Occupational Repetitive Action Research Articles

An exact method to incorporate ergonomic risks in Assembly Line Balancing Problems

Since ergonomic risks related to the tasks performed by each worker are generally neglected when solving the Simple Assembly Line Balancing Problem (SALBP) or partially treated in post-processing, this paper aims to incorporate ergonomic issues natively in the decision process (ErgoSALBP). For such a problem, we present a novel Mixed-Integer Linear Programming (MILP) model that linearizes and incorporates into the SALBP the Occupational Repetitive Action (OCRA). This well-known method gives ergonomic risk indicators for musculoskeletal disorders. A lexicographical approach to address the problem is proposed, where the minimum number of stations is obtained for SALBP and used as a starting point to solve a type-F ErgoSALBP (feasibility problem) focused on satisfying the maximum ergonomic risk workload. Once the exact solution is found, we establish an objective function to smooth the ergonomic risk distribution among stations. We tested a total of 2160 instances with up to 297 tasks. Our method was able to solve 94% of all instances optimally. The share of solutions found with only green stations (the ideal ergonomic condition) was 87%, surpassing the state of the art. For the instances where the model did not converge to a solution within the time limit, we present a procedure to assess the optimality gap. Furthermore, the model can be embedded as a building block for other assembly line configurations. Finally, the results provide trade-off insights for managers: the average OCRA for the line improves as the cycle time increases, which may positively impact workers’ satisfaction and product quality in the long run.

Workload Risk Analysis of the Optimal Packing Division Using RWL, REBA, and OCRA Methods on Musculoskeletal Disorders

Physical work and body posture will be related to the workload obtained, because it will affect production results. Based on the observations of 4 packing operators, there are problems with how they work, so there are some defective/failed to packs products, because some operators complain of fatigue, especially in the hands, back, and feet, and do not focus on one job. From material lifting, and packing processes to cleaning up failed products and products that fall from the conveyor. The methods used are the Recommended Weight Limit (RWL), Rapid Entire Body Assessment (REBA), and Occupational Repetitive Action (OCRA). can find out the level of risk category of each packing operator, and can improve posture/body position and workload carried out, with the aim of improving the workings of the riskiest operators in order to be optimal at work. The results of the study were operators 3 and 4 with higher working risk levels. The workload for operators 3 0.80 ± LI = did not cause any risk to the activity performed and the weight of the load lifted, resultant posture score 9 (very risky), right-handed activity 6.7 (medium risk), and left-handedness 11.9 (very risky). Whereas operator 4 obtained a workload yield of 1.14 li LI, which may increase the risk of complaints of waist pain and weight lifted beyond the standard, posture 6 (medium), right-hand activity 11.2 (high risk), and left hand 6.7 (medium risk).

Analysis Workstation in Manufacturing Industry using Occupational Repetitive Action (OCRA) Index Method to Reduce Risk of Work-Related Musculoskeletal Disorder

Analysis Workstation in Manufacturing Industry using Occupational Repetitive Action (OCRA) Index Method to Reduce Risk of Work-Related Musculoskeletal Disorder

A novel platform to enable the future human-centered factory

This paper introduces a web-platform system that performs semi-automatic compute of several risk indexes, based on the considered evaluation method (e.g., RULA—Rapid Upper Limb Assessment, REBA—Rapid Entire Body Assessment, OCRA—OCcupational Repetitive Action) to support ergonomics risk estimation, and provides augmented analytics to proactively improve ergonomic risk monitoring based on the characteristics of workers (e.g., age, gender), working tasks, and environment. It implements a body detection system, marker-less and low cost, based on the use of RGB cameras, which exploits the open-source deep learning model CMU (Carnegie Mellon University), from the tf-pose-estimation project, assuring worker privacy and data protection, which has been already successfully assessed in standard laboratory conditions. The paper provides a full description of the proposed platform and reports the results of validation in a real industrial case study regarding a washing machine assembly line composed by 5 workstations. A total of 15 workers have been involved. Results suggest how the proposed system is able to significantly speed up the ergonomic assessment and to predict angles and perform a RULA and OCRA analysis, with an accuracy comparable to that obtainable from a manual analysis, even under the unpredictable conditions that can be found in a real working environment.

