FACILITY LAYOUT

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FACILITY LAYOUT

• Facility layout means
• the configuration of departments, work
  centers, and equipment, with particular emphasis
  on the flow patterns of materials and people
  around, into, and within buildings.
• Layout decisions are very important because they
• - Require substantial investments of money
  and effort
• - Involve long-term commitments
• - Have significant impact on cost and
  efficiency of short-term operations

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Characteristics of the Facility Layout Decisions

• Location of the work centers and departments
  impacts the flow through the system.
• The layout can affect productivity and costs
  generated by the system.
• Layout alternatives are limited by
• the amount and type of space required for the
  various areas
• the amount and type of space available
• the operations strategy
• . . . more

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Characteristics of the Facility Layout Decision

• Layout decisions tend to be
• Infrequent
• Expensive to implement
• Studied and evaluated extensively
• Long-term commitments

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Basic Layout Forms

• Process
• Product
• Cellular
• Fixed position
• Hybrid

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Process (Job Shop) Layouts

• Equipment that perform similar processes are
  grouped together
• Used when the operations system must handle a
  wide variety of products in relatively small
  volumes (i.e., flexibility is necessary)

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Process Layout
Process Layout (functional)
Used for Intermittent processing Job Shop or Batch
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Characteristics of Process Layouts

• General-purpose equipment is used
• Changeover is rapid
• Material flow is intermittent
• Material handling equipment is flexible
• Operators are highly skilled
• Technical supervision is required
• Planning, scheduling and controlling functions
  are challenging
• Production time is relatively long
• In-process inventory is relatively high

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Product (Assembly Line) Layouts

• Operations are arranged in the sequence required
  to make the product
• Used when the operations system must handle a
  narrow variety of products in relatively high
  volumes
• Operations and personnel are dedicated to
  producing one or a small number of products

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Product Layout
Figure 6.4
Raw materials or customer
Station 2
Station 3
Station 4
Finished item
Station 1
Material and/or labor
Material and/or labor
Material and/or labor
Material and/or labor
Used for Repetitive or Continuous Processing
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Characteristics of Product Layouts

• Special-purpose equipment are used
• Changeover is expensive and lengthy
• Material flow approaches continuous
• Material handling equipment is fixed
• Operators need not be as skilled
• Little direct supervision is required
• Planning, scheduling and controlling functions
  are relatively straight-forward
• Production time for a unit is relatively short
• In-process inventory is relatively low

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Cellular Manufacturing (CM) Layouts

• Operations required to produce a particular
  family (group) of parts are arranged in the
  sequence required to make that family
• Used when the operations system must handle a
  moderate variety of products in moderate volumes

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Characteristics of CMRelative to Process Layouts

• Equipment can be less general-purpose
• Material handling costs are reduced
• Training periods for operators are shortened
• In-process inventory is lower
• Parts can be made faster and shipped more quickly

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Characteristics of CMRelative to a Product Layout

• Equipment can be less special-purpose
• Changeovers are simplified
• Production is easier to automate

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Fixed-Position Layouts

• Product remains in a fixed position, and the
  personnel, material and equipment come to it
• Used when the product is very bulky, large, heavy
  or fragile

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Hybrid Layouts

• Actually, most manufacturing facilities use a
  combination of layout types.
• An example of a hybrid layout is where
  departments are arranged according to the types
  of processes but the products flow through on a
  product layout.

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New Trends in Manufacturing Layouts

• Designed for quality and flexibility
• Ability to quickly shift to different product
  models or to different production rates
• Cellular layout within larger process layouts
• Automated material handling such as automated
  guided vehicle systems (AGVs)and automated
  storage and retrieval sytems (AS/RS)
• U-shaped production lines have potential to
  improve employee morale
• More open work areas with fewer walls,
  partitions, or other obstacles
• Smaller and more compact factory layouts
• Less space provided for storage of inventories
  throughout the layout

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A U-Shaped Production Line
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Designing and Analyzing a Product Layout

• Line Balancing Problem
• Characteristics
• Inputs
• Design Procedure
• How Good Is The Layout?

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Line Balancing Problem

• Work stations are arranged so that the output of
  one is an input to the next, i.e., a series
  connection
• Layout design involves assigning one or more of
  the tasks required to make a product to work
  stations
• . . . more

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Line Balancing Problem

• The objective is to assign tasks to minimize the
  workers idle time, therefore idle time costs,
  and meet the required production rate for the
  line
• In a perfectly balanced line, all workers would
  complete their assigned tasks at the same time
  (assuming they start their work simultaneously)
• This would result in no idle time
• . . . more

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Line Balancing Problem

• Unfortunately there are a number of conditions
  that prevent the achievement of a perfectly
  balanced line
• The estimated times for tasks
• The precedence relationships for the tasks
• The combinatorial nature of the problem

