THE EFFECT OF LEAD-TIME ON THE SUPPLY CHAIN: THE MEAN VERSUS THE VARIANCE

2011 ◽  
Vol 10 (01) ◽  
pp. 175-185 ◽  
Author(s):  
XIN JAMES HE ◽  
XIAOBO XU ◽  
JACK C. HAYYA
Keyword(s):  
Supply Chain ◽  
Lead Time ◽  
Inventory Systems ◽  
Time Variability ◽  
Inventory Cost ◽  
Safety Stock ◽  
Stochastic Inventory ◽  
Q Model ◽  
Total Inventory ◽  
The Mean

In a study on stochastic inventory systems, Chopra et al. (Decision Sciences35(1) (2004) 1–24) argue that decreasing lead time is the right lever if they want to cut inventories, not reducing lead time variability. According to Chopra et al., reducing the mean lead time, μ, is more important than reducing the lead time variance, σ2, to reduce total inventory cost via a reduced safety stock. This paper is a criticism of Chopra et al., where the optimal z was derived based upon a predetermined Q, instead of solving the optimal z and Q simultaneously in a (z, Q) inventory system. We argue that such an approach is inappropriate because the two decision variables, z and Q, are in general interdependent, and, moreover, reducing reorder point (safety stock), z, does not necessarily decrease the total inventory cost. We demonstrate by means of a truncated lead time (z, Q) model that it is lead time variability, not mean lead time, that affects the inventory policy and total supply chain cost.

scholarly journals Analysis Of Stock Control Of Raw Materials Of Dzohir Noodles In Bengkulu

2022 ◽  
Vol 3 (1) ◽  
Author(s):  
Monika Ahmelia ◽  
Herlin Herlin ◽  
Abdul Rahman
Keyword(s):  
Wheat Flour ◽  
Lead Time ◽  
Raw Materials ◽  
Raw Material ◽  
Inventory Cost ◽  
Safety Stock ◽  
Stock Control ◽  
Inventory Costs ◽  
Total Inventory ◽  
Research Period

This study aims to analyze the stock inventory control of Mie Dzohir's raw materials in Bengkulu. The analytical method used is Economic Order Quantity (EOQ), Reorder Point (ROP), Total Inventory Cost (TIC) and Safety Stock (SS). The results showed that to meet the raw material needs of 91,375 kg during the research period, from January 2020 to December 2020 (12 months), the number of economical purchases/EOQ of wheat flour raw materials that had to be made by the Mie Dzohir factory in Bengkulu was as much as 5,372 kg for each order with a purchase frequency of 17 times for a period from January 2020 to December 2020. Reorders or reorder points (ROP) can also be determined, namely reordering should be done when 345 kg of inventory is in warehouse, with a lead time of 1 days so as not to hamper the company's production process. The total inventory cost (TIC) can also be determined, namely the total cost of raw material inventory of Rp. 3.572.188, - therefore, it can save on inventory costs of Rp. 1.051.697,- .Safety stock (SS) of 95 kg which must be in the warehouse, this is intended therefore, there is no shortage of wheat flour raw materials if there is a delay in the delivery of raw materials.

Modeling of an Inventory System with Variable Demands and Lead Times using a Fuzzy Approach

2016 ◽  
pp. 133-151
Author(s):  
Vijay Kumar ◽  
Pravin Kumar
Keyword(s):  
Customer Service ◽  
Lead Time ◽  
Service Level ◽  
Research Topic ◽  
Lead Times ◽  
Inventory Cost ◽  
Safety Stock ◽  
Customer Service Level ◽  
Optimum Order ◽  
Total Inventory