A design tool to estimate maximum acceptable manual arm forces for above-shoulder work

There is a need for design criteria for above-shoulder work to prevent shoulder fatigue and supraspinatus injuries. A tool is developed to estimate maximum acceptable manual arm forces for above-shoulder work based on 25th % female strength with adjustments for supraspinatus tendon impingement and shoulder fatigue. The tool equations are presented along with tables of maximum acceptable manual arm forces in 77 locations in the 3 D space above the shoulder that accommodates a 50th % female reach. The largest acceptable anterior force, 140.3 N, occurs at shoulder height, 0.5 m anterior to the shoulder. The largest acceptable superior force, 84.4 N, occurs at shoulder height, 0.1 m anterior and 0.2 m medial to the shoulder. The new tool provides design criteria for arm exertions at a higher level of detail than prior ergonomic tools, making it useful for engineers. Based on sensitivity analyses, the tool is robust to parameter assumptions. Practitioner summary: Above-shoulder work is associated with increased risk for shoulder fatigue and injuries. A new tool is developed that estimates maximum acceptable manual arm forces for work at or above shoulder height. The tool can be used to design acceptable above-shoulder work so that it can be accomplished by most workers. Abbreviations: AFF: arm force field; AP: anterior/posterior; DC: duty cycle; GH: glenohumeral angle; HT: humerothoracic angle; LM: lateral/medial; MAE: maximum acceptable effort; MAF: maximum acceptable force; MAS: manual arm strength; MVC: maximum voluntary contraction; N: newton; OCRA: occupational repetitive action; R: reach distance; RMS: root means square; RULA: rapid upper limb assessment; SF: scale factor; SI: superior/inferior; ST: scapulothoracic angle; T: thoracic KEY POINTS A new design tool is introduced that estimates maximum acceptable hand forces for specific locations above the shoulder. This above-shoulder tool is based on a 50th percentile female anthropometry and 25th percentile female manual arm strength. These base strengths are multiplied by scaling factors that adjust for subacromial impingement and fatigue. The tool was shown to be robust based on sensitivity analysis.

De Re Metallica: An Early Ergonomics Lesson Applied to Machine Design in the Renaissance

The Renaissance treatise De Re Metallica (Georgius Agricola, 1556) is one of the first works that deals in detail with the state of the art of metal mining, compiling the main techniques and mechanical devices used in this industrial activity at that time. An advanced knowledge of the human–machine set is observed in this treatise, from a mechanical and ergonomics point of view. The main objective of this work is to carry out an ergonomics analysis of one of the mechanical devices collected in the sixth book of this treatise. It is intended to show that there was a certain concern for ergonomics in the Renaissance, long before the first appearance of this concept. Specifically, a mine water extraction pump, powered by three different systems, is analyzed. Current ergonomics assessment methods have been used to perform this comparative analysis. The postural load has been assessed by the rapid upper limb assessment (RULA) and the rapid entire body assessment (REBA). The Check List OCRA (occupational repetitive action) has been used to perform the analysis of repetitive movements. The results have shown an evolution of the machine, not only on a mechanical level, but also in movements, postures, and safety of the operator for the three methods applied. It is, therefore, an example of practical and real ergonomics applied to machine design dating from the 16th century. In addition, this work may be a very interesting tool for teaching, since it allows showing examples of ergonomics in productive areas related to historical context.

The effect of different work-rest schedules on ergonomic risk in poultry slaughterhouse workers.

