manajemen operasional produksi

Rahma Rei Sakura, S.T., M.T.
NIP. 153112
MANAJEMEN OPERASIONAL PRODUKSI - 16027304
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AGGREGATE
PLANNING
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Process planning
Long
range
Strategic capacity planning
Intermediate
range
Forecasting
& demand
management
Sales and operations (aggregate) planning
Sales plan
Manufacturing
Aggregate operations plan
Services
Master scheduling
Material requirements planning
Short
range
Order scheduling
Weekly workforce and
customer scheduling
Daily workforce and customer scheduling
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Introduction
Warehouse
Food Mart
Aggregate Planning
Retailer
Factory
End
Consumer
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Contoh :
Sebuah perusahaan menjual beberapa kelompok produk dibeberapa wilayah
yang berbeda, maka ramalan bisa dibuat secara agregat untuk semua
kelompok produk dan semua wilayah, atau untuk setiap kelompok produk,
setiap wilayah, atau bahkan pada level yang lebih detail yaitu pada level
individu produk.
Agregasi juga dapat dibuat berdasarkan waktu, sehingga angka ramalan
dapat dibuat untuk periode harian, mingguan, bulanan, atau tahunan.
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Tujuan utama dari aggregate planning yaitu untuk menentukan
kombinasi dari production rate, work-force level, dan inventory on hand.
• Production Rate  jumlah unit yang diproduksi untuk setiap periode
tertentu.
• Work-force level  jumlah pekerja yang dibutuhkan untuk setiap
produksi pada periode tertentu. (production = production rate x
workforce level).
• Inventory on hand  jumlah persediaan yang tidak digunakan dari
periode sebelumnya.
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Introduction

Definisi  the aggregate planning consists of determining how feasible
production alternatives must be employed in each period to satisfy expected
demand at minimum total production cost. (Kostas N. Dervitsiotis, 1981)

Suatu pernyataan tingkat produksi yang direncanakan dalam bentuk aggregate yang
mengintegrasikan antara operasi manufaktur dengan rencana marketing dan bisnis.
Melibatkan pemilihan strategi manufaktur.
Input utama untuk Resource Planning.
Menstabilkan produksi dan tenaga kerja apabila pola demand bervariasi.
Dinyatakan dalam bentuk famili atau group produk, bukan specific model.




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Introduction

Ukuran unit pada setiap perusahaan berbeda-beda (ton, gallon, cases, yards,
kubik atau berdasarkan input yang digunakan dalam produksi seperti man hours
atau machine hours).
Note : digunakan untuk faktor konversi agar perencanaan produksi dapat secara
langsung dikaitkan dengan rencana marketing dan bisnis

Untuk produk dimana unit dalam family relatif homogen dapat dinyatakan dalam
unit produk (cost dollars).

Format tidak standard.
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Production Plan
(Make To Order)
PRODUCTION PLAN
Product Family :
Unit of Measure :
MONTH
WORKING DAYS
Forecast
Order Backing
Production Plan
Planned Daily Rate
Shipping Forecast
Pumps
Dollars at cost
JAN
PAST DUE
22
568,724
175,423 568,724
623,075
28,322
623,075
MANAJEMEN OPERASIONAL PRODUKSI - 16027304
Date Issued : 12/30/xx
FEB
21
473,681
473,681
594,753
28,322
594,753
MAR
22
381,942
381,942
381,942
17,361
381,942
APR
21
624,000
426,835
624,000
29,714
624,000
MAY
23
660,000
328,720
660,000
28,696
660,000
…
…
…
…
…
…
…
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Production Plan
(Make To Stock)
PRODUCTION PLAN
Product Family : Valves
Unit of Measure : Each
MONTH
WORKING DAYS
Forecast
Production Plan
Planned Daily Rate
Shipping Forecast
Planned Ending Inventory
Date Issued : 6/1/xx
JUNE
PAST DUE
21
2,460
2,603
124
2,460
1,240
1,383
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JULY
22
2,500
2,726
124
2,500
1,611
AUG
23
2,700
2,852
124
2,700
1,763
SEPT
20
3,000
2,480
124
3,000
1,243
OCT
23
2,500
2,500
109
2,500
1,243
…
…
…
…
…
…
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Strategi Aggregate Planning
1.
Capacity options

