In selective laser sintering (SLS resp. PBF-LB/P), as in all laser powder bed fusion technologies, plastic powder is deposited over the entire surface of a build platform. A CO2 laser heats the plastic particles at predefined coordinates almost to their melting point, causing them to bond together. Once a layer has been produced, the build platform is lowered, a new layer of powder is applied and the component is thus produced in three dimensions. Unlike stereolithography (SLA) or the PolyJet technology, complex geometries with undercuts or overhangs can be built without support structures, because the components are supported by the surrounding material in the compact powder bed due to the high heat in the build space. This means that, for example, interlocking moving parts can also be manufactured in one piece.
Top technology for plastic parts
Selective laser sintering is used to produce components that have a high temperature resistance and whose good mechanical properties do not age over their lifetime, either. The components have a relatively rough (Ra ~13 μm), grainy surface that can be very easily post-processed. Due to a minimum wall thickness of 0.7 mm, thin-walled and complex geometries are possible. SLS is ideal for e.g.:
In stereolithography (SLA), the first and longest-used 3D printing process, a duroplastic synthetic or epoxy resin (photopolymer) is cured by an ultraviolet laser beam guided along the component contours via movable mirrors. Once the layer is completely cured, the build space is lowered, a new layer is applied and the entire component is thus built up in three dimensions. Support structures are required to fix the components in the liquid build space, and these are removed manually afterwards. Depending on the material, a curing process is then carried out using UV treatment to completely solidify the outer surface of the components. Since the material is constantly sensitive to light, discoloration of the components occurs over time, which is why post-treatment of the surfaces may become necessary.
Filigree structures and top surface quality
Stereolithography is used to produce highly isotropic, waterproof and temperature-resistant components with a very high detail resolution, accuracy and very smooth surfaces (Ra ~2 μm). Due to a minimum wall thickness of 0.7 mm, thin-walled and complex geometries are possible. SLA is ideal for e.g.:
Digital Light Processing (DLP) uses a liquid photopolymer that is cured by UV light projection. Unlike stereolithography (SLA), the light does not penetrate the material from above but from below through the transparent bottom of the build plate (top-bottom process). The component is thus exposed to light layer by layer and pressed upwards out of the build space. In the DLP process, the resolution of the components is defined by the production volume (size of the resin tank) and the resolution quality of the light source (beamer, LCD or LED displays). The smaller the tank and the more pixels, the higher the level of detail of the component. Since the material is exposed over the entire surface, higher build rates are possible with DLP than with SLA. After production, the components are usually thermally post-cured. In addition, geometry-dependent support structures are mechanically removed. DLP is currently used in numerous industries, such as dental technology, the jewelry industry or aerospace.
Perfection in detail - also in series production
With DLP, components can be produced at a build rate of 100 mm/h, featuring an extremely high level of detail, sharp contours and very smooth surfaces. Due to the variety of materials available, impact-resistant duromers, high-stress thermoplastics, tear-resistant elastomers or plastics with a heat resistance of up to 300 °C can be processed precisely and without tools. In this respect, DLP is a real alternative to conventional injection molding, not only from a quality point of view but also for cost reasons, and is ideally suited for the production of:
The new SAF technology uses a bed of polyamide powder, as in selective laser sintering (PBF-LB/P). However, the layer-by-layer bonding of the powder particles is not effected by a laser, but by an infrared-sensitive energy absorption fluid, a so-called High Absorbing Fluid. This binder is applied selectively via piezoelectric industrial print heads, and curing is performed with IR light. Special heat management over the entire powder bed ensures a consistently reproducible part quality even for fine details, flat areas and large, homogeneous and smooth surfaces.
