European Journal of Scientific Research ISSN 1450-216X Vol.30 No.2 (2009), pp.224-235 © EuroJournals Publishing, Inc.2009 http://www.eurojournals.com/ejsr.htm Assessment of Postural Loading among the Assembly Operators: A Case Study at Malaysian Automotive Industry A. R. Ismail Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, National University of Malaysia 43600 UKM Bangi, Selangor, Malaysia E-mail:
[email protected] Tel: +603-89216775; Fax: +603-89259659 M. L Yeo Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, National University of Malaysia 43600 UKM Bangi, Selangor, Malaysia M.H.M. Haniff Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, National University of Malaysia 43600 UKM Bangi, Selangor, Malaysia R. Zulkifli Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, National University of Malaysia 43600 UKM Bangi, Selangor, Malaysia B.M. Deros Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, National University of Malaysia 43600 UKM Bangi, Selangor, Malaysia N.K. Makhtar Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, National University of Malaysia 43600 UKM Bangi, Selangor, Malaysia Abstract Many occupational tasks in industrial are still associated with strenuous working postures and movement. Combined with a heavy physical workload, they result in a high frequency of work-related musculoskeletal disorders (WMSDs). The intention of this study is to reveal the empirical study of discomfort experience by the operators during performing the task at the Malaysia automotive industries. The OWAS (Ovako Work Assessment System) tool is used in order to assess the area of discomfort reported by the 593 different postures were analysed and a total 7. Introduction Musculoskeletal disorders have proved to be a major problem for modern industrialized countries (Markku Mattila et al. The symptoms of WMSDs are discomfort. (1993) were analyses the working postures in hammering task on building construction sites by using the computerized OWAS method. back. stiffness. 1993).8% of postures adopted by the workers during various hammering tasks were classified into OWAS categories III or IV. the computer programs show the detailed about the distribution of posture observations into categories in need of corrective measures.Hoy et al (2004) also clarify a worker friendly workplace can generate short term advantages such as cost reduction and productivity improvement as well as long term benefits from increased employee motivation and reduced staff turnover.5 hours per task. According to their study.Saraji et al. ergonomic risk factor due to repetitive work or prolong standing and shift work. From their finding. Manufacturing Industry is playing an important role on economic development in Malaysia. P. From the analysis result. static load. the occupational health issues common to construction workers.8% of cement worker were category in poor work postures and which need to be corrected soon or immediately. fatigue. The computerized OWAS method for postural data analysis proved to be a very useful way to reduce postural load of dynamic hammering task. Posture. OWAS analyses are able to detect the awkward posture. OWAS posture analysis method been done and new optimum posture is created for the awkward posture. numbness and tingling (Oregon OSHA. contact stress. Optimum.N. Markku Mattila et al. There are many researcher studies on the discomfort working postures by using different methods. 2007). design of workstation and also improving the work posture to increase the comfort level of operators. 27. it indicating that the postures should be corrected either soon or immediately. Kivi and M. automotive workers and steel industry workers are manual handling that causes body strain and pain. vibration. Based on the Occupational Safety and Health (OSH) profile in various sectors in Malaysia. pain. work environment or the equipment used at work and correct work postures were suggested to minimize the WMSDs problems. Several researches have shown that the application of ergonomic principles and programs in almost all workplaces result in increasing productivity and decreasing WMSDs (J. Several physical risk factors for WMSDs can be identified in working life such as postures. reduced absence due to sickness and reduced insurance costs.Mattila (1991) said that the OWAS analysis provided the opportunity to compare the jobs studies according to the number of postures which need to be corrected soon or immediately. The results of analysis were used to improve the method of work.Kivi and M. trunk. swelling. the parts of the body most affected were upper extremities. 1. manual handling high peak load. speed or acceleration of movement (Pinzke and Kopp.Mattila (1991) were also analyses and improved the work postures in the building industry by using the computerized OWAS method. One optimum working posture is achieved at the end of this research in order to increase safety level and to avoid discomfort occur. The total 6457 postures were observed and the observations were always made at 30 second intervals and the total observation period was about 1. J. 2001). Besides. Besides. repetitive work. Their also clarify that for the workers using the non-powered tools during their work. OWAS. 2004). The working posture is modeled in the WinOWAS software and the analyses will be done respectively. 