scholarly journals A model of a production-repair inventory system with time-varying demand and quality-dependent recovery channels

2021 ◽  
Vol 36 ◽  
pp. 04002
Author(s):  
Ivan Yeo
Keyword(s):  
Raw Materials ◽  
Planning Horizon ◽  
Inventory System ◽  
Raw Material ◽  
Time Varying ◽  
Total Cost ◽  
External Sources ◽  
Varying Demand ◽  
Infinite Planning Horizon ◽  
Better Than

In this paper, we study an inventory system over an infinite planning horizon where a time-varying demand is satisfied by process cycles that consist of a production batch followed by a recovery batch. Our model considers three types of inventory—returned items, serviceable items, and raw material. Furthermore, our model considers two recovery channels—recovery into serviceable items and recovery into raw material. Serviceable items are thus sourced from two inputs—direct recovery and production from raw material. These raw materials can be salvaged from returned items, as well as bought from external sources whenever required. We propose an expression for the unit time total cost as well as a numerical method to find the optimal policy. The properties of the model are studied through numerical experiments, in particular, the feasible situations where hybrid policies are better than pure policies.

Optimal Attainment of Production Rates for a Multi-Stage Kanban Managed Production System With Time Varying Demand

2008 ◽  
Author(s):  
Yunmei Fang ◽  
Y. J. Lin
Keyword(s):  
Production System ◽  
Raw Materials ◽  
Raw Material ◽  
Time Varying ◽  
Operation Planning ◽  
Production Rates ◽  
Supply Chain System ◽  
Work In Process ◽  
Multi Stage ◽  
Varying Demand

This paper delves into the evaluation of an operation planning for a realistic multi-stage, single-product Kanban managed production system with time varying production rates and finished goods demands. The study pursued is to dynamically and systematically manipulate the production rate of each stage and the raw material orders at the first stage which are corresponding to the minimum integrated inventory costs incurred due to raw materials, finished products and work-in-process (WIP) inventories under a varying demand of finished product. Simulation results verify the effectiveness of the proposed operation planning methodology for a multistage Kanban managed production and supply chain system.

scholarly journals PERENCANAAN DAN PENGENDALIAN PERSEDIAAN BAHAN BAKU PAIL CAT MENGGUNAKAN METODE MATERIAL REQUIRMENT PLANNING (MRP) PADA PT. XYZ

JUMINTEN ◽  
2020 ◽  
Vol 1 (4) ◽  
pp. 163-172
Author(s):  
Vify Elviana ◽  
Akmal Suryadi
Keyword(s):  
Inventory Management ◽  
Consumer Demand ◽  
Raw Materials ◽  
Raw Material ◽  
Economic Order Quantity ◽  
Economic Order ◽  
Order Quantity ◽  
Material Requirements Planning ◽  
Total Cost ◽  
Material Requirements

