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Chuong 4-Hoach Dinh Nhu Cau Vat Tu
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Transcript of Chuong 4-Hoach Dinh Nhu Cau Vat Tu
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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.
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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?
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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.
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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
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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
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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
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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
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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
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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?
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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
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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
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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
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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.
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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:
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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
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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
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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
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d. Tnh tng nhu cu v nhu cu thc
t hng theo l (nhu cu thc):
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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
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Khung
ca
Thi gian
cung
cp = 2 tun
Tng nhu cu200 300
Lng tip nhn theo tin
D tr hin c
Nhu cu thc200 300
Lng tip nhn t hng theo k hoch
200 300
Lng n hng pht ra theo k hoch
200 300
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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
Lng tip nhn t hng theo k hoch
330 600
Lng n hng pht ra theo k hoch
330 600
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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
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
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Khung
ca
C =320
Thi gian
cung
cp = 2 tun
Tng nhu cu200 300
Lng tip nhn theo tin
D tr hin c120 120 120 120 140
Nhu cu thc200 180
Lng tip nhn t hng theo k hoch
320 320
Lng n pht hng ra theo k hoch
320 320
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Thanh
g
C =70
Thi gian
sn xut = 1 tun
Tng nhu cu400 600
Lng tip nhn theo tin
70
D tr hin c
70 70 70 20 20 20 20 50
Nhu cu thc
330 580
Lng tip nhn t hng theo k hoch
350 630
Lng n hng pht ra theo k hoch
350 630
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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.
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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
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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
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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