3D printing has been in professional use in industry for many years and enables a wide variety of products. Since the first commercially available 3D printer in 1988, which was based on the laser sintering process, a lot has changed to today’s methods and processes. The generic term for all this is the so-called “additive processes”, in which components are built up layer by layer.

Deutsche Bahn and all its suppliers also produce spare parts from metal and plastic using 3D printing. This can drastically shorten delivery times in particular. “In this way, we can ensure a better supply of spare parts and make the vehicles available to our passengers again more quickly. In particular, we are talking about parts that are associated with long delivery times or would no longer be available at all,” says Stefanie Brickwede (Project Manager 3D Printing DB).

Modern manufacturing processes include:

Printing process

3D printing (3DP). The material, which is in powder form, is given shape with an additional liquid binder and by means of a print head in what is known as the powder-binding process, similar to selective laser sintering. Excess powder is then extracted and can also be used to produce other components.

The desired 3D model is thus created through several hundred or even thousand layers. Both the powder and the binder can be dyed beforehand, giving the model the desired color.

Technique: Application of liquid binder on a powder bed
Material: Plastic, ceramic, metal, plaster, cellulose

Layer Laminated Manufacturing (LLM). Paper, metal or plastic foils are laminated together in layers and cut into shape using cutting tools (knife, hot wire, laser).

In the case of plastic films, these are bonded or polymerized; in the case of metal films, they are laser, diffusion or ultrasonic welded.

This process is particularly well suited for the cost-effective generation of solid components and large models, as they work quickly in relation to the component volume and are not very complex in terms of machine technology.

Technique: Bonding of foils in different layers
Material: Plastic films, paper, metal foils 

Selective laser sintering (SLS) and laser melting (SLM). In selective laser melting, a powder-like material is applied in a thin layer to a base plate and completely remelted by a laser beam.

In the case of selective laser sintering, on the other hand, the material is not completely melted, but only melted on, whereby sinter necks connect the individual layers with each other.

Technique: Local melting of powdery materials by a laser
Material: Plastic, metal, sand, ceramics

Fused Deposition Modeling (FDM). The material, which is in solid form, is melted in a heated nozzle and then applied layer by layer to a building platform. This is a so-called extrusion process in which the material is melted from the solid phase and processed.

The material is usually acrylonitrile butadiene styrene (ABS), a plastic that is particularly suitable for heavy-duty applications.

Technique: Layer-by-layer application of molten material.
Material: ABS, wax, PLA, PC, PPSF 

Stereolithography is the oldest additive process in which the workpiece is placed in a liquid bath of photopolymer into which it is gradually lowered. A laser passes over the starting material, liquid photopolymer, at each step to create the desired shape by curing.

After the part is fabricated, it is removed from the liquid bath and allowed to drip. The platform and all support structures are then removed from the component and the finished part is post-processed.

This makes it possible to produce filigree structures and smooth surfaces and is thus considered an extremely precise process.

Technique: Layer-by-layer curing of liquid polymers by means of a UV laser
Material: Acrylic and epoxy resins

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