NGHIEN CUfU - TRAO D O I
NGHIEN Cl/U ANH HUd-NG CUA CH^ 0 0 CONG NGHE DEN CHAT LU'ONG B t MAT KHI GIA CONG
THEP HOP KIM TREN MAY CAT DAY
CUTTING CONDITION'S RESEARCH AFFECTED COME TO GREY IRON SURFACE ROUGHNESS WHEN ABRASION ON SURFACE
GRINDING MACHINE
ThS. Chu Anh Tuan TrUdng Dai hpc Cdng nghiep Ha Ndi
TOM TAT
Bdi bdo cho thay anh hUdng cua che do cong nghe doi vdi den chat liidng be mat vd nang sudt gia cong khi gia cong thep hdp kim tren may cat day Goldsun, dUdc do bang thUc nghiem tren may do do nhdm Mitutoyo. Tren cd sdphdn tich, tong hdp cd sd ly thuyet thi bdi bdo da thiet lap dUdc cong thdc thUc nghiem xdc dinh moi quan he giUa do nhdm be mat, cac yeu to cong nghe khi gia cong. TiC viec sit dung dothivd cac md hinh toan hoc, ta co the danh giddUdc cac yeu to cong nghe dnhhudng den qua trinh gia cdng. Ket qua thu dUdc md ra mot hUdng nghien ci(u khd quan vd khd nang dp dung vao thiic tenhdm nang cao chat lUdng be mat chi tiet khi gia cong tren may cat day noi chung vd thep hdp kim noi rieng.
Tii khoa: Cat day tia liia dien; Thep hdp kim; Chat lUdng be mat.
ABSTRACT
This paper shows the impact of technological regimes for surface quality and processing performance when working on steel alloy wire cutters Golden Sun, the experimentally measured roughness tester Mitutoyo. On the basis of analysis, synthesis, the theoretical basis of the article has established empirical formulas determine the relationship between surface roughness and technological factors when outsourcing. From the use of graphs and mathematical models, we can assess technological factors affecting the machining process. The results open a promising research direction and the ability to apply in practice to improve the quality of surface detail when working on general wire cutters and alloy steel in particular
Keywords: Wire Electrical Discharge Machining; WEDM; Alloy Steel; Surface Quality
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NGHIEN CUfU-TRAO D O I
l . D A T V A N D E
Ngay nay, cung vdi sU phat trien cua khoa hpc va cdng nghe tren tat ca cae linh vUc thi cac san pham cO khi ngay cang ddi hdi chat lUpng cao hon, mUc dp tU dpng hoa san xuat va dac biet la do chinh xac, chat lUpng be mat cua san pham.
Chinh vi vay khi gia cdng bang cac cdng nghe truyen thong tren cac may van nang khd cd the dap Ung cac yeu cau ngay cang cao nay va do do sU canh tranh ciia san pham tren thi trUdng bi han che. ThUc te dd ddi hdi phai phat trien va nghien eUu cac cdng nghe mdi n h i m nang cao dp chinh xac be mat ndi rieng va chat lUpng san pham ndi chung.
Phuong phap gia cdng cat day tia l i a dien va gia cdng xung dien ehi xuat hien each day hon nifa the ky, tuy nhien, cae phUOng phap nay mdi chi dupe ap dung vao san xuat d Viet Nam trong thdi gan day. Mat khac nd phUOng phap gia cdng tien tien nen nhieu nha san xuat chi ban may chU khdng ban cdng nghe.
Xuat phat tU nhUng nhu eau thUe te dd, chung tdi da manh dan tap trung nghien eiiu khao sat mot so anh hUdng cua cac thdng sd cdng nghe cu the d bai bao nay la hai yen td "Thdi gian phdng tia lUa dien va cUdng dp ddng phdng tia lUa dien" doi vdi nang suat va dp nham b^ mat cua ehi tiet gia cdng. De nham dUa ra giai phap nang eao chat lUpng be mat chi tiet. De tai "Nghien cUu anh hudng cua che dp cdng nghe den chat lupng be mat khi gia cdng thep hpp kim tren may eat day Goldsun" cd y nghia thUe tien rat cao. Ngoai y nghia mang tinh khoa hpc, de tai cdn Ung dung phuc vu trUe tiep cho dao tao dac biet la Ung dung vao thUe te san xuat gia cdng tren may cat day tia lUa dien.
