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Time as a key issue for enhanced cooperation between engineering and ergonomics for improved musculoskeletal health and production

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Time as a key issue for enhanced cooperation between engineering and ergonomics for improved musculoskeletal health and production – PowerPoint PPT presentation

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Title: Time as a key issue for enhanced cooperation between engineering and ergonomics for improved musculoskeletal health and production


1
Time as a key issue for enhanced cooperation
between engineering and ergonomics for improved
musculoskeletal health and production
  • Richard Wells(1), Svend-Erik Mathiassen(2,3),
    Lars Medbo(4), Jörgen Winkel(2,3)
  • (1)Department of Kinesiology, Applied Health
    Sciences, University of Waterloo, Canada
  • (2)Division of Production Ergonomics, School of
    Technology and Society, Malmö University, Malmö,
    Sweden
  • (3)National Institute for Working Life, Sweden
  • (4)Department of Transportation and Logistics,
    Chalmers University, Gothenburg, Sweden

2
Story 1 The Dentist story
  • Dentists in Sweden had problems with neck/
    shoulder pain. Ergonomists redesigned the work
    area including the chair and tool placements. At
    the same time work rationalization occurred and
    dentists spent more time on high value added
    tasks.
  • After both interventions the level of
    musculoskeletal problems was unchanged
  • (Winkel and Westgaard 1986)

3
Story2 Line Balancing
  • An ergonomist redesigned a workstation of an
    assembly line job which was reporting a high
    number of reports of discomfort. The solution was
    proposed, pilot tested and installed. The
    consensus of the workers, ergonomist and
    supervisors was that work at the station was much
    improved. Two weeks later engineering re-balanced
    the line and added two new elements.
  • The ergonomist is no longer welcome and is
    regarded as a job-killer.

4
Story 3 Paradoxical Effect of a Sophisticated
Production System
  • Two production lines making the same product are
    compared in two different countries. In one there
    are frequent delays in the production system and
    the workstations are rudimentary. In another, the
    production system is more sophisticated with
    better balancing and attention paid to design and
    adjustability of the workstations. Both however
    had similar static load in the trapezius.
  • The better balancing of the second production
    system reduced the pauses and appeared to
    counteracted the improved workstation design
  • (Bao et al., 1997)

5
Story4 Partial Automation Leading to Work
Intensification
  • Automation was introduced to a pencil packaging
    line to increase productivity.
  • Packaging was semi-automated where the machine
    grouped the pencils but the worker had to insert
    the bundle of pencils into the case and stack the
    packaged pencils.
  • One line was unchanged with no machine feeding.
    Both showed similar force requirements.
  • The semi-automated process had the shorter cycle
    time, the higher rate of movements and the more
    stereotypical movements.
  • Partial-automation may lead to work
    intensification
  • (Coury et al., 2000)

6
The Issue
  • This paper summarises the aims, actions and tools
    of engineers and ergonomists when they attempt to
    manipulate time aspects of work.
  • This issue is of interest because manipulation of
    time affects mechanical exposure is important to
    the risk of developing musculoskeletal disorders
    (MSDs) and is key to the activities of engineers
    in a production system.

7
What happens when work is rationalized?
  • Mechanical Exposure Risk Factors for WMSD of the
    Back/Shoulder/Distal Arm
  • Magnitude
  • Duration?
  • Time Variation Pattern ...

8
What happens when work is rationalized?
  • Changes (often for the worse) to parameters
    describing the time variation pattern of
    mechanical exposure
  • Time in Awkward Posture1
  • Frequency of Performing Actions
  • Angular velocity/acceleration of motions
  • Duty Cycle (Work/Rest ratio)
  • Hand Activity Level (HAL)
  • Muscle Rest/Gaps
  • Static Level
  • Average Load
  • Cumulative load

9
Example Aims of Ergonomists
  • Aim
  • To eliminate or reduce mechanical risk factors
    for WMSD
  • Time Implications
  • Will often reduce the peak magnitude but may find
    it difficult reduce frequency of activities or
    time in loaded conditions

with respect to musculoskeletal disorders
10
Example Aims of Engineers
  • Aim
  • Increase productivity
  • Reduce (time) losses
  • Time Implications
  • May lead to work intensification with higher duty
    cycle (less rest)
  • Work intensification

11
Example Actions of Ergonomists
  • Action
  • Reduce reach
  • Introduce job rotation
  • Time Implications
  • Creates smaller peak loads and smaller cumulative
    loads
  • Creates more task variety but possibly similar
    motor variety

with respect to musculoskeletal disorders
12
Example Actions of Engineers
  • Time Implications
  • Higher monotony and frequency
  • Less rest time
  • Action
  • Partial automation
  • Higher job loading i.e. more tasks/ fewer
    non-value added elements

13
Example Tools of Ergonomists
  • Tool
  • Activity sampling
  • SNOOK tables
  • Time Implications
  • Quantifies tasks, nominal task variety, time in
    defined activities
  • Predicts affect of frequency on acceptable load

14
Example Tools of Engineers
  • Tool
  • Activity Sampling
  • Discrete Event Simulation
  • MTM
  • Time Implications
  • Quantifies value vs non-value added activities
  • Helps examine time losses in system
  • Sets normative movement frequency

15
Engineering Decisions
  • have major effects on mechanical exposure,
    especially its time variation patterns, likely of
    much greater magnitude than many ergonomic
    interventions.
  • often made very early in the design process
  • often difficult to change later
  • address both system and individual levels with
    system and individual level tools

16
Ergonomic Decisions
  • have major effects upon mechanical exposure,
    especially the magnitude of forces and
    distances/reaches
  • often made (too) late
  • cannot affect issues of time
  • address both system and individual levels but
    few if any system level tools

17
Examples
  • Ergonomic consequences of engineering decisions

Reduction in system level manual work but
intensified individual work0
Engineering changes to electronic assembly
including parallel-batch to serial-line assembly
Reduction in work-in-progress and labour inputs
Reduction of work task variability/increase in
monotony
Neumann, P. Kihlberg, S. Medbo, P. and Winkel, J.
Case study of the ergonomics consequences of
engineering decisions, This conference
18
Examples
  • Development of an Ergonomic Evaluation Tool which
    Interacts with Engineering Time Standard Data

Neumann, W.P., Wells, R.P., Norman, R.W. (1999)
4DWATBAK Adapting research tools and
epidemiological findings to software for easy
application by industrial personnel. Proceedings
of the International Conference on Computer-Aided
Ergonomics and Safety, Barcelona, Spain
19
Summary
  • This review shows that there are some common
    tools available to both groups, such as activity
    sampling, but mainly at the level of the
    evaluation of an individuals work. There are
    opportunities for more research and co-operation
    especially in the area of the prediction and
    evaluation of ergonomic quality at the production
    system level.

20
There are many opportunities for more research
and co-operation
  • Epidemiological studies which measure more
    intensively the time variation patterns of risk
    factors along with musculoskeletal health outcome
    measures
  • Incorporation of ergonomic evaluation component
    into current engineering techniques
  • The prediction and evaluation of ergonomic
    quality at the production system level
  • Ergonomic measures acting at the system level
  • Technical consequences of ergonomic decisions
  • Ergonomic consequences of technical decisions
  • Sensitivity of time related risk factors to
    engineering decisions

21
Acknowledgements
  • The authors would like to acknowledge the support
    of the Canadian Association of University
    Teachers (CAUT) (for partial sabbatical support
    of one of the authors, RW), and the National
    Institute for Working Life West, Gothenberg and
    Division of Production Ergonomics, School of
    Technology and Society, Malmö University, Malmö,
    Sweden
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