Inventory modeling has always been an innovative research topic for the researchers. It is concerned with minimization of the total inventory cost and maximization of the service level with minimum inventory. In the real world, the demand is always variable; and also the lead time of supply of an item cannot be always fixed due to some unavoidable circumstances. This chapter is focused on an inventory model with shortages where demand quantity and lead time are considered as variable and represented by triangular fuzzy numbers. An expression for optimum order size, reorder point, safety stock and fuzzy total safety stock cost is developed for a fixed customer service level. This model may help the manager to minimize the inventory cost with a maximum service level under the environment of uncertainty and vague information.

scholarly journals IMPLEMENTASI MODEL STOKASTIK PADA PERMASALAHAN OPTIMASI PERSEDIAAN KELAPA PADA TINGKAT DISTRIBUTOR

2020 ◽  
Vol 9 (1) ◽  
pp. 90
Author(s):  
NOVI RUSTIANA DEWI ◽  
EKA SUSANTI ◽  
BAMBANG SUPRIHATIN ◽  
AGUSTINA BIDARTI ◽  
SINTA ELPATRIKA ABELIA ◽  
...  
Keyword(s):  
Lead Time ◽  
Random Variable ◽  
Inventory System ◽  
Inventory Cost ◽  
Inventory Costs ◽  
Stochastic Inventory ◽  
Stochastic Inventory Model ◽  
Total Inventory ◽  
Stochastic Inventory Models ◽  
Product Inventory

In the inventory system is given operational policies relating to product inventory control, such as how much is ordered, when to order with the aim of minimizing storage and ordering costs. Customer demand and lead time affect the inventory system. This study aims to determine the densitas distribution of demand data, total inventory costs and optimal coconut supply for the two order periods using the stochastic inventory model. Stochastic inventory models can be used if there is variable uncertainty. This paper discusses the optimization of coconut inventories using a stochastic model with uncertainty about demand and lead time. It is known that demand data is uniformly distributed, based on the realization value of random variable requests can be formed in 49 scenarios. Obtained an optimal total inventory cost for the two planning periods is Rp. 45,672,910, optimal supply for period one was 26031 coconuts. Inventory levels in two period for any scenarios are

scholarly journals Analisis Bullwhip Effect pada Rantai Supply dengan Model Q Menggunakan Pendekatan Hadley-Within di PT. XYZ Medan

2019 ◽  
Vol 2 (4) ◽  
Author(s):  
Martha Purnama Sari Panggabean ◽  
Dimas Akmarul Putera ◽  
Nursafwah
Keyword(s):  
Supply Chain ◽  
Inventory Control ◽  
Distribution System ◽  
Control Policy ◽  
Bullwhip Effect ◽  
Product Distribution ◽  
Soft Drinks ◽  
Inventory Cost ◽  
Inventory Control Policy ◽  
Q Model

PT. XYZ adalah perusahaan yang bergerak didalam pembuatan kemasan botol minum. Pendistribusian produk dilakukan PT XYZ menggunakan data historis berdasarkan jumlah permintaan pada tahun 2013 dan 2014. Data tersebut menunjukkan bahwa terjadinya perbedaan hasil. Tahun 2013 memiliki jumlah permintaan yang lebih rendah dari tahun 2014. Informasi terdapat bahwa perlu dilakukan pengevaluasian karena didalam rantai produksi terdapat bullwhip effect. Terdapat nilai bullwhip Effect menujukan bahwa nilai bullwhip effect untuk distributor Indomaret, Carrefour, dan rantai manufakturnya masing-masing sebesar 0,5303; 0,2967, dan 0,5114. Usulan perbaikan dapat diatasi yaitu dengan model Q yang berfungsi menggendalikan persediaan pada rantai pasok dengan metodeHadley-Within. Perhitungan pengendalian persediaan untuk distributor Indomaret, Carrefour, dan rantai manufakturnya masing-masing sebesar 1,0721; 1,100; dan 1,0714. Hasil dari perhitungan menujukan bahwa terjadi keseimbangan antara penjual dan pembeli sehingga biaya pun dapat dihematkan pada PT XYZ.   PT. XYZ Medan is manufacturing company that produce soft drinks of beverages in containers. In the product distribution system at PT. XYZ Medan, found that the number of orders based on the result of forecasting in 2013 lower than actual orders at distrbutor and manufacturer in 2014. Distorsion of information on this order can evaluate the indication of bullwhip effect in supply chain. Based on the result calculation of bullwhip effect, found that the value of bullwhip effect for Indomaret distributor, Carrefour, and supply chain of manufacturer each of 0,5303; 0,2967, and 0,5114. Proposed improvements to predominate bullwhip effect that is by doing inventory control policy with Q model using Hadley-Within approach. The value of bullwhip effect aftre doing inventory control policy for Indomaret distributor, Carrefour, and supply chain of manufacturer each of 1,0721; 1,100; dan 1,0714. The value of bullwhip effect which is close to one shows that the variance between the number of the order and the number of the demand nearly balanced so as to save the inventory cost at PT. XYZ Medan.

