Med-Tech Innovation 3D printing
Processing 3D printed TITANIUM IMPLANTS
Kaitlyn Calaluca of Lucideon discusses additive layer manufacturing of titanium implants and the issues that manufacturers need to address to ensure the cleanliness of these products.
common methods for creating a porous surface structure for effective osseointegration of these devices. Each of these coating methods generates a unique porous surface structure and effi cacious methods have evolved over the years to ensure cleanliness of the fi nal device. The use of several new additive layer manufacturing (ALM) methods to fabricate implant devices with integrated porous surface structures has presented new challenges to achieving the required level of cleanliness of these products. ALM, commonly referred to as 3D printing, includes the use of electron beam melting (EBM) and direct metal laser sintering (DMLS) for the production of Ti components.
P The process methods
Fine metal powder is the basis for both EBM and DMLS methods and the properties of the powder affect the way it compacts and fl ows, which ultimately affects the fi nal ALM product. The powder is spread on a substrate, which is lowered on a piston after each successive
24 ¦ September/October 2014
orous-layer coated titanium (Ti) medical and dental implants have been the industry standard for several decades. Sintered wire or beads, and plasma sprayed Ti coatings have been the most
layer of material is sintered or melted. Because the part is surrounded by unsintered powder at all times, these manufacturing methods do not require any dedicated support structures or tooling. This allows for the construction of complex geometries. EBM uses an electromagnetically directed electron beam energy source to melt fi ne metal powder in a vacuum atmosphere, and DLMS uses a laser in an inert atmosphere to perform essentially the same function. In EBM, the material is totally liquefi ed and a melt pool is created; in DMLS the material is sintered without achieving a full melt. ALM presents the opportunity for medical implant manufacturers to create a totally customisable product, including product confi guration, and the depth, density and pattern of the porous layer. Many confi gurations of the porous layer have been observed in practice, and different categorisations of porosity have been identifi ed. Regular patterns can be created using ALM (Figure 1). Irregular and deep patterns have also been documented, where the porous layer is complex in nature and diffi cult to analyse in a 2D field of view. Open porosity allows fluid flow and is traceable to the part surface. Closed porosity does not allow fluid flow and is not traceable to the part surface. Semi closed porosity (Figure 2)
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