Persediaan merupakan aset perusahaan yang memiliki peran penting dalam operasi bisnis, sehingga perusahaan penting untuk melakukan manajemen persediaan yang baik, artinya perusahaan harus mampu mengantisipasi kendala maupun tantangan yang ada dalam pengelolahan persediaan untuk meminimalisasi total biaya yang harus dikeluarkan oleh perusahaan. Permasalahan yang timbul pada persediaan bahan baku di PT XYZ adalah perusahaan melakukan perencanaan dan pengendalian bahan baku hanya berdasarkan pada pengalaman-pengalaman sebelumnya dan tidak berdasarkan pada metode yang sudah baku. Oleh karena itu pembelian bahan baku tidak sesuai dengan permintaan konsumen. Hal tersebut sering menyebabkan terjadinya kelebihan maupun kekurangan stok bahan baku. Kesalahan dalam penentuan besarnya investasi dalam persediaan akan mengurangi keuntungan perusahaan. Adanya persediaan bahan baku yang terlalu besar, akan menambah beban biaya pemeliharaan dan penyimpanan dalam gudang, serta kemungkinan terjadinya penurunan kualitas bahan baku yang dapat menyebabkan berkurangnya keuntungan perusahaan. Namun jika persediaan bahan baku terlalu sedikit maka akan berakibat pada terhambatnya proses produksi, sehingga tidak terpenuhinya permintaan konsumen. Hasil penelitian ini dapat menyimpulkan bahwa perencanaan kebutuhan bahan baku dengan metode perusahaan didapatkan total cost sebesar Rp 1.796.762.429,-, sedangkan metode Material Requirements Planning (MRP) didapatkan total cost sebesar Rp 1.576.011.801,-. Maka dapat disimpulkan telah terjadi penurunan total cost seluruh bahan baku sebesar 12,28%. Hal ini membuktikan bahwa metode Material Requirements Planning (MRP) lebih efisien daripada metode PT. XYZ. Oleh karena itu untuk mendapatkan total cost yang minimum, metode Material Requirements Planning (MRP) diterapkan pada periode Februari-Juni 2020 sehingga didapatkan total cost sebesar Rp 1.576.011.801,-. Kata Kunci:         Material Requirements Planning (MRP), PT XYZ, Pail Cat, Economic Order Quantity (EOQ), Period Order Quantity (POQ), Lot For Lot (LFL). ABSTRACT                     Inventory is a company asset that has an important role in business operations, so the company is important to conduct good inventory management, meaning that the company must be able to anticipate obstacles and challenges that exist in managing inventory to minimize the total cost to be incurred by the company.The problem that arises in the supply of raw materials in PT XYZ is that the company plans and controls raw materials based only on previous experiences and not based on established methods. Therefore, the purchase of raw materials is not in accordance with consumer demand. This often leads to excess or shortage of raw material stock. Mistakes in determining the amount of investment in inventories will reduce company profits. The availability of raw materials that are too large, will add to the burden of maintenance and storage costs in the warehouse, as well as the possibility of a decline in the quality of raw materials that can lead to reduced company profits. However, if the supply of raw materials is too little, it will result in obstruction of the production process, so that consumer demand is not fulfilled. The results of this study can conclude that the planning of raw material needs by the company method obtained a total cost of Rp 1,796,762,429, - while the Material Requirements Planning (MRP) method obtained a total cost of Rp 1,576,011,801, -. Then it can be concluded that there has been a decrease in the total cost of all raw materials by 12.28%. This proves that the Material Requirements Planning (MRP) method is more efficient than the PT. XYZ. Therefore, to get the minimum total cost, the Material Requirements Planning (MRP) method was applied in the February-June 2020 period so that a total cost of Rp 1,576,011,801 was obtained.   KeyWords: Material Requirements Planning (MRP), PT XYZ, Pail Cat, Economic Order Quantity (EOQ), Period Order Quantity (POQ), Lot for Lot (LFL).

OPTIMALISASI PENGADAAN BAHAN BAKU DALAM RANGKA MEMINIMALKAN TOTAL BIAYA PERSEDIAAN TEMBAKAU PADA PT BENTOEL INTERNATIONAL INVESTAMA DI MALANG

2019 ◽  
Vol 2 (1) ◽  
pp. 23
Author(s):  
Dwi Dayanti Oktavia ◽  
Peni Indarwati ◽  
Marhaerni Fikky Febriananta
Keyword(s):  
Production Process ◽  
Raw Materials ◽  
Cost Savings ◽  
Optimal Level ◽  
Raw Material ◽  
Economic Order Quantity ◽  
Economic Order ◽  
Order Quantity ◽  
Total Cost ◽  
The Cost

A company should maintain an adequate or optimal level of inventory so that production operations can run smoothly and efficiently. What needs to be considered in this case is that the required raw materials are always available, so as to guarantee the smooth production process. However, the amount of inventory should not be too much because this will harm the company. Too much inventory will increase maintenance costs and storage costs in the warehouse. In addition, the amount of inventory that is too much can also increase the likelihood of losses due to damage and loss of quality that can reduce company profits. And vice versa, the amount of inventory that is too small will hamper the production process so that the company will suffer a lot of losses including: the machine does not work as it should, many workers are unemployed, and can even result in the cessation of the production process. This study aims to determine how the calculation of raw materials, what is the total cost of raw material inventory if the company establishes an EOQ (Economic Order Quantity) policy, what is the limit or point of ordering raw materials needed by the company during the grace period at PT.Bentoel International Investama in Malang.The population used is the supply of tobacco raw materials at PT. Bentoel International Investama, where this research was conducted by interview and documentation. The variable in this study is the supply of raw materials. The analysis used is the EOQ (Economic Order Quantity) method.The results of the study, if using the EOQ method in 2017 the cost savings of Rp 40,290,256,931, while in 2018 the cost savings of Rp. 44,388,428,549. Thus there is a difference between inventory policies carried out according to the company with EOQ calculations. It can be concluded that the supply of raw materials every year has increased raw materials, the frequency of purchasing raw materials when using raw materials when using the EOQ method is 2 times in one period, the limit for ordering raw materials needed by companies when using the 2017 EOQ method is 218,176.7 kg, while in 2018 it will be 210,853 kg. The total cost of raw material inventory calculated according to EOQ is less than that spent by the company, so there is a cost savings of raw material inventory

scholarly journals ANALISA PENGENDALIAN PERSEDIAAN DAUN KAYU PUTIH YANG OPTIMAL DENGAN METODE CONTINOUS REVIEW SYSTEM DI PT. XYZ