BACKGROUND:Rest breaks are an organizational measure to reduce the high risk of upper limb work-related musculoskeletal disorders (UL-WMSDs) to which slaughterhouse workers are subject.OBJECTIVE:To analyze the effect of different work-rest schedules on ergonomic risk in poultry slaughterhouse workers.METHODS:A total of 36 repetitive tasks was selected in a Brazilian slaughterhouse. Using the Occupational Repetitive Action (OCRA) Checklist, the level of exposure of workers to risk factors of UL-WMSDs in two work-rest schedules was evaluated. In the real condition, 6 rest breaks of 10 minutes were performed, and in the simulated condition, 3 rest breaks of 20 minutes.RESULTS:The right side of the body presented a higher score on the OCRA Checklist (72%of the tasks) than the left side (p = 0.037) in the real condition. Additionally, the OCRA score (18.3±2.5) was significantly lower (p < 0.001) than the simulated condition (21.9±3.0). It was verified that the risk level in simulated condition remained the same in 13 (36%) tasks, while in 23 (64%) tasks there was an increase in the risk level.CONCLUSIONS:Work-rest schedule of 6 breaks of 10 minutes was better than 3 breaks of 20 minutes to reduce the risk of UL-WMSDs in poultry slaughterhouse workers.

Exertion Perception When Performing Cutting Tasks in Poultry Slaughterhouses: Risk Assessment of Developing Musculoskeletal Disorders.

Brazil is the leader in poultry meat exports, in which most products are in the form of cuts. This study analyzed the exertion perception of poultry slaughterhouses workers when performing cutting tasks, as well as the influence of knife sharpness on the risk of developing musculoskeletal disorders by Occupational Repetitive Action (OCRA) method. Participants (n = 101) from three slaughterhouses were asked to rate their perceived exertion on the Borg scale during the cutting task when the knife was well and poorly sharpened. The OCRA results showed that the score for cutting with a dull knife was greater (43.57 ± 13.51) than with a sharp knife (23.79 ± 3.10) (p < 0.001). Consequently, there was a significant increase in the risk level of acquiring upper-limb work-related musculoskeletal disorders (UL-WMSD) by using a “poorly sharpened” knife (29%; p < 0.001; Borg scale 2–8). Thus, maintaining well-sharpened knives for optimal performance of the cutting task (fewer technical actions) is suggested, as well as including knife sharpening in the standard operating procedure to reduce musculoskeletal disorders.

IMPROVEMENT OF WORK METHOD TO REDUCE REPETITIVE WORK IN PT. TRIJAYA PLASTIK UTAMA WITH OCRA METHOD

PT. Trijaya Plastik Utama is a company that manufactures raincoats. Based on the results of interviews with workers in 3 production departments, most experienced complaints in the upper limbs, especially the neck, back, and hands. Most of the work does repetitive activities with long cycles, so the nature of the work is suspected to cause musculoskeletal disorders for the operator. This study aims to identify the presence of musculoskeletal risks due to repetitive work using the Occupational Repetitive Action (OCRA) method. Based on the identification results of each department section, the packing section has the highest OCRA index value with a value of 3.86 for the right hand and 3.01 for the left hand. Improvement efforts to reduce risk due to repetitive work is to apply the concept of Eliminate, Combine, Re-Arrange and Simplify (ECRS) and the proposed design of work facilities. As a result, the OCRA index value dropped to 0.95 for the right hand and 0.85 for the left hand where the conditions were optimal

The prevalence of musculoskeletal discomforts and its relation with work posture in Carpet Weavers, Boshruyeh City

Introduction: Carpet industry is one of the most important, dangerous and traditional industries in Iran. Non-Ergonomic factors such as non-standard work tools, inappropriate physical postures, long hours of work and insufficient rest of carpet weavers can lead to musculoskeletal disorders. The purpose of this study was to determine the prevalence of musculoskeletal discomfort and its relationship with posture in rural carpet weavers in Boshruyeh city.&#x0D; Methods: This study is descriptive, analytical and cross-sectional. The sampling method was census-based and included all rural carpet weavers in Boshruyeh city who were active at least 6 months prior to the beginning of the study and were willing to cooperate (62 people). In order to investigate musculoskeletal discomforts, used from Cornell Musculoskeletal Discomfort Questionnaire (CMDQ) and for posture assessment, The Occupational Repetitive Action Index (OCRA) method was used. The collected data by using SPSS software IBM 24 (Pearson correlation test) was analyzed.&#x0D; Results: The results showed that 98.39% of the workers felt discomfort at least in one of the 20 assessed regions. The most common discomfort of carpet weavers was 72.88% in the lower back region and the lowest incidence of discomfort was 9.68% in the hip/buttocks. There was a significant statistical relationship between scores of musculoskeletal discomforts in 11of 20 assessed regions with OCRA score (p &lt;0.05), There was also a significant statistical relationship between age, work hours and work experience with CMDQ score (p &lt;0.05).&#x0D; Conclusions: It seems Insufficient rest, Repetitive work, and incorrect posture are of factors affecting the musculoskeletal discomfort.observe the principles of ergonomics, especially having proper postures and regular rest along with stretching can be helpful in reducing the incidence of discomfort and musculoskeletal disorders.

