objectives of charts and diagrams charting and diagramming ... · checklists general questions...

1

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

Sections:

1. Overview of Charting and Diagramming Techniques

2. Network Diagrams

3. Traditional Engineering Charting and Diagramming Techniques

4. Block Diagrams and Process Maps

Gantt Charts ?

Chapter 9

Techniques for Operations Analysis




Objectives of Charts and Diagrams

Used in Methods Engineering

1. To permit work processes to be communicated and

comprehended 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 and develops a graphic to represent it

� Analyst observes and records information about the process

� One-on-one interviews with those familiar with the process� 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 and diagrams� Operation charts

� Process charts

� Flow diagrams

� Activity charts

3. Block diagrams and process maps

4. Gantt charts

2




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 work

elements 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 used to produce a product

� The time to accomplish the operation is sometimes also included.

� 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

2. Inspection operations

� Checking the material, workpart, or assembly for quality or quantity







Operation Chart

Subassembly

Component

3




Checklist of Questions Used to Analyze an

Operation Chart

� The focus of the operation chart is on the materials of a product and 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 processing activities performed either on something or by somebody.

� The chart consists of a vertical list of activities using symbols to represent operations, inspections, moves, delays and storage 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 paperwork forms

� All these charts are used to examine for possible improvements of operations




Flow Process Chart

� Uses five symbols to detail the work performed

on 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







Flow Process Charts

� If the processing operation combined with an inspection

at 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 activities

and time values for other activities

4




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?




Flow Process Chart

Unplanned

vs.

Planned

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



Flow Process Chart




Worker Process Charts

� Used to analyze the activities of a human

worker 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 forms

and office procedures

5




Flow Diagram

� Drawing of the facility layout with the addition of lines

representing 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 that

may 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), excessive

travel, 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 milling

machine 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 scale

e.g., activity time and cumulative time

Activity chart for a worker performing a repetitive task:

6




Multiple-Activity Charts

� Used to track several participants working together

� They consists of multiple columns, one for each participant.

� Objective: to analyze how the workload is coordinated 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 left hands

� 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 allocated between a worker and a machine

� Help to identify opportunities for cycle time improvements e.g., replacement of external work 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 and balance the workload among the workers




Block Diagrams

� Graphic consisting mostly of blocks and arrows

to 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

7




Block Diagram

AC

AB

x

y

Input

Output

+==1

1

•Used to depict flows and interrelationships

among components in complex systems

•Block diagrams are commonly used in linear

control theory, as shown below for a feedback

control system

31323312ACxAxxAxxCxxx −==−= ,




Process Maps

� A process is a sequence of tasks that add value to inputs

to 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 service

operations

� 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 that

shows the input- output connections among

departments (or other functional components)

of an organization

� Cross- functional process map – block diagram

showing 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- output

connections among departments (or other

functional components) of an organization

8




Cross-Functional Process Map

� Block diagram showing how the steps of a

process are accomplished by departments




Gantt Charts

� A graphical display of schedule project

activities on 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

point during week 7




Gantt Chart Showing Precedence

Arrows can be used to indicate precedence

relationships among activities

objectives of charts and diagrams charting and diagramming ... · checklists general questions...

Documents