Nghiên cứu ảnh hưởng của các thông số công nghệ đến độ chính xác gia công trên máy phay CNC theo phương pháp thiết kế thực nghiệm

^ M ^' ^ ^ ^ ^ ^ CHINH XAC GIA CONG TREN MAY PHAY CNC \ ^ J THEO PHU'ONG PHAP THIET KE THU'C NGHIEM RESEARCH THE EFFECTS OF TECHNOLOGICAL PARAMETERS TO ACCURACY IN PROCESSING THE CNC M

^ M ^' ^ ^ ^ ^ ^ CHINH XAC GIA CONG TREN MAY PHAY CNC

\ ^ J 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^

1 Truong Dgi hgc Supham Ky thugt Hung Yin

2 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 ra sdn phdm chdt lugng eao voi ehi phi thdp cho cdc nhd sdn xudt Kit qud nghien euu cho

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 khi gia edng tren mdy phay CNC Do 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

1 Mddiiu

Viec nghien cuu quy luat phan bo kich

thudc va anh hudng eac thong s6 eong nghe dgn

do 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 nay 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 nay trong ITnh vuc

che tao may

Qua nghien euu nit ra nhiing van dg co tinh

quy luat, kiem chiing tren thue te Tir do, xay dung

thu vien che do eong nghe gia cong cho qua trinh

ling dung, nham toi uu cac thong so cong nghe cong

nghe trong pham vi khao sat

2 Cff sd phuwng phap nghien cmi dd chinh xac

gia cong

2.1 Phu-omg phap xac s u i t thdng ke | 4 |

Gia cong loat thii tir 50 ^ 100 chi tilt trong

mpt lan dieu chinh may Do kich thudc thuc cua

timg ehi tiet trong ca loat, xac dinh gia tri gidi ban

ldn nhat, nho nhat Chia khoang gidi han tir ldn

nhat den nho nhat do thanh mpt s6 khoang ( > 6)

Xac dinh so lugng chi tiet cd kieh thudc n i m trong

moi khoang va xay dung dudng eong phan bd kich

thudc thuc nghiem, ed true hoanh la kieh thudc dat

duge, cdn true tung la tan suat ciia cac kich thudc xuat hien trong moi mpt khoang Qua nghien cihi thay rang, kieh thude phSn b6 ciia ca loat chi tilt

trong 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 l a , b)

Tan suat ^R'

Hinh la Dirang cong phdn bo thuc

Hinh lb Dudng cong phdn bd kich thude chudn

Gauss

Gauss CO dang:

{JV27t

Trong do:

e - Co so eua logarit tu nhien

0 - Sai lech binh phuang trung binh

N

Vdi: X | - d j - d ^

X = d, - d"

Nhu vay, muon biet gid tri ciia 0 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)

Gia tn cua ham <l>(z) va 2 0 ( z ) duge

tinh sin trong bang ham Laplace [4] Tir bang nay

thay ring, khi z = — — 3 , tiic la x — 3 o , thi ham

2 * ( z ) = 0 , 9 9 7 3 , trong k p t h u a t c o t h l coi bang 1

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^) trong khoang -3 0 -^ +3 0(khoang 6 a)

b i n g l ("hoac 100%)

2.2 Phu-ong phap quy hoach thirc nghifm [2]

Phuang trinh hdi quy (mo hinh toan hgc)

n h ^ dugc b i n g phuong phap quy hoach thuc

nghiem co the diing de xac dinh cac thong so dau

vao toi uu khi muon dat thong so dau ra cue trj (Idn

nhit hoae nhd nhat)

2.2.1 Phircmg phap quy hoach trvc giao cap I

- 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:

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 khi chi con 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'"

Trong dd:

2j — Z, + /I, _ Miic tren (miic cao);

Z™" — 7J]~ A- Miic dudi (mue thap);

1 = 111 til - Khoang bien thien theo

true Z

- Biin khong thii nguyen x :

Ma hoa dugc thuc hien nhd viee chgn tam

Zj ciia mien nghien cdu lam goc he true tga do

_ z r ' - Z?

