chƯƠng 2 p2 Ép phun &kẾt cẤu khuÔn.pdf
TRANSCRIPT
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CHNG II
PHNG PHP P PHUN V KT CU KHUN
I. MY P PHUN
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1. Cu to chung:
My p phun gm c cc h thng c bn nh trong hnh v:
1.1. H thng h tr p phun:
L h thng gip vn hnh my p phun. H thng ny gm 4 h thng con:
- Thn my.
- H thng in
- H thng thy lc
- H thng lm ngui
1.1.1. Thn my:
Lin kt c h thng trn my li vi nhau.
1.1.2. H thng thu lc:
Cung cp lc ng v m khun, tao ra v duy tr lc kp, lm cho trc vt quay
v chuyn ng ti lui, to lc cho cht y v s trt ca li mt bn. H thng
ny bao gm bm, van, motor, h thng ng, thng cha nhin liu
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H thng thy lc
1.1.3. H thng in:
Cp ngun cho motor in v h thng iu khin nhit cho khoang cha vt liu
nh cac bng nhit v m bo s an ton in cho ngi vn hnh my bng cc
cng tc. H thng ny gm t in v h thng dy dn.
H thng in
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1.1.4. H thng lm ngui:
Cung cp nc hay dung dch ethyleneglycol lm ngui khun, du thy lc
v ngn khng cho nha th cung phu b nng chy. V khi nha cung phu
b nng chy th phn nha th pha trn kh chy vo khoang cha liu. Nhit
trao i cho du thy lc vo khong 90 F. B iu khin nhit nc cung
cp mt lng nhit, p sut, dng chy thch hp lm ngui nha nng trong
khun.
H thng lm mt
1.1.5. H thng phun:
H thng phun lm nhim v a nha vo khun thng qua cc qu trnh cp
nha, nn, kh kh, lm chy do nha, phun nha lng v nh hnh sn phm.
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H thng phun
H thng ny gm cc b phn.
- Phu cp nhit: cha vt liu nh dng vin cp vo khoang trn
- Khoang cha liu: Cha nha v vt trn di chuyn qua li bn trong n.
Khoang trn c gia nhit nh cc bng cp nhit. Nhit xung quanh khoang
cha liu cung cp t 20 n 30% nhit cn thit lm chy lng vt liu
nha.
- Cc bng gia nhit: Gip duy tr nhit khoang cha liu nha bn trong
khoang lun trng thi chy do. Thng thng, trn mt my p nha c th c
nhiu bng gia nhit c ci t vi cc nhit khc nhau to ra cc vng
nhit thch hp cho qu trnh p phun.
- Trc vt: C chc nng nn, lm chy do v to p lc y nha chy do vo
lng khun. Trc vt c cu to gm 3 vng c minh ha trong hnh v:
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Cu to trc vt
- B hi t h: B phn ny gm cng chn hnh nm, u trc vt v seat. Chc
nng ca no l to ra dng nha bn vo khun. Khi trc vt li v th vng chn
hnh nm di chuyn v hng vi phun v cho php nha chy v pha trc u
trc vt. Cn khitrc vt di chuyn v pha trc th vng chn hnh nm s di
chuyn v hng phu ng kn vi seat khng cho nha chy ngc v pha sau.
B hi t m hay van hi t m
- Vi phun: C chc nng ni khoang trn vi cung phun v phi c hnh dng
m bo bt kn khoang trn va khun. Nhit vi phun nn c ci t ln
hn hoc bng nhit chy ca vt liu. Trong qu trnh phun nha lng vo
khun, vi phun phi thng hng vi bc cung phun v u vi phun nn c lp
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kn vi phn lm ca bc cung phun thng qua vng nh v m bo nha
khng b phun ra ngoi v trnh mt p.
V tr vi phun trong h thng phun
1.1.6.H thng kp:
H thng kp
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H thng kp c chc nng ng, m khun, to lc kp gi khun trong qu trnh
lm ngui v y sn phm thot ra khi khun khi kt thc mt chu k p phun.
H thng ny gm cc b phn:
- Cm y ca my: Gm xylanh thy lc, tm y v cn y. Chng c chc
nng to ra lc y tc ng vo tm y trn khun y sn phm ri khi
khun.
- Cm km: Thng c hai loi chnh, l loi dng cho c cu khuu v loi
dng cc xylanh thy lc. H thng ny c chc nng cung cp lc ng m
khun v lc gi khun ng trong sut qu trnh phun.
- Tm di ng: L mt tm thp ln c b mt c nhiu l thng vi tm di ng
ca khun. Chnh nh cc l thng ny m cn y c th tc ng lc vo tm
y trn khun. Ngoi ra, trn tm di ng cn c cc l trn ren kp tm di
ng ca khun. Tm ny di chuyn ti lui dc theo 4 thanh ni trong sut qu
trnh p phun.
