Layout and Flow

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• Layout and Flow

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• Chapter coverage
• Basic layout types
• Selecting a layout type
• Detailed design of a layout

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• Layout
• The layout of an operation is concerned with the
  physical location of its transforming resources,
  that is deciding where to put the facilities,
  machines, equipment and staff in the operation.
• Layout types
• Fixed position layout
• Process layout
• Cell layout
• Product layout

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• Fixed position layout
• In a fixed position layout, the transformed
  resource does not move between its transforming
  resources.
• Equipment, machinery, plant and people who do the
  processing move as necessary because the product
  or customer is either
• Too large
• Too delicate or
• Objects being moved

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• Process layout
• In a process layout, similar processes or
  processes with similar needs are located together
  because
• It is convenient to group them together or
• The utilization of the transforming resource is
  improved
• Different products of customer have different
  requirements therefore they may take different
  routes within the process.
• The flow in a process layout can be very complex.

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An example of a process layout in a library
showing the path of just one customer
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• Cell layout
• In a cell layout, the transformed resources
  entering the operation move into a cell in which
  all the transforming resources it requires in
  located.
• After being processed in the cell, the
  transformed resource may move to a different cell
  in the operation or it may be a finished product
  or service.
• Each cell may be arranged in either a process or
  product layout.
• The cell type layout attempts to bring order to
  the complex flow seen in a process layout.

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The ground floor plan of a department store
showing the sports goods shop-within-a-shop
retail cell
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• Product layout
• In a product layout, the transformed resource
  flow a long a line of processes that has been
  prearranged.
• Flow is clear, predictable and easy to control.

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An army induction centre with uses product
layout
Waiting area
Waiting area
Lecture theatre
Blood test
Doctor
Doctor
Record personal history and medical details
Uniform issuing area
X-ray
Blood test
Doctor
Doctor
X-ray
Blood test
Doctor
Doctor
Uniform store
X-ray
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A restaurant complex with all four basic layout
types
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Volume-variety relationship
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Layout selection steps
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Selecting a layout type
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1) The nature of the basic layout types
B
asic layout
Manufacturing
Service
types
process types
process types
Fixed
Project processes
Project processes
Professional
position layout
services
Jobbing processes
Process layout
Service shops
Batch pro
cesses
Cell layout
Mass services
Mass
processes
Product layout
Continuous
processes
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2) Advantages and disadvantages
Fixed
Process
Cell
Product
position
- Very high mix and product flexibility
- High mix and product flexibility
- Good compromise between cost and flexibility
Lo- w unit costs for high volume
layout
layout
layout
layout
- Gives Opportunities for specialization of
equipment
- Product/customer not moved or disturbed.
- Relatively robust if in the case of disruptions
- Fast throughput.
- Group work can result in good motivation
Advantages
- High variety of tasks for staff
- Easy supervision of equipment of plant
- Gives Opportunities for specialization of
equipment
Low utilization of resources.
Can be costly to rearrange existing layout
Can have low mix and flexibility
- Very high unit cost.
Can have very high WIP
Not very robust to disruption
Can need more plant and equipment
Disadvantages
- Scheduling space and activities can be
difficult.
Complex flow.
Work can be very
repetitive.
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(a) The basic layout types have different fixed
and variable cost characteristics which seem to
determine which one to use. (b) In practice the
uncertainty about the exact fixed and variable
costs of each layout means the decision can
rarely be made on cost alone
3) Consider total cost
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Detailed design of a layout
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• Fixed position layout design
• The location of resources for each project is
  unique and it will be determined on the
  convenience of transforming resources themselves.
• Although there are techniques which held to
  locate resources on fixed position layouts, they
  are not widely used because this layout can be
  very complex and planned schedules do change
  frequently.

