Although increasing numbers of robots and machines on UK’s production lines have helped with difficult tasks, it is very clear that people remain a key and important resource. Ross Townshend, an expert in manual production systems at Bosch Rexroth, examines how to make people more productive by focusing on workstation ergonomics.
A recent study by the Health and Safety Executive stated that one million people every year are affected by musculoskeletal disorders as a direct result of poorly designed workstations. The impact on the bottom line for UK manufacturers was 11.6 million lost working days at a cost of £5.7 billion.
With statistics like these, it is no surprise that the study of ergonomics is becoming more and more important in UK manufacturing. Done well, ergonomic design can increase motivation, satisfaction with resulting benefits in performance and productivity. However, it remains a badly under-utilised concept in industry, too often regarded as difficult to measure, costly to implement and low on the priority list.
Ergonomics is the study of human interaction with the environment, which in a factory consists of tools, equipment, working methods and the tasks that an individual is being asked to perform. To fully implement an ergonomic solution, there are seven key factors that must be taken into account:
1: Body and working height
Working at the wrong height can lead to a hunched posture, craned neck and strained eyes. Manual workstations must accommodate a wide range of body heights to ensure that a tailored, rather than a ‘one size fits all’, approach is taken.
The most important factors in the design of work stations are the working height, proper sizing of reach zones, leg room and range of vision. It is vital that operators have the opportunity to either sit down or stand up at their workstation, which Bosch Rexroth refers to as the “sit down, stand up” concept. “Sit down, stand up” promotes changes in posture, which reduce stress and increases performance, which is not possible with a solely sitting or standing workstation.
The work area height should always be between 800mm and 1500mm. Working above this height, or above heart level, reduces the blood circulation and oxygen supply, leading to a drop in performance. Work that requires bending (below 800mm) can also hinder productivity and should be avoided.
2: Work area
Ergonomically designed stations reduce the risk of injury by adapting to fit the person instead of the other way around. No two workstations will be alike so it is imperative to find the correct working method for each individual to achieve the best results. Within the work area the following rules must be observed:
1. Avoid work above the heart (over 1500mm);
2. Promote dynamic activities by avoiding standing still or static holding which inhibits circulation and oxygen supply to muscles;
3. Allow for varying physical exertion through use of “stand up, sit down” or job rotation;
4. Minimise exertion through use of manual roller sections or lifting aids.
3: Reach zones
There are three key rules to follow when designing an employee’s reach zone at their workstation:
1. All containers, equipment and operating elements must be easily accessible and arranged in the optimum anatomic/physiological range for employees;
2. Torso rotation and shoulder movements, particularly when under exertion (with weights of more than 1 kg) should be avoided whenever possible;
3. A well-designed workstation should be set up into three zones. Primary; for equipment used constantly throughout the working day with equipment or tooling within easy reach when elbows are at an operator’s sides; secondary, for tools and parts that are often reached with one hand with everything being available within a 1800 sweep of both arms when outstretched; and reference, for occasional handling such as reference files or transferring parts to the next workstation.
4: Parts presentation
The presentation of parts to the operator is key in minimising physical exertion and unnecessary movements. The key issues that need addressing are:
1. Frequently used grab containers should be placed at short distances
2. Heavy parts should be stored within easy reach in lower containers
3. Where possible use a slide rail or roller conveyor to minimise employee exertion
5: Range of vision
Each head turn or change in line of sight, results in lost time and decreases productivity. For the optimal workstation design, it is important to address every detail, including head and eye movement. Key vision issues for workstation planning are:
1. Avoid unnecessary eye and head movements;
2. Vision distances should be as identical as possible to eliminate refocusing;
3. Avoid fastening locations not visible to the operator.
The correct light, adapted to the activity of the workstation, is a basic prerequisite for high efficiency and quality. It is therefore important to:
1. Avoid strong lighting contrasts;
2. Avoid glare and reflection;
3. Ensure all workstations are free from shadows, flickering and glare.
7: Adjustment of work equipment
To maintain performance levels and promote productivity, the correct adjustment of a table, chair, footrest and position of tools and material shuttles must be easily achieved. For example, Bosch Rexroth’s versatile aluminium structures ensure that tables, footrests and grab containers can be easily adjusted. What’s more, the correct sitting posture is vital with worker’s calves forming a 90o angle and appropriate lumber support.
A very important message for production line designers and planners to understand is that specialist help and software tools are available at the planning stage. These tools can enable correct design before any material is ordered. Ergonomics starts with design, not adjustment of equipment on the shopfloor - this will always be a compromise. In conclusion, specialist planning and design tools, such as Rexroth’s MTpro, are available to help in the design of ergonomic workstations, which will ultimately deliver a more efficient daily work routine and benefit the bottom line.