ABSTRACT
During the last decades, a huge amount of heavy physical work load was increasingly replaced by Computcrized-Numerical-Control (CNC) Units in manufacturing areas. Hence manual work is decreasing, while static work (e.g., standing, sitting) and cognitive demands rise in these fields of activity. Machine operators have a high responsibility, because mistakes may lead to human injuries as well as to product losses ~ and in consequence may lead to high monetary losses as well. An intuitive usability and an ergonomic organization of CNC workplaces can be an essential basis to reduce the risk of failures in operation as well as physical complaints (e.g. pain or diseases because of bad body posture during work). Within this study, a standardized questionnaire was developed and a survey was carried out among trainees leaming the operation of CNC operated machines. The content of the questionnaire were sociodemographic data, questions on "weak spots" or troubles during operating the CNC machines as well as questions about general working conditions and musculoskeletal symptoms and disorders. Besides, the design of the workplaces was documented in a check list. 112 male trainees (age 17 to 56 years) from 4 training centers were included in the first evaluation. This survey discovered that there is a need of optimization of the
INTRODUCTION Since beginning of the 1970's hard manual work in the production is replaced by computer-controlled machines. Today, modem machines are equipped with complex CNC control units, which make highly complex and precise phases of operation possible. Manual work decrease but static work (e.g. long standing) and cognitive demands in these fields of activity increase. Machine operators have a high responsibility, because operating errors can lead to machine and/or product damage as well as to human injuries. High economic andlor human losses could result in consequence. The current developments in the industrial production area go away from homogeneous mass production to a product usage production. This "lean production philosophy" leads to the fact that machines must be reequipped more frequently. From economic view, it is important that after a re-equipment, the first workpiece fits. This increases the psychosocial pressure to the persons employed at the machines to avoid errors. An intuitive operability and an ergonomic organization of CNC units can be a substantial basis to reduce the risk of operating errors and physical complaints, too. The research questions in this study are: How is the usability of CNC units? Which faulty operations arise and which damage occurs with it? Which ergonomic optimizations are needed?
