ارزیابی ارگونومیک کتابچه راهنمای طرح انبر کلکو: اثرات گرفتن لاستیک، بحال خود برگشتن فنر،زاویه سطح کار

The present study evaluated two design modifications (rubber grip and torsion spring) to the conventional manual Cleco pliers by electromyography (EMG), hand discomfort, and design satisfaction. This study also surveyed workers’ satisfaction with selected design features of the pliers for ergonomic improvement. A two-way (plier design×worksurface angle) within-subject (nested within gender and hand size) design was employed. Eleven workers simulated the plier task in an adjustable workstation for different plier designs and worksurface angles (0°, 60°, and 90°). Lower EMG values were obtained for the pliers with rubber grip and at 60° of worksurface angle. EMG values varied significantly between the participants, but showed low correlations (Spearman's rank correlation=−0.27∼−0.58) with their work experience with the pliers. The hand discomfort and design satisfaction evaluations identified that the grip span (max=14.0 cm) and grip force requirement (peak=220.5 N) of the current pliers need ergonomic modification. The present study shows the needs of both the ergonomic design of a hand tool and the training of a proper work method to control work-related musculoskeletal disorders at the workplace

To operate manual Cleco pliers (Fig. 1), a common hand tool used in aircraft manufacturing, workers often use high grip forces along with non-neutral postures of the upper extremity. Made of forged steel and plated with nickel, the pliers consist of a pair of jaws and handles, crossed along the center of rotation. By using the pliers, a Cleco fastener is installed to hold aircraft skins and frames together temporarily; the head of the fastener, loaded with a stud and spring (spring View the MathML sourcecoefficient=771.3N/cm and View the MathML sourcedisplacement=0.6cm), is secured in the jaws and then pressed for installation. For complete compression of the fastener head, at least 220.5 N of peak grip force (measured by a strain gauge in this study) must be applied to the plier handles. In addition to the high grip forces, awkward postures at the hand/wrist and shoulder (ulnar deviation and shoulder elevation) are often used for work at certain heights and angles of skins and frames (Kumar, 2001). Research has found that repetitive gripping with high forces and improper postures may significantly increase the risk of work-related musculoskeletal disorders at the upper extremity (Bernard, 1997).To prevent upper extremity musculoskeletal injuries due to repetitive, prolonged use of Cleco pliers, ergonomic modification of the pliers is needed. The conventional pliers have been used at the workplace for more than 50 years without design improvement. Bevan (1996) lists problems of the conventional plier design, which include the handle opening being too wide, handle geometry causing deviated hand/wrist postures, and handle texture lacking sufficient friction. No follow-up study, however, has been conducted to examine the potential effects of ergonomic design changes for the pliers. The goals of the present study were to: (1) evaluate the effectiveness of two design modifications (rubber grip and spring recoil) to the conventional pliers and (2) identify design features of the pliers requiring ergonomic modification. Three measures (EMG, hand discomfort, and design satisfaction) were employed to evaluate the two design additions and workers’ satisfaction was surveyed for selected design features. Based on the ergonomic evaluation of the pliers, design recommendations were provided for manual Cleco pliers for better comfort, productivity, and health of the users at work.

An ergonomic analysis on the conventional manual Cleco plier design was conducted with industrial workers by using physiological and psychophysical measures. Rubber grip and spring recoil were added to the conventional pliers. Eleven workers having different hand sizes and at least 1 year of experience with the pliers simulated the plier task with different plier designs at different worksurface angles in a laboratory setting. EMG, hand discomfort, and design satisfaction were measured to identify desirable ergonomic improvements necessary for the pliers. Based on the evaluation results, ergonomic recommendations for the plier task include: • Use rubber grip on the handles. • Provide multiple handle sizes with proper grip spans for hands in various sizes. • Reduce the peak grip force (View the MathML source=220.5N) required for complete compression of the fastener head. • Use an adjustable workstation for worksurface height and angle. • Develop a standard work method and training system.