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Application in the sector biomédico

Additive manufacture: present and future of the implants biomédicos

Dr. Vojislav Petrović, New Processes of Manufacture, Aimme 11/01/2013

In the last times, the European industry has seen to diminish his competitiveness in the massive production of pieces, in front of third countries that are experiencing a big industrial development. This has to fundamentally to some of the competitive advantages of these countries: hand of work of lower cost, taxles lower and direct access to the raw materials. Nevertheless, Europe follows being in command of the technological advances, which allows him keep the leadership in relation with the development of personalised products and of high value added. In particular, one of the niches where the European companies have potential elder, is the one of manufacture of short series, of personalised products, using technologies of manufacture advanced.

The Additive Manufacture (FA), also known like Fast Manufacture or 3D Printing, is precisely one of these technologies advanced that allows to realise ‘complex designs and perfectly adapted to the functionality of the product'. Arisen in the decade of the ninety, these technologies used mainly to manufacture low quality visual prototypes and resistance. In the actuality, and after two decades of evolution so much in material as in the active principles of the processed, the FA is able to process metallic alloys of high provision, such like titanium, chromium cobalt, steel, etc. Simultaneously, the philosophy of manufacture by layers, that allows a free design of technological limitations, has gone calando in the world of the industrial designers and engineers, by what the FA has every time greater acceptance in the industry. The sector of ‘products biomédicos' is one of which better can take advantage of the value added of the Additive Manufacture by several reasons. In the first place, manufacture material by layers allows to obtain ‘implants with porous zones', in which the pores are ‘custom-made, with size controlled' and ‘very very connected'. Some studies, indicate that the osseous cells grow very well through titanium manufactured by means of FA and produce an excellent osteointegración of the implant. The implants of titanium manufactured by means of this technology combine a solid body with porous regions in an alone piece, which allows them offer high provision and a high osteointegración. Second, the majority of pieces manufactured by means of FA are used to to require a postprocesado mechanical, with the end to obtain a similar superficial quality to which would obtain by means of mechanised. However, in the medical implants this peculiarity results advantageous, since the rugosidad superficial is a positive factor, since it allows a better fixation of the implant to the osseous element. In third place, the ‘freedom of forms and design' that characterises to the pieces manufactured by means of FA, is essential, since it allows to produce implants absolutely personalised, to measure of the patient in question. Finally, but no less important, the selective fusion of material when it uses this type of technologies, is used to to produce in special atmosphere (inert or empty gas) which awards to the pieces a high purity. The case of study showed in the Figure 1, realised jointly by Aimme and the Institute of Biomecánica of Valencia, offers a complete vision of the previously described characteristics.

It appears 1. Vástago Of custom-made hip (titanium 6-aluminium 4-vanadium), with superficial porous zone for better osteointegración, fit in the model of the patient fact in estereolitografía.

Technical characterisation

One of the most complete definitions of Additive Manufacture is the one who established the Committee F42 of the ASTM (American Society for Testing and Materials). According to the ASTM F2792-12to ‘Standard Terminology for Additive Manufacturing Technologies', the Additive Manufacture has been defined like “process of union of materials to create objects, from the information contained in a model 3D, usually layer by layer, by comparison to technologies of manufacture by subtraction, as it is the mechanised traditional” (ASTM, 2010).

The additive manufacture of an implant initiates with the segmentation of the model 3D of the same in layers very fine (of 30 to 100 µm, according to the technology). The file that contains the information of the group of layers (with the extension.SLI, .SLC, .ABF; According to the technology patented) is envoy to the system of additive manufacture, that reconstructs layer by layer the physical model of the piece in the material wished. Said reconstruction consists in the deposition of a fine layer of metallic dust and the application of a source of power (generally do of laser or do of electrons) on her. The deposition of the first layer realises on a plate of manufacture and afterwards layer on layer. The no reached material by the do remains intact and can recycle for the following manufacture. The result of the manufacture is an identical physical piece to the model 3D of the implant. If necessary, the piece can subject to postprocesado mechanical (mechanised of surfaces of assembling, polishing, etc.) and thermal sensors (homogenisation, HIP, etc.).

It appears 2. Stages that compose the Additive Manufacture.

The flow of work in the manufacture of implants by means of FA consists in: design of the implant or in his case reconstruction according to images CT, preprocesado virtual (creation of the archive capeado), digital direct manufacture of the implant, postprocesado mechanical and thermal sensors (if it results necessary), postprocesado sanitary ware (sterilisation, packaging, etc.) and surgical implantation like final step.

It appears 3. Flow of work in the manufacture of personalised implants using technologies of FA.

Even being a flow of similar work to the gone on down conventional technologies (forges, the mechanised, etc.), the manufacture of implants by means of FA has important advantages in the production of the implants customizados:

Reduction of the time of delivery, because of high productivity and direct manufacture of the electronic model;
High capacity of customización with flexibility of total design, including custom-made porous zones, internal channels, etc;
substantial Saving in material, because of the recycled complete of the no processed material;
Absence of toolings and moulds, because of the direct manufacture of the product;
identical mechanical Provision to the material colado or forged, because of a complete local fusion of dust.

At the same time, the FA has a singular characteristic very valued in the manufacture of personalised products of all type. The camera of manufacture has a middle-sized volume of 250x 250x 250 mm. Like general rule, all the models that can fit in the volume of the camera of manufacture, are manufactured at the same time, since the machine does not interpret models but the layers housed in the archive capeado. Therefore, unlike other processes of manufacture, where each personalised implant is manufactured individually, by means of the FA can manufacture at the same time multiple implants, entirely distinct and customised according to the concrete patient. In the Figure 4 shows a conjoint manufacture of 21 plates of osteosíntesis of fisionomía different. Can manufacture at the same time implants entirely customised reduces costs of manufacture of way very significant and improves the competitiveness of the price offered.

It appears 4. An example of conjoint manufacture of different personalised implants in a same manufacture (cuttingesy of Surgival).

Like this then , results evident that the Additive Manufacture is a very competitive option to the hour to manufacture series relatively short of implants, with high added value and high level of personalización. However, it does not be necessary to forget that with this type of technologies does not pretend substitute the conventional technologies, since the FA can not compete in the manufacture of big series of implants standardised in sizes. However, the development of new materials, the technological improvement, the increase of productivity and the cheapening of equipment around the Additive Manufacture, are realities that go observing year after year, by what seems logical to consider that these technologies can represent the future, no only of the production of medical implants, but of other a lot of sanitary ware products.

Petrovic V et al. (2011). To study of mechanical and biological behavior of porous You6To the4V fabricated on EBM. Innovative Developments in Virtual and Physical Prototyping – Proceedings of VRAP 2011, 28 Sep – 01 Oct, Leiría, Portugal.

Thomsen P. Et al. (2009). Electron beam-melted, free-form fabricated titanium alloy implants: Material surface characterization and early bone response in rabbits, Journal of Biomedical Materials Research Part B: Applied Biomaterials Vol 90B, Iss 1, pg 35–44 (2009).