Groover is an important contributor to industrial engineering literature and teaching.
Groover's book is the latest book available on the subject of work systems improvement.
It still sticks to the content of motion and time study books.
It defines work system as a combination of men and machines/equipment. But it does not attempt to discuss analysis and improvement of machines and machine usage in processes.
As a physical entity, a work system is a system consisting of humans, information, and equipment designed to perform useful work. (Chapter 1)
Contributes to the production of a product or delivery of a service
Examples:
Worker operating a machine tool in a factory
Robotic welding line in an automobile plant
Material move man driving a delivery truck to make deliveries to various production sections in a plant
Designer working at a CAD workstation
Book - Work Systems and the Methods, Measurement, and Management of Work
by Mikell P. Groover,
Chapter 9. Charting and Diagramming Techniques for Operations Analysis
Sections:
Overview of Charting and Diagramming Techniques
Network Diagrams
Traditional Engineering Charting and Diagramming Techniques
Block Diagrams and Process Maps
Gantt Charts
Objectives of Charts and Diagrams Used in Methods Engineering
To permit work processes to be communicated and comprehended more readily
To use algorithms specifically designed for the particular diagramming technique
To divide a given work process into its elements for analysis purposes
To provide a structure in the search for improvements
To represent a proposed new work process or method
How to Create / Develop the Chart or Diagram?
Analyst has to become intimately familiar with the process and develop a graphic to represent it.
Steps.
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 to Find Improvement Ideas
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:
Important to customer
Physically change the product or service
Checklist of Questions - Example
Material
What alternative starting material could be used?
Should the part be produced or purchased?
Production Operations
Can this operation be eliminated, combined, or simplified?
Could a different joining method be used?
Inspection Operations
Could the inspection task be automated?
Categories of Charts and Diagrams
Network diagrams
Traditional industrial engineering charts and diagrams
Operation charts
Process charts
Flow diagrams
Activity charts
Block diagrams and process maps
Gantt charts
Network Diagrams Consist of: Two-way flows (movement of materials):
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 =
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:
Processing and assembly operations
Changing the shape, properties or surface of a material or workpart
Joining two or more parts to form an assembly
Inspection operations
Checking the material, workpart, or assembly for quality or quantity
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?
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:
Flow process chart – analysis of a material or workpiece being processed
Worker process chart – analysis of a worker performing a task
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
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?
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
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.
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:
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)
3Right-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
Block Diagram
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
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:
beginning/ending point of the process,
task or activity step,
decision point
Symbols are connected by arrows to indicate sequence
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
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
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