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3D printing method


3D Printing | An Overview of 3D Printing Technologies

 

3D printing is sometimes referred to as Additive Manufacturing (AM). In 3D printing, one creates a design of an object using software, and the 3D printer creates the object by adding layer upon layer of material until the shape of the object is formed.  The object can be made using a number of printing materials, including plastics, powders, filaments and paper.

There are a number of 3D printing technologies, and this article provides an overview of those technologies.

Stereolithography (SLA)

Stereolithography makes use of a liquid plastic as the source material and this liquid plastic is transformed into a 3D object layer by layer1.  Liquid resin is placed in a vat that has a transparent bottom.   A UV (UltraViolet) laser traces a pattern on the liquid resin from the bottom of the vat to cure and solidify a layer of the resin.  The solidified structure is progressively dragged up by a lifting platform while the laser forms a different pattern for each layer to create the desired shape of the 3D object3.


Schematic representation of Stereolithography: a light-emitting device a) (a laser or DLP) selectively illuminates the transparent bottom c) of a tank b) filled with a liquid photo-polymerizing resin. The solidified resin d) is progressively dragged up by a lifting platform e)
Source: https://en.wikipedia.org/wiki/Stereolithography

Digital Light Processing (DLP)

3D printing DLP technology is very similar to Stereolithography but differs in that it uses a different light source and makes use of a liquid crystal display panel1.  This technology makes use of more conventional light sources and the light is controlled using micro mirrors to control the light incident on the surface of the object being printed. The liquid crystal display panel works as a photomask.  This mechanism allows for a large amount of light to be projected onto the surface to be cured, thereby allowing the resin to harden quickly1.

Fused Deposition Modeling (FDM)

With this technology, objects can be built with production-grade thermoplastics1.   Objects are built by heating a thermoplastic filament to its melting point and extruding the thermoplastic layer by layer.   Special techniques can be used to create complex structures.  For example, the printer can extrude a second material that will serve as support material for the object being formed during the printing process1.  This support material can later be removed or dissolved.

Fused deposition modelling: 1-Nozzle ejecting molten material, 2-Deposited material (modeled part), 3-Controlled movable table
Source: https://en.wikipedia.org/wiki/Fused_deposition_modeling

Selective Laser Sintering (SLS)

SLS has some similarities with Stereolithography.  However, SLS makes use of powdered material that is placed in a vat. For each layer, a layer of powdered material is placed on top of the previous layer using a roller and then the powdered material is laser sintered according to a certain pattern for building up the object to be created.    Interestingly, the portion of the powdered material that is not sintered can be used to provide the support structure and this material can be removed after the object is formed for re-use1.

Selective Laser Sintering Process

Selective Laser Melting (SLM)

The SLM process is very similar to the SLS process.  However, unlike the SLS process where the powdered material is sintered the SLM process involves fully melting the powdered material1.

Electronic Beam Melting (EBM)

This technology is also much like SLM. However, it makes use of an electron beam instead of a high-powered laser1.  The electron beam fully melts a metal powder to form the desired object.   The process is slower and more expensive than for SLM with a greater limitation on the available materials.

Laminated Object Manufacturing (LOM)

This is a rapid prototyping system. In this process, layers of material coated with adhesive are fused together with heat and pressure and then cut into shape using a laser cutter or knife1,2.     More specifically, a foil coated with adhesive is overlaid on the previous layer and a heated roller heats the adhesive for adhesion between the two layers.  Layers can be made of paper, plastic or metal laminates1. The process can include post-processing steps that include machining and drilling.  This is a fast and inexpensive method of 3D printing1.  With the use of an adhesion process, no chemical process is necessary and relatively large parts can be made2.

Laminated Object Manufacturing
Source: http://www.livescience.com/40310-laminated-object-manufacturing.html

References Used:

  1. http://3dprintingfromscratch.com/common/types-of-3d-printers-or-3d-printing-technologies-overview/
  2. https://en.wikipedia.org/wiki/Laminated_object_manufacturing
  3. https://en.wikipedia.org/wiki/Stereolithography



Types of 3D Printing Technology Explained

Multi Jet Fusion (MJF)

Similar to SLS, Multi Jet Fusion also builds functional parts from nylon powder. Rather than using a laser to sinter the powder, MJF uses an inkjet array to apply fusing agents to the bed of nylon powder. Then a heating element passes over the bed to fuse each layer. This results in more consistent mechanical properties compared to SLS as well as improved surface finish. Another benefit of the MJF process is the accelerated build time, which leads to lower production costs.