Highest precision for fine plastic parts
SAF is a highly industrial-grade technology that achieves homogeneous polyamide components even with extremely small, fine geometries. The maximum component size is 315 x 208 x 293 mm, and the layer thickness is 100 μm. For series production, SAF promises accuracy, repeatability and process control, which are essential in industrial manufacturing today. The high production capacity results from the fact that printing and fusing take place in one operation, combined with a high assembly density. The technology strives to be competitive with injection molding and allows volumes in the hundreds to thousands of parts. Selective Absorption Fusion is ideal for e.g.:
In binder jetting, also known as Drop on Powder (DOP) technology, a liquid binder is sprayed from a print head, similar to an inkjet printer, along the component contours onto a thin layer of plastic powder and causes the individual plastic particles to stick together. The build area is then lowered, a new layer of powder is applied and the entire component is built up three-dimensionally in several layers. As in selective laser sintering (SLS or PBF-LB/P), no support structures are needed in binder jetting because the components are stabilized by the material surrounding them. Unlike selective laser sintering (SLS), the build space is not heated, which on the one hand prevents thermal distortion of the components, but on the other hand requires a subsequent heat treatment to achieve the final stability of the components.
Large prototypes and molds
Binder jetting allows relatively large components to be produced quickly and inexpensively with high precision and good detail resolution. The components have a relatively rough (Ra ~13 μm), grainy surface that can be post-processed very well. Due to a minimum wall thickness of 1 mm, thin-walled and complex geometries with low mechanical load capacity are possible. DOP is ideal for e.g.:
In the PolyJet process, also known as Fine Layer Technique (FLT), a liquid photopolymer is sprayed from an inkjet print head along the component contours onto the build platform and immediately cured using UV light. The build platform is then lowered and the next layer of the component is applied. Depending on the geometry of the component, PolyJet requires support structures to attach the component to the build platform and support overhangs. The special feature of this technology is that components can be produced in full color or texture, and several materials with different properties (e.g. solid and flexible) can be applied simultaneously in a single pass. Thus, components with very different properties and effects can be produced.
Realistic prototypes in full color
PolyJet can produce components with a layer thickness of 14 μm or 27 μm and a dimensional accuracy of +/- 0.1 % with very smooth (Ra ~6 μm), pore-free surfaces that can be pst-processed very well by grinding or polishing. Due to a minimum wall thickness of 0.5 mm, thin-walled and complex geometries are possible. PolyJet is ideal for e.g.:
FDM may not be the first but the best-known 3D printing technology. It was developed in the late 1980s and has evolved to be a very mature and stable technology. The technology is similar to that of a hot glue gun. A wire-shaped, thermoplastic filament is heated to the melting point in an extruder and deposited in liquid form onto a build platform along the contours of the component. In the process, the material hardens quickly by cooling, so that the next layer can be applied and the component can thus be built up layer by layer with a layer thickness of 0.15 mm to 0.3 mm (depending on the material selected). For cost and time reasons, solids are not produced solid but with filler structures. Depending on the part geometry, support structures are required, which have to be removed afterwards. Today, FDM is already used as an industrial technology in many industries for series production.
Robust components for high-performance applications
With FDM, dimensionally stable components with high stiffness can be produced cost-effectively over the long term. Unmachined components have a rough surface and reveal the individual construction stages, but many types of post-processing are possible, such as smoothing, painting or coating. FDM allows a minimum wall thickness of 1 mm and has a lower accuracy compared to other 3D printing technologies. In return, however, a very wide range of processable materials up to composite materials and high-performance plastics is available for demanding applications. FDM is ideal for the production of e.g.:
In Gel Dispensing Printing (GDP), a highly viscous gel (white photopolymer acrylate) is applied layer by layer from an extruder under computer control and immediately cured using UV light. The build area is then lowered and the next layer of the component is applied. With GDP, almost all geometries can be built as hollow bodies and without support structures, which has a positive effect on manufacturing costs and times. GDP is impressive with its fast build rates (2 kg of material per hour), the components are excellently suited for subsequent post-processing and spectacular optical effects.
Parts with impressive appearance
Gel Dispensing Printing is used to produce components up to a size of 1.80 m in one piece. The objects are light- and flame-retardant according to DIN 4102 - class B2 / ASTM D635 / UL 94 HB. The relatively rough, ridged surface can be easily finished and refined, e.g. by coating with polyester, epoxy, polyuria/polyurethane, glass fiber spraying, by metal coating, painting or polishing. Dimensionally stable geometries are possible from a minimum wall thickness of 2 mm. GDP is ideal for e.g.:
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