| 1. |
- Arino, I., et al.
(författare)
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The Influence of the Measuring/Viewing Angle on the Color of Injection-Molded Plastics
- 2010
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Ingår i: International Journal of Polymeric Materials and Polymeric Biomaterials. - : Informa UK Limited. - 0091-4037 .- 1563-535X. ; 59:4, s. 292-306
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Tidskriftsartikel (refereegranskat)abstract
- A multi-angle spectrophotometer was used to measure the CIELab coordinates L∗, a∗ and b∗ in different angles relative to the incident light. The specimens used were acrylonitrile-butadiene-styrene injection-molded plaques in different colors and with different surface textures. Variations in the coordinates when changing the measuring angle depended on the color and the texture. In general, however, smooth (glossy) surfaces were measured to be darker and of higher chroma than textured surfaces and as the gloss of the surfaces decreased (due to texturing), the lightness of the surfaces increased and the absolute values of a∗ and b∗ decreased over the range of measuring angles (not too close to the specular reflection angle). A psychometric study involving a human test panel was used as a complement to the measurement. The agreement between the measurements and this study cannot be said to be satisfactory, unless the variation in the color coordinates was quite clear. Possible reasons are discussed.
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| 2. |
- Dimkovski, Zlate, 1974-, et al.
(författare)
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Evaluation of Durability of SOG-layers on Steel Surfaces by Wear and Scratch Tests
- 2014
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Konferensbidrag (refereegranskat)abstract
- Steel moulds with high precision surfaces are being used in various branches. Process aspects, like tool life and tribological properties, as well as design issues are of great importance. This work summarises experimental studies performed to test durability properties of SOG (spin-on-glass)-layers on steel surfaces. This coating technique is based on a newly developed method for surface preparation of tools which has been demonstrated to be durable for more than 66.000 replications in injection moulding processes without loss of surface fidelity. The procedure allows surface roughness reduction from approximately 200 nm Ra down to some few nm for high gloss applications, as well as easy transfer of large-area functional nanostructures on complex 3D surfaces.Three different types of surfaces were investigated: SOG-layered metal surfaces with three different layer thicknesses, one ingot casted and one electro slag remelted material (with hardness level of 950 and 2500 MPa, respectively). The metal surfaces were ground and polished to mirrorlike finishes.Three circular samples of each type were rubbed against a hard steel ball of 6.35 mm radius on a commercial pin-on-disk tribometer. To resemble the molding process a sliding speed of 2 mm/s and a load of 8 N were chosen. The tests were performed with 5 minutes intervals until the first damage on the surface were observed. In parallel, scratch tests were performed in the same tribometer. The surfaces were measured in-situ by a portable microscope and a stylus, and afterwards by a white light interferometer and scanning electron microscope to evaluate the size of the wear/scratch traces.The surface type with the longest time to damage and/or smallest wear/scratch traces was considered to be the most durable one.
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| 3. |
- Rebeggiani, Sabina, 1980-, et al.
(författare)
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A measure of perceived quality to secure the polishability of new paint systems
- 2023
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Ingår i: Surface Topography: Metrology and Properties. - Bristol : Institute of Physics (IOP). - 2051-672X. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- The automotive industry continuously strives to reduce their environmental impact. For the paint shop it means to introduce more sustainable paint concepts, while maintaining the production rate and retain the right surface appearance that is crucial for the vehicle’s perceived quality. Today most painted parts are visually inspected and, if needed, manually repaired by abrasive polishing to eliminate spot defects. The repair process consists of one sanding step to remove the defect, and one or two rubbing/polishing steps to restore the surface, but still it tends to be a non-reliable process leaving patterns or clusters of shallow micro scratches seen as three-dimensional shapes moving over the surface when viewed from different angles like holograms. These so called ‘polishing roses’ are hard to detect in artificial light but clearly visible in Sunlight and therefore they constitute a constant quality issue. Accurate polishing procedures in combination with more objective inspection techniques would secure a high surface quality—but what is ‘accurate’? The overall scope of the study was to deepen the knowledge of paint systems to develop test routines for the polishability of coatings already during the development stage, and thereby ease the implementation of new coating systems in production. The study was based on collected process data from professional polishers to define a process window based on key parameters for successful end-of-line repairs of coated surfaces, i.e. strategies minimizing the occurrence of visible polishing traces. A CNC-machine was built up for the purpose to systematically test and evaluate new coating systems and repair procedures. The surface estimation was made by visual inspections as well as by a further developed photometric stereo system providing quantitative images of remaining repair traces. © 2023 IOP Publishing Ltd
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| 4. |
- Rebeggiani, Sabina, 1980-, et al.