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• Process layout design
• When cost of traveling is important
• Collecting information such as
• number of loads per day
• cost per distance traveled
• When process relationship is important
• Relationship chart

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Collecting information in process layout
(b)
LOADS/DAY
If direction is not important, collapses to
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Collecting information in process layout
(c)
LOADS/DAY
(d)
LOADS/DAY
Or alternatively
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Collecting information in process layout
(e)
(f)
LOADS/DAY
If cost of flow differs between work centers,
combine with
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Collecting information in process layout
(g)
DAILY COST/DISTANCE TRAVELLED
To give
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Collecting information in process layout
(h)
(i)
DAILY COST/DISTANCE TRAVELLED
DAILY COST/DISTANCE TRAVELLED
If direction is not important, collapses to
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A relationship chart
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• Cell layout design
• Cells in an operation can be created based on two
  interrelated decisions
• What is the extent and nature of the cell i.e.
  the amount of direct and indirect resources the
  cell has as shown in Fig 7.28
• Which resources to allocate to which cell using
• Cluster analysis which process group naturally
  together
• Parts and family coding based on similar
  characteristics of parts of products
• OR
• Production Flow Analysis (PFA)
• Examines both product requirement and process
  grouping
• (See Fig. 7.31)

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Types of cell
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(a) and (b) Using production flow analysis to
allocate machines to cells
(a)
(b)
Product
Product
Cell A
Machines
Machines
Cell B
Cell C
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• Product layout design
• Product type layout is designed based on a
  technique called line balancing. The technique
  consist of the following steps
• Calculating the required cycle time.
• Calculating the number of stages.
• Producing a precedence diagram.
• Finally allocating activities to the stages.

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• Cycle time
• It is the time between completed products
  emerging from the process.
• Example
• Suppose the regional back-office operation of a
  large bank is designing an operation which will
  process its mortgage applications. The number of
  applications to be processed is 160 per week and
  the time available to process the applications is
  40 hours per week.
• Cycle time 40 1/4 hours 15 minutes
• 160
• 1 product every 15 minutes

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• Number of stages
• Required no. of stages total work content
• required cycle time
• Where the total work content is the total
  quantity of work involved in producing the
  product given in time.
• Example
• Suppose that the bank in the previous example
  calculated that the average total work content of
  processing a mortgage application is 60 minutes.
  The number of stages needed to produce a
  processed application every 15 minutes can be
  calculated
• Required no. of stages 60 minutes 4 stages
• 15 minutes
• If you get a fraction round it up to the higher
  whole number.

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• Precedence diagram
• This is a diagram representing the ordering of
  the elements which comprise the total work
  content of the product or service.
• Two rules when constructing the diagram
• The circles which represent the elements are
  drawn as far to the left as possible.
• None of the arrows which shows the precedence of
  the elements should be vertical.

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• Allocating activities to the stages
• The general approach is to allocate elements from
  the precedence diagram to the first stage,
  starting from the left, until the work allocated
  to the stage is as close to, but less than, the
  cycle time.
• When the stage is full of work without exceeding
  the cycle time, move to the next stage.
• Two rules help to decide which activities to
  allocate to a stage
• Choose the largest that will fit into the time
  remaining at the stage
• Choose the element with the most followers.

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• Balancing loss
• The effectiveness of the line balancing activity
  is measured by the balancing loss.
• This is the time wasted through the unequal
  allocation of work as a percentage of the total
  time invested in processing the product or
  service.
• Balancing loss Total idle time
• No. of stages x Cycle time

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Balancing loss is that proportion of the time
invested in processing the product or service
which is not used productively
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• Worked Example
• Consider Karlstad Kakes, a manufacturer of
  specialty cakes, which has recently obtained
  contract to supply a major supermarket chain with
  a specialty cake in the shape of a space rocket.
  It has been decided that the volumes required by
  the supermarket warrant a special production line
  to perform the finishing, decorating and packing
  of the cake. This line would have to carry out
  the elements shown in the next slide, which also
  shows the precedence diagram for the total job.
  The initial order from the supermarket is for
  5000 cakes a week and the number of hours worked
  by the factory is 40 per week. From this
• The required cycle time 40 hrs x 60 mins 0.48
  mins
• 5000
• The required number of stages 1.68 mins (total
  work content)
• 0.48 mins (required cycle time)
• 3.5 stages

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Element listing and precedence diagram for
Karlstad Kates
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Allocation of elements to stages and balancing
loss for Karlstad Kates