucua cac truc X,Y, Z. Hnh 4.3b mo ta cach xac nh chieu quay dng quanh cac truc tng ng

Lu y:lap trnh, van hanh tuan theo nguyen tac ch co dao di chuyen, con phoi (banmay) co nh. Mac du thc te co the dao co nh con ban may chuyen ong.



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Ngon cai ch chieu dng truc X, ngon tro ch chieu dng truc va ngon gia ch chieu dngtruc Z

Hnh 4.3. Quy tac ban tay phai

4.1.3. Cac iem tham chieu tren may phay CNC ( Reference Zero Points )Cac iem tham chieu tren may la cac iem c s hoac iem bat au c s dung e tnh toa ocac iem khac. Ta con goi la iem khong (zero points). He ieu khien CNC dung 4 loai iemtham chieu sau:

iem khong(zero) cua may (Machine zero point )

iem rut dao tham chieu (Reference return point )

iem khong (zero) cua chi tiet (Work zero point )

iem khong(zero) khi lap trnh (Program zero point )

Machine Zero Point

La goc toa o may. c cai at bi nha che tao va khong the sa oi. iem khong cua mayc at ten M va ky hieu nh hnh 4.4. Vi may tien, iem khong cua may thng at tai tammat au cua truc chnh. Vi may phay no thng at tai iem gii han cua cac truc.

Thong thng iem Zero cua may khong dung lam iem tham chieu e lap trnh. iem nay

thng c dung vao cac muc ch sau.

Cai at ban au cho may (Initial setup of the machine)

Lam tham chieu cho cac iem tham chieu khac nh: reference return points, work zeros,va program zeros.

Lam v tr an toan e thay dao.



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Hnh 4.4. iem khong cua may

Reference Return Point

Reference return points la cac v tr ma ban may hoac truc chnh se tr ve o nham thc hienmot tac vu nao o. iem nay c at ten R va c ky hieu nh Hnh 4.5. Mot so he ieu hanhcho phep ch nh 4 iem rut dao tham chieu. Thong thng oi vi may phay iem khong cuamay la iem tham chieu th nhat . iem tham chieu th 2,3,4 c ch nh bang viec cai atcho bo ieu khien may. No co the c at tai bat ky iem thuan tien nao trong vung lam vieccua may. Vi may tien iem tham chieu la iem xa nhat trong vung lam viec.

Hnh 4.5. iem tham chieu cua may ( Reference return point)

V tr cua iem tham chieu th nhat c xac nh trc, chnh xac so vi iem khong cua may.Do vay no co the c s dung cho viec ieu chnh, kiem tra(calibrating and regulating) hethong o lng cua bang trt ban may va truc chnh.



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iem tham chieu c dung ac biet trong 4tnh huong sau:

Khi khi ong may, tat ca cac truc nen luon c a ve iem tham chieu e

kiem tra he thong o lng. May can a lai ve iem tham chieu e thiet lap lai toa o chnh xac trong cac

tnh huong nh: mat ien, van hanh khong ung lam mat i d lieu hien tai.

Khi thay dao.

Kh ket thuc chng trnh gia cong e Reset lai bo ieu khien.

Work Zero Point

La goc toa o cua he toa o gan lien vi phoi. V tr nay c cai at bi ngi van hanh mayva c at tai bat ky v tr thuan li nao o tren phoi. Work Zero Point c at ten la W va khieu nh hnh 4.6.

a. at tai be mat mam cap b. at tai mat au chi tiet tien

c. at tai goc chi tiet d. at tai tam chi tiet

Hnh 4.6. iem khong cua chi tiet.



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Program Zero Points

La goc toa o cua chng trnh gia cong. No dung e xac nh cac v tr trong chng trnh gia

cong. Do vay phai c ch nh trc khi thc thi chng trnh. Program Zero pointc atten P va c ky hieu nh hnh ve. Program Zero pointthng trung vi Work Zero point.Tuy nhien no co the c at tai bat ky v tr thuan li nao khac nh Hnh 4.7

Hnh 4-7. iem Zero lap trnh

Ta co the nh ngha nhieu Program Zerosnham thuan li khi lap trnh gia cong cac chi tietphc tap. Trong trng hp nay iem khong au tien c goi la program zerotat ca cac iemkhong sau o (c xac nh so vi Program Zeros) goi la iem khong cuc bo ( local zero point).

Hnh 4.7. Local Zero Point

4.2. Dung cu phay CNC

He thong dung cu dung cho may CNC noi chung, cho may phay CNC no rieng bao gom cacthanh phan sau: He thong thay dao t ong (Automatic Tool Changer: ATC), o ga dao (ToolHolder), dung cu (cutting tool) nham am bao cac yeu cau sau:

- Ga c nhieu dao vi o chnh xac cao



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- Thay dao t ong, nhanh- Co the hoan oi gia cac dao.

4.2.1. He thong thay dao t ong.Co nhiem vu lay dao t o cha dao, ga vao truc chnh va lay dao t truc chnh cat vao o chadao mot cach nhanh chong. O cha dao (Tool magazine) la he thong lu tr dao co the nhan bietc cac v tr va truy xuat t ong. Xem lai hnh 4.2

4.2.2. O ga dao.O ga dao se giup thuan li cho viec thay oi nhieu dao vao chuc chnh may mot cach nhanhchong, chnh xac. Cau tao o ga dao nh hnh 4.8

Hnh 4.8. O ga dao (Tool Holder)

au ga con (Tapered Shank)

au ga con dung lap O ga dao len truc chnh. Theo tieu chuan ANSI co 6 c o ga dao con cban sau: #30, #35, #40, #45, #50, va #60 may cang ln dung au ga con co so hieu cang ln. ocon tieu chuan la 3.5 in./ft ( he so 7:24).

