3D PRINTING
ADDITIVE MANUFACTURING AND ITS TYPES
Introduction
3D printing, or additive manufacturing, is the construction of a three-dimensional object from a CAD model or a digital 3D model.
A CAD model allows someone to see a part in three dimensions, including any intricate features that would be difficult to depict in a two-dimensional drawing.
The term "3D printing" can refer to a variety of processes in which material is deposited, joined, or solidified under computer control to create a 3D object, with the material being added together (such as plastics, liquids, or powder grains being fused together), typically layer by layer.
Processes of Additive Manufacturing
Modeling
3D printable models may be created with a computer-aided design (CAD) package, via a 3D scanner, or by a plain digital camera and photogrammetry software.
CAD models can be saved in the stereolithography file format (STL), a CAD file format for additive manufacturing that stores data based on triangulations of the surface of CAD models.
Printing
Before printing a 3D model from an STL file, it must first be examined for errors. Most CAD applications produce errors in output STL files, of the following types:
holes
faces normal
self-intersections
noise shells
manifold errors
Once completed, the STL file needs to be processed by a piece of software called a "slicer," which converts the model into a series of thin layers and produces a G Code file containing instructions tailored to a specific type of 3D printer.
This G-code file can then be printed with 3D printing client software (which loads the G-code and uses it to instruct the 3D printer during the 3D printing process).
Finishing
Some printing techniques require internal supports to be built for overhanging features during construction. These supports must be mechanically removed or dissolved upon completion of the print.
Additive Manufacturing Processes
There is a different category that comprises the additive manufacturing technology;
Vat photopolymerization
Material jetting
Binder jetting
Material Extrusion
Powder bed fusion
Directed energy deposition
Sheet lamination
Vat photopolymerization
- DEFINITION-
The vat photopolymerization method is a liquid-based process. This is a process in which liquid polymers are exposed to ultraviolet (UV) light to turn them into solids to form the desired shape and size.
- METHOD-
First, a 3D design is created in a 3D software program. Then, the 3D printer uses digital light processing technology. This works like a projector and projects the image with UV light on the surface of the liquid. This is done using the common layer by layer approach. One layer is considered at a time and the liquid polymer is hardened accordingly. The remaining polymer is drained off. Then the next layer is approached. This process of draining and exposure to UV light is repeated until the object is complete, with the vat completely drained and leaving the solid 3D object.
- MATERIAL-
Build Material:
Photopolymer(Thermoset)
Polymers:
UV-curable Photopolymer resin
Resins:
Visijet range (3D systems)
Vat Photopolymerization process gives good accuracy as well as Good Finish.
Vat Photopolymerization parts are used for quick displays or views of a newly modeled part.
Less consumption of timing for printing products.
Disadvantage:
There are fewer choices of Materials.
Compare to other processes this process is expensive
After the process, removal of material is a lengthy process.
Material Jetting
- DEFINITION:
Material jetting is an additive manufacturing process in which droplets of liquid resin are selectively deposited via inkjet-style print heads and solidified by ultraviolet light exposure to build a solid 3D object.
METHOD-
I. First, the liquid resin is heated to 30 - 60oC to achieve optimal viscosity for printing.
II. Then the print head travels over the build platform and hundreds of tiny droplets of photopolymer are jetted/deposited to the desired locations.
III. A UV light source that is attached to the print head cures the deposited material, solidifying it and creating the first layer of the part.
IV. After the layer is complete, the build platform moves downwards one-layer height, and the process repeats until the whole part is complete.
- Materials:
Acrylic photopolymers (thermoset)
- Advantages:
- Disadvantages:
Binder jetting
- DEFINITION-
Binder jetting is one of the additive manufacturing processes in which a binding liquid is selectively deposited to join powder material together to form a 3D part.
Binder jetting process is a unique process because it does not employ heat during the process like others to fuse the material together.
- METHOD-
- Materials:
Metals, sand (for ceramics), silica, and polymers
- Advantages:
Disadvantages:
Delicate parts may be brittle and may be damaged during post-processing.
The choice of materials used in Binder Jetting is narrow.
Material Extrusion
- DEFINITION-
Material extrusion is an additive manufacturing (AM) methodology where a spool of material (usually thermoplastic polymer) is pushed through a heated nozzle in a continuous stream and selectively deposited layer by layer to build a 3D object.
- METHOD-
The First layer is built as nozzle deposit material was required onto the cross-sectional area of the first object slice.
The following layers are added on top of the previous layers.
Layers are fused together upon deposition as the material is in a melted state.
Materials:
The Material Extrusion process uses polymers and plastics.
