Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr115 BI 7: HOCH NH NGUYN VT LIU V QUN TR HNGD TR Ni dungMc tiu -Thc cht, ni dung v vai tr ca hng d tr. -Cc phng php qun tr hng d tr. -Thcchtcahochnhnhucu nguyn vt liu. -Kthutlpkhochnhucunguynvt liu. -Hiu r v hot ng d tr v lp k hoch nguyn vt liu. -Nmrvckhnngngdngcc phng php v k thut qun tr hng d tr v lp k hoch nguyn vt liu. Thi lngHng dn hc -6 tit. -Nm r cc cng thc trong bi hc. -Thc hnh cc bi tp cui. -Thamkhomtsdngbitpkhcc lin quan ti bi hc. Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr116 TNH HUNG DN NHP Tnh hung: La chn sn xut Doanh nghip Hng H sn xut cc loi bn gh theo cc n t hng ca khch hng. Do hnchbidintchnhxng,nhkhotrongkhisnphmcacngtykhadngv chng loi nn cng ty c chnh sch sn xut ng thi im. Hin nay cng ty ang nhn c mt n t hng sn xut 1.000 chic bn v phi tr hng cho khch hng trong vng 3 thng na. Di y l m phng v kt cu ca chic bn, thi gian sn xut cc chi tit. Cu hi Bn s c quyt nh nh th no v thi gian sn xut sao cho vn cung ng kp thi nhng c chi ph d tr thp nht? F Chn bn (4) 3 tun D Thanh ging ngn (2) 3 tun X Chic bn 1 tun E Thanh ging di (2)5 tun C Mt bn (1) 3 tun B Lp rp khung (1) 1 tun Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr117 7.1.Hoch nh nguyn vt liu7.1.1.Thc cht v vai tr ca hoch nh nhu cu nguyn vt liu 7.1.1.1.Khi nim hoch nh nhu cu nguyn vt liu Nguynvtliulmttrongnhngyutuvocbitquantrngivimt doanh nghip. Vic hoch nh chnh xc v qun l tt ngun nguyn vt liu s gp phnmbosnxutdinranhpnhng,nnh,tha mn nhu cu ca khch hng trong mi thi im vlbinphpquantrnggimchiphsnxut,h gi thnh sn phm.i vi cc doanh nghip sn xut, c bit cc doanh nghip sn xut nhiu chng loi sn phm th vic xc nhnhucuvdtrnguynvtliunhhngrt nhiu n chi ph sn xut. sn xut mi loi sn phm li i hi phi c mt s lng cc chi tit, b phn v nguyn vt liu rt a dng, nhiu chng loi khc nhau, thmvo,lngnguynvtliucnsdngvonhngthiimkhcnhaul khc nhau. V vy, vic lp k hoch chnh xc nhu cu nguyn liu, ng khi lng v thi im l mt vn khng h n gin, i hi nh qun tr phi tnh ton sao cho nguyn vt liu phi y , kp thi vi chi ph nh nht. Trong qun tr hng d tr ngi ta thng hay ni n 2 dng nhu cu lnhu cu clpvnhucuphthuc.Nhucuclplnhucuvnhngsnphmcui cng hoc cc chi tit, b phn khch hng t, n c xc nh thng qua cng tc d bo hoc da trn nhng n hng. Trong khi , nhu cu ph thuc l nhng nhu cu to ra t cc nhu cu c lp, n c tnh ton t qu trnh phn tch sn phm thnh cc b phn, chi tit v nguyn vt liu. V vy vic hoch nh nhu cu nguyn vt liu chnh l vic lp k hoch i vi nhu cu ph thuc. Hoch nh nhu cu nguyn vt liu l mt ni dung c bn ca qun tr sn xut c xy dng trn c s tr gip ca k thut my tnh c pht hin v a vo s dng lnutinMvonhngnm70.CchtipcnMRPlxcnhlngdtr nguyn vt liu, chi tit b phn l nh nht, khng cn d tr nhiu, nhng khi cn sn xut l c ngay. iu ny i hi phi lp k hoch ht sc chnh xc, cht ch i vi tng loi vt t, i vi tng chi tit v tng nguyn liu.Ngi ta s dng k thut my tnh duy tr n t hng hoc lch sn xut nguyn vt liu d tr sao cho ng thi im cn thit. Nh s m rng ng dng my tnh vohotngqunlsnxut,phngphpMRPgipchoccdoanhnghip thc hin c cng tc lp k hoch ht sc chnh xc cht ch v theo di cc loi vt t, nguyn liu chnh xc, nhanh chng v thun tin hn, gim nh cc cng vic tnhtonhngngyvcpnhtthngtinthngxuyn,mbocungcpngs lng v thi im cn p ng. Phng php hoch nh nhu cu nguyn vt liu t ra rt c hiu qu, v vy n khng ngng c hon thin v m rng ng dng sang cc lnh vc hot ng khc ca doanh nghip. Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr118 -Mt s phng php hoch nh nhu cu nguyn vt liu chnh ch yu l: oMRP(MaterialRequirementPlanning)haycngilMRPImcchllp k hoch sn xut khng xt n nng lc sn xut, coi nng lc sn xut ca doanh nghip l v hn. oMRPII(MaterialResourcePlanning)raicuinhngnm70trncs MRPIciuchnhbngcchabinsnnglcsnxutcadoanh nghip vo m hnh. oMRPIII:phttrinMRPIIbngccharanhngchngtrnhphnmm chuyndngchomtsloihnhdoanhnghipvimcchkimsottan b cc ngun lc ca doanh nghip trong k hoch ha sn xut. -Qua ng dng v trin khai thc t ngi ta thy c nhng li ch ca MRP nh sau:op ng nhu cu nguyn vt liu ng thi im, khi lng v gim thi gian ch i. oGimthiulngdtrmkhnglmnhhngnmcpngv phc v khch hng. oNng cao kh nng s dng mt cch ti u cc phng tin vt cht v lao ng. oTo s tha mn v nim tin tng cho khch hng. oToiukinchoccbphnphihpchtch,thngnhtvinhau,pht huy tng hp kh nng sn xut ca doanh nghip. oTng hiu qu ca hot ng sn xut kinh doanh. 