Title: Principles of Ergonomics
1Principles of Ergonomics
2Assignment
- MacLeod, Chapter Two
- Gabriel, Chapter Two
- Case Examples I and II
3What is Ergonomics?
- Laws of Work
- the science and art of fitting the job to the
employee to - minimize injuries
- improve productivity quality
- The Dual Goals
4Ergo concepts come from . . .
- Engineering concepts
- physics
- psychology
- anthropometry
- anatomy
- physiology
- kinesiology
5Ergo requires skills in . . .
- Teamwork
- problem solving
- innovative thinking
- communications
- economic accountability
- desire to help people
6Why Address Ergonomics?
- Regulatory reasons
- Humanitarian reasons
- Good business practice
7Cost Categories Forgotten?
- Lost productivity
- medical plan
- absenteeism
- reduced quality / service
- employee turnover
- training
8Why?
- Median days away from work for carpal tunnel
syndrome was 30 days (94 BLS) - A single CTD could reach 50,000
- But, we dont need to justify based on claim
costs - Because ergonomics is good business!
9Cost Accounting
- Account for safety injury costs by department
or unit - Coordinate Workers Compensation costs and
Medical costs
10The Risk Factor Model
Lack of Rest
Work/Rest Ratio
Shift Length
Environment
Sustained
Repetition
Occupational
Vibration
Non-Occupational
Temperature
Posture
Physical Temporal Risk Factors
Force
Personal
Psychosocial
Compounding Risk Factors
11Physical Temporal Risk Factors
- Force
- Posture
- Temperature
- Vibration
- Repetitions
- Sustained
- Shift Length
- Work / Rest Ratio
- Lack of Rest
12Vibration
- Identify sources
- Eliminate or isolate if possible
- Dampening
- better tool design
- handle coatings
- dampening gloves
13Thermal Considerations
- Avoid cold exposure to extremities
- especially fingers
- Consider special gloves
- Consider localized heating
14Non-Occupational Activities
- Hobbies
- gardening, knitting, sewing, musical instruments,
etc. - Sports
- jogging, softball, rock climbing, golf, racquet
sports, etc. - Miscellaneous
- household chores, carrying children, driving cars
- Sleep
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16Personal Risk Factors
- Aerobic capacity
- age
- alcoholism
- body build
- diabetes
- flexibility
- gender
- gout
- hypertension
- medical history
- menopause
- Nutrition
- obesity
- oral contraceptives
- posture
- pregnancy
- prior history of injury
- renal disease
- rheumatoid arthritis
- smoking
- stature
- strength
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18Psychosocial Risk Factors
- Organizational climate culture
- Job attitude job satisfaction
- Personality traits
- Personal problems
- marital problems
- death of loved ones
- financial problems
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20Basic Factors for the Design of Products
Workplaces
- People are different.
- People have limitations.
- People have certain expectations and predictable
responses to given situations. - If you ignore these factors, the consequences
will be costly financially and in terms of human
discomfort and performance.
21People are Different
- Go to the presentation titled, People are
Different
22People are Different
- Commonly the workplace is designed for a One
size fits all - This approach ends up fitting only a small
portion of the working population - The workforce is aging
- More experience, but . . .
- Less strength, poorer vision, less range of motion
23People Have Limitations
- Size
- Strength
- Range of Motion
- Vision
- Hearing
24People Have Predictable Reactions
- Spatial Compatibility
- Complexity
25To Err is Human
- Human errors may be due to lack of ergonomics in
design. - With good ergonomics in design, errors can be
reduced.
26Cognitive Errors
- Perception Errors
- Decision Errors
- Action Errors
271. Perception Errors
- The person did not grasp the needed information
for any number of reasons. - The signal or message was not clear.
- There were other distracting signals.
- The person was not trained in the meaning of the
information.
282. Decision Errors
- The person did not respond to the signal or
information - Other decisions had to be made quickly and the
person decided the signal was not important or a
priority. - The person judged the situation incorrectly.
293. Action Errors
- The person reacted, but activated the wrong
control or activated the correct control
improperly. - Controls were not laid out as expected.
- Controls did not operate as expected.
- Inadvertently activated a control when there was
not signal or decision made.
3010 Physical Principles
311. Keep Everything in Easy Reach
- Long reaches can strain the body and make work
more difficult, plus waste time. - Keep frequently used items (knobs, switches,
tools, parts, etc.) within easy reach. - Reduce overall dimensions of work surface.
- Tilt work surfaces upward.
- Make cutouts to allow closer access.
- Use Lazy Susans. Suspend tools in mid-air.
- DESIGN FOR THE SMALLEST PERSONS!!
322. Work at Proper Heights
- Mismatches between worker heights and work
heights leads to awkward/contorted postures and
contributes to fatigue, discomfort and possibly
injury and lower productivity. - Work is generally done at elbow height.
- Heavier work a bit lower.
- Lighter work a bit higher.
- Consider visual demands and lighting.