Tm di ng v v tr ca n trn my p phun
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- Tm c nh: Cng l mt tm thp ln c nhiu l thng vi tm c nh ca
khun. Ngoi 4 l dn hng v cc l c ren kp tm c nh ca khun tng
t nh tm di ng, tm c nh cn c thm l vng nh v nh v tm c
nh ca khun v m bo s thng hng gia cn y v cm phun
( vi phun v bc cung phun)
Tm c nh v vi tr ca n trn my p phun
- Nhng thanh ni: C kh nng co gin chng li p sut phun khi km to lc.
Ngoi ra chng cn c tc dng dn hng cho tm di ng.
1.1.7. H thng iu khin:
H thng iu khin gip ngi vn hnh my theo di v iu chnh cc thng s
gia cng nh: nhit , p sut, tc phun, vn tc v v tr ca trc vt, v tr ca
cc b phn trong h thng thy lc. Qu trnh iu khin c nh hng trc tip
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n cht lng sau cng ca sn phm v hiu qu kinh t ca qu trnh. H thng
iu khin giao tip vi ngi vn hnh my qua bng nt iu khin v mn hnh
my tnh.
- Mn hnh my tnh: Cho php nhp cc thng s gia cng, trnh by cc gi liu
ca qu trnh p phun, cng nh cc tn hiu bo ng v c thng ip.
- Bng iu khin: Gm cac cng tc v cc nt nhn dng vn hnh my. Mt
bn iu khin in hnh gm c: Nt nhn iu khin bm thy lc, nt nhn tt
ngun in hy dng khn cp v cc cng tc iu khin bng tay. Bn trong h
thng iu khin l b vi x l cc rle, cng tc hnh trnh, cc b phn iu
khin nhit , p sut, thi gian
2. Qui trnh cng ngh:
Nguyn cng 1: Chun b vt liu:
- Bc 1:Chuyn vt liu dng khi, tm sang dng ht. S dng my nghin
nhm nghin nh vt liu. Ht cng nh th kh nng phn b cng u hn.
- Bc 2: Trn vt liu: S dng my khuy, my trn truc vt to ra s chuyn
ng tng i gia cc ht trong vt liu nhm pha trn u.
- Bc 3: Lm do v nhuyn ha vt liu: Vt liu c trn u v sy kh
bc gia cng trc c lm nng chy, sau n c lm nhuyn v to th
thng nht.
- Bc 4: To ht cho vt liu: Vt liu c to thnh bng 2 phng php: To
ht nng v ngui. To ht nng c lp them u n nhiu l. Vt liu qua u
n c ct thnh nhng kch thc nht nh qua khoang cha lm ngui v
c lm ngui bng nc hoc khng kh. To ht ngui bng nc th c em
i sy kh ri ng gi.
Nguyn cng 2:
Qu trnh c phun nha: Vt liu cht do c cho vo phu nh hng v cp
liu trn xilanh ca my i vo rnh trc vt trong xilanh. Do chuyn ng quay
ca trc vt lm cho vt liu c vn chuyn ln pha vi phun. Trong sut qu
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trnh , vt liu c cp nhit t thnh xilanh do cc nhn t cung cp nh hi
nng, in tr.
Nguyn cng 3:
Qu trnh c phun gi p sut p nha v lm mt: Lng vt liu cn thit
in y khoang to hnh ca khun c tp trung khoang trng trc trc vt.
Trong qu trnh in y khun, trc vt thc hin chuyn ng dc trc v pha
trc, p lc tng y khi vt liu nng chy qua vi phun vo khun. Giai on
tng p ngay khi vt liu in y vo khun. Trong giai on ny di p lc t
ngoi mt lng nh vt liu c thm vo lng khun v p lc tng theo chiu
dc khun. Khi vt liu ngui gy ra hin tng co ngt v p lc khun gim
xung. p lc cc im khc nhau dc theo khun khng ng u p lc trong
khun, giai on ny ph thuc vo p lc do piston c phun truyn cho v ph
thuc vo kt cu ca my. Kt cu ca my c phun c nh hng n c trng
thay i p lc trong khun. c trng thay i p lc dc theo khun ph thuc
vo dy khoang nh hnh ca khun. B dy tng th cng d truyn lc. Tc
lm ngui cng ln, nht ca vt liu cng tng, gim vic truyn p lc.
c trng ca truyn p lc vt liu ph thuc nhiu vo nhit ca vt liu.
Nhit ca v chy ca vt liu tng to thun li cho vic truyn p lc, khi
nhit gim lm cho vic truyn p lc gp kh khn.
