Transcript Aggregate Planning

Aggregate Planning
Aggregate planning is intermediate range
capacity planning usually 2-12 months out
Short
Intermediate
Long
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Aggregation
• Product families lumped together
• Inputs to the plan
– Forecast, Resources, Policies, Inventory, Costs
• Outputs – Cost, Levels of inventory, output,
utilization
• Plans roll
2
a)
b)
Brooke Cashion, operations manager at Kansas furniture, has received the
following estimates of demand requirements. Assuming stockout costs for
lost sales of $100, inventory carrying costs of $25/unit/month, and zero
ending inventory, evaluate these two plans on an incremental basis.
Produce at a steady rate (equal to minimum requirements) of 1,000 per
month and subcontract additional units at a $60 per unit premium cost.
Vary the workforce, which performs at a current production level of 1,300
units/month. The cost of hiring additional workers is $3,000/100 units
produced. The cost of layoffs is $6,000/100 units cut back.
July
Aug
Sept
Oct.
Nov.
Dec.
1,000
1,200
1,400
1,800
1,800
1,600
3
Master Scheduling
Master Production Schedule (MPS) is a
“disaggregation” of the aggregate plan showing
quantity and timing of end items.
Feasibility checked by the rough cut capacity plan
Inputs: beginning inventory, forecast, orders
Outputs: available-to-promise (ATP) inventory,
production requirements
(we’re skipping ahead to pp. 522 – 524)
4
MPS Worksheet
Week
1
2
3
4
5
Forecast
Customer orders
(committed)
Projected
on-hand
inventory
MPS
ATP
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Projected On-hand Inventory
• Calculate projected on-hand inventory one
week at a time
Projected on-hand =
Inventory
Inventory from
previous week
–
Current week’s
requirements
• The current week’s requirements is the larger
of forecast and customer orders.
• When projected on-hand inventory is
negative, then production must occur.
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Available to Promise (ATP) Inventory
• ATP = uncommitted inventory (not already
promised to another customer )
• First week ATP
Beginning inventory + MPS – look ahead quantity
• All other weeks’ ATP
MPS quantity – look ahead quantity
Look ahead quantity is the sum of booked orders until an MPS amount
occurs. (Count the customer orders for the current period, plus the next
period, and so on. Stop counting when you come to a period where an
MPS quantity exists.)
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MPS Example
Week
1
2
3
4
5
Forecast
40
45
45
50
60
Customer orders
(committed)
43
25
5
0
0
7
32
22
7
17
70
35
35
70
45
30
35
70
Projected
on-hand
inventory
MPS
ATP
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Beginning inventory for period 1 = 50 units, lot size is 35.
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MPS Problem
Week
1
2
3
4
5
Forecast
50
55
45
40
40
Customer orders
(committed)
45
30
20
15
10
Projected
on-hand
inventory
MPS
ATP
Beginning inventory for period 1 = 30 units, lot size is 80.
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Material Requirements Planning
• Dependent & Independent demand
• Answers
– what items?
– how many?
– When?
• MRP Inputs
– Bill of materials (BOM)
– Master schedule
– Inventory records
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Bill of Materials
Product structure Tree
Level
X
0
B(2)
D(3)
C
E
E(2)
1
F(2)
2
11
How many more of each component is needed to make
15 Xs if there are 5 of each already in stock?
X
B(2)
D(3)
C
E
E(2)
F(2)
12
If 20 units of the end items are to be assembled, how many additional
units of E are needed?
Item
End
B
C
D
E
F
G
H
LT
1
2
3
3
1
2
1
2
Amt
0
10
10
25
12
30
5
0
End
C
B(2)
F(3)
E(2)
G(2)
D(3)
E(2)
H(4)
E(2)
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An order for the end item should be shipped at week 11.
latest the order can be started & still arrive on time?
Item
End
B
C
D
E
F
LT
1
2
3
3
1
2
Amt
0
10
10
25
12
30
What is the
G
1
5
H
2
0
End
C
B(2)
F(3)
E(2)
G(2)
D(3)
E(2)
H(4)
E(2)
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MRP Processing
All #s are for the beginning of a period
•
•
•
•
•
•
Gross requirements - total demand
Scheduled receipts - open orders from vendors
Projected on hand - inventory at start of period
Net requirements - amt needed in each period
Planned-order receipts - qty to be received
Planned-order releases - amt to order ea. period
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a)
b)
c)
Electro Fans has just received an order for one thousand 20 inch fans due week 7. Each
fan consists of a housing assembly, two grills, a fan assembly, and a switch. The housing
assembly consists of a frame, two supports, and a handle. The fan assembly consists of
a hub and five blades. The electrical unit consists of a motor, a switch, and a knob. With
the lead times, on-hand inventory, and scheduled receipts shown construct;
a product structure tree
a time-phased product structure
a net materials plan
Component
20” Fan
Housing
LT
On Hand
1
100
1
100
Frame
2
Supports (2)
1
50
Handle
1
400
Grills (2)
2
200
Fan Assembly
3
150
Hub
1
Blades (5)
2
Electrical Unit
1
Motor
1
Switch
1
Knob
1
Lot Size
Sch. Recpt.
100
20
12
25
200 wk. 2
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