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Chapter 12 - MRP and ERP
6. Given:
The company that makes a table wants to ship 100 units at the beginning of day 4, 150 units at the
beginning of day 5, and 200 units at the beginning of day 7. Receipts of 100 wood sections are
scheduled at the beginning of day 2. On hand balances: Braces = 60 and Legs = 120. Lead times
Chapter 12 - MRP and ERP
Wood Sections(2)
Lot size: Lot-for-Lot
Beg.
Inv.
1
2
3
4
5
6
7
Gross requirements
200
300
400
Scheduled receipts
100
Projected on hand
0
0
100
100
0
0
0
0
Net requirements
100
300
400
Planned-order receipts
100
300
400
Planned-order releases
400
400
Notes:
POH4 = [POH3 + Planned-Order Receipts3 – Gross Requirements3] + Scheduled Receipts4
POH4 = [100 + 100 – 200] + 0 = 0.
Planned-Order Releases (day 2) = 100 from Planned-Order Receipts of 100 in day 3 (lead time = 1
day for quantities of 1-200) + 300 from Planned-Order Receipts of 300 in day 4 (lead time = 2 days
for quantities of 201-550) = 400.
Chapter 12 - MRP and ERP
12-23
Legs(4)
Lot size: Lot-for-Lot
Beg.
Inv.
1
2
3
4
5
6
7
Gross requirements
400
600
800
Scheduled receipts
Projected on hand
120
120
120
120
0
0
0
0
Net requirements
280
600
800
Planned-order receipts
280
600
800
Planned-order releases
880
800
Notes:
Gross Requirements (day 3) = Planned-Order Releases of 100 Tables * 4 = 400.
Gross Requirements (day 4) = Planned-Order Releases of 150 Tables * 4 = 600.
Gross Requirements (day 6) = Planned-Order Releases of 200 Tables * 4 = 800.
POH3 = [POH2 + Planned-Order Receipts2 – Gross Requirements2] + Scheduled Receipts3
POH3 = [120 + 0 – 0] + 0 = 120.
days for quantities of 201-550) + 600 from Planned-Order Receipts of 600 in day 4 (lead time = 3
days for quantities of 551-999) = 880.
Planned-Order Releases (day 3) = 800 from Planned-Order Receipts of 800 in day 6 (lead time = 3
days for quantities of 551-999).
Chapter 12 - MRP and ERP
12-24
7. Given:
80 units of end item X are needed at the beginning of week 6, and another 30 units are needed at
the beginning of week 8. D can be ordered only in whole cases (50 units per case). One case of D
(50 units) is received automatically every other week, beginning in week 1. On hand balances: B
= 30 and D = 20 units. Lead times are a function of quantity as shown in the table below. The
product structure tree is shown below also:
Quantity
Lead Time
1-100
1 wk
101-200
2 wk
201-300
3 wk
301+
4 wk
Prepare a material requirements plan for component D using lot-for-lot ordering for all items
except D. We will need to prepare material plans for X, B, and D.
Master
Schedule for: X
Week
1
2
3
4
5
6
7
8
Quantity
80
30
X
Lot size: Lot-for-Lot
Beg.
Inv.
1
2
3
4
5
6
7
8
Gross requirements
80
30
Scheduled receipts
Projected on hand
0
0
0
0
0
0
0
0
0
Net requirements
80
30
Planned-order receipts
80
30
Planned-order releases
80
30
Notes:
Planned-Order Releases (week 5 and week 7) have a lead time of 1 week (lead time = 1 week for
quantities of 1-100).
B(2)
D(3)
D(2)
F(2)
X
Chapter 12 - MRP and ERP
B(2)
Lot size: Lot-for-Lot
Beg.
Inv.
1
2
3
4
5
6
7
8
Gross requirements
160
60
Scheduled receipts
Projected on hand
30
30
30
30
30
30
0
0
0
Net requirements
130
60
Planned-order receipts
130
60
Planned-order releases
130
60
Gross Requirements (week 5) = Planned-Order Releases of 80 X * 2 = 160.
Gross Requirements (week 7) = Planned-Order Releases of 30 X * 2 = 60.
POH6 = [POH5 + Planned-Order Receipts5 – Gross Requirements5] + Scheduled Receipts6
POH6 = [30 +130 – 160] + 0 = 0.
Planned-Order Releases (week 3) = 130 from Planned-Order Receipts of 130 in week 5 (lead time = 2
Chapter 12 - MRP and ERP
8. Given:
Oh No! Inc. sells three models: A, B, and C. Lead times are 1 week for all items except C (2
weeks). On hand balances: B = 10, C = 10, and D = 25 units. Lot-sizing rules are lot-for-lot for all
items except D, which must be ordered in multiples of 100. There is a scheduled receipt of 100
units of D in week 1. The master schedule shows that 40 units of A are needed at the beginning of
week 4, 60 units of B at the beginning of week 5, and 30 units of C at the beginning of week 6.