Nguyn cng 4:Qu trnh sau khi lm mt v m khun.
Trong giai on ny p lc trong khun nh hn so vi giai on tng p sut.
Thay i p lc trong giai on ny c quyt nh bi tc lm ngui. Tc
lm ngui sn phm quyt nh i lng ng sut d xut hin trong qu trnh
chy, ng thi nh hng n s hnh thnh ng sut mi.
Nguyn cng 5: Qu trnh kh bavia v lm sch sn phm:
Khi sn phm c a ra khi khun th qu trnh ct bavia v lm sch sn phm
c thc hin. Tip l qu trnh kim tra cc khuyt tt nh r co, nt.
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II. TNG QUAN V KHUN P PHUN:
Mt thit k c bt u khi nh thit k nhn c bn v hay mu sn
phm. Cc thng s c bn lc ny s l : My gia cng thuc lai no? C bao
nhiu long khun trong mt khun? Loi nha dng cho sn phm? Nhn thy
rng cc thng tin ny thc s quan trng nhng chng ta cn lu ti cc vn
sau :
1. Cc tnh cht ca nha lm sn phm .
2. S lng sn phm cn sn xut l bao nhiu ta c th tnh ton s B
tui th ca khun .
3. Chu k p ht bao nhiu thi gian.
4. Ni sn phm s dng v sn phm dng vo vic g?
5. Dung sai lp gp ca sn phm (nu c ).
6. co rt ca nha lm sn phm .
7. Gc thot khun bao nhiu th ph hp.
8. Loi h thng no l ph hp, knh dn ngui hay knh dn nng hay c hai
loi
9. V tr ming phun ,dng chy ,ng dn ,ni li sn phm.
10. Kch thc ca ming phun .
11. Trn khun c khc ha hoa vn hay k t g khng?
12. Cc chi tit thay th cho khun khi cn thit.
13. Cc thng s ca my p phun, kch c, kch thc u phun, cng sut lm
do.
14. Tnh t ng ha ca my.
15. Thi gian hon thnh.
16. Gi thnh.
Ngoi cc vn trn nh thit k cng cn phi tip nhn thm mt s
thng tin t pha khch hng c mt thit k tha mn nhu cu khch.
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1. GII THIU CU TRC MT B KHUN:
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2. CHN LOI KHUN THIT K:
2.1. Khun hai tm:
2.1.1. Khun hai tm c knh dn ngui:
Khun hai tm l loi khun n gin nht. So vi khun hai ba tm th gi
khun hai tm r hn v chu k p phun ngn hn. i vi khun hai tm c mt
lng khun th khng cn n knh dn nha v nha s in y trc tip vo
khun thng qua bc cung phun. i vi khun hai tm c nhiu lng khun th
ta nn quan tm nhiu n vic thit k knh dn v ming phun sao cho nha c
th in y vo cc lng khun cng lc (vn cn bng dng chy ca nha).
Trc khi bt u thit k khun loi ny ta nn dng mt mu phn tch th
trn phn mm tm ra v tr t ming phun thch hp nht. Khi xt thy v tr
cc ming phun c th t thng hng vi cc lng khun th vic dng khun hai
tm l thch hp.
Khun hai tm c knh dn ngui
V vn cn bng dng v i hi cc ming phun phi c b tr thng
hng vi cc lng khun m vic thit k khun hai tm c nhiu lng khun gp
nhiu hn ch i vi mt s loi nha nht nh. Do khc phc nhc
im ny ngi ta dng n khun ba tm hoc khun hai tm c knh dn nng.
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Kt cu khun hai tm c nhiu lng khun.
2.1.2. Khun hai tm c knh dn nng:
Khun hai tm dng knh dn nng lun gi cho nha chy trong bc
cung phun, knh dn v ming phun nha ch ng c khi n chy vo lng
khun. Khi khun m ra th ch c sn phm (i khi c knh dn ngui) c
ly ra ngoi. Khi khun ng li th nha trong cc knh dn vn nng v tip
tc in y vo lng khun mt cch trc tip. Knh dn trong khun c th
bao gm c knh dn ngui v knh dn nng.
Kt cu khun hai tm c knh dn nng.
i vi loi khun ny, cc ming phun phi c v tr trung tm ca
Cc lng khun. iu ny c ngha l cc knh dn phi c t xa mt Phn
khun. Nhng iu ny khng gy bt k tr ngi no cho vic thit k. Loi
khun ny cng ph hp vi khun c nhiu lng khun vi kch thc nh hay
nhng khun m h thng knh dn phc tp v ph nhiu vt liu.
- u im :
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+ Tit kim vt liu.
+ Khng c vt ca ming phun trn sn phm.