(författare)
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A Step-by-Step Analysis of Manual Polishing Sequences
- 2012
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Ingår i: Proceedings of the 9th International Tooling Conference. ; , s. 317-324
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Konferensbidrag (refereegranskat)abstract
- Polishing of tool steels for e.g. injection moulding of plastic parts or direct polishing of products is perhaps the most important industrial finishing process today. Polishing is often made manually to ensure the highest quality and nanometre roughness. This study compare steel samples prepared in different companies to study how different polishing sequences affect final surface qualities, i.e. trying to find crucial factors controlling high gloss appearance and defect levels. The samples were prepared in a way that every step of the polishing process could be studied quantitatively at nanometre level using phase shifting- and coherence scanning interferometry. In addition, all samples were qualitatively documented and judged visually by the polishers themselves. It could be concluded that a ‘several-step’ strategy in combination with short polishing time was advantageous. Also, guidelines for tool and abrasive selection is presented suggesting cotton as carrier and diamonds of 1 µm size for more time efficient final polishing.
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| 5. |
- Rebeggiani, Sabina, 1980-, et al.
(författare)
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A Training Consortium to Explore and Exploit Surface Metrology
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The importance of surface finish in all aspects of manufacturing influences economic considerations as well as environmental aspects and functionality. The ability to effective and efficient characterise surface topography is an important tool in the manufacturers arsenal which is often overlooked or underutilised. By providing a comprehensive, affordable training package, a gap in the industrial knowledge is filled giving manufacturers the ability to increase their competitive edge.
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| 6. |
- Rebeggiani, Sabina, 1980-, et al.
(författare)
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Detection of paint polishing defects
- 2018
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Ingår i: Surface Topography: Metrology and Properties. - Bristol : Institute of Physics Publishing (IOPP). - 2051-672X. ; 6:2
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Tidskriftsartikel (refereegranskat)abstract
- Surface finish plays a major role on perceived product quality, and is the first thing a potential buyer sees. Today end-of-line repairs of the body of cars and trucks are inevitably to secure required surface quality. Defects that occur in the paint shop, like dust particles, are eliminated by manual sanding/polishing which lead to other types of defects when the last polishing step is not performed correctly or not fully completed. One of those defects is known as 'polishing roses' or holograms, which are incredibly hard to detect in artificial light but are clearly visible in sunlight.This paper will present the first tests with a measurement set-up newly developed to measure and analyse polishing roses. The results showed good correlations to human visual evaluations where repaired panels were estimated based on the defects' intensity, severity and viewing angle.
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| 7. |
- Rebeggiani, Sabina, 1980-, et al.
(författare)
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Empirical Evaluation of Spin-on-Glass-Layers on Steel Surfaces by Wear Tests
- 2014
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Ingår i: Tribologia Finnish Journal of Tribology. - Helsinki, Finland : Helsinki University of Technology. - 0780-2285. ; 32:1, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- Dies and moulds with high precision surfaces are being used in various branches, e.g. in the plastic industry where the surface finish are conventionally performed by manual polishers. With ever increasing demands of shorter lead times and reduced costs, efforts have been made to automate this finishing process. This paper presents an empirical study performed to test durability properties of SOG (spin-on-glass)-layers on steel surfaces. The results showed that the thin coating last longer than the thicker ones, and that the harder coatings withstood wear significantly better than the steel reference samples thus motivating further investigations.
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| 8. |
- Rebeggiani, Sabina, 1980-, et al.
