Post on 01-Nov-2014
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MATERIALS REQUIREMENT PLANNING
What MRP does?• MASTER SCHEDULE FOR END ITEMS
• DETAILED SCHEDULE FOR RAW MATERIALS AND COMPONENTS USED IN THE END PRODUCT
Dependent demandLumpy demand
MRP
Independent Vs dependent demandIndependentdemandDemand unrelated to demand of other
products.(end products and spare parts)Usually forecastConventional inventory control system (EOQ,
WAGNOR WHITIN) applicable.
Independent Vs dependent demandDependent demand Demand directly related to demand of some other
product.(components, raw materials or sub assemblies)
Requirements derived from delivery schedule of other items.
MRP is the appropriate tool for planning and control for manufacturing inventoriesRaw materialsWIPComponentsSub assemblies
Lead timesOrdering lead times (for purchased parts)
Initiation of receipt of item purchase requisition from vendor(off shelf/ fabricate)
Lead timesManufacturing lead time
Process part through sequence of machines as given on route sheet (operation + non productive
times)
Place order item delivered
In MRP lead times are used to determine starting dates for assembling final products and sub assemblies, for producing component parts and for ordering raw materials.
Inputs to MRPThe master production schedule and other
data.The bill of materials file( the product
structure)The inventory record file.
Master Production ScheduleWeek no: 6 7 8 9 10
Product P1
50 100
Product p2
70 80 25
Etc
TYPICAL INFORMATION IN MPS(a)What end products are to be produced?(b)How many of each product to be produced?(c) When the products are to be ready for shipment? Firms customer ordersDEMAND forecasted demand
demand for individual components or parts (for repair and service- often excluded form MPS since it does not include end product demand)
Inventory record fileAccurate current data on inventory statusGenerally computerized (item master file)Lead times must be established in inventory
record file.Ordering lead time purchasing recordsManufacturing lead time process route
sheets
INVENTORY TRANSACTIONS:- (issue, arrivals, order placement/realization) MUST BE KEPT CURRENT
Week no:678910Product P1
50
100Product p2
708025
Etc
TYPICAL INFORMATION IN MPSWhat end products are to be produced?How many of each product to be produced?When the products are to be ready for shipment? Firms customer ordersDEMAND forecasted demand
demand for individual components or parts (for repair and service- often excluded form MPS since it does not include end product demand)
Master Production ScheduleWeek no: 6 7 8 9 10
Product P1
50 100
Product p2
70 80 25
Etc
INPUTS FOR MRP EXAMPLE p1 p2
S1(1) S2(2) S3(1) S4(1)
C1(1) C2(4) C3(1) C4(2) C5(1) C6(1) C4(1)
M4
PRODUCT STRUCTURE FOR P1 AND P2WEEK
6 7 8 9 10
P1 50 100
P2 70 80 25
INITIAL INVENTORY STATUS FOR M4PERIOD 1 2 3 4 5 6
ITEM MATERIAL, M4
GROSS REQUIREMENTS
SCHEDULED RECEIPTS
40
ON HAND
50 90
NET REQUIREMENTS
PLANNED ORDER RELEASES
LEAD TIMES (IN WEEKS)ASSEMBLY MANUFACTURING ORDERING
P1= 1 C4= 2 M4-3
P2= 1
S2= 1
S3= 1
BASIC MRP LOGICInput MPS, BOM, inventory status, lead timesDo parts explosionOffset requirements by lead timesNetting of requirements from gross by
considering availabilities.Lot sizing of net requirements for
procurement or production
PERIOD 1 2 3 4 5 6 7 8 9 10
ITEM MATERIAL, P1
50 100
GROSS REQUIREMENTS
SCHEDULED RECEIPTS
ON HAND
0
NET REQUIREMENTS
50 100
PLANNED ORDER RELEASES
50 100
PERIOD 1 2 3 4 5 6 7 8 9 10
ITEM MATERIAL, P2
70 80 25
GROSS REQUIREMENTS
SCHEDULED RECEIPTS
ON HAND
0
NET REQUIREMENTS
70 80 25
PLANNED ORDER RELEASES
70
80 25
PERIOD 1 2 3 4 5 6 7 8 9 10
ITEM SUB MATERIAL, S2
100
200
GROSS REQUIREMENTS
SCHEDULED RECEIPTS
ON HAND
0
NET REQUIREMENTS
100
200
PLANNED ORDER RELEASES
100
200
PERIOD 1 2 3 4 5 6 7 8 9 10
ITEM SUB MATERIAL, S3
70 80 25
GROSS REQUIREMENTS
SCHEDULED RECEIPTS
ON HAND
0
NET REQUIREMENTS
70 80 25
PLANNED ORDER RELEASES
70
80 25
PERIOD 1 2 3 4 5 6 7 8 9 10
ITEM COMPONENT, C4
70
280
25 400
GROSS REQUIREMENTS
SCHEDULED RECEIPTS
ON HAND
0
NET REQUIREMENTS
70
280
25 400
PLANNED ORDER RELEASES
70
280 25
400
PERIOD 1 2 3 4 5 6 7 8 9 10
ITEM COMPONENT, M4
GROSS REQUIREMENTS
70 280
25
400
SCHEDULED RECEIPTS
40
ON HAND
50 90 20
NET REQUIREMENTS
-20 260
25
400
PLANNED ORDER RELEASES
260
25
400