Wear Research and Improved Design of D-knotter Wiper Mechanism

Abstract

In order to solve the serious wear problem of D-knotter wiper inner cam, firstly, a new structure cam was designed. To be more precise, the original cylinder cam contour was replaced by using the offset arc surfaces of the cam theoretical surfaces, which means the point contact manner of convexity-convexity and convexity-plane was substituted by convexity-concave. Secondly, the surface equations of the improved cam were obtained, and then the pressure angle, initial contact area, initial maximum contact stress were calculated. Thirdly, the original and improved cams were manufactured by the turning and milling machine, which were using the aluminum alloy materials. Finally, a contrast experiment of wear pattern between the original and improved cams was designed, and the results were given by quantitative analysis. The results indicated that the improved cam mechanism reduced the pressure angle by an average of 25% than the original one in the majority of the rise travel. In contrast to the original one, the improved cam mechanism’s initial contact area can increase by approximately 50% and the initial maximum contact pressure decreased by 38%. After 10 hours’ runs of each cam mechanisms, the improved cam exceeds the original one by 31.7% in case of the width of the wear trace, and the abrasion value of improved cam is about 50% smaller than the original cam.

Keywords: Baler machine, D-knotter, Wiper mechanism, Wear, Design