Preface:
The goal of any ergonomics process is to eliminate or prevent exposure to the root causes of injury; Force, Frequency, and Posture. These risk factors act alone and in combination to slowly deteriorate the soft tissues of the body, potentially leading to a permanent disability (work-related musculoskeletal disorder) over time.
The most effective means by which to control these risk factors is through the implementation of thoughtful engineering practices. In other words, designing all new operations, and/or modifying existing operations to fit the human body.
The checklists below specify important criteria to be taken into account when evaluating the ergonomic acceptability of existing workstations, optimizing the design of new assembly lines or work cells, and/or purchasing tooling and equipment from external vendors.
The 8 checklists, each focused on a unique and specific set of criteria, are as follows:
- Standing Workstation – Design Criteria
- Seated Workstation – Design Criteria
- Work Reach Envelope – Design Criteria
- Visual Work Envelope – Design Criteria
- Work Chair – Design Criteria
- Tooling – Design Criteria
- Work Area Clearances – Design Criteria
- Access Port Clearances – Design Criteria
The criteria outlined in each checklist are based on anthropometric studies of healthy working-age adults and are intended to ensure that the majority (90%) of the working population can complete their job duties in neutral body postures; extremely tall or extremely short individuals may require special accommodation.
It is also important to note that the guidelines are generic in nature and in some instances, must be adapted to a specific or unique work environment.
The following table outlines design criteria for workstations in which the operator is standing:
Figure 1: Standing Workstation
The following table outlines design criteria for workstations in which the operator is sitting:
Figure 2: Seated Workstation
The following table outlines appropriate horizontal reach distances according to type/frequency of work being performed:
Figure 3: Work Reach Envelope
The following table outlines the optimal visual angles for minimizing non-neutral head/neck postures:
Figure 4: Visual Work Angles
The following table outlines appropriate design criteria for a work chair:
Additional Criteria:
- Ensure seat pan has a waterfall-shaped front edge to minimize compression forces to the underside of the thighs – the radius of the front edge curve should be no less than 4 cm (1.5″) and no greater than 12 cm (5″)
- Cushioning materials within the seat pan and back rest should be expanded flexible urethane foam of either flat slab, sculpted slab, or moulded construction
- Chair should be equipped with a 5-caster base to minimize tipping
- Controls should be operable form the usual seated working posture, have markings visible from a seated position, not require undue force exertion for activation, not require special tools for adjustment, and designed to prevent unintentional actuation
Figure 5: Work Chair
The following table outlines appropriate design criteria for industrial hand tools:
Additional Criteria:
- Air exhaust should be directed toward the front of the tool rather than toward the operator’s hand/wrist
- Any tools surfaces that generate heat or cold and are in contact with the hands should be insulated
- Strip triggers are preferred over single finger triggers to provide operators with more options and encourage multi-finger activation
- If possible, thumb triggers should not be used because the thumb is primarily used as a grip stabilizer. Using the thumb to trigger a tool reduces the stability of the tool
- Tools used to cut or exert large forces should be designed with stops or guards to prevent slippage of the hand
- Tool trigger activation forces should not exceed 2.4 lbf. or 10 N
- Tools weighing in excess of recommended guidelines should be suspended from a counterbalanced arm or tool balancer, particularly for overhead work
- Operators should be provided with anti-vibration gloves when using tools that vibrate
Figure 6: Tooling – Handle Length and Diameter
Figure 7: Tooling – Weight
Figure 8: Tooling – Cutouts and Grip Spans
Figure 9: Tooling – Triggers
The following table outlines appropriate design criteria for work area clearances, critical for machine maintainability:
Figure 10: Work Area Clearances in Prone Position – Lying on Back
Figure 11: Work Area Clearances in Prone Position – Lying on Stomach
The following table outlines appropriate design criteria for access port clearances, critical for machine maintainability:
Figure 12: Full Body Access Port Clearances
Figure 13: Arm Clearances
Figure 14: Hand Clearances
