Process Selection and

Facility Layout

Process types, process Process types, process selection and automationselection and automation

◦ Capacity planning

◦ Layout of facilities

◦ Equipment

◦ Design of work systems

The ways organizations choose to produce or

provide their goods and services. It involves choice of technology, type of

processing, and so on.

It influences

ProcessSelection

CapacityPlanning

Forecasting

WorkDesign

Product & service Design

Technological

Change

Layout

Facilities and

Equipment

Capacity is significantly impacted by process selection and facility layout.

Variety◦ How much

Flexibility◦ What degree

Volume◦ Expected output

Batch

Repetitive

Continuous

Job Shop

Project

Project:Project: A non-repetitive set of activities directed toward a unique goal within a limited time frame◦ Unique◦ Examples: Building a bridge, consulting

Job shop:Job shop: provides unit or lot production or service with changeable specifications, according to customer needs◦ Small scale◦ Examples: Machine shop, dentist’s office

Batch:Batch: Produces many different products in groups (batches)◦ Low or Moderate volume◦ Examples: Bakeries, movie theaters, classrooms

Repetitive:Repetitive: provides one or a few highly standardized

products or services

◦ High volumes of standardized goods or services

◦ Examples: automobiles, computers, cafeteria, car wash

Continuous:Continuous: produces highly uniform products or continuous

services, often performed by machines

◦ Very high volumes of non-discrete goods

◦ Examples: refineries, chemical plant, flour, sugar, electricity

supplying and the internet

Job Shop Batch Repetitive Continuous Projects

Cost estimation

Difficult Somewhat routine Routine Routine Simple to complex

Cost per unit High Moderate Low Low Very high

Equipment used

General purpose

General purpose Special purpose

Special purpose

Varied

Fixed costs Low Moderate High Very high Very high

Variable costs

High Moderate Low Very low High

Labor skills High Moderate Low Low to high Low to high

Marketing Promote capacities

Promote capacities; Semi-standard goods/ services

Promote standardized goods/ services

Promote standardized goods/ services

Promote capacities

Scheduling Complex Moderately complex

Routine Routine Complex, subject to change

Work-in-process inventory

High High Low Low Varied

Automation:Automation: Machinery that has sensing and control devices that enables it to operate automatically

Standardized goods and services

Examples:◦ Goods: Automobile factories, semiconductors◦ Services: Package sorting, e-mail, on-line banking

Fixed automation◦ Specialized equipment for a fixed sequence of operations

Programmable automation◦ Computer-aided design and manufacturing systems (CAD/CAM)◦ Numerically controlled (NC) machines: Machines that perform

operations by following mathematical processing instructions. ◦ Robot: A machine consisting of a mechanical arm, a power supply

and a controller

Flexible automation◦ Manufacturing cell◦ Flexible manufacturing systems◦ Computer-integrated manufacturing (CIM)

FMSFMS are more fully automated versions of cellular manufacturing: A computer controls the transfer of parts from machine to machine as well as the start of work at each machine

Produce a variety of similar products

Classification of production Classification of production systems and types of layoutssystems and types of layouts

The arrangement of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system.

Inefficient operations

For Example:High CostBottlenecks

Changes in the designof products or services

The introduction of newproducts or services

Accidents

Safety hazards

Changes inenvironmentalor other legalrequirements

Changes in volume ofoutput or mix of

products

Changes in methodsor equipment

Morale problems

Product Layouts most helpful to repetitive processing Process Layouts used for irregular processing Fixed-position layouts used when projects require layouts Hybrid layouts combinations of these above types

• Cellular manufacturing

• Group technology

• Flexible Manufacturing Systems

Product layout:Product layout: Layout that uses standardized processing operations to achieve smooth, fast, high-volume flow

Made possible by highly standardized goods or services that allow highly standardized, repetitive processing

The work is divided into a series of standardized tasks, permitting specialization of equipment and division of labor

The large volumes handled by these systems usually make it economical to invest substantial sums of money in equipment and in job design.

