Direct correction of thermo-elastic deformations

根据VDI/DGQ 3441标准，生产精度、加工精度和几何精度是大多数机床关心的问题。机床的几何精度是指体积中的任何位置都可以接近的精度。它取决于轴之间的几何偏差和单轴本身的几何偏差。刀具中心点(Tcp)相对于其所需位置的笛卡尔偏差可以用运动链模型和ISO 230-1中定义的误差来明确描述。为了提高机床的几何精度，机床在投入使用后，其几何形状由机床的控制系统测量和修正。在工作条件下，测量误差由静态、动态和非稳态热弹性误差叠加而成。热弹性误差占总误差的75%。本课题主要针对这些误差，除了机器内部的热源和散热器外，环境的热影响会导致热流进入机器的结构部件。根据热源的热容、质量分布和位置等热材料特性，形成一个不规则的、不稳定的温度场。与伸长长度、伸长系数、零件结构、零件之间的位置以及位置测量系统的类型和安装一起，机器结构的偏差和倾角都是由该温度场引起的。因此，产生的tcp偏差高度依赖于姿态。如果测量后机床的热状态发生高度变化，则误差可能会增加，导致tcp偏离其所需位置的程度更高。随后，零件质量下降。一个实际测量几何误差的过程可以帮助解决这个问题。在此建议的加工过程中，如果在最终切割前几分钟获得，则测量的机床误差是实际的。到目前为止，科学和工业中还没有最先进的技术能够实际测量中小型加工中心的加工过程的几何误差。本研究项目的目的是验证这种测量方法。首先，应验证直接补偿测量偏差的方法。

According to VDI/DGQ 3441 the production accuracy, the machining accuracy and the geometrical accuracy are a matter of concern for the majority of machine tools. The geometrical accuracy of a machine tool is the accuracy with that any position in the volume can be approached. It depends on the geometrical deviations between the axes and of the single axis itself. The cartesian deviations of the tool center point (TCP) from its required position can explicitly be described by a model of the kinematic chain and the errors defined in ISO 230-1.To increase the geometrical accuracy of machine tools their geometry is measured and corrected by the control system of the machine after the bringing into service. Under operating conditions, the measured errors are superposed by static, dynamic and non-steady thermo-elastic errors. The thermo-elastic errors represent up to 75% of the total error. The presented project focusses on these errors.Beside machine internal heat sources and sinks thermal influences of the environment induce heat flows into the structural components of the machine. Depending on the thermal material characteristics, such as heat capacity, mass distribution and position of the heat sources, an irregular and non-stationary temperature field is formed. Together with the elongation lengths, their elongation coefficients, the part structure, the position of the parts to each other and the type and installation of the position measurement system, deviations and inclinations of the machine structure result from this temperature field. Hence, the resulting TCP deviation is highly pose dependent.If high changes of the thermal state of the machine tool occur after the measurement, the errors can increase, leading to a higher deviation of the TCP from its required position. Subsequently the part quality decreases. A process actual measurement of the geometrical errors could help to deal with this problem. Measured machine errors are in the case of this proposal process actual, if they are acquired a few minutes before the final cut.Up to now, there is no state of the art technology available in science and industry that is able to measure the geometrical errors of small and medium machining centers process actually. The aim of the presented research project is the validation of such a measurement method. On top, a method for the direct compensation of the measured deviation shall be validated.