Lean - 7 Cong Cu Thong Ke_nhom1_lopthu6

I HC QUC GIA TP. H CH MINH

TRNG I HC BCH KHOA

KHOA QUN L CNG NGHIP

BO CO BI TP NHM

BY CNG C THNG K

H TR CHO LEAN NH TH NO?

GVHD: ThS. L PHC LUNG

SVTH: NHM 1

1/ Phm Cm T (NT) 71003854

2/ Nguyn Khc Duy 71000473

3/ o Cng Dng 71000555

4/ Nguyn Phc Hoi 71001074

5/ inh Vn Thuyn 71003302

Tp. HCM, 03/2014

i

MC LC

1 T VN .......................................................................................................... 1

2 C S L THUYT ............................................................................................... 1

2.1 Lean Manufacturing ........................................................................................... 1

2.1.1 Lean manufacturing l g ............................................................................ 1

2.1.2 Cc trit l ca Lean ................................................................................... 1

2.2 Phng php DMAIC ........................................................................................ 3

2.3 S dng DMAIC trong Lean Manufacturing .................................................... 3

2.4 7 cng c thng k ............................................................................................. 3

2.4.1 Lu (FLOWCHARTS) .......................................................................... 3

2.4.2 Phiu kim tra (Check sheets) ..................................................................... 4

2.4.3 Biu tn sut (Histograms) ..................................................................... 5

2.4.4 Biu phn tn (Scatter diagrams) ........................................................... 5

2.4.5 Biu Pareto ............................................................................................. 6

2.4.6 Biu nhn qu (Causes and effect diagrams) ......................................... 7

2.4.7 Biu kim sot (Control charts) ............................................................. 8

3 PHN TCH TNH HUNG ................................................................................ 10

3.1 Tnh hung 1: Phn tch tnh hung mt cng ty va v nh (SME) n 10

3.1.1 Gii thiu cng ty ...................................................................................... 10

3.1.2 Thc hin Lean .......................................................................................... 10

3.2 Tnh hung 2: Gim Lead Time vn chuyn ti mt cng ty phn phi thc phm. ......................................................................................................................... 14

3.2.1 Gii thiu v cng ty ................................................................................. 14

3.2.2 Thc hin Lean .......................................................................................... 15

3.3 Tnh hung 3: S dng Lean nhm xc nh lng ph ti mt cng ty may mc ti Bangladesh............................................................................................................ 17

3.3.1 Gii thiu v cng ty ................................................................................. 18

3.3.2 Thc hin Lean .......................................................................................... 18

4 THO LUN V VIC P DNG 7 CNG C THNG K TRONG LEAN 21

4.1 7 cng c c s dng nh th no? .............................................................. 21

4.1.1 Lu ....................................................................................................... 21

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4.1.2 Bng kim tra ............................................................................................ 22

4.1.3 Pareto ......................................................................................................... 22

4.1.4 Biu tn s ............................................................................................ 24

4.1.5 Biu nhn qu ....................................................................................... 24

4.1.6 Biu phn tn ........................................................................................ 25

4.1.7 Biu kim sot ...................................................................................... 26

4.2 Nhng kh khn khi s dng 7 cng c thng k? .......................................... 26

4.2.1 Kh khn chung ........................................................................................ 27

4.2.2 Kh khn ring .......................................................................................... 27

5 TNG KT ........................................................................................................... 30

6 TI LIU THAM KHO ......................................................................................iv

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DANH MC BNG

Bng 2.1 Cc dng biu . ............................................................................................. 8

Bng 3.1 Phn loi khuyt tt v ng gp ca n n tng khuyt tt. ...................... 12

Bng 3.2 Cc thng s cn thit t phm vi mt c mong mun. ................... 13

Bng 3.3 Tng thi gian lng ph do thao tc tha. ...................................................... 19

Bng 3.4 S liu v cc vn cng nhn gp phi trong qu trnh. ............................ 20

Bng 5.1 Cc cng c thng k s dng trong cc giai on ca Lean. ....................... 30

DANH MC HNH

Hnh 3.1 Biu Pareto v cc khuyt tt trong v ngoi qu trnh. ............................ 11

Hnh 3.2 Biu nhn qu ............................................................................................ 12

Hnh 3.3 Biu kim sot. .......................................................................................... 14

Hnh 3.4 Biu Pareto xc nh vn ln nht m khch hng than phin. ............ 15

Hnh 3.5 Biu Pareto xc nh nguyn nhn ln nht gy ra li Giao hng tr. ...... 16

Hnh 3.6 Biu phn tn th hin tng quan li vi than phin ca khch hng. .... 16

Hnh 3.7 Ma trn nhn qu. ........................................................................................... 17

Hnh 3.8 Lu quy trnh. ............................................................................................ 18

Hnh 3.9 Biu nhn qu phn tch nguyn nhn. ...................................................... 19

Hnh 3.10 Biu Histogram biu th d liu cc vn cng nhn gp phi. ........... 20

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1 T VN

Theo Basu (2001) v George (2002), hai thp k gn y chng kin p lc gia tng t khch hng v cc i th cnh tranh trong vic cung cp ngy cng nhiu gi tr da trn cht lng, kh nng vn chuyn nhanh hay chi ph sn xut thp (hoc l tt c) c trong lnh vc sn xut v dch v. iu ny khin cho, theo Womack v Jones (1996), Harry (1998), Basu (2001), Murmanet al. (2002), Sharma (2003),

Arnheiter v Maleyeff (2005), cc ngnh cng nghip dn chp nhn sn xut theo Lean (nhm tng tc p ng n hng v gim chi ph) nh mt phn ca chin lc tng th phn v ti a ho li nhun. V cc cng ty ln dn tin phong trong vic p dng Lean vo doanh nghip nh Toyota, Danaher Corporation, General Electric, Motorola, Honeywell, V cho ti nay, c rt nhiu doanh nghip p dng Lean vo doanh nghip ca mnh.

Tr v qu kh, trc Lean, c rt nhiu cng c ra i m mt trong nhng cng c c lc h tr cho qun l cht lng, vn l vn mun thu ca doanh nghip, chnh l 7 cng c thng k. 7 cng c thng k tht s v cng hu ch khi n c th c p dng vo hiu quy trnh, pht hin nguyn nhn gy nn khuyt tt cng nh h tr trong vic gii quyt v kim sot cc vn (theo Ved Parkash, Deepak Kumar, Rakesh Rajoria, 2013). V theo gio s Kaoru Ishikawa, Noriaki Kano, Karatshu, 99% cc vn v cht lng xy ra hng ngy ti doanh nghip u c th c gii quyt ng 7 cng c thng k.

Vy 7 cng c thng k h tr cho Lean nh th no? tr li cho cu tr li trn, bi bo co ny s dng phng php tip cn vn theo tnh hung v a ra kt lun.

2 C S L THUYT

2.1 Lean Manufacturing

2.1.1 Lean manufacturing l g

Theo Sandra Rothenberg v Frank Cost (2004), c rt nhiu cch nh ngha v Lean manufacturing, tuy nhin, Lean manufacturing (vit tt l Lean, tm dch l sn xut tinh gn), l mt trit l ly kim ch nam l gim thiu lng ph.

Theo Bruce D. Miller (2001), Lean l mt h thng cc nguyn tc, khi nim v k thut c thit lp vi mc tiu loi b lng ph v xy dng mt h thng sn xut hiu qu mang li cho khch hng: Chnh xc nhng g h cn, ng thi im h cn, theo ng s lng, ng s th t, khng hng hc, v chi ph thp nht c th.

Cn theo Jeffrey K. Liker (2005), sn xut Lean l mt trit l theo ui mc tiu gim tng thi gian hot ng k t lc nhn n hng cho n khi giao sn phm cho khch hng cui bng cch loi b lng ph. Lng ph l tt c nhng g khng lm tng gi tr theo quan im ca khch hng.

2.1.2 Cc trit l ca Lean

Theo James P. Wamack (1996), Lean bao gm 5 trit l:

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cao gi tr: im bt u ca t duy theo Lean chnh l gi tr. Gi tr ch c th c nh ngha i khch hng. V n ch c th c nh ngha l mt sn phm c th (hoc mt dch v, hay c hai) p ng c yu cu ca khch hng vi mt mc gi v ti mt thi im c th. Gi tr th c to ra bi ngi sn xut. ng trn quan im ca khch hng th gi tr chnh l l do m ngi sn xut tn ti. Bi vy, t duy theo Lean phi xut pht t vic nh ngha mt cch cn thn gi tr sn phm hoc dch v c th vi mt nng lc sn xut c th c th t c mc gi c th thng qua nhng hnh ng to nn gi tr.

