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Process choice and production layout

 

Contents

 

  1. Management & Development Center-Home

  2. Process Selection and System Design

  3. Process Types

  4. Questions Before Selecting A Process

  5. Product – Process Matrix

  6. Variety, Flexibility, & Volume

  7. Automation

  8. Robot

  9. Flexible Manufacturing System

  10. Computer-integrated manufacturing

  11. Service Blueprint

  12. Service Process Design

  13. Layout

  14. The Need for Layout Decisions

  15. The Need for Layout Design (Cont’d)

  16. Basic Layout Types

  17. A Flow Line for Production or Service

  18. A U-Shaped Production Line

  19. Basic Layout Types

  20. Layout types: Product or Process Make your pick

  21. Basic Layout Types

    1. Product layout

    2. Cellular Layouts

  22. A Group of Parts

  23. Process vs. Cellular Layouts

    1. Process Layout

    2. Cellular Manufacturing Layout

  24. Basic Layout Types

  1. Fixed-Position and combination Layout

  2. Service Layouts

  3. Design Product Layouts: Line Balancing

  4. Parallel Workstations

  5. The obstacle

  6. Cycle Time

    1. Determine Maximum Output Cycle Time: Time to process 1 unit

    2. Determine the Minimum Number of Workstations Required: Efficiency

  7. Percent Idle Time

  8. Example 1

    1. Precedence Diagram

    2. Assembly Line Balancing

    3. Solution to Example 1. Assigning operations by the number of followers

    4. Calculate Percent Idle Time

    5. Line Balancing Heuristic Rules

    6. Solution to Example 1. Assigning operations using their task times.

  9. Example 2

  10. Designing Process Layouts

  11. Example 3

    1. Locate 3 departments to 3 sites

    2. Designing Process Layouts

    3. Layout Alternative

    4. Closeness Rating: multiple criteria

    5. Muther Grid

 

  • Make or Buy?

    • Available capacity, excess capacity

    • Expertise, knowledge, know-how exists?

    • Quality Consideration, specialized firms, control over quality if in-house

    • The nature of demand, aggregation

    • Cost

Make some components buy remaining

  • Process selection

    • Deciding on the way production of goods or services will be organized

  • Major implications

    • Capacity planning

    • Layout of facilities

    • Equipment, Capital-equipment or labor intensive

    • Design of work systems

  • New product and service, technological changes, and competitive pressures

 

  • Job Shops: Small lots, low volume, general equipment, skilled workers, high-variety. Ex: tool and die shop, veterinarian’s office

  • Batch Processing: Moderate volume and variety. Variety among batches but not inside. Ex:paint production , BA3352 sections

  • Repetitive/Assembly: Semicontinuous, high volume of standardized items, limited variety. Ex: auto plants, cafeteria

  • Continuous Processing: Very high volume an no variety. Ex: steel mill, chemical plants
    Projects: Nonroutine jobs. Ex: preparing BA3352 midterm

4. Questions Before Selecting A Process

  • Variety of products and services

    • How much

  • Flexibility of the process; volume, mix, technology and design

    • What type and degree

  • Volume

    • Expected output

 

Dimension

Job Shop

Batch

Repetitive

Continuous

Job variety

Very High

Moderate

Low

Very low

Process flexibility

Very High

Moderate

Low

Very low

Unit cost

Very High

Moderate

Low

Very low

Volume of output

Very low

Low

High

Very high

 

Process Type

High variety

 
 

Low variety

Job Shop

Appliance repair Emergency room

 

 

 

 

 

Commercial bakery Classroom Lecture

 

 

 

 

 

Automotive assembly Automatic carwash

 

 

 

 

 

Oil refinery Water purification

 

 

  • Same type of machines together.

    • Functional lay out

    • Alternatively cellular production

  • Workers move products depending on needed processes.

Product Variety

High

Moderate

Low

Very Low

Equipment

flexibility

High

Moderate

Low

Very Low

Low

Volume

 Job
Shop

 

 

 

Moderate

Volume

 

 Batch

 

 

High

Volume

 

 

 Repetitive
assembly

 

Very high

Volume

 

 

 

 Continuous
Flow

 

  • Machinery that has sensing and control devices that enables it to operate

  • Fixed automation: Low production cost and high volume but with minimal variety and high changes cost

    • Assembly line

  • Programmable automation: Economically producing a wide variety of low volume products in small batches

    • Computer-aided design and manufacturing systems (CAD/CAM)

    • Numerically controlled (NC) machines / CNC

    • Industrial robots (arms)

  • Flexible automation: Require less changeover time and allow continuous operation of equipment and product variety