Taper Shank No. Type of Machine

#60 May rat ln (Very large machines )#50 May c trung (Medium size machines) (20 to 50 HPs)#40 May c nho (Small size machines )#30 May c rat nho (Very small machines)

Vanh o ga dao (Flange)

Dung e o ga dao co the c gap gi bi tay gap thay dao. Co 2loai c ban la V-flange andBT-flange. V-falnges thng dung oi vi cac dao kch thc he inch, BT-flanges Thngdung ga dao kch thc he met. BT-Flankc dung nhieu nhat va chau au.



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V-Flange

BT-Flange

Num co nh o dao (Retention Knob )

Num co nh o dao dung e thanh khoa cua truc chnh (locking drawbar ) keo o ga dao cho sietchat vao truc chnh va tha no ra t ong. Xem hnh 4.9

Hnh 4.9. Ket cau bo phan ga dao len truc chnh

Adaptors(bo ga than dao)

Bo ga than dao c thiet ke vi nhieu kieu khac nhau nham ga c nhieu loai va nhieu cdao khac nhau. Thong thng o ga dao c at ten theo bo ga than dao tng ng. Thng gapla: end mill holders (o ga dao phay ngon), face mill holders (o ga dao mat au), tap holders

SHANK

SIZE [in.]

A GAGE

LINE

B C D

V30 1.250 1.812 1.875 1/2-13

V40 1.750 2.500 2.687 5/8-11

V45 2.250 3.250 3.250 3/4-10

V50 2.750 3.875 4.000 1-8

MODEL D1 D2 1 2 L1 L2 L3 L d1 d2 G

BT20*

BT30 46 38 20 2 48.4 34 24 70.4 31.75 12.5 M12

BT40 63 53 25 2 65.4 70 30 92.4 44.45 17 M16

BT50 100 85 35 3 101.8 90 45 139.8 69.85 25 M24



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(o ga taro), collet holders (o ga dung ong an hoi), boring bar holders (o ga thanh doa),Morse taper holders, Jacob taper holders, va straight shank holders (o ga than dao tru).Hnh 4.10 la s o phan chia cac loai o ga dao khac nhau theo bo ga than dao.

Hnh 4.10. Cac loai o ga dao



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4.2.3. Dung cu phayLa bo phan trc tiep lam nhiem vu cat got. Dung cu dung trong cong nghe phay CNC noi chunga dang hn so vi may cong cu truyen thong. Tuy thuoc vao tng yeu cau cu the ta s dungcac loai dung cu khac nhau. Ve c ban dung cu dung trong cong nghe phay CNC bao gom cacloai sau.

a. Dung cu gia cong lo: Khoan, khoet, doa, ta ro.b. Dao phay ngon (End mill): dao phay ngon au phang (flat End Mill), au chom cau (Ball

End Mill), vat mep (Chamfer End Mill), Dao phay con (Tapper End Mill), Dao cung lun(Corner End Mill), Dao qua cau (Dove Mill).

c. Dao phay mat au (Face Mill)Tren hnh 4.11 la mot so loai dao thng gap. e hieu ro hn ve cac loai dao nay, xem lai moncong nghe che tao may, nguyen ly cat.

Hnh 4.11. Mot so dung cu dung trong cong nghe phay

4.3. Cac quy trnh phay CNC ( CNC Milling Process).Tren may phay CNC ta co the thc hien cac quy trnh sau: Phay khoa mat (Facing ), phaybien dang bao quanh ( Profiling ), phay ht phan vat lieu ben trong, phay hoc (Pocketing), phay ranh (Slot cutting ), gia cong lo (Hole machining ), gia cong mat 3D (3-D surface

machining). Cac Quy trnh nay c mo ta cu the cac bang4.1.



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Bang 4.1 . Milling Processes

( Loai quy trnh) ( minh hoa)



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4.4. Van hanh may phay CNC.

Cac may CNC khac nhau, thao tac van hanh se khac nhau. Muon hieu cu the va co the van hanhthanh thao ngui van hanh (operator) can phai tham khao cac tai lieu hng dan s dung vanhanh (Operators Manual) va phai co kinh nghiem. Trong phan nay, ch gii thieu chung ve cacchc nang van hanh tren cac may CNC. T cac kien thc chung nay se giup ban de dang hnkhi oc tac tai lieu hng dan van hanh may phay CNC.

4.4.1. Van hanh thu cong (manual operation)

a. Tr ve iem tham chieu (reference position return, Zero return, Home Return).Nh tren a gii thieu ve khai niem va cong dung cua iem tham chieu. che o van hanhbang tay, e tr ve iem tham chieu ta nhan nut sau o chon tng truc e adao di chuyen nhanh ve iem tham chieu theo tng truc xac nh hoac co the di chuyen 3 trucong thi (ALL). Toc o di chuyen a c cai at trc phan tham so. Khi tr ve iem thamchieu, en LED bat sang. Co the thay oi toc o di chuyen bang cach s dung chc nang RapidTraverse Override.

b. Jog feed:La phng phap van hanh bang tay nham di chuyen dao theo truc va chieu t chon. e thchien, ta chon chc nang roi gi lien tuc phm truc muon di chuyen e di chuyen

dao en iem mong muon.Tng t, co the ieu chnh toc o di chuyen bang cach s dung chcnang Feed Rate Override. Chc nang Jog feed thng dung cho cac muc ch sau: canh chnhdao, phoi, cai at toa o gia cong, di chuyen dao xa khoi phoi e thc hien mot tac vu nao o,gia cong bang tay.

c. Incremental feed (Rapid move):Khi che o nay, dao se di chuyen theo truc, chieu va khoang cach chon trc. Thc hien bangcach chon chc nang Incremental Feed (Rapid move), noi chon phiem ch truc va chieu tngng, nhap vao khoang cach muon di chuyen.

d. Manual handle feed:Chc nang nay dung e di chuyen dao theo truc va chieu t chon bang viec quay tay xoay trenbo phan tao xung bang tay (Manual pulse generator). Luc nay xung tao ra c a trc tiepvao ong c lam di chuyen cac truc may theo chieu mong muon. Ta co the ieu chnh viec tiennhanh hay cham cua cac truc bang viec ieu chnh che o di chuyen tren bo phan nay. Chonchc nang nay thng e set toa o gia cong, canh chnh dao, a dao vao lai vung lam viec khivt c ... Chc nang nay khong thong qua bo ieu khien cua may nen rat an toan khi van hanh.



