Minimum Thickness of Cut in Micromachining

在特定的加工条件下，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超细金刚石工具，可以在铜和铝表面上获得最小未切削厚度为1 nm的超薄切屑。在Al的情况下，虽然新的锋利的刃口可以去除纳米芯片，但由于刀具磨损过大，导致刀具刃口质量较差，很难获得尖锐的纳米芯片。换言之，在微细加工中可获得的极高精度可能与当刀具刃口锐度保持在几纳米水平时的最小切割厚度的精度相同数量级。采用原子模型进行计算机模拟，可以很好地理解纳米级的微芯片去除过程，该模型假设了刀具和工件的晶格结构及其相互作用。通过计算机仿真对实验结果的分析表明，刀具-材料相互作用对最小切削量有一定影响，但受刃口锋利程度的影响较大，最小切削量可能在刀具刃口半径的1/10左右。

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.