225 Keywords: WMSD. head and neck. lower extremities. a comparison among work discomfort survey questionnaire.Assessment of Postural Loading among the Assembly Operators: A Case Study at Malaysian Automotive Industry operators by filling the survey questionnaire prior than the analysis being done. Some corrective measures on work redesign. . the result may help to improve the working posture and to minimize the WMSDs. back and leg which are 22.6% and 28. OWAS seeks to identify postures.Lambe (1996) clarify the potential for musculoskeletal discomfort or injury can be related to the amount of time spent in a particular position. For driver. Similarly. Base on the code numbers for each limb. Ismail.226 A.9% of workers were related in low back pain. The aim of their studies is evaluation of WMSDs symptoms among the workers by using Nordic Musculoskeletal Questionnaire (NMQ) and determination of WMSDs risk factors by application of OWAS. According to Graham B. motorists and boatswains were rated in action category 3 of OWAS. In applying the technique. After determination of risk factors. If category it to the different job. The first three cells is to code the number of postures. chief officers. M. seamen and cooks were rated in action category 2 of OWAS.K. For captain also showed highest rate of symptoms at low back. which put the body in positions where force exertions can be dangerous. (2004) were evaluation of WMSDs risk factors among the crew of the Iranian Ports and shipping organization’s vessels. deck officers and wheelmen in action category 1. For chief engineers.7% in ankle and 27.N. 26. Postures of chief engineers.6% in category 3 (distinctly deleterious effect) and 8. risk factors that resulted to MSDs symptoms in shoulder region were cause by the awkward postures and excessive workload during most of working time. Through the finding from the OWAS assessment. L Yeo. Deros and N. J. This paper clarify the WMSDs are major problem in almost all countries and are important causes of work incapacity and loss of work days.Figure 1. it meant that their postures were harmless for musculoskeletal system.3% have MSDs symptoms in elbow. 29. the highest prevalence of MSDs symptoms among all participants. the fourth cell is use to code the load or force used and the final two cells is use to code the stage in the cycle or task.8% in feet. According to the result get from OWAS system. 19. R. The OWAS results rated postures of captains.6% respectively.7% of working hours crew had a posture that was related in action category of 1 (no harmful effect). According to their finding from the Nordic Musculoskeletal Questionnaire. an action category value is then determined.0 had shown the example of OWAS technique for forklift driver.M. there are 32.4% in knee pain and 18. R.Hoy et al.Scott and Nicola R. dredger offices.8% related in shoulder pain.H. 32. climbing on the perches was considered extremely uncomfortable during the exercise.Saraji et al. . 30. chief officers and motorists rated in action category 3 of OWAS and dredger officers. the result show that 33. M.M. If considering the working hours. Zulkifli. the OWAS methods can be used to identify any possible correction in working posture that leads to a better and less harmful posture.9% in category 2 (some harmful effect). Their studies were investigated the working posture in a manual collection of eggs by using OWAS method. Postures of electrician officers. postures are recorded according to a coding system.8% in category 4 (extremely deleterious effect). B. bending to inspect nest boxes can potentially cause posture discomfort and strain. Makhtar J. (2005) were clarified that the postural analyses were conducted by using the OWAS and RULA techniques.3% in shoulder.9%. which meant that preventive measures should be taken as soon as possible. in 33. 37. Haniff. Method Generally. . Observation of the Motion and Work Task After accomplish data compilation from the survey questionnaire. which are collecting data about the work discomfort from the workers and observation of work tasks and working postures. total distance of lifting and the cycle time of one complete work task. observer needs to know the work task perform by the worker and their motion such as reach. 2007). One of the workers with higher percentage of pain or discomfort during work will be choose as our study subject. Al. Before start collection data.1. the methods of this study can category in four. 2. move position and release (Santos et. Record each work phases need to go through by the worker to form one complete work task. identify the awkward postures and give a recommendation of new working postures to minimize the WMSDs problem. observer needs to identify the total load lifting. Figure 1 show the step of the methods use in this study.Assessment of Postural Loading among the Assembly Operators: A Case Study at Malaysian Automotive Industry Figure 1: OWAS technique for forklift driver 227 2. Before the ergonomic study. grasp. analyze the posture data by using software. 