" /ll

_ Zj - z?

j = l,2, ,k

- Xay dung ma tran thuc nghiem' + s 6 thi nghiem xae djnh theo cong thirc N = 2'', cot Xp luon bang 1

+ 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 trong phinrag trinh

hoi qui

Tinh y nghTa ciia cac he so b dugc kiem dinh theo chuin Student (t) xac dinh nhu sau:

tj =

Trong do:

b - He s6 thli j trong phuang trinh h6i qui

S^ - Sai lech binh phuang trung binh ciia he

s o /

3 XSy dyng bai toan nghien cihi \h thirc nghiSm

3.L B^i toan nghiSn cihi

1/ Nghien ciiu quy luat phan b6 kich thude

chi tilt eiia loat gia cong thu tren may phay CA^C

khi lira chgn chi dp cdng nghe van toe cat, lugng

chay dao va chieu sau cat t

2/ Nghien euu anh hudng eua viec thay doi

van t6c cit va lugng chay dao den dp ehinh xac kich

thudc chi tilt gia cong tren may phay CNC

3.2 Lira chon gia tri cic thdng so cong nghe

Qua nghien cim vdi muc dich nang cao cong

chinh xac gia cong tren may phay CA'C, cac thong

so eong nghe dugc lua chgn va quy doi nhu sau

[5], [6];

Thong so

cdng nghe

1 Mire cao;

2 Muc trung

binh:

3 Miic thap:

V

(m/min)

81

71

61

S (mm/vong)

0.45

0.3

0.15

t (mm) 1,0 0,6 0.2

3.3 Thuc nghiem

- Vat lieu phoi: thep cacbon C45

- Kich thudc ehi tiet: h = 19* ' '' mm

- Sir dung may phay 3 true CA'C - DMC635V

do Hang DECKEL MAHO Cgng Hda Lien Bang

Dire chi tao, he dieu hanh FANUC32i

3.3.1 Thilt ke thuc nghiem nghiSn ciru quy luat

phan bo kich thirdc

Trong qua trinh thuc nghiem se khong thay

doi gia tri cac thdng so cdng nghe doi vdi loat eac

mau gia cong

- Van tde cit: V - 71.0 m/phiit;

- Lugng chay dao' S = 0.3 mm/v;

- 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'^

thudc gdm 2 yiu tl la van tde eat va ehieu sau cat:

k = 2 S6 thuc nghidm t^i tam:

N„ = 3 Suy ra, tong sd thuc nghiem:

N i = N , + N„=4H-3-7

- Muc CO ban:

O day chgn' V^,^ = 61 m/ph; S^,„ = 0,15 mm/v6ng; t_^,^ -0,2 mm

V^^ = 81 m/ph; S ^ = 0,45 mm/vdng; t^^

= 1,0 mm

Suyra:Vf = 71m/ph; S? ^ 0.3 mm/vdng;

t° = 0.6 mm

- Khoang bien thien:

Al ^ 10 m/ph ; A^i = 0.15 m r a / v o n g ; A\ = 0.4 mm

- Cac biin khdng thit nguyen:

+ Bien khong thir nguyen van toe:

^ v „ ^ j ; x r " " = - l ; x : - = 0 + Biln khdng thu nguyen lugng chay dao:

7.]-'=V' x f " ' ' - l ; x f = 0

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

b - he sd tuyen tinh

b - he so tuong tac cap

Suy ra, ma trSn thi nghiem vdi k = 2 va 3 thuc nghiem tai tam phuang an vdi cac thdng so dau vao (V, S) va cac bien ma hda la X^, X, v^ X^ dugc chi dan tren bang 1

Trong do:

Xg- bien ao dugc dua them vao ma tran; X^ - bien ma hoa iing vdi van toe cat;

Xj - bien ma hoa iing vdi lugng chay dao Bang 1

TT

1

2

3

4

5

6

7

X X, -1

1 -1

1

0

0

0

X, -1 -1

1

1

0

0

0

x,.x

1 -1 -1

1

0

0

0

V

61

81

61

SI

71

7/

71

S

0.15

0.15

0.45

0.45 0.3

03

0.3

phay tinh t^ 0.2 mm

3.3.3 Lira chgn phuang phap, dyng cu do

- Phuang phap do: do kich thude theo

phuang phap tuyet d6i va true tilp

- Dung cu do: Pamne chi thj s6, co bg phan

ghi ket qua do ciia Hang Mitutoyo (Nhat ban);

