Ch09-Charting & Diagramming(2)

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Work Systems and the Methods, Measurement, and Management of Work

by Mikell P. Groover, ISBN 0-13-140650-7.

©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Charting and Diagramming

Chapter 9

Techniques for Operations Analysis






Objectives of Charts and Diagrams

Used in Methods Engineering

1. To permit work processes to be communicated andcomprehended more readily

2. To use algorithms specifically designed for the particular

diagramming technique

3. To divide a given work process into its elements for

analysis purposes

4. To provide a structure in the search for improvements

5. To represent a proposed new work process or method






How to Create / Develop the Chart or

Diagram?

Analyst is intimately familiar with the process anddevelops a graphic to represent it

Analyst observes and records information about theprocess

One-on-one interviews with those familiar with theprocess A graphic model of the process is developed based on

these interviews

Group meetings with personnel familiar with process The analyst records the discussion of the meeting. A graphic model of the process is developed based on the

group meetings






How to Analyze the Chart or Diagram

Algorithmic analysis Line balancing, critical path methods

Checklists General questions applied to the particular process to

assess whether they can be applied to the problem of

interest

Brainstorming Team activity in which participants contribute

recommendations

Separating value-added and non-value-added operations Value added steps:

1. Important to customer

2. Physically change the product or service






Checklist of Questions - Example

What alternative starting material could be used?

Should the part be produced or purchased?

Can this operation be eliminated, combined, or simplified?

Could a different joining method be used?

Could the inspection task be automated?






Categories of Charts and Diagrams

1. Network diagrams

2. Traditional industrial engineering charts anddiagrams

Operation charts Process charts

Flow diagrams

Activity charts

1. Block diagrams and process maps

2. Gantt charts






Network Diagrams

Consist of: Nodes representing operations, work elements, activities or other

entities Arrows connecting the nodes indicates relationships among the

nodes Direction of work flow between nodes Precedence among nodes

Used to represent Work elements in assembly line balancing Work activities in CPM and PERT

Two-way flows (movement of materials):

Maximum number of arrows = n(n -1)

One-way arrows (precedence):Maximum number of arrows =

( )

2

1−nn






Network Diagram - Precedence Constraints

Restrictions on the order in which workelements can be performed

Precedence

diagram






Traditional IE Charts and Diagrams

Operation charts

Process charts

Flow diagrams

Activity charts






Operation Charts

Graphical and symbolic representation of the operations usedto produce a product

The time to accomplish the operation is sometimes alsoincluded.

Two types of operations:

1. Processing and assembly operations Changing the shape, properties or surface of a

material or workpart Joining two or more parts to form an assembly

1. Inspection operations Checking the material, workpart, or assembly for

quality or quantity











Operation Chart

Subassembly

Component






Checklist of Questions Used to Analyze an

Operation Chart

The focus of the operation chart is on the materials of a productand the operations on them

Questions related to material What alternative starting material could be used? Make or buy decision: should the part be produced in the

factory or purchased?

Questions related to operations Is this processing operation necessary? Can this operation be eliminated, combined, or simplified? Could a different joining method be used?

Questions related to inspection Is this inspection necessary? Could the inspection task be automated?






Operation Charts






Process Charts

Graphical and symbolic representation of the processingactivities performed either on something or by somebody.

The chart consists of a vertical list of activities using symbolsto represent operations, inspections, moves, delays andstorage and other activities.

Principal types of process charts:1. Flow process chart – analysis of a material or workpiece being

processed

2. Worker process chart – analysis of a worker performing a task

3. Form process chart – analysis of the processing of paperworkforms

All these charts are used to examine for possibleimprovements of operations






Flow Process Chart

Uses five symbols to detail the work performedon a material or workpart as it is processed

through a sequence of operations and activities:

Operation – processing of a material

Inspection – check for quality or quantity

Move – transport of material to new location

Delay – material waiting to be processed or

moved

Storage – material kept in protected location








SYMBOLS USED IN FLOW

PROCESS CHART









Flow Process Charts

If the processing operation combined with an inspectionat the same workstation: combine symbols - a circle

inside a square

Provides more detail about the steps required to process

a material than in the operation chart:

is used to study a single work part rather than the

multiple components of an assembly

The chart also indicates distances for move activitiesand time values for other activities






Form for Flow Process Chart






Checklist of Questions Used to Analyze a

Flow Process Chart

Questions Related to Material Make or buy decisions: Should the part be produced in the factory or

purchased from an outside vendor?

Questions Related to Operations and Inspections Is the operation time too high? Is the inspection operation necessary?

Questions Related to Moves How can moves be shortened or eliminated by combining or eliminating

operations? Can the level of mechanization in material handling be increased?

Questions Related to Delays Is the delay avoidable?

What is the reason for the delay? Can the reason be eliminated?

Questions Related to Storage Is the storage necessary? Why can’t the material be move immediately to the next operation?




by Mikell P. Groover, ISBN 0-13-140650-7.©2007 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Flow Process Chart

Unplann

ed vs.Plannedstoppag

e





Flow Process Chart





Worker Process Charts

Used to analyze the activities of a humanworker as (s)he performs a task that requires

movement around a facility.