Mengubah-ubah tingkat inventory (level inventory)

Mengubah-ubah ukuran tenaga kerja: hiring / lay off (chase
strategy)

Mengubah-ubah production rate: over time / under time

Menggunakan part time workers
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Strategi Aggregate Planning
2.
Demand options

Mempengaruhi demand  advertising (periklanan), promosi, personal
selling, discount, diskriminasi harga

Backordering
3.
Pure strategies

Bila yang diubah-ubah hanya satu variabel
4.
Mixed Options

Melibatkan pengubahan beberapa variabel, misalnya bila pure strategy
tidak feasible
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Fase-fase Aggregate Planning
Phase 2
Phase 3
Smooth out capacity
utilization
Determine feasible
production alternative
Periodically
Phase 1
Phase 4
Regularly
Forecast aggregate
demand
Allocate demand to
production periods
Time series with
seasonals
Complementary
products
Moving averages
Pricing
Fixed work force
- Overtime
- Undertime
Linear costs
Trial and Error
Exponential
smoothing
Promotion
Others
Flexibility delivery
times
Variable work force
- Hiring
- Layoffs
Linear Programming
- Transportation
- Simplex
Inventory
Nonlinear Costs
Backordering
Linear decision rule
Subcontracting
MANAJEMEN OPERASIONAL PRODUKSI - 16027304
Others
Heuristic and search models
(suitable for all type of costs)
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Fase-fase Aggregate Planning

Phase I : Preparation of an Aggregate Demand Forecast


Forecast dalam satuan unit yang sama untuk semua jenis item produk
Phase II : Specification of Organization Policies for Smoothing Capacity
Utilization

Membuat policy untuk merealisasikan perencanaan agregat yang telah
diramalkan sebelumnya untuk mengantisipasi unstationary demand
dengan melibatkan marketing dan produksi

Contoh: diskon, promosi, dll
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Fase-fase Aggregate Planning

Phase III : Determination of Feasible Production Alternatives

Changing the production rate with the same work force

Changing production rate by changing the size of work force

Absorbing demand through inventories

Absorbing demand by backordering

Absorbing demand by subcontracting
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Fase-fase Aggregate Planning

Phase IV : Determination of Optional Production Strategy

Menentukan strategi yang optimal dengan alokasi demand forecast dengan
alternatif-alternatif produksi yang meminimumkan biaya total selama
horizon perencanaan
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Aggregate Plan – Managerial Inputs
Distribution and marketing
Customer needs
Demand forecasts
Competition behavior
Operations
Current machine capacities
Plans for future capacities
Workforce capacities
Current staffing level
Materials
Supplier capabilities
Storage capacity
Materials availability
Aggregate
plan
Engineering
New products
Product design changes
Machine standards
MANAJEMEN OPERASIONAL PRODUKSI - 16027304
Human resources
Labor-market conditions
Training capacity
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Aggregate Plan – Outputs
Aggressive Alternatives
Complementary
Products
Competitive
Pricing
Reactive Alternatives
Size of
Workforce and
Workforce Adjustment
Inventory
Levels
MANAJEMEN OPERASIONAL PRODUKSI - 16027304
Aggregate
plan
Production
per month
(in units or $)
Units or dollars
of Backlogs,
backorders, or
stockout
Units or
dollars
subcontracted
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Controllable (Decision) Variable
 Inventory
 Production rate
 Manpower
 Capacity : overtime / recruitment / layoff (tenaga kerja /
workforce)
 Subcontract
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Relevant Cost
 Hiring/layoff cost
 Overtime/undertime cost
 Inventory carrying cost
 Subcontracting incremental cost
 Part time labor cost
 Backorder cost
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Aggregate Planing Objectives
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Total Cost
Production cost Cost of regular Cost of units overtime


in period t
production
production
Cost of unit used
Cost of
Cost of



from inventory
backordering
hiring
Cost of
Cost of


firing
subcontracting
TC  C1  C2   Ct
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Total Cost
Demand
forecast
Allocation
amount, units
Unit
costs
Total
costs
$12
$960
Subcontracting
80
Inventory
200*
$1
$400
120
$8
$960
300
$5
$1,500
D5=700
Internal capacity
Production
alternative
Overtime
production
Regular
production
Total Cost at period 5
4
5
$3,820
6
* The 200 units form inventory were produce in period 3
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Methods





