CENAMEX
3D PRINTING and CAO
What is 3D printing?
3D printing is a manufacturing method that consists of depositing layers of material on top of each other. When used on an industrial scale, 3D printing is called additive manufacturing (AM), as opposed to traditional subtractive manufacturing processes like CNC milling.
This technology, invented in the early 1980s, has been around for about four decades. While 3D printing initially appeared as a slow and expensive method of manufacturing, it is now faster and more affordable than ever.
3D printing: how does it work?
A 3D model is first cut into hundreds or even thousands of thin horizontal layers by a dedicated software («slicer»), then exported in G-code format. This 3D printing format is a language that allows the 3D printer to know where and when to deposit material.
Each layer corresponds to the exact 2D shape of the object at its different height levels. For example, when printing a pyramid in 3D, the first layer (at the base of the pyramid) would be a flat square, and the last (at the tip of the pyramid) would simply be a dot.
The layers are 3D printed one on and one after the other until the object is finished.
The main 3D printing technologies
There are several ways to print objects in 3D. The main 3D printing processes or technologies available today are:
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FDM («fused deposition modeling»), with plastic filament coils as consumables
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SLA (stereolithography), where a laser or light projector photopolymerises (solidifies) resin
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Powder fusion or sintering (PBF, SLS, SMS, etc.), methods where plastic or metal particles are fused using powerful lasers
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Material jet ("material jetting" or "binder jetting"), when microscopic drops of material or bonding agent are deposited on a powder bed
These 3D printing technologies each have their strengths and limitations, and are adapted to different types of industries and use cases.
Melt Filament Deposition (FFF, FDM)
When explaining what 3D printing is, we tend to illustrate 3D printing methods based on deposition of melted wire, because it is the most used technology and one of the easiest to understand.
An FFF (or FDM, Fused Deposition Modelling) 3D printer draws a layer of molten plastic on its bed or printing tray. The filament is heated within what is called the extruder, which pushes the molten plastic through the nozzle.
Stereolithography (ALS)
Stereolithography is a 3D printing technique that uses photosensitive resin as a consumable. A laser or light source solidifies the resin.
The solidification process is known as photopolymerization and can be done in several ways:
SLA laser: a laser beam polymerizes the resin point by point, layer by layer.
DLP (Digital Light Processing): a projector emits light that is precisely redirected to the resin thanks to a system of mirrors.
MSLA (Masked Stereolithography): a device projects light that is selectively masked by an LCD screen.
Resin 3D printers are able to print much finer layers than FFF 3D printers, offering a much higher level of detail. These machines are often used by dentists and jewelers, for example.
PBF (Sintering or melting on powder bed)
There are many printing methods based on sintering or powder melting, the most common being SLM (Selective Laser Melting) and SLS (Selective Laser Sintering) technologies.
A powerful laser source is directed onto a bed of powder 3D printing material. The heat emitted by the laser fuses or melts the material particles together.
These techniques are often used to print metal but are also compatible with certain plastics such as nylon.
Material projection
3D printers with material spraying are the ones that look the most like ordinary paper printers. They are equipped with hundreds of small nozzles that deposit ink on a layer of powder.
Either the ink is the material to be printed, or the ink is a binding agent (a sticky liquid) that is deposited on the material to be printed.
The main materials for 3D printing
Today, many 3D printing materials lend themselves to various 3D printing technologies. From thermoplastics to metals and ceramics, and from food to living cells and concrete, almost anything is possible.
Thermoplastics
The most common 3D printing material is still plastic.
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Standard thermoplastics are often used by hobbyists and professionals. These include PLA and ABS, which are quite easy to 3D print.
More technical plastics, called engineering or performance plastics, such as nylon or PETG, are more delicate to print. They require higher extrusion temperatures and typically a closed frame printer to protect against drafts or temperature changes.
High performance polymers like PEEK are preferred when parts need to withstand high temperatures, chemicals, moisture, and other harsh conditions. These 3D printing materials remain expensive, complex to print and require the use of a high temperature 3D printer.
Composite 3D printing materials
To benefit from the various advantages offered by different types of materials, one can choose to print a mixture of two or more materials that form a composite material.
Composite materials can include basic materials like PLA-wood, but also very strong and resistant materials like Nylon loaded with carbon fibers. With the right equipment, continuous fiber can even be deposited directly during the 3D printing process.
Metals and ceramics
Within the 3D printing ecosystem, more and more manufacturers are developing solutions for 3D printing of metals and ceramics.
Most of these solutions are very expensive industrial additive manufacturing machines that produce green parts requiring post-processing (debinding, sintering, etc.) before use.
Food 3D printing
At the moment, the possibilities for food 3D printing are limited. In order to be printed, a food must be in the form of extruded paste.
That’s why the most common form of food 3D printing today is chocolate 3D printing, easy to soften and extrude. Nevertheless, this remains a difficult task, because the taste of chocolate is altered when exposed to significant temperature changes.
It is thus essential to find the perfect compromise between heat, to be able to extrude it, and cold, so that the layers can harden and hold on top of each other.
These are just the main 3D printing materials available, and they all require different types of 3D printers. Thus, companies often use 3D printing service providers.