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4.4.2. Van hanh t onga. Memory operation:

Chng trnh c lu trong bo nh khi mot chng trnh bat k c chon. Khi nhan nut tren bang ieu khien, may se t ong chay gia cong chi tiet theo chng trnh c chon.Luc nay en cycle bat sang. Mot khi qua trnh memory operationc thc hien, cac qua trnhsau ay se c thc thi:

Mot block t chng trnh c oc.Block c giai ma.Lenh tng ng c thc thiLenh trong block ke tiep c oc.

e thc hien ta chon che o tren bang ieu khien, chon nut Program > Load (select)

program roi chon chng trnh muon chay e nap vao bo nh may CNC.

Lu y: khi v ly do nao o phai thoat khoi chng trnh dang gia cong nh: dao gay phai thaydao mi, dng khan capSau khi a khac phuc s co ta muon tiep tuc gia cong phan con lai thlam tng t nh tren, nhng nhan nut , luc nay he ieu hanh yeu cau nhapvao so cua khoi lenh ma ta muon tiep tuc. Luc nay dao se di chuyen nhanh en v tr trong khoilenh tren, cac lenh toc o truc chnh, thay dao van thc hien bnh thng.

b. MDI operation (manual data input)La che o ieu khien may bang cac lenh NC trong MDI mode, chng trnh c thc hien cungcung nh dang nh memory operation nhng c thc hien bang MDI panel (chon nutMDI tren bang ieu khien may). Chng trnh che o MDI khong dc lu vao may va se mati khi tat nguon hoac khi chuyen qua che o khac. MDI operationch s dung cho nhngchng trnh n gian va khong can lu tr hoac dung chay th may, kiem tra toa o cai at,thay dao, cai toa o G92

c. DNC Operation:Khi che o nay,may khong van hanh theo chng trnh trong bo nh ma oc trc tiep chngtrnh (thng t mot may tnh khac ket noi vi may CNC) thong qua bo nhap-xuat. Che o nay

s dung khi chng trnh qua ln khong the cha trong bo nh may CNC.

4.4.3. Van hanh kiem tra (test operation)

a. Feedrate Overirde:ai lng tien dao (feedrate) trong chng trnh se c hieu chnh tang hoac giam theo phantram c la chon tren nut Jog feed rate override. Thng s dung e chay kiem tra chngtrnh. oi khi trong chng trnh ta dung lng tien dao be e am bao an toan, khi gia cong tathay co the tang lng tien dao ma van am bao cac yeu cau th ta dung chc nang nay e tang

toc o tien dao.



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Vd: khi F=100mm/min c xac nh trong chng trnh, neu ta chnh nut Jog feed rateoverrideen so 50% th dao se di chuyen vi toc o 50mm/min

Chc nang nay con dung e thay toc o tien dao che o Jogfeed

b. Rapid Traverse Overirde:Cung tng t nh chc nangJog feed rate overridenhng thng ch co 4 bc ( 0, 25%, 50%,100%). Dung e giam toc o chay dao nhanh. Rapid traver se Overide s dung cho:

- G00- Tr ve iem tham chieu t ong: G27, G28, G30- Tr ve iem tham chieu bang tay (Manual Home Return).- Che o Dry run

c. Dry Run:Dao di chuyen vi toc o tien dao nhanh. Chc nang nay dung e kiem tra ng chay dao khichi tiet cha c ga at hoac ta chnh toa o cho dao chay pha tren chi tiet (khong cat). Dungnut Rapid Traversee thay oi toc o tien dao

d. Single Block:Nhan nut e bat au che o nay (en single block bat sang) va nhan lai nutsingle block (nha ra) e bo che o nay. che o nay khi chng trnh c thc thi, dao sedng sau moi block. Chc nang nay giup ta kiem tra tng khoi lenh.

e. Block skip:Chc nang nay se bo qua khong thc hien cac khoi lenh trong chng trnh c anh dau bangky t bo qua khoi lenh au khoi (thng la ky t \). Chc nang nay c kch hoat khi nutBlock skip c chon, luc nay en block single bat sang.

f. Optional Stop.Dung ket hp vi lenh M01 trong chng trnh e dng chng trnh co chon la. Khi nutOptional Stopc chon, chng trnh se dng khi gap cau lenh M01, neu Optional Stopkhong

c chon, cho du co gap M01 chng trnh van khong dng. e tiep tuc chng gia cong tachon nut

4.4. 4. chc nang an toan (safety functions)a. Emergency Stop:Neu ban nhan Emergency Stop, may se lap tc ngng hoat ong. Emergency Stop ngat tc thhoat ong cua tat ca cac motor. Chng trnh c reset lai t au. Emergency Stopch nendung khi gap cac s co rat nguy hiem can dng ngay moi hoat ong cua may nh: chap mach,va ap nguy hiem Sau khi dung Emergency Stop can phai a may ve iem tham chieu .



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b. Feed Hold :Khi s dung nut nay, dao se ngng di chuyen (nhng spindle van quay), khi nha nut, dao tieptuc di chuyen va moi hoat ong cua may se tiep tuc. Nut feed hold dung khi gap cac s co canphai dng di chuyen truc chnh nh: co nguy c va cham gia dao va phoi, gay dao

c. Over Travel:Khi dao di chuyen vt qua c hanh trnh (stroke end) c xac nh bi nut gii han pham vi(limit switch), dao se giam toc va ngng. Luc nay thong bao Over Travel hien th. Nguon iencung cap cho cac ong c truyen ong bi ngat.

