EVALUASI KEBIJAKAN PERSEDIAAN BAHAN BAKU KANTONG SEMEN UNTUK MENGURANGI BIAYA PERSEDIAAN (Studi Kasus: PT. SOLUSI BANGUN INDONESIA TBK).

This study aims to evaluate company policy in determining raw material ordering rates which are then compared with the EOQ, POQ, and Min-Max methods. This research uses a quantitive case study method using data obtained from the company. Forecasting is done using WinQSB and MAD, MSE and MAPE software for forecasting accuracy. Based on data processing, the data shows the horizontal pattern and the chosen forecasting method is the Simple Average method. Research shows the EOQ method has an order quantity of 1192 units / order with an order frequency of 11 times a year and has the smallest total inventory cost of the three methods compared which is Rp 269,520,852,781 or almost 50% lower than the total costs incurred by the company using the current method. ROP point has a value of 3395 units with a safety stock value of 106 units.AbstrakPenelitian ini bertujuan untuk mengevaluasi kebijakan perusahaan dalam menentukan tingkat pemesanan bahan baku yang kemudian dibandingkan dengan metode EOQ, POQ dan Min-Max. Penelitian ini menggunakan metode studi kasus kuantitatif dengan menggunakan data yang diperoleh dari perusahaan. Peramalan dilakukan menggunakan perangkat lunak WinQSB dan MAD, MSE dan MAPE untuk akurasi peramalan. Berdasarkan pengolahan data, data menunjukkan pola horizontal dan metode peramalan yang dipilih adalah metode Simple Average. Penelitian ini menunjukkan metode EOQ memiliki jumlah pesanan 1192 unit / pesanan dengan frekuensi pemesanan 11 kali setahun dan memiliki total biaya persediaan terkecil dari ketiga metode yang dibandingkan yaitu Rp 269.520.852 atau hampir 50% lebih rendah dari total biaya yang dikeluarkan oleh perusahaan dengan metode saat ini. Titik ROP memiliki nilai 3395 unit dengan nilai stok pengaman 106 unit.

Integrated optimisation for production capacity, raw material ordering and production planning under time and quantity uncertainties based on two case studies

This paper develops a supply chain (SC) model by integrating raw material ordering and production planning, and production capacity decisions based upon two case studies in manufacturing firms. Multiple types of uncertainties are considered; including: time-related uncertainty (that exists in lead-time and delay) and quantity-related uncertainty (that exists in information and material flows). The SC model consists of several sub-models, which are first formulated mathematically. Simulation (simulation-based stochastic approximation) and genetic algorithm tools are then developed to evaluate several non-parameterised strategies and optimise two parameterised strategies. Experiments are conducted to contrast these strategies, quantify their relative performance, and illustrate the value of information and the impact of uncertainties. These case studies provide useful insights into understanding to what degree the integrated planning model including production capacity decisions could benefit economically in different scenarios, which types of data should be shared, and how these data could be utilised to achieve a better SC system. This study provides insights for small and middle-sized firm management to make better decisions regarding production capacity issues with respect to external uncertainty and/or disruptions; e.g. trade wars and pandemics.