Nhn bit dng gi tr: Khi nim dng gi tr m t ton b cc qu trnh, hot ng chuyn u vo thnh u ra ph hp. Vi cng mt u vo u ra, c th c v s dng gi tr v iu ny lm nn s khc bit gia cc t chc. C nhng t chc hot ng hiu qu, pht trin bn vng v cng c nhng t chc phi gnh chu qu nhiu lng ph di nhiu hnh thc, nng sut hot ng thp, dn n b o thi. Ni tm li, cc kt qu mnh yu, c mt ca t chc ph thuc phn ln vo dng gi tr. Mt dng gi tr c xem l hiu qu khi n loi b c cc lng ph v ti nguyn, di chuyn, thng tin, khng gian, thi gian, Qu trnh xy dng thnh cng mt dng gi tr l tng nh trn cn phi qua mt chng ng di, i hi s kin nhn v n lc ca nhiu ngi vi s h tr ca cc cng c, phng php thch hp.

Dng lin tc: Dng lin tc l mt khi nim lin h vi hot ng nhn din v loi b ro cn h thng, to c s cho s tin trin lin tc cc kt qu gt hi t qu trnh cung cp sn phm hay dch v. Ro cn h thng l tt c nhng g ngn cn h thng hot ng nhp nhng, lin tc, tn ti di nhiu hnh thc cc cp khc nhau. Ti mi mc pht trin ca t chc c nhng ro cn h thng c trng. Sau khi loi b ro cn pht trin mc cao hn, t chc li phi i din vi nhng ro cn mi. Do , nhn din v loi b ro cn h thng l hot ng c im bt u nhng khng c im kt thc, chng no t chc cn tn ti. N tn ti song song vi t chc v quyt nh tc pht trin ca t chc.

Ko khch hng: Nguyn tc khch hng ko c th l gii bng cm t sau: ch lm nhng g tht s cn thit. H thng ko l mt h thng cc ch th i t khch hng cui ngc ln trn, trong khng c t c th g c sn xut bi nh sn xut cho n khi c tn hiu v nhu cu ca khch hng cui. Cc d bo v doanh thu khng nh hng cho sn xut, thay vo , sn phm ch c sn xut khi c tn hiu v nhu cu ca khch hng. iu ny to iu kin khch hng ko nhng g h mong i, thay v sn xut y ra nhng sn phm khng cn thit.

S hon thin: Bc cui cng hon tt quy trnh thc hin doanh nghip Lean l theo ui s hon thin. Theo ui s hon thin ng rng s ci tin qu trnh khng bao gi c im kt thc v vic t c s gia tng v hiu qu hot ng c th lp i lp li. S minh bch, r rng ca thng tin trong sn xut, hay s tip cn khng gii hn cc d kin khc nhau l con ng quan trng nht hng ti s hon thin v n to ra mt mi trng d dng khm ph cc phng php tt hn to ra gi tr.

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2.2 Phng php DMAIC

Theo Nabhani v Shokri (2009), DMAIC (Define, Measure, Analyze, Improve,

Control) l mt bn ch ng thng dng trong Six Sigma nhm gii quyt vn c cu trc. N nh mt kim ch nam trong qu trnh ci tin thng qua vic tp trung cao vo tm nguyn nhn gc r trong bt k qu trnh no.

Theo Kwak v Anbari (2006), cc c im ca DMAIC nh sau:

Define: Xc nh yu cu v mong i ca khch hng, xc nh gii hn ca d n, xc nh qu trnh bng vic v lu kinh doanh.

Measure: o lng qu trnh lm hi lng khch hng, pht trin k hoch thu thp d liu, thu thp v so snh d liu nhn bit vn .

Analyze: Phn tch nguyn nhn gy nn khuyt tt v ngun gc ca dao ng, nhn bit s dao ng trong qu trnh, u tin cc c hi ci tin trong tng lai.

Improve: Ci tin qu trnh ngn chn s dao ng, pht trin cc gii php sng to v thc hin k hoch ci thin.

Control: Kim sot dao ng ca qu trnh lm hi lng khch hng, pht trin chin lc kim sot qu trnh ci tin, thc hin h thng ci tin.

2.3 S dng DMAIC trong Lean Manufacturing

Theo Cox (1999), hai c tnh quan trng ca Lean l loi b lng ph v hng n s hon ho. Cng vy, nh Na hani v Shokri (2009) kt lun, hai c tnh ny cng c trong Six Sigma. Do , tin trnh DMAIC c th c s dng cho khi thc hin Lean.

2.4 7 cng c thng k

Theo Bi Nguyn Hng v Nguyn Thu Qunh Loan (2011), 7 cng c thng k c trnh y nh sau:

2.4.1 Lu (FLOWCHARTS)

2.4.1.1 Khi nim

L cng c trc quan th hin qu trnh bng hnh nh, m t th t cng vic trong qu trnh to s nht qun.

2.4.1.2 ng dng

Hai dng lu chnh l: dng lu m t v dng phn tch.

Lu ch ra ci chng ta ANG LM

ch khng phi ci NGH RNG NN LM

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Dng m t bt u vi u vo v kt thc vi u ra. Chng c dng cung cp thng tin, v dng nh l mt hng dn d thc hin qu trnh sn xut.

Dng phn tch cung cp chi tit v s lng lin quan n cc thnh phn ca qu trnh c trnh u di dang k hiu (biu tng) ca qu trnh. Ngi ta thng dng lu dng phn tch so snh cc qu trnh vi nhau v a ra cch ci tin thch hp.

2.4.1.3 Li ch

Phc ha cc hot ng hoc cc cng on to ra sn phm/dch v theo mt trnh t nht nh t lc tip nhn u vo n khi kt thc qu trnh.

Gip lp k hoch d n, hun luyn, o to.

Cng c ci tin cht lng.

Nhn bit qu trnh cn ci tin.

Nhn bit cc bc khng cn thit/c vn trong mt qu trnh.

Cng c thng tin tt.

2.4.1.4 ngha

S dng chy rt hu ch nu bn mun truyn t mt qu trnh (hay mt phng hng) cho tt c mi ngi hn l cho cc thnh vin trong nhm. Biu ny h tr bn gii thch nhng im cn ci tin.

2.4.2 Phiu kim tra (Check sheets)

2.4.2.1 Khi nim

L cng c thu thp d liu c n ch yu gm cc con s ghi nhn v cc qu trnh.

2.4.2.2 ng dng

Kim tra l do sn phm b tr li:

Tm nguyn nhn gy ra khuyt tt.

Kim tra v tr cc khuyt tt.

Bng k trng cu kin khch hng.

Kim tra s phn b ca dy chuyn sn xut.

Phc tra cng vic kim tra cui cng (kim tra xc nhn).

2.4.2.3 Li ch

Phiu kim tra phn ln c s dng trong giai on hoch nh bi cc thnh vin trong nhm, nhng ngi c trch nhim lp k hoch cho hot ng ci tin/chng trnh/chin lc mi. H c th c s xc nhn nhanh chng rng tng ca h ang c thc hin, hay ni no cn ci tin d n i ng hng.

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2.4.2.4 ngha

L mt dng biu mu dng th thp v ghi chp d liu mt cch trc quan, nht qun v to iu kin thun li cho vic phn tch.

Lu : Phiu kim tra l mt cng c chi ph thp, d s dng c th cung cp cho nhm s nhn bit nhanh chng v mt qu trnh c ang hot ng theo k hoch hay khng. Phi m bo rng trc khi p dng Phiu kim tra, cc thnh vin trong nhm hiu c cc tiu ch ca h c nht qun khng?

2.4.3 Biu tn sut (Histograms)

2.4.3.1 Khi nim

L mt tm tt bng hnh nh v thng k ca d liu, di dng th tn s cc i lng o v th hin phn phi d liu.

2.4.3.2 ng dng

S dng theo di s phn b ca cc thng s ca sn phm/qu trnh. T nh gi c nng lc ca qu trnh (Qu trnh c p ng c yu cu sn xut hay khng?) L biu ct th hin tn s xut hin ca vn (Thu thp qua phiu kim tra).

== > Phng nga trc khi vn c th xy ra.