scholarly journals Analisis Pengendalian Persediaan Bahan Baku dengan Menggunakan Metode EOQ pada PT Sigma Indonesia MFG

JUDICIOUS ◽  
2020 ◽  
Vol 1 (2) ◽  
pp. 102-106
Author(s):  
Elsa Fitriyani ◽  
Matdio Siahaan
Keyword(s):  
Standard Deviation ◽  
Order Quantity ◽  
Microsoft Excel ◽  
Inventory Cost ◽  
Safety Stock ◽  
Total Inventory

Tujuan yang ingin dicapai dalam penelitian ini adalah untuk mengetahui apakah pengendalian persediaan bahan baku pada PT Sigma Indonesia Manufacturing sudah efisien atau belum. Bahan baku utama yang di gunakan PT Sigma Indonesia Manufacturing adalah material STKM diameter 8.0. PT Sigma Indonesia Manufacturing mengolah material STKM diameter 8.0 menjadi barang jadi yaitu Collar 8.0. Masalah yang di hadapi oleh perusahaan dalam kaitannya dengan persediaan bahan baku diantaranya adalah pembelian bahan baku yang optimal, persediaan pengaman, serta total biaya persedian bahan baku. Untuk menjawab permasalahan yang ada, penulis menggunakan metode EOQ (Economical Order Quantity). Analisis ini terdiri dari pembelian bahan baku yang optimal, Safety stock, dan Total Inventory Cost. Perhitungan pembelian bahan baku yang optimal dengan menggunakan metode EOQ (Economical Order Quantity), perhitungan Safety stock dicari hitung dengan menggunakan standard deviation sedangkan Total Inventory Cost dihitung dengan menggunakan Microsoft Excel. Data yang digunakan adalah data pembelian dan pemakaian bahan baku Collar 8.0 selama periode Januari 2016 sampai Desember 2018. Hasil yang didapatkan setelah dilakukan perhitungan EOQ jumlah bahan baku yang ekonomis untuk setiap kali pembelian pada tahun 2016 sejumlah 278 batang , tahun 2017 sejumlah 284 batang , tahun 2018 sejumlah 285 batang. Total Inventory Cost menurut perhitungan EOQ pada tahun 2016 adalah sebesar Rp165.591, tahun 2017 sebesar Rp168.754, tahun 2018 sebesar Rp169.325.Total Inventory Cost yang di keluarkan perusahaan pada tahun 2016 sebesar Rp215.268, tahun 2017 sebesar Rp219.380, tahun 2018 sebesar Rp220.122.

scholarly journals Analysis and Design of Information Systems for Control of Raw Materials in UD. YRS Alumunium Work Using EOQ Method

Tech-E ◽  
2020 ◽  
Vol 4 (1) ◽  
pp. 30
Author(s):  
Assaji Assaji ◽  
Rudy Arijanto
Keyword(s):  
Information Systems ◽  
Raw Materials ◽  
Order Quantity ◽  
Sequence Diagrams ◽  
Inventory Cost ◽  
Safety Stock ◽  
Analysis And Design ◽  
Total Inventory ◽  
Manual Recording ◽  
Class Diagrams

