Transcript Document

MS 401
Production and Service Systems Operations
Spring 2009-2010
Capacity Planning
Slide Set #12
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Capacity Planning
• The two major activities of MPC
– planning / control of materials
– planning / control of capacity
• Capacity plans must be developed concurrently with
materials plans if the materials plans are to be realized
• Trade-off
– insufficient capacity versus excess capacity
• Chapter 10 in VBWJ
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Capacity Planning Hierarchy in MPC
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Capacity Planning Hierarchy in MPC
• Resource planning
– converting monthly, quarterly or annual data from the APP into
aggregate resources such as gross labor hours, floor space and
machine hours
– the level of planning involves new capital expansion, bricks and
mortar (buildings), machine tools, warehouse space etc.
• Rough-cut capacity planning
– to modify the resource levels or material plan to ensure the
execution of the MPS
– three techniques
• capacity planning using overall planning factors (CPOF)
• capacity bills
• resource profiles
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Capacity Planning Hierarchy in MPC
• Capacity Requirements Planning (CRP)
– time-phased capacity requirements determined from MRP data
• Finite loading
– shop scheduling process
• Input / Output analysis
– method for monitoring the actual consumption of capacity during
the execution of detailed material planning
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Capacity Planning and Control Techniques
• Capacity planning using overall factors (CPOF)
• Capacity bills
MPS
• Resource profiles
• Capacity Requirements Planning (CRP)
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MRP
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Capacity Planning Using Overall Factors (CPOF)
• Simple technique
• Allocates workload to work centers based on historical
data
• Assumes that product mixes and historical divisions of
work between work centers remain unchanged
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Capacity Planning Using Overall Factors (CPOF)
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Capacity Bills
• Takes into account the period-to-period shifts in product mix
– BOM and routing data required
• The Bill of capacity indicates the total standard time required
to produce one end product in each work center
• Sample product structures:
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Capacity Bills
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Capacity Bills
• The total hours for MPS in each period is the same as the hours in CPOF
• The difference is
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Resource Profiles
• Introduces the time dimension
• Leadtimes: Assume 2 week for component C, and 1 week for all other
end products and components
• Consider, as an example, the requirements for
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Resource Profiles
• and the requirements for end product B for period 5:
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Resource Profiles
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Resource Profiles
• The work center percentage allocations and the total hours (939.20) is the
same as the “capacity bill” method results
• However, the period requirements for individual work centers vary due
to
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Capacity Requirements Planning (CRP)
• Medium-term capacity planning utilizing time-phased
MRP data (including lot sizes and timing)
– improved accuracy in timing capacity requirements
• The other three methods use only MPS data
• Accounts for available inventories
– through MRP’s gross-to-net feature
• Recognizes the completed shop orders
– considers only the capacity needed to complete the remaining work
on open shop orders
• Takes into account the demand that may not be accounted
for in the MRP
– for example, demand for service parts
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Capacity Requirements Planning (CRP)
Item C is processed at work center 300 during the second week of the 2-week
leadtime
1+40*.175=8 hours
watch out for timing
•
•
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Capacity Monitoring with Input / Output Control
• Monitoring the execution of the plan
• Compare the planned work input and output with the
actual input and output
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Capacity Monitoring with Input / Output Control
• Backlog
– decouples input from output, allowing work center operations to be
less affected by variations in requirements
• Do not release orders to a work center that already has an
excessive backlog
• The bathtub analogy to input/output analysis (VBWJ, p355)
– backlog: the water in the tube
• Find the bottlenecks in the system, and concentrate on
managing their capacities efficiently
– an hour of capacity lost in a bottleneck work center is an hour lost
to the entire company
– an hour of capacity gained in a non-bottleneck work center will
only increase work in process inventory and confusion
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