1991. It has 252 (4 x 3 x 7 x 3) posture and load combination. R. Makhtar Make sure subject performs their job according to the work task and the time is not longer than the original cycle time. Table 1 shows the OWAS postures code definition.5 m from the subject to ensure a full view of body segment (Karwowski and Marras. B.M.228 A. Figure 2: Flow diagram for the methods of the study. Data Analysis by Using OWAS Method The OWAS method is collects observation information on worker postures on back. because that is often too hard for the observer to use shorter intervals (Kivi and Mattila. Zulkifli. arms and legs. R. the video recorder can also easily and effectively be used in recalling the actual work situation.3. Observer should maintain the recording distance around 4.M.2.K. Each posture of the OWAS is determined by the four digit code in which the numbers indicates the postures of the back. Ismail. . M. Postures Data Collection by Using Video Recorder Subject working postures will be record by using video recorder. M. 2003). three arm postures and seven leg postures with three estimate loads. Saurin and Guimaraes. L Yeo. 2. Work Discomfort Survey Identify the level of work discomfort on the subject Observation Observe the working postures and work tasks on the subject Data Collection Video recorder method Data Analysis Use OWAS methods Result Comparison Identify the awkward postures Recommend an optimum posture 2. Deros and N. the arms and the load needed.H. Haniff. The advantage of using video recorder is that the observer has much time to look at the observed postures. 2006). Besides. The observations are always made at 30 seconds or 60 seconds intervals between observations. which are combination of four back postures. Observer need to identify OWAS posture code of each selected posture from the video image for each work task. knee bent Kneeling on one or both knee Walking or moving Load < 10kg 10 < Load < 20kg Load > 20kg OWAS code 1 2 Back 3 4 1 Arm 2 3 1 2 3 Leg 4 5 6 7 1 Load Handle 2 3 Resource : (Karwowski and Marras. Prolong time spending in one particular posture may cause musculoskeletal injury. The action categories for each individual postures are presented in Figure 2 and explanation about OWAS action categories for prevention shows at Table 2. . knees bent Standing or squatting on one foot. WinOWAS software will be use to identify the OWAS action category. the next analysis is identifying the OWAS action category by calculate the total time spent in different postures for each body part for one complete work task. Therefore.Assessment of Postural Loading among the Assembly Operators: A Case Study at Malaysian Automotive Industry Table 1: Body parts 229 OWAS postures code definition Description of position Back straight Back bent Back Twisted Back bent and twisted Both arms below shoulder level One arm at or above shoulder level Both arms at or above shoulder level Sitting Standing on both straight legs Standing on one straight legs Standing or squatting on both feet. then the action category indicates the need and urgency for corrective actions. 2003) The each OWAS posture code then will be analysis by using the individual OWAS classified posture combination to get the action category for each work phases. If the risk for musculoskeletal disorder is high. The classification for individual posture combination indicates the level of risk injury for the musculoskeletal system. H. Ismail. 2. Recommend an Optimum Working Posture After identify the awkward postures bring discomfort and pain to the worker. Resource : (Karwowski and Marras.5.K. Identify the Awkward Postures by Using the Result from OWAS Analysis The result from OWAS analysis will be use to identify the awkward postures. R. the levels of action category for both methods give a guideline to the observer whether the working postures are in harmful or not and whether it needs to be change immediately or not. From OWAS action category. Makhtar Figure 3: Action category for each individual OWAS classified posture combination 1 Back Arms 2 3 4 5 6 7 Legs Load Handled 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 1 1 2 2 3 1 2 2 2 3 4 1 1 1 2 2 3 1 2 2 3 3 4 1 1 1 3 3 4 1 3 3 3 4 4 1 1 1 2 2 2 1 1 1 2 2 2 1 1 1 2 2 2 1 1 1 2 3 3 1 1 1 3 3 3 1 1 1 3 4 4 1 1 1 2 2 3 1 1 2 2 3 3 1 1 1 2 3 3 1 1 3 2 3 3 1 1 1 3 3 3 2 2 3 3 4 4 2 2 2 3 3 3 3 4 4 4 4 4 2 2 2 3 4 4 3 4 4 4 4 4 2 2 3 3 4 4 3 4 4 4 4 4 2 2 2 3 3 4 4 4 4 4 4 4 2 2 2 3 4 4 4 4 4 4 4 4 2 2 3 3 4 4 4 4 4 4 4 4 1 1 1 2 3 4 1 3 4 4 4 4 1 1 1 2 3 4 1 3 4 4 4 4 1 1 1 2 4 4 1 3 4 4 4 4 1 1 1 2 2 2 1 1 1 2 2 2 1 1 1 3 3 3 1 1 1 3 3 3 1 1 2 3 4 4 1 1 1 4 4 4 1 1 2 3 1 2 2 3 1 3 2 3 1 4 2 3 Number 1 to 4 in the box show the OWAS Action Category 1 – Category 1 2 – Category 2 3 – Category 3 4 – Category 4 Table 2: The OWAS Action Categories for prevention Explanation Normal and natural postures with no harmful effect on the musculoskeletal system – No action 1 required Posture with some harmful effect on the musculoskeletal system – Corrective actions 2 required in the near future Postures have a harmful effect on the musculoskeletal system – Correction actions should be 3 done as soon as possible The load caused by these postures has a very harmful effect on the musculoskeletal system – 4 Corrective actions for improvement required immediately. L Yeo. R. Besides. 