facility layout - lecture notes

Facility Layout

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Section Objectives

After completing this section, you should be able to:

1. List some of the different reasons for redesign of layouts.

2. Identify the inputs to facility layout decisions.

3. Distinguish between the four basic types of facility layouts.

4. List the primary advantages and limitations of both product and process layout.

5. Develop appropriate process layouts.

6. Solve line balancing problems.

7. Describe new layout approaches.

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Facility LayoutThe optimum placement or arrangement of space-consuming components within a productive system. The space-consuming components are:

machines materials manpower

The benefits of a good layout include: smooth material flow reduced inventories better scheduling effective space utilization fewer production bottlenecks reduced material handling costs

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Inputs to Facility Layout

1. Output (product / service) design - product or service design affects the layout of a facility. Design issues that have to be considered include:

Dimensions / weights of components Perishability / obsolescence Customer interaction requirements

2. Capacity Design - capacity design affects layout by determining the: output rate and output flexibility, and the level of capital intensity

3. Process Design - the way a product or service is produced will influence layout. Design issues include the:

Sequence of processing operations for each output Processing equipment required for each operation Floor space requirements for equipment Inventory storage requirements for raw materials, work-in-progress,

and finished goods

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4. Facility Location - the current site: what flexibility does it have in terms of: Size and configuration Expansion options

5. Job Design - the tasks that constitute work, and the activities necessary to complete the tasks. These influence:

Work station operations and output Work station layout

6. Support Services - these are resources that support the primary production functions. They include:

Maintenance, supervision, employee facilities Loading docks, storage, aisles, elevators

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General Classification of LayoutsProduct (Flow Shop) Layout

The physical components are arranged according to the progressive stages by which the product / service is provided. e.g. assembly lines, cafeterias. Layout built around a product that seeks the best personnel and machine utilization through repetitive or continuous production.

Process (Job Shop) Layout

The physical components are arranged, or grouped, according to the general function they perform, without regard to specific products / services provided. e.g. metal fabricators, hospitals, cafeterias. A layout that deals with low-volume, high-variety production.

Fixed-Position Layout

The product, because of its bulk or weight, remains in one location. All physical components are moved to the location where the product is being produced. e.g. shipyards, buildings. Layout that address the requirements of stationary projects or large, bulky projects.

Group Technology Layout

Dissimilar machines are grouped into work centres in order to work on products with similar shapes and processing requirements. e.g. aircraft manufacturing. It is basically a hybrid product / process layout.

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Job Shop vs. Group Technology Layout

LL L

L L L

M M M

M M M

G G G

G G G

D D D

DDD

Lathe Work Centre Milling machines

Drill pressesGrinding work centre

WorkFlow

Inputs

WorkFlow

Output

G

M

L

D

L

LD

D ML

D

D

L

L

WorkFlow

Inputs

WorkFlow

Output

JobShop

GroupTechnology

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Characteristics of Product and Process Layouts

Characteristics Product Layout Process LayoutWork Flow Fixed VariableOutput Mix Small, standard VariableOutput Volume High Moderate / lowInventories: Raw materials High Low Work-in-progress Low High Finished goods High LowFloor Space Utilization High LowCapital Costs High LowMaterials Handling Mechanized Labour intensiveOutput Costs: Fixed costs High Low Direct labour Low High Direct materials Variable High

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Innovations at McDonald’s

Indoor seating (1950s) Drive-through window (1970s) Adding breakfast to the menu (1980s) Adding play areas (1990s)

Three out of the four are layout decisions!

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Fifth major innovation Sandwiches assembled in order

Elimination of some steps, shortening of others

No food prepared ahead except patty

New bun toasting machine and new bun formulation

Repositioning condiment containers

Savings of $100,000,000 per year in food costs

McDonald’s New Kitchen Layout

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McDonald’s NewKitchen Layout

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Objectives for Facility Layouts

Objectives for Manufacturing Operation Layouts Provide enough productive capacity Reduce materials-handling costs Conform to site and building constraints Allow space for production machines Allow high labour, machine and space utilization and productivity Provide for volume and product flexibility Provide space for restrooms, cafeterias and other personal-care

needs Provide for employee safety and health Allow ease of supervision Allow ease of maintenance Control capital investment

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Additional Objectives for Warehouse Operation Layouts Promote efficient loading and unloading of shipping vehicles Provide for effective stock picking, order filing and unit loading Allow ease of inventory counts Promote accurate inventory recordkeeping

