Contrôle qualité | EPFL Graph Search

vignette|Contrôle qualité du nylon, 1954, Malmö. Photographie conservée au musée nordique. Le contrôle qualité est un aspect de la gestion de la qualité. Le contrôle est une opération destinée à déterminer, avec des moyens appropriés, si le produit (y compris, services, documents, code source) contrôlé est conforme ou non à ses spécifications ou exigences préétablies et incluant une décision d'acceptation, de rejet ou de retouche. Enjeux du contrôle qualité L'ancienne norme ISO 8402 (maintenant annulée) en donnait la définition suivante : (ISO8402:1994, § 2.15.). Le contrôle est un acte technique permettant de déterminer la conformité d'un produit. Pour effectuer un contrôle sur un produit, il faut au préalable en déterminer les caractéristiques et choisir les limites (les usineurs diraient les tolérances) à l'intérieur desquelles le produit est conforme. Il faut que ces limites soient connues par le « contrôleur » qui effectuera le contrôle. Il implique également qu

Study of physical phenomena of selective laser melting towards increased productivity

Christoph Van Gestel

This thesis presents an experimentally focused study of three of the key physical phenomena of the Selective Laser Melting (SLM) process. The SLM process increasingly gains momentum in industrial applications. As awareness of the process and its capabilities for the manufacturing of high performance objects increases, some of the current limitations of the process become more apparent. The SLM process is not a fully mature manufacturing process and there are still significant gains to be made in terms of material understanding, process optimization, final part prediction and quality control. The experimental study of the physical aspects contributes to the material understanding on a fundamental level but also provides the tools for facilitating future research. A link to practical applications is presented in a case study on evaluating the influence of beam movement patterns and on the identification of process instabilities for quality control. A broad literature survey covers the state of the art on improving the SLM process. The three physical phenomena which are the subject of this study are: the interaction of laser beam light with the material to be processed, the transport of heat within the material and the behavior of the molten material. These three phenomena take place under conditions which are unlike conventional production processes, in terms of energy intensity, thermal gradients and liquid (metal) dynamics. The laser-material interaction is characterized by the absorptance. An integrating sphere setup is integrated in an SLM machine to measure the absorptance of the material in the pristine and final state. Also the absorptance evolution is characterized. Results are available for Maraging 300 steel powder, silver powder and AlSi10Mg powder. The influence of surface oxidation and surface roughness is discussed. The heat transport within the powder bed is characterized by diffusion. The thermal diffusivity and thermal conductivity are measured using the flash method with a laser as the energy source. The implementation uses a special laser beam intensity profile and data processing by correlation with numerical simulations. Thermal diffusivity and conductivity values are included for Maraging 300 steel, silver and titanium. The results confirm the large difference between bulk and powder conductivity and the limited influence of the material type. The melt pool behavior is studied using an integrated coaxial vision system. This system uses a combination of sensors to monitor the radiation which is emitted by the melt pool and its surroundings. The implementation presents optimized timing and data processing protocols. The relation between the melt pool properties and the process stability is explained. A procedure is also developed for obtaining temperature field profiles of the melt pool.

EPFL2015

Spot Identification and Quality Control in Cell-Based Microarrays

Michael Bauer, Blaise Calpe

Cell-based microarrays are being increasingly used as a tool for combinatorial and high throughput screening of cellular microenvironments. Analysis of microarrays requires several steps, including microarray imaging, identification of cell spots, quality control, and data exploration. While high content image analysis, cell counting, and cell pattern recognition methods are established, there is a need for new postprocessing and quality control methods for cell based microarrays used to investigate combinatorial microenvironments. Previously, microarrayed cell spot identification and quality control were performed manually, leading to excessive processing time and potentially resulting in human bias. This work introduces an automated approach to identify cell based microarray spots and spot quality control. The approach was used to analyze the adhesion of murine cardiac side population cells on combinatorial arrays of extracellular matrix proteins. Microarrays were imaged by automated fluorescence microscopy and cells were identified using open source image analysis software (CellProfiler). From these images, clusters of cells making up single cell spots were reliably identified by analyzing the distances between cells using a density-based clustering algorithm (OPTICS). Naive Bayesian classifiers trained on manually scored training sets identified good and poor quality spots using spot size, number of Cells per spot, and cell location as quality control criteria. Combined, the approach identified 78% of high quality spots and 87% of poor quality spots. Full factorial analysis of the, resulting microarray data revealed that collagen IV exhibited the highest positive effect on cell attachment This data processing approach allows for fast and unbiased analysis of cell-based microarray data.

Amer Chemical Soc2012

A review of different techniques to characterise the mechanical properties of SLS parts - focus on resistivity measurements

Eric Boillat, Dylan Fivat, Rémy Glardon, Jamasp Jhabvala, Marc Matthey

As SLS has now been established as a rapid freeform fabrication technique in a growing application field (aerospace, tooling, bone and dental implants etc.), one feels more severely the lack of non-destructive, reliable and recognised diagnostic methods for the mechanical characterisation of SLS parts (quality control).

Crc Press-Taylor & Francis Group, 6000 Broken Sound Parkway Nw, Ste 300, Boca Raton, Fl 33487-2742 Usa2012

Study of physical phenomena of selective laser melting towards increased productivity

Christoph Van Gestel

EPFL2015