process selection and facility layout

Process Selection and Facility Layout

• Process selection– Deciding on the way production of goods or

services will be organized

• Major implications– Capacity planning– Layout of facilities– Equipment – Design of work systems

Introduction

Forecasting

Product andService Design

TechnologicalChange

CapacityPlanning

ProcessSelection

Facilities andEquipment

Layout

WorkDesign

Process Selection and System DesignInputs Outputs

Key aspects of process strategy– Capital intensive – equipment/labor– Process flexibility– Adjust to changes

– Design– Volume– Technology

Process Strategy

• Variety– How much

• Flexibility– What degree

• Volume – Expected output Job Shop

Batch

Repetitive

Continuous

Process Selection

Process types

• Job shop– Small scale, wide variety of goods

• Batch– Moderate volume, flexible

• Repetitive or assembly line– High volumes of standardized goods or services

• Continuous– Very high volumes of non-discrete goods

• Projects– Nonroutine work, uniqe set ob objectives, limited

timeframe and resources

Process types and volume

Product – Process Matrix

The diagonal of the matrix represents the ideal choice of processing system for a given sets of circumstances.

Functions/activities affected by process choice

Job variety, process flexibility, unit cost

Volume

Limited(not ongoing)

Product and service life cycles

• Alongside the life cycle the sales and with it the producion volume can change.

• So managers must be aware of the change in the optimal processing system. (the necessity of change is highly dependent on the particular good or service)

Product/Service Profilig

• Linking key product or service requirements to process capavilities.

• Design the process with taking into consideration the following:– Range of products/services– Expected order size– Pricing– Expected frequency of changes in schedules etc.– Order-winning requirements– …

Sustainable production

• Non-polluting• Conserving natural resources & energy• Economically efficient• Safe and healthful for workers, communities

and consumers• Socially and creaqtively rewarding for workers

• Automation: Machinery that has sensing and control devices that enables it to operate– Fixed automation– Programmable automation

Automation of production and services

Advantages of automation

• Low variability in performance and quality• Machines do not

– get bored or distracted– go out on strike or ask for higher wages– lower variable costs

Disadvantages

• Higher initial (investment) cost and • Higher fixed costs• Lower felxibility• Higher skills needed• Lower morale of human workforce• Need for standardisation

– Products– Processes– Equipment and materials etc.

• Computer-aided design and manufacturing systems (CAD/CAM)

• Numerically controlled (NC) machines • Computerized numerical control (CNC)• Direct numerical control (DNC)

• Robot: mechanical arm + power supply + controller• Manufacturing cell• Flexible manufacturing systems (FMS)• Computer-integrated manufacturing (CIM)

Automation

• Layout: the configuration of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system

Facilities Layout

• Requires substantial investments of money and effort

• Involves long-term commitments• Has significant impact on cost and

efficiency of short-term operations

Importance of Layout Decisions

The Need for Layout Decisions

• Inefficient operations• High (variable) Cost• Bottlenecks

• Changes in the design of products or services• The introduction of new products or services• Safety• Changes in environmental or other legal

requirements• Changes in volume of output or mix of products• Changes in methods and equipment• Morale problems

Objectives of facility layout

Main: smooth flow of work, material and information

Supporting objectives:

• Product layouts

• Process layouts

• Fixed-Position layout

Hybrid types:

• Combination layouts

Basic Layout Types

• Product layout – Layout that uses standardized processing

operations to achieve smooth, rapid, high-volume flow

• Process layout– Layout that can handle varied processing

requirements• Fixed Position layout

– Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed

Basic Layout Types

Used for Repetitive or Continuous Processing

Product Layout

• High rate of output• Low unit cost• Labor specialization• Low material handling cost• High utilization of labor and equipment• Established routing and scheduling• Routing accounting and purchasing

Advantages of Product Layout

• Creates dull, repetitive jobs• Poorly skilled workers may not maintain

equipment or quality of output• Fairly inflexible to changes in volume• Highly susceptible to shutdowns• Needs preventive maintenance• Individual incentive plans are impractical

