ThS. Trn Th Bch NhungLCH TRNH SN XUT

Nhng ni dung chnh:Sp xp cng vic ti uPhn cng cng vic cho cc myS GANTTS PERTLCH TRNH SN XUT

1. Sp xp cng vic ti u. Cng vic c t hng trc lm trc (FCFS) Cng vic phi hon thnh trc lm trc (EDD). Cng vic c thi gian thc hin ngn nht lm trc (SPT). Cng vic c thi gian thc hin di nht lm trc (LPT).

V d: C 5 cng vic A, B, C, D, E. thi gian sn xut v thi gian hon thnh nh sau:1. Sp xp cng vic ti u.

Tg hon tt TB 1 cng vic (Ttb) = Tng dng TG/ S cng vic1. Sp xp cng vic ti u.S CV TB trong h thng (Ntb) = Tng dng TG/ Tng TGSXS ngy tr hn TB (TRtb) = Tng ngy tr hn/ S cng vic

1. Sp xp cng vic ti u.KT LUN?

T NGHIN CU2. Phn cng cng vic cho cc my

3. Phng php s Gantt Do Henry Gantt tm ra nm 1910. Biu GANTT biu din mi tng quan gia hot ng v thi gian. Hot ng c lit k t trn xung di, cn thi gian c biu din t tri sang phi. V d: D n Vn phng i din

3. Phng php s Gantt Cc cng vic ca d n

K hiuTn hot ngTg bt uTG, tunALp v duyt k hochT u1BXc nh v tr t vn phngSau A3CChun b nhn sSau A2Do to nhn vin miSau C3Et mua trang thit b vn phngSau B3FLp t h thng h tngSau B2GB tr trang thit b v gSau E2HChuyn ti v khai trngSau G1

3. Phng php s Gantt S GANTT

t1t2t3t4t5t6t7t8t9t10ABCDEFGH

3. Phng php s Gantt

S GANTTu im:

Nhc im:

4. Phng php s PERT/CPM4.1 i nt v PERT/CPMCPM (Critical Path Method) v PERT (Program Evalution And Review Technique) l hai phng php xut hin cng lc, c lp vo nhng nm 50 TK20 nhm h tr qun l cc d n ln. CPM cn gi l phng php ng Gng do J.Kelly (Remington Rand) v R. Uolker (Du Pont) xy dng qun l cc d n ln trong ngnh ha thc phm.

4. Phng php s PERT/CPM4.1 i nt v PERT/CPMPERT l kt qu ca s hp tc ca cc chuyn gia thuc cng ty t vn Booz, Allen & Hamilton; tp on Lockheen Aircraft di s ch tr ca Hi Qun M nhm y nhanh tin thc hin d n ch to tn la Polais trong thi k chin tranh lnh.Hin nay hai phng php ny xch li gn nhau, b sung cho nhau.

4. Phng php s PERT/CPM4.1 i nt v PERT/CPMCPM v PERT c dng gii quyt cc vn sau: Biu din cc hot ng ca mt d n. nh gi thi gian thc hin tng cng vic v ton b d n. Xc nh thi gian ti thiu hon thnh d n Xc nh thi gian d tr c th. So snh chi ph thi gian, xc nh kh nng rt ngn thi gian ca d n.

4. Phng php s PERT/CPM4.2 Lp s PERTQuy tc lp s :

4. Phng php s PERT/CPM4.2 Lp s PERTQuy tc lp s :

4. Phng php s PERT/CPM4.2 Lp s PERTTrnh t lp s :

4. Phng php s PERT/CPM4.2 Lp s PERT

4. Phng php s PERT/CPM4.3 Xc nh ng gngng gng l .i vi cc s n gin ta c th nhanh chng pht hin ra ng gng. i vi s phc tp ta s dng thut ton sau:

4. Phng php s PERT/CPM4.3 Xc nh ng gngTrong thc t vi d n ln, khi lng cng vic ti hng nghn, ngi ta phi s dng mt s nguyn tc tnh ton tng qut.Tnh thi gian ES v EF (thun chiu) EFi = ESi + ti

4. Phng php s PERT/CPM4.3 Xc nh ng gng Ti im nt: Thi gian Esi+1 ca hnh ng tip theo s bng chnh thi gian EFi ca hnh ng trc ;Trng hp im nt l ni kt thc ca nhiu cng vic th Esi+1 ca hnh ng tip theo s bng gi tr ln nht Max(EFi) ca cc cng vic trc .

4. Phng php s PERT/CPM4.3 Xc nh ng gngTnh thi gian LS v LF (nghch chiu)LSi = LFi ti Ti im nt: Thi gian LFi-1 ca hnh ng trc s bng thi gian LSi ca hnh ng i.Trng hp im nt l ni bt u ca nhiu cng vic th Lfi-1 s bng gi tr nh nht Min(LSi).

