Selective laser melting
The Selective Laser Melting (English Selective Laser Melting ( SLM) ) is a generative manufacturing process, which belongs to the group of beam melting process. SLM often also referred to as 3D printing.
The selective laser melting of the material to be processed in powder form is applied in a thin layer on a base plate. The powdered material is locally completely melted by laser radiation and forms after solidification a solid material layer. Subsequently, the base plate is lowered by the amount of layer thickness and reapplied powder. This cycle is repeated until all layers are melted. The finished component is cleaned from the excess powder, processed as needed or used immediately.
Typical layer thicknesses for all materials are 20-100 microns.
The data for the guidance of the laser beam can be generated from a 3D CAD body by means of software. In the first computation step, the component is divided into individual layers. In the second calculation step, the paths ( vectors) are generated for each layer, which leaves the laser beam. To avoid contamination of the material with oxygen, the process is carried out under a protective gas atmosphere of argon or nitrogen.
By selective laser melting manufactured components are characterized by large device densities (> 99 %) from. This ensures that the mechanical properties of the component generative produced largely correspond to those of the base material.
Compared with conventional methods ( casting process ), the laser melting is characterized by the fact that tools or molds account for ( informal production) and thus time to market can be reduced. Another advantage is the large geometric freedom that enables component shapes with mold-based method produced no or only with great effort. Further storage costs can be reduced, since specific components need not be stored but can be made if necessary generatively.
Names and naming
The process was instrumental in the Fraunhofer Institute for Laser Technology ( ILT) in Aachen in cooperation with R & S ( Dr. Matthias Fockele and Dr. Dieter Black ) was developed. In the wake of the further process and equipment development of the various machine manufacturers ( ReaLizer GmbH, Concept Laser, EOS, SLM Solutions) were coined different names for the method described principle. For the laser melts the following designations are used:
- Direct Metal Laser Sintering (DMLS )
- LaserCUSING ®
- Selective Laser Melting ( SLM ®)
Specific component design
Typical method is the geometric freedom. This means that undercuts are possible, which can not be produced with mold-based process. In addition, conventionally produced rotary or milled parts can " refined" with SLM ( mixed construction / hybrid design ). Finally, it is possible to let components or prototypes are developed in a very short time or as unique.
- Geometric freedom
The geometry of freedom allows the production of complex structures which can not be technically or economically implemented with conventional production. These include undercuts, as they occur in jewelry or technical components. Also open - porous structures can be produced, whereby lightweight components can be produced while maintaining the strength. As a bionic template from nature can the porous structure of bone call, which has proven to be beneficial in evolution.
- Mixed construction / hybrid design
Under the mixed construction / hybrid design with SLM process refers to a partially generative component manufactured. Here, a second component manufactured generative portion is mounted on a planar surface of a first, conventionally produced in the component region adjacent the SLM process. The advantage of the hybrid design is that it can be greatly reduced by the SLM process to manufacture structural volume of a component, and particularly simple geometries conventional and geometrically challenging areas can be built using the SLM process. Thus, the construction period, and the cost of the metallic powder material is reduced due to the lower volume of the produced by the SLM process component area.
- Prototypes and unique
Formal methods require certain lot sizes in order to determine the cost for the forms on the unit cost. When SLM process these restrictions to be removed: It is possible to produce models or prototypes in a timely manner. In addition, very individual parts are created as unique as they are required for dentures, implants, watches or jewelry items.
Materials
The materials used for selective laser melting are usually series materials that contain no binder. The machine manufacturers and their material partners certify the series materials for the user (eg for dental technical or medical applications acc. European Directives and product liability law ).
Series materials are converted by spraying in powder form. This results in spherical particles. The minimum and maximum diameter of the particles used is chosen in dependence on the layer thickness to be achieved and the quality of the component being used. All powder materials are 100% recyclable for subsequent construction processes again. A booster with unused material is not necessary.
Materials used are for example:
- Stainless steel
- Tool steel
- Aluminum and aluminum alloy
- Titanium and titanium alloys
- Chrome - cobalt -molybdenum alloys
- Bronze alloys
- Precious metal alloys
- Nickel-based alloys
- Copper alloys
- Ceramics
- Plastics (Method: Laser Sintering )
Applications and Industries
The method can be used in numerous industries. These include:
- Aerospace
- Automotive
- Dental Technology ( dentures, implants)
- Medical technology ( Medical devices, endoscopy devices, implants and orthopedics)
- Engineering
- Tooling (eg inserts for conformal temperature )
- Lifestyle products, such as jewelery, fashion, shoes or watches
- Prototypes, such as: Rapid Prototyping
- Bionic designed lightweight components ( eg technical components mimic the bone structure)
- Small series for racing ( auto racing and motorcycle racing )
- Technical components made of metal.