3D Printing is a dynamic and ever-changing universe and understanding it in depth requires constant effort. As industry professionals, we are aware that the complexity of technologies, materials and processes makes it crucial to understand the main concepts and adapt to emerging innovations and challenges. In this context, constant updating and knowledge exchange are fundamental pillars to contribute to the application and development of 3D printing.

We thought it would be useful to bring together the now rich vocabulary of 3D Printing to provide an accessible overview for anyone interested in learning more about this subject. To make it easier to understand and use, the collection is organised into four distinct parts, each focusing on a broad subject area:

  • #1 Additive Manufacturing and 3D Printing Technologies: the first instalment explores the various additive manufacturing technologies, attempting to bring order to the many existing acronyms and offering a detailed perspective on the methods used to create three-dimensional objects;
  • #2 3D printers: in the second episode, we take a detailed look at the different types of 3D printers, with a guide to understanding their operation and features;
  • #3 Materials: the third issue focuses on the materials used in the 3D printing process, their properties, applications and performance depending on the type of use;
  • #4 3D Printing Software and Files: we conclude with an analysis of the software and file formats used in the 3D preparation and printing process, with useful hints on how to manage and optimise designs for printing.

The contents are constantly evolving and being supplemented. If you too would like to contribute, please write to hello@polyd.com 

 

PolyD, Additive Manufacturing

 

ADDITIVE MANUFACTURING & 3D PRINTING TECHNOLOGIES

Let us begin by distinguishing the two approaches to creating complex, functional parts:

  • Additive Manufacturing;
  • CNC Manufacturing.

Both technologies are used to generate Prototypes and Objects. The approach differs in the way the material is manipulated: additive manufacturing adds material to build the object, while CNC manufacturing removes material to achieve the desired shape.

 

CNC Manufacturing

 

Now that we understand what the concept of CNC manufacturing is, here are some examples:

  • CNC milling (Computer Numerical Control): a computer-controlled rotary cutter removes material from a solid block and creates objects and components;
  • CNC turning: the lathe rotates and cuts the workpiece, removing excess material to obtain the desired shape;
  • Laser cutting: the focused laser beam cuts materials such as metal, plastic or wood;
  • Wire EDM: a thin metal wire and an electrical erosion action remove material from a solid object, creating parts with tight tolerances and precise surfaces;
  • Ultrasonic Machining: a vibrating ultrasonic tool removes material from the workpiece. This technique is mainly used for ceramics or glass;
  • Chemical Machining: chemicals carry material away from a solid surface, e.g. through selective corrosion or etching processes;
  • Sandblasting: excess material is removed with a high-pressure jet of sand. This technique is also often used to clean or polish metal and plastic surfaces;
  • Traditional Machining: this category includes a wide range of subtractive machining techniques involving the use of hand or machine tools, such as parting-off, shaping, filing and sanding.

 

Additive Manufacturing

 

3D Printing (3D Printing) today uses the following terms in common parlance - indifferently: Rapid Manufacturing (Rapid Manufacturing), Additive Manufacturing (Additive Manufacturing), Layer Manufacturing (Layer Manufacturing).

The concept of 3D printing was registered by Stratasys, which brought it into public use in 1999. Additive Manufacturing is today used synonymously with 3D Printing and includes all Technologies that produce Components, Prototypes, Parts or Semi-finished products by adding material layer by layer, based on a 3D file or Model.

Additive machining considers 5 stages:

  • the creation of the model;
  • the generation of the stl file (for conversion read .step converter to .stl);
  • the definition of the necessary layers;
  • the actual production;
  • the finishing processes of the Part or Component.

Additive Manufacturing employs Additive Technologies that have several Advantages:

  • they use a variety of materials, including plastics, metal, ceramics and composite materials;
  • they offer greater design freedom and allow the creation of complex geometries and internal structures;
  • they generally produce less material waste than subtractive technologies.

