Ergonomics research strives to make workers' labor more efficient, safer, and more comfortable. Therefore, six digital humans and welding torch model were built and evaluated based on the Jack software in order to improve the ergonomics of welders' standing postures. Three sets of standing welding actions were designed: walking, raising arm, and contracting arm. Through the Lower Back Analysis, Ovako Working Posture Analysis, Comfort Assessment, and Rapid Upper Limb Assessment, this paper evaluated the optimum range of the weight of the welding torch, the upper limb posture, and the neck posture of the welder. Firstly, the results show that Chinese welders should not use a welding torch with a weight of more than 6 kg when standing up. Secondly, for adult males in the 5th, 50th, 95th percentile of body size, the best operating distance is 321 mm, 371 mm, and 421 mm, respectively, and the best operating height is 1050 mm, 1100 mm, and 1150 mm, respectively; for females in the same percentiles, the optimal operating distance is 271 mm, 321 mm, and 371 mm, respectively, and the optimal operating height is 1000 mm, 1050 mm, and 1100 mm, respectively. Moreover, the horizontal and vertical rotation angle of the welder's neck should not exceed 15° and 8.7°. The adjustment strategy not only has a positive effect on improving welders' operational posture and preventing fatigue and injury to the welder, but it also develops research ideas for promoting safety from the perspective of ergonomics.
Keywords: Jack software; adjustment strategy; ergonomics; welders’ standing posture.