If you google 3D printing or additive manufacturing (AM), you’ll find it defined as “a process that creates a physical object from a digital design”. But there is an abundance of physical objects that exist today which were made from digital designs but not 3D printed. Could your sweater be 3D printed? What about those glamorous cakes sold in stores? The answer is in the details.
There are many different technologies of 3D printing. What they all have in common is that they build objects layer-by-layer according to the code they receive. This code, which forms the blueprints of an object, contains a set of coordinates for a machine to follow to shape material to create the object - similar to how you would play Connect the Dots to create a picture on a piece of paper.
However, before you have a code, you need to get a digital model or Computer-Aided Design (CAD) file. Programs called slicers to analyze the file and generate a code by slicing an object into thin layers and applying the settings for the 3D printing process.
Another common feature of all 3D printers is their ability to move in 3 axes which puts them close to CNC machines. The key difference between 3D printers and CNC machines is that instead of removing material, they add it. Hence the name - Additive Manufacturing.
Before the invention of 3D printers back in 1980, we’d already been producing a wide variety of objects using other machines and processes. So, you may be asking why 3D printing was introduced?
Many production methods are based on subtractive manufacturing – “the large family of machining processes with material removal as their common theme”. 3D printing, on the other hand, operates on the opposite end of the spectrum by building an object from scratch. This leads to the efficient use of resources by minimizing waste and time spent, as well as opening a world of possibilities that would otherwise be impossible with traditional manufacturing methods.
The trick to it all is being able to understand which method you should use and when.
Despite the fact that the concept behind 3D printers is the same, the different technologies and materials available have a huge influence on the kinds of possibilities and specifications that each method brings to the table.
FDM is one of the most well-known 3D printing technologies on the market. It works similar to a glue gun or cream injector (depending on which one you use more). FDM machines use strings of solid material which they melt inside a heated nozzle to form an object.
Starting from the bottom of an object, FDM printers deposit layers of melted material on one another according to the coordinates received in the code. The extruded plastic cools and becomes solid quite quickly, so the machine can continue uninterrupted and place a new layer on top of the previous somewhat hardened layers.
It can be difficult to differentiate between a desktop and industrial FDM printer, especially in the case of hybrid printers. The biggest difference is the quality or resolution that they’re capable of producing. In addition to this are the specs which include size, hardware, software, frame material, sensors, and other features.
Professional-oriented FFF machines are also commonly optimized for working with tougher and stronger thermoplastics and metal-filled composites. For those purposes, industrial FDM printers usually have fully closed chambers with temperature control and stronger nozzles.
Due to the easy working principle of FDM printers, numerous upgrades and reworks are possible which can take the technology to a whole new level. There are FDM printers out there that can produce objects from concrete, metal, wood composites, and food such as chocolate, cheese, meats, and vegetables.
Typically, FDM printers have only one nozzle which extrudes the filament. However, some of them are capable of adding multiple nozzles to print several different strings at the same time. As a result, they are capable of using different materials in the same run – for example, adding a dissolvable support structure that is easy to remove.
This is how dual-nozzle FDM printers overcome some geometrical limitations such as overhangs and make hollow objects and elements easier to print and clean out. There are also different types of multi-material upgrades that enable the use of several colors at the same time to create colorful objects.
Some 3D printing technologies like stereolithography (SLA) use polymerization processes to create an object from a Photoresist liquid material. Polymerization had already been used for other manufacturing and personal processes – for example, creating stamps, dentures, PCBs, or even gel manicures. The key is in the photoresist material (photopolymer), essentially it’s a liquid resin that solidifies due to its reaction under a light source such as LEDs, lasers, UV lamps, etc.
These 3D printers make objects upside down by immersing the built platform into a resin tank and lighting the areas from underneath which results in materials becoming solid layer-by-layer. They use a code to coordinate the light source and polymerize only the areas that make up an object.
After the first layer is formed, the platform ascends to let the uncured resin fill the tank and the process begins once again until the whole object is created. As a light source, DLP printers use projectors to solidify the resin. This digital screen under the tank displays the image of each layer, built from square pixels like in old computer games.
Thanks to this, a layer of an object is formed from small rectangular bricks called voxels. DLP machines can be covered with toned glass/plastic to prevent outside lighting such as the sun and lamps from reacting with the resin. After an object is finished, it also needs to be cleaned from left-over liquid and cured under UV light or natural sunlight to solidify better.
SLA printers work almost the same as DLP machines but source their light from lasers. Generally, the laser inside the machine transmits light to the galvanometer or a deflection mirror that is in motion. Their role is to aim the laser beam in accordance with the code to the specific areas on a print bed that needs to become solid.
Lasers can create smooth rounded lines and be more precise lighting the material, so good SLA machines (even desktop ones) have higher resolution and a smoother surface of prints than DLP printers. However, a single laser beam needs to travel around the whole contour of the object making the printing speed lower in comparison to DLP and DUP technologies.
