In recent years, both academically and industrially, additive manufacturing (AM) has experienced rapid expansion because of its capability of producing customized products of intricate shapes. 3D printing has evolved as a promising technology for the creation of engineering parts or applications, as it is an additive technique, unlike traditional manufacturing techniques. The advantages of 3D printing include reduced material waste, easiness in manufacturing, minimal human participation and post-processing, and efficiency in energy, which make it a viable option for industrial application. The chapter provides a brief introduction to additive manufacturing and also addresses a variety of 3D printing techniques, as well as their benefits and drawbacks. A detailed discussion of the various materials that are suitable for each type of 3D printing procedure is discussed along with the application of AM and the challenges associated with it.
3D printing is a popular and versatile technique that comes with a plethora of applications and benefits. The term is synonymous with additive manufacturing which is an umbrella term for all 3D printing techniques. Additive manufacturing units build any part one layer at a time and bring a long list of advantages to the table.
Moreover, all the different types of 3D printing techniques allow you to choose between material types and get the right combination of surface finish, durability, speed, and cost. This article takes a look at the common methods of 3D printing and explains how they work to help you make the best choice for your project
Additive Manufacturing: A Brief Overview
As stated, Additive manufacturing is the umbrella term that describes all methods of 3D printing. Any 3D printing technique uses a CAD design from a computer and builds up the precise geometric shape in layers. That’s where the name additive manufacturing comes from. Contrary to this technology, traditional techniques generally require you to remove the surplus materials to create the shapes you need.
In the beginning, certain thermoplastics were the only suitable materials for 3D printing. This restricted the applications of the concept because plastics don’t have the necessary physical characteristics for many high-performance industries. However, the situation has improved with time as different techniques allowed the use of other materials like metals, ceramics, and even organic materials
Even then, thermoplastics are among the most popular materials for 3D printing technologies today. Acrylonitrile Butadiene Styrene (ABS), Polylactic Acid (PLA), PolyCarbonate (PC), and Polyvinyl Alcohol (PVA) are some of the most common choices. Across various industries because of their versatility and suitable characteristics.
Types of 3D Printing Techniques
Stereolithography (SLA)
Stereolithography (SLA) belongs to the VAT polymerisation category of 3D printing that utilizes light curable thermoset resins to build parts. It is a powerful 3D printing technology that produces extremely accurate and high-resolution parts that are capable of being used directly in end-use, low-volume production, or for rapid prototyping.
How Does Stereolithography Work?
An SLA printer consists of four primary sections:
- A tank filled with the liquid resin which is usually a clear and liquid plastic
- A perforated platform is immersed in the resin tank. It can be lowered into the tank and can move up and down along the Z-direction depending on the printing process
- A high-powered, ultraviolet laser
- A computer control unit that controls both the platform and the UV laser movements
- Step 1 – The UV laser draws the first layer of the print into the photosensitive resin. Wherever the laser incidents, the photo liquid solidifies. The laser is directed to the appropriate coordinates according to the design.
- Step 2 – After the first layer, the platform is raised according to the layer thickness (about 0.1 mm) and the additional resin is allowed to flow below the already-printed portion. The laser then solidifies the next and the process is repeated until the whole part is complete. The resin that is not touched by the laser remains and can be reused.
- Step 3 – After finishing the part, the platform rises out of the resin tank and the excess resin is drained. At the end of the process, the model is removed from the platform, washed of excess resin with alcohol and then placed in a UV oven for final curing. Post-print curing enables objects to reach the highest possible strength and become more stable.
- Step 4 – The support structures are removed during the post-processing process.
Materials for SLA 3D Printing
Amongst the most widely used materials for SLA, Xtmade offers:
- Rigid plastics: such as ABS SL 7820, PC – Like Heat Resist Translucent, Xtreme Polypropylene…
- Silicone rubbers: such as True Silicone
Selective Laser Sintering (SLS)
Selective laser sintering is an additive manufacturing (AM) technology that uses a high-power laser to sinter small particles of polymer powder into a solid structure based on a 3D model.
SLS 3D printing has been a popular choice for engineers and manufacturers for decades. Low cost per part, high productivity, and established materials make the technology ideal for a range of applications from rapid prototyping to small-batch, bridge, or custom manufacturing.
Recent advances in machinery, materials, and software have made SLS printing accessible to a wider range of businesses, enabling more and more companies to use these tools that were previously limited to a few high-tech industries.
How SLS 3D Printing Works
Printing: The powder is dispersed in a thin layer on top of a platform inside of the build chamber. The printer preheats the powder to a temperature somewhat below the melting point of the raw material, which makes it easier for the laser to raise the temperature of specific regions of the powder bed as it traces the model to solidify a part. The laser scans a cross-section of the 3D model, heating the powder to just below or right at the melting point of the material. This fuses the particles together mechanically to create one solid part. The unfused powder supports the part during printing and eliminates the need for dedicated support structures. The platform then lowers by one layer into the build chamber, typically between 50 to 200 microns, and the process repeats for each layer until parts are complete.
Cooling: After printing, the build chamber needs to slightly cool down inside the print enclosure and then outside the printer to ensure optimal mechanical properties and avoid warping in parts.
