Generally when we talk about 3D printers and 3D printing we refer to additive manufacturing, but there are many 3D Print Technology. Infact this term describes a set of technologies that create objects in three dimensions adding material layer by layer. The materials used can vary from technology to technology. However there are some common features for all production methods. One of them is the use of a computer combined with a special software for this 3D modeling.
Obviously, if you want to print an object in 3D, the first thing to work on is the creation or, in any case, the three-dimensional CAD drawing. Then, with an appropriate extension, you have to transform the three-dimensional model into a file with an STL extension. In this section the main 3D drawing programs.
Once the drawing is complete, you will have to pass to the slicing program. Slicer: here you can find the most used and widespread. That software reads data in STL format and translates the model with structure “layer by layer” in machine language. Now you can print your model with any method, which can be any of the methods listed below.
There are in fact many 3D printing technologies and this article focuses on the explanation of these, trying to understand together the principles of operation:
- Stereolithography (SLA)
- Digital light printing (DLP)
- Modeling for deposition of molten material (FDM)
- Selective laser sintering (SLS)
- Selective laser fusion (SLM)
- Electronic Beam Fusion (EBM)
- Creating a Laminated Object (LOM)
3D Print Technology: Stereolithography (SLA)
Stereolithography is the oldest method and dates back to the prehistory of 3D printing, but it is still in use today. The idea and applications of this method are surprising.
This method was patented by Charles Hull, co-founder of 3D Systems, Inc. in 1986. The printing process involves uniquely 3D printers called stereolithographic apparatus. They convert liquid plastic into solid 3D objects with the help of a beam of laser light.
As mentioned earlier, all 3D Print Technology require a file processed with a computer, with the help of a design program to process the object. This file contains all the information on the three-dimensional representation of the model. You have to convert the CAD file into a format that the programs can understand for further processing, the STL format. The STL file is common in lithography, as is the case for almost all three-dimensional printing methods.
These SLA presses don’t work like the common desktop printers. The stereolithographic printers work with an excess of liquid plastic “loaded” with a photosensitive material. When the laser lights it for a certain period of time, it hardens and becomes a solid object. Normally the result is a three-dimensional object with very smooth walls. However, the quality of the printed objects is proportional, as usual, to the quality of the 3D printers.
The printing process includes all the different steps we have summarized above: Starting with the creation of the 3D model in the CAD program, a special add-on of the software processes the CAD model and generates STL files that contain the information for each layer.
How it works
Normally the layer is 0.1mm and then there are ten levels for each millimeter. Then SLA machine starts the procedure and starts to “illuminate” the liquid plastic, thus forming the first layer of the object.
When the plastic is hardened, a quantity of liquid plastic equal to the processed plastic is put back into the tank. So, the bed is lifted and continues layer by layer until the project is completed. Once you have printed all layers, you must rinse the object with a special solvent. Then you have to place it in an ultraviolet oven to complete.
The time it takes to print an object depends on its size. Small items can be printed within 6-8 hours with a small printer. For large 3D items, several meters long, the printing time can be up to several days.
Stereolithography is widely used in prototyping as it does not take too long to produce an object and the cost is relatively cheap compared to other means of prototyping. This 3d printing method is rarely used to print the final product.
Although stereolithography is considered the oldest 3D printing technology many companies still use it to create prototypes of their designs. 3D Systems Inc., the company that started using this method for prototyping, sells its own machines.
Although FDM products are normally used for domestic use, because they are cheaper and simpler for self-construction, there are stereolithographic printers for home use.
3D Print Technology: Digital Light Processing (DLP)
Digital Light Processing is another 3D Print Technology very similar to stereolithography. The DLP technology was created in 1987 by Larry Hornbeck, and is a patent owned by Texas Instruments. It has become very popular in the production of projectors. It uses digital micro mirrors arranged on a semiconductor chip. The technology is applicable to film projectors, mobile phones and 3D printing.
DLP, 3D Print Technology, works like SLA with photopolymers. What makes the SLA and DLP processes different is the different light source used for polymerization. In this process, the light comes from a liquid crystal display, which is applied to the entire surface of the material during each step of the printing process.
The material to be used for the printing is liquid plastic resin that is inserted in the tank. The resin hardens quickly when hit by light. The great advantage of this method is the impressive print speed. The layer of hardened material can be created with this technology in seconds. When the layer is finished, it is moved upwards and processing of the next layer begins.
The results obtained are robust and have excellent resolution.
DLP are a good chance for who want to start with resin prints and don’t have big budget, here i want to show you 2 great printers DLP under 500$:
3D Print Technology: Fused Deposition Modeling (FDM)
Fused Deposition Modeling (FDM) 3D Print Technology was first developed and implemented by Scott Crump, founder of Stratasys Ltd., in 1980. Other 3D printing companies have adopted similar technologies but with different names. A well-known company, MakerBot coined an almost identical technology, known as Fused Filament Fabrication (FFF).
With FDM (Fused Filament Fabrication) you can print not only functional prototypes, but also conceptual models and products without post-processing. What is really interesting about this technology is that all printed parts have excellent thermal, chemical and mechanical performance (always in relation to the quality of the filament purchased). This is very advantageous for the user. These printers, as mentioned, use reels of special thermoplastic filament that are marketed in 2 different diameters: 3 mm and 1.75 mm.
There are also various formats of weight, in fact you can buy reels of 10m (special format for testing of about 6 grams), 20 m, 250 g, 500g, 1 kg and 2.2 kg, in short, for all needs. The price of the filament is variable according to the material and quality and ranges from 15 to 100 euros per kilogram. In this article you can learn about the many varieties of filaments on the market.
