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1
FACULTY OF MECHANICAL ENGINEERING
UNIVERSITI TEKNOLOGI MALAYSIA
LAYOUT DESIGN - Part 1
2
PRODUCT, PROCESS AND SCHEDULE
Among the questions to be answered before facility planning can be done
What is to be produced ?
How are the products to be produced ?
When are the products to be produced ?
How much of each product will be produced ?
For how long will the products be produced ?
Where are the products to be produced ?
The answers can be obtained from product design, process design, and schedule design
Product design, process design and schedule design must be done concurrently with facilities design
3
PRODUCT DESIGN
Product design involves the determination of which products to be produced and the detailed design of
individual products
DIFFERENT PRODUCT DIFFERENT FACILITY
Basic product design data can be obtained from production drawings, prototypes of the product, etc
4
PRODUCT DESIGN assembly drawing
Product
5
PROCESS DESIGN
Process design decisions determine whether
a part will be purchased or produced,
Selection of process
Sequence of process
This information can be obtained from parts list, bill of materials, route sheet, assembly chart, precedence
diagram
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PROCESS DESIGN make or buy
Options buy raw materials and do in house fabrication and assembly, or buy component and only do in house
assembly
Scope and magnitude of activities are dependent on level of vertical integration
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PROCESS DESIGN make or buy
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PROCESS DESIGN make or buy
- part lists
The input to the facilities planner is a listing of the items to be made and the items to be purchased.
The listing often takes the form of a parts list or a bill of materials
The parts list provides a listing of the component parts o f a product. In addition, a parts list includes at least
the following
Part number
Part name
Number of parts per product
Drawing references
9
PROCESS DESIGN make or buy
- parts list
parts lists
10
PROCESS DESIGN make or buy
- bill of materials
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PROCESS DESIGN make or buy
- bill of materials
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PROCESS DESIGN selection of process
Product identification process selection (include CAPP) Route sheet
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PROCESS DESIGN selection of process
route sheet
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PROCESS DESIGN sequence of process
Assembly chart
Operation process chart
Precedence diagram
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PROCESS DESIGN sequence of process
assembly chart
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PROCESS DESIGN sequence of process
operation process chart
purchased or produced (make or buy)
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PROCESS DESIGN sequence of process
precedence diagram
purchased or produced (make or buy)
18
SCHEDULE DESIGN
Schedule design decisions provide answers to the questions
How much to produce (volume)
When to produce
Associated with these decisions is the determination of the number of machines, number of shifts, number of
employees, space requirements, storage requirements,
material handling equipment, building size etc.
Consequently, plant layout will be very much affected
Information obtained from Master Production Schedule (MPS)
19
SCHEDULE DESIGN volume-variety
Volume-variety chart (paretos law)
Mass production area for 15% of high-volume items and a job shop arrangement for the remaining
85% of the product mix
Very important in determining the layout type
20
SCHEDULE DESIGN scrap estimates
The market estimate specifies the annual volume to be produced for each product
To produce the required amount of product, the number of units scheduled through production must
equal the market estimate plus a scrap estimate.
Ik = Ok
1 Pk
I1 = On
(1-P1)(1-P2)(1-Pn)
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SCHEDULE DESIGN scrap estimates
A product has a market estimate of 97,000 components and requires three processing steps (turning, milling
and drilling) having scrap estimates of P1 = 0.04, P2 =
0.01 and P3 = 0.03
Input for drilling, I3 = 97,000 = 100,000
1 0.03
Input for milling, I2 = 100,000 = 101,000
1 0.01
Input for turning, I1 = 101,000 = 105,219
1 0.04
22
SCHEDULE DESIGN scrap estimates
Scrap estimates
I1 = 97,000
(1 0.03) (1 0.01) (1 0.04)
= 105,219
23
SCHEDULE DESIGN - Machine Assignment
The combination of product, process and schedule design decisions influences the number of employees
involved in producing the product
Decisions regarding the assignment of machine to operators can affect the number of employees
Assumptions
Semiautomatic production equipment
Machines are identical
Times required to load and unload each machine are constant
Automatic machining time is constant
Time for operator to travel between machines is constant
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SCHEDULE DESIGN - Machine Assignment
Multiple activity chart shows the activities of one or more people and one or more machines
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SCHEDULE DESIGN - Machine Assignment -
multi activity chart
Machine Assignment
The
26
SCHEDULE DESIGN - Machine Assignment
0.5 minute to travel between machines
1.0 minute to load a machine
1.0 minute to unload a machine
6 minutes of automatic machine time
0.5 minute to inspect and pack a finished part
operator loads M-1, walks to M-2, loads M-2, walks to M-3, loads M-3, walks to M-1, unload M-1, load M-1,
inspects and packs the part removed from M-1, travel
to M-2 and so forth
12 minutes to achieve a steady-state condition, thereafter a repeating cycle of 9 minutes in duration
occurs
27
SCHEDULE DESIGN - Machine Assignment -
assignment of three machines to one operator
Machine Assignment
The
28
SCHEDULE DESIGN - Machine Assignment
Let a = concurrent activity time (eg loading / unloading )
b = independent operator activity time (walking / inspecting )
t = independent machine activity time (eg automatic machine time)
n = ideal number of identical machines assigned an operator
m = number of identical machines assigned an operator
Tc = repeating cycle time
Io = ideal operator time during a repeating cycle
Im = ideal time for each machine during a repeating cycle
29
SCHEDULE DESIGN - Machine Assignment
Excluding idle time, each machine cycle requires a + t minutes to complete a cycle. Likewise, the operator
devotes a + b minutes to each machine during a cycle.
Hence, an ideal assignment is
n = (a + t) / ( a + b)
From the example,
n = (2 + 6) / (2 + 1) = 2.67
Not possible to have 2.67 machines so assume 3 machines.
30
SCHEDULE DESIGN - Machine Assignment
Consider what will happen if m machines are assigned
The work content for the operator will be m(a + b) , while a machine cycle will be (a + t) in duration
The repeating cycle will be the larger of the two and the difference in the two will be idle time.
Tc = (a + t) if m n
Im = 0 if m n
Io = Tc m(a + b) if m n
31
SCHEDULE DESIGN - Machine Assignment
If we wish to determine the cost per unit produced by an m machine assignment, use the following
Co = cost per operator-hour
Cm = cost per machine-hour v= Co/Cm TC(m) = cost per unit produced based on an
assignment of m machines per operator
32
SCHEDULE DESIGN - Machine Assignment
The cost per hour of a combination of m machines and an operator totals Co + mCm
Assuming each machine produces one unit during a repeating cycle, the cost per unt produced during a
repeating cycle can be determined as follows;
TC(m) = (Co + mCm)(a + t)/m if m n
to minimize TC(m) when m n,
m should be made as small as possible.
33
SCHEDULE DESIGN - Machine Assignment
To facilitate the determination, let
F = TC(n) / TC(n + 1) = (Co + nCm)(a + t)
n[ Co + (n + 1) Cm ] ( a + b)
which reduces to F = v + n x n v + n + 1 n
34
SCHEDULE DESIGN - Machine Assignment If F < 1, then TC(n) < TC(n + 1) and n machines should
be assigned
If F > 1, then TC(n + 1) < TC(n) and n + 1 machines should be assigned
If F = 1, then either n or n + 1 machines should be assigned.
35
FACULTY OF MECHANICAL ENGINEERING
UNIVERSITI TEKNOLOGI MALAYSIA
THE END