Chuong 4-Hoach Dinh Nhu Cau Vat Tu

CHNG 4: HOCH NH NHU CU

NGUYN VT LIU (MRP)

I. Thc cht v yu cu ca hoch nh nhu cu nguynvt liu (MRP).

II. Xy dng h thng hoch nh nhu cu nguyn vt liu.

III. Phng php xc nh kch c l hng.

I. THC CHT V YU CU CA HOCH NH NHU

CU NGUYN VT LIU (MRP)

1. Khi nim MRP

MRP l h thng hoch nh v xy dng lch trnh v nhu

cu nguyn vt liu trong tng giai on.

MRP s tr li c cc cu hi:

Doanh nghip cn loi nguyn vt liu no?

Cn bao nhiu?

Khi no cn?

Khi no cn pht n hng hoc lnh sn xut?

Khi no nhn c hng?

2. Mc tiu ca MRP

Gim thiu lng d tr nguyn vt liu.

Gim thi gian sn xut v thi gian cung ng.

To s tha mn v nim tin tng cho khch hng.

To iu kin cho cc b phn phi hp cht ch, thng nht

vi nhau, pht huy tng hp kh nng sn xut ca DN.

Tng hiu qu ca hot ng sn xut kinh doanh.

3. Cc yu cu trong ng dng MRP

C h thng my tnh v chng trnh phn mm tnh

ton v lu tr thng tin.

Chun b i ng cn b qun l c kh nng v trnh s

dng my tnh v nhng kin thc c bn trong xy dng MRP.

m bo chnh xc v lin tc cp nht thng tin mi trong:

Lch trnh sn xut Ha n nguyn vt liu H s d tr nguyn vt lium bo y v lu tr h s d liu cn thit

II. XY DNG H THNG HOCH NH NHU CU

NGUYN VT LIU (MRP)

1. Nhng yu t c bn ca MRP

a. Nhng yu t u vo c bn:

S lng nhu cu sn phm d bo

S lng sn phm trong n t hng

Mc sn xut v d tr

Cu trc ca sn phm

Danh mc nguyn vt liu

Thi im sn xut

Thi hn cung ng hoc thi gian gia cng

D tr hin c v k hoch

Mc ph phm cho php

u vo u ra

Qu trnh x l

Lch trnhSn xut

H sha nnguynvt liu

H snguynvt liud tr

Chng trnhmy tnh MRP

Bo co nhucu NVL nh k

Bo co nhucu NVL

hng ngy

Bo co v nhng thc hin

Khuyn co muahng

Khuyn co cbit

n hng

D bo

Thit k s

thay

i

Tip nhn

Rt ra

Lch trnh sn xut:

Ch r nhu cu sn phm cn sn xut v thi gian cn c

p ng.

Thng tin v nhu cu cn p ng c ly t nhng ngun

khc nhau: n t hng ca khch hng, s liu d bo.

Nhu cu c lp

Thi gian ca lch trnh sn xut thng ly n v l tun.

VD: Lch trnh sn xut di y cho thy k hoch u ra i

vi chi tit X. S lng sn xut tun th 4 l 100 v tun 8 l

150

Chi tit X 1 2 3 4 5 6 7 8

S lng 100 150

Bng danh mc NVL:

Cung cp thng tin v cc loi chi tit, linh kin v ph kincn thit to ra 1 n v sn phm cui cng.

Ngoi ra cn cho bit thng tin v mi lin h gia cc hngmc linh kin thng qua cu trc hnh cy ca sn phm

Trong DN thng dng 3 loi ha n:

Ha n theo nhm b phn

Ha n theo sn phm in hnh

Ha n cho nguyn vt liu b sung

H s d tr:

Cho bit lng d tr NVL hin c.

N dng ghi chp, bo co tnh trng ca tng loi NVLtrong thi gian c th

Ghi nhn tng nhu cu, n hng s tip nhn v s lng

tip nhn tng ng

Thng tin khc: nh cung cp, thi gian cung ng, ln ca

l cung ng

b. Nhng yu t u ra ca MRP

Nhng loi nguyn vt liu no cn t hng mua hay sn

xut?

