The technical progress of the past few decades have substantially changed the work environment by new technologies. While computers, laptops and tablets have replaced typewriters in the administrative area, Computerized Numerical Control (CNC) is being used more and more on machinery tools in manufacturing industry in order to make manufacturing more flexible, efficient and faster.
The step-by-step implementation of CNC technology has challenged and is still challenging employees and companies in various ways. On the one hand, elder employees, who have always carried out physically strenuous work on conventional machines, are being confronted more and more with knowledge-based computerized systems that are often unfamiliar to them. On the other hand, at the time of demographic changes with the increasing of employee's age, companies face an issue to still be competitive on the international market. The CNC technology is in constant development. That is why ''lifelong learning'' of workers in manufacturing area is essential for the competitiveness of companies. This paper observes work place of machine operator and, especially, adaptation of the CNC system to the worker. Emphasis is placed on the possibility to find an appropriate design of information means of the CNC control unit, e.g. control elements and displays.
Based on studies in this paper, the usability of the system “CNC machine” was tested for the phases of first and further education with objective measurement methods and procedures. Besides this, also the subjective aspects of the work of CNC machine tools have been observed. To achieve this, was checked whether the operation of a CNC machine is designed in such a way that it can be easily operated by users of any age, experience level or experience background. Also the physical strain presented after the implementation of the CNC technology was observed.
In the pilot study, general information about weaknesses and possible issues of manmachine- interface of CNC machine were detected. For this purpose, a survey was carried out among 122 users in several training centers in the region of Bergisches Land. The survey has been carried out by a standardized questionnaire, which has been developed for this purpose. Based on received data, working hypotheses were derived and further examined in three different studies, here called “loops”.
In Loop 1, first of all the technical aspect of operating CNC machines has been observed. Usability tests were carried out on CNC machines in training centers with 24 users. As a result the subjective data collected in the pilot study was added by objective data from measurements during the operation CNC machines. Tests were conducted with the help of the so-called Eye-Tracking system that can be used to record the performance of a person while operating a CNC machine.
In Loop 2, about 800 job task analyses describing the system ''machine operator'' at workplaces derived with the help of so-called “Ergonomic Risk Assessment” (BDS) were analized. It was found out which part of working time machine operator spends for the operating a CNC machine and which part for other activities which is usually done. Especially body posture, load handling and work intensity were observed.
Loop 3 was focused on the human body size. During a cross-section study made among 800 people, the current anthropometric data of a representative sample of the German resident population was obtained and analyzed.
The pilot study (standardized survey of users) firstly indicated age-specific differences in the evaluation of interaction systems (CNC control interfaces) of various producers. Operating errors were also traced to varying designs of operating elements, multiple assignments of buttons and their unclear pressure point. The dimensions of the operating elements are often criticized to be too small. Different aspects of the organization of the work place e.g. access to the machining space or the position and arrangement of the operating panel are connected with partly unfavorable body postures and complaints in the musculoskeletal system.
Loop 1 (field tests with the help of an eye-tracking system) provided information's about the performance on different CNC machines. As a result, intra-individual as well as interindividual differences in operation were found. Here, design of visual and tactile information means on various control panels was observed. The comparison of two control panels with shopfloor programming (version H1: Shopfloor programming using input mask and version H3: Shopfloor programming with DIN/ISO-programming) showed a significant better performance among users in favor of the version with input masks. However, none of the tested control panels completely met the user requirements. Moreover, unfavorable handarm positions and body postures were often taken during programming and operating activities.
The results from Loop 1 were also confirmed in the job analyses in field data collecting (Loop 2). It shows that some jobs, e.g. monitoring the machining procedure can take up to 100% of the workday and are mostly done only in standing or partly in a forward-leaning position.
Apart from the actual work on CNC machines, machine operators have to often carry out extensive manual handling of loads.
The analysis of the anthropometric data from Loop 3 showed different trends of the observed data. In comparison to the available data from the current standards and literature, increasing of the 95th percentile of thumb width and at the same time decreasing of the 5th percentile of the forefinger thickness was detected.
Based on the gained knowledge, recommendations for choosing and designing of CNC control unit were developed for users and buyers. These provide specific instructions for design possibilities of CNC machine and its elements in the working system. It should help to increase the part of ergonomic and demographic work places in companies and make it possible for employees of any age to do their work.
All this shows the needs of further development and research to transfer results of this study to other activities and working systems.