Investigation on shaping machining method for deep hole keyway based on on-line symmetry detection and compensation

Machining of deep hole keyway often suffers from low processing accuracy, low processing symmetry degree between keyway and the reference plane and is difficult to control. In order to enhance the processing quality, a mathematical model of space symmetry error was established based on space projection, orthogonal combination and linear fitting methods so as to study rotatable and shift-able space objects. The space symmetry error was separated into included angle error and displacement error between the fitting straight line and the benchmark line. Through included angle rotation and location measurement along with quantitative translation, the space symmetry error compensation was realized. On the basis of the proposed methods, a Double combined manual self-centering fixture (DCMSF) was designed to realize the radial self-centering and axial location for effective clamping of deep hole keyway, and the reference plane of built-in straight slot was derived out to make it detectable and controllable. Meanwhile, an Online multi-degree of freedom symmetry detection device (OMFSDD) and corresponding Numerical control (NC) programs were also designed for automatic detection and control of symmetry error. Subsequently, mass production of high symmetric deep hole keyway were realized by means of NC gear shaper servo control of rotating shaft angle compensation and bi-directional cutter back-off amount translation compensation, and combination of NC control of fixed angle processing. Deep hole keyway processing experiments indicate that the proposed method can steadily keep the symmetry within 0.03 mm. Thus, the rationality and accuracy of the proposed method was validated which provides a novel approach to high precision deep hole keyway processing.