For the purpose of a basic classification of Additive Technologies, we refer to the ISO Standards that establish and define the terminology of Additive Manufacturing, dividing the techniques into 7 main macro categories:

  • Material Extrusion: is perhaps the best known, thanks to the printers on the market today. The print head heats the filament and deposits it layer upon layer. Examples of this category are FDM or FFF.
  • Vat Photopolymerisation (Photopolymerisation in a Vat): printing takes place in a vat/tub with a light-activated reactive liquid inside, which breaks chemical bonds in the liquid, releases radicals and makes them react with the short chains of the surrounding polymers. The category includes 3SP, CLIP, DPL, SLA, etc.;
  • Power Bed Fusion (Powder Bed Fusion): a laser or electron beam melts or sinters powder, applied layer upon layer. Here we find for example DMP, DMLS, SLM, SLS.
  • Binder Jetting: uses an inkjet-type printer. The layers of powder deposited on the platen are bonded to successive layers by means of a binder. This process is repeated layer by layer until the desired object is formed. When the part is completely printed, the excess powder is removed. Binden Jetting, MBJ, SBI fall into this category.
  • Sheet Lamination: sheets of material such as plastic, paper or sheet metal are glued in layers and the excess material is cut off with a laser or knife. The category includes among others SDL, LOM.
  • Directed Energy Deposition: this is reminiscent of welding because it creates parts through the direct fusion of materials, which are then deposited on the object or prototype, layer by layer. This category includes DED, EBAM, LENS, LMP and Cladding.

To the macro-categories highlighted above, we add HP®'s Multi Jet Fusion (MJF), which due to the presence of both the binding agent and the fusion agent is considered as a mix between power bed fusion and binder jetting.

 

HP® Multi Jet Fusion (MJF)

 

Among the main technologies in terms of performance are HP® Multi Jet Fusion (MJF), the printers used by PolyD. For more on MJF printing you can read our Complete Guide to MJF Printing Technology. Multi Jet Fusion is the 3D printing technology developed by Hewlett-Packard (HP) in 2016, which has become popular for its ability to produce parts with:

  • high surface quality,
  • complex geometric designs,
  • excellent mechanical properties,
  • part strength,
  • incredible print detail,
  • high production speed.

In the Multi Jet Fusion process, a bed of thermoplastic powder, usually nylon, is evenly distributed on a printing platform. Next, one head deposits a fusing agent on each layer of powder, followed by another that deposits an inhibiting agent to control fusion in specific areas of the object. Then an infrared lamp uniformly heats the material and induces fusion in the areas where the fusing agent has been applied.
With the latest generation of MJF printers, PolyD has increased production capacity and operational efficiency:

  • processes are now even more flexible and optimised,
  • costs and operating times are significantly reduced,
  • production volumes have increased.

If you want to learn more about HP printers read '3D Automation Solutions'.

 

1. Material Extrusion 

 

FDM stands for Fused Deposition Modelling. A synonym for Fused Deposition Modelling is FFF (Fused Filament Fabrication). The FDM technology is owned by Stratasys, while FFF is a faithful opensource reproduction.
It is one of the most popular and accessible technologies. In Fused Filament Modelling, 3D printers use an extruder to selectively deposit filaments on a work surface, which solidify to create the designed three-dimensional object. During printing, the head moves across the plane in three dimensions (X, Y and Z axis) and supports may be required to support the objects, supports that are made at the same time as the object and only removed after the print is complete. Parts printed with FDM technology have visible layers on their surfaces, especially on parts with complex geometries or pronounced angles. The most commonly used material is PLA (polylactic acid) or ABS (acrylonitrile butadiene styrene) filament; PETG, Nylon, TPU are also available.
If you want to learn more, read our articles on the Pros and Cons of FDM and MJF Printing Technologies.

 

2. Vat Photopolymerization 

 

Continuous Liquid Interface Production (CLIP) is a technology that combines the principles of stereolithography and photopolymerisation printing. Unlike layer printing, it involves the production of a part through a continuous printing process that solidifies the liquid resin, without separate layers. This makes it possible to print parts much faster and with a more uniform surface.

In Digital Light Processing (DLP), a digital projector projects a 2D image of each layer of the object onto a pool of liquid photosensitive resin. This resin is polymerised by the UV light emitted by the projector, solidifying the corresponding layer of the model. Once a layer is solidified, the table is lowered to allow the next layer to be formed, and the process is repeated until the object is fully constructed.