Fused Deposition Modeling (FDM)

Fused deposition modeling (FDM) is a common desktop 3D printing technology for plastic parts. An FDM printer functions by extruding a plastic filament layer-by-layer onto the build platform. It’s a cost-effective and quick method for producing physical models. There are some instances when FDM can be used for functional testing but the technology is limited due to parts having relatively rough surface finishes and lacking strength.

Metal 3D Printing Processes

Direct Metal Laser Sintering (DMLS)

Metal 3D printing opens up new possibilities for metal part design. The process we use at Protolabs to 3D print metal parts is direct metal laser sintering (DMLS). It’s often used to reduce metal, multi-part assemblies into a single component or lightweight parts with internal channels or hollowed out features. DMLS is viable for both prototyping and production since parts are as dense as those produced with traditional metal manufacturing methods like machining or casting. Creating metal components with complex geometries also makes it suitable for medical applications where a part design must mimic an organic structure.

Electron Beam Melting (EBM)

Electron beam melting is another metal 3D printing technology that uses an electron beam that's controlled by electromagnetic coils to melt the metal powder. The printing bed is heated up and in vacuum conditions during the build. The temperature that the material is heated to is determined by the material in use. 

When to Use 3D Printing

As stated earlier, there are a couple common denominators among 3D printing applications. If your part quantities are relatively low, 3D printing can be optimal—the guidance we give our 3D printing service customers is usually 1 to 50 parts. As volumes start to near the hundreds, it’s worth exploring other manufacturing processes. If your design features complex geometry that is critical to your part’s function, like an aluminum component with an internal cooling channel, 3D printing might be your only option.

Selecting the right process comes down to aligning the advantages and limitations of each technology to your application’s most important requirements. In the early stages when ideas are being thrown around and all you need is a model to share with a colleague, those stair-stepping surface finishes on your part aren’t of much concern. But once you hit the point where you need to conduct user testing, factors like cosmetics and durability start to matter. Although there is no one-size-fits-all solution, properly utilizing 3D printing technology throughout product development will reduce design risk and, ultimately, result in better products.

Technologies and methods of 3D printing - ANRO technology

The active introduction of 3D technologies contributed to the creation of progressive 3D printers with a rich set of options. 's high-performance 3 D-printing technologies have produced original designs for marketing, catering, industry and landscaping.

3D printing is a procedure for designing three-dimensional compositions of a given geometric shape. The process of obtaining the original model is based on the phased construction of the object with clear applied layers, clearly demonstrating the edges of the product.

Innovative 3D printing methods are in high demand in the construction industry, architecture, education, medicine, bioengineering and many other fields. Unlike traditional methods of obtaining parts - milling, turning, they allow you to achieve high accuracy, the greatest savings in materials and time.

Features of 3D printing

Designed models are reproduced using special computer graphics programs , which are designed specifically for this purpose. Building one model can take from a couple of hours to two or more days, depending on the specifics of the project. The desktop device allows designers and design professionals to turn original prototypes into reality.

The advantage of modern technology is the efficiency and cost-effectiveness of modeling objects, for example, in the manufacture of products in production. 3D printers are indispensable for creating unique products in preschool educational institutions, building more complex samples in schools and specialized institutions. Modern technologies make it much easier to work with 3D models, so this technology becomes accessible to children. 3D modeling allows you to create objects of unique geometric shapes of varying degrees of complexity.

