3

CHNG II

PHNG PHP P PHUN V KT CU KHUN

I. MY P PHUN

4

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

5

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

6

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.

7

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:

8

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

9

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

10

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

11

- 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

12

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

13

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.

14

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.

15

1. GII THIU CU TRC MT B KHUN:

16

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.

17

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 :

18

+ 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.

19

> 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

20

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 :

21

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:

22

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.

23

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.

24

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.

25

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.

26

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.

27

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.

28

- 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

29

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.

30

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 :

31

+ 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):

32

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.

33

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

34

6.1. Cht dn hng:

- Cht trn khng c vai:

- Cht trn c vai:

6.1.1. Bc dn hng :

35

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:

36

-Cht do :

- Cam chn ch :

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.

38

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).

39

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 :

40

- 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.

41

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).

42

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:

43

Nguyn l hot ng:

Hnh 1.32:Cht y tiu chun.

Cht hi tiu chun trn khun

44

11.2. Dng cht khuu

- Cht khuu hnh ch X:

Nguyn l hot ng :

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.

46

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:

47

- Gia nh dng thng:

- Gia nh dng cong, mc:

- Bnh nh bng:

48

- mi tay:

- Hp cht cha ht mi:

- Giy nhm v chi qut:

49

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)

50