Khac phuc: nhan nut Reset sau khi di chuyen ve lai pham vi an toan bang Manual HandleFeed.

4.5. Thong so NCBao gom cac thong so ve dung cu (tool parameters) va cac thong so gia cong (machiningparameters):

4.5.1. Thong so dung cu:a. So hieu dao:La thong so ch th v tr cha dao tren bo phan tr dao. Vd: khoi lenh M06 T05: se thc hienlay dao v tr so 5 tren bo phan tr dao gan vao truc chnh va gan dao hien tai tren truc chnhvao v tr so 5 tren bo tch dao.

b. Thong so hnh hoc cua dao.La cac thong so ve kch thc dao cat nh: ng knh dao D, ban knh mui dao R, Chieu daidao, goc mui dao

c. Thong so bu tr dao.e thuan tien cho viec lap trnh cung nh hieu chnh chng trnh, cac he ieu khien CNC cochc nang lu tr gia tr bu tr chieu dai dao ( tool length offset), tc la khac biet gia chieu daidao gia nh khi lap trnh va chieu dai dao khi gia cong thc te va bu tr ban knh (radius

Compensation). Cac thong so nay c cai at vao trong vung Offset cua may CNC. Ta se noiro van e nay phan bu tr dao.

4.5.2. Thong so gia cong:Thong so gia cong bao gom cac thong so c ban sau.

a. Toc o truc chnh ( spindle speed):Xac lap toc o quay truc chnh theo so nguyen vong/phut, trong chng trnh thong so nay cch nh bi lenh S. ta phai dung lenh M03, hoac M04 e kch hoat truc chnh trc khi dunglenh S. Vd: M03 S1200: quay truc chnh thuan chieu kim ong ho 1200 vong/phut. Ta a biet



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trong gia cong c kh toc o cat c xac nh theo n v m/ph. e tnh toc o quay truc chnh

t toc o cat ta dung cong thc sau:D

Vn

1000=

e dng truc chnh ta dung lenh M05. Ta co the thay oi toc o truc chnh a ch dnhtrong chng trnh bang Spindle Overide

b. Toc o chay dao( Feedrate):Xac lap toc o di chuyen dao khi gia cong. Co 2 loai chay dao:- Chay dao trong mat phang ngang xy ( cutting feed rate).- Toc o an dao theo phong z (plunge feed rate)Trong chng trnh, toc o tien dao c ch nh bi lenh F.

V du: trong he met, cau lenh F100 co ngha la tien dao 100mm/phc. Lng d gia cong (Stock to leave):Xac lap be day vat lieu c e lai cho cac bc gia cong tiep theo. Gia tr lng d khac nhau,pham vi chay dao se khac nhau.

d. Mat phang tien dao ( rapid depth, feed plane) :Thong so nay xac lap cao o Z dao can di chuyen ti vi toc o chay dao nhanh, trc khi batau gia cong. Cao o nay cung la chuan thoat dao sau khi gia cong(clearance plane).

e. Bc chay dao ngang ( stepover distance):La khoang cach ng tam dao gia hai ng chay dao ke can. Bc chay dao ngang phai nhohn ng knh dao (40-75% ng knh dao).

f. Chieu sau cat ( Depth cut)La chieu day lp kim loai c ht di sau moi ng chay dao.

g. Mat phang gia cong (tool plane):Xac lap mat phang chay dao. Mat phang chay dao co the la: XY, XZ, YZ tng ng ma lenhG17, G18, G19

h. Dch chnh dao (cutter compensation):La s dch chnh tam dao so vi ng chay dao lap trnh. Xac lap dch chnh dao theo haiphng thc:

- Dch chnh theo bo ieu khien CNC: c xac lap bi cac t lenh G41, G42, G40.- Dch chnh bang cach tnh lai ng chay dao: Chng trnh gia cong khong bao ham cac

t lenh dch chnh G41, G42, G40.

i. Ti nguoi



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Xac lap che o lam nguoi bang phun sng (M07), bang dung dch (M08),tat che o lam nguoi(M09).

Viec xac nh che o cat got hp ly la cong viec rat phc tap va oi hoi rat nhieu kienthc ve ly thuyet va kinh nghiem. Cac kien thc nay c trang b trong cac mon:CNCTmay, Nguyen ly catSau ay la bang che o cat trung bnh khi gia cong tho mot so vatlieu dung dao thep gio (HSS).

Bang 4.2Vat lieugia cong

Gang Nhom Thep

ngknh dao

(mm)

Toc o cat(m/ph)/ toc o

truc chnh

Lngtien dao

(mm/ph)

Toc o cat(m/ph)/ toc

o truc chnh

Lngtien dao

(mm/ph)

Toc o cat(m/ph)/ toc

o trucchnh

Lngtien dao

(mm/ph)8 28/1100 115 126/5000 500 25/1000 10010 28/900 110 129/4100 490 26/820 8212 29/770 105 130/3450 470 26/690 8214 29/660 100 132/3000 440 26/600 8016 30/600 95 133/2650 420 27/530 76

- Khi gia cong bang dao hp kim toc o cat co the chon cao hn gap 2-3 lan.- Gia cong tinh ta thng chon toc o cat cao hn, con lng tien dao chon nho hn.



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4.6. Cac lenh lap trnh c ban

4.6.1. Cac lenh di chuyen daoTrong Cong Nghe phay CNC, thong thng co 3 phng thc di chuyen dao sau: chay dao nhanh(G00), noi suy ng thang (G01), noi suy cung tron (G02,G03)

a. Chay dao nhanh (G00) :- La lenh Hnh thc (Modal)- Lenh G00 ch th di chuyen dao theo hanh trnh thang, vi toc o chay dao nhanh.- Cau truc G00 x_y_z_; Vd: G00 X100.Y100.- Co 2 hnh thc chay dao nhanh: Chuyen ong trong mat phang XY va chuyen ong tien daotheo phng Z, trong o lu y van e tien dao va thoat dao.

