Twenty years after the publication of a first CIRP Keynote Paper about gear metrology [32], this paper reviews again the state of the art in this area. Gear technology has changed and improved significantly during the past decades, which initiated substantial improvements in gear metrology, too. On the other hand, for up to 50% of gear inspection technologies used today, only minor changes are observed. Consequently, this update focuses on new or significantly improved techniques, such that only the combination of both this publication and [32] gives a comprehensive review of the state of the art in gear metrology. Gear technology in emerging markets, e.g., electric cars, large gears for energy systems, and micro gear drives, extends the scope of inspection tasks and requires new measuring methods and instruments, including optical sensors. Measured data, covering the entire gear flank of all teeth, need areal flank descriptions, areal evaluation methods, and areal deviation parameters. New calibration methods and artifacts will improve measurement uncertainties.

Weniger Zähne knirschen – Vollständige und flächenhafte Auswertung von Verzahnungsgeometrien verschieden großer Werkstücke aus einer Hand . . . . .47

The classic radial composite testing procedure of the workpiece gear includes a functional test using an expensive master gear. One of the results of this test is the runout deviation of the entirety of the geared workpiece surface. Nevertheless, any imperfectness of the master gear influences all results. This paper presents a reversal method for calibration, based on the rosette method, which eliminates the impact of runout deviations of the master gear. The major benefits of the developed calibration method are that the geometric gear quantities runout and dimension over balls can be determined at an enhanced accuracy, level based on a simple functional test and much faster than by usual tactile measurements. Another advantage is that accuracy requirements of the master gear and thus the costs can be reduced. (C) 2020 CIRP. Published by Elsevier Ltd. All rights reserved.

This chapter presents the basic principles and techniques for measuring the geometrical features of cylindrical gears. The mathematical models for nominal cylindrical gear geometry are given in a two-dimensional (2D) space and extended to a three-dimensional (3D) space. The geometric parameters for assessing the conformance of gear design and manufacturing are highlighted based on the current international standards. Conventional gear inspections by tactile measuring systems such as gear-measuring instruments (GMIs) and coordinate measuring machines (CMMs) are discussed in detail, including measuring strategies and evaluations of “raw” spatial data sets, methods of calibrating gear-measuring systems, and the estimation of measurement uncertainty. Emerging technologies including optical measuring systems and areal evaluation methods are introduced as part of future cylindrical gear metrology.

Geometric measurements of cylindrical gears are mainly conducted by either applying the generation principle or by coordinate measurements of points on a flank surface. In both cases, a rotary table (RT) is highly involved in the inspection process. The RT error motions and the misalignments of the gear axis with respect to the table’s effective rotary axis affects the measurement results, whose impacts increase with the gear dimensions. This paper presents the influence of such errors on gear measurements using both the classical line oriented and the areal inspection methods. A compensation method to remove these influences in gear evaluations is proposed using a RT, which was calibrated with a ball plate artifact. The methods are validated by measuring and evaluating a large gear artifact applying multiple strategies with and without compensation.

In contrast to measurements of the dimensions of machined parts realized by machine tools and characterized by CMMs, software results are not fully traceable and certified. Indeed, a computer is not a perfect machine and binary encoding of real numbers leads to rounding of successive intermediate calculations that may lead to globally false results. This is the case for poor implementations and poorly conditioned algorithms. Therefore, accurate geometric modelling and implementations will be detailed. Based on the works of National Metrology Institutes, the problem of software traceability will also be discussed. Some prospects for this complex task will finally be suggested.

Rotary tables as components of 4-axis measuring devices provide a quick rotary positioning in geometry measurements, but the non-trivial error motions need to be determined and compensated. This paper presents a new solution for the error mapping, which calibrates the rotary table, the 3-axis measuring device and the artifact (circular ball plate) simultaneously. Multi-measuring and approximation techniques are introduced to identify and quantify the error motions based on obtained point clouds. A mathematical model covers all the deviation sources, occurring at the movement of a rotary axis. Simulations and experimental results verify and validate the solution. The simple and flexible calibration setup together with the developed evaluation procedure enable a compensation of rotary table/axis deviations in a wide application field.

Today's gear design with complex flank features aims to meet the demanding performance requirements of lower noise emission, higher power density and longer lifetime. Geometric properties evaluated over the entire flank area can provide holistic information of a produced gear for both process control and product quality assessment purposes. Optical sensors based on various measuring principles and integrated into Coordinate Measuring Machines (CMMs) or Gear Measuring Instruments (GMIs) can capture high density point clouds of gear flanks in a reasonable time. Other than in conventional gear metrology, these points cover the entire flank instead of one profile and one lead line only, offering an improved data base for a feedback to the manufacturing process and for a performance assessment of gears. An areal measurement of gear flanks requires new mathematical approaches and new software solutions for evaluation. This paradigm change includes a revision and extension of the widely-used gear deviation parameters (e.g. f(H alpha) F-beta, F-p) towards areal parameters and their effective determination by two-dimensional orthogonal polynomials. This paper primarily will be focused on the mathematical methods to obtain areal gear flank modifications and deviations with respect to a pure involute flank surface. However, the parameters characterizing these modifications and deviations keep their meanings in terms of both a control of the manufacturing process as well as an assessment of functional properties. The calculation of areal gear parameters is based on 2D-Chebyshev polynomials. They offer an evaluation of individual flanks as well as a holistic gear evaluation.

