OM-07-ManufacturingProcessessLayout.ppt

8/10/2019 OM-07-ManufacturingProcessessLayout.ppt

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Manufacturing Processes and

Facility LayoutSelected Slides from Jacobs et al, 9thEdition

Operations and Supply Management

Chapter 7 and 7AEdited, Annotated and Supplemented by

Peter Jurkat


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Process Flow Structures

Job shop (ex. Copy center making a single copy of astudent term paper)

Batch shop (ex. Copy center making 10,000 copies ofan ad piece for a business)

Assembly Line (ex. Automobile manufacturer)

Continuous Flow (ex. Petroleum manufacturer)

7-2


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Product-Process Matrix

7-3

Project: fixed location

Work center: job shop

Continuous: glass,

paper, steel

Mass

Customization

Variety - high

Variety - low

Assembly Line:

automobile manufacturer


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Break-Even Analysis

A standard approach to choosing amongalternative processes or equipment

Model seeks to determine the point in units

produced (and sold) where total revenue andtotal cost are equal, or

Model seeks to determine the point in units

produced (and sold) where we will startmaking profit on the process or equipment

7-4


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Break-Even Analysis (Continued)

This formula can be used to find any of its

components algebraically if the otherparameters are known

Break-even Demand=

Purchase cost of process or equipment

Price per unit - Cost per unit

orTotal fixed costs of process or equipment

Unit price to customer - Variable costs per unit

7-5

See Ch07_BreakEvenAnalysis.xls now you do Problem 7.9 and

then Example 7.1 - try to match display on next page

Solution to: Revenue = Cost

Demand*Price = Fixed Cost + Demand*Variable Cost


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7-6

Example 7.1 page 207


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Manufacturing Process Flow Design

A process flow designcan be defined as amapping of the specific processes that rawmaterials, parts, and subassemblies follow asthey move through a plant

The most common tools to conduct a processflow design include assembly drawings,assembly charts, process flow diagrams

(operations), and route sheets

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7-8

Assembly Drawing


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Example: Assembly Chart (Gozinto)

A-2SA-2

4

5

6

7

Lockring

Spacer, detent spring

Rivets (2)

Spring-detent

A-5Component/Assy Operation

Inspection

From Exhibit 5.14

7-9


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Example: Process Flow Chart

Material

Received

from

Supplier

Inspect

Material for

Defects Defects

found?

Return to

Supplier for

Credit

Yes

No,

Continue

7-10


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Facility Layout

Facility layoutcan be defined as the process by which the placement ofdepartments, workgroups within departments, workstations,machines, and stock-holding points within a facility are determined

This process requires the following inputs:

Specification of objectives of the system in terms of output and

flexibility Estimation of product or service demand on the system

Processing requirements in terms of number of operations and amountof flow between departments and work centers

Space requirements for the elements in the layout

Space availability within the facility itself

Each process type (project, job shop, cell, assembly line, continuous)has it corresponding basic layout

Determine the best layout (one that minimizes flow*distance, orflow*unit flow cost, , maximizes throughput, )

7A-11


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7A-12

The Assignment Problem

Assign each departments to one of the 8 rooms so as to minimize the cost of required flows

Cost measured in (number of moves)*distanceor timeor $ cost of move

Can be done by exhaustive enumeration; prohibitive for large problems

All commercial software uses heuristicsSee Ch07A_Process_Layout.xls


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Process Layout: Systematic Layout Planning

Minimizing cost of numerical flow of itemsbetween work centers

Can be impractical to obtain - cannot guaranteemathematical optimum

Does not account for the qualitative factors that

may be crucial to the placement decision

Systematic Layout Planning

Accounts for the importance of having eachdepartment located next to every other

departmentrating factors Is also guided by trial and error

Switching work centers then checking the results of thecloseness score

7A-13

7A 14


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Example of Systematic Layout Planning: Reasons for Closeness

Code

1

2

3

4

5

6

Reason

Type of customer

Ease of supervision

Common personnel

Contact necessary

Share same price

Psychology

7A-14

7A 15


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Example of Systematic Layout Planning:

Importance of Closeness

Rating scale, symbols, and weights

Value

A

E

I

O

U

X

ClosenessLine

code

Numerical

weights

Absolutely necessary

Especially important

Important

Ordinary closeness OK

Unimportant

Undesirable

16

8

4

2

0

-80

7A-15

7A 16


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Example of Systematic Layout Planning:

Initial Relationship Diagram

1

2

4

3

5

U U

E

A

I

The number of lines

here represent paths

required to be taken in

transactions between

the departments. The

more lines, the more

the interaction betweendepartments.

Note here again, Depts. (1) and(2) are linked together, and

Depts. (2) and (5) are linked

together by multiple lines or

required transactions.