Additional Objectives for Service Operation Layouts Provide for customer comfort and convenience Provide an appealing setting for customers Allow an attractive display of merchandise Reduce travel of personnel or customers Provide for privacy in work areas Promote communication between work areas Provide for stock rotation for shelf life

Additional Objectives for Office Operation Layouts Reinforce organization structure Reduce travel of personnel or customers Provide for privacy in work areas Promote communication between work areas

Objectives for Facility Layouts - continued

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Supermarket Retail Layout

Objective is to maximize profitability per square foot of floor space

Sales and profitability vary directly with customer exposure

Five Helpful Ideas for Supermarket Layout1. Locate high-draw items around the periphery of the store

2. Use prominent locations for high-impulse and high-margin items

3. Distribute power items to both sides of an aisle and disperse them to increase viewing of other items

4. Use end-aisle locations

5. Convey mission of store through careful positioning of lead-off department

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Supermarket Retail Layout

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Product Layout for a Bread Bakery

Milling

Mixing

Baking

Cutting

Packaging

Raw Material

Bread

Note thelogical

sequence ofoperations

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Process Layout for a Hospital

Admissions

GeneralWard

IntensiveCare

X-Ray

Surgery

Laboratory

Kitchen

Emergency

Maternity Ward

Labour Room

Delivery Room

Children's Ward

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Process Layouts: It’s All About FlowsResource Flows of Importance:

1. Manufacturing systems - material flows2. Administrative offices - personnel flows3. Hospital flows - patient, staff flows4. Postal service - customer, mail flows5. Restaurants - customer, staff flows

Advantages of Process Layouts:1. Systems can handle a variety of processing requirements.2. System not vulnerable to equipment failure.3. General-purpose equipment is less costly than the specialized

equipment used in product layouts and is easier to maintain.4. Possible to use individual incentive systems.

Disadvantages of Process Layouts:1. In-process inventory costs are high.2. Routing and scheduling are difficult.

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3. Equipment utilization rates are low.4. Material handling is slow and inefficient and more costly per unit than

under product layouts.5. Job complexities often reduce the span of supervision and result in

higher supervisory costs than product layouts do.6. Special attention for each product or customer (routing, scheduling,

machine setups, and so on) and low volumes result in higher unit costs than with product layouts.

7. Accounting, inventory control and purchasing are much more involved than under product layouts.

Designing Process Layouts

Main issue in the design of process layouts concerns the relative positioning of the departments involved. Process layouts features:

1. Some departments benefit from adjacent locations.2. Some departments must be kept separate.3. External factors such as the location of entrances, loading docks,

elevators, windows, and areas of reinforced flooring have to be considered.

4. Flow costs for material and personnel within the building are critical.

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Steps for Process LayoutStep 1: Construct a “from-to-matrix showing the flow of parts or materials from

department to department.

Step 2: Determine the space requirements for each department.

Step 3: Develop an initial schematic diagram showing the sequence of departments through which parts will have to move. Try to place departments with a heavy flow of materials or parts next to one another.

Step 4: Determine the cost of this layout by using the following equation:

Minimize cost = XijCij

where: n = number of work centres or departments

i,j = individual departments

Xij = number of moves between department i and department j

Cij = cost of a move between department i and department j

Step 5: Try to improve this layout by trial and error or by use of a computer program.

Step 6: Prepare a detailed plan considering space or size requirements of each department.

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1 2 3 4 5 6 7 8

175 25 0 30 200 20 25 0 100 75 90 80 90 17 88 125 99 180 20 5 0 25 0 180 187 374 103 7

Flows Between Departments

(number of moves)

12345678

12345678

Department

Shipping & receivingPlastic molding & stamping

Metal formingSewing departmentSmall toy assemblyLarge toy assembly

PaintingMechanism assembly

Activity

1

2

3 5 7

4 6 8

160 ‘

80 ‘

Step 1

Step 240’ 40’ 40’ 40’

40’ 40’ 40’ 40’

40’ 40’ 40’ 40’

40’ 40’ 40’ 40’

Process Layout Illustration - Minimizing Flow Costs for a Toy Company

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1 2 3 4 5 6 7 8

175 25 0 60 400 60 75 0 100 150 180 240 270 17 88 125 198 360 20 5 0 50 0 180 187 374 103 7

12345678

Cost Matrix - First SolutionAssume flow cost = 1 for adjacent movesAssume flow cost = 2 for moves over 1 deptAssume flow cost = 3 for moves over 2 depts (Assume diagonal moves are possible)

Sample Calculations: 1 to 2 = 175 x 1 = 175 1 to 6 = 200 x 2 = 400 1 to 8 = 25 x 3 = 75, etc.

