Practice Problems: Chapter 14, Material Requirements Planning
Problem 1 (page 513):
a. Prepare a Bill-of-materials tree
b. Revise the BOM according to low-level coding.
Problem 2: Determine the overall lead time for the two end products TOL and HQ.
Item
X
A
B
C
D
E
F
G
Lead time
Chair
Leg assembly
Seat
Back assembly
Legs
Cross bar
Slide rails
Back supports
1
1
2
2
2
1
2
3
Problem 3: Suppose that the production of 200 Chair X is planned. Further suppose that
the following inventories are available. Determine the net requirements for all the
component items.
Item
X
A
B
C
D
E
F
G
Item
Available
20
50
250
40
60
50
150
400
Gross requirement
Available
Net requirement
MRP Formulas:
Gross requirements
(GR)
The total expected demand for an item or raw material during each time
period without regard to the amount on hand. (For end items it is MPS;
for components, these quantifies are derived from the planned-order
releases of their immediate “parents.”
Scheduled receipts
(SR)
Open orders that have been placed and are scheduled to arrive from
vendors or elsewhere in the pipeline by the beginning of a period.
Projected on hand
(POH)
Expected inventory available on hand at the beginning of each time
period
Net requirements (NR)
The actual amount needed in each time period.
Planned-order receipts
(PORT)
The quantity expected to be received by the beginning of the period in
which it is shown.
Planned-order releases
(PORL)
Equals planned-order receipts offset by lead time. This amount
generates gross requirements at the next level in the assembly or
production chain. When an order is executed, it is removed from
“planned-order releases” and entered under “scheduled receipts."
GR
Planned-order releases of immediate “parents” x No. required per unit
SR
Given
POH
POH of previous period + SR + PORT – GR
NR
GR – (POH + SR + PORT) if positive, otherwise zero
PORT
NR, in the case of Lot for Lot
PORL
PORT offset by lead time
Problem 4: Develop a net material requirements plan for Chair X.
Available Lead time
Item
Scheduled Receipts
X
A
B
C
D
E
F
G
Week #1 = 100
Week #1 =120, Week #2 = 120
Week #1 =250
Week #1 =80, Week #2 = 100
20
50
250
40
60
50
150
400
Week #1 = 300
Week #1 = 500
1
1
2
2
2
1
2
3
MPS: (Quantities must be made available in the given week)
Week:
MPS for X
1
80
2
120
3
100
4
120
5
120
6
100
Item
LT =
Week:
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
Gross requirement
Scheduled receipts
Projected on-hand
Net Requirement
Planned receipts
Planned order releases
Item
LT =
Week:
Gross requirement
Scheduled receipts
Projected on-hand
Net Requirement
Planned receipts
Planned order releases
Item
Week:
Gross requirement
Scheduled receipts
Projected on-hand
Net Requirement
Planned receipts
Planned order releases
LT =
Item
LT =
Week:
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
Gross requirement
Scheduled receipts
Projected on-hand
Net Requirement
Planned receipts
Planned order releases
Item
LT =
Week:
Gross requirement
Scheduled receipts
Projected on-hand
Net Requirement
Planned receipts
Planned order releases
Item
Week:
Gross requirement
Scheduled receipts
Projected on-hand
Net Requirement
Planned receipts
Planned order releases
LT =
Item
LT =
Week:
1
2
3
4
5
6
1
2
3
4
5
6
Gross requirement
Scheduled receipts
Projected on-hand
Net Requirement
Planned receipts
Planned order releases
Item
Week:
Gross requirement
Scheduled receipts
Projected on-hand
Net Requirement
Planned receipts
Planned order releases
LT =