Ergonomics- Automotive Component Assembly Operation

Task Prior to Abatement (Description)

PBM Industries assembles automobile parts in Chesterfield, Michigan. Lower Control Arm (LCA) was a new automotive component assembled in PBM Industries. It weighed 13.6 kg and was 466 mm long by 90 to 519 mm wide. During assembly, workers had to manually load LCAs onto a conveyor, transfer them onto a fixture for assembly, load ball joints and brackets, and finally unload them. LCAs had to be loaded at each end of the conveyor every 24 seconds. All unfinished and assembled materials had been placed in containers nick-named 5131s. They were 1.3 by 1.0 by 0.8 meter mesh storage containers with a 0.4 meter drop-down section on their front side. There was excessive bending, twisting, and reaching required to manually glide the LCAs into place for assembly. Workers also had to manually fit the LCAs with 2.2 kg ball joints and brackets. Tasks were performed with a conveyor height and a constant LCA height at 1.04 meters.

Task Prior to Abatement (Method Which Verified Hazard)

The 1991 NIOSH Lifting Equation verified that any manual lifting of the LCAs is hazardous.

Task Prior to Abatement (Method Which Identified Hazard)

Increasing number of back injury cases among the workers.

Ergonomic Risk Factor (Force)

Each LCA weighed 13.6 kg and ball joints and brackets weighed 2.2 kg.

Ergonomic Risk Factor (Posture)

Because of the shape, weight, and off-centered center of gravity of LCAs awkward postures were required to manually handle them.

Excessive forward bending and twisting, up to ninety degrees, and excessive reach to the side was required to transfer the LCAs.

Ergonomic Risk Factor (Repetition)

LCAs had to be loaded at each end of the conveyor every 24 seconds.

Ergonomic Solution (Administrative Controls)

  1. A design team consisting of several Industrial Engineers, an Intermet’s Corporate Safety Director, a Safety and Health consultant, an ergonomist, a supervisor, and an employee, who will be transferred to the LCA assembly work area, was established.

Ergonomic Solution (Engineering Controls)

  1. Use of pneumatic or tong – type lifting devices at each end of the line was recommended.
  2. Stopping the use of 5131 containers. 5131s do not allow the use of mechanical or pneumatic lifting devices because of worker over-exertion. Moreover, they are not designed to function properly on a rotating top.
  3. Recommending the use of dunnage with plastic trays that fit six LCAs each.
  4. An excessive length extention arm for LCAs to be used for pneumatic lifting device.
  5. Optimum pallet height range between 95th percentile male knee height to the 5th percentile female shoulder height (0.63 to 1.30 meters) were recommended.
  6. An automatic pallet transfer was recommended for any manual transfer.
  7. Stocking ball joints and brackets as close as possible to the worker and placing them on an adjustable height platform to reduce excessive bending, rotating and reaches.

Ergonomic Solution (Benefits)

  • Developing a well-designed work area with high ergonomics level
  • Increasing quality
  • Increasing safety
  • Increasing productivity
  • Meeting the customer’s specification

Comments

By incorporating ergonomics into the design, not only can built-in problems be reduced, but also customer relations can be enhanced at the same time.

Source

Hilgen, Thomas H., 1995, Ergonomic Solutions for the Same Biomechanical Injury, Advances in Industrial Ergonomics and Safety VII.


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