Effect of Pre-Existing Micro-Defects on Cutting Force and Machined Surface Quality Involved in the Ball-End Milling Repairing of Flawed KDP Crystal Surfaces oleh Hongqin Lei, Jian Cheng, Dinghuai Yang, Linjie Zhao, Mingjun Chen, Jinghe Wang, Qi Liu, Wenyu Ding, Guang Chen