An infinity of geometries
The term Fused Deposition Modelling contains many 3D Print Technology of realization, among the most famous models are certainly the Cartesian Prusa i3, Core XY. The first has a moving plate only for the Y axis and an arm that moves the extruder in X and Z. The XY core, on the other hand, has a moving plate in Z and a moving extruder on “rails” in X and Y. Then there is a further variant that is represented by the Delta model, where the extruder is moved by 3 arms that are horizontally, thanks to the intermovement the extruder can move throughout the plate, which is generally round.
FDM 3D Print Technology is now widely used in an infinite variety of sectors. From car manufacturers such as Hyundai and BMW to food companies such as Nestlè. The FDM is used for the development of new products. It is used to develop the “concept” of the model and for its prototyping. It is the most widely used technology because with this printing method it is possible to construct objects with complex geometries and cavities.
The price for 3D printers depends on the size and model. Professional printers normally have prices of around 10,000 euros. While 3D printers designed for domestic use are not so expensive. We find several models of different brands including MakerBot, Ultimaker, Zortrax, Delta that offer products of excellent quality for less than 3/4,000 €. However, there are many people who prefer to create their own printers with the help of KITs or even from scratch. There are a lot of websites that offer a wide variety of DIY kits that allow you (after assembly) to have a good home product from just 180 €.
3D Print Technology: Selective Laser Sintering (SLS)
Selective Laser Sintering (SLS) is a 3D Print Technology that uses the laser as an energy source to form solid 3D objects. This technique was developed by Carl Deckard, a student at Texas University and his professor Joe Beaman in 1980, a patent later acquired by 3D Systems in 2001. As mentioned earlier, 3D Systems Inc. developed stereolithography, which is somewhat similar to SLS, the main difference being that it uses powdered material in the tank instead of liquid resin.
Like all the other 3D Print Technology listed above, the process starts with an STL file. The printable material with could be anything: nylon, ceramic, glass and some metals such as aluminum, steel or silver. Due to the wide variety of materials, this technology is very widespread especially in professional printing.
In fact, requiring high power lasers is economically disadvantageous for home use. However, there are several start-ups working on the development of low cost SLS presses.
3D Print Technology: Selective laser melting (SLM)
The SLM is a technique that uses a high power laser beam that melts and melts metal powders together. In many sources the SLM is considered a subcategory of selective laser sintering (SLS). But this is not so true as the SLM process completely melts the metal material before transforming it into solid. This is a big difference with selective laser sintering. The history of SLM began with a German research project dated 1995.
As with all other printing methods, it needs a 3D design and a slicer that “cuts” the model into layers. The file format used by the press is a standard STL file. Immediately after loading, the press software assigns parameters and values to the construction of the path.
The metal powder is evenly distributed on a plate, then each 2D slice is melted by the application of the high energy laser. The laser melts a first layer and when the layer is completed the process starts again for the next layer. Metals that can be used with this technique include stainless steel, titanium, cobalt chrome and aluminum.
A lot of pioneering SLM projects have been dedicated to aerospace applications for the manufacture of parts in very light materials.
As for selective laser sintering also this technology does not find many followers among home users, the main users are companies that produce aerospace items and medical orthopedics.
3D Print Technology: Electron beam melting (EBM)
EBM is another type of additive manufacturing for metal parts. It was originally studied by Arcam AB Inc. at the beginning of this century. Also this technique is very similar to SLM, this method of printing however uses an electronic beam instead of the high-energy laser, which is the main difference between these two methods. The rest of the processes are quite similar.
The material used in EBM is metal powder that melts and forms a new object layer by layer. Contrary to SLS, EBM goes into full metal powder melting. The process can reach temperatures of 1000°C.
Comparing it with SLM EBM process is quite slow and expensive, even the availability of materials is limited. So the method is not so popular although still used in some manufacturing processes. Currently the most commonly used material for EBM is pure titanium. The application of EBM mainly focuses on biomedical plants and aerospace.
3D Print Technology: Laminated Object Manufacturing (LOM)
The manufacturing of laminated objects (LOM) is another rapid prototyping system that was developed by the California-based company Helisys Inc.
During the LOM process, layers of laminates of paper, plastic or adhesive metal are fused together by heat and pressure. Then cut into the desired shape with the help of a computer that controls a laser or knife.
The LOM process consists of several steps. First, as usual, the CAD file is transformed into an STL file.
LOM printers use a continuous sheet coated with an adhesive, which is fixed to the plate by a heated roller. The heated roller that passes over the sheet of material melts the adhesive and then the laser or blade cuts the workpiece to the desired size. After the layer is finished, the platform is lowered, a new sheet of material is deposited and the heated roller adheres. The process is repeated over and over until the 3D object is finished.
When the excess material has been cut, the workpiece can be polished or sealed with paint. If paper materials were used during printing, the object will have the appearance and properties of wood, otherwise other materials will be used.
Surely the LOM is not the most popular 3D printing method, but one of the most convenient and fastest. The cost of printing is low because the raw materials are not expensive and the objects printed with LOM can be relatively large.
Not very widespread
There are not many fablabs working with LOM 3D Print Technology at this time. But it is worth mentioning the Irish company Mcor Technologies Ltd. which sells LOM printers. Artists, architects and developers use their product, simply writing paper.
In our journey through various 3D printing technologies we have included only the most popular methods. However if you have something to add, clarify or correct please do not hesitate to write in the comments. We will be happy to enrich this space with additional information.