Basic 3D printing

  • Fused deposition prototyping (FDM). An accessible modeling method, which consists in the layer-by-layer application of a hot thread from a fusible working product (wax, metal, plastic). Most often used for rapid prototyping of various models, for example, mass production of jewelry, souvenirs and toys;
  • Selective Laser Sintering (SLS). One of the famous prototyping methods. The product is formed from a powder product (ceramics, metal-plastic) by melting under the influence of a laser. The advantage of SLS is that you don't have to use a special structure to support floating elements;
  • Laser stereolithography (SLA). The most famous modeling method using a special liquid polymer that hardens under the influence of mercury radiation. The advantages include high print resolution, the least amount of waste and ease of finishing the product;
  • Electron Beam Melting (EBM). Advanced adaptive manufacturing method using special electron beams. Widely used in the production of various titanium products. Unlike models produced by SLS, blanks are solid and highly durable;
  • Production of models using lamination (LOM). Progressive way of forming various models using layer-by-layer gluing. The resulting objects can be upgraded by machining. The advantage of this technology is the availability of the main consumable material - paper;
  • Multi-jet simulation (MJM). A popular type of printing based on multi-jet modeling of a photopolymer product. It is used in various industries. The advantages include the possibility of multi-color printing and the interaction of materials of different properties and characteristics.

Other 3D modeling technologies are common in adaptive and industrial manufacturing. All of them have their own characteristics and nuances. However, the simplest and most popular 3 D-printing method for is Fused Deposition Modeling (FDM).

3 reasons to choose FDM technology

  • Simplicity. Printing technology is accessible even to small children. Therefore, it can be used both in schools and offices, and in preschool institutions;
  • Originality. FDM technology allows you to design objects with unusual geometry and cavities, which is beyond the power of other types of modeling;
  • Variety. When working with FDM technology, a wide variety of plastics can be used, which makes it possible to obtain a fairly wide range of models with different physical and chemical properties. 3D objects can be durable, flexible, luminous, soluble in water, and with many other properties.

FDM technology uses time-tested thermoplastics that are used in traditional manufacturing of various products.

Advantages of modern 3D printing technology from ANRO-technology

  • High speed. Modern technologies provide short terms of product prototype development;
  • Minimum material consumption. Progressive 3D printers allow you to produce objects with the lowest waste rates;
  • Robust internal structure. Innovative devices help to design large objects with minimal weight;
  • Environmentally friendly. The materials used in prototyping are completely safe and do not pose any harm to the user.

Additional advantages of creating a 3D object include durable and convenient storage of materials that does not require special conditions.

3D technology is the future of prototyping, because thanks to them today the most non-standard design projects are being implemented both in everyday life and in the industrial sphere.

Our company is engaged in the development and supply of 3D printers based on FDM technology. Our 3D printers with specialized software are suitable for children from 6 years old. Small 3D prints can fit at home and delight children and adults with the opportunity to print their own 3D models of objects and toys.

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3D printing for dummies or "what is a 3D printer?"

  • 1 3D printing term
  • 2 3D printing methods
    • 2. 1 Extrusion printing
    • 2.2 Melting, sintering or gluing
    • 2.3 Stereolithography
    • 2.4 Lamination
  • 3 Fused Deposition Printing (FDM)
    • 3.1 Consumables
    • 3.2 Extruder
    • 3.3 Working platform
    • 3.4 Positioners
    • 3.5 Control
    • 3.6 Types of FDM printers
  • 4 Laser stereolithography (SLA)
    • 4.1 Lasers and projectors
    • 4.2 Cuvette and resin
    • 4.3 Types of stereolithographic printers

The term 3D printing

The term 3D printing has several synonyms, one of which quite briefly and accurately characterizes the essence of the process - "additive manufacturing", that is, production by adding material. The term was not coined by chance, because this is the main difference between multiple 3D printing technologies and the usual methods of industrial production, which in turn received the name "subtractive technologies", that is, "subtractive". If during milling, grinding, cutting and other similar procedures, excess material is removed from the workpiece, then in the case of additive manufacturing, material is gradually added until a solid model is obtained.

Soon 3D printing will even be tested on the International Space Station

Strictly speaking, many traditional methods could be classified as "additive" in the broad sense of the word - for example, casting or riveting. However, it should be borne in mind that in these cases, either the consumption of materials is required for the manufacture of specific tools used in the production of specific parts (as in the case of casting), or the whole process is reduced to joining ready-made parts (welding, riveting, etc.). In order for the technology to be classified as “3D printing”, the final product must be built from raw materials, not blanks, and the formation of objects must be arbitrary - that is, without the use of forms. The latter means that additive manufacturing requires a software component. Roughly speaking, additive manufacturing requires computer control so that the shape of final products can be determined by building digital models. It was this factor that delayed the widespread adoption of 3D printing until the moment when numerical control and 3D design became widely available and highly productive.