Pham vi do: 0 ^ 25 mm; Do chinh xae 0,001 mm

gia tri eua khoang chia:

_ 45

= 9tim

T u bang 2 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) n i m trong cac

khoang chia Qua tinh toan va bing phin m i m Mi-crosoft 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<^ thuyet

Hinh 2b Chi tiet sau khi phay tinh

Sai leeh so vdi kich thudc danh nghia eiia

ehi tiet dugc chi dan trong bang 2

3.4 Quy luat phdn b6 kich thirdc mau gia cong

Theo so lieu trong bang 2, thay ring:

x^,^ = -0,033 va x^^ - 0,012

Khoang phan tan ciia kich thudc: x - x

= 0 , 0 1 2 - ( - 0 , 0 3 3 ) - 0 , 0 4 5 m m - 4 " ^

Hinh 3 Duong cong phdn bd ly thuyet ciia quy ludt phdn bo chudn

3.5 Anh h u ^ g cua cac thong s i cong nghe d i n

do chinh xac gia cong

3.S.I Ket qua do kich thu&c

- Gia trj sai lech cae ehi tiet theo ma tran

thue nghiem va sai lech trung binh so vdi kich thudc danh nghTa dugc chi dan trong bang 3

-0.02

-0.012

-0.002

0 009

-0.018

-0.017

-0.003

-0.001

-0.015

-0.025

-0.002

-0.004

-0.004

-0.008

0.001

0.009

-0.012 -0.013 -0.004 0.003

Bang 2

-0.033 -0.017 0.007 0.001

Ba

•0.013 0.012 0.008 0.012

n g 3

-0.022 -0.011 0.008 0.012

•0.027 -0.017 -0.008 -0.005

-0.026 -0.024 -0.005 -0.004

-0.031 -0.022 -0.008 0.003

-0.031 -0.027 -0.011 0.002

TT

1

2

3

4

5

6

7

y,:

-13

-21

•15

-23

-3

-3

-15

J B

-16

-35

-19

-27

-5

-5

-19

Jo

•22

-8

•29

-41

•19

-19

•29

y^

-21

-28

-11

-28

-7

-7

-11

y«

•12 -31 -1 -8 -17

•17 -1

?«

-14 -24 -22 -8 -25 -25 -22

yiT

13 -17 -3

•2 -1 -1 -3

y«

14 -14

•15 -12 -11 -4 -15

yt,

-7 -19

•23 -20

-4

-4 -23

yiia

18 -9

6

6

9

9

6

y,u

15

8 -1

4

3

3 -1

im

5 -4 -3

•6

4

4

-3

T h o n g

so ra

- 10

- 17

- 4

- 1 5 -6 -6

- 4

- Vdi ham h i i quy cip 1 tuyen tinh da chpn

CO dang:

Y = b ^ -1- b | X , + bjX, + b | j X , X j

Suy ra, dang cua phuang trinh hoi quy can

tim

Y = bo + b i X , + b3.X3 + bi2.X,.X2

- Theo phuong phap bmh phucmg nhd nhat,

cae he s6 b trong phuang trinh hoi quy eua quy

hoach true giao c i p I tuang iing vdi k = 2 yeu to

anh hudng eo gia tn nhu sau:

( b o — 8 , 8

l b , — 3 , 2

b 2 - 2

[ b i 2 = - 0 , 4

Phuang trinh hdi quy eo dang:

Y — 8,8 - 3,2.Xi + 2.X2 + 0,4 X,.X2

Sau khi kilm tra y nghTa cua cac he b trong

phuang trinh h i i qui theo phuong an thuc nghiem

t?i tam va y nghTa ciia eac he sd b dugc kiem dinh

theo chuin Student (t) Suy ra, cac he so b co y

ng-hTa va dlu duge giir lai trong phuong trinh hoi quy

- Kiem tra su tucmg thich ciia phuang trinh

hdi quy vdi thuc nghiem theo bang gia tn gidi han

cua chi tieu Fissher F

Stn' = 7,123

F(0,95)(f,,f,) = F(0,05)(8,2) = 8,89

F < F||^, phuang trinh hoi quy tim dugc la

tuang thich vdi thuc nghiem vdi mue y nghTa 95%

- Kiem tra su dong nhat cua cac phuang sai

theo bang gia tri gidi han ciia ehi tieu Cochoren,

G - - 2 ^ = 0,302

Suy ra, G^ < G,,

3.6 Do thi thirc nghidm

Su dung phan mem Microsoft Excel - 2007

d l tinh toan va p h i n mem Tableeurve 3D V4.0.0.1

de ve bieu dd quan he cua van tde cat V, lugng chay dao S d i n do chinh xac gia cong hinh (4)

