Additive manufacturing, also known as 3-D printing, is a transformative approach to industrial production that is making lighter, stronger parts and systems a possibility.
This article will delve in the concept of additive manufacturing, its types, and the materials used in additive manufacturing.
What is the additive manufacturing?
Additive manufacturing is processes used to create a three-dimensional object by laying down successive layers of material under the control of a computer. Objects created can be of almost any shape or geometry and are created from digital model data. It is intended to construct a part from scratch but raw material, using digital data coming from a CAD file.
The familiar term of additive manufacturing is 3D printing. This is a popular type of additive manufacturing.
Additive manufacturing types
1. Stereolithography (SLA)
SLA makes use of a vat of liquid photopolymer resin. A UV laser traces the pattern of each layer, causing the resin to solidify. This type used in prototyping, jewelry, and dental models.
2. Selective Laser Sintering (SLS)
SLS uses a laser to sinter powdered material, binding it together to create a solid structure. SLS can be found in creating functional prototypes, automotive parts, and aerospace components.
3. Fused Deposition Modeling (FDM)
FDM worked through the extrusion of thermoplastic filament via a heated nozzle, layer by layer. FDM applications include prototyping, custom tools, and educational models.
4. Digital Light Processing (DLP)
DLP is similar to SLA, though using a digital light projector screen that flashes a single image of each layer all at once. DLP applications include high-detail prototypes, jewelry, and dental applications.
5. Electron Beam Melting (EBM)
A process in which an electron beam melts metal powder to build a part, layer by layer. EBM used in creating aerospace parts, and medical implants.
6. Directed Energy Deposition (DED)
In this type the focused thermal energy fuses the materials by melting as they are deposited. DED used in restore and add features to existing parts, manufacture large metal parts.
7. Binder Jetting
In this type a liquid binding agent is deposited onto a powder bed layer by layer. This type used in sand casting molds, metal parts, full-color prototypes.
8. Material Jetting
Droplets of material are selectively deposited layer by layer to build a part. Material jetting applications include full-color prototypes, tooling, and medical models.
Materials used in additive manufacturing
Additive manufacturing, or 3D printing, has steeply grown its materials portfolio. The chosen material will be everything in a project, determining the success by properties in the final product, cost of the final product, and suitability for application.
The materials used in additive manufacturing are categorized into: metals, polymers, ceramics, composites, and biomaterials.
1. Metals
- Titanium: This property is based essentially on the strength-to-weight ratio and finds wide application in the aerospace and medical implant industries.
- Stainless Steel: Offers resistance to corrosion and durability.
- Aluminum: A light metal with strength that finds major uses in the automotive and aerospace industries.
- Nickel Alloys: Having excellent heat and corrosion resistance.
- Cobalt-Chrome Alloys: Mainly used in dental and medical implants.
2. Polymers
- Thermoplastics, which melt and solidify several times. Examples include ABS, PLA, Nylon, and Polycarbonate.
- Photopolymers: These resins cure on exposure to light and find application in processes such as Stereolithography, SLA.
- Elastomers: Flexible materials such as Thermoplastic Polyurethane (TPU) which used to produce parts that have rubbery characteristics.
3. Ceramics
- Alumina: Known for its hardness and durability, used in industrial and biomedical applications.
- Zirconia: Offers high strength and toughness, used in dental restorations and engine components.
4. Composites
- Carbon Fiber Reinforced Polymers (CFRP): Offers high strength and stiffness, used in aerospace and automotive industries.
- Metal Matrix Composites: Combine the properties of metals and ceramics, used in high-temperature applications.
How dose additive manufacturing work?
The additive manufacturing process generally involves several steps: designing the model, preparing the file, setting up the printer, printing the object, and post-processing.
1. Design the Model
The procedure begins once a 3-dimensional digital model is made using a certain type of CAD software. The model should be accurate and highly detailed as this will serve as the foundation during the actual construction of a haptic object. Among the commonly utilized CAD software are AutoCAD, SolidWorks, and Blender.
2. Process the Digital File
After the product design is completed, the CAD file is converted into an STL (stereolithography) file. The STL file represents the 3D object using a mesh of triangles, heavily approximating the geometry for slicing. The STL file is input into slicing software that slices the model into very thin, finely cut horizontal layers.
The software translates this file into G-code, which provides instructions on how to construct each part. Essential parameters, such as the layer height, print speed, and support structures, are set in this process.
3. Preparation of the Printer
The printer is loaded with the required material for the print: examples of this are the distribution of thermoplastic filament, resin, or metal powder. Most printers require their material to be preheated or conditioned to work properly.
Leveling of the printer bed and calibration of the print head are done to have proper deposition of the layers. Calibration is important to maintain the quality of the print and to conform to the specifications of the design.
4. Printing the Object
Following the G-code instructions, the printer starts constructing the object layer by layer. The thickness of the layer, typically ranging from 20 to 100 microns, depends on the printer and the resolution required.
Different additive manufacturing technologies build layers through a variety of methods:
- Stereolithography (SLA), which cures liquid resin layer by layer using a UV laser.
- Fused Deposition Modeling (FDM), where thermoplastic filament is extruded through a heated nozzle.
- Selective Laser Sintering (SLS), using a laser to fuse powdered material.
- Electron Beam Melting (EBM), where an electron beam melts metal powder.
- Binder Jetting, where a liquid binder is applied selectively into powdered material.
Some printers run in controlled environments for temperature, humidity, and inert gas atmospheres in particular for metal printing.
5. Post-Processing
The supports used to hold the object during the build process are removed manually or with specialized tools after printing.
Additional finishing processes, such as sanding, polishing, and painting, might be necessary for the printed object to achieve good surface quality.
All metal prints normally undergo some thermal treatments, like annealing or sintering, to enhance mechanical properties or reduce internal stresses.
Verification check of accuracy and quality is carried out for the last part to ensure that it meets the design specification and functional requirement.