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H THNG SN XUT TC THI

Just-In-Time = JIT

Chin lc Just-In-Time (JIT) c gi gn trong mt cu: "ng sn phm vi

ng s lng ti ng ni vo ng thi im". Trong sn xut hay dch v, mi

cng on ca quy trnh sn xut ra mt s lng ng bng s lng m cng

on sn xut tip theo cn ti. Cc quy trnh khng to ra gi tr gia tng phi

b. iu ny cng ng vi giai on cui cng ca quy trnh sn xut, tc l h

thng ch sn xut ra ci m khch hng mun.

Ni cch khc, JIT l h thng sn xut trong cc lung nguyn vt liu, hng

ho v sn phm truyn vn trong qu trnh sn xut v phn phi c lp k

hoch chi tit tng bc sao cho quy trnh tip theo c th thc hin ngay khi

quy trnh hin thi chm dt. Qua , khng c hng mc no ri vo tnh trng

khng, ch x l, khng c nhn cng hay thit b no phi i c u vo

vn hnh.

Cc dy truyn lp rp ca hng Ford p dng JIT t nhng nm 30. Cn ni

thm rng Ford l ngi i u trong vic p dng cc dy truyn sn xut. Tuy

nhin, phi n nhng nm 1970, quy trnh sn xut theo m hnh JIT mi c

hon thin v c Toyota Motors p dng. Trong cng cuc cng nghip ho

sau i chin th gii th 2, nc Nht thc hin chin lc nhp khu cng

ngh nhm trnh gnh nng chi ph cho nghin cu v pht trin (R&D) v tp

trung vo vic ci thin quy trnh sn xut (kaizen). Mc tiu ca chin lc ny

l nng cao cht lng v tin cy ca sn phm. Eiji Toyoda v Taiichi Ohno

ca Toyota Motor pht trin mt khi nim h thng sn xut mi, m ngy

nay c gi l H thng SX Toyota. Nhiu nh nghin cu cho rng nc Nht

c c ngy hm nay xut pht t nn tng sn xut da trn h thng tuyt

vi .

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th cng tm hiu JIT trong h thng sn xut Toyota, trc ht cn phn bit

c hai khi nim sn xut truyn thng l tinh xo (craft) v i tr (mass).

Sn xut tinh xo thng s dng cc cng nhn cc k lnh ngh cng vi

nhng cng c n gin nhng linh hot (c bit trong cc ngnh ngh th

cng) to ra tng sn phm theo khch hng. Cht lng ca hnh thc

sn xut ny c l khi cn phi bn, tuy nhin gi thnh dn ti gi bn rt cao

l yu t lm thu hp th trng. Cng v th m sn xut i tr ra i, nh

du mt bc pht trin trong sn xut u th k 20.

Sn xut i tr s dng cng nhn c tay ngh bc trung vn hnh cc my

cng nghip n nng, to ra cc sn phm c tiu chun ho vi s lngrt ln. V gi tr my mc cng nh chi ph ti thit k rt t tin nn nh sn

xut i tr lun c gng gi cc tiu chun thit k sn phm cng lu cng tt.

Kt qu l gi thnh ko theo gi bn gim. Tuy nhin tc phong cng nghip

lm cho cng nhn nhm chn v mt ng lc lm vic.

Toyota Motor kt hp 2 phng thc sn xut tinh xo v i tr, loi b cc

yu im v gi thnh v s cht ch cng nghip, cho ra i mt phng thc

sn xut mi vi i ng cng nhn c tay ngh cao c trang b h thng my

mc linh hot, a nng, c kh nng sn xut vi nhiu mc cng sut. Phng

thc ny c nh gi l s dng t nhn lc hn, t din tch hn, to ra t ph

phm hn, v sn xut c nhiu loi sn phm hn hnh thc sn xut i

tr.

Nn tng ca h thng sn xut Toyota da trn kh nng duy tr lin tc dng

sn phm trong cc nh my nhm thch ng linh hot vi cc thay i ca th

trng, chnh l khi nim JIT sau ny. D tha tn kho v lao ng c hn

ch ti a, qua tng nng sut v gim chi ph. Bn cnh , mc d kh

nng gim thiu chi ph l yu cu hng u ca h thng, Toyota a ra 3

mc tiu ph nhm t c mc tiu chnh yu :

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- Kim sot cht lng: gip cho h thng thch ng hng thng hay thm ch

hng ngy vi s thay i ca th trng v s lng v a dng.

- Bo m cht lng: m bo mi quy trnh ch to ra cc n v sn phm tt

cho cc quy trnh tip theo.

- Tn trng con ngi: v ngun nhn lc phi chu nhiu sc p di n lc

gim thiu chi ph.

Trong quy trnh lp rp t, cc linh kin phi c cc quy trnh khc cung cp

ng lc vi ng s lng cn thit. T , tn kho s gim ng k ko theo

vic gim din tch kho hng. Kt qu l chi ph cho kho bi c trit tiu, tng

t sut hon vn. Tuy nhin, trong mt ngnh cng nghip phc tp nh ngnh

t, vic p dng JIT vo tt c cc quy trnh l iu rt kho khn. Toyota Motor thc hin theo hng ngc li, tc l cng nhn ca quy trnh sau s t

ng ly cc linh kin cn thit vi s lng cn thit ti tng quy trnh trc

. Va nh vy, nhng g m cng nhn quy trnh trc phi lm l sn xut cho

s linh kin c ly i.

Kanban l mt h thng thng tin nhm kim sot s lng linh kin hay sn

phm trong tng quy trnh sn xut. Mang ngha mt nhn hay mt bng hiu,

mi kanban c gn vi mi hp linh kin qua tng cng on lp rp. Mi

cng nhn ca cng on ny nhn linh kin t cng on trc phi li 1

kamban nh du vic chuyn giao s lng linh kin c th. Sau khi c in

y t tt c cc cng on trong dy truyn sn xut, mt kamban tng t

s c gi ngc li va lu bn ghi cng vic hon tt, va yu cu

linh kin mi. Kanban qua kt hp lung i ca linh kin vi cu thnh ca

dy truyn lp rp, gim thiu di quy trnh.

Kanban c p dng vi 2 hnh thc:

- Th rt (withdrawal kanban): chi tit v chng loi v s lng sn phm m

quy trnh sau s rt t quy trnh trc.

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- Th t (production-ordering): chi tit v chng loi v s lng sn phm m

quy trnh sau phi sn xut.

Sau Nht, JIT c 2 chuyn gia TQM (Total Quality Manufacturing) la Deming

v Juran pht trin Bc M. T m hnh JIT lan rng trn khp th gii. JIT

l mt trit l sn xut vi mc tiu trit tiu tt c cc ngun gy hao ph, bao

gm c tn kho khng cn thit v ph liu sn xut. Tm li, JIT to ra cc li

im sau:

- Gim cc cp tn kho bn thnh phm, thnh phm v hng ho.

- Gim khng gian s dng.

- Tng cht lng sn phm, gim ph liu v sn phm li.

- Gim tng thi gian sn xut.- Linh hot hn trong vic thay i phc h sn xut.

- Tn dng s tham gia ca nhn cng trong gii quyt vn .

- p lc v quan h vi khch hng.

- Tng nng sut v s dng thit b.

- Gim nhu cu v lao ng gin tip.

Cng vi s pht trin nh v bo ca cng ngh truyn thng thng tin, JIT

tr thnh kh nng cnh tranh phi c i vi bt c doanh nghip no.