Three existing major challenges in today's cylindrical gear metrology are: an increased need of holistic information on gear geometry; an increasing variety and use of flank modifications; and an improved feedback to the manufacturing process. This paper analyses the consequences of these challenges. They require a paradigm change in gear metrology concerning the sensing hardware (tactile vs. optical), measuring strategies (line oriented vs. area oriented), and evaluation methods. The latter includes a revision and update of the widely used gear deviation and modification parameters (e.g. fα, fβ, Fp, CHα, Cβ) and their effective determination by Chebyshev polynomials. Simulated and measured gear data are analyzed and a proposal for a revised set of gear deviation and modification parameters is presented.

Error avoidance in high-precision manufacturing processes becomes more important for numerous state-of-the-art technologies. Selective laser melting is one of these technologies offering large potentials in the production of complex and flexible metal products. As the technology is relatively new, it is vulnerable for errors, given that the process parameters are not measured yet. A novel multilevel control concept, incorporating several sensors, has the potential to reduce errors significantly. For inner cascade control, the laser power will be adjusted by measurements with an intensity sensor for wavelengths in the visible range. This sensor is integrated into the optical path of the laser beam. An adapted self-learning strategy supports the stability of the process by updating the parameters of the used multidimensional model in order to attenuate environmental influences or shifts within the process. This work presents the concept of the control approach, first measurement results and the required relations between measurement, process and control parameters.

Displacement measurement using a database of speckle patterns is one method for producing a low cost, non-contact, high resolution displacement measurement. However, this method requires a large number of database patterns that limits the measurement range and speed, especially in two dimensions. Appropriate curve fitting helps reduce the number of required database patterns, making it feasible to develop an absolute scale for machine tools based on speckle correlation. The curve used for fitting is the autocorrelation function of the speckle pattern, referred to here as the correlation curve. (C) 2016 Elsevier Inc. All rights reserved.

The field of Large-Scale Metrology has been studied extensively for many decades and represents the combination and competition of topics as diverse as geodesy and laboratory calibration. A primary reason that Large-Scale Metrology continues to represent the research frontier is that technological advances introduced and perfected at a conventional scale face additional challenges which increase non-linearly with size. This necessitates new ways of considering the entire measuring process, resulting in the application of concepts such as virtual measuring processes and cyber-physical systems. This paper reports on the continuing evolution of Large-Scale Metrology.

The contact pattern, defined as the area where gear teeth come into contact during their meshing, is a crucial quality feature of gears. If the size and location of the contact pattern are wrong, the gear meshing properties can be significantly affected (e.g., lifetime, noise). Despite several disadvantages, the so-called “paste method” is established as a method to analyse contact patterns. Here, a new measuring approach is examined using the Finite Elements Method (FEM). It is based on the heating-up of one tooth flank with a powerful laser, a subsequent partial transfer of the heat to a meshing tooth of the second gear wheel and finally capturing the heat distribution on that flank as an infrared image shortly afterwards. The thermal image should correspond to the contact pattern of that individual combination of teeth. A numerical analysis shows that at medium- and large-sized gears the achievable temperature increase will be high enough to be detected with modern infrared cameras.

The design and the application of a circular ball plate artefact, introduced a couple of years ago, appeared to be very simple. But at the end, a measurement result and a measurement uncertainty can be determined only via NMI calibrated artefacts. Recently, PTB and NMIJ published self-calibration methods for pitch artefacts, one based on the rosette-method. This paper describes the testing and verification of this calibration method, applied to a gear artefact. The method was extended to calibrate not only the pitch position of the balls, but also their radial and height position on the circular ball plate (gear artefact). The concept of this advanced method, experiences regarding its application and test results will be presented.

The generation of desired surface layer properties by a certain manufacturing process requires a comprehensive knowledge of the physical loads during the process and their influences on the workpiece material. This paper presents the setup and results of two in-process measurement systems, which are specifically designed to locally determine temperature and strain in several processes (in this case: grinding and deep rolling). One measuring system is based on speckle interference effects (speckle photography) detecting the deformation distribution of the workpiece surface and the other applies resistance deviation measurements of integrated thin films inside the near-surface layer to determine temperature and strain variations.

A laser-chemical process combines advantages of both laser ablation and electro-chemical machining and is used to produce free form micro forming tools. The desired geometry results from a sequence of overlapping removal paths with different cross section. Due to the high requirements of geometry accuracy and surface roughness, a three-level quality control system is developed for this process. Based on causal analysis between removal profile and process parameters a post-process controller designs the position and cross section for the removal paths. With an in situ quality control loop the deviation from the desired removal profile along the feed direction could be compensated by using a state observer and an interferometer. At an in-process level the required process parameters are real time observed and controlled.

Kurzfassung Das Thema Schleifbrand war bereits Gegenstand vieler Untersuchungen in der Wissenschaft sowie der industriellen Forschung. Nach wie vor ist das Phänomen dieser thermo-mechanischen Schädigungen hartfein-bearbeiteter Werkstoffrandzonen nicht zufriedenstellend charakterisiert oder definiert. In der Industrie existiert ein großes Interesse an der Thematik, da ein zuverlässiges und serientaugliches Messverfahren für die Erfassung des Zustandes geschliffener Oberflächen fehlt. Die präsentierten Arbeiten befassen sich mit der Erzeugung und Charakterisierung thermo-mechanischer Schädigungen in einem Außenrundschleifprozess sowie der Erfassung dieser unerwünschten Veränderungen mit dem Verfahren der Barkhausenrausch-Analyse. Die Ergebnisse zeigen, dass bereits vor Auftreten konventionell detektierbarer Gefügeänderungen Zugeigenspannungen durch Schleifprozesse in die Randzone eingebracht werden können. Die Barkhausenrausch-Analyse ermöglicht bei Kombination mehrerer Prüfgrößen eine zuverlässige Erfassung dieser Eigenspannungs- und Gefügeänderungen.