    • Manufacturing cell

    • Flexible manufacturing systems: Use of high automation to achieve repetitive process efficiency with job shop process

      • Automated retrieval and storage

      • Automated guided vehicles

    • Computer-integrated manufacturing (CIM)

 

Show wafer handler web

  • Group of machines that include supervisory computer control, automatic material handling, robots and other processing equipment

    • Advantage:

      • reduce labor costs and more consistent quality

      • lower capital investment and higher flexibility than hard automation

      • relative quick changeover time

    • Disadvantage

      • used for a family of products and require longer planning and development times

  • Use integrating computer system to link a broad range of manufacturing activities, including engineering design, purchasing, order processing and production planning and control

  • Advantage:

    rapid response to customer order and product change, reduce direct labor cost, high quality

  • Service blueprint: A method used in service design to describe and analyze a proposed service. Flowchart:

 

  • Establish boundaries

  • Identify steps involved

  • Prepare a flowchart

  • Identify potential failure points

  • Establish a time frame for operations

  • Analyze profitability

  • Layout: the configuration of departments, work centers, and equipment,

    • Whose design involves particular emphasis on movement of work (customers or materials) through the system

  • Importance of layout

    • Requires substantial investments of money and effort

    • Involves long-term commitments

    • Has significant impact on cost and efficiency of short-term operations

  • Inefficient operations

    For Example:

    • High Cost

    • Bottlenecks

  • Changes in the design of products or services

  • Changes in the design of products or services

  • Accidents Safety hazards

  • Changes in environmental or other legal requirements

  • Changes in methods and equipment

  • Changes in volume of output or mix of products

  • Morale problems

  • Product Layout

    • Layout that uses standardized processing operations to achieve smooth, rapid, high-volume flow

      • Auto plants, cafeterias

  • Process Layout

    • Layout that can handle varied processing requirements

      • Tool and die shops, university departments

  • Fixed Position Layout

    • Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed

      • Building projects, disabled patients at hospitals

  • Combination Layouts

Flow Shop or Assembly Line Work Flow

 

  • Advantage: more compact, increased communication facilitating team work, minimize the material handling

19. Basic Layout Types

Used for Intermittent processing

 

 

 

  • Job Shop
     

  • Project
     

  • Repetitive

Match?

  • Product
     

  • Process
     

  • Fixed-point

a. Product layout

  • Advantages

    • High volume

    • Low unit cost

    • Low labor skill needed

    • Low material handling

    • High efficiency and utilization

    • Simple routing and scheduling

    • Simple to track and control

  • Disadvantages

    • Lacks flexibility

      • Volume, design, mix

    • Boring for labor

      • Low motivation

      • Low worker enrichment

    • Can not accommodate partial shut downs/breakdowns

    • Individual incentive plans are not possible

b. Cellular Layouts

  • Cellular Manufacturing

    • Layout in which machines are grouped into a cell that can process items that have similar processing requirements. A product layout is visible inside each cell.

  • Group Technology

    • The grouping into part families of items with similar design or manufacturing characteristics. Each cell is assigned a family for production. This limits the production variability inside cells, hence allowing for a product layout.

 

 

Dimension

Process

Cellular

Number of moves between departments

many

few

Travel distances

longer

shorter

Travel paths

variable

fixed

Job waiting times

greater

shorter

Amount of work in process

higher

lower

Supervision difficulty

higher

lower

Scheduling complexity

higher

lower

Equipment utilization

Lower?

Higher?

 

a. Process Layout

 

b. Cellular Manufacturing Layout

 

  • Group Technology Layout

    Similar to cellular layout

 

  • Fixed Position Layout

    e.g. Shipbuilding

 

  • Fixed-Position Layout:
    item being worked on remains stationary, and workers, materials and equipment are moved as needed.

    • Example: buildings, dams, power plants

  • Combination Layouts:
    combination of three pure types.

    • Example: hospital: process and fixed position.

  • Warehouse and storage layouts
    Issue: Frequency of orders

  • Retail layouts
    Issue: Traffic patterns and traffic flows

  • Office layouts
    Issue: Information transfer, openness

  • Line balancing is the process of assigning tasks to workstations  in such a way that the workstations have approximately the same processing time requirements. This results in the minimized idle time along the line and high utilization of labor and equipment.

  • Each task takes 1 minutes, how to balance?

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

  • What is the cycle time for the system above?

 

  • The difficulty to forming task bundles that have the same duration.

  • The difference among the elemental task lengths can not be overcome by grouping task.

    • Ex: Can you split the tasks with task times {1,2,3,4} into two groups such that total task time in each group is the same?

