Selective laser sintering (SLS)

Realising functional plastic components directly from 3D data.

Selective laser sintering, abbreviated SLS, is the most frequently used additive layer construction process in the industrial sector.

The starting materials are various plastics in powder form. Depending on the area of application of the manufactured component, it is chosen between materials with different properties. With the help of one or more lasers, functional three-dimensional objects are printed from these powders.

The laser beam precisely fuses the individual powder particles. The building platform is then lowered by one layer thickness and filled with powder again. This process is repeated until the complete object is printed. Due to the printing in the powder bed method, no supporting elements have to be produced even when geometries are complicated.

If desired, the components can be further finished, e.g. by smoothing, blasting, colour infiltration, painting or coating.

Our service portfolio

FKM Sintertechnik offers a wide range of services for additive manufacturing methods. Part of rapid prototyping, which plays a major role especially in the development of new components, is the laser sintering process. In addition, we also offer laser melting (SLM: selective laser melting) for metallic components and carry out various surface refinements. 3D control scans are also part of our service portfolio. On site in our production units and test centres, we carry out all work steps from the CAD creation of the project to the sintering and inspection of the finished workpiece. We work with the most modern laser sintering machines. We continuously invest in further production equipment and optimise our work processes so that we always deliver the best results to our customers.

What is laser sintering?

Laser sintering is a process within additive manufacturing and rapid prototyping procedures. Here, components are made from various plastics in a very short time. One of the advantages is that new moulds, components, and tools can be produced during the developmental process. This way, sources of error can already be identified from the first printed object on and the workpieces can be directly checked for their fit and, if necessary, adapted accordingly. Optimised precision tools and workpieces are produced in a resource-saving, time- and cost-efficient manner with the help of adaptable CAD data. Another advantage of selective laser sintering is that there is an almost unlimited freedom of design. Ideas, however complex and filigree in their geometry, can be realised. Even internal movable parts or cavities such as cooling channels can be realised without seams thanks to SLS. In particular, the considerably reduced time required is a major advantage of laser sintering, but so is the production cost factor. Costs are calculated here according to the built volume. Filigree shapes with cavities are thus more cost-effective with SLS than more compact components and thus stands in contrast to conventional manufacturing methods, where costs often rise with complexity. Another advantage of SLS is that leftover, i.e. non-sintered, powder from a production process can be used for the next project. This minimises the material waste and thus the material costs incurred.

Laser sintering: The process

In the laser sintering process, the selected plastic powder is very thinly applied to a movable building platform. The powder is then precisely fused by a laser beam and as required along the structures previously defined by the CAD programme. The platform is lowered, and a new layer of powder is applied. This way, the entire object is created layer by layer. The powder that is not fused also serves as a stabiliser for the emerging object. The powder that is not fused can then be used for other projects. This reduces the waste of materials enormously, which is also reflected in lower production costs. In contrast to the prototyping process of selective laser melting, laser sintering does not use metals, but only polyamides, polymers and elastomers. FKM Sintertechnik has a permanent selection of ten plastics, which are presented in the following chapter.

Permanently available plastic powders for the SLS procedure

FKM Sintertechnik permanently has ten different plastics for the SLS process in stock – depending on the intended use of the finished component and the associated necessary material properties such as strength, chemical resistance, flexibility, good thermal conductivity, protection against flames and others.

• PA 12 natural/white/grey: This high-strength plastic is resistant to chemicals, has a long-term stability, high accuracy in details and can be post-treated in a variety of ways. Thanks to its biocompatibility, the material is a good choice in the medical technology field of prosthetics.
• PA 11: This whitish powder is made from renewable resources and features extreme flexibility as well as excellent resistance to chemicals.
• PA 12 with glass: This glass bead filled polyamide 12 powder is very stiff with good elongation at fracture and has a high thermal load capacity.
• PA 12 with flame retardant: Polyamide 12 is additionally provided with a chemical flame retardant and is typically suitable in aviation and electrical engineering.
• PA 6: The material is dimensionally stable up to 120 °C, fatigue-resistant and chemically resistant to petrol, oil and grease and is therefore particularly applicable in automotive production.
• PA 12 with aluminium: This Polyamide 12 powder is aluminium filled, so the component has a metallic appearance.
• TPU: This urethane-based thermoplastic elastomer is highly mechanically resilient, elastic, and abrasion-resistant.
• PEEK: Peek is a high-performance polymer that can withstand high temperatures of up to 260 °C and is therefore predestined for use in medicine as well as in aerospace and motor sports.

Selective laser sintering Fields of application

The SLS process is primarily used for professional rapid prototyping. However, selective laser sintering is also playing an increasing role in the production of small series and spare parts. Industries that work with SLS-manufactured components include medicine, the automotive industry, mechanical engineering and aerospace. Especially in medicine, the advantages of SLS are visible, because patient-specific implants or prostheses can be manufactured. But also in the other industries mentioned, SLS has, for example, the decisive advantage of being able to produce complex and lightweight components for specific projects.

Background and history of SLS

Selective laser sintering was developed as early as the 1980s by student Carl R. Deckard at the University of Texas. After a few years of development, Deckard, together with Dr. Joe Beaman, who supported him in his work, applied for a patent in 1986. However, laser sintering did not become marketable until the mid-1990s. Since then, this process has been constantly optimised, made more efficient and, above all, more precise. Gradually, the SLS process is also finding its way into non-industrial areas such as model making or medical technology, where individualised workpieces and patient-specific parts are needed.