Aggregate Planning Master Production Scheduling Materials Requirement Planning

  Dealing with the Problem Complexity through Decomposition Corporate Strategy Aggregate Unit

  Aggregate Planning Demand

  (Plan. Hor.: 1 year, Time Unit: 1 month) Aggregate Planning

  Capacity and Aggregate Production Plans (Perencanaan Agregat)

  End Item (SKU) Master Production Scheduling

  Demand (Plan. Hor.: a few months, Time Unit: 1 week)

  SKU-level Production Plans Manufacturing Materials Requirement Planning and Procurement

  (Plan. Hor.: a few months, Time Unit: 1 week) lead times Component Production lots and due dates

  Part process Shop floor-level Production Control plans

  (Plan. Hor.: a day or a shift, Time Unit: real-time)

  2 Aggregate Planning Inputs Pendahuluan

• Tujuan Aggregate planning (AP) adalah membangkitkan

  Resources Costs • • (generate) top level production plans

   Workforce  Inventory carrying  Back orders

   Facilities

• Basis AP adalah hasil ramalan dan target produksi. Target
•  Hiring/firing produksi ditentukan oleh top level business plan yang Demand forecast
•  Overtime memperhatikan kapasitas & kapabilitas perusahaan

  Policies  Inventory changes

   Subcontracting

•  Subcontracting Analisis dilakukan dalam kelompok produk (product family)

   Overtime dengan unit agregat  Inventory levels  Back orders

• Melibatkan pemilihan strategi manufaktur
• Peran AP adalah sebagai interface antara perusahaan/sistem manufaktur dan pasar produknya.

  Aggregate Planning Outputs Aggregate Planning Strategies

  Total cost of a plan Proactive

•  Alter demand to match capacity

  Projected levels of inventory

• Reactive

   Inventory  Alter capacity to match demand

   Output

• Mixed

   Employment  Some of each

   Subcontracting  Backordering

  5

  6 Demand Options Capacity Options

• Hire and layoff workers

  Pricing Overtime/slack time

• Part-time workers
• Promotion

  Inventories

• Subcontracting •

  Back orders

• New demand
• Maintain a level workforce

• Level capacity strategy:
• Maintain a steady output rate
• Match demand period by period
• Use a combination of decision
• Chase demand strategy:

  variables

  10 Basic Strategies Cumulative Graph Techniques for Aggregate Planning Figure 13.3

   Maintaining a steady rate of regular-time output while meeting variations in demand by a combination of options.

   Matching capacity to demand; the planned output for a period is set at the expected demand for that period.

9 Aggregate Planning Strategies

  Chase Approach

• Advantages
• Advantages

   Investment in inventory is low  Labor utilization in high

• Disadvantages
• Disadvantages

   The cost of adjusting output rates and/or workforce levels Level Approach

   Stable output rates and workforce

   Greater inventory costs  Increased overtime and idle time  Resource utilizations vary over time

1. Determine demand for each period

  Determine capacities for each period 2. d n a

  Identify policies that are pertinent 3. m e d

  Determine units costs 4. t/ u tp

  Develop alternative plans and costs 5. u o e

  Select the best plan that satisfies objectives. Otherwise 6. v Cumulative ti return to step 5. la production u m Cumulative u C demand

  1

  2

  3

  4

  5

  6

  7

  8

  9

  10

  13

  14 Mathematical Techniques Table 13.7

  Summary of Planning Techniques Linear programming: Methods for obtaining

  Technique Solution Characteristics optimal solutions to problems involving allocation of scarce resources in terms of cost

  Graphical/charting Heuristic (trial Intuitively appealing, easy to and error) understand; solution not minimization. necessarily optimal.

  Simulation models: Computerized models that Linear Optimizing Computerized; linear assumptions can be tested under different scenarios to programming not always valid. problems.

  Simulation Heuristic (trial Computerized models can be and error) examined under a variety of conditions.

  CONTOH : Perencanaan Aggregat Controllable (decision) variable

  Trial and Error dengan

• Inventory

  Diketahui demand selama 8 kuartal ke depan (hasil ramalan  lihat slide berikutnya)

• Production rate

  Ongkos produksi :

• Regular time (Cr): 10 (US$/unit)

  Manpower Over time (Co): 20 (US$/unit)

• Ongkos kenaikan tingkat produksi (Ch) : 100 US$/unit (hiring cost)

  Kapasitas: over time/recruitment/layoff (tenaga Ongkos penurunan tingkat produksi (Cl): 150 US$/unit  (lay-off kerja/work force) cost)

• Ongkos inventory (Ci): 50 US$/kuartal

  Subcontract Incremental cost for subcontracting (Cs): 80 US$/unit

  17

  18 Forecasted Demand Level Strategy per kuartal

  Production Adjusted Ongkos Kuartal Demand Inventory

• *)

  level Inventory inventory Kuartal Demand Kumulatif

  D em and per kuartal

  1 220 300 80 350 17,500 1 220 220

  2 170 300 210 480 24,000 d n 800

  2 170 390 a m

  3 400 300 110 380 19,000

  600

  e 3 400 790 d s

  400

  4 600 300 -190 80 4,000 a

  4 600 1390 it t n 200

  5 380 300 -270 5 380 1770 a u K

  6 200 300 -170 100 5,000 6 200 1970

  1

  2

  3

  4

  5

  6

  7

  8

  7 130 2100 7 130 300 270 13,500

  Kuartal

  8 300 2400 8 300 300 270 13,500 Total 96,500

• )

