Keywords: integration, innovative heuristic, interval order policy, inventory total cost 1. INTRODUCTION

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5 eermnaon o Inerval Order Polcy a srbuor and ealers usng Innovave Heursc Mehod o Mnmze Invenory Toal Cos (Applcaon Case a srbuor X n Indonesa) ansa Man Heryano, Sanoso, and Elzabeh Ivana Krsano Bachelor Program n Indusral Engneerng Maranaha Chrsan Unversy, Bandung, Wes Java, Indonesa Tel: (+62) Correspondng Auhor s Emal: ransa.mh@eng.maranaha.edu Absrac: A supply chan sysem usually consss o enes such as manuacurer, dsrbuor, realer, and cusomer. Inegraon n a supply chan sysem s an mporan acor o ncrease compeveness beween each oher. Ths research wll be dscussed how o negrae beween sngle dsrbuor and en realers o egh producs and o nd a mnmum nvenory oal cos. Currenly, dsrbuor and each realer have s own order polcy and gve an mpac ha nvenory oal cos s expensve. The nnovave heursc mehod whch used o negrae order polcy beween dsrbuor and realers or mul em s a model o Prahars, e al (214). The nal sep n hs research s calculang he cos elemens such as orderng cos and holdng cos, hen calculang nvenory oal cos wh curren mehod and nnovave heursc mehod. The resul o hs research s nerval order polcy a dsrbuor and each realer. Ths mehod s gven a mnmum nvenory oal cos a dsrbuor and each realer. Keywords: negraon, nnovave heursc, nerval order polcy, nvenory oal cos 1. INTOUCTION Supply chan managemen s a mehod or negrave approach or managng produc low, normaon, and money negravely nvolve enes rom upsream o downsream whch conss o suppler, manuacurer, dsrbuon nework, and logsc servce (Pujawan, 21). Manuacurer produces produc, dsrbuor dsrbues produc rom manuacurer o realer, prepares and delvers produc base on realer order. srbuor wll order produc o manuacurer or keepng sock a warehouse so ha well nvenory conrol s really needed. Somemes, each eny a supply chan has s own role or producng or orderng produc. Ths research concerns o apply one mehod o negrae wo enes n supply chan sysem beween dsrbuor and realers. There s sngle dsrbuor and en realers o egh producs and no negraon polcy beween hem. The supply chan sysem o ha case s shown n Fgure 1. Currenly, dsrbuor and each realer have s own polcy o order produc. srbuor has a x quany order o manuacurer and every realer has a x perod order o dsrbuor. Fgure 1. Supply Chan Sysem The derence order polcy beween every eny or dsnegrae beween hem gve an mpac o he nvenory oal cos. The expensve nvenory oal cos wll cause low compeveness beween realer and low advanage a dsrbuor and realer. Ths research res o negrae order polcy beween dsrbuor and realers or mul em producs o mnmze nvenory oal cos n every chan and o ncrease advanage and compeveness among realers. 1

6 2. METHOOLOGY Ths research uses nnovave heursc mehod base on model o Prahars, e al (214). The model s developmen model rom any earler research whch major explan abou jon replenshmen. The characersc o hs model s consss o sngle warehouse and n realers and or mul em. The am o hs mehod s deermnng nerval order polcy whch has mnmze nvenory oal cos. The nal sep or usng hs mehod s calculang he cos elemen such as orderng cos and holdng cos. The ollowng algorhm o nnovave heursc s shown n Fgure 2. Sar Sep 1 k=1 =1,..,N =1,,m k=k-1 Unuk =1,..,N =1,,m TC(k) Q() Sep 7 Sep 2 Sep 3 No TC = TC(k) Q() Q() > 1,4 k=k+1 (=max(q) TC(k) Q() Sep 8 Yes Sep 4 k=k+1 Unuk =1,..,N =1,,m TC(k) Q() TC(k) < TC an Q() >1,4? an k 1 Yes Sep 9 No Sep 5 Yes TC(k) < TC an Q() > 1,4? No Sep 6 TC(k) < TC an Q() 1,4? No Yes Toal cos mnmum End a. Sep 1 Se all Fgure 2. Innovave Heursc Algorhm (Prahars, e al, 214) k value o 1 or each realer and each produc. b. Sep 2 Calculae nal nvenory oal cos and calculae Q value based on rs sep. 2

