Ergonomic Study, Redesign and Evaluation of Monier/Rabitz Pliers

Abstract

Introduction: Human body is placed in different situations and states when doing work and activity. Depending on the type and severity of these activities, changes the physiological reactions of the body. Now, if it works with a good tool when it is used to maintain the natural state of the body and have a good design, the rate of these injuries will be reduced in the dramatic in people. Research findings show that in the design of manual tools, considering the conditions such as providing grip pinch of suitable for handhold, maintaining the natural condition of the wrist and preventing pressure from the hand tissues can increase the ability to use these tool and with the reduction of pressure on the curry muscles and fingers tendon, they have a significant impact on the safety and health of the user.

Methods: At first, the characteristics of traditional pliers were examined, and user comments were obtained. Then, four plier models were designed based on the recommendations in scientific studies. To this end, work was done by changing the grip span of traditional tongs. The designed tongs were then examined with the traditional tongs. The required sample was determined based on the results of previous studies and based on statistical calculations of 18 persons. The study subjects were selected from male students of Tabriz University of Medical Sciences and advertised in university environment. Each study participant worked with 5 pliers. The selection of pliers was performed randomly for each individual. Influence of ergonomic grip span of Monier/Rabitz pliers, body postures and workpiece orientation as independent variables on the dependent variables such as discomfort, usability and forearm torque were measured and measured. Data were analyzed using inferential statistics by SPSS software.

Results: At maximum torque strength, using of mixed model analysis of variance, the effect of height and direction of work was not statistically significant but was significant of type of pliers. The maximum and minimum values of maximum torque were 40 mm (mean = 5.001) and 60 mm (mean = 5.754), respectively. According to the Sidak post-test results, the mean SUS scores for the 50mm grip pliers (mean = 67.759), which was the same as the traditional pliers, were significantly higher than the other pliers. The most discomfort was reported in the Thenar area (T) and then in the Thumb proximal phalanx (TP) and the least in the Index finger distal phalanx (ID) and the Middle finger distal phalanx (MD). Friedman nonparametric test results showed a significant difference in mean discomfort scores only in the Middle finger distal phalanx (MD) area (p˂0.05).

Discussion & Conclusion: The findings of this study showed that the 50mm pliers had better usability than the other pliers but the maximum torque in the 60mm pliers was better than the others. By summarizing the maximum torque, usability and hand discomfort evaluations, because the 50mm pliers was not rejected in any of these evaluations, and in terms of usability, it achieved better results than the other pliers, the 50mm plier is recommended as the best grip span for Designing.