The product structure tree for each item is shown below:
Master
Schedule for: A
Week
1
2
3
4
5
6
Quantity
40
A LT = 1
Lot size: Lot-for-Lot
Beg.
Inv.
1
2
3
4
5
6
Gross requirements
40
Scheduled receipts
Projected on hand
0
0
0
0
0
0
0
Net requirements
40
Planned-order receipts
40
Planned-order releases
40
Master
Schedule for: B
Week
1
2
3
4
5
6
Quantity
60
B LT = 1
Lot size: Lot-for-Lot
Beg.
Inv.
1
2
3
4
5
6
Gross requirements
60
Scheduled receipts
Projected on hand
10
10
10
10
10
10
0
Net requirements
50
Planned-order receipts
50
Planned-order releases
50
Chapter 12 - MRP and ERP
12-27
Master
Schedule for: C
Week
1
2
3
4
5
6
Quantity
30
C LT = 2
Lot size: Lot-for-Lot
Beg.
Inv.
1
2
3
4
5
6
Gross requirements
30
Scheduled receipts
Projected on hand
10
10
10
10
10
10
10
Net requirements
20
Planned-order receipts
20
Planned-order releases
20
D, D(2), & D(4) LT = 1
Lot size: Multiples of 100
Beg.
Inv.
1
2
3
4
5
6
Gross requirements
40
180
Scheduled receipts
100
Projected on hand
25
125
125
125
85
5
5
Net requirements
95
Planned-order receipts
100
Planned-order releases
100
Notes:
Gross Requirements (week 3) = Planned-Order Releases of 40 A * 1 = 40.
Gross Requirements (week 4) = (Planned-Order Releases of 50 B * 2) + (Planned-Order
Releases of 20 C * 4) = 100 + 80 = 180.
POH4 = [POH3 + Planned-Order Receipts3 – Gross Requirements3] + Scheduled Receipts4
POH4 = [125 + 0 – 40] + 0 = 85.
POH5 = [POH4 + Planned-Order Receipts4 – Gross Requirements4] + Scheduled Receipts5
POH5 = [85 + 100 – 180] + 0 = 5.
Planned-Order Receipts (week 5) = 1 * 100 = 100 (must order in multiples of 100).
Chapter 12 - MRP and ERP
12-28
Education.
9. Given:
50 chain saws are needed at the start of week 8. The inventory information (shown in bold) and
the product structure tree are listed below in the problem solution:
a. Product tree structure:
Master schedule:
Master
Schedule for:
Saw
Week
1
2
3
4
5
6
7
8
Quantity
50
b. Material requirements plan for E using lot-for-lot ordering for all items. We will need to
prepare material plans for Saw, A, C, and E.
Master
Schedule for:
Saw
Week
1
2
3
4
5
6
7
8
Quantity
50
Saw LT = 2
Lot size: Lot-for-Lot
Beg.
Inv.
1
2
3
4
5
6
7
8
Gross requirements
50
Scheduled receipts
Projected on hand
15
15
15
15
15
15
15
15
15
Net requirements
35
Planned-order receipts
35
Planned-order releases
35
Saw
A(2)
B
C(4)
E(3) D D(2) F(3) E(2) D(2)
Chapter 12 - MRP and ERP
12-29
A(2) LT = 1
Lot size: Lot-for-Lot
Beg.
Inv.
1
2
3
4
5
6
7
8
Gross requirements
70
Scheduled receipts
Projected on hand
10
10
10
10
10
10
10
0
0
Net requirements
60
Planned-order receipts
60
Planned-order releases
60
Notes:
Gross Requirements (week 6) = Planned-Order Releases of 35 Saws * 2 = 70.
C(4) LT = 2
Lot size: Lot-for-Lot
Beg.
Inv.
1
2
3
4
5
6
7
8
Gross requirements
140
Scheduled receipts
Projected on hand
65
65
65
65
65
65
65
0
0
Net requirements
75
Planned-order receipts
75
Planned-order releases
75
Notes:
Gross Requirements (week 6) = Planned-Order Releases of 35 Saws * 4 = 140.
E(3) & E(2) LT = 1
Lot size: Lot-for-Lot
Beg.
Inv.
1
2
3
4
5
6
7
8
Gross requirements
150
180
Scheduled receipts
Projected on hand
10
10
10
10
10
0
0
0
0
Net requirements
140
180
Planned-order receipts
140
180
Planned-order releases
140
180
POH5 = [POH4 + Planned-Order Receipts4 – Gross Requirements4] + Scheduled Receipts5
POH5 = [10 + 140 – 150] + 0 = 0.
POH6 = [POH5 + Planned-Order Receipts5 – Gross Requirements5] + Scheduled Receipts6
POH6 = [0 + 180 – 180] + 0 = 0.
