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= Direct Imaging Sintering = Direct Imaging Sinthering (DIS) is an additive manufacturing (AM) technique that user an an Infrared power source as well as a DLP as the power and imaging source to sinter powdered material (typically nylon or polyamid e, but poentially also engineering plastics such as PEEK). The method uses a DLP chip, that conterary to SLS where a laser travels over a given path to sinther one layer at a time, the entire layer is projected onto the powder bed in its whole. DLP as a means in additive manufacturing is also used for UV sensitive resins where a UV light source is used instead of an infrared light source.

History
Using DLP for for Additive Manufacturing is a well known methodology for polymerization of UV sensitive resin and is a typical alternative to SLA & LCD use. However, even though the "Near Infrared" DLP WXGA 4500 chipset from Texas Instruments was launched in 2014 its use has been limited if not absent from the market for additive manufacturing until Norwegian company Visitech launched first-of-its-kind DLP NIR light engine for use in 3D printing in 2020.

Technology
As additive manufacturing layering technology, DIS involves the use of a high power Infrared power source to sinter, or fuse fine particles of plastic (which can also be encapsulating metal, ceramic, or glass) powders into a solid mass into the desired 3D shape one - one layer at a time - and is comparable to other powder bed fusion technologies such as SLS. As opposed to SLS where the laser selectively travels over the layer and melts a small point continously, DIS projects the entire layer at once and melts the entire layer simoultaneously. The rest of the process is comparable to other powder bed methods where the given cross section is derived from a 3D model.

In contrast with SLA and FDM, which most often require special support structures to fabricate overhanging designs, DIS, as with SLS, does not need a separate feeder for support material because the part being constructed is surrounded by unsintered powder at all times. This allows for the construction of previously impossible geometries. Also, since the machine's chamber is always filled with powder material the fabrication of multiple parts has a far lower impact on the overall difficulty and price of the design because through a technique known as 'Nesting', where multiple parts can be positioned to fit within the boundaries of the machine. One design aspect which should be observed however is that with DIS it is 'impossible' to fabricate a hollow but fully enclosed element. This is because the unsintered powder within the element could not be drained.

Materials
The quality of printed structures depends on the various factors include powder properties such as particle size and shape, density, roughness, and porosity. Furthermore, the particle distribution and their thermal properties affect a lot on the flowability of the powder.

Commercially-available materials used in SLS should also be abailable to be used with DIS. These come in powder form and include, but are not limited to, polymers such as polyamides (PA), polystyrenes (PS), thermoplastic elastomers (TPE), and polyaryletherketones (PAEK) and other engineering polymers.

Applications
DIS is a new technology and is not industrialized, however, just like SLS will enable to easily make complex geometries with little to no added manufacturing effort. Its most common application is in prototype parts early in the design cycle such as for investment casting patterns, automotive hardware, and wind tunnel models. Arguably as shown by Visitech the VAT sizes used can also be large since the projectors can "scroll" across the VAT which may enable DIS to be used towards large part manufacturing or mass production.

Advantages[edit]
There are some common advangates between DIS & SLS which are:


 * The sintered powder bed is fully self-supporting, allowing for:
 * high overhanging angles (0 to 45 degrees from the horizontal plane)
 * complex geometries embedded deep into parts, such as conformal cooling channels
 * batch production of multiple parts produced in 3D arrays, a process called nesting
 * Parts possess high strength and stiffness
 * Good chemical resistance
 * Various finishing possibilities (e.g., metallization, stove enameling, vibratory grinding, tub coloring, bonding, powder, coating, flocking)
 * Bio compatible according to EN ISO 10993-1 and USP/level VI/121 °C
 * Complex parts with interior components can be built without trapping the material inside and altering the surface from support removal.
 * Fastest additive manufacturing process for printing functional, durable, prototypes or end user parts
 * Wide variety of materials with characteristics of strength, durability, and functionality
 * Due to the reliable mechanical properties, parts can often substitute typical injection molding plastics

There are some advantages that can be identifed using DIS (DLP based) additive manufacturing compared to SLS.


 * DLP printing is typically faster than laser based systems
 * Resolution of the print can be optimized be altering the optics of the system
 * Can allow for moving projectors which can increase build area size/speed

= References =