Raw materialsor customer

Finished item

Station 2

Station 2

Station 3

Station 3

Station 4

Station 4

Materials and/or labor

Materials and/or labor

Materials and/or labor

Materials and/or labor

Used for Repetitive or Continuous Processing

Example: automobile assembly lines, cafeteria serving line

Station 1

Station 1

1 2 3 4

5

6

78910

In

Out

Workers

High rate of output Low unit cost Labor specialization Low material handling cost High utilization of labor and equipment Established routing and scheduling Routine accounting, purchasing and inventory control

Creates boring, repetitive jobs Poorly skilled workers may not maintain equipment or

quality of output Fairly inflexible to changes in volume Highly inclined to shutdowns Needs preventive maintenance Individual incentive plans are impractical

Process layouts:Process layouts: Layouts that can handle various processing requirements

The layouts feature departments or other functional groupings in which similar kinds of activities are performed

Examples: Machine shops usually have separate departments for milling, grinding, drilling, and so on

Different products may present quite different processing requirements and sequences of operations

Process Layout - work travels to dedicated process centers

Milling

Assembly& Test Grinding

Drilling Plating

Can handle a variety of processing requirements Not particularly at risk to equipment failures Equipment used is less costly Possible to use individual incentive plans

In-process inventory costs can be high Challenging routing and scheduling Equipment utilization rates are low Material handling slow and inefficient Complexities often reduce span of supervision Special attention for each product or customer Accounting, inventory control and purchasing are

more involved

Fixed-Position Layout:Fixed-Position Layout: Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed

Examples:

◦Large construction projects (buildings, power plants, dams)

◦Shipbuilding, production of large aircraft◦Rockets used to launch space missions

The three basic layout types may be altered to satisfy the needs of a particular situation

Examples: ◦Supermarket layouts: primarily process layout, have

fixed-path material-handling devices as well (roller-type conveyors and belt-type conveyors)

◦Hospitals: process layout, fixed-position layout as well (patient care)

◦Off-line reworking (customized processing) of faulty parts in a product layout

Cellular Production◦Layout in which machines are grouped into a cell that

can process items that have similar processing requirements

Group Technology◦The grouping into part families of items with similar

design or manufacturing characteristicsDesign characteristics: size, shape and function.Manufacturing or processing characteristics: type

and sequence of operations required.

Line BalancingLine Balancing

Tasks are grouped into manageable bundles and assigned to workstations with one or two operators

Goal is to minimize idle time along the line, which leads to high utilization of labor and equipment

Perfect balance is often impossible to achieve

Line Balancing is the process of assigning tasks to workstations in such a way that the workstations have approximately equal time requirements.

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

With 5 workstations, CT =

0.5 min.1.0 min.0.7 min.0.1 min. 0.2 min.

1.0 minute.

Cycle time of a system = longest processing time in a workstation.

With 1 workstation, CT =

0.5 min.1.0 min.0.7 min.0.1 min. 0.2 min.

2.5 minutes.

0.5 min.1.0 min.0.7 min.0.1 min. 0.2 min.

Workstation 1 Workstation 2 Workstation 3

With 3 workstations, can CT = 1.0 minute?

Cycle time of workstation = total processing time in of tasks.

Output capacity = OTCT

OT = operating time per day

CT = cycle time

Example: 8 hours per day

OT = 8 x 60 = 480 minutes per day

Cycle Time = CT = 1.0 min

Output = OT/CT = 480/1.0 = 480 units per day

Cycle Time = CT = 2.5 min

Output = OT/CT = 480/2.5 = 192 units per day

Example: 8 hours per day

OT = 8 x 60 = 480 minutes per day

D = 480 units per day

CT = OT/D = 480/480 = 1.0 Minute

D = Desired output rate

CT = cycle time =OTD

Nmin = CT

t

t = sum of task times

Nmin = theoretical Minimum Number of

Workstations Required

Example: 8 hours per day, desired output rate is 480 units per day

CT = OT/D = 480/480 = 1.0 Minute

Nmin = ∑t /CT = 2.5/1.0 = 2.5 stations

≈ 3 stations

Designing Process Designing Process LayoutsLayouts

The main issue in design of process layouts concerns the

relative positioning of the departments involved.

Departments must be assigned to locations.

The problem is to develop a reasonably good layout; some

combinations will be more desirable than others.

Some departments may benefit from adjacent locations• Sharing expensive tools or equipments.

Some departments should be separated

• A lab with delicate equipment should not be located near a department that has equipment with strong vibrations.

• Sand blasting department and painting department.

• Flammable materials near a furnace.

One advantage of process layouts: satisfy a variety of processing requirements

Customers or materials in these systems require different operations and different sequences of operations

One of the major objectives in process layout is to minimize transportation cost, distance, or time

This is usually accomplished by locating departments with relatively high interdepartmental work flow as close together as possible