Direct Metal Laser Sintering & Electron Beam Melting (3D Printers)

1. Direct Metal Laser Sintering 

Direct Metal Laser Sintering (DMLS) works on the principle of Powder Bed Fusion. DMLS technique is used vastly in the field of Additive manufacturing. In this system, the metal component is printed with the help of the sintering of metal particles at a high temperature obtained by the laser beam. 

This printing technology works on the layer-by-layer fusion of metal particles which are processed and sliced down by the CAD software. The component can also be printed by scanning a similar component and feeding it in the printer by digital processing. 

 

Figure 1. Schematic of Direct Metal Laser Sintering [Source: www.custompartnet.com] 

As demonstrated in Figure 1, the laser beam is deflected onto the position where the powdered metal particles are to be fused. This position is also called the Sintering zone. The laser beam sinters the metal particles layer-by-layer on the powder bed or printing bed. The bed platform raises gradually when the next layer is sintered and subsequently, the re-coater arm pushes the metal powder from its supply table to the sintering zone after the sintering of the previous layer. This technique uses energy to maintain high temperatures in the sintering zone but the particles are not melted and less energy is used compared to SLM printing. 

 

DMLS has a high level of accuracy as laser beams are used precisely at the fusion points of powdered metal particles with the guidance of CAD software. This printing process can be used to fabricate objects from a variety of metals such as steels, stainless steel, aluminum, titanium, nickel alloys, cobalt, and Chromium. The fabricating dimensional tolerance is ±0.1 mm for new generation DMLS printing systems. 

 

2. Electron Beam Melting 

Electron Beam Melting (EBM) printers are developed and manufactured by ARCAM Corporation and this method of printing works on the fundamental principle of the Powder bed fusion method. As the name suggests, the EBM technique uses an electron beam to fuse the metal powdered particles and form the desired component with a layer-by-layer fusion method approach. This electron beam is produced by an electron gun and it extracts the electrons from the metal filament under vacuum. These metal particles are further deposited layer-by-layer in the sliced design processed by the CAD software. The deposition of metal particles by the electron beam is performed on the building plate of the 3D printer. EBM printers are known to have a good production speed but they can be a less precise method for 3D printing than laser techniques.  

 

Figure 2. Schematic of Electron Beam Melting mechanism [Source: arcam.com, ge.com] 

In this particular design of EBM printers by ARCAM illustrated in Figure 2, the electrons are heated at a predefined temperature and then are incident in the form of an electron beam from the filament. These electrons can be accelerated up to half the speed of light and are deflected by two magnets at the desired points on the building platform. Once the powdered metal particles get deposited, the build platform is lowered and the next layer of metal particles is fused with the guidance from the CAD software.  

EBM rapid prototyping makes possible the creation of complex metal components out of a CAD model by melting powder particles. This process is ideal for the fabrication of high melting temperature alloys, such as Titanium, Nickel, and Cobalt-based alloy components. This printing method can precisely create thin wall structures of the thickness of 0.05 mm. 

Powders available by ARCAM on its webpage are: 

Ti–6Al–4V 

Ti–6AL–4V ELI 

Titanium Grade 2 

Co–Cr–Mo ASTM F75 

Basic Comparison

The Direct Metal Laser Sintering process (DMLS) also uses laser beams for the polymerization of metal powder. But this process does not melt the particles completely. The metal particles are heated and fused which can be a faster and less energy-consuming process than other powder fusion techniques which use more energy to melt the particles for fusion. Moreover, DMLS is more accurate than EBM as the laser beam radius in DMLS is quite lower than that of the electron beam in EBM.

Typical SMLS and EBM printers available commercially are shown below:

Fig 3. EOS M 290 DMLS printer [Source:3dlogics.com]

Fig 4. ARCAM EBM Spectra H [Source: ge.com]