Effect of Machine Stiffness on Cutting Performance

研究了点击式钻头的切削特性，特别是切削速度和切深对切削力的影响。点击式钻头作为一种截割工具正变得越来越流行，但其性能仍有待讨论。在不同的切割深度和切割速度下进行了一系列的岩石切割实验，发现切削力的水平分量随着切割深度的增加而线性增加。这个简单的关系对于平均值、平均峰值和峰值都是正确的。研究还发现，当以较高的切割速度切割坚硬的安山岩时，结瘤鼻会在钻头的间隙面上发展。结果表明，随着切割速度的提高，切削力，特别是其垂直分量显著增大。机械刚度被认为是岩石切割过程中的重要因素之一，但其对切割性能的影响却鲜有人研究。本文设计并制造了一台变刚度试验台，进行了一系列的切割实验，发现柔度矩阵的水平-垂直(交叉)分量具有重要意义。如果为负值，则切削力的垂直分量在切割过程中与水平分量协调增加和减少。但是，如果为正数，则当水平分量减少时，垂直分量增加，反之亦然。研究还发现，机床刚度对切削力的平均值、平均峰值和最大值有影响。相对于平行于钻头轴线的力，平均峰值和最大值随着刚度的增加而增加，即对应于横向和垂直刚度分量之和的刚度。

The cutting characteristics of a point attack bit, especially the effects of cutting speed and depth of cut on cutting force were investigated. Point attack bits are becoming more popular as a cutting tool for boomheader, but its performances are still open to discussion. A series of rock cutting experiments were conducted with various cutting depths and speeds.It was found that the horizontal component of cutting force increases linearly with cutting depth. This simple relation is true all for the mean, the mean peak and the peak values. It was also found that the build-up nose develops on the clearance face of the bit when a hard andesite is cut at higher cutting speed. As a result, cutting force, especially its vertical component, increases considerably with cutting speed.The effects of cutting machine stiffness are discussed. Machine stiffness is regarded as one of the important factors in rock cutting, but its effects on cutting performance have scarcely been studied. In this study, a test rig with variable stiffness was designed and manufactured with which a series of cutting experiments were performed.It was iound that the horizontal-vertical (cross) component of compliance matrix has significant importance. If it is negative, the vertical component of cutting force increases and decreases harmonically with the horizontal component during a cutting process. If positive, however, the vertical component increases when the horizontal component decreases, and vice versa. It was also found that machine stiffness has effects on the mean, the mean peak and the maximum values of cutting force. The mean peak and the maximum values increase with stiffness against the force parallel to the bit axis, that is, stiffness corresponding to the sum of the cross and the vertical components of stiffness.