- Hanh trnh chay dao nhanh c thc hien trc tiep theo ng thang ti iem ch th.- Lenh G00 dung e dnh v nhanh dao cat en v tr can thiet e thc hien gia cong tai o.

* Lu y:Khong s dung feedrate F khi chay dao nhanh.

Ap dung G00 : lap trnh chay dao nhanh trong khong gian XYZ:T iem (-1.,-1.,0.5) ti iem (4.5,3.,2.)T iem (20.,20.,50.) ti iem (67.,15.,4.5)

b. Chay dao noi suy ng thang (G01):-Lenh hnh thc (Modal)- Ch th di chuyen dao theo bien dang thang, vi toc o nh ngha bi ham Ff (feedrate), ti vtr xac nh bi t kch thc X_ Y_Z_.- Neu khong xac nh F, xem nh F=0 => khong di chuyen. Gia tr cua F c s dung cho enkhi co gia tr mi c xac lap.- G01 c dung e gia cong theo cac ng thang- Cau truc: G01 X_ Y_Z_ F_;vd: G01 X100.Y100.F200.;

X12.Y2.5 ;

Ap dung G00,G01 : lap trnh chay daoT goc toa o en iem A (2.,2.,0.5) -chay dao nhanhTi iem B(2.,10.,0.5); Ti iem C(14.0,10.0,0.5); Tr ve A. Chay dao toc o 200mm/phut

c. Chay dao noi suy cung tron (G02,G03):- Lenh hnh thc (Modal)- Lenh G02,G03 ch th di chuyen dao theo bien dang cung tron vi toc o fc nh ngha bilenh F. G02 ng di chuyen thuan chieu kim ong ho, G03: ngc chieu kim ong ho.Co the lap trnh noi suy cung tron theo 2 phng phap: phng phap I-J-K va Phng phap R.



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Hnh 4.12. Noi suy cung tron

Cau lenh noi suy cung tron gom 4 thanh phan d lieu va co cau truc nh sau:

Bang tom tat:

D lieu Lenh Y ngha

1. Mat phang gia cong G17G18G19

Cung song song vi mp XYCung song song vi mp ZXCung song song vi mp YZ

2. Chieu chuyen ong G02G03

Cung chieu kim ong ho CWNgc chieu kim ong ho CCW

3. Toa o iem cuoi XP; YP;ZP -Toa o iem cuoi theo he toa o gia cong (G90)- Khoang cach iem cuoi so vi iem au (G91)

4. Toa o tam hoac banknh

Ii,Jj,KkRr

- Khoang cach tam so vi iem au- Ban knh cung tron

X

Y

Z

G19G02

G17G02

G18G02

X

Y

Z

G19G03

G17G03

G18G03



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+ Phng phap IJK:Tam cung tron c xac nh bi vec t (I,j,k) so vi iem au cung tron.Hnh 4.13

Hnh 4.13. Phng phap I,J,KAp dung : S dung phng phap IJK lap quy ao chay dao theo hnh ve sau:

+ Phng phap R:Lap trnh theo ban knh cung tron, Bai toan xac nh tam co 2 nghiem:Nghiem 1: (0Nghiem 2: (>1800) s dung R


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Th du: s dung phng phap R lap trnh ng chay dao theo cung tron.

Chng trnh gia cong co noi dung nh sau:N50 G90 G00 X-2. Y1.;N55 G01 X0Y0 F8.;N60 Y4.0;N65 G02 X2.Y6. R2.0;N70 G01 X8.0;N75 G02 X9.0Y2.268 R2.0;N80 G01 X0Y0;

N85 G00 X-2.0Y-1.0;d. Noi suy ng xoan oc:e thc hien ng xoan oc, ta khai bao ay u t kch thc IP : XxYyZz trong lenh noi suycung tron. Dao thc hien chuyen ong noi suy tren mat phang ch th va noi suy ng thangtheo truc th 3.

Bai tap ve cac lenh di chuyen dao.



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4.6.2. Lenh toa o va kch thc

a. Khai bao lenh kch thc s dung t kch thc (IP): X_; Y_; Z_, la lenh hnh thc.b. Toa o tuyet oi va toa o tng oi (G90,G91):La lenh hnh thc (modal)ieu khien so s dung hai phng phap o toa o:- Tuyet oi G90:(ABS: absolute).

Dao chuyen ong ti iem ch th xac nh bang gia tr tuyet oi so vi iem chuan- Tng oi G91: (INC: incremental).

V tr hien tai cua dao c xem la iem chuan cho chuyen ong ke tiep. Toa o iem ti tnht khoang cach iem trc o.

V du s dung ABS va INC:

Di chuyen t A en B: ABS G90G00 X60.0 Y60.0;INC G91G00 X40.0 Y40.0;Di chuyen t B en A: ABS G90 X20.0 Y20.0;

INC G91 X-40.0 Y-40.0;Khi ta s dung cung luc 2 lenh G90 va G91, s khac biet the hien hnh 4.15:

Hnh 4.15. S khac nhau gia G91 va G90.

Ban chon ABS mode hay INC mode la phu thuoc vao s thuan tien khi lap trnh cho chnhban.

c. He Inch va he Met (G20, G21):Lenh hnh thc (modal)- G20: Chon he inch. Cung can nhac lai la trong he inch dung cac n v sau ay:



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+ n v dai inch+ lng tien dao: inch/vong hoac inch/phut+ Toc o cat: feet/phut- G21: a n v he met+ n v dai mm+ lng tien dao: mm/vong hoac mm/phut+ Toc o cat: m/phut

Moi he ieu khien co he n v mac nh. Mot so he ieu khien s dung he mac nh la he sdung trc o.Lu y:

Khai bao lenh nay phan au chng trnh.