+ Gim thi gian chu k.
+ iu khin c s in y v dng chy ca nha.
- Nhc im :
+ Gi thnh cao hn khun hai tm c knh dn ngui.
+ Kh i mu vt liu
+ H thng iu khin nhit d b hng.
+ Khng thch hp vi nhng vt liu chu nhit km.
2.2. Khun ba tm:
So vi khun hai tm thi h thng knh dn ca khun ba tm c t trn
tm th hai song song vi mt phn khun chnh. Chnh nh tm th hai ny
m knh dn v cung phun c th ri ra khi sn phm khi khun t m (t ct
ui keo).
Kt cu khun ba tm.
Khun ba tm c s dng khi m ton b h thng knh dn khng
th t trn cng mt phng nh khun hai tm. iu ny c th l do:
> Khun c nhiu lng khun.
> Khun c mt lng khun nhng phc tp nn cn hn mt vi tr
phun nha.
> Kh khn trong vic chn ra mt vi tr phun thch hp khc.
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> V phi cn bang dng nha gia cc knh dn vi nhau nn
buc phi thit k knh dn khng nm trn mt phan khun.
im c trng ca khun ba tm l t ct ui keo.
Khun ba tm.
u im :
+ Gi thnh thp hn so vi khun hai tm c knh dn nng.
+ t b hng hc hn khun c knh dn nng.
+ C th ph hp vi nhng vt liu chiu nhit km.
Nhc im :
+ Chu k p phun tng do hnh trinh ca ng nha in y lng
khun di.
+ Lng ph nhiu vt liu.
+ Cn p sut phun ln in y.
3. TNH GI KHUN:
Sau khi chn c loi khun cho thit k, iu quan trng l ngi thit
k phi a ra mt gi khun ph hp cho khch hng. Thng thng gi
khun c tnh bi ngi thit k hay ngi chuyn bo gi ca b phn kinh
doanh. Khi bo gi thng da vo kinh nghim v gi ca loi khun
c thit k trc . Ngoi ra, ngi bo gi cng c th da vo tnh phc
tp hay tnh mi l ca sn phm bo gi. Mc ch cui cng ca vic bo
gi l a ra mt gi hp l v c tnh cnh tranh trn thi trng. Do ngi
bo gi v ngi thit k cn Phi hiu r loi khun s c lm v h thc s
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phi n khp vi nhau trnh trng hp bo gi qu cao hay qu thp. Tuy
nhin m s khch hng tnh s b gi khun trc khi h t hng v th gi
khun cng c th c nh ngay thi in t hng .
4. THIT K LNG KHUN:
4.1. S lng khun:
Ta c th cn nhc chn s lng khun ph hp vi cc thng tin sau :
Kch thc my p phun( nng sut phun ln nht v lc kp ln nht).
Thi gian dao hng.
Yu cu v cht lng sn phm.
Kt cu v kch thc khun.
Gi thnh khun.
S lng khun thng thng c thit k theo dy s sau :2, 4, 6, 8, 12, 16,
24, 32, 48, 64, 96, 128. V cc lng khun s d dn c sp xp theo hnh
ch nht hoc hnh trn.
Thng thng ta c th tnh s lng khun cn thit trn khun da vo: S
long sn phm, nng sut phun v nng sut lm do ca my phun, lc kp
khun ca my.
S lng khun tnh theo s lng sn phm trong n t hng :
n = L x K x tc / ( 24 x 3600 x tm)
Trong :
n : S lng khun ti thiu trn khun.
L : S sn phm trong mt l sn xut.
K : H s do ph phm, K=1/(1-k). Vi k l t l ph phm.
tc : Thi gian ca mt chu k p phun (s).
tm: Thi gian hon tt l sn phm ny.(ngy)
S lng khun tnh theo nng sut phun ca p phun :
n = 0,8xS/W
Trong :
n : S lng khun ti thiu trn khun.
S : Nng sut phun ca my(gam/mtlnphun).
W : Trng long ca sn phm (g).
S lng khun tnh theo nng sut lm do ca my :
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n = P/(X x W).
Trong :
n : S lng khun ti thiu trn khun.
P : Nng sut lm do ca my (g/pht).
X : Nn s phun trong 1 pht (1/pht).
W : Trng lng ca sn phm (g).
S lng khun tnh theo lc kp khun ca my :
n = S x P/ FP
Trong :
n : S lng khun ti thiu trn khun.
S : Din tch b mt trung bnh ca sn phm k c cc rnh dng tnh
theo hng ng khun.(mm2)
Fp : Lc kp khun ti a ca ca my (N)
P : p sut trong khun (Mpa).