2003) Action Category 2. Zulkifli. The new recommend will be analysis again by the using CATIV V5 R16 to get the optimum working posture. recommend an optimum working postures to minimize the WMSDs problem.4.M.M. M. M.230 A. we can identify which body segments bring discomfort or pain to the worker. B. Haniff. The discomfort posture will be change by changing the posture positions. Deros and N. . It was indicate that posture 7 have a harmful effect on the musculoskeletal system and corrective actions should be done as soon as possible. OWAS Action Category for each Individual OWAS Classified Posture Combination Table 4 shows the result of OWAS action category for each posture.2. Figure 3 shows the nine postures selection from the original video image and table 3 shows the activities of the nine postures. except posture 9 all postures were assigned in action category 2 and it indicated . the total movement distance is 0.70 kg Subject start to turn and twisting the body to transfer the cutting products to the wooden box Subject transfer the cutting products to the wooden box. Postures Selection from the Original Video Image Nine postures will be select from the original video image to put into the frames.1.Assessment of Postural Loading among the Assembly Operators: A Case Study at Malaysian Automotive Industry 231 3. OWAS Analysis (a). In additional. Figure 4: Selected frames from the original video image Posture 1 Posture 2 Posture 3 Posture 4 Posture 5 Posture 6 ` Posture 7 Posture 8 Posture 9 Table 3: Activities subject for each posture Activities Subject hold and arrange the cutting products cut from the roll forming machine Subject grasps a total 9 pieces cutting products with the load 0.91 m Subject start to bend down and put the cutting products into the wooden box Subject bends down and put the cutting products into the wooden box Subject arrange the cutting products at the wooden box Subject start to turn back to the roll forming machine after finish arrange the cutting products Subject turn back to the roll forming machine. Results and Discussions 3. the total movement distance is 0.91 m Postures 1 2 3 4 5 6 7 8 9 3. M. Makhtar these postures with some harmful effect on the musculoskeletal system and corrective actions required in the near future. Ismail. 2007) . the subject was standing 56 % of the time on one straight leg. B.M. Also.H. Figure 4 shows the posture observed during handling the cutting products from roll forming machine to wooden box.232 A. All these postures were classified either as categories 2 or 3.K. R. Table 4: Posture 1 2 3 4 5 6 7 8 9 OWAS action category for each posture OWAS Code Leg 2 2 7 3 3 3 3 3 7 Action Category 2 2 2 2 2 2 3 2 1 Back 4 2 4 4 2 2 4 4 1 Arm 2 1 1 1 1 1 2 1 1 Load 1 1 1 1 1 1 1 1 1 Work Phase 0 0 1 1 1 1 2 3 3 (b). Deros and N. Figure 4 illustrates that the back and legs were in the most awkward postures during transfer the cutting products and arrange into the wooden box. OWAS Action Category with Calculated the Total Time Spent in Different Postures for Each Body Part Figure 5: Posture observed during handling cutting products from roll forming machine to wooden box (WinOWAS software. Haniff. Zulkifli. Observations also revealed that back being bent and twisted 56% of the time and bent 33 % of the time.M. M. R. L Yeo. Posture 7 for stage 1 was classified into OWAS action category 2. The results show that the operator are work in an inadequate working environment with awkward postures. 4. Posture 7 for stage 3 at table show the subject back bent above the red color line.5% operator . It assigned OWAS code 4231 and classified into action category 3. It assigned OWAS code 4331 and classified in action category 3 also. knee. but it assigned in OWAS action category 2. Although posture 7 at stage one angle back bend larger than posture 7 at stage two and three. Subject need bend down more to reach the base of the wooden box. Whereas for stage 3. Posture 7 for stage 2 at table show the subject bent and almost aligns with the red color line. Posture Assessment for Posture 7 at Three Stages Figure 6: OWAS code for posture 7 at three stages Stage Posture Back OWAS Code Arm Leg Load Action Category 233 1 2 2 2 1 2 2 4 2 3 1 3 3 4 3 3 1 3 Stage one was represent the product quantity in the wooden box is empty (0 piece). it represents the product quantity in the wooden box is half (900 pieces).Assessment of Postural Loading among the Assembly Operators: A Case Study at Malaysian Automotive Industry (c). If consider about the percentage of times. Transfer the products and arrange at the wooden box involved the poor postures and high motion repetitiveness. thigh and shoulder. It can be clarified that posture 7 at stage one back bent without twisted but posture 7 at stage two and three bent and twisted. For stage 2. Posture 7 for stage 1 at figure 5 shows the back bent below the red color line and assigned OWAS code 2221. Conclusion This study presented an ergonomic assessment of the operators of manual handling in automotive industrial. It indicates this posture with some harmful effect on the musculoskeletal system and corrective actions required in the near future. Regarding to the work discomfort survey questionnaire. posture 7 at stage one. 62. It indicates that this posture has a harmful effect on the musculoskeletal system in long duration and corrective actions should be done as soon as possible. This posture has a harmful effect on the musculoskeletal system and corrective actions should be done as soon as possible. two and three are consider in action category 3. it represents the product quantity in the wooden box is almost full (2300 pieces). majority operators are complaint severe pain at lower back and foot and next is lower leg. Cornell Musculoskeletal Discomfort Questionnaires (English). B. Osteoarthritis and Catilage 11: 499-507 J. 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