# Twin-Tool Orientation Synchronous Smoothing Algorithm of Pinch Milling in Nine-Axis Machine Tools

## TL;DR

This paper introduces a new algorithm for twin-tool orientation in nine-axis machining to improve blade quality and efficiency.

## Contribution

A novel twin-tool smoothing orientation algorithm for pinch milling on nine-axis machine tools is proposed.

## Key findings

- The algorithm generates smooth and stable tool orientations for thin-walled blades.
- It avoids collision interference and improves machining accuracy for difficult-to-machine materials.
- Simulation results show the method is effective for turbine blade models.

## Abstract

Pinch milling is a new technique for slender and long blade machining, which can simultaneously improve the machining quality and efficiency. However, two-cutter orientation planning is a major challenge due to the irregular blade surfaces and the structural constraints of nine-axis machine tools. In this paper, a method of twin-tool smoothing orientation determination is proposed for a thin-walled blade with pinch milling. Considering the processing status of the two cutters and workpiece, the feasible domain of the twin-tool axis vector and its characterization method are defined. At the same time, an evaluation algorithm of global and local optimization is proposed, and a smoothing algorithm is explored within the feasible domain along the two tool paths. Finally, a set of smoothly aligned tool orientations are generated, and the overall smoothness is nearly globally optimized. A preliminary simulation verification of the proposed algorithm is conducted on a turbine blade model and the planning tool orientation is found to be stable, smooth, and well formed, which avoids collision interference and ultimately improves the machining accuracy of the blade with difficult-to-machine materials.