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

• 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

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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)

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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.

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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)

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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)

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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.

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What happens when work is rationalized?

• Mechanical Exposure Risk Factors for WMSD of the
  Back/Shoulder/Distal Arm
• Magnitude
• Duration?
• Time Variation Pattern ...

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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

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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
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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

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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
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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

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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

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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

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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

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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

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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
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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
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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.

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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

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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