2.4.3.3 Li ch

Li ch ch yu ca phng php nay l to c mt hnh nh tng quan v bin ng ca cc d liu, mt hnh dng c trng nhn c t cc con s tng nh v ngha.

2.4.3.4 ngha

M t xu hng ca mt lng d liu ln dng n gin m khng lm mt bt c thng tin no. V bit c nhng tiu ch thng k nh: Gi tr trung nh, lch chun, bin thin,

2.4.4 Biu phn tn (Scatter diagrams)

2.4.4.1 Khi nim

Th hin mi quan h gia cc i lng bng th. Cc i lng c lp v ph thuc c th hin bng nhng im trn th (x,y).

Cc c trng ca biu phn tn:

Tng quan thun (ng bin) - mt bin tng th in kia cng tng.

Tng quan nghch (nghch bin) - mt bin tng cn in kia gim.

Khng tng quan - Khng c s nh hng t bin ny n gi tr ca bin kia.

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2.4.4.2 ng dng

Xc nh mi quan h d tnh gia hai b s liu c quan h vi nhau.

Pht hin v xc nh mi quan h gia hai tp s liu c lin h vi nhau.

2.4.4.3 Li ch

Biu phn tn l mt bc tranh rt khi qut v quan h v ch gip xc nhn s tn ti quan h v mi quan h l g. N a ra kt qu quan st v thng k bit c quan h ny mnh hay yu.

2.4.4.4 ngha

Thng qua biu phn tn cng gip chng ta so snh phng php hay kt qu gia qu trnh.

Biu phn tn th hin mi quan h gia cc c tnh ngha l s thay i ca mt c tnh c kh nng d o s thay i ca c tnh khc (nguyn tc c n chnh l phn tch mi lin h gia hai in s).

Lu : Biu phn tn l cng c rt mnh, tuy nhin chng ta thng s dng n sai mc ch. Biu ny nn c nhng ngi c hiu bit v sn phm/qu trnh, s dng v nh gi chng hn cc k s, gim st vin, cc nhn vin bo tr tht b nh my.

2.4.5 Biu Pareto

2.4.5.1 Khi nim

L mt dang biu thanh th hin t l phn trm cc yu t nhm xc nh nhng yu t no chim t l quan trng nht. Biu Pareto c xy dng da trn nguyn tc Pareto: 20% nguyn nhn to ra 80% kt qu.

2.4.5.2 ng dng

Phng php ny dng tm ra cch thc hiu qu nht ci tin, n gip ta xem xt vn no cn c ci tin trc tin, bng cch la chn mt trong nhiu vn . y cng l phng php phn on quyt nh chnh xc nguyn nhn no cn c x l, bng cch chn la mt trong nhiu ngyn nhn

2.4.5.3 Li ch

Li ch m t chc nhn c l s phn b ngun lc hiu qu vo vn quan trng nht t to ra c hi ci tin tt nht. N cng l mt cng c trao i thng tin hiu qu gip Lnh o cp cao v nhng khc hiu r ti sao bn u tin chn trin khai cc hot ng hin ti v kt qu mong i l g.

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2.4.6 Biu nhn qu (Causes and effect diagrams)

2.4.6.1 Khi nim

L th xng cc liu k nhng nguyn nhn c th c ca vn bit trc. Bao gm:

Biu nhn qu dng 5M

Li ch chnh

- Gip t chc v lin kt cc yu t

- Hnh thnh cu trc gip cho vic ng no nhm

- To iu kin cho mi ngi cng tham gia

- C th dng khi khng bit nhiu v qu trnh

Khuyt im:

- C th c qu nhiu nguyn nhn trong mt nhnh

- Thng hay b sa ly vo nhng chi tit

- D tr nn phc tp: i hi s tn ty v tinh thn kin nhn

- Khng thun li cho cc thnh vin cha quen vi qu trnh

Biu nhn qu theo qu trnh

Li ch

- C ci nhn xuyn sut qu trnh v cc yu t tc ng mi c qu trnh

- C th gip xc nh quyn hn theo chc nng i vi cc cng vic cn ci

tin

- Hun luyn cho cc thnh vin khng quen vi ton b qu trnh

Khuyt im

- D sa ly vo mt s nguyn nhn(nguyn vt liu hay o lng)

- Kh dng cho nhng qu trnh di, phc tp

- Nhng nguyn nhn ging nhau ca vn c th xut hin nhiu ln

Biu nhn qu phn tng

Li ch

- a ra nhng nhm nguyn nhn c th c ca vn gip nh hng gii

php

- Biu t phc tp hn

Khuyt im

- C th b qua nhng nguyn nhn quan trng

- C th gp khc khan khi xc nh nhm nh

- Cn bit nhiu nguyn nhn ca vn

- Cn c nhiu kin thc v sn phm v qu trnh

2.4.6.2 ng dng

Lit k cc nhn lm qu trnh sn xut b bin ng vt ra ngoi gii hn qui nh trong tiu chun. Xem xt cc cng on sn xut v kim tra s sch vn

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hnh theo s nhn qu pht hin cc yu t no c vn hnh cha ph hp vi tiu chun.

nh r nhng nguyn nhn no cn c iu tra trc tin.

Sau khi pht tho xong biu nhn qu, hy tho lun vi cc cn b c lin quan v vit cc kt qu vo biu xc nh cc yu t c tnh quyt nh.

Khi cuc tho lun dn n cc bt ng th hy quyt nh cc yu t c iu tra u tin bng cch biu quyt ly kin thng nht.

Vic xy dng biu nhn qu c tc dng tch cc trong vic o to v hun luyn cc b k thut v kim tra.

Li cun mi ngi suy ngh v cc cu hi: Nguyn nhn g gy nn s bin cht lng ? v Mi quan h gia cc nguyn nhn vi kt qu

tc ng nh th no n c tnh cht lng ?

C th s dng biu nhn qu cho bt k vn no. S nhn qu thy r tng nguyn nhn, nh vy ta c th xut cc gii php nhanh chng hn.

2.4.6.3 Li ch

Phn tch nguyn nhn v h qu (hoc phn tch xng c) cung cp mt dn gip bn ngh ra mi nguyn nhn c th c ca mt vn . N gip bn phn tch su sc hn v mt tnh hung bt k.

Gip chng ta hiu r vn mt cch r rng.

Gip chng ta hiu c mi quan h: bit c cc nguyn nhn chnh mt cch c h thng v mi quan h gia chng vi cc nguyn nhn cp nh hn nh hng ti qu trnh sn xut.

S dng biu nhn qu thc hin nhng ci tin khi cn thit.

S dng biu nhn qu nh l mt danh sch kim tra nhm nghin cu cc nguyn nhn v cc mi quan h tc ng.

2.4.7 Biu kim sot (Control charts)

2.4.7.1 Khi nim

L biu c mt ng tm ch gi tr trung bnh ca qu trnh v hai ng song song trn v di ng tm biu hin gii hn kim sot v kim sot di ca qu trnh c xc nh theo thng k.

Biu kim sot c phn chia ra thnh nhiu loi nh sau:

Biu x-R, biu x-Rs.

Biu P, biu Pn.

Biu U, biu C.

Bng 2.1 Cc dng biu .

Cc dng gi tr Tn biu

Gi tr lin tc -Biu X-R: Trnh by gi tr trung nh v rng ca n) -Biu d X-Rs: Trnh by gi tr o

Gi tr ri rc -Biu P: Trnh by t l li

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-Biu Pn: Trnh by s sn phm b li -Biu C: Trnh by s lng li -Biu U: Trnh by s lng li trn mt n v sn phm

2.4.7.2 ng dng

Biu kim sot cho thy s bin ng ca qu trnh sn xut hoc tc ng trong sut mt chu k thi gian nht inh. V th c s dng :

D on, nh gi s n nh ca qu trnh.

Kim sot, xc inh khi no cn iu chnh qu trnh.

Xc nh s ci tin ca mt qu trnh.

2.4.7.3 Li ch

c xem nh Mt chic ng h bo thc trong qu trnh thc hin cng vic. Bng cch xc nh cc nguyn nhn ngu nhin hay l nguyn nhn khng ngu nhin.

Khi qu trnh ang n nh, ta c th d bo t nht n s cn tip tc n nh trong khong thi gian k tip.

Khi qu trnh c cc nguyn nhn c bit ang gy ra s khng n nh v thay i ln c th nhn thy trn biu kim sot, ta phi tm cch loi b chng ngay t u.