S lng bao nhiu?

Khi no?

2. Trnh t hoch nh nhu cu NVL

Cn thc hin qua 4 bc:

Bc 1: Phn tch kt cu sn phm

Hoch nh nhu cu NVL c tin hnh da trn vic phn

chia nhu cu thnh nhu cu c lp v nhu cu ph thuc:

Nhu cu c lp l nhu cu sn phm cui cng

Nhu cu ph thuc l nhng nhu cu th sinh, chng lnhng b phn, chi tit cu thnh nhu cu c lp

Phn tch cu trc sn phm thng qua s hnh cy

Cp trong s kt cu: cp 0 l cp ng sn phm cuicng. Mi ln phn tch thnh phn cu to ca b phn ta li

chuyn sang mt cp

B phn trn l b phn hp thnh, b phn di l bphn thnh phn

VD: Sn phm hon chnh c ghi cp 0 trn nh ca cy.

Nhng b phn cn thit lp rp thnh sn phm hon chnh

cp 1. Mi b phn ny c cu to t nhng chi tit khc v

c th hin cp 2, tip tc nh vy s hnh cu trc sn phm

X

B(2) C(1)

E(4) D(3) G(2) F(2)

H(4) I(5)

Cp 0

Cp 1

Cp 2

Cp 3

Trng hp mt b phn , chi tit c mt nhiu cp trong kt

cu sn phm.Ta dng nguyn tc h cp thp nht

Y

A B C D E

G E G F

E EE

Bc 2: Tnh tng nhu cu

Tng s lng d kin cho tng loi NVL trong tng giai on mkhng tnh n d tr hin c hoc lng s tip nhn.

Tng nhu cu cc b phn chi tit bng s lng t hng theo khoch ca cc b phn trung gian trc n nhn vi h s nhn nu c.

Bc 3: Tnh nhu cu thc

Nhu cu thc l tng s lng nguyn liu, chi tit cn cung

cp cho tng giai on:

Nhu cu thc = Tng nhu cu - D tr hin c + D tr an

ton

D tr hin c l tng d tr ang c thi im bt u ca

tng thi k

Lng tip nhn l tng s chi tit a vo sn xut nhng

cha hon thnh hoc l s lng t hng mong i s nhn ti

thi im bt u ca mi giai on.

C nhiu chnh sch t hng:

t hng theo l: s lng hng t bng vi nhu cu thc

t hng theo kch c

Bc 4: Xc nh thi gian pht n t hng hoc lnh sn

xut

L thi gian phn phi hay thi gian cung cp sn xut ca mi

b phn, nguyn vt liu.

Thi gian t hng = Thi im cn c khong thi gian

cung ng

Qu trnh hoch nh NVL, linh kin c th hin trong bng

k hoch c dng sau:

Tun 1 2 3 4 5 6 7 8

Tng nhu cu

Lng tip nhn

theo tin

D tr c sn

Nhu cu thc

Nhn hng

Pht n hng

VD: Mt cng ty sn xut g nhn c 2 n t hng lm

cnh ca: 100 ci giao vo tun th 4 v 150 ci vo tun 8, vt t

gm 4thanh g v 2 khung. Cc thanh g c sn xut ti cng ty

mi thanh mt mt tun, khung c mua ngoi vi thi gian cung

ng l 2 tun. Vic lp rp cnh ca mt 1 tun, c lch tip nhn(d

tr ban u) tun 1 l 70 thanh g. Hy xc nh s lng v thi

gian biu lng pht ra theo n hng k hoch p ng nhu cu

trong cc iu kin sau:

1. Lng t hng theo l (nhu cu thc)

2. Lng t hnh theo c ny 320 khung v 70 thanh g

a. Xy dng lch trnh sn xut

Tun1 2 3 4 5 6 7 8

S lng 100 150

b. Xy dng kt cu ca sn phm

c. Xy dng thi gian biu lp rp

Khung (2) Thanh g (4)