  Initial inventory: 270

  I R A P, O = jml unit yang diproduksi pada RT dan OT A, R = jml unit kenaikan dan penurunan r, v = ongkos produksi per unit RT dan OT c = ongkos simpan per unit D = ramalan demand I = jml unit inventory m, n = kapasitas RT dan OT

  1 O k t n

  1

  1 Min

  P k t m t t

  ..., 2, , 1 ; Subject to

  D k t O P

  I I t t t t t

  ..., 2, , 1 ;

  t t ..., 2, , 1 ;

  1

  P k t P A t t t

  ..., 2, ,

  1 P k t P R

  t t t ..., 2, ,

  1

  , , , , t t t t t

  O P

  1

  1

  21 Kuartal Demand Hiring Layoff Total 1 220 2 170 7,500 7,500 3 400 23,000 23,000 4 600 20,000 20,000 5 380 33,000 33,000 6 200 27,000 27,000 7 130 10,500 10,500 8 300 17,000 17,000

  20

  Total 138,000 Chase Strategy

  22 Production Incremental level Cost

  1 220 130 90 7,200 2 170 130 40 3,200 3 400 130 270 21,600

  4 600 130 470 37,600 5 380 130 250 20,000 6 200 130 70 5,600 7 130 130 8 300 130 170 13,600 Total 108,800

  Kuartal Demand Subcontract Subcontract Strategy

  Regular Additional Overtime Inventory Overtime Changing Production units needed Production cost cost work force

  1 220 200

  50

  I c O v R f A h P r Z

  30 30 1,500 1,000 2,500 2 170 200 -30 30 60 3,000 3,000 3 400 200 200

  50 -150 -90 1,000 9,000 10,000 4 600 200 400 50 -350 -350 1,000 26,000 27,000 5 380 200 180 50 -130 -130 1,000 33,000 34,000 6 200 200 19,500 19,500

  7 130 200 -70

  70 70 3,500 3,500 8 300 200 100 50 -50 20 1,000 1,000 2,000

  Total 101,500 Total

  Inventory after RT+OT

  Kuartal Demand

  Mixed Strategy Linear Programming k t k t t t k t t k t t k t t

• 1 ;
• 1 ;

25 Transportation Model(1)

  1

  2

  3

4 SubCont Regular Over time SubCont

  2

  3

  4 Over time SubCont Regular Over time SubCont Regular Over time Regular

  1 Inventory Transportation Model(3)

  Aggregat Planning Periode

  A. Production Planning

  Demand (unit) Produksi (unit)

  a. Regular

  b. Overtime Subkontrak (unit) Inventory (unit) 100 Backorder (unit) Stockout (unit)

  B. Financial Planning Penjualan (US$) Biaya (US$)

  1. Produksi

  a. Regular

  b. Overtime

  2. Subkontrak

  3. Inventory

  4. Backorder

  5. Stockout

  3

  2

  4

• 50 250 - 150
• 250 300
• 250 250 250 450 800 900 500 500 800 1.700 900

  500 - 500 395 305 215 125 250 - 250 420 330 240 150 300 200 500

  1

  RT 700 OT 250 SC 500 RT 800 OT 250 SC 500 RT 900 OT 250 SC 500 RT 500 OT 250 SC 500

  RT OT Subcontract 1 700 250 500 500 2 800 250 500 800 3 900 250 500 1700 4 500 250 500 900

  Supply capacity Perioda Demand

  Inventory awal: 100 unit

  Inventory akhir yang diinginkan: 150 unit Ongkos RT: $100/unit

  Ongkos OT: $125/unit Ongkos SC: $150/unit Ongkos simpan: $20/unit/perioda

  26 Transportation Model(3) Unused Available

  Perioda

  1

  2

  3

  4 Capacity Capacity Produksi Inventory awal 100

  Demand 500 800 1700 1050 6000

  500 500 280 190 100 120 900 - 900 305 215 125 145 250 - 250 330 240 150 170 250 250 500 370 280 190 100

  4 Sumber Perioda penjualan

  1

  2

  3 Transportation Model(2)

  Unused Available

  20

  40

  60

  50 50 - 100

  100 120 160 220 450 250 700 125 145 165 185 250 250 150 170 190 210 500 500 190 100 120 140 750

  50 - 800 215 125 145 165 250 - 250 240 150 170 190

  150.000 240.000 510.000 270.000

• 1.000 5.000 - 3.000
• 37.500 45.000
• 31.250 37.500 45.000 80.000 90.000 50.000

  46.000 85.000 158.750 135.500

  Total Biaya (US$ Proyeksi laba/rugi 104.000 155.000 351.250 134.500

  DEMAND 500 800 1.700 900 End-horizon Inventory

  STOCKOUT 250 250 250 250

  150 Periode Sumber Periode Capacity (unit)