The comparison of ergonomic risk assessment results using job strain index and OCRA methods

Musculoskeletal Disorder (MDSs) is a real problem in terms of ergonomics. MSD is a muscle/pain disorder which is frequently undergone by operators after doing work, e.g. in the press line of a printing company. Some activities in press line are lifting books, reaching out the engine levers, and turning the engine levers. Many MSDs are undergone by operators, such as aches in the upper arms, hands, feet, and back. This is caused by excessive burdens and wrong posture when doing work. This study is aimed to compare the assessment results of operators’ body posture by using OCRA and JSI methods. OCRA (Occupational Repetitive Action) Index is a method used to evaluate and analyze a job. Meanwhile, Job Strain Index (JSI) is a method used to estimate the risk of pain in the upper body. Evaluation is carried out on repetitive activities. Based on the calculation results, the OCRA values obtained are 3.35 for the right hand and 1.13 for the left hand. Meanwhile, JSI value for the right hand is 9 and the left hand is 4.5. The results of the assessment indicate that these activities are categorized as high-risk so and need to be corrected. The author’s recommendation is by adding the number of operators on the press line.

On the OCRA Measurement: Automatic Computation of the Dynamic Technical Action Frequency Factor.

OCRA (OCcupational Repetitive Action) is currently one of the most widespread procedures for assessing biomechanical risks related to upper limb repetitive movements. Frequency factor of the technical actions represents one of the OCRA elements. Actually, the frequency factor computation is based on workcycle video analysis, which is time-consuming and may lead to up to 30% of intra-operator variability. This paper aims at proposing an innovative procedure for the automatic counting of dynamic technical actions on the basis of inertial data. More specifically, a threshold-based algorithm was tested in four industrial case studies, involving a cohort of 20 workers. Nine combinations of the algorithm were tested by varying threshold values related to time and amplitude. The computation of frequency factor showed an average relative error lower than 5.7% in all industrial-based case studies after the appropriate selection of the time and amplitude threshold values. These findings open the possibility to use the threshold-based algorithm proposed here for the automatic computation of OCRA frequency factor, avoiding the time efforts in video analysis.

Ergonomic diagnosis of postural changes and ergonomic risk assessment of a left-handed user in the operation of a drill press, using the REBA, RULA and OCRA Checklist methods

This investigation is a study aimed at assessing posture and evaluating the risk of musculoskeletal injuries (MSI) in upper limbs of mechanical engineering students at the Universidad Politécnica Salesiana in Quito, Ecuador. Through a descriptive study of ten students with an average age of 19.8 ±1.23 years and average drill-use experience of 1.9 ±1.3 months, ergonomic risk was assessed using REBA (Rapid Entire Body Assessment), RULA (Rapid Upper Limb Assessment), and OCRA (Occupational Repetitive Action) Checklist methods. Previously, Harris and Edinburgh tests were used to evaluate laterality, which resulted in a 100% consistently left-handed population (p&lt;0.05). Upper limb joint angles were measured using photometry and the free software Ruler, establishing a database for ergonomic risk assessment. Next, Pearson’s correlation was used to compare the operator’s laterality with each ergonomic evaluation method. Additionally, other variables analyzed were the operators’ age and their experience using the drill press, which do not contribute to the risk of MSI. In conclusion, a high risk of MSI exists for left-handed users when they operate a drill press, and this risk increases with their degree of laterality.