7.1.1.2.Cc yu cu trong ng dng MRPHoch nh nhu cu nguyn vt liu em li li ch rt lntrongvicgimmcdtrtrongqutrnhch bin,mtkhcnduytr,mboynhucu nguyn vt liu ng thi im. MRPc hiuqucnthc hin nhng yu cu v iu kin sau: -CchngtrnhphnmmMRPvhthng my tnh tnh ton v lu tr thng tin; -o to cho i ng cn b hiu r v MRP v c kh nng ng dng c n; -Nm vng lch trnh sn xut, m bo chnh xc v lin tc cp nht v lch trnh snxut.Lchtrnhsnxutchobitthiim,khilngvchngloisn phm hoc chi tit cui cng cn c. S liu ny c th ly t cc n t hng, d bo hoc yu cu ca kho hng d tr theo ma v; -Chthngdanhmcnguynvtliu.Bngdanhmcnguynvtliuldanh sch ca tt c cc b phn, chi tit, nguyn vt liu to ra mt sn phm hoc chi tit cui cng. Mi loi sn phm s c bngdanh mc nguyn vt liu ring; -C h thng h s d tr nguyn vt liu hon chnh. y l h s lu tr nhng thngtinvtnhhnhchitit,bphn,nguynvtliunhtngnhucu,lng tipnhntheotinvdtrsnc.Ngoiracncnhngthngtinvnh cung ng, thi gian thc hin n hng v kch c l hng, nhng n hng b hu Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr119 vnhngsckhcCnggingnhdanhmcnguynvtliu,hsdtr nguynvtliulunciu chnhvcpnhtchnghnnhnhngthayi v d tr sn c, thi gian thc hin, thi hn hon thnh; -Phi m bo chnh xc v bo co hng tn kho. Doanh nghip cn m bo cc bo co tn kho phi chnh xc v l yu t quyt nh vic hoch nh lng nguyn vt liu chnh xc; -Bit thi gian cn thit cung ng hoc sn xut nguyn vt liu v phn b thi gian cho mi b phn cu thnh. Cc nh qun tr cn nm vng thi im ngi tiu dng cn sn phm. T thi im nh qun tr phi xc nh c thi gian ch i, di chuyn, sp xp, chun b v thc hin cho mi b phn cu thnh sn phm. Sau tnh ton v phn b thi gian pht lnh sn xut hoc cung ng kp tr hng ng tin . 7.1.2.Phng php MRP trong hoch nh nhu cu nguyn vt liu XydngMRPbtuitlchtrnhsnxutivinhucuclp(snphm cui cng) sau chuyn i thnh nhu cu v cc b phn, chi tit v nguyn vt liu cn thit trong nhng giai on khc nhau. MRP tnh s lng chi tit, b phn trong tnggiaionchotngloisnphmtrongmiquanhchtchvilngdtr hin c v xc nh chnh xc thi im cn pht n hng hoc lnh sn xut i vi tng loi chi tit, b phn . MRP tm cch xc nh mi lin h gia lch trnh sn xut, n t hng, lng tip nhn v nhu cu sn phm. Mi quan h ny c phn tch trong khong thi gian t khi mt sn phm c a vo phn xng cho ti khi ri phn xng chuyn sang b phn khc. xut xng mt sn phm trong mt ngy n nh no , cn phi sn xut cc chi tit, b phn hoc t mua nguyn vt liu, linh kin bn ngoi trc mt thi hn nht nh.Qu trnh xc nh MRP c tin hnh theo cc bc sau: -Bc 1. Phn tch cu trc sn phmNhtrncp,phngphphochnhnhucunguynvtliuctin hnh da trn vic phn loi nhu cu thnh nhu cu c lp v nhu cu ph thuc. Nhu cu c lp l nhu cu v sn phm cui cng v cc chi tit b phn khch hng t. Nhu cu c lp c xc nh thng qua cng tc d bo hoc da trn nhngn hng. Nhu cu ph thuc l nhng nhu cu to ra t cc nhu cu c lp, n c tnh ton tccqutrnhphntchsnphmthnhccb phn, chi tit v nguyn vt liu. tnh tng nhu cu ph thuc, cn tin hnh phn tch cu trc ca snphm.CchphntchdngtrongMRPls dngktcuhnhcycasnphm.Mihng mc trong kt cu hnh cy tng ng vi tng chi titbphncuthnhsnphm.Sdngktcu hnh cy c nhng c im sau: oCp 0 l cp ng vi sn phm cui cng. C mi ln phn tch thnh phn cu to ca b phn l ta li chuyn t cp i sang cp i + 1. oMi lin h trong s kt cu: l nhng ng lin h gia hai b phn trong s kt cu hnh cy. B phn trn gi l b phn hp thnh v b phn Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr120 di l b phn thnh phn. Mi lin h c ghi km theo khong thi gian (chu k sn xut, mua sm...) v h s nhn. S lng cc loi chi tit v mi lin h trong s th hin tnh phc tp ca cu trc sn phm.oSn phm cng phc tp th s chi tit b phn cng nhiu v mi quan h gia chngcngln.qunltheodivtnhtonchnhxctngloinguyn vt liu, cn phi s dng my tnh h thng ha, m ha chng theo s cu trc thit k sn phm. V d 1: sn xut ra mt chic bn, ngi ta m t chi tit nh sau : Cncvohnhvtrntacthmphngbngsdiy,snphmhon chnh (chic bn) c ghi cp 0 trn nh ca cy. Sau l nhng b phn cn thitlprpthnhsnphmhonchnhcp1.Saumibphnnyli c cu to t nhng chi tit khc v cc chi tit ny c biu din bc cp 2. C nh vy tip din hnh thnh cy cu trc sn phm nh sau: Theo nguyn tc ny tt c cc b phn, chi tit c chuyn v cp thp nht. Nh tit kim c thi gian v to ra s d dng trong tnh ton. N cho php ch cn tnh nhu cu ca b phn, chi tit mt ln v xc nh mc d tr i vi chi tit, b phn cn sm nht ch khng phi vi sn phm cui cng cp cao nht. -Bc 2. Xc nh tng nhu cu v nhu cu thc t Tng nhu cu chnh l tng s lng d kin i vi loi chi tit hoc nguyn vt liutrongtnggiaionmkhngtnhndtrhinc.Tngnhucuhng mc cp 0 c ly lch trnh sn xut. i vi hng mc cp thp hnth tng nhucuctnhbnglngnhngphtratheokhochcacptrc nhn vi h s nhn ca n (nu c). Chn bn Thanh di Thanh ngn Mt bn Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr121 Nhucuthctllngnguynvtliucnthittrongtngkhongthigian nht nh v c xc nh nh sau: Nhu cu thc t=Tng nhu cu-D tr hin c + D tran ton +S ph phm cho php Trong :Dtr sn c = Lng tip nhn theo tin + D tr cn li ca k trc. D tr sn c l tng d tr ang c thi im bt u ca tng thi k. D tr sn c theo k hoch l s lng d tr d kin, c th c s dng tha mn nhu cu ca sn xut.Lngtip nhnltng s b phn, chi tit a vo sn xut nhng cha hon thnh hoc l s lng t hng mong i s nhn c ti im bt u ca mi giai on. nhngphtratheokhochltngkhilngdkinkhochthng trong tng giai on. Lnh ngh phn nh s lng cn cung cp hay sn xut tha mn nhu cu thc. Lnh ngh c th l n t hng i vi cc chi tit, b phn mua ngoi vllnhsnxutnuchngcsnxuttidoanhnghip.Khilnghng havthigiancalnhnghcxcnhtrongnhngkhoch.Ty theo chnh sch t hng c th t theo l hoc theo kch c. t hng theo l l s lng hng t bng vi nhu cu thc t.thngtheokchclslnghngtcthvtnhucuthcbngcch nhn vi mt lng c th hoc bng ng lng yu cu trong thi im . Bt k lng vt no u c b sung vo d tr hin c ca giai on tip theo. -Bc 3. Xc nh thi gian pht lnh sn xut hoc n hng theo nguyn