Challenges in ergonomics design

Isa Halim et al. AJE Vol.9 2009 109-121 112

3. The integrated ergonomics analysis and QFD method

Ergonomics is a scientific discipline concerned with the understanding of interactions among humans and work systems. It optimizes human well-being and overall work system performance by applying theories, principles, data and methods to product design International Ergonomics Association, 2000. Ergonomics is widely applied in many industrial applications. One common application of ergonomics in industry is to minimize the risk of occupational injuries during manual material-handling activities. Many studies have identified manual materials activities as a primary contributor to lower back pain among industrial workers Kuiper, et al., 1999; NIOSH, 1997; Burdorf and Sorock, 1997. Ergonomic design of MHDs is seen as one approach to minimize occupational injuries. Occupational health and safety, comfort, productivity, quality, as well as work efficiency can be improved by improving the ergonomics criteria and usability of MHDs. Many studies have applied ergonomics analysis to improve the usability of MHDs by reducing biomechanical stresses during performing manual material-handling activities Resnick and Chaffin, 1995; Okunribido and Haslegrave, 2003; Glitsch, et al., 2007. In recognition the importance of developing usable products of high quality, human needs and requirements are primary concerns that must be considered during the design and production stages. By applying the QFD method, various human needs and technical aspects can be integrated systematically to establish product design and specifications, so that the products fulfill market demands. Ergonomics can be integrated with QFD because humans’ needs are usually determined by considering human abilities and limitations. The association between the quality of a product and its accommodation of human abilities and limitations could be explored easily with the help of knowledge in ergonomics Bergquist and Abeysekera, 1996. In addition, QFD method has been recognized as the most suitable approach to ensure attention to comfort requirements in the design process of a product, because it is the only means that explicitly addresses the translation of humans needs such as comfort into technical specifications Kuijt-Evers, et al., 2009. Previously, QFD has been applied by to investigate the specifications of studied product that can satisfy humans needs; products include a boning knife Marsot, 2005, pruning shears Haapalainen et al. 19992000, and safety shoes Bergquist and Abeysekera, 1996. In all cases QFD increased user satisfaction while meeting safety needs.

4. Methods

The process of redesigning the MHDs began by identifying the type of HPT and its applications. A questionnaire was developed and distributed among industrial workers to acquire their requirements regarding the design of an HPT. The questionnaire is divided into four sections: 1 personal details of worker, 2 ergonomics analysis, 3 information on the existing HPT, and 4 features for Redesign of a hand pallet truck by integrating Ergonomics analysis and quality function deployment 113 improvement. In the personal details section, workers’ demographic information, such as age and gender were obtained. This information is necessary because even though most HPT users are young males, the design of the HPT should be acceptable for most users Mack et al., 1995. In ergonomics analysis section, information was obtained about the frequency of HPT use, and the types of difficulties and injuries experienced by the workers when handling the HPT. The third section captures workers’ comments regarding the existing HPT. Scores 1 to 5 1: unnecessary; 2: less needed; 3: needed; 4: desirable; and 5: critically desirable are used to identify the workers’ requirements regarding to the features of HPT such as structure, wheels, handle, security system and forks. The final section of questionnaire recorded the workers’ requirements for the new design of an HPT. The information was analyzed using the QFD method. Workers’ requirements were utilized to redesign the existing HPT with the objective of fulfilling workers’ satisfaction. As illustrated by Figure 1, it is described steps involved in capturing and analyzing workers’ requirements. The first three steps involve populating and capturing workers’ requirements, developing the workers’ portion of the matrix, and developing the technical portions of the matrix. In the final step this matrix is analyzed and design attributes are prioritized. Meanwhile, Computer Aided Design CAD that is available in CATIA Software was used to redesign the HPT.

5. Case Study

A direct workplace survey using questionnaires was conducted among 30 production workers who were familiar with using an HPT. The average age of workers was 25.3 years; all were male. Of these workers, 60 used the HPT 1 to 20 times per day, 37 used it 21 to 40 times and only 0.3 of worker used it 61 to 80 times per day. Of these workers, 86.6 of them have experienced difficulties while handling the existing HPT: 32 when transferring heavy objects, 19 during handling, 18 while pushing and pulling the HPT and 15 while lifting the objects. Difficulties reported include size of load, instability when transferring loads, and unsatisfactory maneuverability. Only 53.3 of workers agreed that the existing HPT is suitable for the current job; the rest said that they needed assistance from colleagues to move the HPT while transferring loads. Injuries experienced by the workers when handling the existing HPT were also investigated. Of the workers, 86.7 had been injured when operating the existing HPT, 60 had experienced discomfort and injuries in their shoulders, 30 had suffered arm injuries, 40 had suffered wrist injuries and 30 had experienced injuries and pain in their lower back, 16.7 had felt discomfort in their upper back, 6.7 had suffered leg injuries and 2 had suffered neck and ankle injuries. The workers were also interviewed regarding their requirements on the main features of the existing HPT. Their inputs Table 1 are important in development of a new HPT. Workers’ inputs relating to design improvement of HPT were divided into five categories of score: 1 unnecessary; 2 less needed; 3 needed; 4 desirable and 5 critically desirable. Findings indicate that “easy to maneuver”, Isa Halim et al. AJE Vol.9 2009 109-121 114 “stability of load”, and “able to carry various sizes of object” as the critically desirable requirements. Workers’ requirements for the new HPT design were compiled in the customers’ requirements section of the QFD House of Quality HoQ Figure 2. Table 1. Workers’ requirements to improve the existing HPT Score Features Workers’ requirements 1 2 3 4 5 Relative importance Light 6 5 6 5 8 3.13 Structure Stable while maneuvering 1 3 15 11 3.20 Having front wheels 3 10 9 7 1 2.77 Having rear wheels 2 6 11 10 1 3.07 Wheels Easy to maneuver 1 9 13 7 3.83 Comfort handle height 3 9 8 7 3 2.93 Comfort handle size 4 9 8 7 2 2.80 Handle Comfort handle position 5 7 9 9 0 2.73 Security of carried object 1 15 8 6 3.60 Security system Stability of load 1 2 8 13 6 3.70 Able to carry various sizes of object 1 3 9 9 8 3.67 Fork Suitable size of fork 2 6 12 6 4 3.13 Rating Score: 1- Unnecessary, 2- Less needed, 3-Needed, 4-Desirable, 5-Critically Desirable