Extrusion of Materials is the act of selectively squeezing a material through a nozzle or aperture, and it's what most people imagine when they think of 3D printing. Consider a hot glue gun with a computer controlling each droplet of glue and a pair of rails moving it around. Some of the early consumer 3D printers, such as the MakerBot, used this fundamental structure, which is also known as Fused Deposition Modeling (FDM). This is the type of printer that hobbyists use: the device melts a plastic-like filament or wire by forcing it through a heated nozzle. Although some of these printers can also push out liquid materials, this fundamental structure is ideal for materials like thermoplastics and soft metal filaments.
The adaptability of this printer type, as well as the comparatively inexpensive cost of both building and managing the printer and the supplies, is appealing. In 2020, a home 3D printer, an Ender 3, will cost under $200 and is open-source. In a kind of rudimentary cloning capacity, it can even print many of its own parts.
Material extrusion printers can be scaled up to accommodate concrete mixtures for home construction, or adapted to support edible ingredients for food printing. It's no surprise that this type of printer has piqued the public's interest and, perhaps more than any other, has sparked the AM revolution.
Despite its intimidating name, vat photopolymerization is a straightforward procedure. You may be familiar with photopolymers if you've ever had a chipped tooth or a cavity. The substance is a paste that is molded into the shape of your teeth and solidifies when exposed to UV light. It is then sculpted with a dental bur and-voila!-instant tooth repair. Consider how useful this curing process would be in the construction of a 3D printer.
Light pulses were targeted towards a thin vat of liquid photopoly. Some of the liquid layers solidify into a complicated 2D form using mer resin. Light-activated polymerization is the name for this method. The hardened structure is vertically pushed a few nanometers by a mechanical arm, and the light repeats the process for the next layer. You create a 3D structure out of solid resin over time.
Unlike material extrusion, vat photopolymerization does not use a nozzle to deposit a thin layer of material; instead, the printing process uses a mirror galvanometer, or galvo for short, to regulate light. In addition, unlike material extrusion, which prints from the bottom up, vat photopolymerization prints the top layer first and then works its way down.
Vat photopolymerization, the oldest kind of additive manufacturing, was invented in the 1970s by Dr. Hideo Kodama as stereolithography (SLA), but he was unable to submit a patent owing to financial constraints. Chuck Hull was given a patent for SLA in 1986 and began a 3D printing firm shortly after. This is widely regarded as the beginning of contemporary 3D printing. The focus was on quick prototyping at the time, but it has subsequently moved beyond these early use cases. Vat photopolymerization is now widely used in areas where a smooth surface and precise features are required, such as medical applications. For years, the dental company Invisalign has used SLA technology to mass create individual aligners.
Powder Bed Fusion
The preceding two 3D printing categories mostly focus on different types of polymers. However, metal components are occasionally required, and powder bed fusion is a viable option. The 3D sculpture is built one layer at a time from a vat of material, similar to stereolithography. Instead of a shape being cured and lifted up from a liquid resin, an energy source fuses a powder to the desired shape one layer at a time before adding another. There are a few advantages to this method. The powder is first melted using high-energy sources such as lasers. Powdered metal materials, in addition to powdered plastics, can be included in the range of materials. Second, powder bed fusion techniques can produce stronger components because of the materials used and their high melting temperatures, however at a higher cost than other methods. Third, because the 3D design is created inside a bed of powder, the requirement for support structures is almost eliminated, resulting in less waste. The powder bed that isn't in use may often be reused.
The classic technique for powder bed fusion is selective laser sintering (SLS), which entails employing a guided laser as the energy mechanism to fuse the powder. The laser is guided via galvos, the same as stereolithography. Other types of powder bed fusion include Direct Metal Laser Sintering (DMLS), Selective Laser Melting (SLM), and Electron Beam Melting (EBM).
Directed Energy Deposition
Directed energy deposition is what would happen if material extrusion and powder bed fusion had a child. By melting granules or wire as they are deposited, this technique concentrates thermal energy to fuse materials. From laser (Laser Engineered Net Shaping, or LENS) to electron beam (Electron Beam Additive Manufacturing, or EBAM) to plasma arc, the energy source determines the type of machine (Plasma Arc Directed Energy Deposition, or PA-DED).
The potential of this method to fix existing parts rather than create new components is intriguing. On a shop floor, a directed energy deposition machine can fix everything from handheld equipment to turbine blades. DED may be thought of as a sort of auto welding machine in its most basic form.
MIT invented binder jetting as we know it now in 1993. The business ExOne then developed the technique to work for printing metals in 1996. It's a hybrid of powder bed fusion and a standard inkjet printer you'd get at home. Binder jetting allows for the creation of complicated 3D geometry without the need for supports. Rather than employing a high-energy source to fuse each layer, liquid binding agents are used to combine powdered components. Consider minuscule drops of glue dripping over a layer of baby powder to create a flat form, then layering on top of that. That's the gist of it. It differs from conventional 3D printing technologies in that it uses chemical processes rather than heat or light. This helps to prevent some of the distortions and stress issues that might come from operations that need heat, such as warping.
Binder jetting may be used to make huge structures out of powdered materials like sand or ceramics, such as a 3D printed pedestrian bridge in Madrid. While it may be used to fabricate some metal items directly, it can also be used to print 3D sand castings, which are used to shape molten materials such as iron or steel. This is a contemporary take on a centuries-old foundry method.
Material jetting is comparable to inkjet printing and material extrusion. Material jetting, like material extrusion, drops material droplets onto a build plate, where they cure when exposed to UV light, necessitating photopolymer resin-similar stereolithography. The capacity to accommodate various materials created in the same item distinguishes material jetting from material extrusion or stereolithography. Material jetting, unlike many other methods, enables full-color printing. If you've ever seen a home 3D printer, you'll notice that they usually only print in one color.
Drop on Demand (DOD) is a specialized material jetting technique. However, rather than being general-purpose, it has certain heads that are engaged in the deposition of dissolvable support material and others that manufacture the model. Lost-wax castings are frequently made with DOD printers.
"You can have a job done fast, cheap, or excellent, but you can't have all three," as the old adage goes. Sheet lamination is a clear illustration of fast and inexpensive in the field of 3D printing. Paper and aluminum foil are the materials of choice in this process, and the machine uses lasers to cut shapes and glue them together one sheet at a time. The result of sheet lamination is fascinating in that, depending on the geometry, sufficient sheets of paper can begin to take on some of the strength and properties of wood. It's also simple to add color to the output using ordinary inkjet technology, thanks to the heat and harsh chemical-free procedure.
Laminated item manufacture is another term for sheet lamination (LOM). Sheet lamination is one of the greatest options for architectural models and product development. Some individuals have tried building furniture using this approach as well.
Because 3D printing is such a large area, this may have seemed like a thorough review. It's critical to recognize that the market encompasses far more than your nephew's home 3D printer. It's the next big thing in manufacturing. Material extrusion, vat photopolymerization, powder bed fusion, binder jetting, material jetting, directed energy deposition, and sheet lamination is the ISO/ASTM AM categories, to summarize. There is no quiz, but if you want to make a move in the AM space, you need to be conversant with the seven categories at a high level.