Multiple-sensor integration for efficient reverse engineering of geometry

This paper describes a multi-sensor measuring system for reverse engineering applications. A sphere-plate artefact is developed for data unification of the hybrid system. With the coordinate data acquired using the optical system, intelligent feature recognition and segmentation algorithms can be applied to extract the global surface information of the object. The coordinate measuring machine (CMM) is used to re-measure the geometric features with a small amount of sampling points and the obtained information can be subsequently used to compensate the point data patches which are measured by optical system. Then the optimized point data can be exploited for accurate reverse engineering of CAD model. The limitations of each measurement system are compensated by the other. Experimental results validate the accuracy and effectiveness of this data optimization approach

Tactile 3D probing system for measuring MEMS with nanometer uncertainty : aspects of probing, design, manufacturing and assembly

Measurement underpins manufacturing technology, or in more popular terms: when you cannot measure it, you cannot manufacture it. This is true on any dimensional scale, so for microand nanotechnology to deliver manufactured products it must be supported by reliable metrology. Component miniaturization in the field of precision engineering and the development of micro electromechanical systems (MEMS) thus results in a demand for suitable measurement instruments for complex three-dimensional components with feature dimensions in the micrometer region and associated dimensional tolerances below 100 nm. As will be discussed in the first chapter of this thesis, several ultra precision coordinate measuring machines (CMMs) are developed. These CMMs are suitable for measuring complex threedimensional products, like MEMS and other miniaturized components. From a discussion on available probe systems in the first chapter it is apparent that, with respect to measurement uncertainty and applicability of measurements on MEMS and other miniaturized components, the performance of ultra precision CMMs is currently limited by the performance of available probe systems. The main reason is that the measurement using a probe system is not purely influenced by work piece topography, but also by interaction physics between probe tip and work piece. As the dimensional scale of the measurement decreases, the problems associated with this interaction become increasingly apparent. Typical aspects of this interaction include the influence of contact forces on plastic deformations in the contact region, surface forces and geometric and thermal effects. The influence of these aspects on the measurement result is discussed in the second chapter. This chapter will combine results from literature, simulation and experimental results to discuss the aspects that influence the measurement result in tactile probes. From these results it will become apparent that these aspects underlie the limitation for precision measurements on miniaturized components using tactile CMM metrology. As a result, these interaction aspects are the main challenge when designing ultra precision probes. The analysis of the interaction physics is used in the design of a novel silicon probing system with integrated piezo resistive strain gauges to measure a displacement of the probe tip. The result is a probe system with a colliding mass of 34 mg and an isotropic stiffness at the probe tip with a stiffness down to 50 N/m. The measurement range of the probing system is 30 µm, but in most measurements a range of 10 µm is used which slightly improves the signal to noise ratio. Calibration results using the planar differential laser interferometer setup as discussed in chapter 1 show a standard deviation of 2 nm over 2000 measurement points taken in a 6 hour time frame over a repeated 5.5 µm displacement. The combined 3D uncertainty of the probing system is estimated to be 17.4 nm. In order to measure micrometer scale structures, including holes and trenches, the probing system can be equipped with micrometer scale probe tips. The main limitation is the relative stiffness between the stylus and the suspension of the probing system. By design optimization, a ratio between the length and radius of the measurement part of the stylus of 50 can be obtained, making the probing system highly suitable for measuring these micrometer scale structures. So far, probe tips with a radius of 25 µm have been manufactured and work is being done to decrease this radius even further. The probing system is implemented on a high-accuracy coordinate measuring machine and is suitable for three-dimensional tactile measurements on miniaturized components with nanometer uncertainty. A main limitation when manufacturing the probe is assembly of the probe tip, stylus and chip which is discussed in chapter 4. Assembly of the probe is investigated in a series of experiments on an automated assembler. Based on these results, the design of the probe is optimized for assembly and the automated assembler is made suitable for assembly of the probe by implementation of a novel suction gripper. This resulted in an improvement in placement uncertainty at the tip by a factor of 10 and an increase in yield during assembly from 60 - 80% initially, to over 95%. In chapter 5 several experimental results with the probe system are discussed, including a quantification of the effects of surface forces on tactile measurements. It is shown that these effects are highly repeatable and result in an attraction of 40 µN and 60 µN in the xy- and z-direction, respectively. Moreover, it is shown that the influence of surface forces on a measurement in the xy-plane can be observed for a separation of 500 µm or less. Finally, conclusions and recommendations for further research are discussed in chapter 6

Position and orientation correction for pipe profiling robots

Sewer pipelines are prevalent, important, valuable, unnoticed, and often in a state of disrepair. Pipeline inspection is essential for effective management of wastewater systems and is now mandated for many municipalities complying with the Governmental Accounting Standards Board Statement 34 and EPA regulations. Pipe inspection robots are routinely used to inspect underground pipelines for cracks, deformations, leaks, blockages and other anomalies to prevent catastrophic failure and to ensure cost effective maintenance and renewal. Most existing pipe inspection robots only collect video footage of pipe condition. Pipe profiling technology has recently been introduced to allow for measurement of the internal coordinate geometry of pipelines. Accurate radial measurements permit the calculation of several important pipe parameters which aid in the determination of pipe condition and prediction of time to failure. Significant research work has been completed in North America, Europe, Asia and Australia aimed at improving the accuracy and automation of the pipe inspection process. However, standard calibration, verification, reporting and analysis practices must be developed for pipe profilers if coordinate profiling data is to be effectively included in the long term management of pipeline assets. The objective of this research is to quantify the measurement error incurred by a pipe profiler\u27s misalignment with the pipe axis, present a new methodology to correct the measurement error, develop a prototype profiler to verify the equations derived herein, and to further the development of pipe profiler technology at the Trenchless Technology Center at Louisiana Tech University. Equations are derived for pipe ovality as a function of the robot\u27s position and orientation with respect to a pipe to demonstrate the magnitude of the error which is introduced by a robot\u27s misalignment with the pipe axis. A new technique is presented to estimate the position and orientation of a profiler using radial measurement devices at each of its ends. This technique is demonstrated by applying homogeneous coordinate transformations to simulated radial measurements based on mathematically generated data that would be obtained by incrementally rotating two parallel radial measuring devices in a perfectly cylindrical pipe. A prototype pipe profiling robot was developed to demonstrate the new position and orientation technique and to experimentally verify the measurement error caused by a robot\u27s misalignment with the pipe axis. This work improves the accuracy and automation of pipe profiling technology and makes a case for the development of industry standard calibration, verification, reporting and analysis practices