SLA printers can cure resin through the translucent bottom of the tank like DLP but also from the top of a bath with the material. In the latter, the build platform isn’t lifting up but rather, slightly going down while a roller moves across the build chamber to smooth out the solidified layer and bring more uncured resin to the printing area.
This technology is also another type of DLP printing but an improved one for increasing the working speed. CLIP printers also use projectors as a light source but, instead of lifting the platform after every single layer created, they continuously lighten photopolymer. To make such production possible, these machines have an oxygen-permeable membrane that lies below the resin and creates a “dead zone” of uncured photopolymer. Thanks to this, CLIP printing is usually much faster than SLA while maintaining a high resolution for detailed parts.
In recent years a variety of low-budget resin printers appeared on the market. With slightly different technology names, they all have a common curing solution that makes affordable printing possible. As a light source, these machines use LED lights, usually placed in a matrix. It slightly limits compatible materials, as the LED light source is usually working on 405 nm resins exclusively. Though more diverse resins of this kind are now on the market.
To transfer the layers the lights cure resin through an LCD screen, which darkens the areas needed to be untouched. While the tech is affordable, the printing quality of such desktop printers continues to improve due to their popularity among 3D printing enthusiasts. And, what’s better, this technology wins in printing speeds as LED matrix paired with monochrome LCD screen can cure the resin in several points at once.
Unlike FDM technology, polymerization is a more complicated process that requires bigger expenses, simply because strong and precise light sources and photopolymers cost much more than plastic and heating tools.
Despite the fact that polymerization technologies are capable of high detail, some low-end DUP machines with weak light sources or poor quality deliver bad results - poor details, cracks, and fragile parts. It also becomes hard to defy professional and amateur machines, especially because of the growing interest in SLA and DLP printing.
Some desktop machines, like the ones made by Formlabs, are widely used by professionals like dentists and jewelers despite their size and affordable price of $3,499. Yes, that is considered affordable when compared to the Carbon M2 (CLIP) printer which costs $50,000 per year (three-year minimum) plus $10,000 installation and training fees over $14,000 for accessories package.
If you enjoy building sandcastles on a beach, you would probably like the next group of 3D printers. Powder Bed Fusion is a 3D printing technology group that works with powdered materials such as gypsum, sandstone, metal alloys, nylons, and others.
The working principle is also quite simple: these powdered materials are melted or sintered layer-by-layer at the positions where the object needs to exist. The melted or sintered powder becomes solid, so after a single layer is done, the platform goes down and a roller spreads new powder across the area.
SLS technology is a great example of the powder bed fusion method. It works with monochrome powdered materials like nylon (polyamide), ceramics, glass and its many variations. Currently, there are a large number of materials with different properties including durable, strong, and biocompatible.
Despite SLS printers coming in a desktop version, this technology is commonly used in industrial manufacturing with large build volumes. As the main tool, these printers use a high-powered laser to sinter the powder. After all the layers are completed, a specialist removes the unused powder and cleans parts just like an archeologist cleans a site that contains dinosaur bones.
Although this technology is a variation of SLS, the working principle is the same. The main difference is that DMLS printers work with powdered metal alloys that allow the production of metal parts from stainless steel, maraging steel, cobalt-chromium, inconel, aluminum, and titanium. Of course, metals are harder to melt, so the surface of a part printed on a DMLS machine can be rough.
These parts usually require post-processing: machining or laser polishing to improve the final appearance. However, the geometrical possibilities and the production speed make the DMLS process a strong competitor to other methods in aerospace, medical, prototyping, and tooling spheres.
SLM technology is a close relative of DMLS and SLS but rather than the laser sintering the metal powder, it melts it. So, as DMLS printers heat the powder up for the grains to fuse together, SLM machines melt them to become a liquid and solidify together completely. This leads to the parts coming out stronger and less porous.
One more technology, which can work with metal powders, is EBM. Like SLM, EBM printers melt the powder into a solid piece. The difference is that instead of a laser inside they use an electron beam (controlled by a computer) to heat and melt the material. EBM printing is performed in a vacuum and can reach temperatures of up to 1832 degrees Fahrenheit or 1000 degrees Celsius! An electron beam is also a stronger energy source (due to a higher density), so generally, it has better build rates and makes it possible to print with reactive and stronger materials. Some researchers have developed ways to produce parts from copper, niobium, and bulk metallic glass on EBM printers.
While some manufacturers focused on improving the heat source to melt powder better, others chose to improve the SLS method another way. Binder jetting technology also prints with powder (gypsum, sandstone, metal), but instead of sintering or melting it, these machines use an agent to bind grains together. Just imagine pouring glue on sand – this machine does almost the same thing but with extremely thin layers and under precise computer control. The process starts the same: a roller puts a thin layer of powder material across the build area. Then the 3D printer applies a binder agent to the areas which should be connected. After that, the platform goes down and a new powder layer comes on board to continue on the next layer.
