If you google 3D printing or additive manufacturing (AM), you will find this definition: “It is the process from digital design to making an article.” If you stop thinking for a few seconds, then It can be found that too many items are now made from a digital design. Is your sweater 3D printed? What about the exquisite cakes in the store? The answer seems to be in the details
How does 3D printing work?
There are many different 3D printing technologies, but one thing they have in common is that they build items layer by layer according to the received code. This code is a blueprint for an item. It contains a series of coordinated actions of the device. The materials are built together to make the item-similar to playing “connecting dots into lines” on paper and drawing a picture. However, before you get the code, you will have a digital file or a Computer-Aided Design (CAD) file. The device lets the cutter analyze the file, cut the item into thin layers, and generate code for use in the 3D printing process.
Why is 3D printing?
Before the advent of 3D printers in 1980, we had manufactured many items using other equipment and processes. So you might ask why 3D printing was invented? Many manufacturing methods are based on subtractive manufacturing— “the largest family of machining with the same theme of removing materials.” Instead, 3D printing builds items from scratch. By minimizing wastage and time, the effective use of resources is improved, and at the same time, a door is opened for areas that traditional manufacturing methods cannot manufacture. The secret is to know when and what technology you need.
What are the 3D printing methods?
Although the concepts contained in 3D printers are consistent, different technologies and available materials have a huge impact on manufacturing possibilities and the end result.
FDM is the most famous 3D printing technology on the market. Similar to glue gun or cream spray bottle (depending on which one you use more). FDM equipment Fluids that solid material melts in a built-in heating head to build items. Starting from the bottom of the item, the FDM printer deposits molten material layer by layer based on the coordinates provided by the code. The extruded plastic cools down and quickly forms a solid, so that the equipment is not delayed and new layers are formed on previously fixed layers.
Advantages: Desktop FDM printers and their material filaments are very cheap; a large number of materials and colors can be selected; simply working principles; some 3D printers can be purchased by buyers for multiple upgrades.
Disadvantages: Most cheap FDM printers have inaccuracy problems; universal gravity makes the printer unable to print items with large suspension structures without a supporting structure; items without a flat surface are more difficult to print from the beginning; they can be clearly seen on the surface See the hierarchy.
Fun fact: The range of FDM printers is very large, starting at $ 100 for desktop printers and $ 14,000 for industrial grades.
Industrial FDM Printer
It is very difficult to distinguish between desktop and industrial FDM printers, especially when it comes to hybrid printers. The biggest difference is the quality or resolution they can make. There are also dimensions, hardware, software, frame materials, sensors and other features.
Because of the simple working principle of FDM printers, many upgrades and reprocessing can bring technology to a new level. Did you know that there are FDM printers that can make items from cement, metal, composite wood and food from chocolate, cheese, meat and vegetables?
Double-head and multi-material FDM printers
Generally, FDM printers have only one print head that extrudes a filament of material. However, some can add multiple printheads to print multiple different fluids simultaneously. Eventually they can use different materials for the same use-for example, adding soluble support structures that are easy to remove. This is why the double-headed FDM printer addresses geometric constraints such as hanging and making hollow objects, and the elements are easy to print and remove. There are also different types of multi-material upgrades that enable the use of many colors to make colored items at the same time.
Some 3D printing technologies use polymerization to make items from photosensitive liquid materials. Polymerization has been used in other manufacturing and personal processes-for example, to make stamps, dentures, circuit boards, and even phototherapy nail art. Liquid resin that reacts and cures under light sources such as UV lamps.
Digital Light Processing (DLP)
These 3D printers immerse the printing platform in a resin tank and illuminate the area from below, layer by layer of cured material, and make items upside down. They use code to coordinate light sources and cure only the areas where items need to be crafted. After the first layer is made, the platform rises and fills the tank with unhardened resin. This process is repeated until the entire article is completed. As for the light source, DLP printers use projection or LED curing resin. The digital display below the tank displays the image of each layer with square pixels in old computer games. So each layer is made of small rectangular bricks called 3D pixels. DLP equipment can be covered with discolored glass / plastic to prevent external light sources and resins such as sunlight or table lights from acting. After finishing the item thick, it is necessary to clean up excess liquid and solidify under UV light or strengthen it under natural light.
SLA printers and DLP devices work almost the same way, but the light source is a laser. Generally, the laser inside the device transmits a beam of light to a galvanometer or polarizer in action. Their role is to make the laser beam and the specific area code to be cured on the printing plate focus consistent. Lasers can make smooth circular lines and illuminate materials more accurately, so good SLA equipment (even desktop printers) have higher resolution and smoother surfaces than DLP printers. But the LED can illuminate several points on the resin at the same time, and the laser beam needs to walk on the surface of this article. SLA printers can cure resin through the bottom of a translucent tank like DLP, and can also drip material from the top. In the latter case, the build platform does not lift, but instead drops slightly as the roller moves from the build chamber, smoothly removing the cured layer and moving more uncured resin into the print area.
Continuous Level Printing (CLIP)
This is another improved DLP print that speeds up work. The CLIP printer also uses projection as the light source, but instead of raising the platform after making each layer, it continuously irradiates the photosensitive material. To complete such production, the device needs an oxygen-enriched film under the resin and creates a “dead zone” for the uncured photosensitive material. Therefore, CLIP printing is faster than SLA while maintaining precision parts with high resolution.
Desktop and industrial converged printers
Unlike FDM technology, polymers are more complex processes that require greater expense, mainly because powerful and precise light sources and photosensitive materials cost more than plastic and heating tools.
Good news: some companies and enthusiasts have succeeded in inventing inexpensive desktop DLP printer models-some for less than $ 400.
The bad news: Photosensitive materials are still expensive-$ 70-80 per liter compared to high-end equipment resins of up to $ 200 per liter, which can be said to be very cheap.