Khi bit qu trnh ang n nh, iu s rt thun li cho cng nhn vn hnh qu trnh. iu ny th hin l nu tp s liu ri trong vng gii hn n nh th khng cn phi tin hnh bt c iu chnh no.

Nu qu trnh ang n nh, nu mun gim in dao ng ca qu trnh v lu di, phi thay i h thng qu trnh ch khng phi trng ch vo cc bin php qun l cng nhn iu hnh.

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3 PHN TCH TNH HUNG

3.1 Tnh hung 1: Phn tch tnh hung mt cng ty va v nh (SME) n

Tnh hung ny c dn t bo co ca Maneesh Kumar, Jiju Antony, Ritesh Kumar Singh, Manoj Kumar Tiwari v Daniel Perry (2006).

3.1.1 Gii thiu cng ty

Mt doanh nghip va (SME) n chuyn thit k v gia cng cc sn phm khun c. Cc khch hng chnh ca cng ty l cc nh my v kh, ngnh cng nghip t, cc nh sn xut my dt. Cng ty sn xut khong 250.000 n v sn phm khun c mi nm phc v cho cc nhu cu ca khch hng. Cc nhn vin lm vic trong ba ca mi ngy, mi ca 8 ting, v su ngy mt tun p ng nhu cu th trng.

Cng ty thng xuyn nhn c khiu ni t khch hng ca mnh trn vt nt trong cc ph kin t c sn xut bi cng ty. y l nguyn nhn chnh gy ra s khng hi lng ca khch hng. gi chn khch hng, nh qun l nhn ra tm quan trng ca vic loi b khng hiu qu hot ng v lng ph t t chc. Mc tiu ca t chc l gim lng ph do khuyt tt, chnh l gim cc khim khuyt trong sn phm, hng tn kho thnh phm, ph liu v chi ph lm li.

3.1.2 Thc hin Lean

3.1.2.1 Xc nh

Mt s bui ng no ca thnh vin trong nhm c tin hnh xc nh yu t quan trng i vi cht lng (CTQ), ting ni khch hng (VOC) u vo. Trong cuc hp cc vn ca n v c, kch thc ca vn , tc ng ca vn , c tho lun gia cc thnh vin trong nhm v n c r rng rng hu ht cc khiu ni ca khch hng lin quan n vt nt trong ph kin sn xut t ca cng ty.

c mt ci nhn su sc vo tnh trng hin ti ca cc n v c, nhm tin hnh s dng s dng gi tr (VSM).

3.1.2.2 o lng

Nhm nghin cu thu thp d liu ca sn phm b li trong 2 nm qua v xc nh cc qu trnh quan trng, ni cc khuyt tt ti a xy ra. xc nhn cc d liu lch s, cc thnh vin trong nhm quyt nh thu thp cc d liu ca sn phm b li trong 6 ngy sau sn xut t cc trm lm vic ca mnh. Cc d liu thu thp c phn tch ph hp vi cc d liu lch s, cho thy rng nhng con s khuyt tt c n t cc my c, hot ng mi (MC2), v vt gc (MC3).

Bc tip theo l xc nh tiu chun hiu sut da trn yu cu ca khch hng. Mt k hoch thu thp d liu c thnh lp tp trung vo cc u ra ca d n v cng thc hin cc bi tp thit lp tiu chun. Mt nghin cu o kh nng lp li v lp li (R & R) c tin hnh xc nh ngun gc ca s thay i trong h thng o

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lng v xc nh kch thch l chnh xc hay khng. Mt nghin cu c thc hin kim tra tnh chnh xc ca ng h o c s dng o cc c tnh cng nh kh nng ca ngi lao ng trong vic thc hin cc hot ng trn my tnh. Nghin cu o R & R thc hin trn h thng cho thy mt bin th 8,01%, trong ng rng cc h thng o lng l chp nhn c. Mt m thanh c vi cc c tnh o lng c, chng hn nh mt c l nhng g khch hng mun. Do , mc tiu cui cng ca nhm l tng mt c.

Cc khuyt tt trn mt n v (DPU) m cng ty chp nhn l 0,18. Cc c im k thut v mt c l 2,73 - 2,78g/cc. Tuy nhin, trung bnh ca cng ty li 2,45g/cc.

3.1.2.3 Phn tch

Cc thnh vin nhm nghin cu xc nh c nguyn nhn gc r ca cc khuyt tt v xc nh cc thng s qu trnh quan trng gy ra li ny. Trong su khuyt tt c, ao gm khng kh, thu nh l, v l kh xp l b khim khuyt bn trong khi ng lnh, foliations, v hn l khuyt tt b mt. Nhng khim khuyt ni b c hnh thnh trong qu trnh c nh rn li kim loi. Biu Pareto th hin trong hnh minh ha s ng gp t l phn trm ca cc khuyt tt trong v ngoi trong qu trnh ny. C th kt lun t bng v hnh di y khuyt tt ni b l kt qu ca mt c km.

Hnh 3.1 Biu Pareto v cc khuyt tt trong v ngoi qu trnh.

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Bng 3.1 Phn loi khuyt tt v ng gp ca n n tng khuyt tt.

c mt hnh nh r rng v cc thng s qu trnh nh hng n mt c, mt s nhn qu c xy dng v c th hin trong hnh 3.2.

Nguyn nhn v hiu ng th cho thy cc thng s qu trnh quan trng nht c nh hng n mt c l: vn tc piston giai on u tin, vn tc piston giai on th hai, nhit kim loi, thi gian np v p lc thy lc.

Hnh 3.2 Biu nhn qu

Tin hnh o c k hn, nhm thu c cc thng s cn thit t c phm vi mong mun ca mt c.

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Bng 3.2 Cc thng s cn thit t phm vi mt c mong mun.

3.1.2.4 Ci tin

Trong giai on nng cao, nhm nghin cu quyt nh thc hin mt th nghim c thit k xc nh cc thng s qu trnh quan trng nh hng n mt c cng vic s dng cc phn tch thng k nhm xc nh cc thng s ci t ti u.

Sau khi ci t ti u cc thng s qu trnh c xc nh, cc thnh vin trong nhm quyt nh trin khai h thng 5S v tng bo tr sn xut (TPM) thit lp mt mi trng sch s trong nh xng v cng gim thi gian nhn ri ca my v nhn vin trn sn ca hng.

3.1.2.5 Kim sot

Qun l quyt nh thc hin cc cng vic sau y ngn chn s xut hin ca cc khuyt tt khc cc giai on khc nhau ca sn xut:

- Kim tra cc khuyt tt giai on thit k s cc khuyt tt khng c

thng qua vo giai on sn xut.

- Phn tch FMEA, ph liu trong nh v lm li d liu, d liu kim tra, v

phn tch cc khiu ni ca khch hng c s dng xc nh cc vn

tim nng c th c gii quyt do nhm ln kim chng.

- i lin chc nng c thnh lp tho lun v sn xut v thit k nhng

vn m c th gy ra nhng sai lm / khuyt tt / tht bi.

- Chia s thng tin lin quan n hiu sut cng ty vi nhn vin ca mnh.

- o to nhng ngi vo ca hng tng lin quan n thng tin chi tit v cc

vn sn xut v cht lng cng nh cc hot ng nh gii quyt vn v

xy dng i ng.

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Hnh 3.3 Biu kim sot.

- S dng cc biu v th kim sot tng giai on x l gi cho cc

nhn vin nhn thc c hiu sut thi gian thc cc giai on tng ng

ca sn xut.

- ng vin v cng nhn nhn vin ng gp trong vic xy dng thc hnh tt

nht trong t chc.

3.2 Tnh hung 2: Gim Lead Time vn chuyn ti mt cng ty phn phi thc phm.

Tnh hung ny c dn t bo co ca Farhad Nabhani v Alireza Shokri (2009).

3.2.1 Gii thiu v cng ty

Tnh hung din ra trong mt cng ty phn phi thc phm nm pha ng Bc nc Anh. Cng ty ny c nhim v nhn v x l n hng, mua, tn tr v vn chuyn thc phm ch bin ng lnh v thc phm kh. Trong din bin mi nht, cng ty t tn kho ti mt ch mi ln hn v iu gy nn vn v vn

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chuyn. Hu qu ca iu ny l cng ty nhn c rt nhiu li phn nn ca khch hng vi s tht thot tim nng c tnh ln ti 100 ngn khch hng.

Nhm gim lng ph do than phin ca khch hng, cng ty tin hnh thc hin Lean Six Sigma.