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Inputs

• The production rate required from the product
  layout or the cycle time.
• Cycle time is the maximum time allowed at each
  workstation to complete its set of tasks on a
  unit. The cycle time is the reciprocal of the
  production rate and visa versa.
• All of the tasks required to make the product
• It is assumed that these tasks can not be divided
  further
• . . . more

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Inputs

• The estimated time to do each task
• The precedence relationships between the tasks
• These relationships are determined by the
  technical constraints imposed by the product
• These relationships are displayed as a network
  known as a precedence diagram

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Precedence Diagram
Precedence diagram Tool used in line balancing
to display elemental tasks and sequence
requirements
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Line Balancing Procedure

• Determine which tasks must be performed to
  complete one unit of a product
• Draw a precedence diagram which shows the
  sequence in which the tasks must be performed.
• Estimate task times
• 4 Calculate the cycle time for the line.
  Remember the cycle time is the reciprocal of the
  production rate. Make sure the cycle time is
  expressed in the same time units as the estimated
  task times.
• . . . more

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Line Balancing Procedure

• Calculate the minimum number of workstations that
  can provide the required production rate.
• Cycle TimeProductive Time per hour / Demand per
  hour
• min of workstations Sum of all task times /
  Cycle Time
• 6. Use a line-balancing heuristic such as
  longest-task-time heuristic to assign tasks to
  workstations so that the production line is
  balanced.

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Design Procedure

• 7. Open a new workstation with the full cycle
  time remaining.
• 8. Determine which tasks are feasible, i.e., can
  be assigned to this work station at this time.
  For a task to be feasible, two conditions must be
  met
• All tasks that precede that task must have
  already been assigned
• The estimated task time must be less than or
  equal to the remaining cycle time for that work
  station.

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Design Procedure

• Note that if there is only one feasible task,
  assign it to the work station. If there is more
  than one feasible task, use the heuristic (step
  6) to determine which task to assign. Reduce the
  work stations remaining cycle time by the
  selected tasks time.
• If there are no feasible tasks and
  assignments to that work station are complete, go
  back to step 7 (or stop, if all tasks have been
  assigned).

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Longest-Task-Time Heuristic

• Heuristic methods, based on simple rules, have
  been used to develop very good, not optimal,
  solutions to line balancing problems.
• Longest-Task-Time Heuristic - adds tasks to a
  workstation one at a time in the order of task
  precedence, choosing - when a choice must be made
  - the task with the longest time.

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How Good Is the Design?

• Balance Efficiency is

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Example 1 The ALB Problem

• Youve just been assigned the job a setting up an
  electric fan assembly line with the following
  tasks

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Example 1 The ALB Problem The Precedence Diagram

• Which process step defines the maximum rate of
  production?

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Example 1 The ALB ProblemThe Bottleneck
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Example 1 The ALB Problem We want to assemble
100 fans per day

• What do these numbers represent?

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Example 1 The ALB Problem We want to assemble
100 fans per day
Why should we always round up?
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Example 1 The ALB ProblemSelected Task
Selection Rules

• Primary Assign tasks according to the largest
  number of following tasks.
• Secondary (tie-breaking) Assign tasks in order
  of the longest operating time

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Example 1 The ALB ProblemSelected Task
Selection Rules

• Precedence Diagram

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Station 3
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Station 3
A (4.2-22.2)
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Station 3
A (4.2-22.2) B (2.2-11.2)
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Station 3
A (4.2-22.2) B (2.2-11.2) G (1.2-1 .2) Idle
.2
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Station 3
A (4.2-22.2) B (2.2-11.2) G (1.2-1 .2) Idle
.2
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Station 3
A (4.2-22.2) B (2.2-11.2) G (1.2-1 .2) Idle
.2
C (4.2-3.25).95 Idle .95
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Station 3
A (4.2-22.2) B (2.2-11.2) G (1.2-1 .2) Idle
.2
C (4.2-3.25).95 Idle .95
D (4.2-1.2)3
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Station 3
A (4.2-22.2) B (2.2-11.2) G (1.2-1 .2) Idle
.2
C (4.2-3.25).95 Idle .95
D (4.2-1.2)3
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Station 3
A (4.2-22.2) B (2.2-11.2) G (1.2-1 .2) Idle
.2
C (4.2-3.25).95 Idle .95
D (4.2-1.2)3 E (3-.5)2.5
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Station 3
A (4.2-22.2) B (2.2-11.2) G (1.2-1 .2) Idle
.2
C (4.2-3.25).95 Idle .95
D (4.2-1.2)3 E (3-.5)2.5 F (2.5-1)1.5
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Station 3
D (4.2-1.2)3 E (3-.5)2.5 F (2.5-1)1.5 H
(1.5-1.4).1
C (4.2-3.25).95
A (4.2-22.2) B (2.2-11.2) G (1.2-1 .2)
Idle.2 Idle.95 Idle.1
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Example 1 The ALB Problem

• Which station is the bottleneck?
• What is the effective cycle time?