Future vehicles: the effect of seat configuration on posture and quality of conversation

The percentage of passengers that prefer travelling in groups is increasing. In most vehicles, passengers sit side by side and need to turn their body to be engaged in the conversation with their fellow travellers. However, rotating the body could lead to discomfort which influences conversation quality. The aim of this research is to study the effect of seat configuration on the (dis)comfort experience, conversation quality and posture. Experiments in which participants were asked to talk to each other while sitting at the same distance (1 m) were conducted in four seating arrangements (with seat-belts on), where the angle between the forward directions of two seats were positioned at 0° (side by side), 22.5°, 90° and 120° (almost opposite each other), respectively. Optical tracking has been deployed and the collected data were processed with MatLab® to acquire postural angles over time. Questionnaires were also used to evaluate the perceived (dis)comfort and the quality of the conversation. Experiment results indicate that the 120° configuration scored the best in the overall comfort and the quality of conversation, but only slightly better than the 90° configuration. Practitioner summary: Seating side by side is not optimal to have a comfortable conversation with your seatmate. To improve comfort and quality of conversation in future vehicles, we tested four seating arrangements analysing the effect of seat layout on (dis)comfort experience. Statistical analysis of objective and subjective data shows the optimal configuration for a comfortable conversation. Abbreviation: LPD: localized postural discomfort; PDF: probability density function; OCRA: occupational repetitive action

The Risk Assessment of Repetitive Strain Injury (RSI) Disorder Using Occupational Repetitive Action (OCRA) Index Method

Problems that are often encountered in the workplace, especially those associated with obstacles in carrying out their work is a complaint of Repetitive Strain Injuries. Most problems frequently encountered in this workplace are associated with fatigue in carrying out their work. During the production process, the whole employees use their upper body. Results of questionnaire to workers using the method Nordic body map indicated that the complaints of pain in the left right upper arm are 93%, 93% of the right and left forearm, 93% for the left right wrist, 84% for the left right shoulder. This research uses the OCRA (Occupational Repetitive Action) method. The OCRA method is a quantitative method for the workings used in specific repetitive work. The results of this study are the types of jobs that are at high risk of recurrent strain injury, determining the major use of behavioural repetitive action behaviour (OCRA) and addressing work issues that may cause disturbance of repetitive strain injuries.

Método OCRA en diferentes sectores productivos

Los desórdenes musculo esqueléticos (DME) son la nueva epidemia de enfermedades crónicas, son multifactoriales y afectan los diferentes sectores productivos. Aunque se encuentran múltiples instrumentos para la evaluación de la carga estática y dinámica, el OCRA (Occupational Repetitive Action) parece ser una opción atractiva. Objetivo. Realizar una búsqueda de literatura sobre el uso del método OCRA y DME en trabajadores de diversos sectores productivos (2007- 2018). Materiales y métodos. Una revisión de literatura (siguiendo la declaración PRISMA) de estudios que evaluaran el nivel de riesgo biomecánico (OCRA) y DME en las bases de datos Scielo, Science Direct, Scopus, ProQuest, Gale, PubMed, Lilacs y Ebsco fue realizada, 7 estudios cumplieron con los criterios de selección; la mayoría son cuantitativos (corte transversal). Resultados. El 79% de las condiciones relacionadas con la tarea requieren exigencia física e implican movimientos repetitivos (jardinería y floricultores); la aparición de DME en espalda alta-baja, extremidades superiores e inferiores, los cuales se generan por la frecuencia de las actividades realizadas (producción de calzado); además, “riesgos muy alto” de desarrollar DME (industria del salmón) y un índice medio (OCRA) por movimientos repetitivos que requiere cuidado especial (línea de Ensamblaje en U) fueron encontrados. Conclusiones. La revisión arrojo el uso limitado del método OCRA para la detección de DME en trabajadores de diferentes sectores; y este método puede ser usado para la detección del riesgo biomecánico.