3D printing techniques

There are a lot of 3D printing technologies, and even more names for them due to patent restrictions. However, you can try to divide technologies into main areas:

Extrusion printing

This includes methods such as deposition fusion (FDM) and multi-jet printing (MJM). This method is based on the extrusion (extrusion) of consumables with the sequential formation of the finished product. As a rule, consumables consist of thermoplastics or composite materials based on them.

Melting, sintering or bonding

This approach is based on bonding powdered material together. Formation is done in different ways. The simplest is gluing, as is the case with 3D inkjet printing (3DP). Such printers deposit thin layers of powder onto the build platform, which are then selectively bonded with a binder. Powders can be made up of virtually any material that can be ground to a powder—plastic, wood, metal.

This model of James Bond's Aston Martin was successfully printed on a Voxeljet SLS printer and blown up just as successfully during the filming of Skyfall instead of the expensive original

sintering (SLS and DMLS) and smelting (SLM), which allow you to create all-metal parts. As with 3D inkjet printing, these devices apply thin layers of powder, but the material is not glued together, but sintered or melted using a laser. Laser sintering (SLS) is used to work with both plastic and metal powders, although metal pellets usually have a more fusible shell, and after printing they are additionally sintered in special ovens. DMLS is a variant of SLS installations with more powerful lasers that allow sintering metal powders directly without additives. SLM printers provide not just sintering of particles, but their complete melting, which allows you to create monolithic models that do not suffer from the relative fragility caused by the porosity of the structure. As a rule, printers for working with metal powders are equipped with vacuum working chambers, or they replace air with inert gases. Such a complication of the design is caused by the need to work with metals and alloys subject to oxidation - for example, with titanium.

Stereolithography

How an SLA printer works

Stereolithography printers use special liquid materials called "photopolymer resins". The term "photopolymerization" refers to the ability of a material to harden when exposed to light. As a rule, such materials react to ultraviolet irradiation.

Resin is poured into a special container with a movable platform, which is installed in a position near the surface of the liquid. The layer of resin covering the platform corresponds to one layer of the digital model. Then a thin layer of resin is processed by a laser beam, hardening at the points of contact. At the end of illumination, the platform together with the finished layer is immersed to the thickness of the next layer, and illumination is performed again.

Lamination

Laminating (LOM) 3D printers

Some 3D printers build models using sheet materials - paper, foil, plastic film.

Layers of material are glued on top of each other and cut along the contours of the digital model using a laser or a blade.

These machines are well suited for prototyping and can use very cheap consumables, including regular office paper. However, the complexity and noise of these printers, coupled with the limitations of the models they produce, limit their popularity.

Fused deposition modeling (FDM) and laser stereolithography (SLA) have become the most popular 3D printing methods used in the home and office.

Let's take a closer look at these technologies.

Fused Deposition Printing (FDM)

FDM is perhaps the simplest and most affordable 3D construction method, which is the reason for its high popularity.
High demand for FDM printers is driving device and consumable prices down rapidly, along with technology advances towards ease of use and improved reliability.

Consumables

ABS filament spool and finished model

FDM printers are designed to print with thermoplastics, which are usually supplied as thin filaments wound on spools. The range of "clean" plastics is very wide. One of the most popular materials is polylactide or "PLA plastic". This material is made from corn or sugar cane, which makes it non-toxic and environmentally friendly, but makes it relatively short-lived. ABS plastic, on the other hand, is very durable and wear-resistant, although it is susceptible to direct sunlight and can release small amounts of harmful fumes when heated. Many plastic items that we use on a daily basis are made from this material: housings for household appliances, plumbing fixtures, plastic cards, toys, etc.

In addition to PLA and ABS, printing is possible with nylon, polycarbonate, polyethylene and many other thermoplastics that are widely used in modern industry. More exotic materials are also possible, such as polyvinyl alcohol, known as "PVA plastic". This material dissolves in water, which makes it very useful for printing complex geometric patterns. But more on that below.

Model made from Laywoo-D3. Changing the extrusion temperature allows you to achieve different shades and simulate annual rings

It is not necessary to print with homogeneous plastics. It is also possible to use composite materials imitating wood, metals, stone. Such materials use all the same thermoplastics, but with impurities of non-plastic materials.