2. GIA C O N G CAT D A Y BANG TIA LLTA DIEN VA ANH H l / ^ N G CUA NO DEN CHAT LtfONG BE MAT CHI TIET GIA CONG VA N A N G S U A T G I A CONG
Cat day tia lUa dien (WEDM - Wire Elec- trical Discharge Machining) la phUong phap dimg 1 day dan dien cd dUdng kinh nhd {0,1 - 0,3mm)
cuon lien tuc va chay theo 1 bien dang dinh trUdc de tao thanh mdt vet cat tren phdi. PhUOng phap nay thUdng dung de gia cdng cac 16 thdng suot co bien dang phUe tap nhU cac 15 tren khudn dap, khudn ep, khudn due ap lUc, che tao cac dien c^c dung cho gia cdng xung dinh hinh, gia cdng cac ranh hep, gap khue, cac dUdng kiem,... [1],
1 y^
C o 1 1
2 SiAngdeh 1 Bom 4 fXnQcathwbnn 5H4tti«r>g«gMiltn CNCvilCiatn CCapAfn 7 BMnWY TTxnh 1.1: Sd do nguyen li may cat ddy tia liia dien [2]
2.1. CO che boc tach vat lieu
Khi gia cdng cat day, sU bde tach vit lieu dUa tren hieu Ung an mdn xung dien cua cac tia lUa dien xuat hien giUa hai dien cUc (hinh 1.2).
Cac tia liia dien nay tac dung rieng re nhd chat dien mdi. SU bdc tach vat lieu xuat hien do sii phdng dien tao ra nhiet dp cao lam nong chay va bdc hoi hai dien cUc. Nang lUpng mdt chieu dupe dat vao mot maeh xung vdi dien ap tU 30 den 250 V va tan so 50 den 500KHz tao ra giUa hai dien cUe dat each nhau mdt khoang ngan (thUdng tU0,01 den 0,5 mm) mot xung vudng [Ij.
EDE
I Planu 1
I
DunsoiC-)
1
^
--'\ a t n m o ) Cb) ^ EM «mcHinh 1.2: SU boc tach vat lieu khi gia cong cat d&y [Ij
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NGHIEN CUfU-TRAO Ddi
2.2. Be mat gia cong khi cat day
Trong gia cdng cat day ta cd the d l dang nhan thay cd 2 kieu khe h d phdng dien tdn tai ddng thdi, do la:
' Khe hd phdng dien mat trUdc: La khoang each gifla day va phdi dupe do theo hUdng tien day, ki hieu la g|-
' Khe h d phdng dien mat ben: La khoang each giUa day va phdi do theo chieu vudng gdc vdi hudng tien day, ki hieu la g|^.
Mat ben sau khi gia cdng cd dac diem la khdng ddng deu do vat lieu chay long d khe h d phia trUde, cac hot khi, cac phan tU vat lieu phoi ...bi dinh vao be mat. Dieu nay la mdt phan quan trpng gay ra nham be mat. Gia tri cua dp nham be mat phu thupc rat nhieu vao dp Idn cua ddng dien, neu ddng dien cang Idn thi gay ra dp nham cang Idn tren be mat.
2.3. Dp chinh xac trong qua trinh cat day Dp chinh xac cua gia cdng khi cat day phu thudc vao nhieu thdng sd nhU: Vat lieu gia cdng, hinh dang ket eau, khe hd phdng dien... Gia cdng bang cat day di dang dat dupe dung sai ±0,05 m m [1]-
Sau khi gia cdng be mat gia cdng khdng hoan toan phliig ma nd de lai nhflng nhap nhd, dd chinh la dp nham be mat. Dieu nay lam giam dac tinh chdng mai mdn va tang nguy co bi an mdn hoa hpc [2].
3. KHAO SAT A N H H U ' 6 N G CUA CHE DO CONG NGHE DEN CHAT VJONG BE MAT VA N A N G S U A T KHI GIA CONG THEP HOP KIM TREN M A Y CAT DAY TIA Ll/A DIEN 3.1. Mo hinh dinh tinh qua trinh cat day tia liia dien
a a j MB C K
CbKESttlBbEHCon
"T"
1
•"""1
v.. L u I.
difn
Kich tJjBBs gu seag CbitiiSBaai
£k!sn8<md^giBco()g
Hinh 1.3: Md hinh dinh tinh qua trinh gia cong tia lUa dien [4]
3.2. Dieu kien thUc nghiem 3.2.1. May cat ddy Goldsun
Bang 1. Cac thong so ki thuat may OS 2532B
Kich thudc ban may Hanh trinh ban may Do day gia cong Idn nhat Kich thiidc phoi !dn nhat Do con (nghieng) 16n nhat
Dddng kinh day Toe dp gia cong I6n nhat Do chinh xac gia cong Dong dien gia cong Idn nhat
Kich thdoc bao bi may Trpng liipng tmh
mm mm mm
^S Dp mm mm2/ph
mm A mm
kg
400 X 580 250 X 320 300 200 6°
00,1 - 00,2
<160 0,015 5 1360x1060x1750
1300 kg
Thiet bi sU dung trong thi nghiem la may edt day cd ki hieu GS 2532B cua hang GoldSun san xuat vdi cac thdng sd ki thuat sau (bang 1).
