**1. Introduction**

146 Biomedicine

Tiwari U., Mishra V., Poddar G.C., Kesavan K., Jain S.C., Ravisankar K., Singh N. & Kapur

Tiwari U., Mishra V., Bhalla A., Singh N., Jain S.C., Garg H., Raviprakash S., Grewal N. &

Webb D.J., Hathaway M.W., Jackson D.A., Jones S., Zhang L., Bennion I. (2000) First in-vivo

Wehrle G., Nohama P., Kalinowski H., Torres P.I. & Valente L.C.G. (2001) A fiber optic

Yang C., Zhao C., Wold L., Kaufman K.R. (2003) Biocompatibility of a physiological

Capability of Mouthguards, Dental Traumatology, vol.27: 263-268.

Grating Sensors, *Current Science*, vol. 97(11) 1539-42.

pressure sensor, *Biosensors and Bioelectronics* vol.19: 51-58

vol.5: 45–50

*Technol*. vol.12: 805–809

P. (2009) Health Monitoring of Steel and Concrete Structures using Fiber Bragg

Kapur P. (2011) Fiber Bragg grating Sensor for Measurement of Impact Absorption

trials of a fiber Bragg grating based temperature profiling system, *J Biomed Opt*,

Bragg grating strain sensor for monitoring ventilatory movements, *Meas. Sci.* 

In recent years, European industry has been facing the challenge of losing competitiveness in mass production. Due to important factors such as lower labour costs, lower taxes or insite access to raw materials, mass production has migrated to Third World countries. However, European industry is more advanced in technological aspects and is in need of a qualitative advantage in the development of new technologies. One of the efforts of European companies is directed towards the production of short series of customized products with added value. Major efforts have been done in order to customize products and give them an added value by developing new manufacturing technologies.

Additive Manufacturing (AM) is a powerful tool that offers the necessary competitiveness to European companies (Petrovic, 2011). AM technologies have been available on the market for many years. Initially, these technologies were considered only for prototyping - the first technologies that appeared on the market were capable of fabricating only polymer parts of low quality and low resistance. However, in the last decade, the sector of AM has experienced an important evolution with constant growth in sales of machine systems and rapid products (Wohlers, 2010). Numerous advantages of 'freeform fabrication' have driven new developments in processing principles and materials. New value-added materials have been released for layer-by-layer processing. On the other hand, new technologies have been developed to process demanding materials for different sectors. New energy sources have been introduced in order to process high melting point metal alloys such as Titanium, Cobalt Chromium, etc.

There are many terms commonly used for AM, such as solid *free form fabrication* (FFF), *rapid manufacturing* (RM), *additive layered manufacturing* (ALM) and *3D printing.* The latter may be the most descriptive for people not familiar with additive technologies. Unfortunately, this term may produce a wrong idea, since AM machinery is much more than any kind of printer. However, officially and according to ASTM F42 Committee, Additive Manufacturing is defined as "process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies, such as traditional machining" (ASTM, 2010).

AM enables the use of **value-added design** in medical device manufacturing sector. Process of adding material in layers allows the fabrication of *designed, controlled and well-*

Additive Manufacturing Solutions for Improved Medical Implants 149

processed. The part is oriented for building and a support structure is made for the downfacing surfaces of the part. Afterwards, cross-sections of a given thickness, known as 'slices', are generated virtually from 3D CAD descriptions of the part and support structures. The slices are saved in a 'slice file' (ABF, SLI, SLC or any other format that may depend on patented technology). After pre-processing, the slice file is sent to the machine to

The fabrication process consists of two basic steps: *coating* and *selective melting*. The coating step is the process in which material is laid over the working surface in a very thin layer. The thickness of the layer depends on the chosen technology and it ranges between 0.03 mm to 0.20 mm. The selective melting step refers to the process of printing the part slice by the action of a source of energy. The active principle can be a *light source*, *laser beam*, *electron beam*, etc. It acts over the layer of material and produces fusion of slice's footprint to the layer below. The power of the energy source depends on the chosen technology: in the low end, we have Stereolithography that uses ~100 mW, and in the high end, we have Electron Beam Melting that uses up to 3000 W. Only the contour of part slice and its interior are fused (Figure 2, right); the rest of the material is left untouched and may be recycled (more or less, depending on the process and material). The actions of coating and slice printing follow each other until all the slices are correctly printed, generating the final threedimensional part. Once fabrication has finished, the part is taken out to be cleaned of

be 'printed' slice-by-slice.

Fig. 2. Steps in AM process (left) and fused layer (right)

*interconnected porosity* which, combined with solid material, provides better bone ingrowth into implants. Also, AM implants are characterized by *rough surface quality* per se. Undesirable in other sectors, in medical implants rough surface is an advantage because it enhances bone-implant fixing. Furthermore, AM technologies perform fabrication of metal implants in a highly controlled atmosphere with restricted presence of oxygen, which results in especially *high purity*. Finally, layer-by-layer principle allows the fabrication of *customized net-shape implants* that fully fit patient's data. In addition, high power and processing velocity open the possibility of serial production of *standardized implants*.

Fig. 1. Acetabular cup with designed porous surface (Courtesy of ARCAM AB).

The aim of this chapter is to illustrate the capabilities of AM on the example of a technology with one of the most powerful active principles: Electron Beam Melting (EBM).