4.2. Cch b tr lng khun:
Trn thc t, ngi ta thng b tr lng khun theo kinh nghim m
khng c bt k s tnh ton hay m phng no. Nhng nu lm nh vy i
khi ta gp mt s li trn sn phm, c bit i vi nhng khun c nhng
lng khun khc nhau trn cng mt khun v khi y ta phi sa loi khun( iu
ny rt tn cng v tn km thi gian v tin bc). Do trnh vic ny xy
ra ta nn m phng qu trnh in y ca tng lng khun m khng c h
thng knh dn bit chng c in y nh th no. Khi y ta s thit k
h thng knh dn to s cn bng dng cho tng lng khun.
Khi b tr lng khun ta nn b tr lng khun theo cc cch sau:
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Cc kiu b tr lng khun dng hnh ch nht.
Cc kiu b tr lng khun dng hnh trn v ng thng.
5. THIT K H THNG DN NHA:
H thng nha trong khun lm nhim v a nha t vi phun ca my
p phun vo cc lng khun. H thng ny gm: cung phun, knh dn v ming
phun.Thng thng trong thit k ngi ta thit k knh dn v ming phun
trc ri mi n cung phun v kch thc ca cung phun ph thuc vo kch
thc knh dn v ming phun.
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H thng dn nha.
5.1. Cung phun (Sprue):
Cung phun ni trc tip vi vi phun ca my p phun a nha vo
knh dn qua ming phun vo cc lng khun.
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V tr cung phun.
u cung phun nn cng nh cng tt nhng vn phi m bo s
in y ng u gia cc lng khun vi nhau. Gc cn ca cung phun
cn phi ln d thot khun nhng ng knh cung phun th ng
qu ln v s lm tng thi gian lm ngui v tn vt liu. Trn thc t
ngi ta t gia cng cung phun lin trn khun (tr nhng khun n gin)
m ngi ta dng bc cung phun tin gia cng v thay th.
Hin ti trn thi trng c 3 loi bc cung phun ph bin c cc ng
knh ngoi 12mm,14mm,20mm. Ty thuc vo khi lng tng sn phm,
kch thc knh dn v ng knh ca vi phun trn my phun m ta
dng loi bc cung phun no cho ph hp.
Bc cung phun trn khun.
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Trn khun, cung phun s c y ri khi khun cng lc vi sn
phm. Do cn c mt b phn ko cung phun li trn tm di ng
(tm khun c) khi m khun cung phun c th ri khi bc cung
phun.Thm vo , ngi thit k c th li dng phn nha gi cung
phun lm ui ngui chm (cold slug well) nh m qu trnh in y cc
lng khun tt hn.
5.2. Knh dn nha (Runners):
Cc knh dn nha l cu ni gia cc ming phun v cung phun. Chng
lm nhim v a nha vo cc lng khun.V th khi thit k chng cn
phi tun th mt s cc nguyn tc k thut m bo cht lng cho
hu ht sn phm. Sau y l mt s nguyn tc m ta cn phi tun th :
> Gim n mc ti thiu s thay i tit din knh dn.
> Nha knh dn phi thot khun d dng.
> Ton b chiu di knh dn nn cng ngn nu c th trnh mt p v
mt nhit trong qu trnh in y.
> Mt ct knh dn phi ln m bo s in y cho ton b sn
phm m khng lm thi gian chu k qu di, tn thm nhiu vt liu v
lc kp ln.
5.2.1. Knh dn ngui:
A. :Cc loi tit din ngang ca knh dn nha:
Knh dn c nhiu dng mt ct ngang khc nhau nhng ph bin
l cc loi knh dn c mt ct ngang hnh trn, hnh thang hiu chnh,
hnh thang,hnh ch nht v hnh bn nguyt.
Cc loi tit din knh dn nha.
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so snh cc loi knh dn ngi ta dng ch s ng knh thy
lc v s cn dng. Khi ng knh cnh ln th s cn dng cng b. Ta c
th tnh ng knh thy lc da vo cng thc sau:
Dh = 4A/P
Vi : Dh : ng knh thy lc.
A : Din tch mt ct ngang.
P : Chu vi.
B. :Kch thc knh dn nha:
Vic tnh ton c ng knh v chiu di knh dn hp l l Rt
quan trng v khi mt knh dn qu ln hay qu di s lm cn Tr ng
v gy tn nhiu vt liu v lm tng thi gian chu k.Do ta nn thit
k knh dn nh mc c th c th li dng nhit Ma st trn n gia
nhit cho nha lng gip qu trnh in y lng Khun thun li hn v
sn phm t b qu nhit.
Ngoi ra ta c th tnh ton kch thc knh dn theo cng thc sau :
D = W x L /3,7
Trong :
D : ng knh knh dn(mm).
