The ColdMetalFusion (CMF) process is known for reliable serial production in metal AM with high part quality. In CMF, Headmade Materials combines standard PM metal powders with its proprietary binder system to form a powdery feedstock that can be processed into green parts on standard plastic laser sintering systems. The subsequent debinding and sintering step is again PM industry standard, and the part characteristics are fully comparable to MIM in terms of density and strength.

But CMF can also be used to produce porous parts with up to 50 vol% porosity. Even gradient porosity and parts with dense and porous sections are possible. The influence of feedstock, laser sintering parameters and sintering parameters on porosity and the potential in filter applications and medical industry will be shown in this study.

By developing new feedstock materials and new CMF processing parameters, CMF can also be used to produce components with a defined and gradual porosity for applications in the fields of filtration, medical technology, and hydrogen generation. The focus here is not on the mechanical properties, but on the porosity characteristics in terms of pore size, pore shape, homogeneity, flow resistance and surface.

With CMF the porosity can be adjusted in three ways: feedstock, laser sintering and sintering. Especially the laser sintering offers a new and unique dimension to adjust the porosity compared to MIM and competing 3D printing technologies, because the porosity in the green part can already be adjusted and gradual porosity gradients can be implemented within one part using various exposure strategies. This offers many possibilities for potential new applications.

Creating porous structures with CMF standard feedstock

In the following, the possibility of producing porous structures with CMF standard feedstock is examined. The two main influencing factors that determine the degree of porosity are ...

One possibility to produce more porous structures is the use of ... within the feedstock material, as these particles tend so have a lower sintering activity [4], especially at lower sintering temperatures. Figure impressively illustrates this effect by comparing the green and sintered density as well as the scaling factor of CMF standard feedstock (fine metal powder) and optimized CMF feedstock (coarse metal powder).

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Applications

Figure 3 shows exemplary Ti6Al4V parts like a technical filter with highly porous filter areas which are embedded within a honeycomb-shaped support frame, as well as the acetabulum-component of a hip joint implant which is printed with a porous outer shell and a dense inner surface...