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10/14/2010
1
PERENCANAAN AGREGAT
Kuliah 3
LSiPro – FT Untirta
Muhammad Adha Ilhami
Muhammad Adha Ilhami
Tujuan Pembelajaran
• Mahasiswa mampu menggunakan teknik
agregasi
• Mahasiswa mampu menyusun Master
Production Schedule (MPS) atau Jadwal Induk
Produksi (JIP).
Muhammad Adha Ilhami
Pemahaman Dasar
• Bahwa aggregate plan (AP) merupakan tahapperencanaan awal dimana hasilnya adalah MPS (Top Level Production Plan) dan dilakukan oleh Top Level
Business Plan.
• AP memperhatikan kapasitas dan kapabilitasperusahaan.
• Analisa AP dilakukan dalam kelompok produk (product family) dengan unit agregat.
• AP melibatkan pemilihan strategi manufaktur.
• AP berperan dalam sebagai interface antaraperusahaan/sistemmanufaktur dan pasar produknya.
Muhammad Adha Ilhami
Company Top Level Plan
Muhammad Adha Ilhami
• Alur informasi
dalam AP.
• Data (input)
dan Hasil
(output) AP.
10/14/2010
2
Planning Horizon
Muhammad Adha Ilhami
Aggregate planning: Perencanaan kapasitas jangkamenengah, biasanya dilakukan untuk 2 sampai 12 bulan. AP prinsipnya menyesuaikan kapasitas dan permintaan
Shortrange
Intermediate range
Long range
Now 2 months 1 Year
Overview of Planning Level
Muhammad Adha Ilhami
• Short-range plans (Detailed plans)– Machine loading
– Job assignments
• Intermediate plans (General levels)– Employment
– Output
• Long-range plans– Long term capacity
– Location / layout
– Product/Process design
Why Aggregate Plan?
Muhammad Adha Ilhami
• Detil lebih sulit diperoleh untuk waktu yang lebih panjang
• Detil membawa banyak ketidakpastian: agregasi yang dilakukanditujukan mengurangi variabilitas– Permintaan total pakaian lebih sedikit mengandung bias dibandingkan
permintaan kaos, celana, dan kemeja.
• Jika terdapat variabilitas kenapa repot-repot membuat rencanadetil, bagaimanapun juga input akat berubah.– Buat rencana yang fleksibel
– Fleksibilitas dan agregasi biasanya sejalan
Rencana Agregat
Muhammad Adha Ilhami
Strategi perencanaan dalam tahapan Perencanaan dan
Pengendalian Produksi yang bermuara pada perencanaan
kapasitas yang optimal.
Proses agregasi (aggregation) ialah pengelompokan beberapa
jenis item menjadi product family.
Proses disagregasi (disaggregation) adalah proses derivasi
product family menjadi item.
10/14/2010
3
Istilah Berkaitan dengan Produk
Muhammad Adha Ilhami
• Type: kelompok beberapa product families.
• Product family: kelompok beberapa items.
• Item: produk akhir individual yang dibeli (digunakan) oleh konsumen.
• Biasanya hirarki tersebut dimulai dari product family, karena bila sebuah pabrik membuat lebih dari satu jenis type maka operasi perusahaan itu akan menjadi sangat kompleks.
• Pengelompokan sejumlah item ke dalam sebuah product
family dilakukan dengan teknik Group Technology (GT).
Satuan Agregat
Muhammad Adha Ilhami
• Unit agregat yang biasa
digunakan dalam proses
agregasi :
Jam kerja buruh, mesin atau
resource lainnya.
Waktu standar.
Harga jual, Ongkos produksi.
Satuan agregat dummy
(pseudo product).
Aggregate plan units
Muhammad Adha Ilhami
• At this level of planning, there is not a lot of detail. Individual end product identity is typically not present. Instead, planning is performed for a composite, or average unit of product in a particular family of similar products. For example, we may plan for units of hair dryers, without regard for whether they are 1500 watt dryers, 1600 watt dryers, 1875 watt dryers, travel dryers, etc.
• Decisions are typically aggregated into monthly time periods. Weekly or daily detail is not needed at this level of decision making. Those finer time breakdowns will be made at lower levels of decision making still to come.
Contoh Proses Agregasi
Muhammad Adha Ilhami
IBM memproduksi komputer laptop, desktop, notebook dan mesin teknologi tinggi lainnya. Proses agregasi adalah pengelompokkan jenis – jenis komputer tersebut ke dalam family product (misalnya famili komputer).
Sebuah rumah sakit bisa melakukan agregasi jasa yang diberikan menjadi jumlah perawat atau dokter yang dibutuhkan.
PT. Telkomsel bisa melakukan agregasi jumlah unit penjualan kartu prabayar (kartu simpati) dan kartu pascabayar (kartu hallo) menjadi jumlah rupiah penjualan yang diterima. Kartu hallo juga terdiri dari beberapa item.
