Abstract—The intention of this study to design the probability optimized sewing sack’s workstation based on ergonomics for productivity improvement and decreasing musculoskeletal disorders. The physical dimensions of two workers were using to design the new workstation. The physical dimensions are (1) sitting height, (2) mid shoulder height sitting, (3) shoulder breadth, (4) knee height, (5) popliteal height, (6) hip breadth and (7) buttock-knee length. The 5 th percentile of buttock knee length sitting (51 cm), the 50 th percentile of mid shoulder height sitting (62 cm) and the 95 th percentile of popliteal height (43 cm) and hip breadth (45 cm) applied to design the workstation for sewing sack’s operator and the others used to adjust the components of this workstation. The risk assessment by RULA before and after using the probability optimized workstation were 7 and 7 scores and REBA scores were 11 and 5, respectively. Body discomfort-abnormal index was used to assess muscle fatigue of operators before adjustment workstation found that neck muscles, arm muscles area, muscles on the back and the lower back muscles fatigue. Therefore, the extension and flexion exercise was applied to relief musculoskeletal stresses. The workers exercised 15 minutes before the beginning and the end of work for 5 days. After that, the capability of flexion and extension muscles’ workers were increasing in 3 muscles (arm, leg, and back muscles). Keywords—animal feed, anthropometry, ergonomics, sewing sack, workstation design I. INTRODUCTION HAI workmen’s compensation reported in 2008, musculoskeletal disease is the highest occupational diseases (3,407 persons) caused by working postures and overweight lifting [1]. Accordingly, many industries interested in principle of ergonomics. Ergonomics approach to design the conventional workstation balancing between capability of worker and productivity improvement. Furthermore, ergonomics’ design could reduce awkward work posture.Inadequate posture from an improperly designed workstation causes static muscle efforts, eventually resulting in acute localized muscle fatigue, and consequently in decreased performance and productivity, and in enhanced possibility of operator related health hazards [2]. The objective of this study is to design the proper workstation for sewing sack procedure. RULA and REBA are employed to determine work posture before and after using the probability optimized workstation. School of Occupational Health and Safety, Institute of Medicine, Suranaree University of Technology, Nakornratchasima, 30000, Thailand (phone: 664-422-3939; fax: 664-422-3920; e-mail: pirutchada@ sut.ac.th). Department of Occupational Health and Safety, Faculty of Public Health, Mahidol University, Bangkok, 10400, Thailand (e-mail: phwpp@mahidol.ac.th). II.METHODS A. Determination of the Workstation Dimensions The workstation design is using the physical dimensions from the population (2 operators in this process). Anthropometric measures in 7 dimensions are (1) sitting height, (2) mid shoulder height sitting, (3) shoulder breadth, (4) knee height, (5) popliteal height, (6) hip breadth and (7) buttock-knee length, as shown in Table 1. Calculating the physical dimensions for designing workstation: Percentile(r) = r (N+1)/100, the physical dimensions were shown in Table 2. The workstations were presented in figure 1 (the existing workstation) and 2 (the new workstation). Pirutchada Musigapong, Wantanee Phanprasit Workstation Design based on Ergonomics in Animal feed Packing Process T TABLE I ANTHROPOMETRIC MEASURES OF THE POPULATION IN 7PHYSICAL DIMENSIONS Physical dimensions of Worker (cm) Anthropometry 1 st 2 nd Sitting height 123 125 Mid shoulder height sitting 62 61 Shoulder breadth 51 42 Knee height 52 54 Popliteal height 43 42 Hip breadth 45 38 Buttock-knee length 48 46 TABLE II THE 4PHYSICAL DIMENSIONS DESIGN THE PROBABILITY OPTIMIZED WORKSTATION Anthropometry Dimensions (cm) Mid shoulder height sitting 62 Popliteal height 43 Hip breadth 45 Buttock-knee length 51 (46+5) 799 World Academy of Science, Engineering and Technology International Journal of Industrial and Manufacturing Engineering Vol:5, No:5, 2011 914 International Scholarly and Scientific Research & Innovation 5(5) 2011 scholar.waset.org/1307-6892/6418 International Science Index, Industrial and Manufacturing Engineering Vol:5, No:5, 2011 waset.org/Publication/6418