So, Laywoo-D3 consists partly of natural wood dust, which allows you to print "wooden" products, including furniture.

The material called BronzeFill is filled with real bronze, and models made from it can be ground and polished, achieving a high similarity to products made from pure bronze.

One has only to remember that thermoplastics serve as a binding element in composite materials - they determine the thresholds of strength, thermal stability and other physical and chemical properties of finished models.

Extruder

Extruder - FDM print head. Strictly speaking, this is not entirely true, because the head consists of several parts, of which only the feed mechanism is directly "extruder". However, by tradition, the term "extruder" is commonly used as a synonym for the entire print assembly.

FDM extruder general design

The extruder is designed for melting and applying thermoplastic thread. The first component is the thread feed mechanism, which consists of rollers and gears driven by an electric motor. The mechanism feeds the thread into a special heated metal tube with a small diameter nozzle, called a "hot end" or simply a "nozzle". The same mechanism is used to remove the thread if a change of material is needed.

The hot end is used to heat and melt the thread fed by the puller. As a rule, nozzles are made from brass or aluminum, although more heat-resistant, but also more expensive materials can be used. For printing with the most popular plastics, a brass nozzle is quite enough. The “nozzle” itself is attached to the end of the tube with a threaded connection and can be replaced with a new one in case of wear or if a change in diameter is necessary. The nozzle diameter determines the thickness of the molten filament and, as a result, affects the print resolution. The heating of the hot end is controlled by a thermistor. Temperature control is very important, because when the material is overheated, pyrolysis can occur, that is, the decomposition of plastic, which contributes both to the loss of the properties of the material itself and to clogging of the nozzle.

PrintBox3D One FDM Printer Extruder

To prevent the filament from melting too early, the top of the hot end is cooled by heatsinks and fans. This point is of great importance, since thermoplastics that pass the glass transition temperature significantly expand in volume and increase the friction of the material with the walls of the hot end. If the length of such a section is too long, the pulling mechanism may not have enough strength to push the thread.

The number of extruders may vary depending on the purpose of the 3D printer. The simplest options use a single print head. The dual extruder greatly expands the capabilities of the device, allowing you to print one model in two different colors, as well as using different materials. The last point is important when building complex models with overhanging structural elements: FDM printers cannot print “over the air”, since the applied layers require support. In the case of hinged elements, temporary support structures have to be printed, which are removed after printing is completed. The removal process is fraught with damage to the model itself and requires accuracy. In addition, if the model has a complex structure with internal cavities that are difficult to access, building conventional supports may not be practical due to the difficulty in removing excess material.

Finished model with PVA supports (white) before and after washing

In such cases, the very water-soluble polyvinyl alcohol (PVA) comes in handy. Using a dual extruder, you can build a model from waterproof thermoplastic using PVA to create supports.

After printing, PVA can be simply dissolved in water and a complex product of perfect quality can be obtained.

Some FDM printers can use three or even four extruders.

Work platform

Heated platform covered with removable glass work table

Models are built on a special platform, often equipped with heating elements. Preheating is required for a wide range of plastics, including the popular ABS, which are subject to a high degree of shrinkage when cooled. The rapid loss of volume by cold coats compared to freshly applied material can lead to model distortion or delamination. The heating of the platform makes it possible to significantly equalize the temperature gradient between the upper and lower layers.

Heating is not recommended for some materials. A typical example is PLA plastic, which requires a fairly long time to harden. Heating PLA can lead to deformation of the lower layers under the weight of the upper ones. When working with PLA, measures are usually taken not to heat up, but to cool the model. Such printers have characteristic open cases and additional fans blowing fresh layers of the model.

Calibration screw for work platform covered with blue masking tape

The platform needs to be calibrated before printing to ensure that the nozzle does not hit the applied layers and move too far causing air-to-air printing resulting in plastic vermicelli. The calibration process can be either manual or automatic. In manual mode, calibration is performed by positioning the nozzle at different points on the platform and adjusting the platform inclination using the support screws to achieve the optimal distance between the surface and the nozzle.

As a rule, platforms are equipped with an additional element - a removable table. This design simplifies the cleaning of the working surface and facilitates the removal of the finished model. Stages are made from various materials, including aluminum, acrylic, glass, etc. The choice of material for the manufacture of the stage depends on the presence of heating and consumables for which the printer is optimized.