3.2.2 Thc hin Lean

3.2.2.1 Xc nh

u tin, cng ty s dng cng c SIPOC xc nh khch hng hin ti v khch hng tim nng n trong ln bn ngoi cng ty, cc yu cu ca h v h thng vn chuyn cng nh u ra v u vo ca h thng ny.

Sau , cng ty cng s dng thm cng c Ting ni khch hng (VOC) kt hp vi Th im cn bng (Balanced Score Card) nhm tm hiu ting ni ca khch hng, tm hiu th no l mt h thng vn chuyn tt, mt h thng vn chuyn m khch hng mong mun. B phn chm sc khch hng ca cng ty tin hnh ghi li cc phn hi, s lng than phin t khch hng. u tin, cng ty s dng biu Pareto nhm xc nh vn ln nht m khch hng than phin l g. V chnh l vn giao hng tr vi 50% s than phin.

Hnh 3.4 Biu Pareto xc nh vn ln nht m khch hng than phin.

3.2.2.2 o lng

Cng ty tin hnh v li s quy trnh vi Giao hng tr l bin CTQ (Critical to Quality). Nh vy, nhm gim thiu lng ph do khuyt tt trong giao hng gy ra, cng ty thu thp d liu t phiu t hng, nng sut, li gp phi do khch hng than phin trong tng cng on trong bn tun gn nht.

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3.2.2.3 Phn tch

S dng biu Histogram v Pareto kt hp Process Sigma Level nhm xc nh c th hn nguyn nhn gy ra li Giao hng tr. Nh vy, theo biu , cng ty xc nh c nguyn nhn Thi gian ti hng trong kho l chim t trng cao nht.

Hnh 3.5 Biu Pareto xc nh nguyn nhn ln nht gy ra li Giao hng tr.

Tip tc phn tch bng biu phn tn kt hp phn tch hi quy vi 11 li Thi gian ti hng trong kho tng ng vi li than phin ca khch hng (l trc dc, biu th khong cch gia gi tr thc t v gi tr m khch hng mong i). Nh vy c th thy c l dch v c cung cp lun gp phi tnh trng khng p ng c mong i ca khch hng vi cng mt mc ngang nhau.

Hnh 3.6 Biu phn tn th hin tng quan li vi than phin ca khch hng.

Tip tc phn tch qua ma trn nhn qu (Cause & Effect XY), mt dng cng c mi ci tin t biu nhn qu. Bn cnh vic a ra cc nguyn nhn gc r nh tnh, kt hp vi cc s liu o lng c cho ra im s cho thy nguyn nhn gc r cui cng l g.

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Hnh 3.7 Ma trn nhn qu.

T bng, cng ty rt ra c c 6 vn chim s im rt cao l Sai st vo nhng dp l c bit, Thiu giao tip ni b, Phng php ti hng trong kho t, Thiu ht nhn vin, Cch b tr kho t, Sao lng trong chuyn hng.

tm c nguyn nhn gc r, cng ty tin hnh rainstorming v sau s dng cng c biu quan h (Affinity Diagram) xc nh. Cui cng, phng php tt nht c chn chnh l b tr li khng gian tn kho t hiu qu cao nht.

3.2.2.4 Ci tin

Bn cnh vic tin hnh b tr li khng gian tn kho, cng ty cn s dng cng c Poka Yoke nhm hn ch ti a kh nng pht sinh vn giao hng tr.

3.2.2.5 Kim sot

Cui cng, nhm kim sot, cng ty s dng biu kim sot v Process Sigma Level nhm nh gi qu trnh, kim sot chng u n.

3.3 Tnh hung 3: S dng Lean nhm xc nh lng ph ti mt cng ty may mc ti Bangladesh.

Tnh hung ny c dn t bo co ca Noman Sikder, Taslima Akther, Abdur Rahim, Raj Narayan Acharjee, Rifat Khan, Fazle Rabbi, Anup Saha (2013).

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3.3.1 Gii thiu v cng ty

Trc s cnh tranh n t cc cng ty Trung Quc v n , ngnh cng nghip may mc ti Bangladesh vp phi hng lot vn n t khng ch l nng sut nhng cn l cht lng sn phm. V tiu biu, ti mt cng ty may mc ti Bangladesh hin gp phi vn vi cc loi lng ph trong cng ty, c bit l ti quy trnh may v. Do , vn cp thit l gii quyt cc loi lng ph tn ti trong cng ty. Tnh hung ny s tin hnh xc nh lng ph do thao tc tha ca cng nhn.

3.3.2 Thc hin Lean

3.3.2.1 Xc nh

Cng ty tin hnh s dng lu nhm c ci nhn tng th v quy trnh trong cng ty.

Hnh 3.8 Lu quy trnh.

Bn cnh , cng ty cng tin hnh thng k li thi gian ca tng quy trnh v ca tng cng nhn di dng bng nhm xc nh khong thi gian b lng ph trong cng ty.

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Bng 3.3 Tng thi gian lng ph do thao tc tha.

3.3.2.2 o lng

Cng ty tin hnh thu thp d liu bng cch quan st v bm thi gian v cc thao tc tha ca cng nhn trn dy chuyn cch c th.

3.3.2.3 Phn tch

S dng biu nhn qu phn tch ra cc nguyn nhn c th c dn n vn lng ph do thao tc tha ca cng nhn.

Hnh 3.9 Biu nhn qu phn tch nguyn nhn.

Sau , t vic c bng d liu v s cng nhn gp phi cc vn dn n thao tc tha sau, cng ty tin hnh s dng cng c Histogram nhm c ci nhn trc quan hn v vn no ni tri nht.

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Bng 3.4 S liu v cc vn cng nhn gp phi trong qu trnh.

Hnh 3.10 Biu Histogram biu th d liu cc vn cng nhn gp phi.

Nh vy c th thy, ba vn u l ba vn ni cm khin cho cng nhn khng thoi mi v gy ra cc thao tc tha nhm ly li s d chu cho bn thn, nh vy dn n lng ph.

3.3.2.4 Ci tin

Tin hnh thit k li khng gian lm vic sao cho khoa hc (Ergology) v to s thoi mi cho cng nhn cc b phn trn c th.

3.3.2.5 Kim sot

Cng ty s dng biu kim sot theo di thi gian hon thnh cng vic ca cng nhn nhm c th d dng can thip kp thi khi c lng ph do thao tc tha xut hin tr li.

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4 THO LUN V VIC P DNG 7 CNG C THNG K TRONG LEAN

4.1 7 cng c c s dng nh th no?

4.1.1 Lu

4.1.1.1 ng dng trong LEAN

Lu l cng c gip cho mi ngi trong qu trnh c th hiu r qu trnh theo ng mt cch. T , n gip chng ta nhn din vn tn ti trong qu trnh v dn dn ci tin n. Quan trng hn, n thc s ph hp vi trit l tinh gn ca LEAN, thng qua vic hiu r v quy trnh, chng ta s n lc n gin ha ht mc, gim lng ph v lm ng ngay t u.

Trong LEAN, lu thng c s dng trong giai on Define xc nh qu trnh v thit k qu trnh gii quyt vn .

Bn cnh , mt ngha na ca Lu l to iu kin cho cc thnh vin trong doanh nghip c th lm vic mt cch ha hp vi nhau, ci thin thng tin gia nhng khu vc phng ban v sn xut thng qua vic cng nhau xy dng lu v hiu r trch nhim ca nhau.

s dng c Lu trong LEAN, doanh nghip phi m bo c nhng nguyn tc sau:

- Nhng ngi thch hp phi c tham gia vo vic xy dng lu . - Tt c thnh vin ca nhm d n LEAN u phi tham gia. - D liu lc no cng phi d tip cn i vi mi thnh vin. - Thi gian phi c phn phi y . - Mi ngi tham gia cng t nhiu cu hi cng tt.

(Da theo Bi Nguyn Hng v Nguyn Thy Qunh Loan (2011)).

4.1.1.2 Ti sao Lu c th lm c nh vy?

Theo Bi Nguyn Hng v Nguyn Thu Qunh Loan (2011): xc nh v cung cp t liu v mt qu trnh l mt c quan trng hng ti ci tin v i mi qu trnh. Bng cch v li v th hin ra nhng g ang lm, lu cung cp cho ngi xem nhng thng tin, hng dn v s lng v qu trnh sn xut, dch v. T vic hiu r quy trnh, chng ta c th d dng kim sot n.