The problem of assigning rest times to reduce physical ergonomic risk at assembly lines

Line balancing and job rotation have been recently found to be effective methods to reduce workers’ ergonomic risks since the design/planning phase of assembly lines, and at the same time to limit performances deterioration and/or costs increments. As far as we know, there are no papers in the literature that deals with the problem of assigning rest times to workers in assembly lines with the aim to reduce their ergonomic workload. In the paper the problem of assigning rest times to workers in assembly lines is considered (Rest Time Assignment Problem). We show how rest times assignment affects ergonomic risk of workers in mixed-model assembly lines when this is evaluated through the Occupational Repetitive Action index (OCRA), and suggest and approach to simultaneously find solutions for the Assembly Line Balancing Problem and the Rest Time Assignment Problem.

An ergonomics solution in the footwear industry: the footwear unmold

The aim of this work was to analyze the influence of the implementation of ergonomic measures in the work conditions of the cemented assembly section in the unmold activity in a shoe industry located in the state of Paraíba. To do so, a comparative analysis related to the ergonomic improvements previously implanted in the workstations of the company was carried out, looking to verify whether the application of those measures had influenced or not the work conditions in the assembly section mentioned. Historically, that type of industry doesn't have a culture of Prevention of Accidents and Ergonomics in its practices. Consequently, the elevation of the number of acquired diseases related to the work in that section was observed. As methodological procedures, interviews were accomplished with workers of the Assembly Section of the company, aiming to make the measurement of the work conditions, starting from the application of the methodology Situation, Problem and Improvement (SPI) and of the method Occupational Repetitive Action (OCRA), Gravity, Urgency and Tendency (GUT) and the diagram of painful areas of Corlett et Manenica (1980). As a result, improvements of the work conditions were evidenced with the elimination of most non-ergonomic conditions in the activity, besides making possible larger motivation and better life quality to the employees of the studied section.

Ergonomic Analysis of the Work Condition in Aluminum Crafts Industry

Indonesia has plenty of abundant natural wealth. This natural wealth produces natural materials that can be utilized as a craft product. The craft workers generally still work manually and the work is done repeatedly in one cycle so it is very susceptible to musculoskeletal disorders. Musculoskeletal disorders will cause decrease of worker’s effectiveness and efficiency in completing the task. Thus, this fact has some adverse impact for the company. The purpose of this study is to analyze some task in manufacturing a traditional cooking tool (griddle) which encompasses mold of the griddle, refine of the griddle and the finishing touch by using the Occupational Repetitive Action Index (OCRA index) method. This method consists of high frequency movements, large forces, awkward postures, insufficient resting time and other factor such as vibration. Result of this study shows that in the molding operation, the worker has uncertain and medium risk on right hand in manufacturing small and large size of griddle with OCRA index is 2.5 and 5.3 respectively. In the refining operation the worker has light and medium risk on left hand in manufacturing small and large size with OCRA index is 3.6 and 5.8 using grinding machine and 5.8, 5.2, 6.3 and 5.0 using miser tool. In finishing operation, the worker has high risk on right hand in numbering of code griddle and has medium risk on right hand and medium on left hand in labeling with OCRA index is 9, 6.1 and 6.8 While in assembling operation the worker has no risk. Score that it indicates the risk level of the task in such job. Thus the following actions are to improve the work condition ergonomicly in all operation in alumunium craft.

Cognitive status and repetitive working tasks of low risk

Industrial working environment demonstrates important advances in terms of working conditions. Nevertheless, there are still present manual tasks with high frequency, namely, repetitive tasks. This kind of working tasks are among the most influential for workers’ psychological and myoskeletal health. The concern for the risk derived by the repetitive task is evident by the fact that there is a well-known technical standard dedicated to this named OCRA (Occupational Repetitive Action). The present study uses OCRA for categorizing the risk produced by a replicated real repetitive task in laboratory conditions, and then compares electrophysiological method for deeper investigating into workers’ psychophysiology. The study combines results from OCRA and Electrodermal Activity (EDA) and offers suggestions for work design experts to consider psychophysiological impact metrics derived from low risk repetitive tasks.