Total cost = $3,449

Step 4

Step 31 3 5

2 4 6

25 88

20020

100 5

175


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4 3 5 7

2 1 6 8

Revised LayoutExchange 1 & 4

Why 1 & 4? Youwant to bring 1 and6 next to each other,and this is one way

to do it!

Costs affected:1&5, 1&6, 1&7,1&8, 4&5, 4&6,

4&7, 4&8

1 2 3 4 5 6 7 8

175 50 0 30 200 40 50 0 100 150 180 240 270 17 88 125 198 360 40 10 0 75 0 180 187 374 103 7

12345678

Cost Matrix - Second SolutionCost reductions:

1&5 = 30, 1&6 = 2001&7 = 20, 1&8 = 25

Cost additions:4&5 = 20, 4&6 = 54&7 = 0, 4&8 = 25

Total cost = $3,234

Step 5


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Small ToyAssembly

5

MechanismAssembly

8

Shipping andReceiving

1

Large ToyAssembly

6

MetalForming

3

Plastic Mldg. / Assb.

2

Sewing

4

Painting

7

A final,feasiblesolution

after severaliterations

Step 6


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Process Layout Illustration - Systematic Layout PlanningEven though the approach of minimizing flow costs is widely used, it suffers from the limitation of being able to focus on only one objective, and many situations involve multiple criteria.

A more general approach, systematic layout planning (SLP), allows for subjective input from analysts or managers to indicate the relative importance of each combination of department pairs.

The following is an example of SLP for the floor of a department store:

From

1. Credit dept

2. Toy dept.

3. Wine dept.

4. Camera dept.

5. Candy dept.

To 2 3 4 5 I U A U 6 --- 1,6 ---

U I A --- 1 1,6

A E 2,3 1

X 1

Area (sq. ft.)

100

400

300

100

100

Letter

Number

Closeness Rating

Reason for Rating

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Reason

Type of customer

Ease of supervision

Common personnel

Contact necessary

Share same space

Psychology

Code

1

2

3

4

5

6

5 2 4

13

Initial layout based upon relationship requirements

(ignoring space and building constraints)

2 4

3 15

20 ft.

50 ft.

Final layout adjustedby square footageand building size

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Product LayoutThese are layouts used to achieve a smooth and rapid flow of large volumes of products or customers through a system. The main characteristics of product layouts:

Standardized products requiring standardized processing

Job divided into a series of tasks

Specialization of labour and equipment

Substantial investment in equipment and in job design

Each item follows the same sequence of operations

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Station# 1

Station# 2

Station# 3

Station# 4

Work flow

EndBegin

Materialsand/or labour




Product Layout: The Assembly Line

OMFloorAnimationOMFloor

Animation

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Main Advantages of Product Layouts1. High rate of output2. Low unit costs as fixed costs of specialized equipment spread over

many units.3. Labour specialization reduces training costs and time.4. High utilization of labour and equipment.5. Routing and scheduling are included in the initial design of system

and do not require much attention once the system is in operation.6. Accounting, purchasing and inventory control are fairly routine.

Primary Disadvantages of Product Layouts1. Division of labour usually creates dull, repetitive jobs with little

opportunity for advancement and may lead to morale problems.2. System is inflexible in response to changes in volume of output or

changes in product or process design.3. System is susceptible to shutdowns caused by equipment

breakdowns or employee absenteeism.4. Preventative maintenance, the capacity for quick repairs and spare

parts inventories are necessary expenses.

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Steps in Product LayoutStep 1: Develop the precedence diagram showing the sequence and performance times for each task.

Step 2: Calculate cycle time to meet the output requirement. Take the demand per day and divide it into the productive time available per day (in minutes or seconds).

productive time

Demand per day or production rate per day

Step 3: Determine the theoretical minimum number of workstations. This is the sum of all task times divided by the cycle time. Fractions are rounded to the next higher whole number.

time for task i

Cycle time

Step 4: Perform the line balance by assign specific assembly tasks to each workstation. An efficient balance is one that will complete the required assembly, follow the specified sequence, and keep the idle time at each workstation to a minimum.

