Proactive Ergonomics and Cart Handling in the Automotive Industry

Best Practices in Implementing New or Retrofit Industrial Ergonomics Programs in the Automotive Industry

automotive manufacturing industrial ergonomicsThe automotive industry has a long and successful history of employing manual material handling ergonomics programs to reduce the likelihood of musculoskeletal disorders (MSDs) and utilizing proactive ergonomics as a tool for improving both operational efficiencies and product quality.

Early Assessment of Force Requirements

An article in EHS Today, At Ford, Ergonomics Meets Immersive Engineering, describes how Ford has used digital assembly to move ergonomic analysis of tasks far upstream in the design process by building digital models of operators performing assembly tasks with digital components – a virtual operator assembling virtual parts years before a prototype is available!

Combining the digitized operators’ motions with biomechanical models allows Ford ergonomists and engineers to identify and modify high risk operations well before cutting steel to build fixtures and tooling.

So, how did Ford benefit from this process?

  • 80% fewer manufacturing feasibility issues,
  • Very high perception of new product quality from customers – five times the industry average, and
  • A dramatic reduction in injuries, lost time and physical pain, and suffering.

Proactive Ergonomics at Work: Identifying and Retrofitting Existing Designs

As is common practice in the automotive industry, Honda has established internal guidelines for classifying cart push and pull forces. After evaluation of the force required to perform a task, each task receives a color code. Those tasks receiving a red label are high risk and require redesign.

An OSHA Ergonomics Success Story describes how Honda implemented proactive ergonomics. One task required Honda associates to push carts that weighed one thousand pounds or more. The force required to keep the carts in motion was in the green zone (acceptable), but the initial force required to start them moving was deep in the red zone (unacceptable). A team of associates developed an on-demand electric motor assist system to start the carts moving. Once the cart was moving, the motor switched off, which helped to prolong battery life.

What is the ROI on proactive ergonomics programs like this one?

The investment on these systems paid its way and more – a US $1.5 million return over the five-year life of the carts from an initial investment of approximately US $300,000. Honda eliminated any initial cart start forces over 50 pounds-force and the new carts could now carry heavier loads.

Consider Dynamic Braking to Control Stopping of Carts for Improved Ergonomics

Some challenges remain regarding the ergonomics of cart handling. One is stopping carts once they are moving. Sudden stops, such as emergency stops, can place very high loads on the person pushing or pulling the cart.

“Sustained forces aren’t a big issue for us,” said Honda ergonomist José Banaag, “Stopping the cart once it’s moving is a problem.”

Ergonomic Risks of Maneuvering Carts

Operators commonly turn carts; for example, when positioning them on assembly lines. The forces on operators while maneuvering carts is a relatively unexplored area of the ergonomics of manual cart handling that requires more attention.

A study from the Netherlands focused on ergonomic adjustments of catering carts suggests that those forces are equal to the initial force required to start a cart moving. Evaluation tools such as the Liberty Mutual Tables rate acceptable force levels based on the frequency of the higher level of force required to initiate cart movement. Should we be including maneuvering forces in those analyses?

“Maneuvering is a big issue,” says Banaag, “It takes a lot of effort to maneuver carts”.

Ergonomic Testing: Consistent Measurements in Cart Testing & Caster Testing

Brent Bowers, Ergonomics Program Manager at Deere and Company, has responsibility for ergonomics in plants around the world. A big concern is the consistency of the measurement of cart forces.

“We use the ISO 11228-2 measurement protocol to generate the push-pull forces to get more consistency.” said Bowers.

Once they have a representative average force from several trials, they evaluate the acceptability of the required force using the Liberty Mutual Tables.

It is difficult for human operators to push a test cart with the same acceleration for each trial. Consequently, Deere is exploring the development of new techniques to improve the consistency of force measurements. One possible option is an automated system that will consistently assess the forces required to push or pull carts under various loads and with various casters. The system could also be used to assess different cart designs before they are rolled out to the production lines.

Deere is also looking at caster maintenance; for example, over time the convex cross-sectional profile of a caster can wear down, changing the push and pull force requirements. Deere’s innovative idea is to work on the development of a go/no-go caster profile gauge to quickly evaluate when a worn caster should be replaced.

Proactive Ergonomics – Knowledge, Preparation & Design are Key

Proactive assessment of manual cart handling force requirements in the automotive sector has paid off in terms of better cart designs that lower risk of injuries and discomfort, increase operator satisfaction, and gain operational efficiencies.

For a deeper understanding of the ergonomics of safe pushing and pulling and factors to design safer manual material handling tasks, download the Guide to Workplace Ergonomics.

Tom Albin PhD is a licensed professional engineer (PE) and a certified professional ergonomist (CPE). He holds a PhD from the Technical University of Delft in the Netherlands. He is a Fellow of the Human Factors and Ergonomics Society.

Tom has extensive experience as a researcher, corporate ergonomist, and product developer. In addition, he has been active in the US and International Standards community. He is accredited as a US expert to several International Standards Organization working groups and is Vice-Convenor of the ISO committee revising the standards for input devices and workstation layout/postures. He chaired the committee that revised and published the American National Standard ANSI/HFES 100-2007 Human Factors Engineering of Computer Workstations and currently co-chairs the committee working on a new revision of that standard.

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