Types Of 3D Printing

3D printing is becoming the future of the manufacturing era. Also known as additive manufacturing, it’s an umbrella term encompassing several manufacturing technologies that build parts layer-by-layer. In total, seven categories of additive manufacturing processes have been identified and established so far.

Fused Deposition Modeling (FDM)

FDM, also called fused filament fabrication (FFF), is currently the most popular 3D printing technology.

The way FDM usually works is that a spool of filament is loaded into the 3D printer and fed through to a printer nozzle in the extrusion head. The printer nozzle is heated to the desired temperature, whereupon a motor pushes the filament through the heated nozzle, causing it to melt. The printer then moves the extrusion head along with specified coordinates, laying down the molten material onto the build plate, where it cools down and solidifies. Once a layer is complete, the printer proceeds to lay down another layer. This process of printing cross-sections is repeated, building layer-upon-layer until the object is fully formed.

FDM offers a number of advantages. Firstly, FDM is one of the fastest choices in 3D printing, for parts produced with FDM can be ready in a few minutes or couple of hours. Secondly, FDM enjoys great scalability - it can be easily scaled to any size, thus leading to low cost-to-size ratio. FDM printers are continually being made bigger and less expensive, due to low part costs and the simple designs involved. Thirdly, FDM is the only 3D printing technology which uses production-grade thermoplastics, so items printed have excellent mechanical, thermal and chemical attributes.

FDM technology is widely spread today, and used in industries such as automobile manufacturers, food producers, and toy manufacturers.

Stereolithography (SLA)

SLA is the world’s first 3D printing innovation introduced by Chuck Hull in 1986. And even today, SLA is still the most cost-effective 3D printing technology available when parts of very high accuracy or smooth surface finish are needed. Best results are achieved when the designer takes advantage of the benefits and limitations of the manufacturing process.

SLA printing machines do not function like normal desktop printers that extrude some quantity of ink to the surface. SLA 3D printers operate with an excess of liquid plastic that after a while hardens and forms to a solid object. After the plastic hardens a stage of the printer drops down in the tank a fraction of a millimeter and laser forms another layer until printing is finished. After all, layers are printed, the item has to be rinsed using a solvent and then put in an ultraviolet oven to complete processing.

Generally speaking, SLA can produce parts with very high dimensional accuracy and with intricate details. And parts made from SLA have a very smooth surface finish, making them ideal for visual prototypes. However, SLA parts are generally brittle and not suitable for functional prototypes. The mechanical properties and visual appearance of SLA parts will degrade over time when the parts are exposed to sunlight.

Resin, a type of light-reactive thermoset polymer, is the most common material used for SLA 3D Printing. A wide variety of resins are commercially available, including standard resins, engineering resins, dental and medical resins, and castable resins.

Selective Laser Sintering (SLS)

Creating an object with powder bed fusion technology and polymer powder is generally known as selective laser sintering (SLS). The process was developed and patented in the 1980s by Carl Deckard - then an undergraduate student at the University of Texas - and his mechanical engineering professor, Joe Beaman.

Objects printed with SLS are made with powder materials, most commonly plastics, such as nylon, which are dispersed in a thin layer on top of the build platform inside an SLS machine. A laser, which is controlled by a computer that tells it what object to "print," pulses down on the platform, tracing a cross-section of the object onto the powder. The laser heats the powder either to just below its boiling point (sintering) or above its boiling point (melting), which fuses the particles in the powder together into a solid form. Once the initial layer is formed, the platform of the SLS machine drops — usually by less than 0.1mm — exposing a new layer of powder for the laser to trace and fuse together. This process continues again and again until the entire object has been printed. When the object is fully formed, it is left to cool in the machine before being removed.

The most notable difference between SLS and SLA is that it uses powdered material in the vat rather than liquid resin in a cube, like SLS does. Plus, SLS does not have to use some other support structures as the object being printed is surrounded by unsintered powder.