10/14/2010
4
Prinsip Aggregate Plan
Muhammad Adha Ilhami
• Aggregate planning: General plan
– Combined products = aggregate product
• Short and long sleeve shirts = shirt – Single product
– Pooled capacities = aggregated capacity
• Dedicated machine and general machine = machine– Single capacity
– Time periods = time buckets
• Consider all the demand and production of a given month together
– Quite a few time buckets
– When does the demand or production take place in a time bucket?
Aggregate Plan Input
Muhammad Adha Ilhami
• Sumber daya
– Tenaga Kerja
– Fasilitas
• Ramalan Permintaan
• Statemen KebijakanPerusahaan
– Subkontrak
– Overtime
– Tingkat Persediaan
– Back order
• Biaya
– Biaya inventori
– Biaya back order
– Biaya Hiring/firing
– Biaya Overtime
– Biaya subkontrak
Aggregate Plan Output
Muhammad Adha Ilhami
• Biaya total Perusahaan
• Projected levels of inventory
– Inventory
– Output
– Employment
– Subcontracting
– Backordering
Strategi Umum AP
Muhammad Adha Ilhami
• Proactive
– Mengubah demand menyamai kapasitas.
• Reactive
– Mengubah kapasitas menyamai permintaan.
• Mixed
– Gabungan proaktif dan reaktif
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5
NATURE OF THE AGGREGATE
PLANNING PROBLEM
Muhammad Adha Ilhami
Time
1 year
Demand Forecast
Regular (or Normal) Capacity Limit
Units of
“Aggregate”
Product
AGGREGATE PLANNING STRATEGIES
Muhammad Adha Ilhami
Aggregate Planning Strategies
Operations Oriented Marketing Oriented
Leveling strategyChase strategy
Shifting demandCounter seasonal products
Operation Oriented
Muhammad Adha Ilhami
Strategi untuk mengatasi demand yang berfluktuasi dikategorikan
sebagai strategi berorientasi operasi atau berorientasi market/pasar.
Leveling strategy: Maintain output at a constant (level) rate
throughout the planning horizon. Accommodate seasonal variations
in demand through the accumulation and depletion of inventories.
Chase strategy: Vary the output rate to match the seasonal
variations in demand. Output rate can be varied by (1) hiring and
firing workers, (2) utilizing overtime and idle time, or (3)
subcontracting.
Hybrid strategy: A cost effective aggregate plan may require the use
of a combination of the pure strategies listed above. Such a plan is
referred to as a hybrid plan.
Marketing Oriented
Muhammad Adha Ilhami
Strategi/taketik marketing berhubungan dengan demand siklis.
Ilustrasi :
Biasanya produksi tertentu (tetap) namun jika demand berada di
bawah produksi,maka marketing harus diandalkan sehingga demand
setara dengan produksi.
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6
Alur Proses Pengolahan Data –
Peramalan – Rencana Agregat
Muhammad Adha Ilhami
Item Family Family
Data
Data ProdukA
Data ProdukB
Data ProdukC
PeramalanFamily
PerancanganAgregatFamily
Disagregasi
Disagregasi
Disagregasi
MPS
Agregasi
Agregasi
Agregasi
Data
Data familyA
Data familyB
Data familyC
Peramalan Family
Peramalan Family
Peramalan Family
PerancanganAgregatFamily
PerancanganAgregatFamily
PerancanganAgregatFamily
Disagregasi
Disagregasi
Disagregasi
MPS
Agregasi
Agregasi
Agregasi
Contoh Hasil Peramalan Permintaan
(Dalam agregat)
Muhammad Adha Ilhami
Month
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Demand Forecast100 150 250 400 250 50 90 160 260 390 240 60
Additional DataHiring cost: $200 per worker hiredFiring cost: $100 per worker firedRegular pay: $5000 per worker per monthOvertime pay: 1.5 times regular payInventory carrying cost: $10 per unit (based on end of month balances)Backorder cost: $20 per unit (based on end of month shortage)Productivity: 10 units per worker per month (this has also been scaled down from what was originally expressed in thousands of units per month)Beginning workforce size: 20 workers (available at the beginning of January)Beginning inventory: 0 units (no inventory available at the beginning of January)
LEVEL STRATEGY WITH INVENTORY
AND BACKORDERS• Total annual demand = 2,400 units.
• Average monthly production needed = 2,400 units/12 months = 200 units per month.
• Current work force size is 20 workers. This is just enough (because productivity = 10 units per
worker per month).
Muhammad Adha Ilhami
Month JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Demand Forecast 100 150 250 400 250 50 90 160 260 390 240 60
Production 200 200 200 200 200 200 200 200 200 200 200 200
Beginning Inv. 0 100 150 100 -100 -150 0 110 150 90 -100 -140
Ending Inv. 100 150 100 -100 -150 0 110 150 90 -100 -140 0
Carrying Cost 1000 1500 1000 1100 1500 900
Backorder Cost 2000 3000 2000 2800
Regular Labor Cost 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000
Overtime Cost
Total Inventory Carrying Cost: $7,000Total Backorder Cost: $9,800Total Hiring Cost 0Total Firing Cost 0Total Regular Payroll Cost: $1,200,000Total Overtime Payroll Cost: 0Total Annual Cost: $1,216,800
LEVEL STRATEGY WITH SUBCONTRACT
• Total annual demand = 2,400 units.
