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Process Selection and Facility Layout


Process Selection  
and Facility Layout


  • Process selection
    • Deciding on the way production of goods or services will be organized
  • Major implications
    • Capacity planning
    • Layout of facilities
    • Equipment
    • Design of work systems
 

Introduction


Forecasting 

Product and 
Service Design
 

Technological 
Change
 

Capacity 
Planning
 

Process 
Selection
 

Facilities and 
Equipment
 

Layout 

Work 
Design
 

Process Selection and System Design 

Inputs 

Outputs


Key aspects of process strategy

    • Capital intensive – equipment/labor
    • Process flexibility
    • Adjust to changes
      • Design
      • Volume
      • Technology
 

Process Strategy


  • Variety
    • How much
  • Flexibility
    • What degree
  • Volume
    • Expected output
 

Job Shop 

Batch 

Repetitive 

Continuous 

Process Selection


Process types


  • Job shop
    • Small scale, wide variety of goods
  • Batch
    • Moderate volume, flexible
  • Repetitive or assembly line
    • High volumes of standardized goods or services
  • Continuous
    • Very high volumes of non-discrete goods
  • Projects 
    • Non-routine work, unique set ob objectives, limited timeframe and resources
 
 

Process types and volume


Product – Process Matrix 

The diagonal of the matrix represents the ideal choice of processing system for a given set of circumstances.


Functions/activities affected by process choice 

Job variety, process flexibility, unit cost 

Volume 

Limited 
(not ongoing)


Some examples 
(find the process type of each) 

Movie production

Bakery

Restaurant  
(non fast food)

University

Car repairing  
(car mechanic shop)

Oil mining

Producing office tools

Veterinarian 
 

Project

Batch

Batch 

Batch

Job shop 

Continuous

Repetitive

Job shop

 


Product and service life cycles 

  • Alongside the life cycle the sales and with it the production volume can change.
  • Thus managers must be aware of the change in the optimal processing system.  
    (the necessity of change is highly dependent on the particular good or service)

Example 

  • Computer building shop in a garage (working for order only, one computer at a time for given purposes)
  • The shop hires some workers and producing some dozens of computers for one customer at a time
  • Computer factory is established, creating large number of computer series
  • The R&D function of the firm invents a new computer prototype
 
 

Job shop 

Batch 

Repetitive 

Project


Product/Service Profiling 

  • Linking key product or service requirements to process capabilities.
  • Design the process with taking into consideration the following:
    • Range of products/services
    • Expected order size
    • Pricing
    • Expected frequency of changes in schedules etc.
    • Order-winning requirements

Sustainable production 

  • Non-polluting
  • Conserving natural resources & energy
  • Economically efficient
  • Safe and healthful for workers, communities and consumers
  • Socially and creaqtively rewarding for workers
 
 
 

 


  • Automation: Machinery that has sensing and control devices that enables it to operate
    • Fixed automation
    • Programmable automation
 

Automation of production and services


Advantages of automation 

  • Low variability in performance and quality
  • Machines do not
    • get bored or distracted
    • go out on strike or ask for higher wages
    • lower variable costs

 


Disadvantages 

  • Higher initial (investment) cost and
  • Higher fixed costs
  • Lower felxibility
  • Higher skills needed
  • Lower morale of human workforce
  • Need for standardisation
    • Products
    • Processes
    • Equipment and materials etc.

 


  • Computer-aided design and manufacturing systems (CAD/CAM)
  • Numerically controlled (NC) machines
    • Computerized numerical control (CNC)
    • Direct numerical control (DNC)
  • Robot: mechanical arm + power supply + controller
  • Manufacturing cell
  • Flexible manufacturing systems (FMS)
  • Computer-integrated manufacturing (CIM)
 

Automation


  • Layout: the configuration of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system
 

Facilities Layout


  • Requires substantial investments of money and effort
  • Involves long-term commitments
  • Has significant impact on cost and efficiency of short-term operations
 

Importance of Layout Decisions


The Need for Layout Decisions 

  • Inefficient operations
        • High (variable) cost
        • Bottlenecks
  • Changes in the design of products or services
  • The introduction of new products or services
  • Safety
  • Changes in environmental or other legal requirements
  • Changes in volume of output or mix of products
  • Changes in methods and equipment
  • Morale problems

 


Objectives of facility layout 

Main: smooth flow of work, material and information 

Supporting objectives:


  • Product layouts
  • Process layouts
  • Fixed-Position layout
  • Combination layouts: 
    • Cellular layout (& group technology)
    • Flexible manufacturing systems
 
 

Basic Layout Types


  • Product layout
    • Layout that uses standardized processing operations to achieve smooth, rapid, high-volume flow
  • Process layout
    • Layout that can handle varied processing requirements
  • Fixed Position layout
    • Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed
 

Basic Layout Types


Used for Repetitive or Continuous Processing 

Product Layout


  • High rate of output
  • Low unit cost
  • Labor specialization
  • Low material handling cost
  • High utilization of labor and equipment
  • Established routing and scheduling
  • Routing accounting and purchasing
 
 

Advantages of Product Layout


  • Creates dull, repetitive jobs
  • Poorly skilled workers may not maintain equipment or quality of output
  • Fairly inflexible to changes in volume
  • Highly susceptible to shutdowns
  • Needs preventive maintenance
  • Individual incentive plans are impractical
 

Disadvantages of Product Layout


A U-Shaped Production Line


Advantages/disadvantages of  
U-shaped lines 

  • Shorter distances for workers & machines
  • Permits communication thus facilitates teamwork
  • More flexible work assignments
  • Optimal if the facility has the same entry and exit point
 
  • If lines are highly automated, there is no need for communication and travel
  • If entry points are on the opposite side as exit points
  • Noise and contamination factors are increased in the U-shape