For a better adhesion of the first layer of the model to the surface of the table, additional tools are often used, including polyimide film, glue and even hairspray! But the most popular tool is inexpensive, but effective masking tape. Some manufacturers make perforated tables that hold the model well but are difficult to clean. In general, the expediency of applying additional funds to the table depends on the consumable material and the material of the table itself.

Positioning mechanisms

Scheme of operation of positioning mechanisms

Of course, the print head must move relative to the working platform, and unlike conventional office printers, positioning must be carried out not in two, but in three planes, including height adjustment.

Positioning pattern may vary. The simplest and most common option involves mounting the print head on perpendicular guides driven by stepper motors and providing positioning along the X and Y axes.

Vertical positioning is carried out by moving the working platform.

On the other hand, it is possible to move the extruder in one plane and the platforms in two.

SeemeCNC ORION Delta Printer

One option that is gaining popularity is the delta coordinate system.

Such devices are called "delta robots" in the industry.

In delta printers, the print head is suspended on three manipulators, each of which moves along a vertical rail.

The synchronous symmetrical movement of the manipulators allows you to change the height of the extruder above the platform, and the asymmetric movement causes the head to move in the horizontal plane.

A variant of this system is the reverse delta design, where the extruder is fixed to the ceiling of the working chamber, and the platform moves on three support arms.

Delta printers have a cylindrical build area, and their design makes it easy to increase the height of the working area with minimal design changes by extending the rails.

In the end, everything depends on the decision of the designers, but the fundamental principle does not change.

Control

Typical Arduino-based controller with add-on modules

FDM printer operation, including nozzle and platform temperature, filament feed rate, and stepper motors for positioning the extruder, is controlled by fairly simple electronic controllers. Most controllers are based on the Arduino platform, which has an open architecture.

The programming language used by printers is called G-code (G-Code) and consists of a list of commands executed in turn by the 3D printer systems. G-code is compiled by programs called "slicers" - standard 3D printer software that combines some of the features of graphics editors with the ability to set print options through a graphical interface. The choice of slicer depends on the printer model. RepRap printers use open source slicers such as Skeinforge, Replicator G and Repetier-Host. Some companies make printers that require proprietary software.

Program code for printing is generated using slicers

As an example, we can mention Cube printers from 3D Systems. There are companies that offer proprietary software but allow third-party software, as is the case with the latest generation of MakerBot 3D printers.

Slicers are not intended for 3D design per se. This task is done with CAD editors and requires some 3D design skills. Although beginners should not despair: digital models of a wide variety of designs are offered on many sites, often even for free. Finally, some companies and individuals offer 3D design services for custom printing.

Finally, 3D printers can be used in conjunction with 3D scanners to automate the process of digitizing objects. Many of these devices are designed specifically to work with 3D printers. Notable examples include the 3D Systems Sense handheld scanner and the MakerBot Digitizer handheld desktop scanner.

MakerBot Replicator 5th Generation FDM Printer with built-in control module on the top of the frame

The 3D printer user interface can consist of a simple USB port for connecting to a personal computer. In such cases, the device is actually controlled by the slicer.

The disadvantage of this simplification is a rather high probability of printing failure when the computer freezes or slows down.

A more advanced option includes an internal memory or memory card interface to make the process standalone.

These models are equipped with control modules that allow you to adjust many print parameters (such as print speed or extrusion temperature). The module may include a small LCD display or even a mini-tablet.

Varieties of FDM printers

Stratasys Fortus 360mc professional FDM printer that allows printing with nylon

FDM printers are very, very diverse, ranging from the simplest home-made RepRap printers to industrial installations capable of printing large-sized objects.

Stratasys, founded by Scott Crump, the inventor of FDM technology, is a leader in the production of industrial installations.

You can build the simplest FDM printers yourself. Such devices are called RepRap, where "Rep" indicates the possibility of "replication", that is, self-reproduction.

RepRap printers can be used to print custom built plastic parts.

Controller, rails, belts, motors and other components can be easily purchased separately.

Of course, assembling such a device on your own requires serious technical and even engineering skills.

Some manufacturers make it easy by selling DIY kits, but these kits still require a good understanding of the technology. RepRap Printers

And, despite their "home-made nature", RepRap printers are quite capable of producing models with quality at the level of expensive branded counterparts.