W : khi lng sn phm (g)
L : chiu di knh dn (mm)
Hoc : D = D x fL
Trong : D : ng knh knh dn tham kho.
fL : h s chiu di.
5.2.2. Knh dn nng :
Knh dn nng c dng cho nhng sn phm c kch thc ln (v
tivi,vi tnh,cc chi tit trn xe hi) hoc mng hoc lm bng loi nha cn
c duy tr ti nhit chy do nh: HDPE, LDPE, POM, PBT, PCBn trong
knh dn nha s lun c duy tr trng thi chy do m bo sn phm
c in y ng b.
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Cc loi h thng knh dn nng.
C hai loi knh dn nng: knh dn cch ly v knh dn gia nhit.
Knh dn cch ly (insulated runners) :
Knh dn cch ly c cu to gm mt lp nha ngui ng vai tr l mt
lp cch ly v mt li nha lun c duy tr trng thi chy do nh ng
nhit in. Bn trong ng nhit in l cht nhn c th di chuyn ln xung
ng ngt dng phun nha. Nh vy, kch thc ming phun ln hay nh s ty
thuc vo khe h m cht cho dng nha chy qua.
Hnh 1.13: Knh cch ly.
+ u im :
- D thit k.
- Gi thnh r.
- Tit kim vt liu do ph liu vt liu.
+Nhc im :
- Thi gian chu k qu ngn d duy tr trng thi chy do cho
nha.
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- Cn thi gian khi ng di n inh nhit chy do.
- i khi gp mt s li trong qu trnh in y.
- Kh i mu vt liu.
Knh dn c gia nhit (heated runners) :
Knh dn c gia nhit gm hai lai: loi gia nhit trong v gia nhit ngoi.
Knh dn gia nhit ngoi c b gia nhit bao quanh li nha nng. Cn knh dn
gia nhit trong th c nha bao quanh cht nng. Tng t nh knh dn cch
ly,lu lng phun u c iu khin bi s di chuyn ca cht.
5.2.3. Ming phun cho knh dn ngui:
Ming phun l ng kt ni knh dn v lng khun. Ming phun c chc
nng rt quan trng l a nha lng in y vo lng khun v th vic tnh
ton kch thc v b tr ming phun c ngha quyt inh dn cht lng sn
phm.
Ming phun trn khun.
5.2.3.1. Cc loi ming phun ct bn tay:
Loi ming phun trc tip thng dng cho cc khun c mt lng khun,
ni m vt liu c in y vo lng khun trc tip m khng qua h thng
knh dn. Chnh v khng c h thng knh dn nn vic mt p trong qu trnh
in y l rt b. Tuy nhin, nhc im ca loi ming phun ny l li vt
ct rt ln trn b mt sn phm. S co rt c quyt inh bi b dy sn
phm v ng knh.
5.2.3.2. Phn loi ming phun:
a) Ming phun bng tay:
Ming phun ct bng tay l loi ming phun dnh theo sn phm sau khi
p phun. Ta d dng nhn ra cc sn phm nha c ming phun ct bng tay qua
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vt ct cn li trn b mt ca chng. Do , vi loi ming phun ny nn thit k
kch thc nh mc c th m bo tnh thm m cho sn phm ming phun.
in hnh l s co rt ca phn nha gn ming phun s nh v ti ming phun
s ln. iu ny a n hu qa l ng sut cng gn ming phun ln.
b) Ming phun kiu bng(Tab gate):
Ming phun kiu bng thng c lm gim ng sut trong lng
khun v ngn nga li to ui cho cc chi tit phng v mng. ng sut sinh
ra trong lng khun s c tp trung bng, m s c ct b sau khi p phun.
Ming phun kiu bng ph hp dng cho cc loi nha PC, Acrylic, SAN,
ABS,
Ming phun kiu bng v vt ct n li.
c) Ming phun cnh (Edge gate):
L loi ming phun thng dng, c th dng cho nhiu sn phm bi kt cu
rt n gin v khng cn chnh xc cao. Ming phun cnh c t trn mt
phn khun v in y lng khun t bn hng, trn hay di.
d) Ming Phun kiu gi(Overlap gate):
L l ming phun tng t nh ming phun kiu cnh,ch khc nhau ch
l ming phun nm lp trn b mt sn phm.
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Ming phun kiu gi.
e) Ming phun kiu qut:
Ming phun kiu qut thc cht cng l ming phun kiu cnh c b rng
b bin i. Ming phun kiu ny cho dng chy m v cho php in y lng
khun mt cch nhanh chng nn rt ph hp cho cc sn Phm ln v dy.
Thm vo , ming phun kiu qut cng to ra dng chy lan ta nn gip
trnh c ng hn ni c b dy mng trn sn phm.
