Part 4 Lesson 1 and 2 Basic Motion Elements and Work Design

PART 4 Work Study and Measurement
Learning Objectives:
Upon completion of PART 4, you will be able to:
1. Explain the principles that apply to the use of the human body,
workplace arrangement, and design of tooling and equipment
2. Identify and classify the17 Therbligs Basic Motion Elements
3. To analyze therbligs that make up a repetitive task
4. Principles of Motion Economy
Learning Materials:
1. Laptop/Personal Computer/Cellphone/Tablet
2. Copy of Work Study and Measurement Module
3. LCD Projector (for Faculty use only during lectures)
4. Calculator
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LESSON 1: Motion Study and Work Design
Definitions
Motion study - analysis of the basic hand, arm, and body movements of workers as they
perform work
Work design - design of the methods and motions used to perform a task
Design of the work system
 Includes:
 Workplace layout and environment
 Tooling and equipment used in the task workholders, fixtures, power tools,
etc.
Basic Motion Elements

Frank Gilbreth – first to analyze and classify the basic motion elements
 “Therblig”s – 17 basic motion elements
 Spelled backward except for “th”
 Therbligs are the basic building blocks of virtually all manual work performed
at a single location (so the primary interest is the hand motions).
 Therbligs involves both physical and mental elements.
 Although it is first used in production and logistics, the principles are also
applicable to service industry.
17 Therbligs Basic Motion Elements

1. Transport empty (TE) – reach for an object with empty hand
– today we call it “reach”
2. Grasp (G) – grasp an object by contacting and closing the fingers until control has
been achived
3. Transport loaded (TL) – move an object with hand and arm
– today we call it “move”
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4. Hold (H) – hold an object with one hand

5. Release load (RL) – release control of an object
6. Use (U) – manipulate/use a tool (use screwdriver or hammer)
7. Pre-position (PP) – position object for next operation.
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8. Position (P) – position object in defined location
9. Assemble (A) – join two parts
10. Disassemble (DA) – separate multiple parts that were previously joined
11. Search (Sh) – attempt to find an object using eyes or hand
12. Select (St) – choose among several objects in a group (hand-eye coordination is
involved)
13. Plan (Pn) – decide on an action (a short pause or hesitation ‫ ددرت‬in the motions)
14. Inspect (I) – determine quality of object using the eyes
15. Unavoidable delay (UD) – waiting due to factors beyond worker control (e.g., waiting
for a machine to complete its feed motion)
16. Avoidable delay (AD) – worker waiting (e.g., use the mobile)
17. Rest (R) – resting to overcome fatigue
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Example (Right hand/left hand activity chart)
Seq Work element description Worker

. time
1 A worker picks up board with left 0.08 min.
hand and holds it.
2 Worker picks peg from tray and 0.06 min.
inserts it into hole in board with
right hand.
3 Worker picks second peg from
tray and inserts it into hole in
board with right hand
0.06 min.
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Micromotion Analysis
 Analysis of therbligs that make up a repetitive task

 Objectives:
 Eliminate ineffective therbligs if possible; for example, eliminate the need to
search for parts or tools by positioning them in a known & fixed location in
the workplace.
 Avoid holding objects with hand – Use workholder
 Combine therbligs – Perform right-hand and left-hand motions
simultaneously
 Simplify overall method resequence of therbligs in the cycle
 Reduce time for a motion, e.g., shorten distance of therbligs such as transport
loaded.
Lesson 2: Principles of Motion Economy
Developed over manyyears of practical experience in work design

 Guidelines to help determine
 Work method
 Workplace layout
 Tools, and equipment
 Objective: to maximize efficiency and minimize worker fatigue
Three Categories of Motion Economy & Work Design Principles

1. Principles that apply to the use of the human body
2. Principles that apply to the workplace arrangement
3. Principles that apply to the design of tooling and equipment
1. Use of Human Body