Cycle time =

Minimum number of workstations =

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1. Longest operating task time

Choose the available task with the longest task time

2. Greatest number of following tasks

Choose the available task with the largest number of following tasks

3. Ranked positional weight Choose the available task for which the sum of following task times is the longest

4. Shortest operating task time

Choose the available task with the shortest task time

5. Least number of following tasks

Choose the available task with the least number of following tasks

Line-Balancing Heuristics (Rules of Thumb)

Rule Meaning

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The problem: Pproduce 500 Model J Wagons per 8-hour day Setup time and work breaks total 45 minutes Production time available = 480 – 45 = 435 minutes Assembly steps and times for the Model J Wagon are given below:

ABCDEFGHIJK

Position rear axle support and hand fasten 4 screws to nutsInsert rear axle

Tighten rear axle support screws to nutsPosition front axle assembly and hand fasten with 4 screws to nuts

Tighten front axle assembly screwsPosition rear wheel #1 and fasten hub capPosition rear wheel #2 and fasten hub capPosition front wheel #1 and fasten hub capPosition front wheel #2 and fasten hub cap

Position wagon handle shaft on front axle assembly and fasten bolt and nutTighten bolt and nut

TimeTask Task Description

4511950151212121289

195

AA,B

DA,B,CA,B,CD,ED,E

A,B,C,D,E,F,G,H,IJ

Tasks ThatMust Precede

Assembly Line Balancing Illustration

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A

B C

F

G

D E H

I

J K

Step 1: Draw the precedence diagram

45

11 9

50 15

12

12

12

12

8 9


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Step 2: Calculate the cycle time

Cycle Time = time available / output required

= 435 minutes / 500 units = 0.87 minutes = 52.2 seconds

Step 3: Calculate the minimum number of workstations

Minimum number of work stations = total task time / cycle time

= 195 seconds / 52.2 seconds = 3.74 = 4 stations

Step 4: Balance the line using the following heuristics (rules of thumb):

1. According to Greatest-Number-of-Following-Tasks rule

2. According to the Longest-Operating-Time rule


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Station 1

Station 2

Station 3

Station 4

Station 5

A

D

B/E/C/F

G/H/I/J

K

45

50

11/15/9/12

12/12/12/8

9

7.2

2.2

41.2/26.2/17.2/5.2

40.2/28.2/16.2/8.2

43.2

None

None

C,E/C,H,I/F,G,H,I/None

H,I/I/J/None

None

C,E/C/F,G,H,I

H,I

Workstation Task Task Time Idle TimeFeasible Remaining

TasksTasks With

Most Followers

Step 4: Balancing the line using the Greatest-Number-of-Following-Tasks rule:


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Station 1

Station 2

Station 3

Station 4

D

A

E/H/I/B

C/F/G/J/K

50

45

15/12/12/11

9/12/12/8/9

2.2

7.2

37.2/25.2/13.2/2.2

43.2/31.2/19.2/11.2/3.2

None

None

H,I,B/I,B/B/None

F,G/G/J/K

E/H/I/B

C/F/G/J/K

Workstation Task Task Time Idle TimeFeasible Remaining

TasksTasks With Longest

Operating Time

Efficiency of the line = total task time / (number of stations * cycle time):

Step 4: Balancing the line using the Longest-Operating-Time rule:

Efficiency of line balance using the greatest-number-of-following-tasks rule= 195 / (5 x 52.2) = .747 = 74.7%

Efficiency of the line using the longest -operating-time rule= 195 / (4 x 52.2) = .934 = 93.4%


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Production Lines: Western vs. Japanese

Western

1. Top priority: line balance 2. Strategy: stability - long production runs. Rebalancing seldom occurs 3. Assume fixed labour assignments 4. Use inventory buffers to cushion effect of equipment failure 5. Plan to run at fixed rate:. Send quality problems off line 6. Linear or L-shaped lines 7. Material movement by conveyor is desirable 8. Buy “supermachines” and keep them busy on a continuous basis 9. Applied in labour-intensive final assembly10. Run mixed models where labour content is similar from model to model

Japanese

1. Top priority: flexibility 2. Strategy: flexibility - expect to rebalance often to match output to changing demand 3. Flexible labour: move to current workload 4. Employ maximal preventive maintenance to keep equipment from breaking down 5. Slow for quality problems: speed up when quality is right 6. U-shaped or parallel lines 7. Put stations close together and avoid conveyors 8. Install small machines: add more as needed 9. Applied even to capital-intensive subassembly10. Strive for mixed-model production, even in subassembly and fabrication

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Characteristics of Japanese Manufacturing Layouts

Chief Objective: Manufacturing flexibility to give the ability to modify production rates quickly and to change to different models.

Means of Achieving Objective:1. Workers trained at many jobs.