3.2.2. Chi tiet gia cdng
' Vat heu phdi la thep khdng gi 12Crl8Ni9 (tUOng Ung vdi mac thep 12X18H9 cua Nga);
Kich thudc 50 x 50 x 10, loai thep nay la loai pho bien hon ca so vdi cac mac thep eon lai trong hp Austenit vi cd nhflng Uu diem sau:
Cd tinh chdng an mdn cao trong cac moi trUdng an mdn manh nhU axit cac loai nen cd y nghia rat Idn trong cdng nghiep hda hpc (san xuat
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NGHIEN CUfU - TRAO D 6 |
axit, phan hdn, hda dau). Ngoai ra, do nd hoan toan on dinh trong khi quyen nen cung dUpc dung rpng rai lam hang tieu dung (vd dong ho deo tay kep tdc...), dd gia dung (xoong noi, bep...) va trang tri trong xay dUng [3].
Bdng2. Thdnhphdn cac nguyen to hoa hoc thep 12Crl8Ni9 Mac thep
12Crl8Ni9
Thanh phan hoa hoc cac nguyen to, % C
0,12 Cr 17,0 - 19,0
Ni 8,0 - 10,0
Mn 2,0
P 0,035
S 0,02
Hinh 1.3: May do nhdm S] 400 Hinh 1.4: Mdu thep thi nghiem 12Crl8Ni9
3.2.3. Dung cu do
Trinh til do va k^t qua do do nham diicfc thUc hien bang may do dp nham be mat SJ 400 cCia hang Mitutoyo - Nhat Ban va duOc hien thi tren may tinh.
Cac ket qua khac dUOc thilc hien tai phong ThUc hanh - Thi nghiem Gia cong khuon mau, Trung tam Co khi - Viet Han, TrUdng Dai hoc Cong nghiep Ha Noi.
4. TIEN HANH THTjC NGHIEM VA XlT LY SO LI$U
4.1. Cac thong so dau vao cua thi nghiem Muc tieu cua thi nghiem la nghien ciJu anh hiidng cua mot so che dp cong nghe tieu bieu anh hudng den chat liiong be mat chi tiet trong gia cong cat day tia Ifla dien.
va do dp nham be mat v6i 09 phoi, khao sat dUa tren 3 yeu to Co anh hifdng chu yeu tcfi chat liidng be mat chi tiet la: dien ap phong tia lila dien U, do keo dai xung t^, khoang each xung t .
Cu the la moi mau thi nghiem diidc gia cong trong ciing mot che do (vdi cac thong so dieu khien) nhat dinh va n h a nhau. Cac thong so dieu khien se diloc thay doi trong khoang dieu chinh cho phep cua thiet bi va ditpc ghi chep, tinh toan de til do danh gia dUpc anh hildng cua cac yeu td tdi be mat cua chi tiet.
De xac dinh mo hinh toan hoc ve siJ anh hudng, dong thdi cua cac yeu to che dp cSt den dQ nham be mat khi gia cong tren may cjt day CNC cd giong nhu tren cac thiet bi truyen thong hay khong can phai cat thit nghiem.
Ta cd moi quan he giijfa do nham b^ m?l va che dp cat phai tuan theo quy luat ham mii;
Tien hanh thilc nghiem gia cong cit day R = K
(1) TAP CHI C O KHi VIET NAM, S6 4 nam 2014
NGHIEN ClJfU - TRAO DOI
nghiem.
Trong dd:
R^ - la dp nham b^ mat chi tiet;
KR„ - la hang sd;
X, y, z: La so mu tinh den sU anh hUdng cua che dp cat den dp nham be mat, xac dinh bang thUc U - la dien ap danh tia Ifla dien (V);
t^: La dp keo dai xung (s);
t^: La khoang each xung (s).
DUa vao quy hoach thUe nghiem, ta chon mien nghien cUu thUc nghiem la:
U,in^ = 90(V) t , _ = 0,7(s) t, =16(s) U..m = ^0(V) t , _ = 0 , l ( s ) C = 8 ( s ) Cac yeu to x^ thuc nghiem la:
Mflc tren: x^'*' = Inx ^^^;
Mfle dudi: x *''* = Inx^^^^;
Mflc ca sd: x"" = V2 (Inx. i-hix ).
