The main technologies of 3D printing with metals

Metal 3D printing is considered the pinnacle of additive technologies. The first patent for metal 3D printing technology – direct laser sintering or DMLS – was received by the German company EOS GmbH in 1997. Metal 3D printing has continued to evolve since then, and today we’ll take a look at the most common methods. .

The additive manufacturing of metal products can be divided into four main areas: synthesis from metal powders on a substrate (MPBF), inkjet deposition of a binder on metal powders (Metal Binder Jetting), direct energy and material injection (DED) and 3D printing by extrusion, a well-known enthusiasts (FDM/FFF).

Synthesis on a substrate using metal powders (Metal Powder Bed Fusion, MPBF)

Processes in this category include direct metal laser sintering (DMLS), selective laser melting (SLM), and electron beam melting (EBM).

Direct Metal Laser Sintering (DMLS)

This method can be used to create objects from almost any metal alloy. In direct laser sintering, the sacrificial powder is applied in a thin layer, then the laser sequentially processes the layer, sintering the particles without completely melting. The process is repeated over and over again until a complete product is obtained. At the end of 3D printing, the product is slowly cooled, and the remaining powder is removed from the working chamber to be cleaned and prepared for reuse. The main advantage of direct laser sintering of metals is that it makes it possible to obtain products without internal stresses and hidden defects, which is especially important in the production of cast parts, for example, for the aerospace or automotive industries. The main disadvantage of this method is its high cost.

Selective laser melting (SLM)

As in the previous method, fine metal powders are used here. The principle of growth is similar, but instead of sintering, the powder particles are completely melted, forming a very dense mass. Currently, this process is only applicable to certain metals and alloys, such as stainless and tool steels, titanium, cobalt-chromium and aluminum alloys. High processing temperatures can lead to residual stresses and distortion of printed objects.

Electron beam melting (EBM)

This method is similar to selective laser melting, but electron guns are used instead of laser emitters. The range of compatible consumables is limited: titanium alloys are most commonly used, although the method can work with cobalt-chromium and some other options. The technology is mainly used in the additive manufacturing of parts for the aerospace industry.

The main advantages of the above methods are the ability to build parts of almost any geometric shape and, in general, the use of a wide range of materials – from lightweight aluminum to high-temperature nickel superalloys, many of which are difficult to produce using traditional methods. . In terms of mechanical properties, the resulting products may be somewhat inferior to cast and forged counterparts, but in the manufacture of complex-shaped parts, this is compensated by the possibility of manufacturing durable products without welded joints.

The disadvantages include the high cost of consumables, equipment and operation. In addition, parallel growth of metal support structures is required to cope with deformations, which leads to more waste and requires significant post-processing work. Useful volumes of such systems are structurally limited, and work with fine powders requires strict adherence to safety regulations.

3D printing with metal powders with inkjet application of a binder (Metal Binder Jetting)

The technology provides for the selective application of a binder on layers of powder – sand, ceramics or metal – before obtaining a part. Since the process takes place at room temperature, the possibility of thermal deformation is eliminated, and the equipment itself can be adapted for large-scale production. Supports are not needed, since the powder itself serves as a support for the laid out blanks. After construction is completed, unused materials can be sieved and reused. Such systems are popular in small-scale production and the manufacture of individual parts according to individual requirements.

metal powder 3d printing

The advantages are greater geometric freedom, efficient use of working volume with the possibility of small-scale production and the absence of the need for support structures, which facilitates post-processing. The absence of deformations at the construction stage allows the development of large-sized products. The technology is characterized by higher productivity and lower cost than the synthesis processes on a substrate.

The main disadvantage is the need for heat treatment. Preforms for 3D printing must be annealed and sintered, which requires additional financial and time costs. The density of the resulting products, as a rule, is lower than that of analogues obtained synthetically on a substrate, which can lead to a deterioration in mechanical properties. The choice of suitable metal consumables is relatively limited.

Direct supply of energy and materials (Directed Energy Deposition, DED)

This includes multiple processes using different energy sources as well as powders or wires. The two most common methods are additive fabrication of frameworks (WAAM) and laser metal deposition (LMD), also known as direct laser growth.

Direct supply of energy and materials (directed energy release, Ded)

At the heart of all DED 3D printing technologies is the supply of consumable material directly into the melting zone. The consumable material is either powdered powder or wire. The material is applied to the surface of the product to be grown and immediately melted using an electric arc, laser or electron gun. WAAM is a combination of wire and arc welding, while LMD uses powders and lasers.

DED technologies are suitable not only for 3D printing products from scratch, but also for the repair of metal parts such as turbine or compressor blades, as well as for applying metal coatings.

One of the advantages of DED 3D printing is the low cost of materials when using wire. DED 3D printers can also use two or more metals or alloys at the same time, creating structures with degraded composition. Multi-axis positioning (5 or 6 axes) adds the ability to build geometrically complex parts without the use of support structures.

Finally, DED 3D printers scale well, produce high-density parts, are economical in terms of material consumption, and can be very productive, especially when using wire.

Among the disadvantages are the relatively high cost of equipment, low resolution, which reduces detail, as well as the poor quality of surfaces when working with wire, which requires intensive post-processing.

3D printing by extrusion (FDM/FFF)

The well-known and available technology of 3D printing by layer-by-layer deposition of a polymer rod (FDM or FFF) can also be used for the production of metal products. This requires special threads, but the right equipment is available even for small businesses. This is the whole point of making metal 3D printing as accessible as possible.

3D Printing Extrusion Fdm Fff

Consumables – polymer-metal threads, that is, plastic composites with a metal filler. Such composites can be printed on most FDM 3D printers, even the most amateur ones, but the resulting blanks require serious processing. After 3D printing, the polymer binder must be removed by etching or annealing, after which the part must be sintered to the finished shape. Thus, the main part of the costs falls on heat treatment equipment and rather expensive consumables, but in general, the process remains the cheapest of all listed.

3D printing by extrusion with polymer-metal filaments is used both in piece and small-scale production, does not require the use of expensive and dangerous fine powders, and is available for small and medium-sized businesses.

The main disadvantage is the tedious heat treatment of 3D printed blanks, which requires additional equipment. Parts with complex geometries often need to be printed with supports, but the support structures are relatively easy to remove prior to heat treatment, just like conventional plastic models. The resulting products have a relatively high porosity and are subject to significant shrinkage during heat treatment, which must be compensated for by chipping when preparing 3D models for printing.

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