Additive Manufacturing Technologies: An Overview about 3D Printing Methods and Future Prospects

Table 4

Selective sintering/melting (SS).

Selective Laser Sintering
	A layer of powder is laid down and a CO2 laser sinters it at the points selected on a 2D cross section of the model (XY plane). The platform gradually descends (Z plane) in accordance with the height of the layer defined [12].
	Precision is between +/- 0.3% (min. +/- 0.3 mm).; The minimum layer thickness is 0.08 mm. Maximum model size 700x380x580 mm.
	The following materials can be used: Polyamide (PA), Glass filled polyamide (PA-GF), Alumide, PA 2241 FR, TPU 92A-1.; Properties of the PA material: tensile modulus: 1650 Mpa; tensile strength: 22 Mpa; elongation at rupture: 20%; flexural modulus: 1500 Mpa; bending strength: - Mpa; impact strength: 53 J/m; deformation under load temperature: 86°C.
	Advantages and disadvantages; Pieces of high quality and precision are obtained. A large quantity of sintering materials is available. They do not present problems to obtain pieces with cantilevers or internal holes because the own dust makes of support.; The equipment and materials are medium-high cost.
Selective Laser Melting
	The print nozzle head is fitted with a CO2 laser that is directed via a set of lenses onto the powdered material.; The support structures are made of the same material as the model and must undergo a subsequent finishing or even machining process [3].
	The minimum layer thickness is 0.020 mm.
	The material can be: stainless steel, Co-Cr, Inconel 625-718, titanium Ti64.; Properties of the material Co-Cr: ultimate creep (): 1050 Mpa; elongation (E): 14%; Young’s modulus: 20 Gpa; Hardness 360 HV.
	Advantages and disadvantages; Pieces of high quality and precision are obtained. There is a large amount of metallic materials to be sintered.; Equipment and materials are expensive. They have problems to obtain pieces with cantilevers or internal holes due to the relative difficulty of removing the supports.