Bang 3- Bang tinh toan Cac yeu t6
IVIifc tren Mcic dudi Miic CO s6 Khoang bien thien
Z, 90 70 80 10
Z, 0,7 0,1 0,4 0,3
Z, 16 8 12 4 4.2. Ket qua thi nghiem va xfl ly so lieu
4.2.1. Do nhdm bematR^
4.2.1.1. Md hinh toan hoc
Gia thiet moi quan he giUa dd nham be mat va che dd edt tuan theo qui luat ham mu. Cd nghia 14:R. = K , . - U , ' . t - . t . - .
Day la mot ham phi tuyen, sti dung phUdng phap tuyen tinh hda ham phi tuyen bang each lay logarit 2 ve ta diipc phiidng trinh mdi:
Ln(R,) = ln(K,.) + x.ln(U) + y l n ( t ) + z.ln(t,).
Dat: y = ln(R ); a„ = ln(K„J; a^ = x; a, = y; n^ = z.
x, = l n ( U ) ; x , = ln(t,);X3 = ln(t„).
Ta diidc phddng trinh mdi nhu sau:
y = a|, + a|.x,+ aj.Xj + aj.Xj
Dang tong quat:y = a„ + a^.x^ + ^^.x^ + + an.xn
(2)
(3) (4) Bai toan trd thanh xac dinh ham so hoi qui thiic nghiem n bien so. Vdi thUc nghiem cd ba bien dau vao, lam thi nghiem vdi n = 2^ = 8 thi nghiem tai cac dinh va ba thi nghiem d trung tam, ta cd bang
quy hoach thvtc nghiem sau (bang 4). ^
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NGHIEN CiHU - TRAO D6\
Bang 4. Bang quy hoach thUc nghiim
Stt 1 2 3 4 5 6 7 8 9 10 11
Bien ma hoa
X j
+1 +1 +1 + 1 0 0 0
X,
+ 1 + 1
+1 + 1 0 0 0
X,
+ 1 + 1 +1 + 1 0 0 0
Bien thUc nghiem U,(v)
70 90 70 90 70 90 70 90 80 80 80
ti(s) 0,1 0,1 0,7 0,7 0,1 0,1 0,7 0,7 0,4 0,4 0,4
l,(s) 8 8 8 8 16 16 16 16 12 12 12 4.2.1.2. Jhuc nghiem do nhdm
Ap dung tinh chat ciia quy hoach trUc giao cap 1 ta tinh dUdc cac he so, ta cd:
a„ = (1/N)y,= 1/8(2,54+2,55+2,56+2,57+2,63+2,95+3,08+3,29) = 2,774.
a, = (1/N)x, y. = l/8(-2,54+2,55-2,56+2,57-2,63+2,95-3,08+3,29) = 0,07.
a^ = {1/N)x, y = l/8(.2,54+2,55+2,56+2,57-2,63-2,95+3,08+3,29) = 0,104.
J; = (1/N)xjy^ = l/8{-2,04-2,05-2,06-2,07+2,13+2,95+3,08+3,29) = 0,217.
Thay vao phUdng trinh y = 2,774 + 0,07X| + 0,104Xj + 0,217x,.
Sau khi xay dung dUdc phuong trinh y, ta tinh phuong sai dii:
S ^ , „ = [ l / n . ( k + l ) ] . ( y , - y _ /
Lan luot thay cac gia tri trong bang 5, ta dupc: S^^,^ = 0,0257 > S'^_ = 0,0065 Bangs
(5)
(6)
Stt 1 2 3 4 5 6 7 8
y.
2,54 2,55 2,56 2,57 2,63 2,95 3,08 3,29
Xj
-1 +1 -1 +1 -1 + 1 -1 +1
X ,
-1 -1 +1 +1 -1 -1 +1 +1
X
-1 -1 -1 -1 +1 +1 +1 +1
a^i 2,774 2,774 2,774 2,774 2,774 2,774 2,774 2,774
a^
0,07 0,07 0,07 0,07 0,07 0,07 0,07 0,07
a^
0,104 0,104 0,104 0,104 0,104 0,104 0,104 0,104
S
0,217 0,217 0,217 0,217 0,217 0,217 0,217 0,217
y
2,382 2,522 2,591 2,731 2,817 2,957 3,026 3,166
(y-y,,)'
0,024 0,008 0,001 0,023 0,032 0,002 0,003 0,017
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NGHIEN CUfU-TRAODOI
F = S^_,/ S\ = (0,0257/0,0065) = 3,9538.