Although polymerization technology can make high-definition, some low-end DLP equipment with weak light sources or low-quality photosensitive materials can also produce bad results-poor details, cracks and fragile parts. This also makes it difficult to distinguish between professional and amateur equipment, especially as there is growing interest in SLA and DLP printing. Some desktop devices, such as Formlabs’ products, are widely used by experts for dentistry and jewelry, despite their size and a reasonable price of $ 3,499. Yes, it’s quite cheap compared to the price of Carbon M2 (CLIP) $ 50,000 per year (minimum 3 years) plus $ 10,000 installation and training fees and more than $ 14,000 accessory kit prices.
Advantages of SLA / DLP / CLIP printing: finer; high resolution; no need to start with a flat surface; smoother surface; some resin types help make metal casting models, and ISO certified medical tools and equipment.
Disadvantages: printers and materials are expensive; fewer materials and colors are selected than FDM; some SLA printers are very slow; because of gravity, if the construction platform rises, complex items still need a “support” structure.
Powder bed fusion technology (SLS, DMLS, SLM, EBM, CJP, MJP, MJF)
If you like to build sand castles on the beach, you will also like the next set of 3D printers. Split bed fusion is a group of 3D printing technologies using powder materials such as gypsum, sandstone, metal alloys, nylon, and others. The principle is also simple: these powder materials are melted or sintered layer by layer at the desired location of the article. The melted or sintered powder becomes strong, so after completing one layer, the platform descends and the rollers are covered with new powder in the area.
Selective laser sintering (SLS)
SLS technology is the best example of powder bed fusion method. Monochromatic powder materials such as nylon (nylon), ceramics, glass, and many variations thereof are used. There are a large number of materials with different properties, including durable, strong and biocompatible. Although there is a desktop version of the SLS printer, this technology is more widely applicable to industrial manufacturing with large build volumes. These printers use high-energy lasers to sinter the powder. After all the layers have been printed, someone will need to remove the unused powder and clean up the parts, just like the sister of archeology cleans up the scene with dinosaur fossils.
Advantages: SLS printer can manufacture very complex parts without support at all; strong printing mechanical properties; good chemical resistance
Disadvantages: Printed product is porous and needs to be sealed; Cannot print hollow but fully enclosed parts because unused powder will remain in the part; heat treatment is required after completion of production
Direct metal laser sintering (DMLS)
Although this technology is another form of SLS, it works the same. The main difference is that DMLS printers use stainless steel, maraging steel, cobalt-chromium, nickel, aluminum, and titanium alloy powders that can make metal parts. Of course, metals are more difficult to melt, so the surface of items printed with DMLS equipment may be rough. These parts often require post-processing: machining or laser polishing to improve the final appearance. However, the shape possibilities and manufacturing speed make DMLS highly competitive in the aerospace, medical, prototyping, and ball mold fields.
Selective Laser Melting (SLM)
SLM technology is a close relative of DMLS and SLS, but replaces laser sintering and metal powder with melting. So when the DMLS printer heats the powder until the particles are fused together, the SLM equipment melts them into a liquid and completely solidifies. Parts made in this way are stronger and less porous.
Electron beam melting (EBM)
Another technique that can use metal powders is EBM. Like SLM, EBM printers melt powder into a solid. The difference is that the internal laser is changed to an electron beam (computer control) to heat and melt the material. EBM printing is suitable for vacuum and can reach 1832 degrees Fahrenheit or 1000 degrees Celsius! E-books are a more powerful source of energy (because of higher density), so often they have better construction rates and can be printed with reactive and stronger materials. Some researchers have improved their fabrication methods and printed with copper, niobium, and bulk metallic glass.
Binder jet and color inkjet printing
While some manufacturers focus on improving the heating source to better melt the powder, others choose to improve SLS in other ways. Adhesive spray technology uses powder (gypsum, sandstone, metal) but does not sinter or melt. These devices use media to bond particles together. Imagine pouring glue into the sand-the principle of the device is almost the same, but it has a very thin layer and is controlled by a computer. The procedure starts the same: the rollers spread a thin layer of powder over the build area. 3D printers provide connectable bonding media in the area. The platform will then descend to the new powder layer.
Most importantly, adhesive media can be blended with colored inks-so you can print from stones with 390,000 combinations of CMYK colors. This method is called color inkjet printing (CJP) and it is very popular among artists and architects.
Advantages: Requires less energy than SLS; can print in color; requires no support and can print the same size as SLS
Disadvantages: Items are fragile and require a coating to prevent absorption of moisture from the air; hollow closed parts cannot be made.
Multi-nozzle fusion (MJF)
MJF technology is relatively young compared to the previously mentioned technology. Simply put, MJF is a combination of adhesive and laser sintering. Like those two technologies, MJF uses powdered materials to make items-PA 12 (Polyamine). At the beginning of printing, spray the fusion agent and decoration agent on the area set by the code. The molten powder particles are then printed and the powder is heated by the bulb after each layer is made.
Advantages: Print speed several times faster; prints can withstand a variety of post-production (paints, spray paint, sandblasting, painting)
Disadvantages: Only polyamide can be printed at the moment; unique and expensive technology; can’t print hollow closed items
Material injection (MJP, MJF and PolyJet)
Material jet 3D printing is the technology most often compared to ink 2d printing. Similar to FDM, this technology sprinkles materials on the build platform. However, UV light-curable single-layer liquid photosensitive resins are used instead of molten solid materials. In addition, the difference is that it is not used for one nozzle to move inside the printer. Some material ejection equipment has multiple nozzles, which makes industrial printers use multiple materials at the same time. The range of photosensitive resins is also excellent-it can print soft, strong, colored and biocompatible parts.