Cnh ca

Tun 1 Tun 2 Tun 3 Tun 4 Tun 5 Tun 6 Tun 7 Tun 8

thanh g

Lp rp

cnh caMua khung

thanh g

Mua khung

Lp rp

cnh ca

Sn xut Sn xut

d. Tnh tng nhu cu v nhu cu thc

t hng theo l (nhu cu thc):

Tun 1 1 2 3 4 5 6 7 8

S lng 100 150

Cnh ca

Thi gian

cung

cp = 1 tun

Tng nhu cu100 150

Lng tip nhn theo tin

D tr hin c

Nhu cu thc100 150

Lng tip nhn t hng theo k hoch

100 150

Lng n hng pht ra theo k hoch

100 150

Khung

ca

Thi gian

cung

cp = 2 tun

Tng nhu cu200 300


D tr hin c

Nhu cu thc200 300


200 300


200 300

Thanh

g

Thi gian

sn xut = 1 tun

Tng nhu cu400 600

Lng tip nhn theo tin 70

D tr hin c70 70 70

Nhu cu thc330 600


330 600


330 600

t hng theo kch cTun 1 2 3 4 5 6 7 8

S lng 100 150

Cnh ca

Thi gian

lp rp = 1

tun

Tng nhu cu100 150


D tr hin c

Nhu cu thc100 150


100 150


100 150

Khung

ca

C =320

Thi gian

cung

cp = 2 tun

Tng nhu cu200 300


D tr hin c120 120 120 120 140

Nhu cu thc200 180


320 320

Lng n pht hng ra theo k hoch

320 320

Thanh

g

C =70

Thi gian

sn xut = 1 tun

Tng nhu cu400 600


70

D tr hin c

70 70 70 20 20 20 20 50

Nhu cu thc

330 580


350 630


350 630

III. PHNG PHP XC NH KCH C L HNG

1. Mua theo l

Nguyn tc cp hng theo nhu cu thc gi l cp theo l.

Theo phng php ny l cn bng no mua bng y.

Thch hp vi l hng kch c nh.

t hng thng xuyn, lng d tr cung cp ng lc

thp v khng tn chi ph lu kho.

Khng thch hp i vi doanh nghip sn xut nhiu sn

phm hoc sn phm c cu trc phc tp v khng thch hp

vi nhng phng tin chuyn ch c tiu chun ha

2. Phng php t hng c nh theo mt s giai on

gim s ln t hng v n gin hn trong theo di ghi

chp nguyn vt liu d tr ta dng phng php t hng c

nh theo 1 s giai on.

3. Phng php cn i cc giai on b phn

L phng php ghp l nhng vi chu k khng c nh.

Lng t hng ty thuc vo mi quan h gia chi ph t

hng v chi ph lu kho.

C l ti u c tnh theo cng thc:

EPP =

Khi ghp cc giai on ta s dng nguyn tc cng dn

chn thi im t hng.

VD: S liu v nhu cu thc t NVL. Hy dng phng php

cn i cc giai on b phn xc nh c l hng. Bit rng : chi

ph mi ln t hng l 1 triu v chi ph lu kho 1 n v hng

trong tun l 5000 ng

Chi ph t hng

Chi ph lu kho 1 n v hng trong mt giai on

EPP = 1000000/ 5000= 200 n v

T xc nh thi im t hng v lng t hng tng ng:

Tun Tng

1 2 3 4 5 6 7 8

Nhu cu

thc50 80 55 90 10 60 120 80 545

Tun Tng

Nhu cu thc50 80 55 90 10 60 120 80 545

Lng n hng tip nhn

185 0 0 160 0 0 200 0 545

4. Phng php xc nh c l hng theo EOQ

Phng php ny cho chi ph ti u nu nh nguyn liu

tng i ng nht

Nu cu trc sn phm gm qu nhiu loi nguyn vt liu,

chnh lch nhiu th khng p dng c

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Chuong 4-Hoach Dinh Nhu Cau Vat Tu