Download - Dis Aggregation
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Disaggregation
Working with aggregate units facilitates intermediate planning.
But to put this plan into action we should translate it,
decompose it, disaggregate itand state it in terms of actual units
of products and for a shorter period
Aggregate planning was for12or more months.Now we should break it down into shorter periods, say 2-3 months.
Disaggregation:
Breaking down the aggregate plan into specific products - fromaggregate product to real specific products - based on the
specific products, then calculating detail of manpower,
material and inventory requirements.
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Disaggregation
Aggregate Plan
Month Jan Feb MarLawn Mower 200 300 400
Master Schedule
Push 100 100 100Self-propelled 75 150 200
Riding 25 50 100
Total 200 300 400Total of aggregate and
disaggregate products are not
necessarily equal
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Master Schedule
The result of disaggregationis a master schedule.
The Master Schedule shows quantity and timingof specific products.
It usually covers 6 to 12 weeks.
After preparing a tentative Master Schedule, a planner can do Rough-cut
Capacity Planning.
Rough-cut capacity planningis to check the feasibility of the Master
Schedule with respect to available manpowerand machinerycapacities,
storagespaces, and vendorcapabilities.
It is just a rough check to ensure that the master schedule is achievable.
The master schedule then is used as the basis for short term planning.
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Master Schedule
Aggregate plan: 12 months.
Master schedule: 12 weeks.
Master schedule is updated every 2 weeks.
Therefore, it is on a rolling basis, always we
have a disaggregated plan for the next 12weeks.
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Master Production Schedule (MPS)
Master schedulestates quantityand delivery timeof
specific products.
It says we need 75 push lawnmowers in January. But it does
not say how we get it - from production,or from inventory.
MasterProductionSchedule(MPS)is developed
based on Master Schedule.
MPS: Quantity and timing of planned production.
MPS determines the Promised Inventory, and the
Production Requirements availableto promise inventoryfor
each period.
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Master
scheduling
Beginning inventory
Forecast
Customer orders
Inputs Outputs
Projected inventory
Master production schedule
Uncommitted inventory
(Available to Promise)
Master Scheduling Process
The key idea is: we have a forecast, but it turns into and actualorder when we receive a customer order.
MPS starts with a preliminary calculation of projected inventory.
This reveals when we need production to get additional inventory.
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64 1 2 3 4 5 6 7 8
Forecast 30 30 30 30 40 40 40 40
Customer Orders
(committed) 33 20 10 4 2
Projected on-hand
inventory 31 1 -29
JUNE JULY
Beginning
Inventory
Customer orders are
larger than forecast in
week 1
Forecast is larger than
Customer orders in week 2
Forecast is larger than
Customer orders in week 3
Example; Projected on-hand Inventory
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Example; Projected on-hand Inventory
64 June July
1 2 3 4 5 6 7 8
Forecast 30 30 30 30 40 40 40 40
Customer Orders
(committed)33 20 10 4 2
Projected onhand inventory
31 1 41 11 41 1 31 61
MPS 70 70 70 70
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Available To Promise (ATP)
Now we can determine available to promiseat each period.
We use a look ahead procedure.
Sum booked customer orders week by week up to (not including)
the next week of production. This is booked orders.
The remaining inventory is ATP.
ATP is only calculated for the first week and for weeks in which
there is a MPS quantity. (In this example: weeks 1, 3, 5, 7, 8)
64 June July
1 2 3 4 5 6 7 8
Forecast 30 30 30 30 40 40 40 40
Customer Orders (committed) 33 20 10 4 2
Projected on hand inventory 31 1 41 11 41 1 31 61
MPS 70 70 70 70
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Available To Promise (ATP); First week
Available to promise in week 1 = Inventory in week 0 + Production
in week 1 - Customer Orders at week 1 - Customer Orders at week 2
ATP(1) = I(0)+ P(1) - CO(1) - CO(2)ATP(1) = 64+0 -33 -20= 11
This is an uncommitted inventory.
It can be assigned to week 1, week 2, or both.
64 June July
1 2 3 4 5 6 7 8
Forecast 30 30 30 30 40 40 40 40
Customer Orders (committed) 33 20 10 4 2
Projected on hand inventory 31 1 41 11 41 1 31 61
MPS 70 70 70 70
ATP 11 56 68 70 70
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Available To Promise (ATP); Other weeks
For other weeks, beginning inventory is removed from the formula:
ATP(3) = P(3)-CO(3)-CO(4)
ATP(3)= 70-10-4= 56
64 June July
1 2 3 4 5 6 7 8
Forecast 30 30 30 30 40 40 40 40
Customer Orders (committed) 33 20 10 4 2
Projected on hand inventory 31 1 41 11 41 1 31 61MPS 70 70 70 70
ATP 11 56 68 70 70
64 June July1 2 3 4 5 6 7 8
Forecast 30 30 30 30 40 40 40 40
Customer Orders (committed) 33 20 10 4 2
Projected on hand inventory 31 1 41 11 41 1 31 61
MPS 70 70 70 70
ATP 11 56 68 70 70
For weeks 7 and 8, no CO, therefore ATP = MPS
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Updating ATP
As additional orders are booked, they would be entered into the
schedule.
ATP would be updated to reflect new booked orders.
Marketing can use updated ATP amounts to provide realistic
delivery dates to customers
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Updating MPS
Changing to a master production schedule can be disruptive.
Particularly changes in the immediate periods of the schedule
Aggregate Plan is developed for say 1 year
Master Production Schedule is developed for a period of say 12
weeks.
MPS is updated say every 2 weeks, it is on a rolling basis.
Frozen Firm Full Open
1 2 3 4 5 6 7 8 9 10 11 12
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Problem 1. Book Page 627.
Forecast of demand for the next four months is 70 units permonth
Committed customer orders for the next four months are 80,50, 30, and 10, respectively. Order size is 100 units.Beginning inventory is 0.
Prepare MPS
Prepare ATP
Assignment
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Solution to Problem 1
1 2 3 4Forecast 70 70 70 70
Customer Orders 80 50 30 10
Inventory on hand 20
MPS 100
ATP
Month
1 2 3 4
Forecast 70 70 70 70
Customer Orders 80 50 30 10
Inventory on hand 20 50MPS 100 100
ATP
Month
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Solution to Problem 1
1 2 3 4
Forecast 70 70 70 70
Customer Orders 80 50 30 10
Inventory on hand 20 50 80
MPS 100 100 100
ATP
Month
1 2 3 4
Forecast 70 70 70 70
Customer Orders 80 50 30 10Inventory on hand 20 50 80 10
MPS 100 100 100
ATP
Month
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Solution to Problem 1
1 2 3 4
Forecast 70 70 70 70Customer Orders 80 50 30 10
Inventory on hand 20 50 80 10
MPS 100 100 100ATP 20
Month
1 2 3 4
Forecast 70 70 70 70
Customer Orders 80 50 30 10
Inventory on hand 20 50 80 10
MPS 100 100 100
ATP 20 50
Month
1 2 3 4
Forecast 70 70 70 70
Customer Orders 80 50 30 10
Inventory on hand 20 50 80 10
MPS 100 100 100ATP 20 50 60
Month