Design and Applications of Coordinate Measuring Machines

Coordinate measuring machines (CMMs) have been conventionally used in industry for 3-dimensional and form-error measurements of macro parts for many years. Ever since the first CMM, developed by Ferranti Co. in the late 1950s, they have been regarded as versatile measuring equipment, yet many CMMs on the market still have inherent systematic errors due to the violation of the Abbe Principle in its design. Current CMMs are only suitable for part tolerance above 10 μm. With the rapid advent of ultraprecision technology, multi-axis machining, and micro/nanotechnology over the past twenty years, new types of ultraprecision and micro/nao-CMMs are urgently needed in all aspects of society. This Special Issue accepted papers revealing novel designs and applications of CMMs, including structures, probes, miniaturization, measuring paths, accuracy enhancement, error compensation, etc. Detailed design principles in sciences, and technological applications in high-tech industries, were required for submission. Topics covered, but were not limited to, the following areas: 1. New types of CMMs, such as Abbe-free, multi-axis, cylindrical, parallel, etc. 2. New types of probes, such as touch-trigger, scanning, hybrid, non-contact, microscopic, etc. 3. New types of Micro/nano-CMMs. 4. New types of measuring path strategy, such as collision avoidance, free-form surface, aspheric surface, etc. 5. New types of error compensation strategy

Traceability of on-machine tool measurement: a review

Nowadays, errors during the manufacturing process of high value components are not acceptable in driving industries such as energy and transportation. Sectors such as aerospace, automotive, shipbuilding, nuclear power, large science facilities or wind power need complex and accurate components that demand close measurements and fast feedback into their manufacturing processes. New measuring technologies are already available in machine tools, including integrated touch probes and fast interface capabilities. They provide the possibility to measure the workpiece in-machine during or after its manufacture, maintaining the original setup of the workpiece and avoiding the manufacturing process from being interrupted to transport the workpiece to a measuring position. However, the traceability of the measurement process on a machine tool is not ensured yet and measurement data is still not fully reliable enough for process control or product validation. The scientific objective is to determine the uncertainty on a machine tool measurement and, therefore, convert it into a machine integrated traceable measuring process. For that purpose, an error budget should consider error sources such as the machine tools, components under measurement and the interactions between both of them. This paper reviews all those uncertainty sources, being mainly focused on those related to the machine tool, either on the process of geometric error assessment of the machine or on the technology employed to probe the measurand

Optical Tactile Probe for the Inspection of Mechanical Components

Abstract Mechanical components are often subjected to tolerances and geometrical specification. This paper describes an automatic 3D measurement system based on the integration of a stereo structured light scanner and a tactile probe. The tactile probe is optically tracked by the optical scanner by means of 3D measurements of a prismatic flag, rigidly connected to the probe and equipped with multiple chessboard patterns. Both the stereo vision system and the tactile probe can be easily configured enabling complete reconstructions of components having complex shapes. For instance, structured light scanning can be used to acquire external and visible geometries while tactile probing can be limited to the acquisition of internal and hidden surfaces

High-resolution absolute range sensors based on the combination of frequency modulation and laser triangulation for heavy industry application

Feedback control of metal strip rolling processes requires inline-capable, fast and robust thickness gauges. An optical thickness gauge is developed which measures the distance to the top and bottom of the strip with two optical sensors. They combine triangulation and multi-wavelength interferometry for a robust absolute high-resolution range measurement. Sinusoidal modulation interferometry is used to realize a very compact Fizeau-type multi-wavelength interferometer. The performance of the thickness gauge is studied in the laboratory under dynamic conditions that are close to production environment. The expanded measurement uncertainty of 0.48 μm of the system is thereby consistent with the observed deviation of the measurement values from a tactile reference sensor

Development towards a focus variation based micro-co-ordinate measuring machine

The increasing number of small and fragile parts that are being manufactured using micromachining technology has raised the demand for co-ordinate measurement machines (CMM) that can measure on a micro- and millimetric scale without contacting the part, thus avoiding damage to the surface of the part. These instruments are expected to measure on a micro- and millimetric scale with a measuring uncertainty in the nanometre range. A number of techniques used for contactless surface measurements exist, such as the focus variation (FV) technique, which have the ability to perform measurements on the micro- and millimetric scale in a short amount of time. These instruments may have the potential to be implemented in a non-contact micro-CMM platform. [Continues.

Computed tomography as a tool for tolerance verification of industrial parts

AbstractComputed tomography (CT) is becoming an important technology for industrial applications, enabling fast and accurate control of manufactured parts. In only a few minutes, a complete 3D model of a part may be obtained, allowing measurements of external and internal features. This paper presents results of tolerance verification of a plastic housing for an insulin pen manufactured by Novo Nordisk A/S. Calculation of measurement uncertainties was taken into account in decision making regarding the specified tolerance limits. Variables in terms of CT systems, data sets, and evaluation software are considered in this study