Dept. A 

Dept. B 

Dept. D 

Dept. C 

Dept. F 

Dept. E 

Used for Intermittent processing

Job Shop or Batch 

Process Layout

(functional) 

Process Layout


  • Can handle a variety of processing requirements
  • Not particularly vulnerable to equipment failures
  • Equipment used is less costly
  • Possible to use individual incentive plans
 

Advantages of Process Layouts


  • In-process inventory costs can be high
  • Challenging routing and scheduling
  • Equipment utilization rates are low
  • Material handling slow and inefficient
  • Complexities often reduce span of supervision
  • Special attention for each product or customer
  • Accounting and purchasing are more involved
 

Disadvantages of Process Layouts


Fixed-position layouts 

  • The product or project remains stationary and workers, materials, and equipment are moved as needed.
  • If weight, size, bulk, or some other factor makes it undesirable or extremely difficult to move the product.
  • E.g. firefighting, road-building, home-building, drilling for oil etc.
  • Cellular Production
    • Layout in which machines are grouped into a cell that can process items that have similar processing requirements
  • Group Technology
    • The grouping into part families of items with similar design or manufacturing characteristics
    • Makes cellular production much more effective
 

Cellular Layouts


Traditional process layout 

Cellular layout


Dimension 

Functional 

Cellular 

Number of moves between departments 

many 

few 

Travel distances 

longer 

shorter 

Travel paths 

variable 

fixed 

Job waiting times 

greater 

shorter 

Throughput time 

higher 

lower 

Amount of work in process 

higher 

lower 

Supervision difficulty 

higher 

lower 

Scheduling complexity 

higher 

lower 

Equipment utilization 

lower 

higher 

Functional vs. Cellular Layouts


Flexible manufacturing systems 

  • FMS: a group of machnies designed to handle intermittent processing requirements and produce a variety of similar products.
  • CIM (Computer Integrated Manufacturing): a system of linking a broad range of manufacturing activities through an integrating computer system
  • Warehouse and storage layouts 
    • Minimizing movement & picking time and cost
  • Retail layouts
    • Presence & influence of customers
  • Office layouts:
    • Information is computerized, image of openness
 

Service Layouts


Design Product Layouts: Line Balancing 

Line Balancing is the process of assigning

tasks to workstations in such a way that the workstations have approximately equal time requirements.

This way the idle time will be minimized, utilization will be maximized. 

Specialization: dividing work into elemental tasks that can be performed quickly and routinely.

 


Cycle Time 

Cycle time is the maximum time allowed at each workstation to complete its set of tasks on a unit. 

tmax <  Cycle time  < ∑t


Determine the Minimum Number  
of Workstations Required 

Theoretical Nmin is not necessarily will be the Nactual. The latter is affected by other technical and practical considerations, too.    Nmin Nactual 

(rounded up to the next integer)


A diagram that shows elemental tasks and their precedence requirements. 

A simplified precedence

diagram 

a 

b 

c 

d 

e 

0.1 min. 

0.7 min. 

1.0 min. 

0.5 min. 

0.2 min. 

Precedence Diagram


Assume that the desired output is 480 units per day. The facility is working 8 hours a day. The elemental tasks and their connections are shown on the previous slide. 

  • Calculate the cycle time.
  • Calculate the minimum number of workstations.
  • Arrange the tasks to these workstations in the order of the greatest number of following tasks.
 
 

Example 1: Assembly Line Balancing


 
 
Workstation
 

 
Time 
Remaining
 

 
 
Eligible
 

 
Assign 
Task
 

Revised 
Time  
Remaining
 

 
Station 
Idle Time
 


1.0

0.9

0.2 

a, c *

c **

none*** 

a

c


0.9

0.2 
 
 

0.2 


1.0 



0.0 

0.0 


1.0

0.5

0.3 

d

e


d

e


0.5

0.3 
 

0.3

Total: 0.5 

Example 1 Solution 

*     Tasks that have no predecessors.

**   b is not eligible, because it needs more time than than the remaining.

*** Every available task needs more time than 0.2.


Efficiency %= 100 x (1 – Percentage of  idle time) 

Calculate Percent Idle Time and efficiency


Line balancing procedure


  • Assign tasks in order of most following tasks.
    • Count the number of tasks that follow
  • Assign tasks in order of task time.
  • Assign tasks in order of greatest positional weight.  
    • Positional weight is the sum of each task’s time plus the times of all following tasks.
 

Line Balancing Heuristics


Example 2 

Working day is 8 hours and the desired output rate is 400 units per day. 

Draw the precedence diagram.

Compute the cycle time & the minimum theoretical number of workstations required.

Assign tasks to workstations according to the greatest number of following tasks. Tiebreaker: longest processing time goes first.

Calculate Percent idle time & efficiency.

 


Solution 2 

CT = (8*60)/400= 1.2; Nmin = ∑ti / CT = 3.17 → 4 


 


 







Work station 

Tasks assigned 

Idle time 

WS1 

a,c,b 


WS2 

d,e 

0.3 

WS3 


0.2 

WS4 

g,h 

0.5 

Percentage idle time = 1.0 / (4*1.2) = 20.83%

Efficiency = 100 – 20.83 = 79.17%


Other approaches 

  • Paralell workstations
  • Cross-train workers (dynamic line balancing)
  • Mixed model line  
    (more product on the same line)

1 min. 

2 min. 

1 min. 

1 min. 

30/hr. 

30/hr. 

30/hr. 

30/hr. 

1 min. 

1 min.  
on average 

1 min. 

1 min. 

60/hr. 

30/hr. 

30/hr. 

60/hr. 

30/hr. 

30/hr. 

Bottleneck 

Parallel Workstations 

Parallel Workstations 

2 min. 

2 min.


Thank you for your attention


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