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3D PRINTING PROCESS

Selective laser sintering (SLS)



Selective laser sintering is ideally suited for the production of functional prototypes, high-quality functional parts and small batches made of plastic.

What is laser sintering used for?

Prototypes

Laser sintering is ideal for rapid prototyping. It is very often used to check the fit of injection molded parts before the tool is manufactured.

  • Installation sample
  • Functional prototypes
  • Illustrative models

Functional parts

The well-balanced mechanical properties of our materials allow us to produce durable and robust parts for many applications. The white SLS parts are ideal for subsequent finishing.

  • Manufacturing aids, gauges, etc.
  • Technical special parts
  • Orthotics and prostheses

Small batches

SLS is perfect for small parts that are required in low to medium quantities (1 - 10,000 pieces). The use of industrial 3D printers guarantees high throughput with short delivery times.

  • Attachments in mechanical engineering
  • Covers and housings
  • Consumer goods

Selective laser sintering materials



A wide variety of polyamides (e.g. PA 12) and elastomers are available to you. These plastics cover a wide range of requirements such as strength, flexibility or chemical resistance.

PA12

PA12 is a technical thermoplastic that is most commonly used in SLS 3D printers. It offers the best price-performance (properties) ratio.

TPU

With this thermoplastic elastomer with a Shore hardness of 90A, flexible parts can be manufactured that have a good feel and high wear resistance.

3D printing finish for SLS parts



The selective laser sintering can produce any three-dimensional parts in a very good quality. Numerous finishing methods can be used for these parts. The following overview shows numerous options that are available to our customers.

Most of the time, our classic finish is used. A black color with subsequent compression blasting. The result is a smooth surface that is suitable for salable products.

Untreated SLS 3D printed part in white

Depending on the material, the parts usually come in a white color from the 3D printer. The surface is slightly rough. Due to this nature, untreated parts easily absorb dirt and, in contact with the skin, also sebum. Without finish, we recommend untreated parts especially for prototypes and functional parts that are not exposed to excessive skin contact.

SLS parts can be excellently dyed in different colors.
SLS parts can be easily colored in the color of your choice. For this purpose, harmless textile dye is used, which penetrates the surface of the parts during the dyeing process. The dyeing process is very simple:
The necessary color pigments are dissolved in a heated water bath and then the white SLS parts are added. After a certain time, the parts have absorbed the paint and can be removed again. A short drying phase follows and the parts are ready for the next finishing step or for use.
Black laser sintered part incl. ceramic blasting
The surface of the finished printed parts is compressed again by the so-called compaction blasting. This gives the surface a slightly velvety and smooth structure, which, in contrast to untreated surfaces, is less scratch-sensitive and rough.
The surface of a laser sintered part can be smoothed by slide grinding
In vibratory grinding – also known as barrel finishing – the finished parts are placed in a vibrating trough together with differently shaped grinding stones after de-powdering. The vibrations generated in it cause stones and parts to move through. This produces uniform abrasion on the part, resulting in a homogeneous, smooth surface. However, this finishing process is not recommended for parts that require sharp edges, as these are broken and slightly rounded off in the process.
Laser sintering allows parts to be painted afterwards
SLS parts can also be colored by painting. After thorough removal of any visible construction stages and subsequent priming, painting with two to three top coats can be implemented. High-quality visible surfaces on functional components are therefore no problem.
Infiltrated with Dichtol, laser sintered parts are made pressure-tight
When infiltrated with Dichtol, SLS parts can be made pressure-tight. The part is immersed in a bath filled with sealing oil. The impregnation penetrates the open pores of the part and closes them reliably.
SLS parts can be smoothed by chemical smoothing
By means of so-called chemical smoothing, surfaces on 3D printed parts can be refined to approximate the surfaces of injection molded parts. For this purpose, the part is hung in a closed apparatus in which the solvent is evaporated. This fine solvent vapor attacks the rough surface structure of the part, which smooths it and creates a uniform surface finish.

Advantages and disadvantages of the SLS 3D printing process



Selective laser sintering cannot do everything, but it can do a great deal. It is not for nothing that it is the most widely used 3D printing process. Nevertheless, it always depends on the individual application. You are welcome to contact us directly about this.

Advantages of the SLS process

Disadvantages of the SLS procedure

Contact us - we are open for new projects!

How laser sintering works



The technology is already over 40 years old.

Dr. Joe Beaman and Dr. Carl Deckard of the University of Texas developed the basic principles of laser sintering back in the 1980s. In addition to the SLS 3D printing process, additive manufacturing offers two other very similar technologies. However, these are much younger. We see the HP Multi Jet Fusion process as the most important alternative. You can read about the exact differences to laser sintering here .

How does the process work?

The SLS technology works with a fine plastic powder that serves as the starting material. This plastic powder is mostly nylon. It is applied at the beginning of the printing process with a squeegee in a thin layer (80-150 µm) on the construction platform. This platform can be lowered in small steps in a so-called building cylinder.

Data preparation

The 3D data for printing must also be broken down into thin layers at the beginning. This digital preparation is carried out by so-called slicing software. Then the prepared data is loaded onto the SLS machine and printing can begin.

Printing process

As the name suggests, laser sintering uses a laser beam to fuse the fine powder. The powder layers prepared by the squeegee are now exposed with the prepared data. Each thin data layer is projected onto the respective powder layer by the laser. In the video shown above, the process described can be seen very clearly. As soon as a layer is completed, the building platform in the cylinder is lowered by the respective layer thickness.

Cooling down

The build space of an SLS 3D printer is heated during the entire printing process. This thermal energy has to escape again after printing. The construction job first cools down in the system itself to a moderate temperature for a few hours. The installation space is then removed from the system and has to cool down further at room temperature. This process must be carried out as gently (slowly) as possible, otherwise the SLS components can become warped.

Unzip

After the cooling phase, the sintered components can be removed from the construction job. Most of the loose, unprinted powder can be easily removed by hand or with a brush. A thin layer, however, easily bakes onto the SLS parts, which can then be finally removed by glass shot peening.