Khong nen s dung ca hai lenh tren trong cung mot chng trnh.d. Lenh he truc toa oV tr cua dao se c xac nh da tren he toa o. Co 3 loai he toa o c s dung tren mayCNC khi lap trnh:(1) He toa o may (Machine coordinate system)(2) He toa o gia cong (Workpiece coordinate system)(3) He toa o cuc bo ( Local coordinate system)

+ He toa o may (Machine coordinate system)

- Nh ta a biet trong phan trc, moi may co mot iem xac nh la iem khong (zero point),thng no la iem tham chieu th nhat. Cai at iem khong cua may c thc hien bi nha sanxuat. He toa o lay iem khong lam goc c goi la he toa o may- He toa o may c thiet lap khi tr ve iem tham chieu, gi cho en khi tat may. Khi lap

trnh muon s dung he toa o may ta dung lenh (G53):- La lenh mot lan (one shot, non-modal): ch tac dung tren cau lenh.Lenh G53 khong anh

hng he toa o gia cong a c thiet lap.- Cau truc G53 x_y_z_; vi: x_y_z_; tnh theo toa o tuyet oi.- Trc khi s dung G53, moi phep bu phai b huy bo,- G53 ch s dung vi G90

V du ve he toa o may

en v tr iem P1: G90 G53 G00 X-340.0Y-210.0;



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en v tr iem P2: G90 G53 G00 X-570.0Y-340.0;

+ He toa o gia cong (work coordinate system)La he toa o gan lien vi chi tiet gia cong. He toa o nay thng c s dung khi lap trnh giacong nen goi la he toa o gia cong. e xac nh he toa o gia cong co 2 cach sau.

(1) Dung lenh G92- La Lenh hnh thc (modal)- Cau truc: G92 XxYyZz;x,y,z la toa o hien thi cua dao so vi he toa o can cai at.- Muc ch :* e cai at he toa o gia cong.

* Bu tr s khac biet gia he toa o lap trnh va he toa o gia congv du.G92 X50Y60

Hnh 4.16. V du ve G92

(2) Dung lenh G54-59:Khi chng trnh yeu cau s dung nhieu he toa o, viec thay oi gia tr toa o tr nen phc tap.Phan ln cac he ieu khien CNC eu co kha nang xac lap cung mot luc nhieu he toa o lamviecbang viec s dung lenh toa o G54-G59. Viec s dung G54-G59 co rat nhieu u iem so viG92 (se trnh bay sau), do vay khi lap trnh gia cong a so ta s dung G54-> G59 thay cho G92.- La lenh hnh thc (modal)- Xac nh cung luc c toi a 6 he toa o t G54 -> G59V du: Ga 2 phoi tren len ban may

Hai chi tiet tren co the c gia cong lien tuc vi 1 chng trnh:O0001;G90 G54 G00 X0Y0; Lam viec vi chi tiet ch nhatG90 G55 G00 X0Y0;

V tr hien tai cua dung cu

Toa o gia cong can cai at 60

50



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Lam viec vi chi tiet hnh elipseM30;

Cai at G54 -> G59:Neu trong chng trnh s dung G54-> G59, trc khi thc thi chng trnh ta phai cai atv tr cua G54-> G59 vao bo nh may. Trnh t cac bc cai at G54 nh sau.

- Ga at chi tiet gia cong len ban may.- nh tam chuan (x,y) cua chi tiet so vi iem khong cua he toa o may. Khi khong can

chnh xac ta co the di chuyen dao en v tr mong muon bang che o Jog Feed hoacManual Handle Feed roi quan sat bang mat. Khi can chnh xac ta phai dung cac thiet bdo c kh hoac quang hoc e xac nh v tr toa o can cai at.

- a gia tr nay vao bo nh he ieu khien (man hnh work offset). e vao man hnh naythong thng ta chon Setting>Offset > WORK > G54 - G59 =>

- nh tam chuan (z) cua chi tiet so vi iem khong cua he toa o may: di chuyen spindleen v tr mong muon theo phng z. e am bao o chnh xac ta khong cho dao tiep xuctruc tiep vi phoi ma dung c o (Block gauge). Toa o z a vao man hnh offset se la

toa o hien tai tr i kch thc cua c o. hnh di, nh cua workpiece c ch nhla Z=0.

- a gia tr Z1 nay vao bo nh he ieu khien (man hnh work offset)



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Khi G54 c ch nh, chng trnh se s dung tam cua workpiece lam iem chuan giacong.Vd:O0001;G90 G54 G00 X0Y0;..M30;

Khi lap trnh, phai nh xac nh la chon G54-G59. Mot so he ieu khien mac nhG54.

So sanh gia G92 va G54 - 59G92 G54-59

Cach cai at Bang chng trnhBang che o MDI

Bang man hnh work offset screen

u n gian, de cai atThch hp vi he ieu hanh cu

Khong mat khi ngat nguon ienCo the s dung vi he tao o cuc bo G52

Nhc iem Se mat khi ngat ien hoac trve iem tham chieu

+ He Toa o cuc bo G52 (modal)e tien li khi lap trnh oi khi ta can phai di toa o lam viec en v tr nao o, trong trnghp nay ta dung lenh di truc toa o G52, he toa o gia cong khi c di en toa o mi goi lahe toa o cuc bo.Lu y: Gia tr toa o gia cong G54, G55 khong thay oi khi dung G52 ma ch tam thi di env tr mi.Cau lenh : (G54, G55,) G52 x_y_z_Bo G52 bang cau lenh sau: G52x0y0z0.Vdu.