Ming phun kiu qut.
Ming phun kiu qut nn c lm cn c b rng ln b dy c
mt ct ngang khng thay i. iu ny gip m bo :
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+ Vn tc chy l hng s.
+ Ton b b rng c dng cho lu lng.
+ p sut nh nhau qua ton b b rng.
5.2.3.3. Ming phun t ngt:
a)Ming phun im( point gate):
Ming phun im thng dng cho khun ba tm c nhiu lng khun, hay
c kch thc lng khun ln. Khi thit k ming phun im ngi ta thng
dng knh dn c tit din hnh thang hay hnh thang bin i tin vic gia
cng v lp cht ko h thng knh dn ming phun ri khi sn phm d dng
hn. u im chnh ca ming phun im l gip b tr nhiu ming phun vo
cng mt lng khun khi lng khun c kch thc ln. i u ny khin qu
trnh in y cc vng khc nhau trn sn phm din ra nhanh chng v tt hn.
Tuy nhin, cn lu khun c th bi tng nhit gy qu nhit i vi nhng vt
liu c cu trc si di v c nht thp do ming phun c kch thc nh.
Ming phun kiu im.
Kch thc khuyn dng cho thit k:
Kch thc thit k ming phun im.
b)Ming phun ngm(tunners gate or submarine gate):
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Ming phun ngm thng c dng trong khun 2 tm c nhiu
lng khun.Khi thit k sn phm nh v cn ct keo mt bn Ta nn ngh
n kiu ming phun ny.
C hai loi ming phun ngm :ming phun ngm ng thng v ming
phun ngm ng cong.
+ Ming phun ngm ng thng :
Loi ming phun ngm dng thng.
+ Ming phun ng cong :
Qu trnh ct ming phun ng cong .
c)Ming phun ca knh dn nng:
Ming phun loi ny c tiu chun ha cng vi h thng knh dn
v cung phun. Do khi cn ta ch vic lin h vi cc nh sn xut v tip thu
li khuyn t h c c thit k thch hp.
+ Kiu khng c van :Ming phun kiu ny s bi ngt khi khun
m ra v nha ming phun rt nng. S inh hnh ca sn phm c
iu khin bi phn nha ng cng gn ming phun.
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Ming phun khng c van.
+ Kiu c van : Trong knh dn c thm mt cht, cht ny c tc
dng nh mt van c th ng ming phun ngay trc khi nha Gn
ming phun ng c. iu ny cho php tng cng kch thc ng
knh ming phun ln hn v iu khin qu trnh nh hnh tt hn.
Ming phun kiu c van.
6. H THNG DN HNG:
H thng dn gm cht n hng v bc dn hng.
Bc dn hng&Cht dn hng
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6.1. Cht dn hng:
- Cht trn khng c vai:
- Cht trn c vai:
6.1.1. Bc dn hng :
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7. H THNG LI MT BN:(H THNG TRT)
Sau khi thit k xong mt phn khun cho sn phm,nhiu khi c mt s
phn trn sn phm b vng, khng tho c theo hng m khun. Lc ny
ta cn phi c mt h thng gi l h thng li mt bn tho ra cc phn b
vng y.
7.1. Cc kt cu tho li mt bn nh hng m khun:
- Cam cht
xin:
Tho li mt bn bng cam cht xin.
- Cht c mt cam:
- Cht xin:
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-Cht do :
- Cam chn ch :
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37
7.2. Tho li bn bng xilanh-pittng:
- Kiu c nm kha :
- Kiu kha :
8. H THNG LM NGUI:
Nha lng sau khi vo khun phi c lm ngui tht nhanh t
c hnh dng m ta mong mun. Nu lm ngui khng tt th nha nng s
gia nhit cho khun v th l qu trnh nh hnh s ko di v Lm tng thi
gian chu k p phun. Do ,h thng lm ngui khun c vai tr ht sc quan
trng v n quyt nh ton b chu k p phun.
8.1. Cc phng php lm ngui :
Lm ngui bng kh: khun c lm ngui bng kh nh vo bc x nhit
ca thp lm khun ra mi trng xung quanh.
L ngui bng nc hoc hn hp Etylen Glycol: y l phng php
c dng rng ri nht hin nay.Theo phng php ny, khun c lm
ngui nh vo cc knh dn cha cht lm ngui c b tr trong cc tm
khun.
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H thng lm ngui.
a)Khun c lm ngui bng nc.
b)Khun c lm ngui bng hn hp.
8.2. Thit k h thng lm ngui :
Cc b phn trong h thng lm ngui:
H thng lm ngui hon chnh.
A : B cha (Collectionmanifold).
B : Khun (Mold).