7 c. Sep 3 Check Q value. The expecaon Q value s less han or equal 1.4. I s mean ha oal nvenory cos s he smalles. I Q value s more han 1.4, hen connue o he sep 4. The value o 1.4 s based on model o Nlsson, e al (27) whch descrbes he lowes error rom major replenshmen cos. d. Sep 4 Add k value = k + 1 Q value more han 1.4 and hen calculae new nvenory oal cos and Q value. e. Sep 5 Check Q value and new nvenory oal cos. The Q value s less han or equal 1.4 and he new nvenory oal cos mus be less han nal nvenory oal cos, so ha connue o sep 6. I no and hen go back o sep 4.. Sep 6 Check Q value and new nvenory oal cos mus be less han nal nvenory oal cos. I hs condon s ullled, so ha nvenory oal cos s he smalles. I no hen go o sep 7. g. Sep 7 Less k value = k - 1 k value more han 1 and hen calculae new nvenory oal cos and Q value. h. Sep 8 Add k value = k + 1 or he hghes or maxmze Q value and hen calculae new nvenory oal cos and value. Q. Sep 9 Check Q value and new nvenory oal cos. The Q value s less han or equal 1.4 and he new nvenory oal cos mus be less han nal nvenory oal cos. I s mean ha oal nvenory cos s he smalles. I no hen go o sep 8 ll Q value less han or equal o 1.4 and new nvenory oal cos less han nal nvenory oal cos. 2.1 Model Componen 2.1.1Assumpon The assumpons or hs mehod and hs case are descrbed below: 1. emand rae or each realer and each produc s consan value. 2. ealer uses EOQ (Economc Order Quany) o order o dsrbuor. 3. Backorder sn allowed Perormance Crera and ecson Varable Perormance crera used n hs research s mnmzng oal nvenory cos. The oal nvenory cos consss o orderng cos and holdng cos. The decson varable n hs research usng nnovave heursc s dsrbuor order nerval and nvenory oal cos. Order nerval a realer s mulple rom order requency a dsrbuor. I more han or equal han so ha he requency value a realer (1, 2, 3, ). I less han so ha he requency value a realer 3. MATHEMATICS 3.1 Mahemacs Noaon Index Noaon: = ndex or produc ( = 1, 2,, 8) = ndex or realer ( = 1, 2,, 1) ecson Varable: = orderng nerval a dsrbuor (monh) TC = nvenory oal cos (I/monh) (k) 1 1 1,,,

8 Parameer noaon: w = major orderng cos a dsrbuor (I/order) w H = orderng cos or produc a dsrbuor (I/order) = holdng cos or produc a dsrbuor (I/monh) = demand or realer and produc (box) = orderng requency a dsrbuor (order/monh) = orderng requency a realer (order/monh) S = major orderng cos a realer (I/order) S = orderng cos a realer and produc (I/order) = nerval order me a realer and produc (monh) = orderng nerval a realer (monh) h = holdng cos a realer or produc (I/monh) Q = rao beween holdng cos and order cos a realer or produc k = neger value = 1 as comparson 3.2 Componen Cos a srbuor Orderng Cos Orderng cos a dsrbuor consss o major orderng cos (xed orderng cos) and mnor orderng cos (varable orderng cos) wh ormulaon: w Toal orderng cos = + 8 w (1) = 1 Holdng Cos srbuor wll have holdng cos > 1 8 H ( Toal holdng cos = = 1 = Componen Cos a ealer or > wh ormulaon: 1) or > 1 (2) Orderng Cos Orderng cos a all realers consss o major orderng cos (xed orderng cos) and mnor orderng cos (varable orderng cos) or each produc wh ormulaon: 1 S 1 8 S Toal orderng cos = + where = and = k (3) = 1 = 1 = 1 Holdng Cos Holdng cos a all realers wh ormulaon: 1 8 h Toal holdng cos = = 1 = 1 2 (4) 3.4 Invenory Toal Cos Invenory oal cos usng nnovave heursc can be ormulaed: w w H ( 1) S S h Invenory oal cos = = 1 = 1 = 1 2 = 1 = 1 = 1 = 1 = 1 Subsue: = and = k, hen: 2 (5) 4

9 1 H (1 ) w w S S h Invenory oal cos = = 1 = 1 = 1 2 = 1 = 1 = 1k = 1 = 1 2 k (6) The nvenory oal cos ormulaon s calculaed by ndng value as orderng nerval a dsrbuor. value s dtc reached = so can be ormulaed: d S 2 w + w + S + = 1 = 1 = 1 = 1 k * = (7) h k H 1 + = 1 = 1 = 1 = 1 Subsue (7) o (6) so ha he opmal nvenory oal cos can be ormulaed: S 1 h = k TC * 2 w w S H 1 + (8) = 1 = 1 = 1 = 1 = 1 = 1 = 1 = 1 k 3.5 ao Beween Orderng Cos and Holdng Cos The rao beween orderng cos and holdng cos or S Q value s ormulaed: k 2 S Q = = h 2 2 k h k (9) 2 4. ESULT AN ISCUSSION In hs research, he nnovave heursc mehod wll apply a dsrbuor X whch has 1 realers and 8 producs. Based on calculang resul, srbuor X has major orderng cos ( w ) abou 194,327 I/order, mnor orderng cos or each produc ( w ) abou 785/I/order, and holdng cos or each produc ( H ) abou 1,517 I/monh. The nal daa rom each realer can be shown a Table 1. Table 1. Orderng Cos a ealer ealer Major Orderng Cos ( S ) Mnor Orderng Cos ( S ) (I/order) () (I/order) = ,349 1,63 1,63 1,63 1,63 1,63 1,63 1,63 1, ,779 1,474 1,474 1,474 1,474 1,474 1,474 1,474 1, ,911 1,4 1,4 1,4 1,4 1,4 1,4 1,4 1, ,466 1,51 1,51 1,51 1,51 1,51 1,51 1,51 1, ,432 1,4 1,4 1,4 1,4 1,4 1,4 1,4 1, , ,432 1,4 1,4 1,4 1,4 1,4 1,4 1,4 1,4 8 12,411 1,4 1,4 1,4 1,4 1,4 1,4 1,4 1,4 9 12,69 1,63 1,63 1,63 1,63 1,63 1,63 1,63 1, ,

