Demirtas, G. (2016). Utilisation and accuracy of rotary tables in modern production metrology : Analysis and evaluation of the reversal error by means of an incremental encoder, laser interferometer, and coordinate measuring machine [Diploma Thesis, Technische Universität Wien]. reposiTUm. https://doi.org/10.34726/hss.2016.37287
Production Metrology; Coordinate Metrology; Coordinate Measuring Machines (CMMs); Rotary Tables; Reversal Error; Backlash; Angular Metrology; Magnetic Linear Encoders; Laser Angle Interferometer
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Abstract:
The ever-increasing degree of complexity and diversity of industrial parts and assemblies brings in its wake a great demand for interchangeability, as well as more precise, accurate, reliable, and faster measurement technologies and systems. In this context, coordinate metrology has become more important than ever, since it offers several advantages compared to conventional metrology. As the core of coordinate metrology, the so-called Coordinate Measuring Machines (CMMs) enable conducting challenging measurements in a straightforward and faster manner due to their universality and versatility. Here rotary tables represent an important accessory for the CMMs, particularly for the measurement of rotationally symmetric parts, e.g. gear wheels, crankshafts and camshafts, and screw compressors. Acting as the fourth axis of CMMs, not only do they extend part accessibility but also increase the effective measurement volume. However, it must be kept in mind that they also increase the number of possible error sources. A typical example is the reversal error that influences the bi-directional repeatability and accuracy negatively when the approach direction is reversed. This factor becomes all the more decisive and significant in industrial applications where (positioning) precision and accuracy are of great significance, e.g. in welding robots and wearable exoskeletons in the context of robotic technology, and in rotary tables in the context of production technology and precision metrology. Therefore, the utilisation of the high-resolution measurement instruments in evaluating positioning accuracy characteristics is of critical importance when it comes to assuring and improving product and process quality. In the practical part of this thesis, an experimental study was carried out in the High Precision Measurement Room - Nanometrology Laboratory of the TUWien mainly in order to determine the practical capability and adequacy of a Hall-effect linear magnetic encoder in measuring positioning accuracy characteristics (in particular, the reversal error) of a manual rotary table. This was realised by implementing appropriate measurement set-ups, by conducting related measurements, and by comparing the measurement results with those obtained simultaneously by a more accurate measurement instrument, i.e. by a laser angle interferometer. In addition to that main goal, the positioning accuracy characteristics of a high-precision rotary table of a CMM was evaluated first by CMM itself, and then by laser angular interferometer for comparison and verification. Furthermore, this thesis provides readers with the state of the art in the modern production metrology, as well as makes them familiar with both conventional (tactile) and advanced types of CMMs, such as optical/optoelectronic CMMs, Multi-Sensor CMMs, Portable-CMMs, and the industrial Computed Tomography (iCT).
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