7A-16

7A 17


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Now you do 7A.8

Example of Systematic Layout Planning:Initial and Final Layouts

3

2 4

1

5

Initial LayoutIgnoring space andbuilding constraints

2

5 1 43

50 ft

20 ft

Final LayoutAdjusted by square

footage and building

size

Note in the

Final Layout

that Depts.

(1) and (5)are both

placed

directly next

to Dept. (2).

7A-17

1

2

4

3

5

U U

E

A

I


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Assembly Line

Layout not a problemits obviously a line with sequentialwork stationscan be straight, curved, double back, ..

Tasks along line and at each station must satisfyprecedence relationships

A line is balanced if the entire line moves at same speed

and all tasks at all stations get done with no slacknotonly nearly impossible but not completely desirable

Time at each station is workstation cycle time

Assembly line balancing is to arrange tasks at each station

so they can be done during the cycle time with minimumidle time

Work time at each station is sum of task times (or longestsequence of task times at station if parallel tasks)

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Example of Line Balancing:

Precedence and Task Times Diagram

7A-19

A

C

B

D E F

G H

2

3.25

1

1.2 .5

11.4

1

Total tasktimes =

11.35

Task C

determines

cycle time

Parallel work

can be done

on one line

Task Precedents Time (mins)

A None 2

B A 1

C None 3.25

D A, C 1.2

E D .5

F E 1

G B 1

H F, G 1.4

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Example of Line Balancing: Determine Cycle Time

Required Cycle Time, C =

Production time per period

Required output per period

C =420 mins / day

100 units / day= 4.2 mins / unit

Question: Suppose we want to assemble 100 fans per day.What would our cycle time and number of workstationshave to be?

7A-20

Theoretical Min. Number of Workstations,N

N =Sum of task times (T)

Cycle time (C)

t

t

N =11.35 mins / unit

4.2 mins / unit= 2.702, or 3t

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Example of Line Balancing: Rules To Follow for Loading Workstations

Assign tasks to station 1, then 2, etc. in sequence.Keep assigning to a workstation ensuring thatprecedence is maintained and total work is lessthan or equal to the cycle time. Use the following

rules to select tasks for assignment.

Primary:Assign tasks in order of the largestnumber of following tasks

Secondary (tie-breaking):Assign tasks in order ofthe longest operating time

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7A-22


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A

C

B

D E F

GH

2

3.25

1

1.2 .5

1

1.4

1

A(4.2-2=2.2)

B(2.2-1=1.2)

G(1.2-1= .2)

Idle= .2

Task Followers Time (Mins)

A 6 2

C 4 3.25

D 3 1.2

B 2 1

E 2 0.5

F 1 1

G 1 1

H 0 1.4

Station 1 Station 2 Station 3

7A 22

Sort table by number of followers:

Cycle time = 4.2

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C(4.2-3.25)=.95

Idle = .95

A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1


A 6 2

C 4 3.25

D 3 1.2

B 2 1E 2 0.5

F 1 1

G 1 1

H 0 1.4

A(4.2-2=2.2)

B (2.2-1=1.2)

G(1.2-1= .2)

Idle= .2


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Cycle time = 4.2

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A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1

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

H(1.5-1.4)=.1

Idle = .1


A 6 2

C 4 3.25

D 3 1.2

B 2 1E 2 0.5

F 1 1

G 1 1

H 0 1.4

A(4.2-2=2.2)

B(2.2-1=1.2)

G(1.2-1= .2)

Idle= .2


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

7A 24

Now you do 7A.4

Cycle time = 4.2

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Example of Line Balancing: Determine the Efficiency of the Assembly Line

Efficiency =Sum of task times (T)

Actual number of workstations (Na) x Cycle time (C)

Efficiency =

11.35 mins / unit

(3)(4.2mins / unit) =.901

Actually efficiency = 11.35/(3*4.1) = .923

but may not want to run this tight.

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Manufacturing Cell:

Transition from Process Layout

1. Grouping parts into families that follow acommon sequence of steps

2. Identifying dominant flow patterns ofparts families as a basis for location orrelocation of processes

3. Physically grouping machines andprocesses into cells

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7A-28


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Project Layout

Question: What are our primary

considerations for a project layout?

Answer: Arranging materials and equipment

concentrically around the production point in their

order of use.

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Retail Service Layout

Goal--maximize net profit per square foot

of floor space

Servicescapes

Ambient Conditions

Spatial Layout and Functionality

Signs, Symbols, and Artifacts

7A-30


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Retail Layout for Visibility

Customer never sees

more than four aisles

Customer never sees less than

four aisles and can see as many

as six in some locations

Enhanced by having low counters

in center and high along walls

Documents

OM-07-ManufacturingProcessessLayout.ppt