Chapter 5, Part B

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Facility Layout: Manufacturing and Services

Chapter 5, Part B

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Facility Layout

Facility layout means planning: for the location of all machines, utilities, employee

workstations, customer service areas, material storage areas, aisles, restrooms, lunchrooms, internal walls, offices, and computer rooms

for the flow patterns of materials and people around, into, and within buildings

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Locate All Areas In and Around Buildings

Equipment Work stations Material storage Rest/break areas Utilities Eating areas Aisles Offices

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Characteristics of the Facility Layout Decision

Location of these various areas impacts the flow through the system.

The layout can affect productivity and costs generated by the system.

Layout alternatives are limited by the amount and type of space required for the

various areas the amount and type of space available the operations strategy

. . . more

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Characteristics of the Facility Layout Decision

Layout decisions tend to be: Infrequent Expensive to implement Studied and evaluated extensively Long-term commitments

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Manufacturing Facility Layouts

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Materials Handling

The central focus of most manufacturing layouts is to minimize the cost of processing, transporting, and storing materials throughout the production system.

Materials used in manufacturing include: Raw material Purchased components Work-in-progress Finished goods Packaging material Maintenance, repair, and operating supplies

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Materials Handling

A materials-handling system is the entire network of transportation that:

Receives material Stores material in inventories Moves material between processing points Deposits the finished products into vehicles for

delivery to customers

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Materials Handling

Material-Handling Principles Move directly (no zigzagging/backtracking) Minimize human effort required Move heavy/bulky items the shortest distances Minimize number of times same item is moved MH systems should be flexible Mobile equipment should carry full loads

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Materials Handling

Material-Handling Equipment Automatic transfer devices Containers/pallets/hand carts Conveyors Cranes Elevators Pipelines Turntables AGVS

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Basic Layout Forms

Process Product Cellular Fixed-Position Hybrid

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Process (Job Shop) Layouts

Equipment that perform similar processes are grouped together

Used when the operations system must handle a wide variety of products in relatively small volumes (i.e., flexibility is necessary)

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Characteristics of Process Layouts

General-purpose equipment is used Changeover is rapid Material flow is intermittent Material handling equipment is flexible Operators are highly skilled . . . more

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Characteristics of Process Layouts

Technical supervision is required Planning, scheduling and controlling functions are

challenging Production time is relatively long In-process inventory is relatively high

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Product (Assembly Line) Layouts

Operations are arranged in the sequence required to make the product

Used when the operations system must handle a narrow variety of products in relatively high volumes

Operations and personnel are dedicated to producing one or a small number of products

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Characteristics of Product Layouts

Special-purpose equipment are used Changeover is expensive and lengthy Material flow approaches continuous Material handling equipment is fixed Operators need not be as skilled . . . more

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Characteristics of Product Layouts

Little direct supervision is required Planning, scheduling and controlling functions are

relatively straight-forward Production time for a unit is relatively short In-process inventory is relatively low

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Cellular Manufacturing Layouts

Operations required to produce a particular family (group) of parts are arranged in the sequence required to make that family

Used when the operations system must handle a moderate variety of products in moderate volumes

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Characteristics of Cellular ManufacturingRelative to Process Layouts

Equipment can be less general-purpose Material handling costs are reduced Training periods for operators are shortened In-process inventory is lower Parts can be made faster and shipped more quickly

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Characteristics of Cellular ManufacturingRelative to Product Layouts

Equipment can be less special-purpose Changeovers are simplified Production is easier to automate

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Fixed-Position Layouts

Product remains in a fixed position, and the personnel, material and equipment come to it

Used when the product is very bulky, large, heavy or fragile

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Hybrid Layouts

Actually, most manufacturing facilities use a combination of layout types.

An example of a hybrid layout is where departments are arranged according to the types of processes but the products flow through on a product layout.

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New Trends in Manufacturing Layouts

Designed for quality Designed for flexibility - to quickly shift to different

product models or to different production rates Cellular layout within larger process layouts Automated material handling U-shaped production lines . . . more

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New Trends in Manufacturing Layouts

More open work areas with fewer walls, partitions, or other obstacles

Smaller and more compact factory layouts Less space provided for storage of inventories

throughout the layout

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Planning Manufacturing Facility Layouts

Two Categories of Software Tools Computer aided design (CAD)

Allows 3-D, full-color views of facility design Allows virtual walk-throughs Ex. – ArchiCAD, AutoSketch, AutoCAD

Computer simulation Can simulate proposed system layout in operation

and measure its performance Ex. – ProModel, VisFactory, SIMPROCESS

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Process and Warehouse Layouts Product Layouts Cellular Manufacturing Layouts