G54

60

50

G54G90(G54) G52 X60Y50; (sau cau lenh nayG54 tam thi di t P1-> P2)..(Gia cong theo toa o P2)G00x0y0 (a dao ve goc P2)G52 X0Y0 (chuyen G54 ve lai P1)G00x0y0 (a dao ve lai goc P1)



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4.6.3. Mat phang gia cong (G17,G18,G19): La lenh Modal

Co 3 mat phang gia cong chnh:XY,ZX,YZG17:mat phang XY c nhn t chieu Z+en Z-

Hnh 4.18. Mat phang G17 va quy nh chieuG18: mat phang ZX c nhn t chieu Y+en Y-

Hnh.4.19. Mat phang gia cong G18G19: mat phang YZ c nhn t chieu X+en X-

Hnh 4.20. Mat phang gia cong G19

Y

Y

X

Z

X

Z



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4.6.4. Lenh tr ve iem tham chieu (G28,G29,G30):

Ngoai thao tac tr ve iem tham chieu bang tay, trong chng trnh khi can thiet (thay dao, ketthuc chng trnh) ta co the dung G28, G29 hoac G30. G28,G29,G30 la lenh thc hien trongmot cau lenh (One shot)

* G28: Lenh G28 ch th chay dao nhanh t iem hien thi ti iem trung gian va sau o tr veiemtham chieu th nhat.- Tr ve iem tham chieu theo 1 truc: G28 Zz;- Tr ve iem tham chieu theo hai truc: G28 XxYy;- Tr ve iem tham chieu theo 3 truc: G28 XxYyZz;iem trung gian chon bat k. Thng la mot iem an toan nao o.

Hnh 4.21. Lenh tr ve iem tham chieuLu y: G28 thng s dung vi mode G91

G28 lam dao di chuyen nhanh bat chap che o trc o.Vd: G91 G28 Z0 :rut thang dao ve iem tham chieu theo phng z; G91 G28 X0Y0 : tr veiem tham chieu theo phng XY.*G29: Lenh G29 ch th thc hien chay dao nhanh t iem goc may ti iem trung gian va sauo en iem X_Y_Z_.- Cau truc G29 X_Y_Z_.;

- G29 s dung iem trung gian a c nh ngha bi G28, do o G29 s dung sau G28.Th du:N45 G01 X2.0Y2.0;N50 G90 G28 X2.0Y10.5;N55 T2M6;N70 G29 X1.0Y3.0;...+ G30:Dung e tr ve iem tham chieu th 2,3,4



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Cau truc G30 Pp X_Y_Z_.;;Khi Pp = 2 -> tr ve iem tham chieu th 2;Tng t cho Pp =3 hay Pp =4;X_Y_Z_.;: ch iem trung gianv du: rut dao thang ve iem tham chieu th 2G91G30P2x0y0z0.

4.6.5. Lenh chon va thay dao

* Lenh:TxM06:- Tx : nh ngha dao so hieu x can thay. Vd: T1 (chon dao so 1)- M06: lenh thay dao

- Phan ln cac may CNC yeu cau thoat dao theo phng Z trc khi thay dao;- Lenh T chon dao nhng khong thay dao, do o phai dung vi lenh M06.- Can bu tr chieu dai dao do moi dao co chieu dai khac nhau.

4.6.6. Lenh tam dng chng trnh (M00, M01)- M00: khi dung M00, chng trnh se tam dng cho en khi nut c nhan.- M01: khi dung M01, chng trnh se tam dng chi khi nut Optional Stop c chon.

4.6.7. Lenh ket thuc chng trnh (M02, M30).

- M30: Ket thuc chng trnh va quay lai au chng trnh( thng dung)- M02: Ket thuc chng trnh nhng khong quay lai au chng trnh

4.6.8. Lenh cung cap chat lam nguoi (M07, M08, M09):

- M07: khi ong ti nguoi (Flood); M08: Khi ong che o phun sng (Misty)- M09: Tat che o ti nguoi

4.6.9. Lenh tam dng di chuyen truc chnh G04Pp

Dung e tam thi dng di chuyen truc chnh trong khoang thi gian p micro giay.Vd:G01z-5F100G04p200G01z10

4.6.10. Lenh lap lai mot khoi lenh LLLenh nay dung e lap lai mot khoi lenh L lan. V du: G91G01X100F100G04P200L3



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4.7. Bu tr trong cong nghe phay (Tool Compensation)

4.7.1. Bu tr ban knh+ The nao la bu tr ban knh?ieu khien so yeu cau lap trnh theo toa o tam dao (tool center coordinate) nhng khi gia congchi tiet s dung iem bien dao cat. do vay neu lap trnh theo kch thc tren ban ve th phaidch chnh dao i mot oan bang ban knh dao. Phep dch chnh tren goi la bu tr ban knh(radius compensation).

Lap trnh bu tr ban knh c thc hien bi lenh G41, G42.Huy bu tr dung lenh G40.

+ ng dung cua bu tr ban knh.- Dao gia cong khac dao lap trnh. Thay v viet lai chng trnh, ngi van hanh ch can thay oi

gia tr bu tr.- Phai thay dao gay va khong co dao tng t nh a lap trnh.- S thay oi kch thc do dao b mon, hoac mai va sa lai.- Thc hien gia cong tho va tinh cho cung mot chng trnh.

+ Cach dung G41,G42, G40.

+ Cau truc lenh G41, G42, G40:



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Lu y:- Phai xac nh mat phang gia cong trc khi thc hien bu- Lenh khi ong bu tr G41,G42 va ket thuc bu tr G40 phai dung vi lenh G00,G01. khongdung vi G02,G03.- Lng bu tr c xac nh bi a ch D va c cai vao bo nh may (offset) trc khi sdung

+ Down cut (thuan) va Up cut (nghch):Khi thc hien bu tr, tuy theo hng bu tr va tuy theo chieu chay dao ma co the gay ra up cuthoac down cut. Hnh 4.22

Hnh 4.22. Up cut va Downcut

Vi may cong cu, thng ta s dung up cut nham tang tuoi tho dao, giam va ap. Tuynhien down cut t gay ra hien tng trt nen nang suat va o bong cao hn thng dunggia cong tinh va gia cong vat lieu mem.