2. Large investment in preventative maintenance.

3. Workers encouraged to solve production problems as they arise.

4. Workers and machines shifted as needed to solve production problems.

5. Production lines stopped or slowed when machine breakdowns or quality problems occur.

6. Little inventory carried.

7. Work stations placed close together.

Appearance of Layouts:1. Small manufacturing floor plans.

2. Compact and tightly packed layouts.

3. Large percentage of floor space utilized for production.

4. U-shaped production lines.

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Process Layout - Additional Illustration # 1

A small printing shop wishes to locate its seven departments in a one-floor building that is 40 unitswide and 50 units long. Department sizes are :

Department Length (units) Width (units)Layout 10 10Cutting 20 10Shipping 10 10Supply Storage 20 15Printing 25 20Binding 20 20Art 20 20

The average number of loads flowing between departments is expected to be:

From Dept Layout Cutting Shipping Supply Storage Painting Binding ArtLayout --- --- --- --- --- --- ---Cutting --- --- --- 100 --- 400 ---Shipping --- --- --- 500 --- --- ---Supply Storage --- 600 100 --- 400 100 ---Printing --- --- --- --- --- 1200 100Binding --- 100 1000 --- 200 --- ---Art --- 100 --- --- 100 --- ---

What is your layout recommendation?

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Eight work centres must be arranged in an L-shaped building. The location of centres A and E are designated as shown in the accompanying diagram. Assuming transportation costs are $2 per load per metre, develop a suitable layout that minimizes transportation costs using the information below.

From / To A B C D E F G H A -- 40 40 60 120 80 100 110 B -- 60 40 60 140 120 130 C -- 45 85 40 70 90 D -- 40 50 40 45 E -- 90 50 40 F -- 40 60 G -- 60 H --

A * B

C D E *

F G H

From / To A B C D E F G H A -- 10 5 90 365 135 125 0 B 0 -- 140 10 0 35 0 120 C 0 220 -- 110 10 0 0 200 D 0 110 240 -- 10 0 0 170 E 5 40 100 180 -- 10 40 10 F 0 80 40 70 0 -- 10 20 G 0 45 20 50 0 40 -- 20 H 0 0 0 20 0 0 0 --

Loads per day

* cannot be moved

Distances (metres)

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Hercules Manufacturing, a producer of corrugated cardboard boxes, is planning a 3600 square foot layout. The operations manager has obtained SLP ratings for locating departments next to each other.

From / To Storage Corrugator Folder/Gluer Taper/Bailer Inspection ShippingStorage --- AN U U I U Corrugator --- --- I U U XFolder/Gluer --- --- --- AN I UTaper/Bailer --- --- --- --- U IInspection --- --- --- --- --- AN Shipping --- --- --- --- --- ---

AN = Absolutely Necessary I = Important U = Unimportant X = Undesirable

Area(sq.ft.)1200400400400400800

What should be the layout used by Hercules Manufacturing?

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Product Layout - Additional Illustration # 1

Rival Manufacturing Company, a producer of can openers, has to balance its assembly line. Given below are the work elements, their times and their precedence requirements:

Work Element Time (sec.) Precedence A 30 -- B 60 A C 70 A D 50 A E 20 A

F 40 A,B,C G 50 A,C

H 50 A,B,C,D,E,F,G

370

Demand per day is 400 can openers. Working time per day is 8 hours.

a. Draw the precedence diagram.b. What is the theoretical number of work stations?c. What is the minimum number of work stations needed to achieve a cycle time of 70 seconds,

using the greatest-number-of-following-tasks rule?d. What is the minimum number of stations needed to meet a cycle time of 100 seconds, according

to the longest-operating-time rule?e. What are the balance delays in parts (c) and (d) ?

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Product Layout - Additional Illustration # 2

Able Manufacturing has an opportunity to bid on a contract to produce an electronic assembly. Ablecould use excess assembly capacity at its main production facility. The contract would require (over two years) of 30,000 units. Able’s engineers suggest an assembly line consisting of nine tasks:

Work Element Time (min) Must Follow A 4 G B 6 G

C 2 B,D D 5 A,F E 3 D F 4 GG 3 I

H 2 C,E I 4 ---

Assembly would occur on one shift with average productive time of 7.5 hours per employee daily. There would be twenty-two productive days per month on average. Direct labour costs are $11 per hour; variable overhead is estimated at 10 percent of direct labour; direct materials are $18 per unit; initial tooling for the project is $150,000 and semifixed costs of manufacturing for the assembly lineare estimated at $8,000 per month. Able would like a 15 percent margin on selling price for such a contract. Should Able submit a bid and, if so, at what price?

facility layout - lecture notes

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