C:ng phn phi nc hoc hn hp lm ngui
(Supplymanifold).
D : Bm (Pump).
E : Knh lm ngui (Regularcoolingchannels).
F : ng dn (Hoses).
G : Vch lm nguOi (Baffels).
H : B iu khin nhit (Temperature controllers).
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9. THIT K H THNG RNH THOT KH TRN MT PHN
KHUN:
Cc rnh thot kh nn c b tr nhng ch m vt liu c in y
sau cng trnh kt khi gy ra cc vt chy hoc sn phm khng c in
y hon ton. Chiu su ca rnh thot kh nn tun th theo kch thc khuyn
dng trnh sn phm ra l ph phm.
10. H THNG Y:
Sau khi sn phm trong khun c lm ngui,khun m ra. Lc ny sn
phm vn cn dnh trn ci khun do s ht chn khng nn cn h thng y
y sn phm rt ra.
10.1. Cc loi h thng y thng dng:
- H thng y dng cht y:
Cc cht y c gia cng rt chnh xc v c chn theo tiu chun.
Thng thng, cc cht y ch c gia cng chnh xc phn dn Hng v
c lp theo h thng trc. cng ca thn cht khong 6065Rc, cng
ca u cht khong 3035 Rc.
Cc phn t trong h thng y.
+ Mt s loi cht y :
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- H thng y dng li y:
Li y dng y nhng sn phm c thnh mng v hnh dng phc
tp. Trong trng hp ny nu ta dng cht y trn s khng hiu qu v s
khng lc y, nu c lc y i na th b mt sn phm cng b ln vo.
H thng y dng li y.
- H thng y dng ng y:
ng y dng y nhng sn phm c dng trn xoay hoc tm mng.
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H thng y dng ng y.
- H thng y dng tm tho:
Tm tho dng tho nhng sn phm hnh tr trn hay hnh hp ch
nht c b dy thnh mng. Khun s dng h thng ny,sn phm khng c vt
cht y nn lun m bo tnh thm m cho sn phm.
- H thng y dng kh nn :
Li khuyn l ta nn dng kh nn kt hp vi tm tho y sn phm
ng.
H thng y dng kh nn.
11. H THNG HI :
H thng hi c chc nng y tm y li v pha sau v gi c nh tm
y trc khi khun ng hon ton. hi tm y v ta c th dng cht hi
hoc cht khuu (Toggle-lock).
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11.1. Dng cht hi:
- Cht hi c l xo: i khi i vi khun nh n gin ta khng
cn dung n l xo.
- Cht hi tiu chun:
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Nguyn l hot ng:
Hnh 1.32:Cht y tiu chun.
Cht hi tiu chun trn khun
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11.2. Dng cht khuu
- Cht khuu hnh ch X:
Nguyn l hot ng :
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45
- Kiu ch Y :
- Kiu ch Z:
12. LM NGUI: ( nh bng khun )
nh bng khun l cng on cui cn trc khi lp rp khun. Vic nh
bng khun ht sc quan trng v n quyt nh s thot khun v tnh thm
m ca sn phm.
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Mt s dng dc dung trong qu trnh lm ngui:
- My mi tay: dung mi th mt ca long khun.
- Cc kiu mi:
- Gia bn ln:
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47
- Gia nh dng thng:
- Gia nh dng cong, mc:
- Bnh nh bng:
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- mi tay:
- Hp cht cha ht mi:
- Giy nhm v chi qut:
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III. CC KIU KHUN C BN
tiu chun ha cc loi khun, ngi ta tnh ton v a chng vo
nhng tiu chun nht nh. Do , ty theo loi khun v kch thc khun m
cch b tr cc chi tit khun nh cht,bc,bulon s khc nhau. y chng ta
s p dng tiu chun FUTABA ca Nht.
Theo tiu chun FTABA th khun gm c cc loi sau:
- Kiu S: bm keo trc tip. Trong gm c:
SA: c tm pha di tm c
SB: c thm tm bng li sn phm
SC: ging SA,nhng khng c tm
SD: ging SB,nhng khngc tm
SE,SF: kiu khun dng cho vic ly ui keo bng Robot
- Kiu D: bm keo gin tip.Trong gm c cc loi DA, DB, DC, DD, DE, DF,
ging kiu S
- Ngoi ra cn c cc kiu E, F. nhng chngkhng thng dng nn tm thi
khng bn ti y
Sau y l v d v 1 s kiu khun thng dng:
T1: tm trn (Top Plate)
A: tm ci (Cavity Plate)
B: tm c (Core Plate)
C: gi (Spacer)
E: tm y (Ejector Retainer)
F: tm gi (Ejector Plate)
T2: tm y (Bottom Plate)
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