Ppt discussing aggregate planning included optimization model solution.

1. Dr. AKHMAD YUNANI, S.E., M,T,
ADMINSTRASI BISNIS – FAKULTAS
KOMUNIKASI DAN BISNIS
KBJ3D3 – RANTAI PASOK DALAM BISNIS
SEMESTER 7 – 2022/2023
05. AGGREGATE PLANNING IN A
SUPPLY CHAIN

2. TUJUAN PEMBELAJARAN
Mengidentifikasi keputusan terkait aggregate planning (AP)
Menjelaskan pentingnya AP dalam RP
Menjelaskan informasi yang diperlukan untuk menyusun
AP
Menjelaskan trade-off yang muncul ketika menyusun AP
Menyusun AP dengan Microsoft Excel
Setelah mengikuti sesi ini, mahasiswa dapat:
1
2
3
5
Buku rujukan utama: Chopra ddk “Supply Chain Management” Ch. 8
4

3. OVERVIEW ON ENTERPRISE
ERP dan planning
Strategic Planning
Business Planning
Volume
S & O Plan
Sales Plan Operations
Plan
Mix
Master Scheduling
Detailed Planning &
Execution Process; MRP,
Plan Sched., Supply Sched.,
etc/
Execution
Demand
Supply
Forecasting
&
demand
management
Capacity
planning

4. PERAN AP DALAM RP
Konsep dasar
Penentuan jumlah dan waktu produksi untuk
waktu segera di masa yg akan datang
Tujuan  minimize biaya (dan
maximize profit) dalam periode
perencanaan melalui
penyesuaian:
Prasyarat untuk AP:

5. PERAN AP DALAM RP
Konsep dasar
Contoh

6. PERAN AP DALAM RP
Konsep dasar
Contoh
Product
Decision
Process
planning
& capacity
decision
Master
Prod.
Schedule
& MRP
Detailed
work
schedule

7. PERAN AP DALAM RP
Konsep dasar
 Dengan demand forecast dalam suatu rentang waktu,
tentukan tingkat produksi, inventory, dan kapasitas setiap
periode dalam rentang tersebut sehingga tercapai profit
maksimal
 Tetapkan rentang waktu perencanaan (umumnya 3-18
bulan)
 Tetapkan durasi setiap periode
 Tetapkan informasi kunci yang dibutuhkan untuk
menyusun sebuah aggregate plan

8. PERAN AP DALAM RP
Konsep dasar
Level inventory
Jumlah tenaga kerja
Penggunaan tenaga kerja
part-timer, lembur, waktu
menganggur.
Subkontrak
Strategi harga
• Kekurangan stok
berdampak
hilangnya
customer. 
service level
• Biaya persediaan
naik.
• Biaya hiring dan
training.
• Karyawan baru
kurang produktif.
• PHK berdampak
moral.
• Solusi memenuhi
demand melonjak.
• Risiko hi-cost.
• Risiko kualitas.
• Risiko rahasia bisnis
terbuka
• Menaikkan demand:
promosi.
• Memanjangkan
demand: back-
order, counter-
seasonal, mix
service.
• Sulit memenuhi
kenaikan demand yg
tinggi.
• Lembur
meningkatkan cost
dan menurunkan
produktivitas.
• Sulit memanfaatkan
waktu nganggur.
• Hanya cocok untuk
pekerjaan rendah
ketrampilan

9. INFORMASI DIBUTUHKAN UNTUK AP
 Aggregate demand forecast Ft untuk setiap periode t
selama kurun waktu T
 Biaya produksi
 Labor costs, regular time ($/hr) dan overtime ($/hr)
 Subcontracting costs ($/hr atau $/unit)
 Cost of changing capacity – hiring atau layoff ($/tenaga kerja),
penambahan atau pengurangan kapasitas mesin ($/mesin)
 Jam kerja orang/mesin yang dibutuhkan per unit
 Inventory holding cost ($/unit/periode)
 Stock-out atau backlog cost ($/unit/period)  rush order
 Constraints – overtime, layoffs, capital available,
stockouts, backlogs, dari suppliers

