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

Investigating the Capability of Precision in Robotic Grinding

Most robotic grinding focus on the surface finish rather than accuracy and precision. However ever increased demand on complex component manufacture requires to advance robot grinding capability so that more practical and competitive accurate systems can be developed. The current study focuses on improving the level of accuracy of robotic grinding, which is a significant challenge in robot application because the kinematic accuracy of robot movement is much more complex than normal CNC machine tools. Aiming to improve accuracy and efficiency the work considers all quality of measures including surface roughness and the accuracy of size and form. For that to be done, a repeatability test is firstly preformed to observe the distributions of the joint positions and how well the robot responds to its programmed position using a dial gauge method and a circuit trigger method. After that, a datum setting method is performed to assess the datum alignment with the robot. Hence, a mathematical model based on regression analyses applies towards the collected data to observe closely any error correlation when setting up a datum to perform the grinding procedure

Automatic tolerance inspection through Reverse Engineering: a segmentation technique for plastic injection moulded parts

This work studies segmentations procedures to recognise features in a Reverse Engineering (RE) application that is oriented to computer-aided tolerance inspection of injection moulding die set-up, necessary to manufacture electromechanical components. It will discuss all steps of the procedures, from the initial acquisition to the final measure data management, but specific original developments will be focused on the RE post-processing method, that should solve the problem related to the automation of the surface recognition and then of the inspection process. As it will be explained in the first two Chapters, automation of the inspection process pertains, eminently, to feature recognition after the segmentation process. This work presents a voxel-based approach with the aim of reducing the computation efforts related to tessellation and curvature analysis, with or without filtering. In fact, a voxel structure approximates the shape through parallelepipeds that include small sub-set of points. In this sense, it represents a filter, since the number of voxels is less than the total number of points, but also a local approximation of the surface, if proper fitting models are applied. Through sensitivity analysis and industrial applications, limits and perspectives of the proposed algorithms are discussed and validated in terms of accuracy and save of time. Validation case-studies are taken from real applications made in ABB Sace S.p.A., that promoted this research. Plastic injection moulding of electromechanical components has a time-consuming die set-up. It is due to the necessity of providing dies with many cavities, which during the cooling phase may present different stamping conditions, thus defects that include lengths outside their dimensional tolerance, and geometrical errors. To increase the industrial efficiency, the automation of the inspection is not only due to the automatic recognition of features but also to a computer-aided inspection protocol (path planning and inspection data management). For this reason, also these steps will be faced, as the natural framework of the thesis research activity. The work structure concerns with six chapters. In Chapter 1, an introduction to the whole procedure is presented, focusing on reasons and utilities of the application of RE techniques in industrial engineering. Chapter 2 analyses acquisition issues and methods that are related to our application, describing: (a) selected hardware; (b) adopted strategy related to the cloud of point acquisition. In Chapter 3, the proposed RE post-processing is described together with a state of art about data segmentation and surface reconstruction. Chapter 4 discusses the proposed algorithms through sensitivity studies concerning thresholds and parameters utilised in segmentation phase and surface reconstruction. Chapter 5 explains briefly the inspection workflow, PDM requirements and solution, together with a preliminary assessing of measures and their reliability. These three chapters (3, 4 and 5) report final sections, called “Discussion”, in which specific considerations are given. Finally, Chapter 6 gives examples of the proposed segmentation technique in the framework of the industrial applications, through specific case studies

Geometrical Error Analysis and Correction in Robotic Grinding

The use of robots in industrial applications has been widespread in the manufacturing tasks such as welding, finishing, polishing and grinding. Most robotic grinding focus on the surface finish rather than accuracy and precision. Therefore, it is important to advance the technology of robotic machining so that more practical and competitive systems can be developed for components that have accuracy and precision requirement. This thesis focuses on improving the level of accuracy in robotic grinding which is a significant challenge in robotic applications because of the kinematic accuracy of the robot movement which is much more complex than normal CNC machine tools. Therefore, aiming to improve the robot accuracy, this work provides a novel method to define the geometrical error by using the cutting tool as a probe whilst using Acoustic Emission monitoring to modify robot commands and to detect surfaces of the workpiece. The work also includes an applicable mathematical model for compensating machining errors in relation to its geometrical position as well as applying an optimum grinding method to motivate the need of eliminating the residual error when performing abrasive grinding using the robot. The work has demonstrated an improved machining precision level from 50µm to 30µm which is controlled by considering the process influential variables, such as depth of cut, wheel speed, feed speed, dressing condition and system time constant. The recorded data and associated error reduction provide a significant evidence to support the viability of implementing a robotic system for various grinding applications, combining more quality and critical surface finishing practices, and an increased focus on the size and form of generated components. This method could provide more flexibility to help designers and manufacturers to control the final accuracy for machining a product using a robot system

Integrated tactile-optical coordinate measurement for the reverse engineering of complex geometry