Also known as process chart-person analysis

The symbols are the same as flow process chart Storage activity is omitted since it is difficult to

interpret in the context of human work activity





Form Process Charts

Used to analyze the flow of paperwork formsand office procedures





Flow Diagram

Drawing of the facility layout with the addition of linesrepresenting movement of materials or workers within

the facility

Arrows on the lines represent direction of movement

Often used in conjunction with a process chart

Operations, inspections, delays, and storages at specific

locations are identified by numbers referenced to the

activity number





Flow Diagram

The flow diagram reveals problems in the work flow thatmay not readily be identified using the process chart

alone.

For example, if the work flow involves considerable

backtracting, this can be identified in the flow diagram,whereas it is indicated only as distances in the process

chart.

Thus, it can be used to detect excessive backtracking

(which might be missed in a process chart), excessivetravel, possible traffic congestion, points where delays

typically occur and inefficient layout.





Flow Diagram

Flow diagram for worker

setting up a milling

machine:

Note the large number of

trips back and forth

between the millingmachine and the tool crib





Activity Charts

A listing of the activities of one or more subjects (e.g.,workers, machines) plotted against a time scale to

indicate graphically how much time is spent on each

activity

These activities are generally repetitive.

Types of activity charts:

Right-hand/left-hand activity chart (a.k.a. workplace activity

chart)

Worker-machine activity chart

Worker-multimachine activity chart

Gang activity chart (a.k.a. multiworker activity chart)





Shading Formats for Activity Charts

Instead of using symbols for the work activities, as in the other charts, the activities are indicated by vertical lines or bars

When bars are used, they are shaded or colored to indicate

the kind of the activity being performed.





Activity Chart

Activity charts usually have more than one time scalee.g., activity time and cumulative time

Activity chart for a worker performing a repetitive task:





Multiple-Activity Charts

Used to track several participants workingtogether

They consists of multiple columns, one for each

participant.

Objective: to analyze how the workload iscoordinated and shared among the entities. Right-hand/left-hand activity chart

Worker-machine activity chart

Worker-multimachine activity chart

Gang activity chart (a.k.a. multiworker activity chart)





Right-Hand/Left-Hand Activity Chart

Shows contributions of the right and left hands

balance of the workload between the right and lefthands

Remember the example with pegs

Task involves placing pegs into a peg board

Note that left hand is used as a workholder





Worker-Machine Activity Chart

Shows how work elements are allocatedbetween a worker and a machine

Help to identify opportunities for cycle time

improvements e.g., replacement of externalwork elements by internal work elements





Worker-Multimachine Activity Chart

Can be used to indicate machine interference(when a machine must wait for service because

worker is currently servicing another machine)





Gang Activity Chart

This chart indicates activities in which two or more workers performing together as a team

Also known as multiworker activity chart

Can be used to analyze the operations of different stations in the the same chart

Objective: To better coordinate the activities andbalance the workload among the workers





Block Diagrams

Graphic consisting mostly of blocks and arrowsto portray the relationships among components

of a physical system

Commonly used in linear control theory, where Arrows represent the flow of signals or variables in

the system

Blocks contain transfer functions that define how

input signals are mathematically transformed into

output signals





Block Diagram

AC AB

x y

Input Output

+

==

11

•Used to depict flows and interrelationshipsamong components in complex systems

•Block diagrams are commonly used in linear

control theory, as shown below for a feedback

control system

31323312ACx Ax x Ax xCx x x −==−= ,





Process Maps

A process is a sequence of tasks that add value to inputsto produce outputs

Basic process map is a block diagram showing the steps

in a process

Widely applied to business processes

Also applicable to production, logistics, and serviceoperations

Levels of detail:

High-level process map – macroscopic view of

process and includes only the most important steps

Low-level process map – used to map each of the

steps in a high-level process map





Symbols in the Basic Process Map

Process map symbols:

(a) beginning/ending point of the process,

(b) task or activity step,

(c) decision point

Symbols are connected by arrows to indicate

sequence





Basic Process Map





Alternative Forms of Process Maps

Relationship process map – block diagram thatshows the input-output connections among

departments (or other functional components) of

an organization

Cross-functional process map – block diagramshowing how the steps of a process are

accomplished by various departments

Departments listed as rows separated by

dashed lines Also called a swim-lane chart





Relationship Map

Block diagram that shows the input-outputconnections among departments (or other

functional components) of an organization





Cross-Functional Process Map

Block diagram showing how the steps of aprocess are accomplished by departments





Gantt Charts

A graphical display of schedule project activitieson a time axis

Project activities are listed on a vertical axis

Activity time durations are shown as horizontal

bars with starting and ending times





Gantt Chart: Planned Activities

Shows planned activities for a construction project





Gantt Chart: Progress

Shows actual work accomplished at some pointduring week 7





Gantt Chart Showing Precedence

Arrows can be used to indicate precedencerelationships among activities

Documents

Ch09-Charting & Diagramming(2)