10. OUTPUT AP
 Kuantitas produksi dengan waktu regular, lembur, dan
subkontrak
 Jumlah persediaan
 Jumlah backlog/stock-out
 Peningkatan/penurunan kapasitas mesin
A poor aggregate plan can result in lost sales, lost profits,
excess inventory, or excess capacity (explain and give an
example)

11. IDENTIFIKASI UNIT PRODUKSI
AGREGAT
 Aggregate diidentifikasi sebagai suatu cara untuk
menepati jadwal produksi
 Fokus pada bottlenecks yang mungkin timbul ketika
memilih unit agregat dan menentukan kapasitas serta
waktu produksi
 Perlu perhatian serius terhadap aktivitas seperti setups
dan maintenance

12. IDENTIFIKASI UNIT PRODUKSI
AGREGAT
 Contoh
 AB42 adalah manufacturer peralatan pertanian yang
memiliki enam product families. Biaya, revenue, waktu
produksi, waktu setup dan data historis ukuran batch
untuk setiap product family sebagai berikut:
Family
Material
Cost/
Unit ($)
Revenue/
Unit ($)
Setup
Time/B
atch
(hour)
Average
Batch
Size
Production
Time/ Unit
(hour)
Net
Production
Time/Unit
(hour)
Percentage
Share of
Units Sold
A 15 54 8 50 5.60 5,6 + 0,16 =
5,76
10
B 7 30 6 150 3.00 25
C 9 39 8 100 3.80 20
D 12 49 10 50 4.80 10
E 9 36 6 100 3.60 20
F 13 48 5 75 4.30 15

13. IDENTIFIKASI UNIT PRODUKSI
AGREGAT
 Weighted average approach –AB42
• Weighted average approach
Family
Material
Cost/ Unit ($)
Revenue/
Unit ($)
S
etup Time/
Batch (hour)
Average
Batch S
ize
Production Time/
Unit (hour)
Net Production
Time/Unit (hour)
Percentage S
hare
of Units S
old
Weighted Average
-material cost
Revenue per
Aggregate Unit
Net Prod. Time
per Aggregate Unit
A 15 54 8 50 5,6 5,76 10 1,5 5,4 0,58
B 7 30 6 150 3 3,04 25 1,75 7,5 0,76
C 9 39 8 100 3,8 3,88 20 1,8 7,8 0,78
D 12 49 10 50 4,8 5 10 1,2 4,9 0,50
E 9 36 6 100 3,6 3,66 20 1,8 7,2 0,73
F 13 48 5 75 4,3 4,37 15 1,95 7,2 0,66
256 10 40 4,00

14. STRATEGI PERENCANAAN AGREGAT
Srategi
Aggregate Plan
Chase
strategy
Level
strategy
Mix
strategy
 Tingkat output setiap
periode disesuaikan
dengan demand (forecast).
 Jumlah karyawan bervariasi
mengikuti tingkat output.
 Sesuai untuk bisnis service.
• Tingkat produksi
harian seragam.
• Menggunakan
inventory atau waktu
menganggur sebagai
buffer.
• Tingkat produksi yg
stabil bagus untuk
kualitas dan
produktivitas.
• Kombinasi bisa
menjadi alternatif
optimal.

15. PERENCANAAN AGREGAT DENGAN
LINEAR PROGRAMMING
 Case: AB42 Mfg
Month Demand Forecast
January 1.600
Februar
y
3.000
March 3.200
April 3.800
May 2.200
June 2.200
• There is no limits on subcontracting, inventories and stock-out/backlog
• All stock-outs are backlogged/supplied from the following month
production
• Inventory cost are incurred on the ending inventory of the month
• The supply chain manager’s goal is to obtain the optimal aggregate plan
that allows AB42 to end June with at least 500 units (no stock-out in the
end of June and at least 500 units in inventory)
Beginning inventory 1.00
0
No. of workers in January 80
Total working days a month 20
Labor cost per hour regular
time
$4
Hour time per day regular 8
Maximum overtime (hour) per
employee per month
10

16. PERENCANAAN AGREGAT DENGAN
LINEAR PROGRAMMING
 Case: AB42 Mfg
Item Cost
Material cost $10/unit
Inventory holding cost $2/unit/month
Marginal cost of stock-out/backlog $5/unit/month
Hiring and training costs $300/worker
Layoff cost $500/worker
Labor hours required 4/unit
Regular time cost $4/hour
Overtime cost $6/hour
Cost of subcontracting $30/unit