On top of that, the gluing agent can be combined with color inks – in this case, it’s possible to print a colored object within 390,000 combinations of CMYK colors from sandstone. This method is called Color Jet Printing (CJP) and it’s popular among artists and architects.
MJF technology is quite young in comparison to the previously mentioned technologies above. If explained simply, MJF is like a hybrid between Binder Jetting and Laser Sintering. As is the case with both of them, MJF works with a certain powdered material to create an object - PA 12 (Polyamide). Printing starts with jetting a fusing agent and a detailing agent onto the areas mapped out by the code. This melts powder grains, and then the printing continues with heating the powder by a lamp after every single layer is created.
Material jetting 3D printing technology is a method most commonly compared with 2D printing with inks. Like FDM, this technology spreads the material on a build platform. However, instead of melting a solid material, it works with liquid photopolymers which are cured by UV light after a single layer is applied. Also, the difference is that instead of using a nozzle that moves across the printer, some material jetting machines have several nozzles to allow for some industrial printers to combine several materials at the same time. The range of photopolymers available is excellent – it’s possible to print flexible, tough, colored, and biocompatible parts.
LOM 3D printers are probably the most similar to their 2D predecessors which print documents and photos on paper. That’s because this technology works with sheets of adhesive-coated material (paper, plastic, or metal). LOM printing starts with bringing the first sheet to a build platform, where a knife or a laser cuts a form of an object according to the code. After a layer is completed, a new sheet of material is applied to the platform. Then the platform glues and presses the sheets together and starts cutting a new form. This process continues for every layer until a final part is produced in its entirety. A printed piece needs to be removed from extra material after printing.
LOM printing can be colourful, too, with impressive precision. Even if an object had been printed using an ordinary copy paper, it’s quite solid and can even be drilled! That makes LOM technology one of the cheapest and environmentally friendly options available. Paper prints display wood-like properties and can be strengthened through post-processing.
One more technology, which allows playing with CMYK inks, appeared recently on the market when company XYZ Printing released their da Vinci Color machine. Inkjet FDM printing is a mixture of single-nozzle FDM printing and ink jetting. The printer builds an object layer-by-layer by melting a string of white plastic but with a kicker, it adds ink at every layer. As a result, Inkjet FDM printers are capable of producing parts in a multitude of colors like that of industrial machines but within a desktop format.
3D printing is developing at a rapid pace, with new machines, upgrades, materials, software, and technologies appearing on the market every day. Some methods prove to be useful and become adopted into the mainstream, while others just copy previous techniques.
In order to truly see the benefits of 3D printing manufacturing, the best practice is to include it into the production line smartly. All 3D printing technologies are good for prototyping, replacement parts and low volume runs. Within these fields, 3D printing has great competitive advantages:
Wide choice of materials and colors, dimensional possibilities make 3D printing a great method, capable of delivering unique, complicated, functional prototypes of almost everything. Many industries integrate 3D printing to a prototyping or product development stage to cut down the expenses and create a new product or part quicker, and better. The more expensive and precise a product needs to be, the more important the prototyping step becomes. No matter what products a company creates, physical prototypes allow for thorough product testing to identify design flaws and help to avoid mistakes before committing to mass production.
Many present-day manufacturing methods were created to support mass production, which means they are only profitable when several thousand copies are produced. However, not all products require mass production, so 3D printing is suitable for low volume manufacturing and better than molding for example.
Nowadays, people tend to prefer products created especially for them – that includes clothing, glasses, jewelry, devices, and much more. Some customers are even willing to pay extra for a product that fits their personal needs and tastes, which creates a strong demand for 3D printing to join the game. Designers, retail outlets and companies can offer people personalized and custom goods ranging from some simple everyday products like toothbrushes to custom 3D printed bicycles, made fast.
Many complex tools, machines and devices need replacements from time to time. It’s easy to lose customers if you’re not available when they need you. 3D printing provides low-cost and fast replacement parts and is particularly useful for discontinued products. Because a part can be created on-demand from a digital file, manufacturers don’t need to waste time and resources on producing spare parts before they are needed and focus on new products for their customers. When a replacement part is needed, additive manufacturing is the solution.
Similar to that of prototypes, props, mock-ups and demonstration models need to be unique and aesthetically pleasing. In this way, 3D printing became a game-changer for architects, designers, movie makers, animators, fashion designers and ordinary companies with creative marketing ideas. The potential to create impressive demo events and models quickly can accelerate sales, improve branding and marketing, which are critical to being competitive.
While some products can be standardized for the masses, implants, prosthetics and other medical devices should be customized for each individual to optimize comfort and effect. Some of them should also be made with a fast turnaround and that’s where 3D printing comes into the picture. In addition, instead of creating a unique 3D model manually every time, 3D scanning can be used as well as modeling software tools. Manufacturing implants on a 3D printer can sometimes not be the cheapest option but it is a much easier and more precise one.
Image: 3D printed prosthetic hand