 Most applicable to manual work. There are 12 principles related to the use of human
body.
Important principles related to the worker hands
1. Design work to fully utilize both hands (the worker uses always the preferred hand to
accomplish most of the work).
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2. Hand and arm motions should be symmetrical and simultaneous to minimize

hand/arm-eye coordination
 Avoid different independent motions of hands/arms
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3. Design work to favor preferred hand
 Work units should enter the workplace on the side of the worker’s preferred
hand (preferred hand is faster & stronger)
An experiment (Example)
A relatively simple task
 Reaching, selecting, grasping, transporting, releasing small parts.
 Two types of container
 A rectangular bin
 A bin with a tray
 The worker performed the work cycle with each container using
 Only the right hand
 Only the left hand
 Both hands performing symmetrical and simultaneous motions.
Note: Worker is a right-handed person
4. Take advantage of Gravity- Don’t oppose it (Important principles related to utilize

laws of physics)
5. Use lowest classification of hand and arm motion (five classifications)
I. Finger
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II. Finger and wrist

III. Finger, wrist, and forearm
IV. Finger, wrist, forearm, and upper arm
V. Finger, wrist, forearm, upper arm, and shoulder
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I. Movement of the fingers only as when picking up a cotton roll
II. Fingers and wrist motion as used when transferring an instrument to the
operator, or manipulating a hand instrument.
III. Fingers, wrist, and forearm as when reaching for a handpiece.
IV. The entire arm when reaching for supplies away from the work area, or to
adjust the operating light.
V. The entire arm and shoulder as when turning around to reach for equipment
from adjacent fixed cabinetry
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6. Design method to utilize feet and legs where appropriate
 Since they are stronger than arms
7. Worker’s two hands should not be idle at the same time
8. Method should consist of smooth continuous curved motions rather than straight
motions with abrupt changes in direction
9. Method should achieve a natural rhythm of the motions involved
10. Minimize eye focus and travel
2. Workplace Arrangement
Principles for Design of the workplace

1. Locate tools and materials in fixed positions within the work area
2. Locate tools and materials close to where they are used
 To minimize the distances to be covered
3. Locate tools and materials to be consistent with sequence of work elements
 Decrease the time required for searching
Normal and maximum working areas in the workplace

Design for average user
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Numbers indicate the sequence of operations
4. Use gravity feed bins to deliver small parts and fasteners
Two types of bins used for small parts and fasteners in the workplace:
(a) gravity feed bin (b) conventional rectangular bin
5. Provide adequate illumination

 Also color, contrast among items, location of the light source are important
6. A proper chair should be provided for the worker
 Adjustable to the size of the worker
 Seat height and back adjustments
 Padded seat and back

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3. Design of Tooling and Equipment

1. Work holding devices should be designed for the task
2. Hands should be relieved of work elements that can be performed by the feet
using foot pedals
 sewing machine OR advance welding machine
3. Combine multiple functions into one tool where possible
 Hammers designed for stick and remove nails
4. Perform multiple operations simultaneously rather than sequentially
 Pneumatically powered, multiple- spindle lug nut to attach tires to the car
assembly.
5. Design equipment controls for operator convenience and error avoidance

 Controls (e.g., switches and push buttons) should be located within easy
reach to minimize the body motions required to access them
6. Mechanize or automate manual operations if economically and technically
feasible
7. Hand tools and portable power tools should be designed for operator comfort
and convenience
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PART 4 Work Study and Measurement

Upon completion of PART 4, you will be able to:

2. Copy of Work Study and Measurement Module

3. LCD Projector (for Faculty use only during lectures)

LESSON 1: Motion Study and Work Design

Basic Motion Elements

 Spelled backward except for “th”

 Therbligs involves both physical and mental elements.

17 Therbligs Basic Motion Elements

4. Hold (H) – hold an object with one hand

Seq Work element description Worker

 Analysis of therbligs that make up a repetitive task

Lesson 2: Principles of Motion Economy

Developed over manyyears of practical experience in work design

Three Categories of Motion Economy & Work Design Principles

1. Use of Human Body

2. Hand and arm motions should be symmetrical and simultaneous to minimize

4. Take advantage of Gravity- Don’t oppose it (Important principles related to utilize

II. Finger and wrist

III. Fingers, wrist, and forearm as when reaching for a handpiece.

Principles for Design of the workplace

Normal and maximum working areas in the workplace

4. Use gravity feed bins to deliver small parts and fasteners

5. Provide adequate illumination

 Adjustable to the size of the worker

 Seat height and back adjustments

 Padded seat and back

3. Design of Tooling and Equipment

5. Design equipment controls for operator convenience and error avoidance

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