• Average monthly production needed = 2,400 units/12 months = 200 units per month.
• Current work force size is 20 workers. This is just enough (because productivity = 10 units per
worker per month). Subcontract fee is $30 per unit.
Muhammad Adha Ilhami
Month JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Demand Forecast 100 150 250 400 250 50 90 160 260 390 240 60
Production 200 200 200 200 200 200 200 200 200 200 200 200
Beginning Inv. 0 100 150 100 -100 -150 0 110 150 90 -100 -140
Ending Inv. 100 150 100 -100 -150 0 110 150 90 -100 -140 0
Carrying Cost 1000 1500 1000 1100 1500 900
Subcontract Cost 3000 4500 3000 4200
Regular Labor Cost 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000
Overtime Cost
Total Inventory Carrying Cost: $7,000Total Subcontract Cost: $14,200Total Hiring Cost 0Total Firing Cost 0Total Regular Payroll Cost: $1,200,000Total Overtime Payroll Cost: 0Total Annual Cost: $1,221,200
10/14/2010
7
CHASE STRATEGY WITH HIRING AND
FIRING• Total annual demand = 2,400 units.
• Average monthly production needed = 2,400 units/12 months = 200 units per month.
• Current work force size is 20 workers. This is just enough (because productivity = 10 units per
worker per month).
Muhammad Adha Ilhami
MonthJAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Demand Forecast 100 150 250 400 250 50 90 160 260 390 240 60
Workers Needed 10 15 25 40 25 5 9 16 26 39 24 6
Number Hired 5 10 15 4 7 10 13
Number Fired 10 15 20 15 18
Hiring Cost 1,000 2,000 3,000 800 1,400 2,000 2,600
Firing Cost 1,000 1,500 2,000 1,500 1,800
Labor Cost 50,000 75,000 125,000 200,000 125,000 25,000 45,000 80,000 130,000 195,000 120,000 30,000
Overtime Cost
Total Inventory Carrying Cost: 0Total Backorder Cost: 0Total Hiring Cost $12,800Total Firing Cost $7,800Total Regular Payroll Cost: $1,200,000Total Overtime Payroll Cost: 0Total Annual Cost: $1,220,600
CHASE STRATEGY WITH OVERTIME
AND IDLE TIME• Total annual demand = 2,400 units.
• Average monthly production needed = 2,400 units/12 months = 200 units per month.
• Current work force size is 20 workers. This is just enough (because productivity = 10 units per
worker per month).
Muhammad Adha Ilhami
MonthJAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Demand Forecast 100 150 250 400 250 50 90 160 260 390 240 60
Capacity * 20 20 20 20 20 20 20 20 20 20 20 20
Capacity Needed * 10 15 25 40 25 5 9 16 26 39 24 6
Overtime * 5 20 5 6 19 4
Idle Time * 10 5 15 11 4 14
Regular Labor Cost 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000
Overtime Cost 37,500 150,000 37,500 45,000 142,500 30,000
Total Inventory Carrying Cost: 0Total Backorder Cost: 0Total Hiring Cost 0Total Firing Cost 0Total Regular Payroll Cost: $1,200,000Total Overtime Payroll Cost: $442,500Total Annual Cost: $1,642,500
Pilih Yang Mana?
Muhammad Adha Ilhami
Total Inventory Carrying Cost: $7,000Total Backorder Cost: $9,800Total Hiring Cost 0Total Firing Cost 0Total Regular Payroll Cost: $1,200,000Total Overtime Payroll Cost: 0Total Annual Cost: $1,216,800
Total Inventory Carrying Cost: 0Total Backorder Cost: 0Total Hiring Cost $12,800Total Firing Cost $7,800Total Regular Payroll Cost: $1,200,000Total Overtime Payroll Cost: 0Total Annual Cost: $1,220,600
Total Inventory Carrying Cost: 0Total Backorder Cost: 0Total Hiring Cost 0Total Firing Cost 0Total Regular Payroll Cost: $1,200,000Total Overtime Payroll Cost: $442,500Total Annual Cost: $1,642,500
Apa Konsekwensinya?
Level Inventory & Backorder Chase Fired & Hired
Chase Overtime & Idletime
Total Inventory Carrying Cost: $7,000Total Backorder Cost: $14,200Total Hiring Cost 0Total Firing Cost 0Total Regular Payroll Cost: $1,200,000Total Overtime Payroll Cost: 0Total Annual Cost: $1,221,200
Level Subcontract
Linear Programming
Muhammad Adha Ilhami
Keterangan:
r : ongkos produksi per unit reg time
P : jumlah unit yang diproduksi reg time
h : ongkos kenaikan per unit produk
At : jumlah unit kenaikan produksi
f : ongkos penurunan per unit produk
Rt : jumlah unit penurunan produksi
v : ongkos produksi per unit overtime
Ot : jumlah unit diproduksi overtime
c : ongkos inventori per unit
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