Trial and Error (Charting/Graphical Methods)

Pure strategy

Mixed strategy
Mathematical (Optimal) Approach

Linear Programming Model

Transportation Model
Empirical Approach
Simulation
Berdasarkan asumsi hubungan biaya yang digunakan, metode aggregate planning
dapat dibedakan menjadi:
1. Linear cost relationships (Metode LDR)
2. Non-linear cost relationships (Metode Bowman)
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Klasifikasi Metode Aggregate Planning
Aggregate
planning
method
Cost relationships
Linear
Nonlinear
Not yielding
optimal plan
A. Trial and error:
▪ Using table
▪ Using graph
Yielding optimal
plan
B. Linear programming D. Linear decision rule
▪ Transportation
Dynamic programming
method
▪ Simplex method
MANAJEMEN OPERASIONAL PRODUKSI - 16027304
C. Heuristic models and
Computer search
models
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Sistem Aggregate Planning
Constraints
Decision
Capacity limits for
production alternatives
Allocate demand
to production
periods using
feasible
alternatives
Input
Output
Period-by-period
demand forecasts
Feasible production
alternatives
Production rate
Aggregate
Planning
Work-force size
Cost data on item 2
Desired inventory
Initial condition
Amount of
subcontracting
Performance criteria
MANAJEMEN OPERASIONAL PRODUKSI - 16027304
(Minimize total production cost)
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Trial and Error

Contoh :

Diketahui demand selama 8 kuartal ke depan (hasil ramalan)