Post-processing: The finished parts need to be removed from the build chamber, separated, and cleaned of excess powder. The powder can be recycled and the printed parts can be further post-processed by media blasting or media tumbling.
Fused Deposition Modeling (FDM)
Fused deposition modeling (FDM) 3D printing, also known as fused filament fabrication (FFF), is an additive manufacturing (AM) process within the realm of material extrusion. FDM builds parts layer by layer by selectively depositing melted material in a predetermined path. It uses thermoplastic polymers that come in filaments to form the final physical objects.
Composing the largest installed base of 3D printers worldwide, FDM is the most widely used technology across most industries, and likely the first process you think of when 3D printing comes up.
How does FDM 3D printing work?
An FDM 3D printer works by depositing melted filament material over a build platform layer by layer until you have a completed part. FDM uses digital design files that are uploaded to the machine itself and translates them into physical dimensions. Materials for FDM include polymers such as ABS, PLA, PETG and PEI, which the machine feeds as threads through a heated nozzle.
To operate an FDM machine, you first load a spool of this thermoplastic filament into the printer. Once the nozzle hits the desired temperature, the printer feeds the filament through an extrusion head and nozzle.
This extrusion head is attached to a three-axis system that allows it to move across the X, Y and Z axes. The printer extrudes melted material in thin strands and deposits them layer by layer along a path determined by the design. Once deposited, the material cools and solidifies. You can attach fans to the extrusion head to accelerate cooling in some cases.
To fill an area, multiple passes are required, similar to coloring in a shape with a marker. When the printer finishes a layer, the build platform descends and the machine begins work on the next layer. In some machine setups, the extrusion head moves up. This process repeats until the part is finished.
Direct Metal Laser Sintering (DMLS)
Direct metal laser sintering (DMLS) belongs to the powder bed fusion (PBF) category of 3D printing and is similar to the SLS technology. In DMLS, however, metal powders are used instead of plastic powders to create metal parts that can be used both for functional prototypes and production parts.
Direct metal laser sintering technology is similar to Selective laser melting (SLM) technology, but the difference between both processes is the temperature used for metal powder fusion. SLM, as the name suggests, heats the metal powder until it fully melts into a liquid. DMLS does not melt the metal powder but sinters heat particles enough so that their surfaces weld together. Anyway, both terms (SLM and DMLS) are often used interchangeably in the 3D printing industry.
How Does DMLS Work?
The direct metal laser sintering process involves six basic steps:
Step 1 – The DMLS process begins by slicing the 3D design CAD file data into single extremely thin layers, generating a 2D model for each layer
Step 2 – The machine uses a high-powered optic laser, inside the build chamber area that contains inert gas
Step 3 – There is a material dispensing platform and a build platform along with a roller used to move new powder over the build platform layer by layer
Step 4 – On laying the powder on the build platform, the laser begins its path for this layer, selectively sintering the powder into a solid. The sequence of powder layer addition and sintering continues until the whole part is done
Step 5 – After cooling, the surrounding loose metal powder is removed from the printer. The final steps include support structure removal and other post-processes
Step 6 – DMLS parts can be treated like metal parts produced by conventional metal working for further processing. This may include machining, heat treatment, or surface finishing.
Materials for DMLS 3D Printing
Among the most generally used materials for DMLS, Xtmadeparts offers:
- Aluminium: such as AlSiMG
- Steel: such as Tool Steel MS1, Stainless Steel 17-4, Stainless Steel 316L
- Inconel: such as Inconel 718
Binder Jetting
Binder jetting is a simple method of 3D printing that relies on an industrial bonding agent to join different layers of a part. In binder jetting, the input is the key material in powder form which the printer deposits with a thin layer of a binding agent.
Furthermore, the process works with materials like sand, some polymers, metal powders, and ceramic metal compounds. This is among the low-cost 3D printing methods that can produce large volumes at a low turnaround time.
Moreover, the design flexibility and excellent color reproduction along with the dimensional accuracy of 0.2 mm (metal) come at a cost. The mechanical characteristics of your results will not be that good, thus limiting this technique to low-intensity applications only. For instance, some of the most common applications of Binder Jetting are:
- Metal parts
- Realistic models
- Low-cost prototypes
- Sand casting molds
- Material Jetting
Another popular choice among the types of 3D printing technology is the material jetting process. In this case, the 3D printer uses liquified material droplets to build each layer.
One thing that makes this process unique is the ability to use different types of material on a single object. As a result, you can fabricate parts with mixed colors and textures which can give you a customized aesthetic look of the final product.
Get Started With Xtmadeparts 3D Printing Service
Whether you’re confused about which 3D printing technique to use or you need quick prototyping services, Xtmadeparts is the ideal partner to have.
With Xtmadeparts, you have premium quality FDM, SLA, SLS and DMLS services available right at your fingertips, all offered at a competitive price. Moreover, Xtmadeparts offers you a wide range of materials and surface finish to select from. Not only that, if you’re confused about any step of the fabrication process, or need professional advice, you can reach out to us for guidance from our team of experts.
Contact us today to get started. You can also upload your files on the website to get a quote and a DFM analysis within hours, or send RFQs directly to [email protected].
