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Optimizing multi-item EPQ under defect and rework: A case in the plastic molding industry Nafisah, Laila; Sinaga, Rika Apriyanti Magdalena; Soepardi, Apriani; Salma, Melati; Irianto , Irianto
OPSI Vol 18 No 1 (2025): OPSI - June 2025
Publisher : Jurusan Teknik Industri, Fakultas Teknologi Industri UPN "Veteran" Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31315/opsi.v18i1.14740

Abstract

Product availability is a key indicator of service performance and is closely linked to production planning. Inaccurate decisions in lot sizing may lead to either overstock or stockout, resulting in substantial financial losses. Classical Economic Production Quantity (EPQ) models generally assume perfect quality and ignore real-world factor such as defects, rework, and backorders. This study proposes an extended EPQ model for multi-item production systems that integrates random defect rates, rework, and backordering within a single framework. Unlike previous studies that focus on single-item scenarios or deterministic defect rates, this model reflects a more realistic setting faced by companies by accounting for stochastic defects, the cost of crushing and rework, and customer backorder fulfillment. The model aims to determine the optimal lot size and production cycle that minimize the total inventory-related costs. The proposed model is validated using real case data from a plastic molding company. Results show that the model yields cost savings of 0.19% compared to the current company policy. Although modest, these savings are significant when scaled across production periods. More importantly, the model demonstrates strong adaptability to operational constraints and provides a practical decision-support tool for industries managing multiple products, quality variation, and uncertain demand.
Determining the International Hub Port on Sumatra Island Using the Integration of Geographic Information System and Analytical Hierarchy Process Methods Setijadi, Setijadi; Hartati, Verani; Fauzi, Muchammad; Salma, Melati
Spektrum Industri Vol. 23 No. 2 (2025): Spektrum Industri - October 2025
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/si.v23i2.361

Abstract

Indonesia’s maritime trade development heavily depends on the effective utilization of its port infrastructure, particularly in Sumatra, which is strategically located along the Malacca Strait and near major ASEAN markets. However, trade and logistics activities remain concentrated in Java, creating regional imbalances and leaving western Indonesian ports underutilized. This study aims to identify the most strategic ports in Sumatra that can serve as international trade hubs by developing a spatially integrated, multi-criteria evaluation framework. Three main criteria, trade volume, global connectivity, and multimodal accessibility, were assessed using the Analytic Hierarchy Process (AHP) based on expert input from port management, logistics, and transport planning specialists. Geographic Information System (GIS)-based proximity analysis was applied to evaluate each port’s access to roads, railways, and industrial centers, producing a Multimodal Connectivity Index integrated into the AHP model. The findings reveal that Boom Baru (Palembang), Belawan (Medan), and Batu Ampar (Batam) rank as the top-performing ports, with final scores of 0.875, 0.855, and 0.800, respectively. These ports exhibit high trade volumes and superior multimodal connectivity, with Boom Baru and Belawan achieving the highest connectivity index (2.67 out of 3.00). In contrast, Pekanbaru and Tanjung Balai Karimun scored lower due to limited infrastructure and weaker integration. The study concludes that incorporating GIS-based spatial analysis into the AHP framework reduces subjectivity in port evaluation and provides a replicable, data-driven tool for regional infrastructure prioritization. This approach contributes a novel composite index and offers strategic insights for developing Sumatra’s role in Indonesia’s maritime trade network.
Evaluasi dan Perbandingan Kinerja Manajemen Gudang di Garut Menggunakan Integrasi Metode AHP-SAW Hatala, Muhammad Hudzaly; Fatliana, Anggun Nindy; Rahmad, Nuraini; Walenna, A. M. Adhitya A.; Krisnasari, Dea Dita; Salma, Melati; Mardika, Riski Arif; Putra, Azhar Syafiq
Jurnal Kalibrasi Vol 23 No 2 (2025): Jurnal Kalibrasi
Publisher : Institut Teknologi Garut