tc tr li t thi im sn xut.Khicungcp,snxutccchitithocsnphm,doanhnghipsmtthigian chovicchi,chunb,bcd,snxut.Do,bitthiimcncsn phmpngnhucukhchhng,doanhnghipphitnhngclixcnh khong thi gian cn thit hon thnh tng chi tit hoc sn phm. Thi gian phi t hng hoc sn xut c tnh bng cch ly thi im cn c chi tit sn phm tr i khong thi gian cung ng hoc sn xut cn thit cung cp ng lng hng yu cu .Theovd8,thigiancnthitcungcphocsnxutccchititbphn c cho nh sau: Chi titK hiuCp sn phmTun Chic bn A01 B khungB12 Mt bnC13 Thanh diE21 Thanh ngnF21 Chn bnG22 Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr122 Ta c s cu trc sn phm theo thi gian sau y: Tun 1Tun 2Tun 3Tun 4Tun 5Tun 6 Mua G Sn xut E Sn xut F Lp rp B MuaC Lp rpchic bn Kt qu ca qu trnh hoch nh nhu cu nguyn vt liu, linh kin c th hin trong biu k hoch c dng sau: Tun0123456 Hng mc Tng nhu cu Lng tip nhn theo tin D tr sn c Nhu cu thc Lng tip nhn n t hng theo k hochLng n hng pht ra theo k hochLng tip nhn t hng theo k hoch l s lng nhng chi tit, nguyn vt liu mong mun nhn c ti u k. i vi t hng theo l, lng nguyn vt liu ny s bng nhu cu thc t. i vi t hng theo kch c, lng nguyn vt liu ny s vt qu nhu cu thc t. Lng nguyn vt liu vt qu nhu cu thc t s c cng vo lng d tr sn c ca giai on ti. Lng n hng pht ra theo k hoch l khi lng d kin t ra trong tng giai on. N c tnh bng lng tip nhn t hng theo k hoch c xt ti yu t thigianthchin(thigianthchinlkhongthigiandkinktthc mtcngvicno).Lngnhngnysccoiltngnhucuticp thp hn trong chui sn xut. Vd2:Mtcngtysnxutgnhnchain thnglmcnhca: 150 chic sgiao vo tun th 5 v 150 ci vo tun th 8. Mi cnh ca u gm 4thanhgvhaikhung.Ccthanhgcsnxutticngtymt1tunv khung g s c mua ngoi vi thi gian cung ng l 2 tun. Sau khi c y thanhgvkhungca,cngtysphitinhnhlprpcnhcamt1tun. Doanhnghipclchtipnhnvotun1l100thanhgv50khungg.Hy xc nh s lng v thi gian biu ca lng pht ra theo n hng k hoch p ng c nhu cu trong nhng iu kin sau: 1. Lng t hng theo nhu cu thc t 2. Lng t theo kch c l 200 khung g v 100 thanh g. Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr123 Hng dn: u tin cn xc nh cu trc ca sn phm Xc nh lch trnh sn xut,tng nhu cu v nhu cu thc t nh trong bng sau: 1. i vi trng hp t hng theo nhu cu thc t: Tun012345678 S lng200200 Tun 012345678 Tng nhu cu200 200Lng tip nhn theo tin D tr hin c0 0 0 0 000 0Nhu cu thc0 0 0 0 20000 200Lng tip nhn t hng theok hoch 0 0 0 0 20000 200Cnh ca Thi gian lp rpmt 1 tun Lng n hng pht ra theok hoch0 0 0 200 00200 0i vi tng nhu cu ca cch ca s ly t lch trnh sn xut l 200 tun th 5 v 200 tun th 8. D tr hin c v lng tip nhn theo tin khng c nn nhucuthctsbngtngnhucu.ivithngtheonhucuthctth lngtipnhnthngtheokhochbngngnhucuthct.Lngn hng pht ra theo k hoch s phi li li 1 tun.Tun 012345678 Tng nhu cu400 400Lng tip nhn theo tin 100D tr hin c 100 100 100 000 0Nhu cu thc 0 0 0 300 00400 0Lng tip nhn t hng theo k hoch 0 0 0 300 00400 0Khung ca Thi gian cung ngmt 2 tun Lng n hng pht ra theok hoch0 300 0 0 40000 0Tngnhucukhungcaschnhllngnhngphtratheokhochca cnh ca nhn vi h s nhn l 2. Lng tip nhn theo tin ca tun 1 l 100khungca,vvydtrhinccatun2sl100khungca.Nhucu thc t s l 400 100 = 300 v lng n hng pht ra theo k hoch phi li li Cnh ca Khung (2)Thanh g (4) Cp 0Cp 1 Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr124 2 tun. i vi cc thanh g, khi xt n hng 200 cnh ca cng cn phi c 800 thanh g vo u tun th 4. y do c 50 thanh g d tr nn nhu cu thc l 800 50 = 750 thanh. Ta phi pht n hng theo k hoch vo u tun th 4 v lch sn xut bt u t u tun th 3.Tun 012345678 Tng nhu cu800 800Lng tip nhn theo tin 50D tr hin c50 50 50 000 0Nhu cu thc 0 0 0 750 00800 0Lng tip nhn t hng theok hoch0 0 0 750 00800 0Thanh g Thi gian cung ngmt 1 tun Lng n hng pht ra theok hoch0 07500 0 800 0 02. t hng theo kch c: Tun 012345678 Tng nhu cu200 200Lng tip nhn theo tin D tr hin c0 0 0 0 000 0Nhu cu thc0 0 0 0 20000 200Lng tip nhn t hng theok hoch 0 0 0 0 20000 200Cnh ca Thi gian lp rpmt mt tun Lng n hng pht ra theok hoch 0 0 0 200 00200 0 Tun 012345678 Tng nhu cu400 400Lng tip nhn theo tin 100D tr hin c100 100 100 100100100 100Nhu cu thc 0 0 0 300 00300 0Lng tip nhn t hng theo k hoch0 0 0 400 00400 0Khung ca Thi gian cung ngmt 2 tun Lng n hng pht ra theo k hoch0 400 0 0 40000 0ivithngtheokchc,nhucuthcttunth4cnl300snphm, trongkchckhungcal200,vvyphi t2ltunth4(ln ca n hng phi l bi s ca c n hng), mi l 200 sn phm, phn d tha 100 snphmtunth4scchuynlmdtrhinccatun5.Tngt tun th 7 cng s t thnh 2 l, mi l 200 sn phm. Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr125 Tun 012345678 Tng nhu cu800 800Lng tip nhn theo tin 50D tr hin c50 50 50 505050 50Nhu cu thc0 0 0 750 00750 0Lng tip nhn t hng theok hoch 0 0 0 800 00800 0Thanh g Thi gian cung ngmt 1 tun Lng n hng pht ra theok hoch 0 0 800 0 08000 0Cng tng t nh vy i vi thanh g, nhu cu thc t tun th 4 cn l 750 sn phm, trong kch c thanh g l 100, v vy phi t 8 l tun th 4, mi l 100 sn phm, phn d tha 50 thanh g tun th 4 s c chuyn lm d tr hin c ca tun 5. Tng t tun th 7 cng s t thnh 8 l, mi l 100 thanh g. 7.1.3.Cc phng php xc nh l hngi vi nhu cu c lp thng p dng phng php EOQxcnhkchclhngcnmua.Mhnh EOQ m hnh t hng kinh t c bn, l mt trong nhng phng php qun tr hng d tr. M hnh ny sctrnhbyphnsau.Tuynhin,ivi nhngnhucuphthucthvntrnnphctp hndotnhadngvchngloi,slngvthi giancnthitcachng.TrongMRPkhimuanhng nguynvtliudtrcnhucuphthuccrtnhiucchxcnhclhng c p dng. Thc t cho thy khng c mt cch no c u im ni tri hn tt c cc cch khc, v vy, ty tng trng hp c th mi doanh nghip c th la chn cho mnh mt chnh sch hp l. Di y l mt s phng php xc nh l hng: -Phng php t hng c nh theo mt s giai on Phngphpnys c thc hin bng cch nhm nhu cu thc t ca mt scc giai on c nh vo mt n hng thnh mt chu k t hng. -Mua theo l Theo nguyn tc mua theo l nguyn vt liu s c a n tng ng vi nhu cu trong tng thi k. Vd3:CngtyAnPhcmunxcnhchiphthngvchiphdtrn hng theo tiu chun a hng theo l ng vi nhu cu. Cho bit chi ph tn kho l 1 USD/sn phm/tun v chi ph thit lp n hng l 100 USD/ln.Thi k012345678910 Tng nhu cu353040010403003055 Lng tn kho sn c0000000000 Lng NVL a n3530400104030030550 Tng chi ph = chi ph t hng + chi ph d tr = 8 100 +0 = 800 USD -Phng php xc nh c l hng theo m hnh EOQ Phng php ny xc nh khi lng ca l hng t sao cho chi ph t hng v tr hng l nh nht. Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr126 Nu ta gi: D = nhu cu trong nm (s n v/nm) H = Ph tr hng (ng/nm) S = Ph t hng (ng/ln t) Q = S lng t hng (n v/ln t) TC = tng chi pht hng v tr hng: HQ SDTC2 Q= + 2QSQH-=V d 4: Vi s liu t v d 3, cho bit nhu cu trung bnh hng tun v nguyn vt liu l 27 n v, gi s 1 nm cng ty lm vic c 52 tun. Ta c:Nhu cu v nguyn vt liu c nm l D = 52 27 = 1.404 n v. 2 140 100Q 731 52- = = n v Thi k0 1 2 3 4 5 6 789 10Tng nhu cu353040010403003055 Lng tn kho sn c388414131643434422 Lng a n73737373 Tng chi ph = (100 + 100 + 100 + 100 ) + (38 + 8 +..+ 22) = 717 USD -Xc nh kch c l hng theo k thut cn i cc thi k b phnThc cht cng l phng php ghp l nhng vi chukkhngcnhccgiaion.Cclc ghpvinhautrncsxemxttngchiphd tr t ti mc thp nht c th c. y l chnh schclmtronglngthngkhcnhau ty thuc vo mi quan h gia chi ph t hng v chi ph lu kho. Phng php ny khng cho php xc nh c l ti u nhng li l phng php c chiphthp.Do,nlcchtipcncs dng ph bin.Phng php ny c gng cn i gia chi ph t hng v chi ph lu kho. Thut thchinllytngnhucuvnguynvt liuhocchitit,bphntrongcc giaionlintipchonkhicchiphthnggnnhtvichiphlukho thnh mt n t hng. V mt kinh t, c l ti u c tnh theo cng thc sau: Chi ph thit lp n hng (t hng) Q* = Chi ph lu kho ca 1 n v hng trong mt giai on Thctcltmcsaukhighpccgiaiontheonguyntccngdns c la chn khi tng lng nhu cu gn nht vi c ti u va tnh c. Phngphpnytoraslinhhottronghnhthnhccnthngmvn quantmmbogimthiucchiphdtr.Ncnglmkhongcch chnh lch gia c l trong cc n t hng. Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr127 V d 5: Vi s liu v d 3 v 4 ta c: Thi k0 1 2 3 4 5 6 789 10Tng nhu cu354040010403003055 Lng tn kho sn c400505040030300 Lng a n 75 906055 Tng chi ph ca phng n ny l:TC = (100 + 100 + 100 + 100) + ( 30 + 140 + 60) = 630 USD 7.2.Qun tr hng d tr 7.2.1.Thc cht, vai tr ca hng d tr 7.2.1.1.Quan nim v d tr v hng d trHngdtrlslnghnghoctoratrong qutrnhsnxutkinhdoanhnhmpngchonhu cu trong tng lai. Hng d tr thng chim t trng lntrongtisncadoanhnghip(thngthng chim4050%).Chnhvvy,vicqunl,kim sot tt hng d tr c ngha v cng quan trng, n gp phn m bo cho qu trnh sn xut tin hnh lin tc, c hiu qu.Hng d trbao gm nguyn vt liu, sn phm d dang,thnh phm d tr tu theoccloihnhdoanhnghipmcccdnghngdtrkhcnhau.Chnghn nh mt ngn hng s c nhng phng php tiu chun ring kim sot nh gi mc tn qu v tin mt; mt bnh vin s c nhng phng php kim sot ngun mu,thucmen;mtxnghipmayscphngphpkimtralngnguynvt liu d tr.i vi cc doanh nghip hot ng trong lnh vc dch v, hng d tr ch yu l cc dng c, ph tng v phng tin vt cht k thut dng vo hot ng. i vi lnh vc thng mi, doanh nghip mua bn kim li, hng d tr ca h ch yu l hng mua v v hng chun b chuyn n tay ngi tiu dng. i vi lnh vc sn xut, sn phm tri qua mt qu trnh ch bin bin u vo l nguyn vt liu thnh sn phmurannhngdtrbaogmnguynvtliu,bnthnhphmtrndy chuyn v thnh phm cui cng.-Trong lnh vc ny ngi ta phn li hng d tr thnh 4 loi: oD tr nguyn vt liu / b phn cu thnh. oD tr sn phm d dang. oD tr sn phm hon chnh. oD tr cc mt hng ph khc phc v sn xut. Bn thn vn d tr lun c hai mt tri ngc nhau. Ngi bn hng mong mun c nhiu hng d tr khch hng khng phi i lu. Nhn vin ph trch sn xut Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr128 mong mun c mc d tr nguyn vt liu ln d dng lp k hoch sn xut. Tuy nhin b phn ti chnh th mong mun mc tn kho t nht, v hng tn kho thng chim t trng ln trong ti sn ca doanh nghip, mc tn kho nhiukhin chi ph tng cao, mc ri ro ln...V vy cc doanh nghip phi tm cch xc nh mt mc cnbnggialnghngdtrphcvsnxut,phcvttyucucakhch hng, nhng c chi ph d tr mc ti u.