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PERENCANAAN
KEBUTUHAN BAHAN DAN
MANUFAKTUR
JUST IN TIME
Dr. Mohammad Abdul Mukhyi, SE., MM
Resource Requirements Planning
Master ProductionMaster ProductionScheduling (MPS)Scheduling (MPS)
Material RequirementsMaterial Requirements
Planning (MRP)Planning (MRP)
Capacity RequirementsCapacity Requirements
Planning (CRP)Planning (CRP)
AggregateAggregatePlanningPlanning
ResourceResource
RequirementsRequirements
PlanningPlanning
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Material Requirements Planning (MRP)
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Materials Requirements Planning
(MRP)
Computer based system
Explodes Master Schedule (MPS) into required
amounts of raw materials and subassemblies
to support MPS
Nets against current orders and inventories to
develop production and purchased materialordering schedules
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Objectives of MRP
Improve customer service
Reduce inventory investment
Improve plant operating efficiency
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Elements of MRP
Order ChangesOrder Changes
OrderOrder
PlanningPlanning
ReportReport
MRPMRP
SystemSystem
Planned OrderPlanned OrderScheduleSchedule
InventoryInventory
Transaction DataTransaction Data
Bill ofBill of
Materials FileMaterials File
MasterMaster
ProductionProductionScheduleSchedule
InventoryInventoryStatus FileStatus File
ServiceService--PartsPartsOrders andOrders and
ForecastsForecasts
PerformancePerformance
ExceptionException
ReportsReports
Inputs Outputs
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MRP Computer Program Begins with number of end items needed
Add service parts not included in MPS
Explode MPS into gross requirements by consulting
bill of materials file
Modify gross requirements to get net requirements:
Net Requirements = Gross Requirements
+ Allocated Inventory
+ Safety Stock
- Inventory On Hand
Offset orders to allow for lead time
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Outputs of MRPPlanned order schedule - quantity of material
to be ordered in each time period
Changes to planned orders - modifications to
previous planned orders8
Secondary outputs:
Exception reports
Performance reports
Planning reports
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Lot-Sizing in MRP
Lot-size is the quantity ordered/produced at one
time
Large lots are preferred because:
Changeovers cost less and capacity greater
Annual cost of purchase orders less
Price breaks and transportation breaks can be utilized
Small lots are preferred because:
Lower inventory carrying cost
Reduced risk of obsolescence
Shorter cycle time to produce customer order
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The best method, resulting in least cost,
depends on cost and demand patterns.
Lot-Sizing Methods
Economic Order Quantity (EOQ)
does not consider quantity discounts
does not always provide the most economical
approach with lumpy demands
Lot-for-Lot (LFL)
accommodates lumpy demand
Period Order Quantity (POQ)
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Issues in MRP
Lot-Sizing
Useful at lower levels but may drive excess
inventory when applied at higher levels
Net Change versus Regenerative MRP
Net change may generate too many action notices
Regenerative more costly to run but appears to be
easier to manage
. . . more
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Issues in MRP
Safety Stock
Use depends on uncertainty of demand..... more
uncertain the greater the need for safety stock
Assemble-to-Order Firms
MPS and MRP treated separately from Final
Assembly Schedule(FAS)
Use Modular Bill of Material
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MRP I to MRP II
MRP I simply exploded demand (MPS) into
required materials
MRP II became Manufacturing Resource
Planning which provides a closed-loop
business management system
Financial management
Shop floor control
Operations management
Simulation capability
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Evaluation of MRP
Most beneficial to process-focused systems
that have long processing times and complex
multistage production steps
Lead times must be reliable
Must freeze MPS for some time before actual
production... certain demandDifficult to implement
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Capacity Requirements Planning (CRP)
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Capacity Requirements Planning
(CRP)
Tests MPS for feasibility
Utilizes routings to determine labor/machine
loads
If schedule feasible, recommends freezing
If schedule overloads resources, points out
processes that are overscheduled
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Load Schedules
Compares actual labor and machine hours
against available hours
Offsets schedules between successive stages
of production by lead times
Provides feasible MPS and economically
loaded work centers
Promotes system operating efficiency ...lowers costs!
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