Vdi bac til m^ = n-(k+l) = 4; bac mau n„ -1=2. Ta chpn miSc y nghia la bing 0,05, tra bang Fisher t a d U d c f = 19,2.
F < f, vay mo hinh la phu hpp. Chuyen ve bien Z, td y = 2,774 + 0,07x, + 0,104Xj + 0,217X3 •"" '^ = ^ ^ - Z„)/Z1 thay vao ta dupc y=l,4427 + 0,007Z,+'o,3477Z, + 0,0543Z,
= 4,1691, thay vao ta dupc:
a„ = l n ( K , ) CS> K = e'" = R^ = 4,1691.U »"'.t " ' " " . t , » " « (pm)
Vay phuong trinh (7) la phuong trinh hdi quy thUc nghiem.
(7)
Vdi bai tpan dat ra trong dieu kien tac gia da lap lai thi nghiem 3 lan va do 3 gia tri dd nham, lay gia tri trung binh cua 3 ket qua do, ta dupc ket qua nhu bang 6.
Bang 6
STT 1 2 3 4 5 6 7 8 9 10 11
Bien ma hoa
X j
-1 + 1 -1 + 1 -1 + 1 -1 + 1 0 0 0
==2
-1 +1 +1
+1 +1 0 0 0
X
+ 1 +1 + 1 +1 0 0 0
Bien thiic nghiem U,(v)
70 90 70 90 70 90 70 90 80 80 80
t(s) 0,1 0,1 0,7 0,7 0,1 0,1 0,7 0,7 0,4 0,4 0,4
t.(s) 8 8 8 8 16 16 16 16 12 12 12
Gia tri do nham Lan 1
2,14 2,65 2,95 2,01 2,74 3,03 3,03 3,15 2,65 2,55 2,35
Lan 2 2,35 2,16 2,16 3,07 2,23 3,07 2,98 3,27 3,0 2,73 3,24
Lan 3 3,13 2,84 2,84 2,66 2,94 2,76 3,23 3,47 2,84 2,98 3,15
R(pm) 2,54 2,55 2,56 2,57 2,63 2,95 3,08 3,29 2,83 2,75 2,91 4.2.1.3. Do thi bieu diin moi quan he giUa do nhdm R^ vdi t^ 1/ khi t^ = 8 (s)
TAP CHI CO KHI VIET NAM, So 4 nam 2014 il^hiviPl^i
NGHIEN CUfU-TRAO D C I
Theo ket qua do dp nham va do thi bieu diln mdi quan he gifla dp nham be mat R^ vdi cac thdng sd U; t; t^ thi ta cd the nhan xet nhU sau:
- Khi gia cdng cat day vdi dien ap thap, dp keo dai xung nhd thi gia tri nham be mat chi tiet la rat thap tUe la be mat chi tiet tUPng ddi mm.
- Khi gia cdng cat day vdi dien ap tang dan, dp keo dai xung Idn thi gia tri nham be mat chi ti^t la rat cao tUc la be mat chi tiet se khdng dflpc nhan bong.
5. KET L U A N
Vdi cac thiet bi do dp nham cua hang Mitutoyo (Nhat Ban), tac gia da tien hanh do dUpc do nham be mat chi tiet trong qua trinh gia cdng thep hop kim bang phUPng phap eat day tia l^a dien. Til nhflng ket qua do dupe (dp nham hi mat) tac gia da dUa ra dUpc mdi quan he gifla che dp cat va do nham be mat chi tiet, ket qua nay vUa giup cho viec phan tich nguyen nhan gay ra nham be mat ben canh dd con lam co sd cho viec nghien eflu cac moi quan he giUa cac che dp cat den nang suat gia cdng va tudi ben cua dung cu cat (day cat).*>
Ngay nhan bai: 12/3/2014 Ngay phan bien: 14/4/2014
Tai lieu tham khao:
[l].Nguyen Van Tuan, VuNgoc Pi, Nguyin Van Hung, Cac phUdng phap gia cong tien tien,NXB. Khoa hoc va Ky thuat (2008).
[2]. http://www.meslab.org/mes/threads/2517-Cong-nghe-gia-cong-xung-dinh-hinh.html, truy cap ngay 01/04/2014.
[3]. Nghiem Hung, Giao trinh vat lieu hoc. Tit sach Dai hpc Bach khoa Ha Npi (1999).
[4]. Trung tam Hoc lieu, Dai hoc Thai Nguyen, http://www.Irc-tnu.edu.vn.
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