A Cylindricity Error Evaluation Algorithm Based on Mechanical Thinking

When using photogrammetric method to measure axial forgings, it is impossible to measure the points' coordinates of the same section or spiral line, so the conventional method to evaluate the cylindricity error can't be used. In this paper, a cylindricity error evaluation algorithm based on mechanical thinking is proposed. The measurement points which are near the same shaft parts are divided into a group and projected onto the fitting surface of the bottom of shaft parts. Each group of projected points can do ellipse fitting to obtained the center coordinates. The initial axis equation is obtained through two sets of point coordinates which are the mean value of the coordinates obtained on the bottom surface. Different from grid method and genetic algorithm, the optimal axis equation is obtained by adjusting the axis equation in the corresponding direction based on the mechanical thought and the operation speed is accelerated by changing step length. Experimental results show that this method is equivalent to the traditional measurement method, besides it's simple and efficient without tedious process on measuring the points.