    • Ex: Try the above question with {1,2,2,4}

  • A required technological sequence prohibit the desirable task combinations

    • Ex: Let the task times be {1,2,3,4} but suppose that the task with time 1 can only done after the task with time 4 is completed. Moreover task with time 3 can only done after the task with time 2 is completed. How to group?

  • The major determinant: cycle time

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

  • Minimum cycle time: longest task time by assigning each task to a workstation

  • Maximum cycle time: sum of the task time by assigning all tasks to a workstation

a. Determine Maximum Output Cycle Time: Time to process 1 unit

  • Example: If a student can answer a multiple choice question in 2 minutes but gets a test with 30 questions and is given only 30 minutes then
    OT=30 minutes; D=30

  • Desired cycle time=1 minute < 2 minutes = Cycle time from the process capability

b. Determine the Minimum Number of Workstations Required: Efficiency

  • Example: Students can answer a multiple choice question in 2 minutes but given a test with 30 questions and is given only 30 minutes. What is the minimum number of students to collaborate to answer all the questions in the exam?

  • Total operation (task) time = 60 minutes = 30 x 2 minutes
    Operating time=30 minutes
    60/3=2 students must collaborate. This Nmin below.

 

Efficiency = 1 – Percent idle time

a. Precedence Diagram

  • Precedence diagram: Tool used in line balancing to display elemental tasks and sequence requirements

b. Assembly Line Balancing

  • Arrange tasks shown in the previous slide into workstations.

    • Use a cycle time of 1.0 minute

      • Every 1 minute, 1 unit must be completed

    • Rule: Assign tasks in order of the most number of followers

      • If you are to choose between a and c, choose a

      • If you are to choose between b and d, choose b

      • Number of followers: a:3, b:2, c:2, d:1, e:0

  • Eligible task fits into the remaining time and all of its predecessors are assigned.

c. Solution to Example 1. Assigning operations by the number of followers

Work- Station

Time Remaining

Eligible

Assign Task

Station Idle Time

1

1.0

a,c

a

 
 

.9

c

c

 
 

.2

none

-

.2

2

1.0

b

b

 

 

0

none

-

0

3

1.0

d

d

 

 

.5

e

e

.3

 

.3

-

-

 
       

.5

  • Eligible operation fits into the remaining time and its predecessors are already assigned.

  • What is the minimum cycle time possible for this example?

d. Calculate Percent Idle Time

 

Efficiency=1-percent idle time=1-0.167=0.833=83.3%

e. Line Balancing Heuristic Rules

  • Assign tasks in order of most following tasks.

  • Assign task in the order of the greatest task time.

  • Assign tasks in order of greatest positional weight.

    • Positional weight is the sum of each task’s time and the times of all following tasks.

f. Solution to Example 1. Assigning operations using their task times.

 

Work- Station

Time Remaining

Eligible

Assign Task

Station Idle Time

1

1.0

a,c

a

 
 

.9

c

c

 
 

.2

none

-

.2

2

1.0

b

b

 

 

0

none

-

0

3

1.0

d

d

 

 

.5

e

e

.3

 

.3

-

-

 
       

.5

  • Eligible operation fits into the remaining time and its predecessors are already assigned.

Solution to Example 2

 

  • Requirements:

    • List of departments

      • Shape requirements

    • Projection of work flows

      • One way vs. two way: Packaging and final assembly.

    • Distance between locations

      • One way vs. two way: Conveyors, Elevators.

    • Amount of money to be invested

    • List of special considerations

      • Technical, Environmental requirements

  • Heuristic: assign critical departments first. The critical departments are those with X and A ratings.

  • Solution:

As

Xs

1-2

1-4

1-3

3-6

2-6

3-4

3-5

 

4-6

 

5-6

 

  • Begin with most frequently in the A list (6)

  • Add remaining As to the main cluster

  • Graphically portray Xs

  • Fit the cluster into the arrangement

 

1

2

6

3

5

4

 

 

a. Locate 3 departments to 3 sites

  • Distances in meters

From\To

A

B

C

A

-

20

40

B

20

-

30

C

40

30

-

  • Work Flow in kilos

From\To

1

2

3

1

-

10

80

2

20

-

30

3

90

70

-

  • Mutual flow

From\To

1

2

3

1

-

-

-

2

30

-

-

3

170

100

-

  • Closeness graph

 

b. Designing Process Layouts

  • Create Layout Alternatives

  • Find the one which minimizes transportation costs and distance traveled

c. Layout Alternative

Total Distance Traveled by Material=7600 m

 

c. Muther Grid

  • Allow multiple objectives and subjective input from analysis or manager to indicate the relative importance of each combination of department pairs.

  • Subjective inputs are imprecise and unreliable