Laser sintering process

Methods are used to produce the more costly rapid prototypes include those that produce models within a few hours. They include photopolymerization, laser tooling, and their modifications. The laser sintering process uses powdered TP rather than chemically reactive liquid photopolymer used in stereolithography. Models are usually made from certain types of plastics. Also used in the different processes are metals (steel, hard alloys, copper-based alloys, and powdered metals). With powder metal molds, they can be used as inserts in a mold ready to produce prototype products. These systems enable having precise control over the process and constructing products with complex geometries. 

Figure 7.32 Selective laser sintering process. A laser is bounced off a mirror, which is controlled by a scanner to selectively trace the outline of a cross section of a part on a powder bed. When one layer has been traced, the part is lowered and fresh powder is rolled into place. After finishing, the part is removed from the loose, unfused powder.

Application Laser sintering processes are used for functional parts. Casting processes are possible, but the direct application is used more frequently (Fig. 12). 

Ziegehneier S, WdUeckea F, Tucka CJ, Goodridgea RD, Haguea RJM. Aging behavior of thermoplastic elastomers in the laser sintering process. J Mater Res 2014 29(17) 1841-51. 

The curved tunnel is a steadily narrowing channel, which can be manufactured using divided inserts or using the laser sintering process. This tunnel is especially subjected to extreme bending stresses. When optimizing, it has to be ensured that no bending stress peak will occur. 

Extensive cooling systems can also be realized with the laser sintering process. These systems are manufactured as a network structure under the surface to be cooled (Figure 2.99). Through this, the cooling medium (e.g., water or CO2) can be transported near the surface (2 mm) to achieve a uniform temperature distribution [9]. 

FIGURE 7.2 Schematic view of the selective laser sintering process [26b]... 

The alternative is to use the laser-sintering process to manufacture form inserts from steel (Section 7.2.6). LDS parts injection-molded with these form inserts can be readied for the LDS process without wet-chemical dipping. On account of the process-related surface roughness of form inserts manufactured by DMLS, there is a slight tendency toward more overmetallization, but this is not generally considered a critical issue. 

Parts produced by the direct metal laser sintering process. 

Fig. 3. Schematics of DMLS(Direct Metal Laser Sintering) process.

Despite the fact that Selective Laser Sintering (SLS) is not an Inkjet 3D printing process, due to its industrial importance, a brief description of this method is included here. 

In the paper, a specific approach to investigation of sintering kinetics was proposed. The experiments on laser sintering were carried out with the use of a number of testing samples. The duration of laser processing, t, was varied for different samples. This allowed to elucidate important features of structural evolution at different stages of the sintering process. 

The membrane nanoporous layers are proposed to be formed by laser sintering of nanopowders deposited onto the surface of microporous structure by sol-gel sedimentation/centrifugation technique. In principle, the method of laser sintering is well known [1], However, there is no wide application in practice of nanopowder processing up to date. A number of constraints defines what quality of sintered stmcture may or may not be achieved by this technique. On the whole, the comprehension of nanopowder sintering mechanisms by laser radiation is rather low. 

It is supposed that due to the short time of laser sintering undesirable recrystallisation processes are prevented or limited. Besides, optimum conditions for formation of nanoporous layer during laser sintering are provided due to specific ability of nanoparticles to consolidation. As a result, the filter materials possess increased filtration fineness and throughput in comparison with the analogical... 

Kroh M (2008) Development of a modified processing technique for selective laser sintering of high temperature resistant polymers with a Nd YAG-laser. Conference of the polymer... 

Fig. 2 Laser sintering machine, scheme of a sealed build chamber for high-temperature processing (According to Phenix, F)...

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