3D Printers and 3D Printing: Technologies, Processes and Techniques

3D printing  is also called additive manufacturing. This term accurately describes how this technology works to create objects. "Additive" refers to the successive addition of  thin layers between 16 to 180 microns or more  to create an object. In fact, all 3D printing technologies are similar, as they construct an object layer by layer to create complex shapes.


How does 3D Printing Work ?


There are 3 main steps in 3D printing.

The first step  is the preparation just before printing, when you design a 3D file  of the object you want to print.  This 3D file can be created using CAD software , with a 3D scanner  or simply downloaded from an online marketplace. Once you have checked that your 3D file is ready to be printed , you can proceed to the second step.

The second step  is the actual printing process.  First, you need to choose which material will best achieve the specific properties required for your object. The variety of materials used in 3D printing is very broad. It includes plastics, ceramics, resins, metals, sand, textiles, biomaterials, glass, food and even lunar dust! Most of these materials also allow for  plenty of finishing options that enable you to achieve the precise design result you had in mind, and some others, like glass for example, are still being developed as 3D printing material and are not easily accessible yet.

The third step is the finishing process. This step requires specific skills and materials. When the object is first printed, often it cannot be directly used or delivered until it has been sanded, lacquered or painted to complete it as intended.

The material chosen for the project will determine which printing methods are most suitable. Among these, the most commonly used techniques for each group of materials are described next. 

If you want to use Plastic or Alumide



  • Fused Deposition Modeling (FDM) Technology: is at the very entry of the market as it mainly used by individuals. It is probably the most popular printing method due to the number of printers available on the market. FDM is an affordable 3D printing process compared to other 3D printing technologies. This process works by material being melted and extruded through a nozzle to 3D print a cross section of an object each layer at a time. The bed lowers for each new layer and this process repeats until the object is completed. Layer thickness determines the quality of the 3D print. Some FDM 3D printers have two or more print heads to print in multiple colours and use support for overhanging areas of a complex 3D print.


  • SLS Technology : Laser sintering is a 3D printing technique consisting of the fabrication of an object by melting successive layers of powder together in order to form an object. The process most notably facilitates in the creation of complex and interlocking forms. It is available for Plastic and Alumide .


If you want to compare these two technologies in order to find the best suited for you, have a look to our showdown FDM vs. SLS.

If you want to use Resin or Wax

PolyJet and MultiJet

The technology you will need is the photopolymerisation , a technique that involves the solidification of photo-sensitive resin by means of a UV light. It is used by different 3D printing processes such as:


  • Stereolithography (SLA): uses a vat of curable photopolymer resin. The build plate descends in small increments and the liquid polymer is exposed to light where the UV laser draws a cross section layer by layer. The process is repeated until a model has been created. The object is 3D printed by pulling the object out of the resin (bottom up), which creates space for the uncured resin at the bottom of the container and can then form the next layer of the object. Another method is to 3D print the object by pulling it downward into the tank with the next layer being cured on the top.


  • Digital Light Processing (DLP)  a projector is used to cure photopolymer resin. This is very similar to the SLA method except that instead of using a UV laser to cure the photopolymer resin, a safelight (light bulb) is used. Objects are created similarly to SLA with the object being either pulled out of the resin, which creates space for the uncured resin at the bottom of the container thus forming the next layer of the object, or down into the tank with the next layer being cured at the top. 
    Sculpteo uses DLP technology for Silver and Brass 3D printing. We 3D print a wax model first then, we use a lost-wax casting technique: a mould is made around the wax before it is melted and filled with silver, creating your object.

  • Continuous Liquid Interface Production (CLIP) works by projecting a continuous sequence of UV images, generated by a digital light projector, through an oxygen-permeable, UV-transparent window below a liquid resin bath. The dead zone created above the window maintains a liquid interface below the part. Above the dead zone, the curing part is drawn out of the resin bath.


  • MultiJet printers : Similar to Stereolithography, the high-quality PolyJet and MultiJet 3D printing processes use a UV light to crosslink a photopolymer. However, rather than scanning a laser to cure layers, a printer jet sprays tiny droplets of the photopolymer (similar to ink in an inkjet printer) in the shape of the first layer. The UV lamp attached to the printer head crosslinks the polymer and locks the shape of the layer in place. The build platform then descends by one layer thickness, and more material is deposited directly onto the previous layer.