(författare)
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Factors influencing the surface quality of polished tool steels
- 2014
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Ingår i: Surface Topography: Metrology and Properties. - Bristol : Institute of Physics Publishing (IOPP). - 2051-672X. ; 2:3
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Tidskriftsartikel (refereegranskat)abstract
- Today’s demands on surface quality of moulds for injection moulding of plastic components involve no/low defect contents and roughness levels in the nm-range for high gloss applications. Material properties as well as operating conditions influence the mould finish, and thus the final surface of moulded products. This paper focuses on how particle content and different polishing strategies influence final surface qualities of moulds. Visual estimations of polished tool steel samples were combined with non-contact 3D-surface texture analysis in order to correlate traditional assessments to more quantitative methods, and to be able to analyse the surfaces at nanometer-level.It was found that steels with a lower proportion of particles, like carbides and oxides, gave rise to smoother polished surfaces. In a comparative study of polishers from different polishing shops, it was found that while different surface preparation strategies can lead to similar final roughness, similar preparation techniques can produce high-quality surfaces from different steel grades. However, the non-contact 3D-surface texture analysis showed that not all smooth polished surfaces have desirable functional topographies for injection moulding of glossy plastic components.
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| 9. |
- Rebeggiani, Sabina, 1980-, et al.
(författare)
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On communicating extruded aluminium surface quality along the supply chain : a customer approach to sustainable surfaces
- 2023
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Ingår i: Surface Topography: Metrology and Properties. - Bristol : Institute of Physics (IOP). - 2051-672X. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Today, far too many products are scrapped due to surface related issues, products with perfect function but with minor surface blemishes. The complaints are often offset by goodwill commitments from suppliers at great cost to them and delivery delays and lead time costs for customers. The reason is that the industry relies on several non-standardized classification systems for surface quality that are based on various combinations of and designations for surface defects, assessed by visual inspections at a defined distance to determine the severity of any detected surface deviations. These similar classification systems provide far too much scope for subjective and non-repeatable assessments causing communication problems between customer and producer at all stages in the supply chain. To challenge this situation, a common toolbox to communicate, describe and define surface quality should be developed, i.e. a standardisation of surface quality assessment including various effects and defects with a jointly established nomenclature and evaluation parameters. This work presents the first step of a research project bringing together 11 suppliers and OEMs along the supply chain, from the delivery of raw aluminium to finished alumina profiles included in consumer products. The final goal of the project is to develop an ‘objective classification of visual requirements’ on alumina profiles towards increased sustainability and decreased material wastage. Presented result is a common terminology with links to the process chain, surface defect geometry and visual appearance aiming at making the communication between producers and buyers of the aluminium profiles clearer and more unambiguous when it comes to specification and requirements of profile surfaces in each of the supply-chain links. Future work will add measurable parameters specifying surface quality.
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| 10. |
- Rebeggiani, Sabina, 1980-
(författare)
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On Polishability of Tool Steels
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One of the world’s fastest growing industries is the plastic industry. Today’s ever increasing demands of high quality products, shorter lead times and reduced costs push development and research forwards. Moulds for plastic injection moulding need to have a functional surface to meet demands on demoulding and wear properties, but also to produce the required final surface quality, which for ‘standard mould qualities’ of high gloss applications means nearly defect free, shiny and smooth mould surfaces with roughness levels in the nm-range.The aim of this thesis was to develop a metrology framework to quantitatively characterise these mould surfaces in order to gain better understanding of which defect structures are critical at injection moulding, and how these are correlated to material properties and operating conditions in surface preparation of tool steels. In practice this means to capture surface features of some few nm in height/depth up to some hundreds of microns in lateral dimension within insert areas of cm2 and larger. Experiments combining polishers’ experience with steel producers’ as well as non-contact areal texture examinations of surface topography were performed to overcome and link practical skills to academic ones.Based on areal surface metrology, defect classification and image analysis based surface characterisation, an evaluation procedure for polished tool steel surfaces was developed, initially tested and verified. The suggested method involves descriptions of relevant defect structures and acceptance levels for high gloss polished tool steels in the form of numerical parameter values based on interferometric measurements. It was also concluded that the cleanness of the steels was less important as long as it was kept within reasonable levels; the surface preparation strategy is a major factor influencing the mould surface quality e.g. it was found that a ‘several-step-strategy’ was favourable to avoid defect structures; not all ‘mirror-like’ mould surfaces had desirable topographies for injection moulding, therefore a well-defined mould surface assessment with numerical values describing mould surface quality is necessary to secure effective mould surfaces.
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