Disadvantages of Product Layout

A U-Shaped Production Line

Advantages/disadvantages of U-shaped lines

• Shorter distances for workers & machines

• Permits communication thus facilitates teamwork

• More flexible work assignments

• Optimal is the facility has the same entry and exit point

• If lines are highly automated, there is no need for communication and travel

• If entry points are on the opposite side as exit points

• Noise and contamination factors are increased in the U-shape

Dept. A

Dept. B Dept. D

Dept. C

Dept. F

Dept. E

Used for Intermittent processingJob Shop or Batch

Process Layout(functional)

Process Layout

Work Station 1

Work Station 2

Work Station 3

Product Layout(sequential)

Used for Repetitive ProcessingRepetitive or Continuous

Product Layout

• Can handle a variety of processing requirements

• Not particularly vulnerable to equipment failures

• Equipment used is less costly• Possible to use individual incentive plans

Advantages of Process Layouts

• 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 and purchasing are more involved

Disadvantages of Process Layouts

Fixed-position layouts

• The product or project remains stationary and workers, materials, and equipment are moved as needed.

• If weight, size, bulk, or some other factor makes it undesirable or extremely difficult to move the product.

• E.g. firefighting, road-building, home-building, drilling for oil etc.

• 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 characteristics– Makes cellular production much more effective

Cellular Layouts

Traditional process layout

Cellular layout

Dimension Functional CellularNumber of moves between departments

many few

Travel distances longer shorter

Travel paths variable fixed

Job waiting times greater shorter

Throughput time higher lower

Amount of work in process

higher lower

Supervision difficulty higher lower

Scheduling complexity higher lower

Equipment utilization lower higher

Functional vs. Cellular Layouts

• Use of flexible manufacturing systems

Service layouts• Warehouse and storage layouts

– Minimizing movement & picking time and cost

• Retail layouts– Presence & influence of customers

• Office layouts:– Information is computerized, image of openness

Other Solutions & Service Layouts

Design Product Layouts: Line Balancing

Line Balancing is the process of assigning tasks to workstations in such a way that the workstations have approximately equal time requirements.This way the idle time will be minimized, utilization will be maximized

Specialzation: dividing work into elematal tasks that can be performed quickly and routinely

Cycle Time

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

tmax < Cycle time < ∑t

Determine the Minimum Number of Workstations Required

A diagram that shows elemental tasks and their precedence requirements.

A Simple Precedence Diagrama b

c d e

0.1 min.

0.7 min.

1.0 min.

0.5 min. 0.2 min.

Precedence Diagram

Assume that the desired output is 480 units per day. The facility is workint 8 hours a day. The elemental tasks and their connections are shown in the previous slide.

• Calculate the cycle time.• Calculate the minimum number of workstations.• Arrange the tasks into these workstations in the

order of the greatest number of following tasks.

Example 1: Assembly Line Balancing

WorkstationTimeRemaining Eligible

AssignTask

RevisedTime Remaining

StationIdle Time

1 1.0

0.9

0.2

a, c *

c **

none***

a

c

-

0.9

0.2

0.2

2 1.0 b b 0.0 0.0

3 1.0

0.5

0.3

d

e

-

d

e

-

0.5

0.3 0.3

Total: 0.5

Example 1 Solution

* Tasks that have no predecessors.** b is not eligible, because it needs more time than than the remaining.*** Every available task needs more time than 0.2.

Efficiency = 1 – Percent idle time

Calculate Percent Idle Time and efficiency

Line balancing procedure

• Assign tasks in order of most following tasks.– Count the number of tasks that follow

• Assign tasks in order of task time.

• Assign tasks in order of greatest positional weight. – Positional weight is the sum of each task’s time

and the times of all following tasks.

Line Balancing Heuristics

Example 2

Working day is 8 hours and the desired output rate is 400 units per day.

Draw the precedence diagram.Compute the cycle time & the minimum number of workstations required.Assign tasks to workstations according to the greatest number of following tasks. Tiebreaker: longest processing time goes first.Calculate Percent idle time & efficiency.

Other approaches

• Paralell workstations• Cross-train workers (dynamic line balancing)• Mixed model line

(more product on the same line)

1 min.2 min.1 min.1 min. 30/hr. 30/hr. 30/hr. 30/hr.

1 min.

1 min.

1 min.1 min. 60/hr.

30/hr. 30/hr.

60/hr.

1 min.

30/hr.30/hr.

Bottleneck

Parallel Workstations

Parallel Workstations

Thank you for your attention