1. School of Mechanical Engineering, Shandong University of Technology, Zibo, P. R. China
2. Laser Precision Manufacturing Research Center, Shandong University of Technology, Zibo, P. R. China
3. Weihai Guangtai Airport Equipment Co., Ltd, Weihai, P. R. China
4. Shandong Provincial Key Laboratory of Precision Manufacturing and Non-traditional Machining, Zibo, P. R. China