+ V du:Dao di chuyen t iem 0,theo chieu CWbu dao ra ngoai (down cut), roi tr ve

iem 0 vi F100.O0002;N1 G90G54G17G00X0Y0S1000M03;N2 G41 X20.0Y10.0D01;N3 G01 Y50.0 F100.0;N4 X50.0;N5 Y20.0;N6 X10.0;N7 G40 G00 X0Y0 M05;N8 M30;.

10

10

20

30

40

50

20 30 40 50

Y

10

10

20

30

40

50

20 30 40 50

Y

10

10

20

30

40

50

20 30 40 50

Y

Down cut

Up cut

b

a

d

c



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-> Khi N3 c thc hien, cac ng a,b, c, d c tnh dch so vi ng lap trnh mot kngbu.+ Che o bu tr (Offset mode:)- che o bu tr, sau khi khi ong bu tr, o bu se ap dung cho G01, G02, G03, va G00.- Thong thng, hai block ke tiep se c oc nham xac nh vec t bu tr tc thi.- Lng bu tr c tnh theo phng vuong goc vi ng di chuyen cua dung cu.

+ Cat lem khi bu tr (Overcutting:)Overcutting xay ra khi may khong hieu hng di chuyen tiep theo.Thng la khi oc 2 cau lenhtiep theo ma khong co lenh nao lien quan en chuyen ong cua dung cu trong mat phang giacong. Trong trng hp nay mot so he ieu hanh se bao loi ve bu tr. Mot so he ieu hanh khacvan thc hien, nhng lng bu tr se c tnh theo phng vuong goc vi lenh di chuyen trc

o. ieu nay thng gay ra Overcuting (hnh 4.23)O0002;N1 G90G54G17G00X0Y01000M03;N2 Z100.0;N3 G41 X20.0Y10.0D01;N4 Z2.0;N5 G01 Z-10.0 F100.0;N6 Y50.0 F200;N7 X50.0;N8 Y20.0;

N9 X10.0;N10 G00 Z100.0;N11 G40 X0Y0 M05;N12 M30;.

+Ngan nga Overcutting:e ngan nga Overcutting khi lap trnh ta tranh trng hp trong 2 khoi lenh lien tiep nhaukhong cha lenh ve di chuyen dao trong mat phang gia cong. Sau ay la v du ve cac bien phapngan nga Overcutting cho v du trenO0002;

N1 G90 G54 G17 G00 X0Y0 S1000 M03;N2 Z100.0;N3 X20.0;N4 Z5.0;N5 G01 Z-10.0 F200;N6 G41 Y10.0 D01 ;N7 Y50.0 F100.0;N8 X50.0;N9 Y20.0;

N10 X10.0;

Hnh 4.23. Overcuting



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N11 G00 Z100.0;N12 G40 X0Y0 M05;N13 M30;.Hoac.

O0002;N1 G90 G54 G17 G00 X0Y0 S1000 M03;N2 Z100.0;N3 G41 X20.0Y10.0 D01;N4 Z-10.0; --------------------------V tr an toan (G00)N5 G01 Y50.0 F100;N8 X50.0;

N9 Y20.0;N10 X10.0;N11 G00 Z100.0;N12 G40 X0Y0 M05;N13 M30;.

4.7.2. Bu tr chieu dai dao

+ The nao la bu tr chieu dai dao?La phep hieu chnh theo phng truc z e kh s khac biet gia chieu dai dao thc te va chieudai dao lap trnh.Hnh 4.24

Hnh 4.24. Bu tr chieu dai

+ ng dung cua bu tr chieu dai dao.- Dung nhieu dao trong mot chng trnh, ta cai at toa o gia cong (G54) cho mot dao nao o,cac dao con lai phai dung bu tr chieu dai.- Cat nhieu lp khac nhau vi cung mot chng trnh. Luc nay ta dung lng bu tr dao e nhchieu sau cat cho cac lp.



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+ Lenh s dung bu tr chieu dai (modal):G43:bu tr dng. Khi s dung G43, gia tr bu tr xac nh bi ma H_ se c cong vao gia trtoa o ch nh bi cau lenh trong chng trnh.Tc la dao c nang len theo chieu dng motoan xac nh bi H_. vay G43 dung khi dao thc te dai hn dao lap trnh(dao cai at toa o).V du:Khi H1 set 20.0; H2 set 30.0Cau lenh:G90 G43 Z100.0 H1 ; Z se di chuyen en 120.0G90 G43 Z100.0 H2 ; Z se di chuyen en 130.0G44: bu tr theo chieu amKhi s dung G44, gia tr bu tr xac nh bi ma H se b tr bi gia tr toa o ch nh bi caulenh trong chng trnh. Tc la dao c ha thap theo chieu am mot oan xac nh bi H_. vay

G44 dung khi dao thc te ngan hn dao lap trnh(dao cai at toa o).V du:H1 set 20.0; H2 set 30.0G90 G44 Z100.0 H1 ; Z se di chuyen en 80.0G90 G44 Z100.0 H2 ; Z se di chuyen en 70.0G49 :huy bu tr chieu daiTuy nhien ta cung co the s dung H00 e huy bu chieu dai. H00 luon co y ngha la 0.

Lu y: ta co the dung G43 vi lng bu tr am, e thay cho G44 (thng dung trong lap trnhbang CAD/CAM)

4.7.3. Cai at lng bu tr.

e cai at lng bu tr vao bo nh cua may, ta chon che o Sau o chon tiep hoac Luc nay ta vao man hnh Offset.Khai baolng bu tr vao cacvung offset mong muon. Hnh 4.25

Hnh 4.25. T

Giáo Trình Máy CNC Và Công Nghệ Gia Công Trên Máy CNC

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