Condition Monitoring of Ultra-Precision Cutting Process of Brittle Material using Sensor Fusion and its Optimum Control

在玻璃、陶瓷等脆性材料的切削加工过程中，由于脆性断裂，工件表面通常以切屑的形式脱落。然而，已知切屑主要是在小于临界厚度的小的未变形切屑厚度和加工表面光滑无凹坑时塑性变形产生的。由于塑性变形而产生切屑的切削过程称为延性切削。由于影响延性模态切削的因素很多，这些因素对延性模态切削稳定性的影响程度尚不明确。因此，本研究的目的是寻找有效的切削过程监控参数，通过自适应控制来稳定韧性模切削过程。在超精密端面车床上，采用一种新型的单晶金刚石刀具加工单晶硅工件时，测量了刀具系统的切削力、声发射信号和振动加速度。用于脆性材料的超精密加工。结果表明：(1)进料速度为0.5 gm/rev时加工为韧性模式，进料速度为1.75 gm/rev时加工为脆性模式，进料速度为1.0 um/rev时加工为混合模式，即由于塑性变形和脆性断裂而产生切屑。(2)在旋转角度下，由于晶体结构的影响，声发射信号包络线较大，而韧性模切时推力的动态分量较小。另一方面，在声发射信号包络线较大的工件旋转角处脆性模式切削时，动态推力较大。(3)在刀具系统固有频率3khz处，脆性模态切削的声发射包络信号均值、刀具系统振动加速度的均方根值及其振动幅值均大于韧性模态和混合模态切削。(4)韧性模态切削比脆性模态和混合模态切削更大。少

Surface of workpiece is commonly removed as chips due to brittle fracture in a cutting process of brittle materials like glass and ceramics. However, it is known that the chips can be mainly generated due to plastic deformation at small undeformed chip thickness less than the critical thickness and the machined surface is smooth without pit. The cutting process in which the chips are generated due to plastic deformation is called ductile mode cutting. As there are a lot of factors affecting ductile mode cutting, it has not been clarified how much the factors affect stability of ductile mode cutting. Consequently the purpose of this study is to find out effective parameters for monitoring of cutting process to stabilize ductile mode cutting process by using adaptive control. Cutting forces, AE signals and vibration acceleration of cutting tool system were measured while single crystal silicon workpice was machined on a ultra-precision face lathe by using a single crystal diamond tool wi … More th small chamfer at cutting edge, which is being marketk. for ultra-precision machining of brittle materials. As a result, the followings are concluded from the experiments described above: (1) Machining at feed rate of 0.5 gm/rev is ductile mode, machining at feed rate of 1.75 gm/rev is brittle mode and machining at feed rate of 1.0 um/rev is mixed mode: that is, the chips were generated due to plastic deformation and brittle fracture. (2) Dynamic component of thrust force was smaller in the ductile mode cutting at rotational angle where envelope of AE signal was largar due to crystalline structure. On the other hand, dynamic thrust force was larger in the brittle mode cutting at rotational anglo of workpiece where envelope of AE signal was larger. (3) Mean values of AE envelope signal, RMS value of vibration acceleration of cutting tool system and its vibration amplitude at frequency of 3 kHz, which was natural frequency of cutting tool system, were larger in the brittle mode cutting more than in the ductile and mixed mode cuttings. (4) Static thrust force per unit area of cutting cross section was larger in the ductile mode cutting more than in the brittle mode and the mixed mode cuttings. Less