If you want to use Metal

  • DLP combined with the lost-wax casting technique allows objects to be printed in 3D. Sculpteo uses DLP technology for  Silver  and  Brass  3D prints. First, we 3D print a wax model. Then, we use a lost-wax casting technique: a mould is made around the wax before it is melted and filled with silver, thus creating your object.


  • Direct Metal Laser Sintering (DMLS) uses a laser as a power source in order to sinter metal powder by aiming a laser and tracing a cross section of the object layer by layer. Direct Metal Laser SIntering is similar to the selective laser sintering process.


  • Electron Beam Melting (EBM)  uses an electron beam as the power source instead of a laser to 3D print metal. An electron beam melts metal powder layer by layer within a high vacuum and can achieve full melting of the metal powder. This method can produce high-density metal parts thus retaining the material's properties.


If you want to use Multicolor




  • Binder Jetting is popular since you can create detailed 3D prints with colour. An automated roller is used to spread a layer of powder onto the build platform. Excess powder is pushed to the sides and ensures that the bed is filled with a layer of packed powder. On a fast axis, the print heads apply a liquid binder and colour simultaneously to create a cross section of the object on the powder.


  • Selective Deposition Lamination is a 3D printing process using paper. This process is similar to Laminated Object Manufacturing (LOM) rapid prototyping method. The process involves layers of adhesive coated paper (or plastic or metal laminates) that are successively glued together with a heated roller and cut to shape with a laser cutter layer by layer. A roller with the material moves each new sheet of material over the last and repeats the process until the object is completed.


  • Triple-jetting technology (PolyJet) used in Stratasys Objet500 Connex3, is the most advanced method of PolyJet 3D printing. This technology performs precise printing with three materials and thus makes three-colour mixing possible. To know more about this technology, you can refer to PolyJet & Multijet


3D Printing Technologies Comparison

Technology Additive Manufacturing Process Advantages Disadvantages Plastic based material Metal or Brass Resin  Multicolour
Fused Deposition Modelling Material Extrusion Strong Parts
Easy to print yourself
Poorer surface finish and slower
Requires support structures
Yes
Selective Laser Sintering Powder Bed Fusion No support required
High Heat and Chemical Resistant
High speed
Precision limited to powder particle size
Rough surface finish
Yes
Direct Metal Laser Sintering Powder Bed Fusion High-density components
Intricateness
Finishing step is a mandatory Yes
Electron Beam Melting Powder Bed Fusion Good printing speed
Less distortion
Needs finishing
Caution required when dealing with X-Ray
Yes
Stereolithography Photopoly- merisation Complex Geometries
Detailed parts
Smooth Finish
Post-finishing required
Requires Support structures
Yes
Digital Light Processing Photopoly- merisation Concurrent production
Complex shapes and sizes
High precision
Thickness limitation
Limited range of materials
Yes
Continuous Liquid Interface Production Photopoly- merisation Concurrent production
Complex shapes and sizes
High precision
Thickness limitation
Large choice of resins simulating different properties
Yes
Multijet et Polyjet Material Jetting Good precision
Good surface finish
Use of multiple materials and colours
No removal of support material
Slow Build Process Yes Yes
Binder Jetting Jetting Lower Price
Enables colour printing
High speed
Limited choice of materials
Fragile parts
Yes
Selective Deposition Lamination Sheet Lamination Lower Price
No toxic materials
Quick to make large parts
Less accurate
Non-Homogenous parts
Yes

Conclusion

The list of 3D printing technologies and processes continues to grow as 3D printing is always changing. The 3D printing industry continues to innovate its hardware as well as the materials and processes to create objects or parts. Depending on many factors such as budget, design or function, choosing the appropriate 3D printing process as well as the right material is important. 3D printing can create many different 3D printed objects that were previously only fabricated through mass manufacturing methods.

An online 3D printing service like Sculpteo exists due to the complexity, time and skills required for the Printing and Finishing steps. This complexity may hinder people from using this wonderful technology, but at Sculpteo we apply our knowledge to serve anyone willing to try 3D printing, as we want to broaden access to additive manufacturing technology.




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