Measurement strategy for a production-related multi-scale inspection of formed work pieces

Part of: Seliger, Günther (Ed.): Innovative solutions : proceedings / 11th Global Conference on Sustainable Manufacturing, Berlin, Germany, 23rd - 25th September, 2013. - Berlin: Universitätsverlag der TU Berlin, 2013. - ISBN 978-3-7983-2609-5 (online). - http://nbn-resolving.de/urn:nbn:de:kobv:83-opus4-40276. - pp. 143–148.The technology of sheet-bulk metal forming provides numerous advantages in the field of manufacturing. Work pieces with filigree and complex structures can be formed by only a few forming steps. To ensure a sustainable and effective production, the forming process has to be controlled by a production-related measurement system. A measurement system, which meets the high requirements of a forming process like a short measuring time, a high measuring point density and the ability to measure different features at the same time, is a multi-scale fringe projection system with multiple sensors of different resolutions. However, an adapted definition of a measurement strategy is necessary in order to enable a rapid conformity decision of the manufactured work piece based on the evaluated measurement data and thus to be able to inspect as many work pieces as possible. It allows to correct the manufacturing during a primary forming process and to assure a sustainable forming process

MUVOT - Establishing an International Vocational Training Program on the Topic of Measurement Uncertainty

Measurement results represent important information, which are necessary for evaluating and improving the quality of manufactured products and to control manufacturing processes. Furthermore, they build the basis for numerous decisions in the field of quality management, process and production automation or product development and design. Knowledge about the acquisition, evaluation and interpretation of measurement data as well as an understanding of the relevant influences on those measurement results are essential for employees working in the field of manufacturing metrology. Measurement results are always afflicted with deviations, due to a variety of causes. It follows that in order to assign a value to the reliability and quality of a measurement result its uncertainty must be determined and considered. However, employees in the field of quality management or metrology are often not familiar with methods for determination and interpretation of measurement uncertainty, because appropriate opportunities for training are missing in current vocational education. This need has led to the creation of the European project MUVoT, which will create a course for advanced vocational training in determining measurement uncertainty. The training course is based on a blended learning concept, combining self-dependent learning via a web-based platform and face-to-face workshops. This allows the adaption of individual knowledge and skills by self-controlled learning of abstract contents whilst the exercises enable the practical application of typical methods, which are generally considered as quite complex by many employees, and thus assure correct understanding. The featured Blended Learning concept facilitates the integration of the training into a workplace setting, thus the idea of Lifelong Learning is promoted in new fields of application. The curriculum and training concept for this newly developed training program have been designed such that the course can be applied internationally. To facilitate this, a harmonized scheme for course structure and contents has been defined albeit with inherent flexibility, allowing the adaptation to specific constraints

Numerical and experimental study of the powder bed characteristics in the recoated bed of the additive manufacturing process

Part of the optimization steps for additive manufacturing is related to the correct understanding of the mechanical behavior of the powder used in the process. Obtain this understanding based purely on experiments might be a difficult and sometimes prohibitive task. A particle-based numerical tool can provide critical information for correct understanding of powder deposition process. Numerical simulations through the Discrete Element Method (DEM) provide a useful mean to investigate the additive manufacturing process, given the possibility to study particle-scale information that are difficult to access experimentally. The characteristics of the recoated powder bed are investigated in the packed bed region and onto the manufactured part using PA12 commercial powder. Particle size distribution, contact and non-contact cohesive forces are incorporated in the numerical model. Furthermore, the non-spherical shape of real particles is taken explicitly into account in numerical simulations. A blade-type recoating system is used to form the powder bed and its roughness is calculated. Experimental measurements are performed by fringe projection. Several areas of the recoated powder layers can be scanned with this optical measurement method. Thus, the analyzed surface roughness can be compared with the simulated quantities to validate the numerical model. The sintered part is modelled as a prescribed rigid static region in the simulated system. The powder recoated in the sintered region may have different characteristics (packing, roughness) compared to the powder bed region. Recoating process is modelled using two different shapes for the sintered region. The amount of material recoated and the surface roughness are then calculated for the powder bed as well as for the sintered region

Friction identification and compensation on nanometer scale

This work concerns the modelling and experimental verification of the highly nonlinear friction behavior in positioning on the nanometer scale. The main goal of this work is to adjust and identify a simple dynamic friction model which allows a model-based estimation of the friction force in combination with the system inertia against displacement. Experiments in the pre-sliding and sliding friction regimes are conducted on an experimental setup. A hybrid two-stage parameter estimation algorithm is used to fit the model parameters based on the experimental data. Finally, the identified friction model is utilized as a model-based feedforward controller combined with a classical feedback controller to compensate the nonlinear friction force and reduce tracking errors

Geometrical Product Specification and Verification as toolbox to meet up-to-date technical requirements

The ISO standards for the Geometrical Product Specification and Verification (GPS) define an internationally uniform description language, that allows expressing unambiguously and completely all requirements for the geometry of a product with the corresponding requirements for the inspection process in technical drawings, taking into account current possibilities of measurement and testing technology. The practice shows that the university curricula of the mechanical engineering faculties often include only limited classes on the GPS, mostly as part of curriculum of subjects like Metrology or Fundamentals of Machine Design. This does not allow students to gain enough knowledge on the subject. Currently there is no coherent EU-wide provision for vocational training (VET) in this area. Consortium, members of which are the authors of this paper, is preparing a proposal of an EU project aiming to develop appropriate course

Friction identification and compensation on nanometer scale

This work concerns the modelling and experimental verification of the highly nonlinear friction behavior in positioning on the nanometer scale. The main goal of this work is to adjust and identify a simple dynamic friction model which allows a model-based estimation of the friction force in combination with the system inertia against displacement. Experiments in the pre-sliding and sliding friction regimes are conducted on an experimental setup. A hybrid two-stage parameter estimation algorithm is used to fit the model parameters based on the experimental data. Finally, the identified friction model is utilized as a model-based feedforward controller combined with a classical feedback controller to compensate the nonlinear friction force and reduce tracking errors