Minimum Thickness of Cut in Micromachining

在特定切削条件下，最小切削厚度是决定加工精度的最重要因素之一。在高可靠性的机床上使用特制的细金刚石刀具，可以得到Cu和Al表面最小未切削厚度在1 nm左右的极薄切屑。对于Al，虽然新的锋利刃口可以去除纳米切屑，但由于刀具过度磨损，刃口质量较差，难以稳定地获得纳米切屑。换句话说，当切削刃锐度保持在几纳米水平时，微加工所能达到的极限精度可能与最小切割厚度的精度相同。采用原子切割模型，假设切削刃和工件的晶格结构及其相互作用，通过计算机模拟可以很好地理解纳米级微芯片的去除过程。通过计算机仿真对实验结果进行了分析，结果表明：最小切削厚度在一定程度上受刀-工-料相互作用的影响，但受刃口锐度的影响更大，最小切削厚度可能在刃口半径的1/10量级。

The minimum thickness of cut is one of the most important factor to determine the machining accuracy extremely attainable for a specific cutting condition. With the use of a specially prepared fine diamond tool on a highly reliable machine tool, very thin chips the minimum uncut thickness of which are at the order of 1 nm can be obtained in facing of Cu and Al. In the case of Al, while a new sharp cutting edge can remove the nanometric chip, it is difficult to obtain the nanometric chip stab-ly due to the poor cutting edge quality resulted from excessive tool wear. In other words, the extreme accuracy attainable in micromachining may be of the same order as that of minimum thickness of cut when the cutting edge sharpness is maintained at a few nm level. The microchip removal process at nanometric level can be well understood by the computer simulation using an atomistic cutting model in which the lattice structures of cutting edge and workpiece and their interactions are assumed. The analysis of the experimental results aided by the computer simulation show that, while the minimum thickness of cut is affected by the tool-workmaterial interaction to a certain degree, it is more strongly affected by the sharpness of cutting edge and that the minimum thickness of cut may be at the order of 1/10 of the cutting edge radius.