Tip theo, lu c th gip chng ta n gin ha quy trnh thng qua vic ci tin khng ngng. Khi quy trnh c trnh by, ti hin li mt cch r rng, c h thng, ngi xem s c ci nhn bao qut, thay v ch bit ti nhim v ca mnh nh trc y, t , h s c th nhn ra vn , lng ph mt cch d dng hn. Bn cnh , lu gip lm gim lng ph thng qua vic lm ng ngay t an u, mi c nhn u c mt nhim v v tiu chun cho cng vic ca mnh.

im cui cng, lu c gip cho chng ta bit c mi cng on ca qu trnh, thay v ch tp trung vo nhim v ca bn thn, chnh v vy, cc nhn vin trong

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doanh nghip s phi hp n vi nhau, vn hnh nhp nhng cng vic, gip loi b nhng lng ph do ch i, thao tc tha.

Tuy nhin, cng phi cng nhn rng, lu l mt cng c khng thc s mnh. Trong 3 tnh hung phn tch trn, ngi ta thng s dng VSM hn l lu .

4.1.2 Bng kim tra


Trong l thuyt, bng kim tra l mt cng c chnh thu thp s liu. V khi p dng cho LEAN, cng dng ca bng kim tra vn c gi nguyn.

Bng kim tra c dng trong giai on Measure thu thp nhng d liu cn thit, t xc nh vn hoc lng ph. N c th dng phn loi li hay khuyt tt ca sn phm, hay ch ra v tr ca cc li thng xy ra trn hnh ca sn phm kim tra.

Bng kim tra gip chng ta m t thc cht mt s kha cnh ca qun tr bng d kin ch khng phi bng kin ch quan. T , chng ta c th c mt s hiu bit cng nh minh chng r rng hn v nhng lng ph hay vn tn ti trong doanh nghip.

4.1.2.2 Ti sao Bng kim tra c th lm c iu ny?

Ty cho tng loi d liu cn thu thp, bng kim tra c th s c thit k theo mt mu ring, lm sao cho r rng nht, trc quan v ph hp vi mc ch s dng nht. Chnh v th, c th ni, bng kim tra c th c s dng trong mi tnh hung thu thp d liu.

Theo Bi Nguyn Hng v Nguyn Thy Qunh Loan (2011) ng kim tra lun cha ng nhng thng tin m rng tm nhn cho chng ta, v vy khi c nhng s liu thu thp, chng ta cn lm cc c phn tch tip theo nhn dang lng ph hoc vn . Bng kim tra c cho l cng c cung cp s liu cho biu tn s v pareto.

4.1.3 Pareto


Pareto c s dng nhm mc ch phn bit mt vi nguyn nhn quan trng gy ra lng ph vi nhiu nguyn nhn khng quan trng khc. Khi c nhiu vn xy ra trn dy chuyn sn xut nh: khuyt tt, sai hng, khiu ni, tai nn ngi ta phn loi theo cc dng nh nguyn nhn, hin tng ty theo mc ch ca vic phn tch. Sau thit lp biu thay th cho cc d liu theo tm quan trng tm ra u l nhng gi tr quan trng nht.

T c s l thuyt, phn tch 3 case trn nhm rt ra mt kt lun rng Pareto s dng xc nh vn v xc nh nguyn nhn quan trng theo mc u tin t cao n thp v u c s dng giai on Analyze trong DMAIC.

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Ngoi ra, Pareto cn c s dng xc nh cc vn v thiu ht ng cch thu thp v so snh d liu trong giai on Measure.

thc hin Pareto trong LEAN, chng ta cn tin hnh theo quy trnh chun ha sau:

Bc 1: Thu thp d liu - nhm nghin cu xc nh nguyn nhn gc r ca vn v cc khuyt tt v tin hnh i thu thp d liu bng cc cng c check sheet, biu kim sot

Bc 2: Phn loi d liu thnh nhm - cc d liu c phn loi theo khuyt tt, ni sn xut, cng on, thi gian, nguyn vt liu, my mc, cng nhn vn hnh, phng php, thao tc

V d trong case nhiu li nh: khng kh, hn, l kh, xp, c nhm li thnh 5 nhm: khuyt tt ni b, lm ngui, phn lp, hn, khuyt tt khc.

Bc 3: Sp xp d liu v tnh ton tng hp s lng % tch ly - Cc loi khuyt tt c s lng ln nht v tr cao nht. Cc d liu c sp xp gim dn, ring d liu khc c sp xp dng cui.

Bc 4: Tin hnh v biu - Ct u tin chnh l dng li quan trng nht cn c ci tin ngay - Khuyt tt ni b (case trn). Sau khi ci tin, v tr quan trng ca dng li s thay i v dng li tip theo - lm ngui tr thnh quan trng nht cn phi ci tin tip theo. Da trn im gy ca ng cong tch ly, ta nhn thy hai dng li: Khuyt tt ni b v lm ngui ri vo vng quan trng cn ci tin trc v cc dng khc ri vo vng t quan trng hn. Nh vy cn c bin php khc phc cho nhng vn ny.

4.1.3.2 Ti sao Pareto c th lm c iu ny?

Theo Bi Nguyn Hng v Nguyn Thu Qunh Loan (2011), nguyn tc ca Pareto pht trin trn c s cc nguyn nhn ca vn c trng s khc nhau v kt qu c th c ci tin tt v d dng bng cch tp trung vo mt vi nguyn nhn quan trng. Bi v ngun lc ca cng ty c hn v chng ta khng th no khc phc c tt c cc nguyn nhn cng mt lc. Khc phc c 20% nguyn nhn quan trng c th gim thiu 80% lng ph lun l tiu ch m cc doanh nghip la chn. iu ny cng ging nh thay i vn ha trong cng ty, khng th mt lc m thay i hon ton, phi tin tng c mt i n s thay i hon ton.

Lu : Khi tip cn trit l LEAN th cc nguyn nhn theo th t u tin gy ra lng ph phi theo ng trn quan im ca khch hng. iu ny mi mang li bin php ci tin hiu qu. Cng theo Bi Nguyn Hng v Nguyn Thu Qunh Loan (2011), phn tch Pareto ch t quan im ca nh sn xut c th to ra mt lot cc th t u tin m b qua khch hng, c ngi s dng k tip ln ngi s dng cui cng. R rng, iu ny a ra mt bin php ti trong thip lp nhng u tin ci tin. Mi quan tm ca khch hng kh c th nh lng nhng khng nn b qua. Cu hi: C phi chng ta ang nh gi nhng iu quan trng i vi khch hng hay khng? phi tr li c.

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4.1.4 Biu tn s


Theo Bi Nguyn Hng v Nguyn Thu Qunh Loan (2011), biu tn s l mt cng c dng tm tt, phn tch v trnh by d liu. Li ch ch yu ca phng php ny l to c mt hnh nh tng quan v bin ng ca cc d liu. Bi v, nu chng ta c mt bng d liu di vi cc s liu ln ti con s trn 50, s tht kh khn khi nhn nh gi mt cch tng th (nh vi case s 3, c th d dng thy c vn m ngi cng nhn gp phi l g khi thy ba ct chnh lch hn so vi cc ct cn li trong biu ). Nh vy, cn c mt cng c c kh nng to nn mt bc tranh tng qut, mt bc tranh cho thy cc vn tp trung u l nhiu nht. V xa hn na, t biu tn s, c th tnh c trung nh v lch chun ca qu trnh cng cch phn b ca tp d liu nhm pht hin nhng gi tr vt khi tiu chun. Chnh bi v nhng gi tr vt khi tiu chun ny l cc khuyt tt trong sn phm, m theo Lean, y chnh l lng ph.

Chng hn, biu phn b thng c dng phn b i xng, hnh chung. Chnh v th, hnh dng, trn ca biu c dng nh gi kh nng ca qu trnh nhm pht hin ra nhng nguyn nhn c bit ang tc ng n qu trnh t a ra cc iu chnh, ci tin c th cho qu trnh. Hoc l, da trn biu tn s, c th so snh cc gi tr tiu chun vi phn b ca biu . a ra cc so snh t l ph phm so vi tiu chun; gi tr trung bnh c trng vi ng tm ca hai gii hn khng; hnh dng biu lch qua phi hay qua tri t a ra quyt nh lm gim s phn tn hay xt li tiu chun.

Biu tn s thng c s dng trong giai on Analyze. Chng ta thc hin xy dng biu ny bng cch o gi tr ln nht v nh nht, xc nh rng ca ct, in trn v in di cng gi tr trung tm ca biu . Sau tin hnh v ra theo tp d liu thu thp c t giai on Measure.

