Partenaires et organisations internationales
(Anglais)
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PHILIPS CFT, Eindhoven (NL), SANDVIK COROMANT, Stockholm (S),
Modular InkJet Technology (MIT), Jarfälla (S), Merck KGaA, Darmstadt (D), Fraunhofer Institut für Silicatforschung (FHG-ISC),
Würzburg (D), Universität Groningen, Groningen (RuG) (NL)
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Résumé des résultats (Abstract)
(Anglais)
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Industrial companies manufacturing complex millimetre-sized ceramic mass products, typically made from plates or bars containing many products suffer the problems of the complexity and inflexibility of the batch oriented processes. The separation of ceramic microparts causes up to 30 % waste of material. Ceramic products seriously deform during sintering. Ceramic foils cannot be made in layers below 5 um thick but much thinner layers are wanted. In the coating industry the usual CVD process for wear resistant layers is very time consuming and cannot be applied locally.
The new technology was supposed to offer product design freedom in ceramics, glass and even metals. In principle also UV-curing plastic monomers could be processed using a UV laser (stereolithography with inkjet). The proposal suggested to print a sol of nanosized particles by inkjet technology and to dry and laser sinter the printed ceramics using one single on-line system. Multiple process cycles ('stereostiction') may provide composite ceramic / metal / glass structures of arbitrary patterns (also 3-dimensional) without subsequent subtractive shaping, trimming or product separation. Due to the additive nature of the new technology and the flexibility of both inkjet and laser technology the main benefits expected were:
· Reduction of manufacturing costs by up to 5 X reduction of number of processing steps
· Full software control allows mass production with batch size of 1 piece
· Additive processes produce no waste material for product separation, giving up to 30 % material cost reduction and environmental load.
· Minimum layer thickness 0,1 um; nominally 0.1 ... 0.5 um per printing pass.
· Printing speed is at least 5 cm2/sec, the aim is 50 um line width and 5 um landing accuracy.
The first objective was 2-D local patterning of wear-resistant layers on various materials. The second objective was 2-D patterning and composite generation using the 'multicolour' capability of inkjet technology using colloidal sols of different materials made via the sol-gel route instead of coloured inks. The third objective was 3-D shaping with ready sintered ceramics in multi-pass with a sliced CAD-design where patterns are stacked. The fourth objective was reduction of costs and environmental impact by the additive nature of the technology and by the use of water based matrices instead of organic solvents.
The consortium had strong complementary expertise and comprises two industrial users of the new technology and know-how: Philips for high tech electronic products and Sandvik for high quality cutting tools. All partners were developers/suppliers: Merck introduced its expertise for practical industrialisation, Pelikan brought its ink expertise, Xaar Jet AB brought inkjet system expertise, FHG-ISC brought sol-gel expertise, Philips brought laser technology, Sandvik brought wear-resistance expertise and RuG brought interface and microstructure expertise. The industrial partners were responsible for process development together with FHG-ISC (sol-gel formulation) and Groningen University (metal-ceramic interfacing). Pelikan formulated the base sols to printable liquids and acted as the industrial supplier while Xaar Jet AB developed the print head and built the prototype system with the purpose to market the system. Philips developed the embedded laser technology.
Principles of the sintering process were investigated using the dip and spin coating technique for manufacturing mono and composite layers early in the project A prototype ACERLINK system comprising an inkjet printer and a laser system was built by Xaar Jet AB. High cycle speed was obtained using a high speed multiple nozzle print head.
Basic ink formulations were developed for the SiO2 sinter material. On the same basis, a stable ink also for ZrO2 was obtained. For Al2O3 and ZrO2/Ni, on the other hand, the same ink system provided printable inks but did not meet the requirements of colloidal stability. The most promising precursors of SiO2 and ZrO2 were used for the subsequent surfactant evaluation. Ink formulations which resulted from surfactant evaluation allowed to print crack-free patterns on fused silica and steel substrates.
Suitable polymers were evaluated which were supposed to improve particle distribution in the aqueous zirconia ink during drying. A polymer was found which provided good drying properties of the ink and in addition, enhanced the printing reliability of the print head. The resulting ZrO2 ink was applicable to glass and steel substrates but still suffered from lacks such as maximum sinterable layer thickness and tendency to uneven material distribution. Industrial applications were tested at Philips CFT. Promising results were obtained when the ink was used for friction reduction of trimmer knives. Applicability for 3-dimensional structures needs further tests and possibly development work.
In summary, acerlinkability seem to request a set of system properties which have too many contradictory aspects and thus, the proposed matrix of sinter material and substrate types could not be covered on a common process and material basis. Acerlinkability needs individual development for each sinter material/substrate pair.
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