17. PERENCANAAN AGREGAT DENGAN
LINEAR PROGRAMMING
 Case: AB42 Mfg
 Decision variables:
For t = 1, ..., 6
Wt = Workforce size for month t
Ht = Number of employees hired at the beginning of month
t
Lt = Number of employees laid off at the beginning of
month t
Pt = Production in month t
It = Inventory at the end of month t
St = Number of units stocked out at the end of month t
Ct = Number of units subcontracted for month t
Ot = Number of overtime hours worked in month t

18. PERENCANAAN AGREGAT DENGAN
LINEAR PROGRAMMING
 Case: AB42 Mfg
 Objective function
• Minimize
(Regular-time labor cost + Overtime labor cost + Cost of
hiring and layoffs + Cost of holding inventory + Cost of
stocking out + Material cost + Cost of subcontracting)
Min 640Wt
t=1
6
å + 6Ot
t=1
6
å + 300Ht
t=1
6
å + 500Lt
t=1
6
å
+ 2It
t=1
6
å + 5St
t=1
6
å + 10Pt
t=1
6
å + 30Ct
t=1
6
å
$4 per hour X 8 hours
a day X 20 days a
month
$6 per
hour
$300 per worker
$500 per worker
$2 per unit per month
$5 per unit per month
$30 per
unit
$10 per
unit

19. PERENCANAAN AGREGAT DENGAN
LINEAR PROGRAMMING
 Case: AB42 Mfg
 All for constraints t = 1,..., 6
1. Workforce, hiring, and layoff constraints
Wt
=W t–1
+Ht
– Lt
2. Capacity constraints
Pt
£ 40Wt
+
Ot
4
3. Inventory balance constraints
It–1
+ Pt
+Ct
= Dt
+ St–1
+ It
– St
4. Overtime limit constraints
Ot
£10Wt
 W0 = 80
4 hour per unit, 8
hours a day, 20 days a
month
4 hour per
unit
I0 =
1.000
I6 ≥ 500
S6 = 0
Maximum
overtime

20. PERENCANAAN AGREGAT DENGAN
LINEAR PROGRAMMING
 Case: AB42 Mfg
 
T
I
I
I
T
t t
T 



1
–
1
0 2
/
)
(
inventory
Average
=
(I0
+ IT
) / 2+ It
t=1
T –1
å
( )
T
é
ë
ê
ê
ê
ù
û
ú
ú
ú
Dt
t=1
T –1
å
( )
T
é
ë
ê
ê
ê
ù
û
ú
ú
ú
Average time
in inventory

21. PERENCANAAN AGREGAT DENGAN
LINEAR PROGRAMMING
 Case: AB42 Mfg
Total cost over planning horizon = $422,275
Revenue over planning horizon = 40 x 16,000 = $640,000
Period,
t
No.
Hired,
Ht
No.
Laid
Off,
Lt
Workforce
Size, Wt
Overtime,
Ot
Inventory,
It
Stockout,
St
Subcontract,
Ct
Total
Production,
Pt
0 0 0 80 0 1,000 0 0
1 0 15 65 0 1,983 0 0 2,583
2 0 0 65 0 1,567 0 0 2,583
3 0 0 65 0 950 0 0 2,583
4 0 0 65 0 0 267 0 2,583
5 0 0 65 0 117 0 0 2,583
6 0 0 65 0 500 0 0 2,583

22. PERENCANAAN AGREGAT DENGAN
LINEAR PROGRAMMING
 Case: AB42 Mfg
=
(I0
+ I6
) / 2+ It
t=1
5
å
( )
T
=
5,367
6
= 895
Average
seasonal
inventory
Average flow time =
895
2,667
= 0.34 = 0.34 months

23. HIGHER DEMAND VARIABILITY
 Case: AB42 Mfg
Month Demand Forecast
January 1,000
February 3,000
March 3,800
April 4,800
May 2,000
June 1,400
=
(I0
+ IT
) / 2+ It
t=1
T –1
å
( )
T
=
6,450
6
=1,075
Average
seasonal
inventory