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Process Layouts Primary focus is on the efficient flow of materials The wide variety of potential product routings

through the facility can be evaluated using computer simulation

Warehouse Layouts Primary focus is the fast storage and retrieval of

inventory items Decisions about aisle size/placement and location

of each inventory item can be evaluated using computer simulation

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Product Layouts Primary focus is on the analysis of production lines The goal of the production line analysis is to:

Determine how many workstations to have Determine which tasks to assign to which

workstation Minimize the number of workers & machines used Provide the required amount of capacity

Line balancing is a key part of the analysis

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Planning Product Layouts

Line Balancing Procedure1. Determine the tasks involved in completing 1 unit2. Determine the order in which tasks must be done3. Draw a precedence diagram4. Estimate task times5. Calculate the cycle time6. Calculate the minimum number of workstations7. Use a heuristic to assign tasks to workstations

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Line Balancing Heuristics Heuristic methods, based on simple rules, have been

developed to provide good (not optimal) solutions to line balancing problems

Heuristic methods include: Incremental utilization (IU) method Longest-task-time (LTT) method … and many others

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Incremental Utilization Method Add tasks to a workstation in order of task

precedence one at a time until utilization is 100% or is observed to fall

Then the above procedure is repeated at the next workstation for the remaining tasks

Pro – Appropriate when one or more task times is equal to or greater than the cycle time

Con – Might create the need for extra equipment

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Longest-Task-Time Method Adds tasks to a workstation one at a time in the order

of task precedence. If two or more tasks tie for order of precedence, the

one with the longest task time is added Conditions for its use:

No task time can be greater than the cycle time There can be no duplicate workstations

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Example: Armstrong Pumps

Line BalancingArmstrong produces bicycle tire pumps on a

production line. The time to perform the 6 tasks in producing a pump and their immediate predecessor tasks are shown on the next slide.

Ten pumps per hour must be produced and 45 minutes per hour are productive.

Use the incremental utilization heuristic to combine the tasks into workstations in order to minimize idle time.

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Line Balancing Tasks that Time toImmediately Perform

Task Precede Task (min.) A -- 5.4

B A 3.2 C -- 1.5 D B,C 2.8 E D 17.1 F E 12.8

Total = 42.8

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Line Balancing – Network (Precedence) Diagram

A

C

B ED F

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Line Balancing – Cycle Time

= 45/10 = 4.5 minutes per pump

Productive Time per HourCycle Time = Demand per Hour

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Line Balancing – Minimum Number of Workstations

Minimum Number ofWorkstations

= [(42.8)(10)]/45 = 9.51 workstations

(Total Task Time)(Demand per Hour)= Productive Time per Hour

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Line Balancing – Incremental Utilization HeuristicWS Tasks Mins./pump #WS’s

Incr.Util. 1 A 5.4 5.4/4.5=1.2= 2

60.0% 1 A,B 5.4 + 3.2 8.6/4.5=1.9= 2

95.0% 1 A,B,C 8.6 + 1.5 10.1/4.5=2.2= 3

49.8% 2 C 1.5 1.5/4.5=.33= 1

33.3% 2 C,D 1.5 + 2.8 4.3/4.5=.96= 1

95.6% 2 C,D,E 4.3 + 17.1 21.4/4.5=4.8= 5

95.1% 3 E 17.1 17.1/4.5=3.8= 4

95.0% 3 E,F 17.1 + 12.8 29.9/4.5=6.6= 7

94.9% 4 F 12.8 12.8/4.5=2.8= 3

94.8%

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Line Balancing – Utilization of Production Line

= 9.51/10 = .951 = 95.1%

Minimum Number of WorkstationsUtilization = Actual Number of Workstations

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Rebalancing a Production Line Changes that can lead to production lines being out of

balance or having insufficient/excess capacity are: Changes in demand Machine modifications Variations in employee learning and training

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Planning Cellular Manufacturing Layouts

Cell Formation Decision Which machines are assigned to manufacturing

cells Which parts will be produced in each cell

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Fundamental Requirements for Parts to be Made in Cells

Demand for the parts must be high enough and stable enough that moderate batch sizes of the parts can be produced periodically.

Parts must be capable of being grouped into parts families.

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More-Complex Issues to be Resolved If all the parts cannot be cleanly divided between

cells, how will we decide which are to be the exceptional parts?

If inadequate capacity is available to produce all the parts in cells, which parts should be made outside the cells?

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Cell Formation Procedure1. Form the Parts-Machines Matrix.2. Rearrange the Rows.

Place the machines that produce the same parts in adjacent rows.

3. Rearrange the Columns. Place the parts requiring the same machines in

adjacent columns.4. Use the rearranged parts-machines matrix to identify

cells, the machines for that cell and the parts that will be produced in that cell.

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Chapter 5, Part B