4.1.4.2 Ti sao biu tn s c th lm c iu ny?

Khuyt tt xut hin l mt trong nhng vn au u ca doanh nghip, v pht hin c xc sut cng kh nng phn l mt iu khng h d dng. Vi biu tn s, nh qun l c th xem chnh xc d liu c phn b theo hnh g, chng hn nh hnh chung ph hp vi l thuyt phn phi chun, t , trong Lean, c th p dng thm cc phn tch thng k lm r hn nng lc ca qu trnh nhm c nhng iu chnh cho ph hp (thng qua cc s liu v hnh dng phn phi, v gi tr trung tm, cc gii hn in cng lch chun, gi tr trung nh,).

4.1.5 Biu nhn qu


Biu nhn qu l mt cng c mnh c s dng suy ngh v trnh y mi quan h gia mt kt qu xy ra v nguyn nhn tim tng ca n. y l cng c c bit quan trng khi phn tch ci tin cht lng, tm nguyn nhn gy ra lng ph, t mi c th a ra cc in php khc phc phng nga.

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Biu nhn qu c dng nhiu trong giai on Analyze. Chng ta thc hin xy dng biu ny bng cch i ngc t lng ph (hoc hin tng xy ra) ln ra cc nguyn nhn (hay cc gii php tc ng cn thit). Cc c thc hin nh sau:

Bc 1: Xc nh vn m chng ta mun gii quyt v vit vo trong mt khi nm bn phi trang giy.

Bc 2: Tng hp kin xc nh nh cc nguyn nhn chnh gy ra vn c th c. Ch xem xt cc yu t c trng: h thng thng tin v d liu; mi trng lm vic; my mc thit b; nguyn vt liu; o lng; phng php; con ngi.

Bc 3: Suy ngh v tt c nhng nguyn nhn c th gy ra vn trong mi loi nguyn nhn chnh. tm ra cc nguyn nhn chng ta phi bit cch vn hnh p dng cch t 5 loi cu hi sau (5W-1H):

- Who (Ai): lng ph ny l do ai? Ai chu trch nhim?... - What (Ci g): Ci g xy ra? Ci g gy nn lng ph ny?... - Where ( u): Lng ph ny xy ra u? ... - When (Khi no): Lng ph ny xy ra khi no?... - Why (Ti sao): Ti sao li b xy ra? - How (Lm th no): Lm th no n xy ra? Khc phc lm sao?...

4.1.5.2 Ti sao biu nhn qu c th lm c iu ny?

Theo Bi Nguyn Hng v Nguyn Thu Qunh Loan (2011), thng tin l cha kha ci tin qu trnh. V thng qua vic phn tch 3 tnh hung trn, chng ta d dng nhn thy biu nhn qu c th gip chng ta t c mc tiu tm kim thng tin, m c th hn l nhng nguyn nhn gy nn vn .

Bn cnh , Bi Nguyn Hng v Nguyn Thu Qunh Loan (2011) cn cp, mt trong nhng thuc tnh gi tr nht ca biu nhn qu l n cung cp mt cng c tuyt vi h tr cho qu trnh ng no nhm. iu ny thc s quan trng trong vic p dng LEAN, v khi thc hin LEAN trong cng ty, i hi phi c s kt hp gia cc thnh vin trong nhm d n v gia nhm vi cc nhn vin khc c lin quan. T rt ra c thm mt kt lun, biu xng c thc s hu ch v tng thch vi LEAN. iu ny c th nhn thy d dng thng qua cc tnh hung a ra trn, bt k giai on tm hiu nguyn nhn no cng s dng ti cng c ny.

Cui cng, biu nhn qu c kh nng tm ra c nguyn nhn ct li thng qua biu C v E, t chng ta c th a ra nhng gii php hiu qu nhm khng cho nhng vn ny xy ra lp li.

4.1.6 Biu phn tn


Theo Bi Nguyn Hng v Nguyn Thu Qunh Loan (2011), biu phn tn th hin mi quan h gia hai c tnh, ngha l s thay i ca mt c tnh c kh nng d bo s thay i ca mt c tnh khc. Biu ny c s dng nhiu trong Analyze, ngoi ra, trong mt s trng hp, n c th c s dng trong giai on u ca Improve, l giai on th nghim. Bi v, thng qua biu phn tn, chng

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ta c th so snh phng php hay kt qu gia cc qu trnh t la chn cch lm no t hiu qu cao hn. Nh vy, khi ng dng vo trong Lean, chng ta c th lp ra c cc quan h gia cc yu t gy nn lng ph t iu chnh cho ph hp (nh trong case s 2, ngi ta lp biu phn tn gia li v s khng hi lng ca khch hng).

4.1.6.2 Ti sao biu phn tn c th lm c iu ny?

Khi c mt tp d liu, tht kh c th nhn ra quan h gia chng, mt mi quan h m khi c tnh ny bin i th c tnh kia cng in i theo mt chiu hng thun hay nghch hay khng quan h. V vy, biu phn tn chnh l mt cng c quan st, bi v n c kh nng din t mi quan h. Nh vo s phn b theo mt trn biu , ngi quan st s bit c tng quan gia chng v c cch tc ng cho ph hp vi mc ch.

4.1.7 Biu kim sot


Trong LEAN, biu kim sot thng c dng kim sot s n nh ca h thng, thng qua ci thin quy trnh v p ng nhu cu ca khch hng. Bn cnh , iu kim sot cn gip doanh nghip theo di v kim sot qu trnh ci tin. Biu kim sot thng c s dng trong giai on Control, tuy nhin, trong mt vi trng hp, n c dng trong giai on Measure vi mc ch thu thp v so snh d liu xc nh cc vn v thiu ht.

4.1.7.2 Ti sao biu kim sot c th lm c iu ny?

S d, iu kim sot c th mang li nhng li ch trn v iu kim sot c kh nng phn it gia bin i ngu nhin do bn cht v bin i khng ngu nhin do nguyn nhn c bit no gy nn. theo Bi Nguyn Hng v Nguyn Thy Qunh Loan (2011). Nu n tm ra nhng bin i khng ngu nhin, ta bit rng quy trnh khng n nh v phi loi b n.

4.2 Nhng kh khn khi s dng 7 cng c thng k?

Theo Michael Schaeffers, 7 cng c thng k th qu t phc v cho cng vic kim sot cht lng sn phm. Mc d chng mang n nhng cng c phc v cho qu trnh kim tra, d bo sn phm, song chng c nhng nhc im nht nh. Chng hn, 7 cng c ny c s dng vo lc vn c xy ra. Bn thn n khng c kh nng ci tin qu trnh cng nh cho mt du hiu thng bo khi trc trc xut hin. N ch c th lm nhim v thng tin rng sn phm tt giao.

Nh vy, nhng kh khn khi s dng 7 cng c thng k bao gm:

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4.2.1 Kh khn chung

Cn mt khong thi gian cho vic thu thp thng tin, s liu thc hin cho vic o lng v xy dng biu . V tt nhin, s liu c o lng phi l s liu c th i din c cho tng th, c chnh xc tt.

ng trn quan im ca Lean cc pht hin lng ph da trn nhng cng c thng k l nhng g m khch hng khng cn n. Nu ch ng trn quan im ca ca nh sn xut xc nh cc lng ph m b qua vai tr ca khch hng s dn n nhng bin php ti khi tin hnh ci tin.

p dng biu khng ti u. Khng nn lm dng vo biu tc l ty theo mc ch s dng m dng ng iu . Gii quyt vn khng cn phi dng mt lc 7 cng c thng k bi chng s mt thi gian gian thu thp d liu, tin bc, cng sc m hy da vo bn cht ca vn .

7 cng c thng k pht huy hiu qu vai tr ca mnh th cn phi c s hiu bit v s dng ng vi mc ch trnh nhm ln gia cc cng c. iu ny rt quan trng, bi s dng sai cng c trong nhng giai on khc nhau s chng mang li li ch m cn a ra nhng kt lun v bin php ci tin khng ph hp. Thit hi s l chnh cng ty mnh.

4.2.2 Kh khn ring

4.2.2.1 Lu

To ra v s dng lu l mt trong s nhng cng vic quan trng nht tin hnh cng vic kim sot ton b qu trnh sn xut v qun l. Cn c kin thc tng qut v cc vn v tin hnh sp xp chng thnh lu .