In the current era of globalization, information technology and information systems are developing very fast. YRS Alumunium Work is a furniture company that manufactures cupboards, stove racks, sinks, and especially for storage of household items. The problems currently being faced by businesses, among others; (a) recording still using stationery and books or still using manual recording methods, (b) ineffective stock checking, (c) sudden out of stock, to solve the problem it is proposed to make a system using the web that can be integrated into stock by a calculation method. With UML scenario depiction (activity diagrams, usecase diagrams, class diagrams, sequence diagrams). To check the inventory of goods easily done effectively, know the minimum amount of stock, and must place an order again using the EOQ (Economic Order Quantity) method. By using the eoq method, it takes into account that for bolts to get an economical amount of inventory as much as 522.01 with a safety stock of 21 will place an order again when the stock becomes 50 and the total inventory cost is 110 458.4418.

scholarly journals Inventory model for deteriorating items with negative exponential demand, probabilistic deterioration and fuzzy lead time under partial back logging

2020 ◽  
Vol 30 (3) ◽  
Author(s):  
Nabendu Sen ◽  
Sumit Saha
Keyword(s):  
Inventory Management ◽  
Lead Time ◽  
Probability Distributions ◽  
Optimal Strategies ◽  
Inventory Model ◽  
Deteriorating Items ◽  
Optimal Time ◽  
Inventory Cost ◽  
Total Inventory ◽  
Negative Exponential

The effect of lead time plays an important role in inventory management. It is also important to study the optimal strategies when the lead time is not precisely known to the decision makers. The aim of this paper is to examine the inventory model for deteriorating items with fuzzy lead time, negative exponential demand, and partially backlogged shortages. This model is unique in its nature due to probabilistic deterioration along with fuzzy lead time. The fuzzy lead time is assumed to be triangular, parabolic, trapezoidal numbers and the graded mean integration representation method is used for the defuzzification purpose. Moreover, three different types of probability distributions, namely uniform, triangular and Beta are used for rate of deterioration to find optimal time and associated total inventory cost. The developed model is validated numerically and values of optimal time and total inventory cost are given in tabular form, corresponding to different probability distribution and fuzzy lead-time. The sensitivity analysis is performed on variation of key parameters to observe its effect on the developed model. Graphical representations are also given in support of derived optimal inventory cost vs. time.

ANALISIS PENGENDALIAN PERSEDIAAN BAHAN BAKU DENGAN METODE ECONOMIC ORDER QUANTITY PADA CV. DIKA JOK JENGGAWAH

2019 ◽  
Vol 18 (2) ◽  
Author(s):  
Siti Husnul Hotima ◽  
Dini Hayati
Keyword(s):  
Economic Order Quantity ◽  
Economic Order ◽  
Order Quantity ◽  
Inventory Cost ◽  
Safety Stock ◽  
Reorder Point ◽  
Total Inventory ◽  
Point Total

