The Influence of Tool Wear on Surface Morphology in T2 Pure Copper High Speed Milling

The increase of machining distance is inevitably accompanied by the increase of tool wear, which also leads to the deterioration of the machined surface quality. In order to satisfy the increasing processing needs of T2 pure copper and improve the processing quality of T2 pure copper, the work aims to study the internal relationship between tool wear and machined surface morphology at different milling speeds. The experiment takes milling speed as independent variable. According to the single factor test results, the influence of milling speed on tool wear is studied. On the basis of wear tool milling force model and machined surface stress model, the influence of tool wear on machined surface quality and the reason of surface defects are analyzed from milling force, tool damage form and wear mechanism. The tool wear morphology and the machined surface defects are classified and characterized by optical microscope and scanning electron microscope. When the milling speed is low, there is intense extrusion friction between the rake face and the chip due to the relatively large milling force Fx in the feed direction, resulting in scratches and grooves on the rake face. Lower milling speed means longer machining time at the same milling distance, it results that the cutting tool in processing not only should take more cycle load, but also bear more impact times. It is easy to cause the stress concentration at tool tip, so as to make the cutting edge break and tear. Severe tool wear often results in the change of tool geometry and the further deterioration of tool stress state, which destroys the stability of milling system, leads to flutter ripple on workpiece surface, and greatly increases the roughness of machined surface. Tool wear will change the actual friction form between cutter and workpiece and affect the machining surface stress state, so that the tearing stress on the workpiece surface exceeds the yield strength of the material, and then form the surface tearing. However, when the milling speed is higher, the milling system is relatively stable due to the lighter damage of the tool, and the machined surface still maintains good machining quality. Especially when milling speed is 600 m/min, the surface roughness Sa and Sq reaches 1.80 μm and 2.25 μm. It remains around 2.20 μm and 3.10 μm when the tool is worn. In the milling of T2 pure copper, increasing the milling speed has a positive effect on prolonging the tool life and improving the quality of the machined surface. © 2022, Chongqing Wujiu Periodicals Press. All rights reserved.