4. Phng php s PERT/CPM4.3 Xc nh ng gngTnh thi gian d trS = LS-ES hoc S=LF-EF.

C hai cch biu din:M t s kin ti cc im nt: A-o-N (Activity on Node)M t s kin trn mi tn: A-o-A (Activity on Arrow)4. Phng php s PERT/CPM4.3 Xc nh ng gng

CPM tnh thi gian da trn cc d liu bit, nhng trng hp thi gian cho cc hnh ng khng th bit trc th phi lm th no?i vi mi hnh ng ta s a ra 3 cch nh gi v thi gian:4. Phng php s PERT/CPM4.4 Tnh xc sut hon thnh d n

Thi gian lc quan (to) l thi gian ngn nht Thi gian bi quan (tp) l thi gian di nhtThi gian c tnh hin thc nht (most likely time) tm l thi gian theo nh gi l gn vi thc t nht hon thnh hot ng.Thi gian thc t d kin (trung bnh) te chnh l g tr thi gian trung bnh ca 3 i lng to, tp, tm. 4. Phng php s PERT/CPM4.4 Tnh xc sut hon thnh d n

4. Phng php s PERT/CPM4.4 Tnh xc sut hon thnh d n

4. Phng php s PERT/CPM4.4 Tnh xc sut hon thnh d n

Tnh thi gian hon thnh d n M vn phng i din

Tnh thi gian hon thnh d n M vn phng i dinKt lun?. l ng gng vi thi gian d tnh l ..tun, xc sut chnh lch thi gian ny so vi thc t l .. tun.Nu mun bit xc sut d n ny hon thnh trong khong thi gian 17 tun l bao nhiu th ta s lm nh th no?

Tnh thi gian hon thnh d n M vn phng i din tm c xc sut hon thnh d n trn trong vng 15 v 17 tun ta cn:Z = (thi hn thi gian d kin)/ lch chun = (T-Tep)/ pTra bng ng vi gi tr z ta s tm c gi tr xc sut tng ng.

Tnh thi gian hon thnh d n M vn phng i dinVi d n M vn phng ta c: Vi T = 17 tun, z = 0.57 Tra bng 4, xc sut hon thnh d n l 71.57%.

Tnh thi gian hon thnh d n M vn phng i din99% d n c hon thnh trong my tun.

Tnh thi gian hon thnh d n M vn phng i din20 tun

4.5 ng dng PERT qun tr chi ph-thi gian thc hin d nNguy c khng hon thnh ng tin l nguy c thng trc ca cc d n.Cch lm thng dng l huy ng thm ngun lc, ng ngha tng chi ph.Rt ngn thi gian m bo chi ph l ch hng ti ca cc nh qun l.Chi ph ca t chc SX chia lm hai loi:Chi ph nh mc: c d tnh thc hin cc cng vic.Chi ph xc tin: chi ph tng thm rt ngn thi gian hon thnh cng vic.

Cc bc s dng PERT/CPM rt ngn thi gian thc hin d nXc nh chi ph d tnh cho tng cng vic trn 1 n v thi gian.Xc nh chi ph xc tin tng ng.Sp xp chi ph xc tin theo trnh t t thp n cao.Lp biu PERT/CPM tm ng gng.Bt u bng nhng cng vic nm trn ng gng. Tin hnh rt ngn thi gian t cng vic c chi ph xc tin thp nht, nh lun lun so snh vi chi ph d kin tng ng.

Cc bc s dng PERT/CPM rt ngn thi gian thc hin d nXc nh li ng gng mi sau khi thc hin rt gn.Tip tc rt ngn thi gian n khi no chi ph xc tin vt qu chi ph d kin tnh trn cng mt n v thi gian th dng li. Lp bng tng kt thi gian rt ngn v chi ph xc tin tin rt ra kt lun.

S dng PERT/CPM rt ngn thi gian thc hin d n M vn phngBc 1 v 2. Lp bng s liu v chi ph d tnh v chi ph xc tin.

S dng PERT/CPM rt ngn thi gian thc hin d n M vn phngBc 3. Sp xp chi ph xc tin theo th t t thp n cao.

S dng PERT/CPM rt ngn thi gian thc hin d n M vn phngBc 4. Dng PERT/CPM lp s mng v xc nh ng gng ( lm).Bc 5. Tin hnh rt ngn thi gianBt u t cng vic e (trn ng gng) so snh hai loi chi ph rt xung 1 tun ng gng cn 9 tun.Tip tc rt ngn cng vic g (trn ng gng) xung 1 tun, ng gng khng i, thi gian cn 8 tun.

S dng PERT/CPM rt ngn thi gian thc hin d n M vn phngBc 5. Tin hnh rt ngn thi gianTip tc rt ngn ln th 3. Cng vic B cng nm trn ng gng, nhng c chi ph xc tin cao hn chi ph nh mc, v l thuyt cng vic khng nn rt gn na.

S dng PERT/CPM rt ngn thi gian thc hin d n M vn phngBc 8. Lp bng tng kt.Da vo bng ta thy, d cng vic b c chi ph xc tin cao hn nh mc nhng ta vn c th tip tc rt ngn c thi gian, tng chi ph xc tin vn nh hn tng chi ph nh mc tit kim c t cc cng vic rt gn trn.