333. Work in Good Postures
- Corollary to 2. Working in good postures
increases comfort and productivity. - Understand the concept of the neutral posture for
wrists, elbows, shoulders, head/neck, and spine. - Adjustable height angle workstations (p 46)
- Store items in the POWER ZONE (knuckle height to
elbow height) - Pistol grip vs. inline tools (see next slide)
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354. Reduce Excessive Forces
- Anything that can be done to minimize the
exertion required to perform a task. - Needlessly excessive forces load the muscles
creating fatigue and potential injury. - Example Ford truck assembly wiring connectors.
Commonly found forces as high as 75 lbs. Reduced
many forces to as low as 2 lbs.
364 Continued . . .
- Hand Grasping Forces
- Power grips are better than pinch grips.
- Tool grips can be too large and too small
- Two-handed tools are better than one-handed tools
- Arm Push/Pull Forces
- Use mechanical assists and power tools to your
advantage - Use of jigs / fixtures are better than static
grips.
374. Continued . . .
- Loads on lower back
- Utilize the power zone when lifting
- Knuckle to elbow height close in.
- Pushing is better than lifting / carrying.
Pushing is better than pulling. - Larger diameter wheels are better
- Maintain wheels
- Keep floor clean
38Force Guidelines
- Pinch grip maximum 8 lbs
- Power grip maximum 25 lbs
- Push maximum 24 lbs
- Pull maximum 18 lbs
- Static force exertion maximum of 60 s
- Lifting (see NIOSH Lifting Guide)
395. Minimize Fatigue
- Overloading human capabilities can lead to
injuries, accidents, poor quality, lost
productivity. - Avoid static muscle loading
- Restricts blood flow, oxygen, lactic acid
- Better tool handles, Tool Balancers
40Tool Balancer
416. Reduce Excessive Repetition
- The number of repeated motions produces wear and
tear on the body. - Use machines for repetitive tasks.
- Design for motion efficiency and efficient
workstation layout. - Eliminate double handling.
42Repetition Guidelines
- Damaging wrist motion
- 1000 per hour maximum
- 2000 maximum per 8 hour shift
437. Provide Clearance and Access
- Provide space to both get the task done and have
easy access to everything needed. - Provide adequate clearance for head, arms, torso,
knees, feet. - Keep largest and smallest workers in mind during
design. - Design for the range.
- Use adjustable workstation
448. Minimize Contact Stress
- Direct pressure or contact stress can disrupt
blood flow and nerve function. - Remember stress is is the force distributed over
a given area. - Reduce the force
- Increase the contact area
- Avoid sharp edges on work surfaces and tools.
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469. Provide Mobility and Change of Posture
- Even a great posture needs a break
- Sit-Stand Workstations
- Micro-Break Concept
4710. Maintain a Comfortable Environment
- The work environment can directly and indirectly
affect worker comfort, but also quality and
productivity. - There are standards for appropriate
- Lighting
- Temperature/humidity
- Noise
- Vibration
4810 Cognitive Principles
491. Standardize
- Many errors are caused because there is
inconsistency in how information is displayed and
how controls work. - To prevent mistakes, a general rule is to insure
that similar devices work the same way agreeing
on a standard.
502. Use Stereotypes
- A commonly held expectation of what people think
is supposed to happen when they recognize a
signal or activate a control. - Examples
- Moving a lever forward to increase speed
- Rotating a knob clockwise to make a pointer turn
to the right or make it increase - Using red to mean stop or danger
513. Link Actions with Perceptions
- Ideally there should be a strong relationships
between the perception of the need to take an
action and the action itself a compatibility
between a display of information and a control. - Good design means configuring things so that it
is self-evident what one is supposed to do.
524. Simplify Presentation of Information
- Sometimes too much information is provided in too
complex a fashion. - Good designs provide simplified displays.
- Visual images (photos, icons, signs) can be
better than words. - Example The acceptability of universal road
signs (deer crossing)
535. Present Information at the Appropriate Level
of Detail
- Find out what the user needs to know and deliver
at that level of detail not too detailed and
not too simple. - Computer software pop-up help vs. on-line help
vs. a hardcopy users manual.
546. Present Clear Images
- Make images
- Visible
- Size, contrast
- Distinguishable
- Separate from other signals
- Fire alarm bell vs. class bell
- Interpretable
- 1 vs. l
- 6053946067 vs. (605) 394-6067
557. Use Redundancies
- Provide the same information in more than one
way. - Zip code is redundant with street, city,
state - Police car has flashing lights and sirens
- Stop sign has three redundancies red,
octagon, STOP
568. Use Patterns
- Information presented in visual patterns can be
understood more quickly and accurately. - Graphs are usually better than tables of data.
- Normal control settings
579. Provide Variable Stimuli
- Humans detect a novel stimuli more readily than a
constant one. - Flashing lights are more noticeable than
unchanging lights. - Wavering or unusual sirens are more noticeable
than constant ones. - In training sessions, use a variety of techniques
of presenting information.
5810. Provide Instantaneous Feedback
- Provide timely feedback to the user on the course
of action taken. - Repeating a phone number during a conversation
insures success. - Computer keys have an audible or tactile click to
indicate successful use. - Lack of feedback leaves uncertainty and could
lead to further errors.