-Trong qun tr d tr thng cp n cc loi chi ph c lin quan sau y:oChiphmuahng:Lchiphctnhtkhilnghngcanhngv gi mua mt n v. Chi ph ny c th c u i hng gim gi nu mua cng mt lc vi s lng ln. oChi ph t hng: L ton b cc chi ph c lin quan n vic thit lp cc n hng.Nbaogmccchiphtmngunhng,chiphchunb,chiphvn chuyn,chiphgiaonhnhng,kimtrasaist,nhpkho,ccchiphhnh chnh khc ...oChi ph lu kho: L nhng chi ph pht sinh trong thc hin hot ng d tr. N bao gm cc chi ph: Chi ph c hi: Khi l hng c d tr th vn u t khng dng vo mc ch khc c hoc vn phi tr li sut cho ngn hng khi tn ng;Chi ph ctgi: Chi ph thu a im lu gihngho,chiphhaomncsh tng kho bi, bo him, chi ph bo qun; Chi ph do li thi, h hng v mt mt: Chi ph do li thi s c phn b cho cc mn hngcnhiuriroblithi,mriro cngcaothchiphcngln.Snphmc thbhhng,thidolunhlng thc, hoa qu, sn phm ti sng... Chi ph mt mt l chi ph c th do hng ha b ly cp, tht thot hoc v...Tn thtkhiphibnsnphmmuavmkhngsdngna(dochuynhng sn xut kinh doanh, cht lng sn phm gim st);oChiphthiuhng:lnhngtnthtdothiuhnggynn.Tgcbn hng, nu thiu hng cung cp, khch hng s chuyn sang t hng ca doanh nghip khc. T gc sn xut, trong qu trnh sn xut, thiu hng dn n vic ngng sn xut i nguyn liu, ng bn thnh phm, ko di thi gian giao hng v dn n ngng caKhi nghin cu qun tr hng d tr, chng ta phi gii quyt hai vn c bn l: LngthngbaonhiultiuvThiimthngvolcnol thch hp. 7.2.1.2.Vai tr ca hng d tr Trong sn xut kinh doanh, d tr hng ho, nguyn vt liu l cn thit khch quan, n c nhng vai tr sau: Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr129 -m bo s gn b, lin kt cht ch gia cc khu, cc giai on ca qu trnh sn xut. Khi cung v cu v mt loi hng d tr no khng u n gia cc thi k, th vic duy tr thng xuyn mt lng d tr nhm tch ly cho thi k cao im l mt vn ht sc cn thit. Nh duy tr d tr, qu trnh sn xut s c tin hnh lin tc, trnh c s thiu ht t qung ca qu trnh sn xut.-m bo kp thi nhu cu ca khch hng, trong bt k thi im no. y cng l cch tt nht duy tr v tng s lng khch hng ca doanh nghip. Trong nn kinh t th trng, vic duy tr mt khch hng l rt kh khn, ngc li, mt i mt khch hng l rt d.-Phng nga nhng yu t ri ro trong sn xut v cung ng (nhng lc my hng hocnguynliucungcpchakpthi).Sthayithigiansnxutvvn chuyn trong sut qu trnh hot ng cng c th dn n s khng chc chn v thi gian p ng n hng. D tr c th lm gim tc ng ca s bin itrn v gip doanh nghip hot ng mt cch bnh thng. -Khaithclithdosnxutvtmuaviquymln.Doanhnghipcth c hng t l chit khu khi mua hng vi khi lng ln hoc tit kim c chi ph t hng.-D tnh trc s tng gi trong tng lai. Vic mua hng trc lin quan n mua thm mt khi lngsn phm mc gi thp hin ti hn l mua mc gi cao trongtnglai.Muahngvis lnglnhncnthitsdnnmcdtr nhiu hn v tng chi ph d tr. Tuy nhin, nu nh d on trong tng lai gi c s tng, cc chi ph ca vic mua hng trc c th b p c khon ny. -p ngnhu cu ca khch hng mt cch nhanh chng. Nhu cu khng phi lc no cng d bo chnh xc c, n c th thay i do yu t ma v, tnh chu k hoc nhng bin ng bt thng c th xy ra ngoi d bo. 7.2.2.Cc phng php qun tr hng d tr 7.2.2.1.K thut phn tch ABCKthutphntchABC c xut da vo nguyn tc Pareto (Pareto l mt nh kinh t ngi vo th k th 19). ng ta quan st v pht hin ra rng cmt s t ngi trong x hi li c thu nhp cao cn li a s l thunhpthphoctrungbnh.Tacngcththyl trongmtcahngbchhavinhiuchngloisnphmthphnlndoanhthu hoc li nhun ph thuc vo mt vi mt hng; trong mt doanh nghip hoc mt t chc trong s hng trm nhn vin th ch c mt s ngi c kh nng sng to thc s. Quy lut s t quan trng c th p dng vo qun tr hng d tr. K thut phn tch ABC l nguyn tc phn tch hng ho d tr thnh 3 nhm cn c vo mi quan h gia s lng v gi tr ca chng. Nguyn tc ny l s ci bin ca quy lut 80:20 ca Pareto.-Khi p dng nguyn tc Pareto cho vic qun l hng d tr, ngi ta thng chia hng d tr thnh 3 nhm: Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr130 oNhmA:Baogmnhngloihngdtrcgitrhngnmcaonht,vi gi tr t 70 80% so vi tng gi tr mt hng d tr, nhng v mt s lng chng ch chim 15%tng s mt hng d tr. oNhmB:Baogmnhngloihngdtrcgitrhngnmmctrung bnh,vigitrt15%25%sovitnggitrhngdtr,nhngvsnlng chng chim khong 30% tng s hng d tr. oNhm C gm nhng loi hng c gi tr hng nm nh, khong 5%tng gi tri cc loi hng d tr, tuy nhin s lng chng chim khong 55% so vi tng s loi hng d tr. -K thut phn tch ABC trong cng tc qun tr hng d tr c nhng tc dng sau: oThngxuynkimtravkimsottngmnhngvcbitlkimsot cht ch nhng mt hng thuc nhm A. Vic thit lp cc bo co chnh xc v nhm A phi c thc hin thng xuyn nhm m bo kh nng an ton trong sn xut. oCc ngun vn dng mua hng nhm A cn phi nhiu hn so vi nhm C, do cn c s u tin u t thch ng vo qun tr nhm A. oNh c k thut phn tch ABC trnh ca nhn vin gi kho tng ln khng ngng,dohthngxuynthchinccchukkimtra,kimsottng nhm hng. -Cch tin hnh phng php ABC nh sau: oXc nh khi lng, chng loi v gi tr cc loi hng d tr. oXc nh t l % v gi tr ca cc loi mt hng d tr. oSp xp theo th t gim dn v t l % ca gi tr hng d tr. onh s th t t trn xung theo danh sch cc mt hng d tr. oXc nh t l % lu k theo gi tr. oXc nh t l lu k theo mt hng. oPhn loi hng d tr thnh 3 nhm ABC. Bngth,chngtacthbiuthtiuchuncaccnhmhngdtrtheok thut phn tch ABC nh sau: Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr131 minh ha cho vn nu trn, chng ta xt v d sau:V d 6: Cng ty A c 10 loi nguyn vt liu d tr; s lng nhu cu mt nm, gi