Tool axis control method for impeller tunnel milling using non-orthogonal 4-axis machine

For milling of free-form impeller channel using nonorthogonal 4-axis machine, a tool axis control method was proposed, which interpolated tool axis by rotating it through a revolution axis in a constraint surface. Through analyses of the tool axis constraint conditions, a unit cone which met the constraint conditions was established in work coordinate system. An algorithm was presented to calculate initial tool axis of the clean-up machining, then the interference-free tool axis of every contact point was generated in a clean-up tool path. Sequentially the surface area on the unit cone was calculated, which determined by the corresponding clear-up tool axis, and interpolated clean-up tool axis by rotating it in a same angle on this area to get the tool axis of the impeller channel milling, finally a machine kinematics constraints was established to smooth it. Examples show that the method can calculate the smooth and interference-free tool axis of the impeller channel accurately and efficiently when it is machined by using non-orthogonal 4-axis machine.