Nhiu cng ty vn cha hiu: Kim sot mt qu trnh, trc ht ngi ta cn phi hiu r qu trnh . H c gng gii quyt vn v ci tin cc qu trnh li khng nhn thc c ngay t u tm quan trng ca cc lu .

4.2.2.2 Histogram

Ba im thng mc phi khi s dng Histogram:

Vn s liu thu thp c: Trc khi a ra kt lun t s phn tch biu tn s, phi m bo s rng s liu i din c cho cc iu kin hin ti v tiu biu cho qu trnh. Nu s liu c (Qu trnh thay i sau khi s liu c ly) hay nu c bt k nghi ng g v s chch lch hay khng trn vn v s liu, tt nht l thu thp s liu mi m bo v cng c kt qu.

Vn kch thc mu: ng rt ra kt lun ch da vo mt mu nh (Di 40 s liu cho mt mu). Mu cng ln, phn b v hnh dng ca biu tn s v s liu ca mu s th hin tnh tin cy ca ton b qu trnh hay tp hp ca sn phm.

Din li biu tn s khng phi l kt lun m ch l gi thuyt: cc din gii cn c cng c bng phn tch b sung v cc quan st trc tip qu trnh dang kho st. Kt lun v din dch an u c th khng ng ngay c khi n c v hp l. Phi lun u t thi gian suy ngh nhng cch l gii khc cho dng phn phi t biu tn s.

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4.2.2.3 Pareto

Pareto s dng nhm mc ch tch it mt vi vn quan trng vi nhiu vn khng quan trng. Tuy nhin vic kt lun khng phi lc no cng u tin gii quyt cc vn quan trng.

Khch hng: Khng th to ra mt lot cc th t u tin theo quan im nh sn xut m b qua khch hng. Mc d mi quan tm ca khch hng kh c th nh lng nhng khng nn qua. Theo Lean, lng ph phi c da trn quan im ca khch hng ch khng phi cng ty. V vy, a ra quyt nh cui cng cn phi c xem xt c th hn na.

S o lng: nh ngha v khuyt tt thng khng r rng, v vy cc nhm Pareto c th c xc nh khng chnh xc.

Ch s: V mt k thut, khng phi lc no cng qua nhng vn khng quan trng. V d nh c vn tn sut xy ra t nhng chi ph tng ng ca n li cao v c th gy ra khng tha mn khch hng. Vic xc nh mt vn quan trng hay khng b ph thuc vo ch s dng la chn.

4.2.2.4 Biu kim sot

Theo Bi Nguyn Hng v Nguyn Thu Qunh Loan (2011), biu kim sot dng thuc tnh c th gip chuyn dch cc qu trnh ca cng ty hng ti mc khng c sai st. Tuy nhin, n khng cung cp nhng thng tin c th v cc nguyn nhn gy ra ph phm v khi phn trm ph phm tin ti khng, kch thc mu cng ln s c yu cu tm ra cc u ra ph phm. Chng hn nh, nu mt qu trnh ang to ra trung bnh mt ph phm trong mi triu n v c to ra, khi kch thc mu trung bnh cn tm ra mt ph phm l mt triu n v. Do iu kim sot dng thuc tnh tr nn khng hiu qu khi phn trm ph phm tin n 0.

4.2.2.5 Biu phn tn

Biu phn tn cn c gi l biu tng quan, iu th mi quan h gia hai i lng trong mi tng quan gia cc chui gi tr ca chng. Khi i lng X c gi tr thay i, biu ch ra s thay i tng ng ca i lng Y. Biu phn tn l mt bc tranh rt khi qut v quan h v ch gip xc nhn c tn ti hay khng s tng quan v tng quan l g. N a ra kt qu quan st v thng k bit c tng quan ny mnh hay yu. Khi s dng Biu phn tn nn cn thn nu mi tng quan l khng r rng, khi rt ra kt lun cng cn tht cn thn. Tt nht nn s dng cc phng php kim tra s tng quan khc nh gi quan h gia cc bin s nu khng rt ra c kt lun t Biu phn tn.

4.2.2.6 Biu nhn qu

Biu nhn qu l mt cng c rt hiu qu trong vic p dng tm ra nguyn nhn ct li ca vn , nhng cng c mt s kh khn khi s dng. Vic dng cng c ny cn phi thc hin ng no nhm. Nhm ny phi c kin thc, kinh nghim, v v tr trong t chc tng ng nhau, i v nu c s chnh lch trong 3 yu t ny th nhng g c chp nhn c xu hng nghing v kin ca ngi c kin

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thc, kinh nghim, v tr cao hn, v iu nhn qu ny s mang tnh ch quan. Mt kin khc, biu nhn qu l mt dng tp hp rt nhiu nguyn nhn c th c gy ra vn , nhng n khng phi l cc nguyn nhn gc r. V th cn phi kt hp nghin cu su hn rt ra kt lun ch khng nn kt lun ngay v d dn n sai lch trong phng php.

4.2.2.7 Check sheet

C nhiu dng phiu kim tra, tu theo mc ch kim sot, tuy nhin d c s dng dng check sheet no th cng tn rt nhiu thi gian v cng sc, v ngi thc hin phi lin tc theo di, khi c s kin xy ra th phi cp nht ngay vo check sheet. y l im khc bit gia check sheet v 6 cng c cn li.

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5 TNG KT

Theo Ved Parkash, Deepak Kumar, Rakesh Rajoria (2013), cc u im ca 7 cng c thng k l:

H tr cho cng vic ci tin quy trnh bng cch pht hin s dao ng.

H tr cho cng vic ci thin cht lng sn phm bng cch pht hin khuyt tt v nguyn nhn.

Gip tng kh nng cnh tranh cho doanh nghip thng qua vic gim kh nng sa sai, tng hi lng cho khch hng.

H tr cho vic gim cc loi lng ph trong doanh nghip.

Nh vy, khi p dng Lean trong doanh nghip, mt iu cn thit l nn s dng 7 cng c thng k h tr trong qu trnh lm Lean, c bit l trong vic gim lng ph cng nh l tng cht lng sn phm.

Mt cch tng qut, theo Ming-Tzong Wang, Hung-Da Wan, Hsing Yang Chen, Shi-Min Alex Wang, Szu-Chi Huang v Hsiang-Yun Lisa Cheng (2012), 7 cng c thng k u c th c s dng nh trong ng 5.1 di y. Tuy nhin, 7 cng c ny thng xuyn c s dng trong qu trnh loi b lng ph v ci thin cht lng sn phm ti cc giai on nh sau:

Giai on o lng: Check sheet.

Giai on phn tch: Biu nhn qu, biu Pareto, biu kim sot, biu phn tn v biu Histogram.

Giai on kim sot: Biu kim sot.

Bng 5.1 Cc cng c thng k s dng trong cc giai on ca Lean.

Giai

on

7 cng c thng k s dng trong cc giai on

Danh mc hot ng xut Vn Phng php v cng c xut

Define

Thit k qu trnh gii quyt vn .

Xy dng k hoch d n, v chn d n ph hp.

Xc nh qu trnh ng cch lp lu cc dng chy kinh doanh.

Qu trnh Lu

Measure

o lng quy trnh p ng nhu cu ca khch hng.

Gii quyt vn ca qu trnh n nh.

m o cht lng d liu.

Qu trnh Check sheet

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Xy dng k hoch thu thp d liu v h thng.

Thu thp v so snh d liu xc nh cc vn v thiu ht.

Thu thp d liu

Biu Pareto Biu C v E Biu xng c Biu kim sot Biu tn s

Analysis

Xc nh cch gim khong cch gia trnh hin ti v mc tiu mong mun.

Phn tch nguyn nhn ca cc khuyt tt v ngun gc ca s thay i.

Xc nh cc in i trong qu trnh.

Xc nh c hi u tin ci thin trong tng lai.

Nguyn nhn

gy ra khuyt tt v ngun gc ca s in i

Biu Pareto Biu phn tn Biu tn s

Improve

Xc nh, nh gi v la chn cc gii php ci thin.

Ci tin quy trnh loi cc vn .

Xy dng la chn thay th v thc hin k hoch ci tin.

Th nghim Biu xng c Biu phn tn Biu C v E

Control

Kim sot qu trnh in i p ng yu cu khch hng.

Pht trin mt chin lc theo di v kim sot qu trnh ci tin.

Thc hin nhng ci tin ca h thng v cu trc.

Th nghim Biu Pareto Biu kim sot Lu

iv

6 TI LIU THAM KHO

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