mua ca mi chi tit c th hin trong bng sau: K hiu NVLABCDEGHIKL Nhu cu nm (tn) 3.0004.0001.5006.0001.0005003006001.7502.500 Gi NVL (USD)5012451020500150020105 T ccloicc sliu vnhu cu hng nm, gi mt n v hng ha, gi tr hng nm, t l % ca mi loi nguyn vt liu ny ngi ta ng dng nguyn tc phn tch ABC chia nhm v sp xp thnh th t u tin nh trong bng di y: Mt hng Nhu cuhng nm Gi muamt n v Gi tr cc loi mt hng % v gi tr so vi tng gi tr nm Sp xp th t u tin A 3.0005015.00013,83 B4.0001248.0004,416 C1.5004567.5006,214 D6.0001060.0005,525 E1.0002020.0001,847 G500500250.000232 H3001500450.00041,41 I6002012.0001,110 K1.7501017.5001,618 L2.500512.5001,119 1.087.500100 Sau khi sp xp li th t v vi k thut phn tch ABC, ta phn loi 10 loi d tr trn thnh ba nhm nh sau: TTMt hng Gi trhng nm % v gi tr so vi tng gi tr nm % so vi tng s loi hng Xp loi 1H450.00041,410A 2G250.0002320 3A15.00013,830 4C67.5006,2140B 5D60.0005,5250 6B48.0004,4160 7E20.0001,8470 8K17.5001,6180C 9L12.5001,1190 10I12.0001,1100 1.087.500100 7.2.2.2.M hnh t hng kinh t c bn-M hnh EOQ The Basic Economic Order Quantity Model MhnhEOQlmttrongnhngkthutkimsotdtrphbinvlui nht, n c nghin cu v xut t nm 1915 do ng Ford.W.Ham, n ngy nay n vn c nhiu cc doanh nghip s dng. K thut kim sot d tr theo m hnh ny rt d p dng, tuy nhin phi c nhnggi nh cho trc, l: Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr132 oNhu cu gn nh c nh v c xc nh trc.oThi gian t khi t hng n khi nhn l khng i v c xc nh trc. oKhng cho php c hin tng thiu hng. oChi ph t hng l c nh, khng lin quan n s lng hng t v khng cchnh sch chit khu (gi mua gim theo lng bn tng). oHngmcsnphmchlchngloinnht,khngxtntnhhung nhiu mt hng. Vi gi nh nh trn s biu din s dng d tr theo thi gian c dng nh sau: VigithitnhuculcnhvcchobngD,thDsgimdnkhis dng v c th hin bng dc l D. Mc tn kho ti a l Q* v s c s dng ht nkhi mc tn kho bng 0. Tn kho trung bnh s l Q*/2 Nu ta t mi ln s lng nhiu th s ln t hng s gim v chi ph t hng s thp, ngc li nu t hng mi ln vi s lng nhiu th chi ph d tr s tng. Ta cn tm mt lng t hng Q*sao cho tng chi ph v d tr l nh nht. Nu ta gi: D = Lng nhu cu v nguyn vt liu trong nm.Q = Lng t hng mi ln. S = Chi ph t hng mt ln. H = Chi ph d tr nguyn vt liu trong nm. Th chi ph lu kho hng trong nm lchi ph d tr bnh qun nhn vi s lng hng d tr v bng QH2 Chi ph t hng trong nm l chi ph tng ln t hng bnh qun nhn vi s ln t hng trong nm v bng DSQ Tng chi ph v hng d tr s l: Q DTC H S2 Q= + c TC min th TC'Q = 0 Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr133 Ta c: 22H DS 2DCTC 0 Q2 Q H'' = = = Vy:Q* = 22DSQH=T lng Q* ny ngi ta cng c th tnh c s n hng ti u nn t trong nm v thi gian trung bnh gia cc ln t hng trong nm nh sau: S lng n hng mong mun trong 1 nm l: DQ-

Khong cch trung bnh gia 2 ln t hng l: V d 7: Cng ty An Thnh c nhu cu v sn phm A l 3.000 sn phm/nm vi chi ph t hng mi ln l 100 USD v chi ph d tr l 10 USD/sn phm/nm. Chobittrongnmdoanhnghipssnxut300ngy.Vytacthtnhton c cc ch tiu v d tr nh sau: a) Lng t hng ti u :2DC245H=sn phm b) S lng n hng mong mun: D13Q- =n hng c) Khong cch trung bnh gia 2 ln t hng: 3002313 = ngy -im t hng li (ROP Reorder Point) Trong m hnh d tr EOQ chng ta gi nh rng chng ta s ch n khi hng trong kho ht hng (mc = 0) th mi tin hnh t hng v khi t hng s nhncngay.Tuynhintrongthctthigiangialcthngvnhnhngc th di hn. S lng n v hng t Q* khng phi i n thi gian T mi t, m phi t mt thi gian trc hng v ng lc trc khi d tr ht thi im T. V vy ngi ta phi xc nh mt im t hng li trnh hin tng thiu ht. im t hng li l lng hng t trc khi lng s dng = 0 cn c vo thi gian vn chuyn n hng m bo khng gin on trong qu trnh sn xut. im t hng li (ROP) c xc nh nh sau: ROP = d L Trong :d l nhu cu tiu dng hng ngy v hng d tr. L l thi gian t khi t hng n khi nhn c hng (thi gian ch i hng). Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr134 im t hng li (ROP) c biu din bng hnh v sau y: V d 8: Cng ty Anh Thnh c nhu cu v sn phm A l 3000 sn phm/nm vi chi ph t hng mi ln l 100 USD v chi ph d tr l 10 USD/sn phm/nm, gimisnphml50USD.Chobittrongnmdoanhnghipssnxut300 ngy, thi gian t khi t hng n khi hng n l 10 ngy, vy im t hng li s l: DROP L 100N= = sn phm 7.2.2.3.M hnh sn lng t hng theo sn xut POQ (Production Order Quantity Model)L m hnh d tr c ng dng khi lng hng c a n lin tc hoc khi sn phm va c tin hnh sn xut va tin hnh s dng hoc bn ra. Trong m hnh EOQ chng ta gi nh ton b lng hng ca mt n hng c nhn ngay trong mt chuyn hng. Tuy nhin c nhng trng hp doanh nghip s nhn hng dn dn trong mt thi gian nht nh. Trong trng hp ny ngi ta phi tm kim mt m hnh t hng khc vi EOQ. MhnhPOQthchhpchohotngsnxutkinhdoanhcangithngnn ncgilmhnhsnlngthngtheosnxut.Mhnhnyscp dng trong trng hp lng hng c a n mt cch lin tc, hng c tch ly dnchonkhilngthngctpktht.Mhnhnycngcpdng trong trng hp doanh nghip va sn xut va bn hoc doanh nghip t sn xut ly vt t dng. Trong nhng trng hp nh th ny, chng ta phi quan tm n mc sn xut hng ngy ca nh sn xut hoc mc cung ng ca nh cung ng. Trong m hnh ny v c bn cc gi thuyt ging nh m hnh EOQ, im khc bit l hng c a n lm nhiu ln v nhu cu s dng hng ngy phi nh hn mccungngtrnhhintngthiuht.BngphngphpgingnhEOQta xc nh c sn lng ti u Q*. Gi:p: Mc sn xut (mc cung ng) hng ngy. d: Nhu cu s dng hng ngy (d < p). t: Thi gian sn xut c s lng cho 1 n hng (hoc thi gian cung ng). Q: Sn lng ca n hng. H: Chi ph d tr cho 1 n v mi nm. Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr135 M hnh POQ c dng nh sau: Tng chi ph v d tr ca m hnh POQ l: HQ SDTC2 Q-= + c TC min th TC'Q = 0 suy ra TC = 21 d D(1 ) H S 02 p Q + =21 d D(1 ) H S2 p Q = 2DS 2DS pQdH p dH(1 )p- = = hoc *p2 D S dQH d p = Tng chi ph d tr s l: D Q p dTC S ( ) HQ 2 p= + V du 9: Cng ty A c kh nng sn xut vi tc 500 sn phm mt ngy v kh nngsdng30.000snphmmtnm.Chobitmtnmcngtylmvic300 ngy,chiphdtrl2USD/nphm,chiphmilnthngl30USD.Vy lng t hng ti u v tng chi ph v d tr s c xc nh nh sau: Trc ht xc nh d = D/N, sau xc nh Q* ta c: Q*=2DSdH(1 )p=2DSH pp d = 1.061 sn phm D Q p dTC S H 1.909 USDQ 2 p| | = + = |\ .

7.2.2.4.M hnh khu tr theo s lng (QDM Quantity Discount Model) L m hnh d tr c tnh n s thay i ca gi c ph thuc vo khi lng hng trongmilnthng.Vickhutrtheoslngthcchtlgimgihngha khi khch hng mua loi hng no vi mt s lng ln.Vdnumuadi10snphmgisl5USD/snphm,numuat1149sn phm s l 4,5 USD/sn phmv mua t 50 sn phm tr ln s c gim gi ch cn 4 USD/sn phm. tng doanh s bn hng, nhiu cng ty thng a ra chnh sch gim gi khi s lng mua cao ln. Chnh sch bn hng nh vy c gi l bn hng khu tr theo lng mua. Nu chng ta mua vi s lng ln s c hng gi thp. Nhng lng d tr s tng ln v do chi ph lu kho s tng. Xt v mc chi ph t hng th lng t hng tng ln, s dn n chi ph t hng gim i. Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr136 Mc tiu t ra l chn mc t hng sao cho tng chi ph v hng d tr hng nm l thp nht. Trng hp ny ta p dng m hnh khu tr theo s lng (QDM). Tng chi ph v hng d tr c tnh nh sau: Tng chi ph ca hng d tr= Chi ph mua hng + Chi ph t hng + Chi ph d tr D QTC Pr D S HQ 2= + + xc nh c lng hng ti u trong mt n hng, ta tin hnh cc bc sau y: -Bc 1: Xc nh mc sn lng ti u tng mc khu tr: Q*=2DSI Pr Trong : Pr: l gi mua ca mt n v hng ho. I: l t l % chi ph d tr tnh theo gi mua 1 n v hng ho. -Bc2:iuchnhsnlngnhngnhngkhngiukinlnmcsn lngphhp.mimckhutr,nulnghngtnhbcmtthp khngiukinhngmcgikhutr,chngtaiuchnhlnghng ln n mc ti thiu c hng gi khu tr. Ngc li, nu lng hng cao hn th iu chnh xung bng mc ti a. -Bc 3: Tnh tng chi ph theo mc sn lng iu chnhS dng cng thc tnh tng chi ph nu trn tnh ton tng chi ph cho cc mc sn lng c xc nh bc 1 v bc 2.-Bc 4: Chn Q* c tng chi ph ca hng d tr thp nht xc nh bc 3.V d 10: Nhu cu v my khoan in ca mt ca hng kinh doanh l 1.000 ci/nm. Chi ph t hng l 100 USD/n hng v chi ph lu kho bng 40% gi mua. Nu t hng t hn 120 ci th gi ca mt ci khoan in l 78 USD; nu t hng t 120 ci trln,gisgimxungchcn50USD/ci.Cahngcnnpdngmhnh chit khu theo s lng hay khng? Hng dn:Trc ht cn tnh Q* i vi tng mc gi *pQ (78 USD) =12DSI Pr =2 1.000 1000, 4 78 = 80 sn phm *pQ (50 USD) =22DSI Pr =2 1.000 1000, 4 50 = 100 sn phm Cnphiiuchnhmcsnlngnybng120michngchitkhuv khng th t mua 100 ci khoan in ti mc gi 50 USD/ci; chnh sch chit khu khng p dng i vi n hng di 120 sn phm.Sau tnh tng chi ph ca 2 phng n ny: TC1(78USD) = Pr1 D+*1DQ S + *1Q2 I Pr1 1.0001.000 78 100 0, 4 78 80.498 USD80= + = Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr137 TC2(50USD) = Pr2 D + *2DQ S+ *2Q2 I Pr2 1.000 1201.000 50 100 0, 4 50 52.033 USD120 2= + + = Sosnh2trnghptrntathyphngn2cchiphnhhn,dodoanh nghipnntmua120cikhoaninchomilnthngvigimuac chit khu l 50 USDV d 11:Mt bnh vin ln s dng 500 chic bnh xy mt nm. Chi ph mi ln t hng bnh qun l 15 USD/n hng. Chi ph d tr chim 20% gi mua. Gn y cngtychngchmuahngcanhsnxuttheophngphpkhutr theo s lng, c th nh sau: Gi thng thngl 48 USD/chic. Vi lng mua t 50 99, gi l 47 USD/ chic. Vi lng mua t 100 chic tr ln, gi l 45 USD/chic. Vy lng t hng ti u l bao nhiu? Hng dn: Bc 1: Xc nh Q* theo cc mc gi: *1Q = 2 (2.000) (48)(0,2) (15) = 79 chic *2Q = 2 (2.000) (47)(0,2) (15) = 80 chic *3Q= 2 (2.000) (45)(0,2) (15) = 82 chic Bc 2: Xc nh lng t hng iu chnh Q* theo cc mc khu tr. Vi *1Q = 79 chic, nm trong vng p dng gi 47 USD/chic t 50 99 chic, nn phiiuchnhlngmuaxungmctiacatrnghpmuavikhilng thng thng l 49 chic vi mc gi l 48 USD/chic hoc yu cu nh cung cp bn vi mc gi 47 USD v khi lng mua s l 79 chic.Gi s trng hp bnh vin s vn mua vi khi lng *1Q = 79 chic/n hng. Vi *2Q= 80 chic, nm trong vng p dng gi 47 USD/ chic t 50 99 chic nn khng cn iu chnh. Lng t hng trng hp ny s l *2Q= 80 chic/n hng. Vi*3Q= 82 chic, thp hn mc p dng gi khu tr 45 USD nn ta phi iu chnh. Lng t hng iu chnh *3Q= 100 chic/n hng. Bc 3: Xc nh tng chi ph v hng d tr: TC1 = 47 2.000 + 2.00079 15 + 792 0,2 47 = 96.759 USD TC2 = 47 2.000) + 2.00080 15 + 802 0,2 47 = 94.751 USD TC3 = (45) (2.000) + 2.000100 15 + 1002 (0,2) (45) = 90.750 USD Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr138 Bc 4: La chn lng t hng ti u.So snh tng chi ph v hng d tr trn ta thy mc *3Q= 1.000 l mc t