10 ealer () Table 2. Holdng Cos and emand a ealer Holdng Cos ( h ) (I/monh) emand ( ) (box) = ,522 1, , ,512 1, , ,527 1, , ,515 1, , , ,555 1, , ,539 1, , ,578 1, , ,671 1, , ,528 1, , ,63 1, , Currenly, dsrbuor and each realer have s own polcy o order produc. srbuor has a x quany order o manuacurer and every realer has a x perod order o dsrbuor. The mnmum nvenory oal cos wh nnovave heursc mehod s reached by 147 eraon process and can be shown a Table 3. Based on calculaon process wh curren mehod whch no negraon among hem and nnovave heursc mehod wh negraon, he comparson nvenory oal cos can be shown a Table 4 and he orderng nerval and orderng quany a dsrbuor and each realer can be shown a Table 5. Table 3. Ieraon Process wh Innovave Heursc No Toal Cos Toal Cos Toal Cos Toal Cos Toal Cos Qr<1,4 No Qr<1,4 No Qr<1,4 No Qr<1,4 No (I/monh) (I/monh) (I/monh) (I/monh) (I/monh) Qr<1, No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No Yes No No No No Yes No No No No Yes No No No No Yes 6

11 Table 4. Comparson o Invenory Toal Cos Poson Curren Mehod (I/monh) Innovave Heursc Mehod (I/monh) srbuor 5,52,198 4,375,562 ealer 1 576, ,938 ealer 2 665, ,47 ealer 3 1,97,611 85,79 ealer 4 1,735,456 1,24,577 ealer 5 621,876 58,229 ealer 6 563, ,555 ealer 7 1,92,285 79,237 ealer 8 546,537 44,338 ealer 9 574,88 443,49 ealer 1 552, ,675 Toal 13,528,226 1,419,6 Table 5. Comparson o Orderng Inerval and Orderng Quany Curren Mehod Innovave Heursc Mehod Poson Orderng Inerval (monh) Orderng Quany (box) Orderng Inerval (monh) Orderng Quany (box) srbuor - 6, ,121 ealer ealer ealer ealer ealer ealer ealer ealer ealer ealer CONCLUSION Based on calculaon process, resul and dscusson, nnovave heursc mehod has a mnmum nvenory oal cos compared wh curren mehod. Currenly, dsrbuor and each realer have s own order polcy and gve an mpac ha nvenory oal cos s expensve. Ths nnovave heursc mehod has opmal orderng nerval and negraon beween dsrbuor and realers. Ths mehod also gves savng abou 3,19,22 I/monh or 23%/monh. Inegraon and mnmum nvenory oal cos wll ncrease compeveness among realers. EFEENCES Askn, Goldberg. (22). esgn and Analyss o Lean Producon Sysem. John Wley and Sons, Inc. Bua, E. S., J. G. Mller. (1979). Producon-Invenory Sysems: Plannng and Conrol. chard. Irwn, Homewood.IL. junad, M. (25). Pengaruh Perencanaan Pembelaan Bahan Baku dengan Model EOQ unuk Mul Iem dengan All Un scoun, Jurnal Ilmah Teknk Indusr, Vol. 4, No.2, hal

12 Kusuma, Hendra. (1999). Perencanaan dan Pengendalan Produks. And, Yogyakara. Nlsson, A., Segersed, A., Slus, E. V.. (27). A New Ierave Heursc o Solve The Jon eplenshmen Problem Usng a Spreadshee Technque. Inernaonal Journal o Economy Producon 18, hal Nur Bahaga, Senaor. (26). Ssem Invenor. ITB. Prahars, Y., Naalan, Y., Wee, H.M. (214). An Innovave Heursc n Mul Iem eplenshmen Problem or One Warehouse and N ealers. Journal o Indusral Engneerng, Vol.16, No. 1, hal Pujawan, I. (21). Supply Chan Managemen. Guna Wdya, Surabaya. angku, F. (21). Manajemen Persedaan: Aplkas d Bdang Bsns. PT aja Grando Perkasa, Jakara. Tersne, chard J. (1994). Prncple o Invenory and Maeral Managemen. The Unversy o Oklahoma, 3 rd ed. Tersne, chard J. (1998). Prncple o Invenory and Maeral Managemen. The Unversy o Oklahoma, 4 h ed. 8

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