During the Scan, Spin, and Selectively Photocure (3SP) process, a UV laser is used to polymerise a thin layer of liquid photosensitive resin on a substrate, according to the 3D file. The model is rotated, allowing for an even distribution of the material and ensuring a higher production speed. This cycle of scanning, rotation and selective polymerisation continues until the desired object is completed.

Stereolithography (SLA) uses liquid resins to create three-dimensional objects. During the Stereolithography process, a special UV laser selectively hardens thin layers of liquid resin. The laser moves along a predetermined path, solidifying the resin in the exact areas where it is required by the model, layer by layer. During the melting process, fumes are emitted, requiring proper ventilation and compliance with precise health regulations. If you want to know more, read our article on MJF, FDM or SLS. PolyD's tips for your 3D Printing.

 

3. Power Bed Fusion

 

Digital Metal Printing (DMP) is Direct Metal Printing, also known as Direct Metal Laser Sintering ( DMLS). It enables the production of complex, high-precision metal parts with a similar strength to objects made using traditional production techniques such as milling and casting.
The production mode is similar to that of SLS technology: a laser melts and solidifies metal powders layer by layer.

Selective Laser Melting (SLM) uses a high-power focused laser to selectively melt and solidify metal powders or metal alloys, layer by layer, without the aid of binders.

Selective Laser Sintering (SLS) uses a selective melting process with a laser. It is used with a variety of powdered materials, including plastics, metal, ceramics and composites. The SLS process starts with a bed of powdered material placed uniformly on a printing plate. A precision laser selectively sinters the powder particles, fusing them together layer by layer according to the desired 3D pattern.
SLS produces parts without the need for supports, as each layer of powder acts as a carrier for subsequent layers. SLS is particularly suitable for the production of parts requiring strength, durability and dimensional accuracy. However, post-processing of the moulded parts may be necessary to achieve optimum surface finishes and to remove any residual powder.
Read more in our article on MJF, FDM or SLS. PolyD's tips for your 3D Printing.

A variant of SLS is Micro-Scale Selective Laser Sintering (µ-SLS); it uses a small-scale laser to create parts with microscopic detail, often in the micrometre range. It is mainly used for the production of microfluidic devices, semiconductors and electronic components.

 

4. Binder Jetting

 

Metal Binder Jetting (MBJ) involves the distribution of a layer of metal powder onto a substrate, followed by the selective application of a liquid binder via a printhead. The binder is only deposited in the areas where solidification is required and the deposition and solidification cycle continues until the object is completed. Subsequently, the object is sintered to remove the residual binder and solidify the metal particles.

Sand Binder Jetting (SBJ) combines sand or similar materials with a binder to produce three-dimensional models or components. An even layer of sand is distributed on the work surface; the printhead then applies the liquid binder only to the areas where solidification is required. Subsequently, the object can be sintered or treated by other methods to increase its strength and durability, depending on the application used

 

5. Material Jetting

 

In Material Jetting, objects are constructed by depositing layer after layer of photopolymer, metal or wax, in a point mode similar to inkjet printers. As soon as the photopolymer comes into contact with light or heat, it solidifies. Material jetting printers have two print jets, one for the construction of the part and the other for the dissolvable substrate. Material jetting is often used to make moulds.

Drop on Demand (DOD) uses printheads equipped with small apertures through which material is selectively deposited layer upon layer, only where it is required. It can be used with plastics, ceramics and metal.

Multi Jet Modeling (MJM) uses a combination of material jets and binders to produce three-dimensional models. Layers of photopolymer are superimposed and polymerised with the aid of UV light. Parts and components can be directly printed in multiple colours, in translucent and transparent materials.

MJM is also known as PolyJet. PolyJet, similar to SLA, uses a solidified liquid resin layer by layer, but unlike SLA, which uses a laser to polymerise a liquid resin, PolyJet printers use ultraviolet light. The printers work like inkjet printers, only instead of ink droplets they use plastic droplets polymerised precisely by UV light. PolyJet is a trademark owned by Stratasys.

 

6. Sheet Lamination 

 

The process behind Selective Deposition Lamination (SDL) involves the 'selective' deposition of thin layers of plastic material onto a substrate, followed by their lamination and fusion to create a three-dimensional object. During the execution of the process, the plastic material is extruded or deposited in a controlled manner on a work surface, following the 3D file. Subsequently, the deposited layers are joined by applying heat or pressure, ensuring strong adhesion between them and the formation of a cohesive structure.