Ongkos kenaikan tingkat produksi
: $ 100

Ongkos penurunan tingkat produksi
: $ 150

Ongkos inventory
: $ 50

Incremental cost for subcontracting : $ 80
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Trial and Error
Forecast demand per Kuartal
Demand Kumulatif
220
220
170
390
400
790
600
1390
380
1770
200
1970
130
2100
300
2400
MANAJEMEN OPERASIONAL PRODUKSI - 16027304
Demand per kuartal
Kuantitas demand
Kuartal
1
2
3
4
5
6
7
8
800
600
400
200
0
1
2
3
4
5
6
7
8
Kuartal
28
Trial and Error
Level Strategy (2)
Units
Business Cycle
Production
1
2
3
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5
6 7
8 9 10 11
Time Periods
12 13
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Trial and Error
Level Strategy (1)
Kuartal
Demand
1
2
3
4
5
6
7
8
220
170
400
600
380
200
130
300
*) Initial
Production
Level
300
300
300
300
300
300
300
300
Inventory
80
210
110
-190
-270
-170
0
0
Adjusted Ongkos
Inventory*) inventory
17.500
350
24.000
480
19.000
380
4.000
80
0
0
5.000
100
13.500
270
13.500
270
96.500
Total
inventory: 270
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Trial and Error
Chase Strategy (3)
Units
Business Cycle
Production
1
2
3
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5
6 7
8 9 10 11
Time Periods
12 13
31
Trial and Error
Chase Strategy (3)
Kuartal Demand
1
220
2
170
3
400
4
600
5
380
6
200
7
130
8
300
MANAJEMEN OPERASIONAL PRODUKSI - 16027304
Hiring
0
0
23.000
20.000
0
0
0
17.000
Layoff
0
7.500
0
0
33.000
27.000
10.500
0
Total
Total
0
7.500
23.000
20.000
33.000
27.000
10.500
17.000
138.000
32
Trial and Error
Subcontract Strategy
Kuartal Demand
1
2
3
4
5
6
7
8
220
170
400
600
380
200
130
300
MANAJEMEN OPERASIONAL PRODUKSI - 16027304
Production
Incremental
Subcontract
level
cost
130
90
7,200
130
40
3,200
130
270
21,600
130
470
37,600
130
250
20,000
130
70
5,600
130
0
0
130
170
13,600
Total
108,800
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Aggregate Planning
Strategy - Hybrid
Units
Business Cycle
Production
rate break
1
2
3
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4
5
6 7 8 9 10 11 12 13
Time Periods
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AGGREGATE PLANNING STRATEGIES
Chase Strategy – using capacity as the
lever
Time flexibility from workforce or
capacity strategy – using utilization as
the lever
Level Strategy – using inventory as the
lever
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CHASE STRATEGY
▪ The production rate is synchronized with the demand rate by varying machine capacity or
hiring and lying off employees as the demand rate varies.
▪ This strategy can be expensive to implement if the cost of varying machine or labor capacity
over time is high.
▪ The Chase Strategy results in low levels of inventory in the supply chain and high levels of
change in capacity and workforce.
▪ It should be used when the cost of carrying inventory is very high and costs to change
levels of machine and labor capacity are low.
Chase Strategy  Merubah Kapasitas
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Time Flexibility from Workforce or
Capacity Strategy
▪ This strategy may be used if there is excees machine capacity. For example, machine are not
used 24 hours a day, 7 days a week.
▪ In this case, the workforce (capacity) is kept stable but the number of hours worked is varied
over time in an effort to synchronize produck with demand.
▪ This strategy result in low levels of inventory but with lower average machine capacity is
relatively inexpensive.
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LEVEL STRATEGY
▪ A stable machine capacity and workforce are maintained with a constant output rate.
▪ Shortages and surpluses result in inventory levels fluctuating over time.
▪ In this case, production is not synchronized with demand.
▪ Employees benefit from stable working conditions.
▪ A drawback associated with this strategy is that large inventories may accumulate and customer
orders may be delayed.
▪ This strategy keeps capacity and costs of changing capacity relatively low.
▪ It should be used when inventory carrying and backlog costs are relatively low.
Level Strategy  Kapasitas Tetap, Produksi Konstan
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MAIN OBJECTIVE
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MAIN OBJECTIVE
a.
Production Rate
: jumlah unit yang dapat diselesaikan setiap unit waktu
tertentu. (misal, setiap minggu atau setiap bulan).
b.
Workforce
: jumlah dari pekerja setiap unit dari kapasitas yang
dibutuhkan untuk melakukan produksi.
c.
Overtime
: jumlah dari waktu lembur perencanaan produksi.
d.
Machine Capacity Level
untuk produksi.
: jumlah unit dari kapasitas mesin yang dibutuhkan
e.
Subcontracting
: kebutuhan kapasitas yang disubkontrakkan pada satu
perencanaan waktu tertentu.
f.
Backlog
: permintaan yang tidak dipenuhi, yang muncul pada
periode tertentu tetapi akan dipenuhi pada periode yang akan datang.
g.
Backorder
: permintaan yang tidak terpenuhi, tetapi pelanggan
masih mau menunggu untuk memproduksi barang tersebut.
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MAIN OBJECTIVE
h.
Safety Stock
: jumlah produk yang diproduksi pada satu periode tertentu
dan digunakan ketika jumlah permintaan lebih besar dari jumlah unit produksi.
i.
Inventory
: persediaan (stok) dari suatu item atau sumber daya yang
digunakan dalam suatu perusahan.
j.
Inventory on Hand : jumlah persediaan yang tidak digunakan dari periode
sebelumnya.
k.
Shortage / Stock out : jumlah demand > jumlah supply.
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LEARNING OBJECTIVES
1. Identify the decisions that are best solved by aggregate
planning. (capacity, production, and inventory)
2. Understand the importance of aggregate planning as a
supply chain activity. (customers and supplier)
3. Describe the information needed to produce an
aggregate plan. (cost and production information)
4. Explain the basic trade-offs to consider when creating an
aggregate plan. (cost of capacity, inventory, stockout)
5. Formulate and solve aggregate planning problems using
Microsoft Excel.
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ADA PERTANYAAN ?
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