Assembly Line.ppt

8/11/2019 Assembly Line.ppt

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Chapter 10Facility Layout

Operations Managementby

R. Dan Reid & Nada R. Sanders3rdEdition Wiley 2007


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Learning Objectives Define layout planning and its importance

Identify and describe different types of

layouts Compare process layouts & product layouts

Describe the steps involved in designingboth process and product layouts

Explain the advantages of hybrid layouts

Define the meaning of group technology &its importance to cellular layouts


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What Is Layout Planning Layout planning is determining the best physical

arrangement of resources within a facility

Facility resource arrangement can significantly affectproductivity.

Two broad categories of operations:

Intermittent processing systemslow volume of many different

products

Continuous processing systemshigh volume of a few

standardized products


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Facility Layout Fixed Position

Product is too large to move;

e.g.: a building

Process Group similar resources together

Product

Designed to produce a specific product efficiently

Hybrid: combines aspects of both process andproduct layouts

Cellular

Modular


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Fixed Position Layout The position of a product or customer is

fixed; and materials, equipment, workers,

and other resources are transported to andfrom the product or customer.

Usually used because product movement is

difficult (ship building) or for convenience(on-site repair).

This is often managed through Project

Management (Chapter 16).


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Process Layout Similar processes/functions are grouped

together (job shop). Volume ofparts/services does not warrant product orcellular layout.

Primary advantages--flexibility, utilizationof machinery/equipment.

Disadvantages--greater handling ofmaterials/customers, more complexscheduling, WIP/waiting lines,

departmental boundaries


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Traditional Process Layout


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Process Layouts General purpose & flexible resources

Lower capital intensity & automation

Higher labor intensity

Resources have greater flexibility

Processing rates are slower

Material handling costs are higher

Scheduling resources & work flow is morecomplex

Space requirements are higher


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Designing Process Layouts Step 1: Gather information:

Space needed, space available, importance ofproximity between various units

Step 2: Develop alternative block plans:

Using trial-and-error or decision support tools

Step 3: Develop a detailed layout

Consider exact sizes and shapes of departments andwork centers including aisles and stairways

Tools like drawings, 3-D models, and CAD softwareare available to facilitate this process


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Comparing Alternatives Load-distance measures

Load: # of trips, weight moved, $-value moved

Distance: rectilinear distance (using north-south &east-west movements)

REL charts:

Management opinion on strength of relationships

Software tools: CRAFT: computerized relative allocation of facilities

technique

ALDEP: automated layout design program


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Process Layout Example


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Process Layout Steps Step 1: Gather information like space needed, from-to

matrix, and REL Chart for Recovery First Sports MedicineClinic(total space 3750 sq. ft.)

A

Radiology

400 sq. ft.

B

Laboratory

300 sq. ft.

C

Lobby &Waiting

300 sq. ft.

D

ExaminingRooms

800 sq. ft.

E

Surgery &Recovery

900 sq. ft.

F

PhysicalTherapy

1050 sq. ft.


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Step 1: Gather Information(continued)


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Step 2: Develop a Block Layout Use trial and error with from-to and REL

Charts as a guide

Use computer software like ALDEP orCRAFT


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Warehouse Layouts Warehouse Layout Considerations:

Primary decision is where to locate each departmentrelative to the dock

Departments can be organized to minimizeldtotals

Departments of unequal size require modification ofthe typical ld calculationsto include a calculation oftheratio of trips to area needed

The usage ofCrossdocking(see Ch.4) modifiesthe traditional warehouse layouts; more docks, lessstorage space, and less order picking


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Office Layouts Office Layout Considerations:

Almost half of US workforce works in an officeenvironment

Human interaction and communication are the primaryfactors in designing office layouts

Layouts need to account for physical environment andpsychological needs of the organization

One key layout trade-off is between proximity andprivacy

Open concept offices promote understanding & trust

Flexible layouts incorporating office landscapinghelp to solve the privacy issue in open office

environments


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Product Layout

Processes/work stations arranged insequence of activities required to producethe product/service (Assembly Line). Use for high volume, standardized products and

services

WIP and handling of materials/customers is

minimized Equipment is specialized, capital intensive

Output is dependent on the slowest workstation

The line must be balanced for effectiveness.


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Product Layouts

Specialized equipment

High capital intensity & wide use of

automation Processing rates are faster

Material handling costs are lower

Less space required for inventories

Less volume or design flexibility


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ProductLayout

Product

A

Product

B

Product

C

Step 1

Step 1

Step 1

Step 2

Step 2

Step 2

Step 3

Step 3

Step 3

Step 4

Step 4

Step 4

7-14


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Designing Product Layouts

Step 1:Identify tasks & immediate predecessors

Step 2:Determine the desired output rate

Step 3:Calculate the cycle time Step 4:Compute the theoretical minimum

number

of workstations

Step 5:Assign tasks to workstations (balance the

line)

Step 6:Compute efficiency, idle time & balance

delay


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Assembly Line Balancing

1. Precedence diagram: circles=tasks, arrows showthe required sequence.

2. Determine cycle time:

3. Determine required workstations (theoreticalminimum)

4. Set rules for assigning tasks (number of following

tasks, longest task time)

unitput)/time_demand(out

/time_unitproduction

D

PC

cycle_time

task_times

C

TN

t


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Assembly Line Balancing

5. Assign tasks to first workstation, usingrules and staying within cycle time.Repeat for following workstations until alltasks are assigned.