hngti u cho mi ln t hng (tng chi ph v hng d tr nh nht) v t hng theo gi 45 USD/ chic l tt nht. 7.2.2.5.M hnh phn tch bin M hnh phn tch bin xc nh mc d tr ti u qua vic tnh ton li cn bin v l cn bin. Khi d tr t n mc no m nu ta thm vo mt n v d tr s c li cn bin mong i bng hoc ln hn l cn bin mong i.Nu gi:-p l xc sut xy ra khi nhu cu ln hn hoc bng vi mc cung ng cho trc, vy 1 ps l xc sut xy ra khi nhu cu nh hn mc cung ng cho trc. -MP l li nhun cn bin vML l thit hi (l) cn bin th li cn bin mong i s bng xc sut ca n v ly thm bn c nhn vi li cn bin (p MP). -Tngt,lcnbinmongisbngxcsutcanvlythmmbn khng c nhn vi l cn bin (1 p ML). Vy ta c:p MP> (1 p) ML p> MLMP ML + V d 12: Mt ca hng chuyn bn hoa qu, gi bn nho l 6USD/kg v mua vo l 4USD/kg.Nukhngtiuthctrongngysthithi1USD.Cuithngca hng kim k li v thy s lng nho bn c hng ngy nh sau: Nhu cu (kg/ngy)60616263646566 S ln xut hin378101282 Hy xc nh mc d tr hiu qu? Theo cng thc trn, iu kin chp nhn mc d tr l: p> MLMP ML +>0,3 TTNhu cuTn sXc sut xut hin Xc sut cu ln hn cung 16030.061 26170.140.94 36280.160.80 4 63100.200.64 564120.240.44 66580.160.20 76620.040.04 501.00 Ta thy xc sut bn c 64kg nho l 0,44 > 0,3. Nn ca hng nn d tr mc l hiu qu. Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr139 TM LC CUI BI Bi hc ny thc cht l s kt hp ca hai ni dung qun tr hng d tr v lp k hoch nhu cu nguyn vt liu.Phn ni dung v lp k hoch nhu cu nguyn vt liu cn phi nm r thc cht, cc yu cu vquytrnhhochnhnhucunguynvtliu.PhngphpMRPgipchoccdoanh nghip hoch nh mt cch tng i chnh xc v nhu cu nguyn vt liu sao cho chi ph d tr l thp m vn m bo cung ng nguyn vt liu vo ng thi im cn thit. tnh ton c nhu cu nguyn vt liu theo phng php MRP cn phi hiu r v cu trc ca sn phm, xc nh chnh xc tng nhu cu v sn phm, nhu cu thc t, lng d tr sn c, lng tip nhn theo tin , kch c l hng t xc nh lng tip nhn t hng theo k hoch v lng n hng pht ra theo k hoch.Phnnidungvquntrhngdtrnulnthcchtvvaitrcahngdtr.Cc phng php d tr c bn nh m hnh EOQ, m hnh POQ, m hnh khu tr theo sn lng, m hnh phn tch bin. Cc phng php ny gip ngi hc bit cch xc nh lng t hng ti u cn bng gia cc loi chi ph trong d tr, thi gian t hng ti u, s ln t hng, im t hng li v tng chi ph d tr. Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr140 CU HI N TP1.D tr l g? Vai tr ca d tr? 2.Trnh by mc tiu, nhim v ca qun tr hng d tr trong cc doanh nghip. 3.Hy nu cc loi chi ph ca hng d tr?4.Hy trnh by k thut phn tch ABC trong qun tr hng d tr. 5.Hy nu cc im ging v khc nhau gia m hnh d tr EOQ v POQ. 6.M hnh khu tr theo s lng c p dng trong trng hp no? V sao? 7.M hnh phn tch cn bin c s dng nh th no trong xc nh lng t hng ti u. 8.Trnh by cc bc thc hin phng php d tr khu tr theo sn lng DQM. 9.MRP l g? Hy trnh by cc yu cu c bn ng dng MRP trong mt doanh nghip. 10. Ti sao trong phng php MRP cn phn tch cu trc ca sn phm theo hnh cy? Phn bit gia nhu cu c lp v nhu cu ph thuc? 11. Hy nu trnh t thc hin hoch nh nhu cu nguyn vt liu bng phng php MRP. 12. Hy nu cc phng php xc nh kch c ca l hng? Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr141 BI TP Bi 1: Hyxcnhcpsnphmvslngivitngccchititcnthitsnxut10sn phmAlpha.Sktcucasnphmvslngchititccthnhphncchotrong bng di y: Bi 2 Cho mt sn phm vi nhng thng s sau: Tng nhu cu (D) = 360 n v sn phm; Chi ph d tr (H) = 100USD / sn phm/nm; Chi ph t hng (S) = 100 USD/n hng, s ngy lm vic trong nm l 300 ngy. a. Hy xc nh lng t hng kinh t? b. Hy xc nh s n hng mong mun trong mt nm?c. Hy xc nh thi gian ch hng? Bi 3 Nhu cu v mt loi sn phm l 3 n v/ngy, v thi gian t khi t hng n khi nhn hng l 15 ngy, hy xc nh im t hng li?Bi 4 Cng ty A chuyn sn xut ph tng vi mc 300 chic/ngy. Loi ph tng ny c s dng 12.500 chic/nm v trong nm cng ty lm vic 250 ngy. Chi ph lu kho 20.000 ng/1 n v trong nm, chi ph t hng mi ln l 300.000 ng. Lng t hng sn xut l bao nhiu? Bi 5 Mt cng ty sn xut bnh cu ho c sn lng l 30.000 bnh/nm. Mi mt bnh cu ho cn c mt quai xch. Bit rng chi ph lu kho l 1,5 USD/quai xch, chi ph cho hot ng sn xut l150USD,vmccungngl300quai/ngy.Sngylmvictrongmtnml300 ngy.Hy xc nh lng t quai xch ti u? Bi 6 Mtcngtybnchitrem,gnychngchmuahngcanhsnxuttheo phng php khu tr theo s lng, c th nh sau: - Gi thng thng mt chic xe l 5.000 ng. - Vi lng mua t 1.000 1.999 chic, gi l 4.800 ng. - Vi lng mua t 2.000 chic tr ln, gi l 4.750 ng Bi 7: Hoch nh nguyn vt liu v qun tr hng d tr142 Chi ph t hng l 49 ngn ng mt ln t hng. Nhu cu hng nm l 5000 xe. Chi ph lu kho bng 20% gi mua. Vy lng t hng ti u l bao nhiu? Bi 7 Nhu cu v my khoan in ca mt ca hng kinh doanh l 1.000 ci/nm. Chi ph t hng l 100 USD/n hng v chi ph lu kho bng 40% gi mua. Nu t hng t hn 120 ci th gi ca mtcikhoaninl78USD;nuthngt120citrln,gisgimxungchcn50 USD/ci. Ca hng c nn p dng m hnh chit khu theo s lng khng? Bi 8 Cng ty An M s dng 1.500 chi tit A trong mt nm. Bit rng chi ph d tr l 45 USD/chi tit/nm,chiphthngl150USD/nhng,thigianlmvictrongnml300ngy,v thi gian t khi t hng n khi nhn c hng l 6 ngy. Hy tnh: a. Lng t hng ti u? b. im t hng li? c. Chi ph d tr hng nm?