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AGGREGATE PLANNING

AGGREGATE PLANNING. Proses peramalan  informasi jumlah produk Buat rencana produksi : upaya menjabarkan hasil peramalan menjadi rencana produksi yang layak untuk dilakukan. Salah satu metode  AGGREGATE PLANNING AGGREGATE PLANNING

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AGGREGATE PLANNING

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  1. AGGREGATE PLANNING

  2. Proses peramalan  informasi jumlah produk • Buat rencana produksi : upaya menjabarkan hasil peramalan menjadi rencana produksi yang layak untuk dilakukan. Salah satu metode  AGGREGATE PLANNING AGGREGATE PLANNING • Concerned with determining the quantity and timing of production for the intermediate future  3-8 months • To determine the best way to meet forecasted demand by adjusting production rates, labor levels, inventory levels, overtime work, subcontracting rates  minimizing cost • Use a logical overall unit for measuring sales and output  not individual unit product

  3. Examples: • Individual product Aggregate product • - Red car • Green car unit car • Blue car • Keripik tempe pedas • Keripik tempe manis bungkus keripik tempe/gr • Keripik tempe asin • Keuntungan penggunaan satuan agregat : • Kemudahan dalam pengolahan data • Ketelitian hasil yang diharapkan • Kemudahan memahami mekanisme sistem produksi yang terjadi dalam implementasi rencana.

  4. Several question need to be answered before applying aggregate planning • Should inventories be used to absorb changes in demand during the planning period? • Should changes be accommodated by varying the size of the workforce? • Should part timers be used, or should overtime and idle time adsorb fluctuation? • Should subcontractors be used on fluctuating orders so stable workforce can be maintained? • Should prices or other factors be changed to influence demand?

  5. Capacity options (Production Strategy) • Changing inventory levels • Increase inventory during periods of low demand to meet high demand in the future periods • Varying workforce size by hiring or lay offs • Hire or lay off production workers to match production rates • Varying production rates through overtime and idle time • Keeping constant workforce while varying hours may be possible • Subcontracting • Subcontracting work during peak demand periods • Using part-time workers • Use part time workers  service sector TO ANSWER FLUCTUATION DEMAND

  6. Pure Mixing Options • Level Strategy • Equal amount produced each period • Steady employment • Vary inventory to meet variations in demand • Inventory costs or the expense of a shortage • Service – constant but poor utilization: • Too large - poor utilises workforce • Too small – lose some demand to competitor

  7. Chase Demand • Production identical to demand for the period • Vary the work-force • Overtime or hiring and laying (high costs) • No inventory cost, no shortage cost • Service – overtime, split shifts, overlapping shifts, call-in workers, part-time

  8. PERENCANAAN AGREGAT DENGAN METODE GRAFIS • Melihat gambaran permintaan kumulatif dan rata-rata permintaan kumulatif. Tahap-tahap : • Gambarkan histogram permintaan dan tentukan kecepatan produksi (Pt) rata-rata yang diperlukan untuk memenuhi permintaan. 2. Gambarkan grafik permintaan kumulatif terhadap waktu serta grafik permintaan rata-rata kumulatif terhadap waktu. Identifikasikan periode tempat terjadinya kekurangan (back order) dan periode-periode adanya kelebihan (inventory) 3. Tentukan strategi yang akan digunakan untuk menanggulangi kelebihan dan kekurangan barang tersebut.

  9. 4. Hitung ongkos yang ditimbulkan oleh setiap strategi dan pilih ongkos terkecil. DATA PERMINTAAN UNTUK 8 PERIODE MENDATANG : Persediaan Awal : I t - 1 = 0 Back Order = Rp. 100,-/unit/bl Ongkos sub kontrak = Rp. 800/Unit. Ongkos untuk menaikkan produksi= Rp. 1.000,-/Unit Ongkos simpan / penundaan = Rp. 50,-/Unit/periode Ongkos untuk menurunkan produksi = Rp. 1.500,-/Unit Rencanakan kecepatan produksi (Pt) selama 8 periode yad

  10. Solusi :1. Histogram Demand dan Pt. Dt Pt = 300 t

  11. Plot demand kumulatif vs t dan Demand rata-rata kumulatif vs t.

  12. back order Dt Produksi rata- rata kumulatifdemand kumulatif inventory t

  13. STRATEGI YANG DIGUNAKAN:a. Tenaga kerja diasumsikan sama dengan pola permintaan - ongkos merekrut (menaikan produksi) - ongkos memberhentikan (menurunkan produksi)b. Inventory, menyediakan persediaan pada awal periode yang mungkin  ongkos persediaan.c. sub kontrak, memberikan sebagian produksi pada pihak luar  ongkos sub kontrak.4. Perhitungan ongkos dari setiap strategi 4.1. Perencanaan tenaga kerja  Rumus dasar : Pt = Dt – It-1 + It

  14. 4.2. Mengadakan persediaan, tingkat produksi KONSTAN

  15. 4.3. Sub kontrak

  16. PERENCANAAN AGREGAT DENGAN MODEL TRANPORTASI (LAND)Contoh :Permintaanselama 4 periodesertasumberdaya yang dimilikinyaselama 4 periodetersebut, sbb :

  17. Diketahui pula bahwa pada periode 1 sudah terdapat persediaan awal sebesar 100 unit dan pada akhir periode 4 diinginkan adanya persediaan sebesar 150 unit. Ongkos produksi pada jam kerja biasa (reguler time)Rp. 100/unit, pada jam kerja lembur (over time) Rp. 125/unit, ongkos untuk mengadakan sub kontrak Rp. 150/unit dan untuk menyimpan produk di kenakan ongkos Rp. 20,-/unit/periode.

  18. Contoh soal :Sun Valley ski company, which produces the famous sun ski, has a production cost of $ 60 per pair during regular time and $ 70 per pair on overtime. The firm’s production capacity and forecast demand as shown below :Period (quarter) :Forecast demand : 900 500 200 1900 units Beginning inventory is 200 pair, and stock is carried at a cost of $ 5 per pair-quarter. Demand is to be met without any hiring, layoff, subcontracting, or back orders. Unused regular time has a cost of $ 20/pair 1 2 3 4

  19. ContohMichigan manufacturing produces a product which has a 6-month demand cycle, as shown. Each unit requires 10 worker-hour to be produces, at a labor cost of $ 6 per hour regular rate (or $ 9 per hour over time). The total cost per unit is estimated at $200, but unit can be subcontracted at a cost $208 per unit. There are currently 20 workers employed in the subject department, and hiring and training cost costs for additional workers are $300 per person, where as layoff cost are $400 per person. Company policy is to retain a safety stock equal to 20 % of the monthly forecast,

  20. Lanjutan Contoh :and each months safety stock becomes the beginning inventory for the next month. There are currently 50 units in stock carried at a cost of $2 per unit-month stock outs have been assigned a cost of $20 per unit-month.

  21. Three agregate plans are proposed :Plan 1 : vary the work-force size to accommodate demand Plan 2 : Maintain a constant work force of 20 and use overtime and idle time to meet demand.Plan 3 : Maintain a constant work force of 20 and build inventory on incur a stockout costThe firm must begin January with the 50 unit inventory on hand

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