Laminated Object Manufacturing (LOM) uses layers of materials such as paper, plastic or metal to construct three-dimensional objects. The process involves the selective cutting of sheets of material and their subsequent bonding or welding, layer by layer, until the desired object is obtained. During the process, a roller or cutting head controlled by CAD software is used to cut the sheets according to the profile of the object to be printed. After each cut, a layer of adhesive is applied between the sheets to join the previously cut layers. The cutting and gluing cycle is repeated until the component is complete. Once finished, the part can be finished or treated further to improve its mechanical or aesthetic properties.

 

7. Directed Energy Deposition 

 

Cladding applies a layer of material to the surface of an existing component to improve its properties or change its appearance. This additional layer, called 'cladding', is made of different materials than the base component, such as metals, ceramics or composites, and is applied through a variety of techniques, including welding, thermal deposition or chemical deposition. The cladding process is used to improve wear resistance, corrosion resistance, thermal or electrical conductivity.

Directed Energy Deposition (DED) begins by feeding a source of material, commonly in the form of powder or filament, into a deposition chamber. Once the optimum temperature is reached, the material is melted and deposited onto a substrate or work surface using a controlled jet. The melted material is then further melted using an energy source such as a high-power laser or electron beam to melt the newly deposited material. The process continues layer by layer until the desired shape of the object is completed.

Electron Beam Additive Manufacturing (EBAM) uses an electron beam to selectively strike and melt metal powder particles on the substrate, following the 3D pattern. It offers higher production speed than other metal technologies and enables the production of large components with fine details and good mechanical properties.

In Laser Engineered Net Shaping (LENS), it uses lasers that weld streams of air-blown metal powders to customised parts. A high-power laser beam strikes a small spot on a metal substrate, producing a 'pool' into which an auger blows tiny amounts of metal powder to fill it and increase its volume.

Also in Laser Metal Deposition (LMD), a high-power laser melts and solidifies metal powders, wires or metal powders mixed with binders, layer by layer.

 

Other Additive Technologies

 

BiofabricationTM and Bio 3dprinting is an automated method that, through the use of 3d printing software and hardware, enables the use of living cells as base materials to produce tissues. The technique is basically based on 3 elements:

  • bioink, i.e. the solution composed of cells;
  • biopaper, i.e. the bio-absorbable matrix on which the solution is deposited;
  • bioprinter, i.e. the printer specially modified to 'print' viable tissue.

The cells once fused form the tissue structure.
It is widely used in medicine to regenerate organs, to produce tissue, to develop organoids and disease models.

Carbon DLS TM (Digital Light Synthesis) is a printing technology that combines photopolymerisation with the use of advanced resins to produce components with superior performance. It uses UV light to polymerise liquid resins, precisely layering them to create three-dimensional objects.

Ceramic 3D Printing makes it possible to print objects with ceramic materials, such as clay or silicates. Ceramic 3D Printing involves additive manufacturing systems and types of 3D printers that are also used in other sectors: extrusion, binder jetting, powder sintering, photopolymerisation. Objects such as pots, plates and components for industrial applications are thus produced.

Electron Beam Melting (EBM) uses a beam of electrons projected onto a bed of metal powder. The melting and solidification process takes place layer by layer in a vacuum environment at a temperature of around 1000°C. It is widely used in aerospace because it allows the creation of large parts.

Powder Bed and Inkjet Head 3D Printing (3DP) was patented in 1993 by the Massachusetts Institute of Technology and is the first trademarked use of the term '3D printing'. It makes use of plastic powders, ceramics and metals. This process involves the use of a bed of powder as a substrate, onto which a binding ink is selectively deposited by inkjet printheads. The powder particles are then fused together layer by layer, following the 3D pattern. Once printing is complete, the object is removed from the powder bed and can be further processed to improve its mechanical or aesthetic properties.

 

The contents are constantly evolving and being supplemented. If you would also like to contribute by reporting 3d printing techniques that we have not considered, please write to hello@polyd.com 

 

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Happy 3D printing!