Session 11 Multi-Level Bill of Material Explosion http://www.pom.edu/mpc/lectures_in_manufacturing_planning.htm lecture session 11

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Session 11Multi-Level Bill of Material
Explosionhttp//www.pom.edu/mpc/lectures_in_manuf
acturing_planning.htmlecture session 11

• Product Structure Diagrams
• Multi-Level Bill of Material Explosion Linking
  MRP Records
• Front and Back Loaded Schedules
• Lead Time Offsetting
• Technical Issues

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Product Structure Example P301 Computer

• Memory board (M)
• Assemble 4 RAM chips and 1 switch (S) onto a
  board type (X).
• Arithmetic board (A)
• Assemble 1 integrated microprocessor (Z) with 2
  ROM chips and 1 switch (S) onto a board type (Y).

M
A
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Product Structure Example P301 Computer
(Continued)

• Processor unit (P)
• Working from back to front of the box casing (B),
  assemble one switch (S) to the inside of each of
  the 4 plug connections at the back of the box.
  Then fit 4 memory boards (M) into the 4 identical
  rows of connectors. Finally, fit the arithmetic
  board (A) into the front connector row.

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Product Structure Example P301 Computer
(Continued)

• Final Assembly
• The video unit (V) and the keyboard unit (K) have
  been preassembled (with connecting cables).
  Simply connect the sockets on the end of their
  cables to the corresponding plugs at the rear of
  the processor unit (P). The computer is now ready
  to use.

P
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Product Structure Example P301 Computer
(Continued)

1. Draw the product structure tree according to the
   assembly directions.
2. Determine low-level codes for each product.
3. Assume no inventory of any item. How many of each
   part should be available to assemble one
   completed unit?

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Product Structure DiagramP301 Computer

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Product Structure DiagramP301 Computer
(Continued)

• b., c.

Item Low-Level Code Quantity Required for One Unit
A Arithmetic Board 2 1
B Box Casing 2 1
C Ram Chip 3 16
K Keyboard Unit 1 1
M Memory Board 2 4
P Processor Unit 1 1
R ROM Chip 3 2
S Switch 3 9
V Video Unit 1 1
X Board Type X 3 4
Y Board Type Y 3 1
Z - Microprocessor 3 1
Assuming no inventory for any item Assuming no inventory for any item Assuming no inventory for any item
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Product Structure DiagramP301 Computer

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Linking MRP Records Examples

• The Big B Bike and Trike Shop produces two basic
  bikes called A and B. Each period, Paul, the
  owner. plans to assemble 10 A bikes and 5 B
  bikes. Given this information and the following
  product structure diagrams for A and B, fill out
  the MRP records for component parts G and Y for
  the next seven periods.

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Linking MRP Records Examples (Continued)
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Linking MRP Records Examples (Continued)
MPS Bike B 5 u/period
Bike A 10 u/period
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Linking MRP Records Problem 8 Part a
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Linking MRP Records Problem 8 Part b

• Suppose 10 units of safety stock are required for
  part Y. What changes would result in the records?
  Would the MRP system produce any exception
  messages?
• Exception message period 2 below safety stock.
• There will be an increase in the order in period
  1 from 18 to 28 units.

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Front and Back Scheduling Example

• Peters Power Tools (PPT) has
• just received an order for 50
• PPT band saws, to be shipped at
• the beginning of period 9.
• Information concerning the saw
• assembly is given in this table.
• Draw the product structure diagram

PPT band saw PPT band saw PPT band saw
Item Lead time (periods) Components
Saw 2 A(2), B, C(3)
A 1 E(3), D
B 2 D(2), F(3)
C 2 E(2), D(2)
D 1
E 1
F 3
Number of parts required to make one parent. Number of parts required to make one parent. Number of parts required to make one parent.
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PPT Product Structure Diagram

• Draw the product structure diagram

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PPT Front Loaded Schedule

• Construct a Gantt chart for the new order using
  front scheduling logic.

E
D
F F F
A
C C
B B
SAW SAW


1 2 3 4 5 6 7 8 9
Period Number Period Number Period Number Period Number Period Number Period Number Period Number Period Number Period Number
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PPT Back Loaded Schedule

1. Construct a Gantt chart for the new order using
   back scheduling logic.

F F F
D
E
B B
C C
A
SAW SAW


1 2 3 4 5 6 7 8 9
Period Number Period Number Period Number Period Number Period Number Period Number Period Number Period Number Period Number
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Scheduling Explanation

• The front scheduling logic causes all the work to
  be done ahead of schedule which creates
  additional inventory and occupies resources that
  could be used on other orders. MRP applies back
  scheduling logic so that parts and components are
  completed when they are needed to fill customer
  orders.

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Lead Time Offsetting

• Precedent Relationship
• Components of Lead Time
• Set-up Time
• Run Time
• Material Handling Time
• Queue Time
• Staging Time
• Cumulative Lead Time
• Advantage of Back Loaded Schedules

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Technical Issues

• Low Level Coding
• Indented Bill of Materials
• Pegging
• Cumulative Lead Time
• Planning Horizon
• Processing Frequency
• Regeneration
• Net Change