Ergonomics at assembly workplaces

Status:

completed 02/2008

Aims:

According to the German government's annual accident prevention report, an average of approximately 25% of all working days lost due to sickness are attributable to disorders of the musculoskeletal system and the connective tissue. Work-related stress factors include constrained postures, static body postures and repetitive tasks. Such factors are frequently encountered at assembly workplaces. In the majority of cases, improvements to the design of the workplaces concerned lead to a substantial reduction in exposure. Consideration for anthropometric measurements is not generally sufficient; the form of work to be completed at such workplaces is a further important factor in their optimization. In the course of the project, ergonomic assembly workplaces are to be evaluated in comparison with conventional workplaces. The results then form a basis for a general guidance document for the ergonomic design of assembly workplaces. This document can be made available in the future to the member companies of the BG responsible for the electrical, textile and precision engineering industries (BGETF).

Activities/Methods:

A literature survey was first conducted, in which the existing findings concerning the design of assembly workplaces and ergonomic studies at such workplaces were reviewed and evaluated. A questionnaire was developed for the recording of stresses and complaints among employees at assembly workplaces in member companies of the BGETF. Parallel to this activity, an ergonomic assembly workplace was developed, since searches failed to reveal a commercial workplace which adequately addressed the anthropometric requirements of the employees. The new workplace was installed in six selected plants, and the employees instructed in its use. With the aid of the CUELA measurement system, the stress situation was recorded for comparison purposes on 15 test subjects on both the new workplace and that which it replaced. Workplace environmental factors, workplace dimensions and the ergonomic design of the workplace were documented by means of questionnaires.

Results:

460 questionnaires concerning the stress and strain situation at assembly workplaces were distributed in 13 different manufacturing plants. Of these, 343 questionnaires (response quota: 74.6%) were subjected to statistical evaluation. The results showed that the majority of assembly workplaces could not be adjusted easily to the individual, despite this being both necessary for the tasks and desirable for the employees. The stress factors most frequently indicated were the primary use of the hands, unfavourable postures of the upper body, sustained standing, and physical inactivity. These factors are also reflected in the complaints stated: the proportion of employees with musculoskeletal complaints was high (approx. 70%). Of these, no fewer than 63% (n= 142) were receiving medical treatment.
Working shift profiles of the body posture and the use of the ergonomic assembly workplace were quantified by means of CUELA measurements. The measurement results revealed that only 27% of the test subjects used a combination of sitting and standing positions in order to avoid one-sided working postures. This figure is not consistent with the questionnaire results, according to which 47% of the test subjects indicated that they used this function. A positive observation was that exercise of the lower extremities increased significantly owing to the ergonomic design of the leg space at the new workplace.
It can be summarized that the anthropometric requirements formulated in standards are not adequately addressed by the manufacturers of assembly workplaces and workplace seating, and that despite detailed instruction and an acclimatization phase, the test subjects did not adequately exploit the ergonomic properties of the workplace.
The findings can now be formulated in a guidance document for plants. Attention must be paid to the provision of more intensive support to plants during the implementation of ergonomic assembly workplaces.

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