3D PRINTING TECHNOLOGIES

 

SLM (Selective Laser Melting)

Sources:

http://3dprintingfromscratch.com/common/types-of-3d-printers-or-3d-printing-technologies-overview/

 

Selective laser melting (SLM) is a technique that also uses 3D CAD data as a source and forms 3D object by means of a high-power laser beam that fuses and melts metallic powders together. In many sources SLM is considered to be a subcategory of selective laser sintering (SLS). But this is not so true as SLM process fully melts the metal material into solid 3D-dimentional part unlike selective laser sintering. The history of SLM started with German research project held by group of Fraunhofer Institute ILT in 1995.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The fine metal powder is evenly distributed onto a plate, then each slice of 2D layer image is intensively fused by applying high laser energy that is directed to the powdered plate. The energy of laser is so intense that metal powder melts fully and forms a solid object. After the layer is completed the process starts over again for the next layer. Metals that can be used for SLM include stainless steel, titanium, cobalt chrome and aluminum.

 

This method of printing is widely applied to parts with complex geometries and structures with thin walls and hidden voids or channels. Lots of pioneering SLM projects were dedicated to aerospace application for different lightweight parts. SLM is great for project that experience such kind of problems like tooling and physical access difficulties to surfaces for machining, as well as restrict the design of components. The technology is not widely spread among at-home users but mostly among manufactures of aerospace and medical orthopedics. But the whole process of acceptance, certification and final approval takes some time which results in long time for development and qualification for this technology.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Polyjet and Multijet 

Sources:

http://www.sculpteo.com/en/3d-printing-technologies

 

Polyjet and Multijet is similar to SLA and uses a UV light to crosslink a photopolymer. The difference is, instead of scanning a laser to cure layers, a printer head jets tiny droplets of the photopolymer (similar to ink in an inkjet printer) in the shape of the first layer. The UV lamp attached to the printer head crosslinks the polymer and locks the shape of the layer in place. The build platform then steps down one layer thickness and more material is deposited directly on the previous layer. This is process is repeated until the part has completed printing.

 

PolyJet 3D printers, such as the Stratasys Objet 3D printers, are capable of highly complex and high resolution parts with fine features, but lack the strength of SLS and FDM parts. Combining two or three materials in specific concentrations and microstructures, this technology allows to produce a range of materials with varying translucency, rigidity, thermal resistance or color. Using this process, a single part can contain materials with diverse physical and mechanical properties ranging from rubber-like flexibility to ABS-like rigidity. Similar to SLA, the photopolymer is vulnerable to sunlight and heat, and the material can creep over time.

 

Poly-jet printing is a great process for developing fully assembled prototypes and complex and detailed geometries with multiple material properties.

 

DLP (Digital Light Processing)

Sources:

http://www.sculpteo.com/en/3d-printing-technologies

 

Digital Light Processing is a 3d printing process where a projector is used to cure photopolymer resin. Very similar to SLA where the only difference is that instead of a UV laser to cure the photopolymer resin, a safelight (light bulb) is used. Objects are created the same as SLA with the object being either pulled out of the resin which creates space for the uncured resin at the bottom of the container and to form the next layer of the object or down into the tank with the next layer being cured on the top.

 

Objects that are printed with Digital Light Processing have less visible layers versus other processes such as FDM/FFF. Compared with SLA, DLP can have faster build speeds due to a single layer being created in one singular digital image whereas with SLA, the UV laser has to scan the vat with a single point (trace out the object layer).

 

Also, the same photopolymer resins that can be used with SLA, can be used for DLP 3D Printing. Objects printed with this process have the same strengths and weaknesses.

 

Similar to SLA, DLP is commonly used to generate highly detailed artwork, non-functional prototypes, and can be used to make molds in investment casting applications.