Tujuan yang diharapkan dari penelitian ini adalah ingin menganalisis persediaan bahan baku optimal yang dibutuhkan dengan menggunakan metode Economic Order Quantity (EOQ), menganalisis berapa besar persediaan pengaman (Safety stock), menganalisis kapan waktu yang tepat untuk melakukan pemesanan kembali (reorder point), menganalisis total persediaan bahan baku atau Total Inventory Cost (TIC). Jenis penelitian yang digunakan adalah kuantitatif deskriptif. Teknik pengumpulan data yang digunakan dalam penelitian ini adalah wawancara, observasi, dan dokumentasi. Penelitian dan hasil perhitungan yang dilakukan menunjukkan bahwa persediaan bahan baku setiap tahunnya tidak stabil. Bahan baku yang dibutuhkan oleh perusahaan apabila dihitung menggunakan metode Economic Order Quantity (EOQ) pada tahun 2016 adalah sebesar 11,52 m3 dengan frekuensi pembelian 6 kali per periode (1 tahun). Tahun 2017 sebesar 9,90 m3 dengan frekuensi pembelian 6 kali per periode (1 tahun). Persediaan pengaman (safety stock) pada tahun 2016 adalah sebesar 16,48 m3. Pada tahun 2017 sebesar 11,25 m3. Titik pemesanan kembali (reorder point) pada tahun 2016 adalah sebesar 17,18 m3. Pada tahun 2017 sebesar 13,1 m3. Total biaya persediaan bahan baku yang dihitung menurut Economic Order Point (EOQ) lebih sedikit dibandingkan dengan yang dikeluarkan oleh perusahaan, maka ada penghematan biaya persediaan. Pada tahun 2016 sebesar Rp.110.499.402 dan pada tahun 2017 sebesar Rp.81.655.306. Kata Kunci: Economic Order Quantity (EOQ), Persediaan Pengaman (Safety Stock), Titik Pemesanan Kembali (Reorder Point), Total Biaya Persediaan atau Total Inventory Cost (TIC).

scholarly journals ANALISIS KINERJA MANAJEMEN PERSEDIAAN DI BARJAZ COMPANY MENGGUNAKAN PENDEKATAN EOQ

2018 ◽  
Vol 8 (1) ◽  
pp. 203
Author(s):  
I Made Antony Dwi Putra ◽  
Agoes Ganesha Rahyuda
Keyword(s):  
Control System ◽  
Inventory Control ◽  
Study Data ◽  
Inventory System ◽  
Raw Material ◽  
Inventory Cost ◽  
Safety Stock ◽  
Analysis Techniques ◽  
Inventory Turnover ◽  
Total Inventory

A large amount of inventory in the company makes high inventory cost, while low inventory will risk the occurrence of shortage of inventory. The research was conducted at Barjaz Company, to find out how the raw material inventory system applied by the company, and whether the system is efficient or not. Methods of data collection is done by conducting interviews to parties related to inventory and observation on the object under study. Data analysis techniques used are; EOQ analysis, determining safety stock, determining reorder point, determining maximum inventory, calculating inventory turnover and calculating total inventory cost. The results show that the inventory system applied today is still not effective. Companies should conduct inventory control system using EOQ method. With the implementation of EOQ, the company's inventory turnover value increased and the company issued a total inventory cost of Rp 1,099,982, lower than the company's inventory control system at Rp 1,671,100.

scholarly journals Optimization Of Raw Material Inventory Costs In The Food Supply Chain Using Differential Evolution Algorithm

2018 ◽  
Vol 73 ◽  
pp. 13016
Author(s):  
Mara Huriga Priymasiwi ◽  
Mustafid
Keyword(s):  
Supply Chain ◽  
Differential Evolution ◽  
Food Industry ◽  
Differential Evolution Algorithm ◽  
Optimization Method ◽  
Raw Material ◽  
Inventory Cost ◽  
De Algorithm ◽  
Material Requirement ◽  
Total Inventory

The management of raw material inventory is used to overcome the problems occuring especially in the food industry to achieve effectiveness, timeliness, and high service levels which are contrary to the problem of effectiveness and cost efficiency. The inventory control system is built to achieve the optimization of raw material inventory cost in the supply chain in food industry. This research represents Differential Evolution (DE) algorithm as optimization method by minimizing total inventory based on amount of raw material requirement, purchasing cost, saefty stock and reorder time. With the population size, the parameters of mutation control, crossover parameters and the number of iterations respectively 80, 0.8, 0.5, 200. With the amount of safety stock at the company 7213.95 obtained a total inventory cost decrease of 39.95%. Result indicate that the use of DE algorithm help providein efficient amount, time and cost.

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