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33364/kalibrasi/v.23-2.2656

Abstract

This study aims to evaluate and compare warehouse management performance in Garut Regency based on five main variables: warehouse layout, equipment, SOP standards, human resources (HR), and occupational health and safety (K3). A mixed-method approach was applied, where the Analytical Hierarchy Process (AHP) was used to determine the weight of each variable, while the Simple Additive Weighting (SAW) method was employed to calculate the total performance score (utility score) and rank warehouses according to the weighted scores of each variable. Data were collected from eight different warehouses through direct observation, interviews, and warehouse check-up audits using a Likert scale. The results show that warehouse layout holds the highest weight at 44.95%, followed by SOP at 23.67%, equipment at 15.02%, HR at 9.75%, and K3 at 6.62%. Warehouse 5 achieved the highest performance score of 94%, indicating the most optimal warehouse management due to its strong performance in layout and K3, as well as high utility scores in the other variables. In contrast, Warehouse 6 obtained the lowest score of 58%, mainly due to poor layout, limited equipment, and weak SOP, highlighting the need for significant improvements. These findings emphasize that layout and SOP are the most dominant factors in determining warehouse management effectiveness, while the other variables serve as supporting elements. The results also indicate that larger-scale companies tend to achieve higher utility scores, reflecting greater maturity across the five evaluated variables.
Optimasi Pengendalian Persediaan Gas Oxygen dan Acetylene Melalui Evaluasi ROP ROQ Berbasis Forecasting di PT Kaltim Prima Coal Yovanka Syulah Pertiwi; Faishal Arham Pratikno; Melati Salma
Journal of Industrial Innovation and Safety Engineering (JINSENG) Vol 3 No `1 (2025): JINSENG Volume 3 Nomor `1 January 2025
Publisher : Fakultas Rekayasa dan Teknologi Industri

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.35718/jinseng.v3i`1.8481988

Abstract

This internship aims to evaluate and optimize the inventory control of industrial oxygen and acetylene gas at PT Kaltim Prima Coal, which is managed under a closed-loop system. The main issues are the mismatch between the Reorder Point (ROP) and Reorder Quantity (ROQ) parameters in the Ellipse system and actual demand fluctuations, as well as an imbalance in bottle distribution that causes stockouts in the warehouse. The solution methods include statistical analysis of historical data from 2024–2025, forecasting using Exponential Smoothing, recalculation of ROP/ROQ based on three lead time scenarios, and determination of the ideal number of cylinders using the Demand During Lead Time approach. Analysis results indicate that the best forecasting method for oxygen is Exponential Smoothing with α=0.3 (MAPE 15.86%) and for acetylene, α=0.5. Recalculations using actual lead times resulted in an oxygen ROP of 22 bottles (4-day lead time) and an acetylene ROP of 29 bottles (11-day lead time), significantly different from the existing parameters (oxygen ROP=3, acetylene ROP=0). The ideal number of bottles in the system is 95 bottles for oxygen and 91 bottles for acetylene, while the actual inventory of 103 oxygen bottles and 87 acetylene bottles indicates that the root cause is not a shortage of bottles, but rather an imbalance in distribution across cycle points. The primary recommendation is to accelerate bottle returns and even out distribution without needing to increase the total bottle inventory.
Analisis Risiko Keselamatan Kerja Awak Mobil Tangki (AMT) Pada PT XYZ Dengan Metode HIRADC dan JSA Rachel Abigail; Faishal Arham Pratikno; Melati Salma
Journal of Industrial Innovation and Safety Engineering (JINSENG) Vol 4 No 2 (2026): JINSENG Volume 4 Nomor 2 July 2026
Publisher : Fakultas Rekayasa dan Teknologi Industri

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.35718/jinseng.v4i2.8482028

Abstract

Tanker Truck Operator (AMT) is a high-risk job because it involves direct contact with flammable materials, unpredictable road conditions, and complex operational pressures. Hazards such as fires, explosions, and loss of vehicle control can have fatal consequences for both workers and the environment. This is underscored by a 2025 workplace accident involving a tanker truck due to a vehicle system failure at PT XYZ, demonstrating that sources of danger stem not only from work behavior but also from technical aspects of the equipment. This study aims to identify potential hazards, analyze risk levels before and after control measures are implemented, and determine appropriate control measures for AMT work activities at PT XYZ. The methods used were Hazard Identification, Risk Assessment, and Determining Control (HIRADC) and Job Safety Analysis (JSA), through direct observation of each stage of the activities and interviews with the HSSE Supervisor at PT XYZ. The results of the study indicate the presence of potential hazards in the gate-in, filling shed, and distribution processes, with varying risk levels. Before control measures were implemented, several risks were categorized as “very high,” including undetected vehicle damage, incomplete use of PPE, and loss of vehicle control. Control measures were implemented through the application of Pre-Trip Inspections as the primary mitigation step to significantly reduce risk levels and comprehensively protect the occupational safety of AMT personnel.