Experimental and finite element analysis of temperature and energy partition to the workpiece while grinding with a flexible robot

Grinding processes performed with flexible robotic tool holders are very unlike conventional types of grinding because of low stiffness of the robot's structure. A special flexible robotic grinding process is used for in situ maintenance of large hydroelectric equipment for bulk material removal over large areas rather than as a finishing step, as is the case for most conventional grindings. Due to the low structural stiffness of tool holder, cutting is interrupted at each revolution of wheel during the grinding process. In this study, an investigation is carried out to determine the temperatures and energy partition to the workpiece for the above-mentioned flexible robotic grinding process by a three-dimensional finite element thermal model. Experiments were undertaken using embedded thermocouples to obtain the subsurface temperature at several points in the workpiece during the process. Then, energy partition to the workpiece was evaluated using a temperature-matching method between the experimental and numerical results. This ratio is used for predicting the temperature field at the wheel-workpiece interface with a relevant heat source function. Kinematics of cut and the flexible robot's dynamic behavior are considered in applying the heat input to the model. The energy partition to the workpiece in this specific flexible grinding process is found to be lower than for analogous conventional precision grinding processes. Two models, one from the literature and one from the power model of the process, are modified and proposed for determining the energy partition. The results showed that the energy partition ratio decreases by increasing the process power. Also, this ratio slightly decreases at higher feed speeds. In addition, lower temperatures were seen at higher powers due to the lower intensity of heat input over a larger contact area. Experimental observations show close agreement between simulated contact temperatures and measured results. (C) 2013 Elsevier B.V. All rights reserved.

由于机器人结构的刚度较低，使用柔性机器人刀架进行的磨削工艺与传统磨削类型有很大不同。一种特殊的柔性机器人磨削工艺用于大型水电设备的现场维护，用于大面积去除块状材料，而不是像大多数传统磨削那样作为精加工步骤。由于刀架的结构刚度低，在磨削过程中砂轮每转一圈切削就会中断。在本研究中，通过一个三维有限元热模型，对上述柔性机器人磨削工艺中工件的温度和能量分配进行了研究。在加工过程中，使用嵌入式热电偶进行实验，以获取工件内几个点的表面下温度。然后，通过实验结果和数值结果之间的温度匹配方法来评估工件的能量分配。该比率用于通过相关热源函数预测砂轮 - 工件界面处的温度场。在将热量输入模型时，考虑了切削运动学和柔性机器人的动态行为。在这种特定的柔性磨削工艺中，发现工件的能量分配比类似的传统精密磨削工艺要低。对两个模型（一个来自文献，一个来自该工艺的功率模型）进行了修改并提出用于确定能量分配。结果表明，能量分配比随着加工功率的增加而降低。此外，在较高的进给速度下，该比率略有下降。另外，由于在较大接触面积上热输入强度较低，在较高功率下温度较低。实验观察表明，模拟接触温度和测量结果之间非常吻合。(C) 2013 Elsevier B.V.保留所有权利。