多股螺旋弹簧绕制过程中的动态张力

Dynamic Tension of Stranded Wires Helical Spring during Reeling

多股螺旋弹簧(简称多股簧)是由钢索(通常由2～7股0.4～3.0 mm的碳素弹簧钢丝缠绕而成)卷制而成的圆柱螺旋弹簧,绕制过程中对钢丝张力的一致性控制是保证多股簧的质量关键。按实际成形过程推导多股螺旋弹簧各钢丝中心线的数学模型;提出多股螺旋弹簧各股钢丝在绕簧过程中的动态张力变化理论模型。研究得出多股螺旋弹簧的成形加工质量除了与钢丝本身的质量有关外,还与绕簧的速度、对钢丝产生拉力的部件的转动惯量有关。提出一种多股螺旋弹簧绕制的工艺参数确定和控制方案。结合实际案例,在绕簧过程中钢丝的张力因系统惯性可以产生约20%的控制误差,从而找到了多股螺旋弹簧产品的废品率与拧索速度之间的关系。在上述理论模型的指导下,对原设备只需进行较小的改动,即限制设备主轴的最高转速,产品合格率随即得到较大幅度的提高,这是因为钢丝的张力因系统惯性最大只能产生小于0.6%的控制误差。

The stranded wires helical spring is normally made up of 2 to 7 carbon steel wires that are tied up to form a strand which is then twisted to form a helical spring. It is extremely important to remain consistent tension of individual wires during reeling to assure the quality of a spring. The mathematic models on center lines of wires are put forward. The dynamic tension theory of individual wires is derived. The research concludes that the quality of a spring is related to the wire quality, as well as the velocity of reeling and the moment of inertia that causes the generation of tensional force on individual wires. A scheme on acquiring and controlling the reeling technical parameters of the spring is proposed. According to case study, high reject rate of the stranded wires helical spring is resulted from tension control error up to 20% by system inertia during reeling. The problem is solved by reducing the maximum velocity of the reel, which improves spring qualified rate for tension control error down to 0.6%.