Complex design specifications and tighter tolerances are increasingly required in modern engineering applications, either for functional or aesthetic demands. Multiple sensors are therefore exploited to achieve both holistic measurement information and improved reliability or reduced uncertainty of measurement data. Multi-sensor integration systems can combine data from several information sources (sensors) into a common representational format in order that the measurement evaluation can benefit from all available sensor information and data. This means a multi-sensor system is able to provide more efficient solutions and better performances than a single sensor based system. This thesis develops a compensation approach for reverse engineering applications based on the hybrid tactile-optical multi-sensor system. In the multi-sensor integration system, each individual sensor should be configured to its optimum for satisfactory measurement results. All the data measured from different equipment have to be precisely integrated into a common coordinate system. To solve this problem, this thesis proposes an accurate and flexible method to unify the coordinates of optical and tactile sensors for reverse engineering. A sphere-plate artefact with nine spheres is created and a set of routines are developed for data integration of a multi-sensor system. Experimental results prove that this novel centroid approach is more accurate than the traditional method. Thus, data sampled by different measuring devices, irrespective of their location can be accurately unified. This thesis describes a competitive integration for reverse engineering applications where the point cloud data scanned by the fast optical sensor is compensated and corrected by the slower, but more accurate tactile probe measurement to improve its overall accuracy. A new competitive approach for rapid and accurate reverse engineering of geometric features from multi-sensor systems based on a geometric algebra approach is proposed and a set of programs based on the MATLAB platform has been generated for the verification of the proposed method. After data fusion, the measurement efficiency is improved 90% in comparison to the tactile method and the accuracy of the reconstructed geometric model is improved from 45 micrometres to 7 micrometres in comparison to the optical method, which are validated by case study

Numerical simulation of an English equestrian Saddletree

A thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Master of Philosophy.The manufacture of horse riding saddlery in the UK is centred in Walsall in the West Midlands. The local industry faces stiff competition from cheap imports in local markets and dwindling exports to international markets. To continue to provide affordable high end products, which the local industry is reputed for, it is essential to develop an understanding of the functional and performance requirements of the saddletree based on scientific and engineering methods thereby laying a foundation for a methodical approach to product development. Through the measurement of surface data from a physical artefact, a 3 dimensional CAD geometrical replica of the English jumping saddletree was developed. Assumptions for the loading and boundary conditions identical to the user environment were obtained from available literature on the movements of the horseback, parameters for a jumping horse, saddletree test data, and, interface contact measurements acquired using a pressure mat. In addition, material properties data were obtained from available literature. Nonlinear static numerical models were subsequently developed and parametric studies were performed to determine the relationship between the deformation of the saddletree and the bending loads. Furthermore, nonlinear transient dynamic numerical models were developed and parametric studies performed to determine the response of the pommel to impact loads. The models were found to be sensitive to loading, material, and geometric parameters. From cantilever tests, the stiffness of the saddletree was found to be between 3.63 N/mm and 4.68 N/mm, and the steel reinforcement plates increased the stiffness by a factor of up to 2.3 times. Simply supported, the stiffness of the saddletree was between 526.62 N/mm and 596.16 N/mm, and the steel reinforcement plates increased the stiffness by a factor of up to 5.5 times. In addition, the simply supported models were sensitive to the wood laminate stacking sequence. Furthermore, the dynamic models showed that the steel reinforcement plates dampened the oscillations in the pommel after impact with a rigid body at 7 m/s, 8.5 m/s, and 10 m/s. The numerical cantilever models were validated with experimental data while interface pressure mat measurements validated interface contact stresses between the deformable bodies and the rigid body surfaces. Interface pressure mat results exhibited pressure hot spots and uneven load distributions underneath the saddletree. Peak and average pressures were 82.7 KPa and 15.4 KPa respectively, representing 16.2 % and 10.0 % error in comparison with the contact stresses obtained from the numerical models. Compression-flexure tests complemented the dynamic models. The steel reinforcement plates were observed to protect the pommel from delamination which was the principal failure mode of the wooden pommel; however, the reinforced pommel failed in flexure. From the simulations and tests performed, it was evident that there is a stiffness mismatch between the saddletree and the horseback which is undesirable. In addition to this significant conclusion, it has been shown that the steel reinforcement plates have a significant effect on the stiffness of the saddletree and do not protect it from failing. Hence, their continued use in the design and manufacturing of the English jumping saddletree is not recommended. Invaluable knowledge gained from the research allowed the definition of the performance attributes in a materials selection process ensuring the choice of potential material candidates to guarantee the optimal performance of the saddletree. Finally, the findings were incorporated in the development of a new concept design for next generation English saddletrees

Advances in Manufacturing Technology XXVII: Proceedings of the 11th International Conference on Manufacturing Research (ICMR2013)

ICMR2013 was organised by Cranfield University on the 19-20 September 2013. The conference focuses on any aspects of product development, manufacturing technology, manufacturing systems, information systems and digital technologies. It provides an excellent avenue for researchers to present state-of-the-art multidisciplinary manufacturing research and exchange ideas. In addition to the four keynote speeches from Airbus and Rolls-Royce and three invited presentations, there are 108 papers in these proceedings. These papers are split into 24 technical sessions. The International Conference on Manufacturing Research is a major event for academics and industrialists engaged in manufacturing research. Held annually in the UK since the late 1970s, the conference is renowned as a friendly and inclusive environment that brings together a broad community of researchers who share a common goal; developing and managing the technologies and operations that are key to sustaining the success of manufacturing businesses. For over two decades, ICMR has been the main manufacturing research conference organised in the UK, successfully bringing researchers, academics and industrialists together to share their knowledge and experiences. Initiated a National Conference by the Consortium of UK University Manufacturing Engineering Heads (COMEH), it became an International Conference in 2003. COMEH is an independent body established in 1978. Its main aim is to promote manufacturing engineering education, training and research. To achieve this, the Consortium maintains a close liaison with government bodies concerned with the training and continuing development of professional engineers, while responding to the appropriate consultative and discussion documents and other initiatives. COMEH is represented on the Engineering Professor’s council (EPC) and it organises and supports national manufacturing engineering education research conferences and symposia