Capacity Mechanics


Detailed required to produce effective load and priority plans; includes level of safety capacity.

Capacity planning outputs to formulate:

· Capacity plans

· Tooling requirements

· Overload conditions

· Underload conditions

Methods that balance capacity and load

· Rescheduling order

· Splitting orders

· Changing capacity – workforce changes/subcontracting

· Modifying order quantities/priorities

Close loop with master planning of resources and distribution planning

· Product quantities

· Timing

· Priorities

Close loop within detailed scheduling and planning process

· Purchased

· Self-manufactured materials

· Part quantities

· Timing

· Priorities

Close loop with execution and control of operations…verify that all these made correctly, on time:

· Manufactured parts

· Subassemblies

· Assemblies

Priority/Capacity Hierarchy

· CRP cannot compensate for overloaded conditions caused by higher-level load/priority plans

Accomplishing Production Schedules



Concerned with correct mix of equipment, personnel, tooling, and other resources

Valid due date maintenance

Receives and is dependent on input from priority planning functions

Validated by capacity planning at each level

· CRP less common in repetitive and continuous line production

· CRP more common in job shop and batch production environments

· Resource planning typically loads departments/areas in terms of general amounts of work – days, numbers of personnel, numbers of types of finished products.

· RCCP translates these conditions into capacity of key work centers (bottlenecks)

Complications of Capacity

· Lot sizing

o Order timing variability because of aggregation

o Order mix variability

· Bottlenecks

· Complexity

o Uncertainty

o Variability of demand

CRP Inputs

· Routing Data

· Production Order Status

· Schedule of planned manufacturing order releases

· Workcenter data

CRP Output

· Workcenter load report

· Revised schedule of planned manufacturing order releases

Load Unit of Measures

· MPS Level

o Product Category

o Product Type

· CRP Level

o Standard Hours

o Standard Units

Primary sources of load to be measure by CRP

· Open-order status info from Production Control

· Planned order releases produced by MRP

Increasing Capacity

· Overtime/weekends

· Add personnel

· Extra shifts

· Add equipment/facilities

· Reassignment of personnel

Reduce Load

· Decrease Lot Sizes

· Subcontracting

· Hold orders in production control

· Reduce MPS – last resort

Reducing Capacity

· Reassign personnel

· Eliminate shifts/reduce length of shifts

Increasing Load

· Release orders early

· In-source normally purchased or subcontracted items

· Increase Lot sizes

· Increase MPS

Redistributing Load

· Use alternate workcenter

· Use alternate routings

· Adjust operation start dates forward and backward in time

· Revise MPS or lot sizes

· Split orders

Capacity Planning in Repetitive Production

· Fixed Routings

· Variable run times by product mix

· Insignificant queue and wait times

· Setup time only during line changeover

· Production rate constrained by slowest workstation

· Feedback at key points rather than at every operation

*CRP is not often used in this environment*

Measuring performance of Detailed Capacity Planning Process

· Eliminated past due load

· Balanced load according to capacity

· Shorter queues

· Reduced WIP

· Higher productivity

· Reduced idle time

· Reduced overtime

· Increased throughput

Rated Capacity = Hours/shift x Days/Week x Shifts/Day x Number of Machines x Utilization x Efficiency

Master Planning interaction

· Monitors info from key workcenters for overload and underload

Distribution Requirements Planning

· Personnel Planning:

o By wave or shift on daily basis per shipping plan

§ Wave: store orders or routing stops being picked up at a time

o Demonstrated capacity over time

Detailed Scheduling and Planning Internal Interactions

· CRP closes loop with MRP in terms of availability of resources to support MRP priorities

o More real time integration the better

§ Identify orders for which capacity exists

§ Capacity shortage for orders

Execution and Control of Operations Interactions

· Identify orders for which capacity exists

· Identify orders for which there is capacity shortage

· Balance loads and capacity

Advantages of CRP

· Confirms adequate cumulative capacity

· Considers lot sizes and routings

· Provides time-phases visibility of capacity and load imbalances

· Estimates lead time precisely

· Helps eliminate erratic lead times

Disadvantages of CRP

· High amount of computation required

· Computational preciseness is approximation

· Applies mainly to non-repetitive production

· Extensive accurate input data required

· No precise level of detail (function of execution and control)

· Effect of MPS revision not clear

Effects of not doing CRP

· Low Productivity

· Higher WIP

· Bottlenecks

· Late deliveries and shortages

· Long Lead Times

· High Labor costs

One Comment (+add yours?)

    Feb 09, 2013 @ 10:50:11

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