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首页> 外文会议>Proceedings of the Twenty-sixth annual meeting of the American Society for Precision Engineering >MEASURING POSITIONING ACCURACY OF LARGE MACHINE TOOLS
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MEASURING POSITIONING ACCURACY OF LARGE MACHINE TOOLS

机译：大型机床定位精度的测量

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Nowadays, manufacturing of large parts is a driving force in machine tool industry. This demand has challenged machine tool builders to materialize designs in a new scale and even more, to keep the accuracy of these machines at the level of smaller machines. On the other hand, builders lack appropriate tools to assess positioning accuracy of big machines in practical ways. The classical set of instruments used to setup the machine, such us precision levels, squares or linear interferometers with different kinds of optics is becoming obsolete when addressing this new family of machines. The way to overcome these difficulties seems to be grounded on the way instruments are used more than in the development of new instruments. The base measuring technology best suited for this task seems to be laser interferometry. Other devices such as Ball Bars are able to provide accurate measurements although they get impractical when verifying very large machines. Nowadays more and more workshops have access to Laser Tracker devices. These are very handy during machine tool assembly or during the setup of jigs; on the other hand, they lack accuracy to verify machine tool positioning accuracy. Lately several approaches have arisen that take advantage of the high accuracy of the laser interferometer while disregarding the information from the rotational encoders. The basic idea relies on combining linear interferometer measurements from sequential measurements in a multilateration scheme [3]. However, when experimenting with very large machine tools some limitations become evident. In house experiments have shown that the main obstacle to achieve the limiting accuracy of this approach is instability of the ambient conditions and machine tool thermal behavior. Due to these factors, accuracies expected from pure muitilateration become meaningless. In this work an intermediate approach has been developed, where linear and rotational measurements are merged, with the aim of reducing the time required by the measurements. The benefit is double, being the measurement more economical and the machine suffering smaller thermal drifts during measurement. So the technique is valid to provide a positioning error map accurate enough to enhance the performance of the machine in future mechanical or numerical compensations and even to provide a feedback to the design.
机译：如今，大型零件的制造已成为机床行业的动力。这种需求挑战了机床制造商以新的规模甚至更大的规模实现设计，以将这些机床的精度保持在较小的机床水平上。另一方面，建设者缺乏合适的工具来以实用的方式评估大型机器的定位精度。解决这类新的机器系列时，用于设置机器的经典仪器（例如具有不同光学元件的精密水平仪，平方或线性干涉仪）变得过时了。克服这些困难的方法似乎是基于使用仪器的方式，而不是开发新仪器。最适合此任务的基础测量技术似乎是激光干涉仪。诸如球杆之类的其他设备也能够提供准确的测量值，尽管它们在验证大型机器时变得不切实际。如今，越来越多的车间可以使用Laser Tracker设备。这些在机床组装或夹具安装过程中非常方便。另一方面，它们缺乏验证机床定位精度的准确性。最近出现了几种方法，它们利用激光干涉仪的高精度而忽略了来自旋转编码器的信息。基本思想是在多边方案中将线性干涉仪的测量结果与顺序测量结果进行组合[3]。但是，在试验非常大型的机床时，一些局限性显而易见。内部实验表明，达到这种方法的极限精度的主要障碍是环境条件的不稳定和机床的热行为。由于这些因素，纯变位预期的准确性变得毫无意义。在这项工作中，已经开发出一种中间方法，其中将线性和旋转测量合并在一起，目的是减少测量所需的时间。好处是双重的，因为它使测量更为经济，并且机器在测量过程中遭受的热漂移较小。因此，该技术可有效地提供足够准确的定位误差图，以在将来的机械或数字补偿中增强机器的性能，甚至可为设计提供反馈。

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