24. HIGHER DEMAND VARIABILITY
 Case: AB42 Mfg
Total cost over planning horizon = $432,858
Period,
t
No.
Hired,
Ht
No.
Laid
Off,
Lt
Workforce
Size, Wt
Overtime,
Ot
Inventory,
It
Stockout,
St
Subcontract,
Ct
Total
Production,
Pt
0 0 0 80 0 1,000 0 0
1 0 15 65 0 2,583 0 0 2,583
2 0 0 65 0 2,167 0 0 2,583
3 0 0 65 0 950 0 0 2,583
4 0 0 65 0 0 1,267 0 2,583
5 0 0 65 0 0 683 0 2,583
6 0 0 65 0 500 0 0 2,583
Average flow time =
1,075
2,667
= 0.40 months

25. HIGHER DEMAND VARIABILITY
 Case: AB42 Mfg
 Lower hiring and layoff costs
=
(I0
+ IT
) / 2+ It
t=1
T –1
å
( )
T
=
2,500
6
= 417
Average
seasonal
inventory
Average flow time =
417
2,667
= 0.16 months
Total cost over planning horizon = $412,688

26. HIGHER DEMAND VARIABILITY
 Case: AB42 Mfg
Period,
t
No.
Hired,
Ht
No.
Laid
Off,
Lt
Workforce
Size, Wt
Overtime,
Ot
Inventory,
It
Stockout,
St
Subcontract,
Ct
Total
Production,
Pt
0 0 0 80 0 1,000 0 0
1 0 35 45 0 1,200 0 0 2,267
2 0 0 45 0 0 0 0 2,267
3 42 0 87 0 300 0 0 2,267
4 0 0 87 0 0 1,267 0 2,267
5 0 26 61 0 250 683 0 2,267
6 0 0 61 0 500 0 0 2,267

27. FORECAST ERROR DALAM AP
Forecast errors must be considered
Safety inventory
Safety capacity
 Use overtime as a form of safety capacity
 Carry extra workforce permanently as a form of safety
capacity
 Use subcontractors as a form of safety capacity
 Build and carry extra inventories as a form of safety
inventory
 Purchase capacity or product from an open or spot
market as a form of safety capacity

28. Aggregate Planning In Excel
For t = 1, ..., 6
Wt = Workforce size for Month t
Ht = Number of employees hired at the beginning of
Month t
Lt = Number of employees laid off at the beginning
of Month t
Pt = Production in Month t
It = Inventory at the end of Month t
St = Number of units stocked out at the end of
Month t
Ct = Number of units subcontracted for Month t
Ot = Number of overtime hours worked in Month t

29. Aggregate Planning In Excel
Figure 8-1

30. Aggregate Planning In Excel
Figure 8-2

31. Aggregate Planning In Excel
Figure 8-3

32. Aggregate Planning In Excel
Figure 8-4

33. Building a Rough Master
Production Schedule
Disaggregate an aggregate plan
Family
Setup
Time/B
atch
(hour)
Average
Batch
Size
Production
Time/Unit
(hour)
Production
Quantity
Number
of
Setups
Setup
Time
(hours)
Production
Time
(hours)
A 8 50 5.60 258 5 40 1,445
B 6 150 3.00 646 4 24 1,938
C 8 100 3.80 517 5 40 1,965
D 10 50 4.80 258 5 50 1,238
E 6 100 3.60 517 5 30 1,861
F 5 75 4.30 387 5 25 1,664
Table 8-8

34. The Role of IT in
Aggregate Planning
The ability to handle large problems
The ability to handle complex problems (through
either nonlinear optimization or linear
approximations)
The ability to interact with other core IT systems
such as inventory management and sourcing

35. Implementing Aggregate Planning
in Practice
1. Think beyond the enterprise to the entire
supply chain
2. Make plans flexible because forecasts are
always inaccurate
3. Rerun the aggregate plan as new data
emerge
4. Use aggregate planning as capacity utilization
increases

36. Summary of Learning Objectives
1. Identify the decisions that are best solved by
aggregate planning
2. Understand the importance of aggregate
planning as a supply chain activity
3. Describe the information needed to produce
an aggregate plan
4. Explain the basic trade-offs to consider when
creating an aggregate plan
5. Formulate and solve aggregate planning
problems using Microsoft Excel