4 K i t qua thyc nghif m v^ d^nh gia k i t qua ng-hien ciru

Tii k i t qi^a nghien cuu thay rang:

1 v l phuang an edng nghe da ehgn dam bao

do ehinh xac gia cong:

x™"= 0,012 nm

2 Vdi phuang an edng nghe dS ehgn theo

ma tran thue nghiem, tir dd thi (hinh 4) suy ra:

- V = 81 (m/phut); S = 0,15 (mm/v6ng): sai lech ldn nhit (-13,6 |jm) - Vung m i u da cam

- V = 81 (m/phiit); S = 0,45 (mm/vdng): sai lech (-10,4 |im) - Vung mau xanh la ma

- V = 71 (m/phiit); S - 0,3 (mm/vdng): sai lech (-8,8 |im) - Viing mau xanh la m^

- V = 61 (m/phiit); S = 0,15 (mm/vdng): sai lech (-8,0 nm) - Vimg mau xanh nudc bien

- V = 61 (m/phiit); S = 0,45 (mm/v6ng): sai

lech nho nhit (-3,2 \xm) - Vimg mau tim

Do do, theo phuang phap thiet ke thuc

ng-hiem (DOE) sir dung ham hdi quy nhieu bien, xac

dinh dugc bg thdng so cong nghe tdi uu cue bp (trong pham vi khao sat) ed sai leeh kich thudc nho nhat nhu sau:

- Van t i e cit: V = 61 (m/phut)

- Lugng chay dao: S = 0,45 mm/vong

- Chieu sau c a t ' t = 0,2 tnm

Ss.^

Hinh 4 Anh hudng ciia van toe cat vd lirgng chgy dao den dp chinh xdc kich thuoc

[I] Tran Van Dich, Nghien cuu do chinh xdc gia cdng bdng thue nghiim, Nha xuit ban khoa hoc

va ky thuat Ha Npi 2003

[2] Nguyin Trpng Hung, Thiit ki thuc nghiem trong chi tao mdy, Trudng Dai hoc Su pham ky thuat

Hung Yen, Hung Yen 2013

[3] Nguyen Van Phu, Nghiin ciru phucmg phdp diiu ehinh cdc thong sd cdng nghe di dam bda dp chinh xdc kich thirdc chi tiet gia eong trin mdy phay CNC, Luan van Thac sy ky thuat, Trudng Dai

hgc Su pham ky thuat Hung Yen, Hung Yen 2013

[4] Ninh Diic T i n , Nguyin Trpng Hung, Ky thugt do Tap I - Dung sai ldp ghep vd Tieu chudn hoa,

Nha xuat ban Giao due Viet Nam, Ha Npi 2006

[5] Lulzim Bala', A&im Gjelaj', Avdyl Bunjaku^ and Avdi Salihu', Surface Roughness of Material Processing during Milling Process, Journal of Mechanics Engmeermg and Automation 2 (2012)

601-605

[6] Nitm Agarwal, Surface Roughness Modeling with Machining Parameters (Speed, Feed & Depth

of Cut) in CNC Milling, MIT Intemational Joumal of Mechanical Engineenng, Vol 2, No lU, Jan

2012, pp (55-61)

Abstract:

This article presents a research method the effects of the technological parameters to accuracy in processing the CNC milling machine by design of experiments (DOE) method, which reduces the number

of experiments, produces high quality products with low cost for manufacturers Results of research for the distribution law of processing details 'size and relations between the deviation of processing size and technological parameters including cutting speed and feed intake ranging and determine the local optimum technological parameters (within the survey) with minimum size deviations when processing on CNC mill-ing machines Therefore, the accuracy and productivity in processmill-ing are improved

Keywords: Effect factors of technology Precision processing Design of experiments (DOE), Cutting veloc-ity Flow range CNC milling machine

Ngudi phan bi^n: PGS.TS Khong Doan Dien