6. Evaluate line efficiency:

7. Rebalance if efficiency is not satisfactory.

kstationsactual_worN;CN

T

E aa


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Example 10.4 Vicki's Pizzeria and the Precedence Diagram

Immediate Task TimeWork Element Task Description Predecessor (seconds

A Roll dough None 50

B Place on cardboard backing A 5

C Sprinkle cheese B 25D Spread Sauce C 15

E Add pepperoni D 12

F Add sausage D 10

G Add mushrooms D 15H Shrinkwrap pizza E,F,G 18

I Pack in box H 15

Total task time 165


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Layout Calculations

Step 2:Determine output rate

Vicki needs to produce 60 pizzas per hour

Step 3:Determine cycle time

The amount of time each workstation is allowed tocomplete its tasks

Limited by the bottleneck task (the longest task in aprocess):

sec./uni60units/hr60

sec/min60xmin/hr60

units/hroutputdesired

sec./daytimeavailable)(sec./unittimeCycle

hourperpizzasorunits/hr,72sec./unit50

sec./hr.3600

timetaskbottleneck

timeavailableoutputMaximum


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Layout Calculations (continued)

Step 4:Compute the theoretical minimumnumber of stations

TM = number of stations needed to achieve

100% efficiency (every second is used)

Always round up (no partial workstations)

Serves as a lower bound for our analysis

stations3or2.75,

nsec/statio60

seconds165

timecycle

timestaskTM


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Layout Calculations (continued) Step 5:Assign tasks to workstations

Start at the first station & choose the longest eligible taskfollowingprecedence relationships

Continue adding the longest eligible task that fits without going over the

desired cycle time When no additional tasks can be added within the desired cycle time,

begin assigning tasks to the next workstation until finished

Workstation Eligible task Task Selected Task time Idle time

A A 50 10

B B 5 5C C 25 35

D D 15 20

E, F, G G 15 5

E, F E 12 48

F F 10 38

H H 18 20I I 15 5

1

2

3


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Last Layout Calculation

Step 6:Compute efficiency and balance delay

Efficiency (%) is the ratio of total productivetime divided by total time

Balance delay (%) is the amount by which the

line falls short of 100%

91.7%100sec.60xstations3

sec.165

NC

t(%)Efficiency

8.3%91.7%100%delayBalance


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Other Product Layout Considerations

Shape of the line (S, U, O, L): Share resources, enhance communication &

visibility, impact location of loading &

unloading

Paced versus un-paced lines Paced lines use an automatically enforced

cycle time Number of products produced

Single

Mixed-model lines


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Comparison of Product vs. Product Layouts

Process Layouts Product LayoutsProducts: large #, different small # efficiently

Resources: general purpose specialized

Facilities: more labor intensive more capital intensive

Flexibility: greater relative to market lower relative to market

Processing slower fasterRates:

Handling costs: high low

Space requirements: higher lower


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Hybrid Layouts

Combine elements of both product &process layouts

Maintain some of the efficiencies ofproduct layouts

Maintain some of the flexibility ofprocess layouts

Examples: Group technology & manufacturing cells

Grocery stores


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Hybrid Layouts

Cellular Layout Cross between product/process layout

group a number of machines into a cell toproduce a family of parts requiring similarprocessing (group technology).

Often arranged into U- or C-shaped line flows

Modular Layout achieves layout flexibility so that layouts can

be changed, expanded, or reduced withoutmuch difficulty.


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Designing Hybrid Layouts One of the most popular hybrid layouts uses Group

Technology (GT) and a cellular layout

GT has the advantage of bringing theefficiencies of aproductlayout to aprocess layout environment


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Process Flows before the Use of GT Cells


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Process Flows after the Use of GT Cells


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Facility Layout Across theOrganization

Layout planning is organizationallyimportant for an efficient operations

Marketing is affected by layout especiallywhen clients come to the site

Human resources is affected as layoutimpacts people

Finance is involved as layout changes can becostly endeavors


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Chapter 10 Highlights

Layout planning is deciding on the best physicalarrangement of resources.

There are four basic types of layouts: process,product, hybrid, and fixed position.

Process layouts provide flexibility to make avariety of different products. Product layouts

provide greater efficiency for one product. The steps for designing process layouts are:

gather space and closeness information, developa block plan, and develop a detailed layout.


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Chapter 10 Highlights (continued)

The steps for designing an product layout are:identify tasks and predecessors, determineoutput rate, determine cycle time, computing the

theoretical minimum number of work stations,assigning tasks to workstations, and computingefficiency and balance delay.

Hybrids layouts combine elements from bothtypes of layouts to increase efficiency.

Hybrid layouts combine GT analysis with cellularlayout concepts .


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Chapter 10 Homework Hints

10.8: Assign sites based on number oftrips (refer to Example 10.2). There is no

strategy regarding which side of the aisleto assignjust nearness to the dock.

10.16: Follow the steps. This is a product

layout (assembly line balancing). Thebook has an example on pages 360-366,which is also on the slides covered in class.


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Sample Problem10.7

dock aisle

Department Category Trips to/fromdock

1 Sports t-shirts 50

2 Mens t-shirts 633 Womens t-shirts 35

4 Childrens t-shirts 55

5 Fashion t-shirts 48

6 Undershirts 60


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Sample Problem10.15

Draw precedence diagram Determine cycle timedemand = 50 units/hr

Theoretical minimum no. of work stations

Assign tasks to workstations using cycle time

Efficiency and balance delay of line?

Bottleneck?

M i t t?

Task Imm. predecessor Task time (sec)

A None 55

B A 30

C A 22

D B 35

E B, C 50

F C 15

G F 5

H G 10

TOTAL 222

Assembly Line.ppt

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