Ordinary users who do not want to delve into the intricacies of the process, but require only a convenient device for household use, can purchase a ready-made FDM printer.

Many companies focus on the development of the consumer market segment, offering 3D printers for sale that are ready to print "straight out of the box" and do not require serious computer skills.

3D Systems Cube consumer 3D printer

The most famous example of a consumer 3D printer is the 3D Systems Cube.

While it doesn't boast a huge build area, ultra-fast print speed, or unsurpassed model build quality, it's easy to use, affordable, and safe: This printer has received the necessary certification to be used even by children.

Mankati FDM printer demonstration: http://youtu.be/51rypJIK4y0

Laser Stereolithography (SLA)

Stereolithographic 3D printers are widely used in dental prosthetics

Stereolithographic printers are the second most popular and widespread after FDM printers.

These units deliver exceptional print quality.

The resolution of some SLA printers is measured in a matter of microns - it is not surprising that these devices quickly won the love of jewelers and dentists.

The software side of laser stereolithography is almost identical to FDM printing, so we will not repeat ourselves and will only touch on the distinctive features of the technology.

Lasers and projectors

Projector illumination of a photopolymer model using Kudo3D Titan DLP printer as an example

The cost of stereolithography printers is rapidly declining, due to growing competition due to high demand and the use of new technologies that reduce the cost of construction.

Although the technology is generically referred to as "laser" stereolithography, most recent developments use UV LED projectors for the most part.

Projectors are cheaper and more reliable than lasers, do not require the use of delicate mirrors to deflect the laser beam, and have higher performance. The latter is explained by the fact that the contour of the whole layer is illuminated as a whole, and not sequentially, point by point, as is the case with laser options. This variant of the technology is called projection stereolithography, "DLP-SLA" or simply "DLP". However, both options are currently common - both laser and projector versions.

Cuvette and resin

Photopolymer resin is poured into the cuvette

A photopolymer resin that looks like epoxy is used as consumables for stereolithography printers. Resins can have a variety of characteristics, but they all share one key feature for 3D printing applications: these materials harden when exposed to ultraviolet light. Hence, in fact, the name "photopolymer".

When polymerized, resins can have a wide variety of physical characteristics. Some resins are like rubber, others are hard plastics like ABS. You can choose different colors and degrees of transparency. The main disadvantage of resins and SLA printing in general is the cost of consumables, which significantly exceeds the cost of thermoplastics.

On the other hand, stereolithographic printers are mainly used by jewelers and dentists who do not need to build large parts but appreciate the savings from fast and accurate prototyping. Thus, SLA printers and consumables pay for themselves very quickly.

An example of a model printed on a laser stereolithographic 3D printer

Resin is poured into a cuvette, which can be equipped with a lowering platform. In this case, the printer uses a leveling device to flatten the thin layer of resin covering the platform just prior to irradiation. As the model is being made, the platform, together with the finished layers, is “embedded” in the resin. Upon completion of printing, the model is removed from the cuvette, treated with a special solution to remove liquid resin residues and placed in an ultraviolet oven, where the final illumination of the model is performed.

Some SLA and DLP printers work in an "inverted" scheme: the model is not immersed in the consumable, but "pulled" out of it, while the laser or projector is placed under the cuvette, and not above it. This approach eliminates the need to level the surface after each exposure, but requires the use of a cuvette made of a material transparent to ultraviolet light, such as quartz glass.

The accuracy of stereolithographic printers is extremely high. For comparison, the standard for vertical resolution for FDM printers is considered to be 100 microns, and some variants of SLA printers allow you to apply layers as thin as 15 microns. But this is not the limit. The problem, rather, is not so much in the accuracy of lasers, but in the speed of the process: the higher the resolution, the lower the print speed. The use of digital projectors allows you to significantly speed up the process, because each layer is illuminated entirely. As a result, some DLP printer manufacturers claim to be able to print with a vertical resolution of one micron!

Video from CES 2013 showing Formlabs Form1 stereolithography 3D printer in action: http://youtu.be/IjaUasw64VE

Stereolithography Printer Options

Formlabs Form1 Desktop Stereolithography Printer

As with FDM printers, SLA printers come in a wide range in terms of size, features and cost.

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