拉刀螺旋前刀面刃磨砂轮安装姿态计算方法

Wheel Orientation Calculation for Helical Rake Flank Sharpening of Broaching Tool

为了精确地对拉刀螺旋前刀面进行刃磨并保证良好的加工质量,提出了一种砂轮安装位置及姿态的计算方法。该算法通过空间包络原理计算砂轮磨削接触线,并给出接触线分布位置约束,以两个接触点进行前角定义,从而将满足磨削工艺要求的砂轮安装位置和姿态求解转换为一个非线性方程。然后,根据前刀面螺旋角分布规律指出,砂轮的安装摆角应远离前刀面对应的螺旋角范围,从而将该非线性方程转换为两个单变量的搜索问题,通过牛顿-拉夫逊等方法实现快速求解。研究结果表明,较大的砂轮尺寸或砂轮安装摆角对应较大的砂轮安装倾角,因此建议采用贴近前刀面螺旋角的砂轮安装摆角以回避刃磨中砂轮与前一切削齿之间的干涉。基于VERICUT的仿真结果证明,该方法计算出的砂轮安装位置与姿态能够保证螺旋前刀面得到准确磨削。

To achieve accuracy of rake angle and ensure the grinding quality of the rake flanks of broaching tools, a novel wheel orientation and position calculating method is proposed, the contact curve is identified following the enveloping theory, and its distribution constraints are obtained. Defining the rake angle by two contact points, the wheel orientation evaluation is transformed into a nonlinear equation, which is further resolved as two single-variable searching problems obeying the principle that the swing angle of the grinding wheel ought to depart away the helix angle. Thus this equation can be easily solved by Newton-Raphson method. The results indicate that either larger radius or larger swing angle of the wheel corresponds with a larger tilt angle, and a swing angle close to the helix angle of rake flank is suggested to avoid the interference between the grinding wheel and front cutting teeth. A VERCUT based simulation verifies that the wheel orientation and position from this proposed method can ensure grinding precision of the helical rake flank of broaching tool.