2021 ◽  
Vol 16 (1) ◽  
pp. 106-117
Author(s):  
Enny Aryanny ◽  
Ragil Kusuma Jati
Keyword(s):  
Raw Materials ◽  
Raw Material ◽  
Lost Sales ◽  
Continuous Control ◽  
Review System ◽  
Total Cost ◽  
Continuous Review ◽  
Eucalyptus Oil ◽  
Inventory Costs ◽  
Eucalyptus Leaves

Persediaan adalah sumber daya yang perlu diadakan dan dipelihara untuk menunjang kelancaran produksi. PT. XYZ merupakan perusahaan yang bergerak di proses pembuatan minyak kayu putih. Perusahaan memproduksi minyak kayu putih dimana bahan baku utamanya adalah daun kayu putih. Perusahaan ini memiliki permasalahan dalam melakukan pengendalian persediaan bahan baku daun kayu putih yang disebabkan oleh permintaan minyak kayu putih oleh konsumen yang tidak menentu. Perusahaan mengalami keadaan persediaan yang berlebih yang mengakibatkan tingginya biaya persediaan dan kurangnya persediaan yang mengakibatkan produksi yang tidak memenuhi pesanan. Berdasarkan permasalahan di atas, maka dilakukan pengendalian persediaan dengan metode continuous review system backorder dan lost sales. Tujuan dari penelitian ini adalah melakukan pengendalian persediaan daun kayu putih sehingga dapat meminimumkan biaya persediaan. Metode continuous review system backorder dan lost sales akan dibandingkan dengan metode perusahaan dan dipilih metode terbaik dengan total biaya paling minimum. Hasil dari perhitungan diperoleh total biaya persediaan minimum dengan metode continuous review system backorder sebesar Rp 2.459.692.004, sedangkan metode perusahaan sebesar Rp 2.595.684.800, sehingga mendapatkan penghematan biaya sebesar Rp 135.992.796 dengan efisiensi sebesar 5,2%. Jumlah pemesanan bahan baku per pesan bulan November 2019 – Oktober 2020 sebesar 1.812 ton, dengan total biaya persedian bahan baku sebesar Rp 2.544.762.825.   Kata Kunci: Continuous, Pengendalian, Persediaan.   ABSTRACT Inventories are resources that need to be procured and maintained to support the continuity production. PT. XYZ is a company engaged in the process of making eucalyptus oil. The company produces eucalyptus oil where the main raw material is eucalyptus leaves. This company has problems in controlling the supply of raw materials of eucalyptus leaves caused by the erratic demand of eucalyptus oil by consumers. The company experiences a state of excess inventory which results in high inventory costs and lack of inventory resulting in production that does not fulfill orders. Based on the above problems, inventory control is carried out using the continuous review system backorder and lost sales method. The purpose of this study is to control the inventory of eucalyptus leaves so as to minimize inventory costs. The continuous review system backorder and lost sales method will be compared with the company method and the best method is chosen with the minimum total cost. The results of the calculation obtained the minimum total inventory cost with the continuous review system backorder method of Rp.2,459,692,004, while the company's method of Rp2,595,684,800, so as to get a cost savings of Rp.135,992,796 with an efficiency of 5.2%. The number of raw material orders per message in November 2019 - October 2020 amounted to 1,812 tons, with a total cost of supplying raw materials amounting to Rp 2,544,762,825.   Keywords: Continuous, Control, Inventory.

Comments on Two Models for Operating Two-Warehouse Inventory Systems with Deteriorating Items and Inflationary Effects

2011 ◽  
Vol 2 (2) ◽  
pp. 1-21
Author(s):  
Huachun Xiong ◽  
Jinxing Xie ◽  
Bo Niu
Keyword(s):  
Infinite Horizon ◽  
Planning Horizon ◽  
Inventory Systems ◽  
Traditional Model ◽  
Present Value ◽  
Total Cost ◽  
Demand Rate ◽  
Replenishment Cycle ◽  
The Cost ◽  
Infinite Planning Horizon

This paper deals with the two-warehouse partial backlogging inventory problems under inflation for a deteriorating product with a constant demand rate over an infinite horizon. In contrast to the traditional model in which each replenishment cycle starts with an instant replenishment and ends with shortages, an alternative model is proposed in recent literature in which each cycle starts with shortages. It is proven to be less expensive to operate than the traditional model in terms of the present value of the cost per unit time. The present paper points out that the criteria of minimizing the cost per unit time is unreasonable when the inflationary effect is taken into consideration, and instead, the criteria of minimizing the present value of the total cost over the whole infinite planning horizon should be used. The objective functions of these two models are changed and proved that the model with shortages at the start of the cycle is less expensive to operate than the traditional model in terms of the present value of the total cost, but the optimal solutions of the models minimizing the cost per unit time indicate significantly higher total costs.

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