Polymers: ABS, Nylon, PC, PC, AB
Advantages:
Wide selection of print material
Easily understandable printing technique
Easy and user-friendly method of the material change
Low initial and running costs
Comparable faster print time for small and thin parts
No supervision required
Small equipment size compared to other AM
Comparably low-temperature process
Disadvantages:
Visible layer lines
The extrusion head must continue moving, or else the material bumps up
Supports may be required
Poor part strength along Z-axis (perpendicular to build platform)
Finer resolution and wider area increase print time
Susceptible to warping and other temperature fluctuation issues such as delamination
Toxic print materials
Power bed fusion
DEFINITION-
Powder bed fusion (PBF) is an additive manufacturing process and works on the same basic principle in that parts are formed through adding material rather than subtracting it through conventional forming operations such as milling.
Powder bed fusion creates three-dimensional parts one layer at a time using a powder that is stirred or melted with one of the two types of heat sources.
Laser Powder Bed Fusion
Electron Beam Powder Bed Fusion
Materials:
The Powder bed fusion process can use any powder-based materials, but the following materials are the most common
Selective heat sintering – Nylon (monochrome white thermoplastic powder)
DMLS, SLS, SLM: Stainless Steel, Titanium, Aluminium, Cobalt Chrome, Steel
EBM: Stainless Steel, Titanium, Aluminium, Cobalt Chrome, and copper
Advantages:
The process creates less waste and is more efficient.
This process works with a variety and range of materials.
You can create models or prototypes with this type of additive manufacturing.
Disadvantages:
This process is slower and more time-consuming.
Structural properties of these aren’t good compared to other manufacturing processes due to layer-based manufacturing.
This process uses high energy to create parts.
Directed energy deposition
DEFINITION-
Directed Energy Deposition (DED) is a metal additive manufacturing process where an energy source – usually an Electron Beam, Laser or Arc is directed toward a plate or other substrate material where it impinges with wire or powder feedstock material and melts, leaving deposited material on the substrate.
The DED process is known by other names, including Laser Engineered Net Shaping (LENS), Direct Metal Deposition (DMD), Electron Beam Additive Manufacturing (EBAM), Directed Light Fabrication, and 3D Laser Cladding, depending on the exact application or method used.
METHOD-
The following things are followed in this process.
Using the geometric CAD information, both the nozzle head and the build platform is moved to generate the 3D geometrical features
The laser beam melts the surface and creates a small molten pool of the material on the substrate at the start point along the build path
The feeders feed the powder through the nozzle into this molten pool
Using the CAD geometric information, CNC controlled head or the bed or both are moved along the build path to create the metal part feature.
Materials:
Typically used to work on metal parts, this process can also be used with polymers and ceramics.
Almost any weldable metal can be additively manufactured using DED, including aluminium, inconel, niobium, stainless steel, tantalum, titanium and titanium alloys, and tungsten.
Advantages:
DED technologies are used exclusively in metal additive manufacturing due to the nature of the process.
direct energy deposition has lot of advantages :-
Using the DED method we can create higher density material.
Basically this process is useful for repairing parts
Due to Fed material we can change material easily.
less amount of material required to build product.
These are some advantages of Direct energy deposition method.
Disadvantages:
- Along with advantages there are some disadvantages of this process.
- This process is very expensive compared to other additive manufacturing processes.
- support structures cannot be used during the build process, hence features like overhangs will not be possible.
- Parts produced using DED technology are lower in resolution with a poor surface finish.
Sheet lamination
DEFINITION-
The sheet lamination 3D printing technique is mainly used to produce colored objects in a high detailed resolution. As a build material, thin layered materials like aluminum foil or paper based filaments are cut into appropriately shaped layers, often by lasers or a very sharp blade.
Steps of Working:
The first step is to place the material that is to be 3D printed on the cutting bed of the machine.
Once that is achieved, the material should be bonded over the previous layer using a suitable adhesive.
After the bonding has been ensured, the cutting can start using a laser or knife.
The next layer is added and the process will be repeated. It is to be noted that steps number two and three can be interchanged depending on whether it is forming and cutting or cutting and forming a type of Sheet lamination.
Advantages:
Compared to any other 3D printing technology, SL 3D printing can print a part in a considerably lower print time.
Building a part with multi-materials is possible.
The cost of material, combined with the cost of 3D printing is very low than high-quality 3D printing processes.
This process enables you to manufacture parts and functional prototypes of a larger build volume.
Disadvantages:
Material waste can be high.
Limitations of material.
Post Processing is needed.
CONCLUSION
This blog article discusses the early versions of additive manufacturing for making fast prototypes that were initiated by the necessity of speeding the process in model development and shortening the time between product development and market placement. Additive manufacturing processes take the information from a CAD file that is later converted to an STL file. In this process, the drawing made in the CAD software is approximated by triangles and sliced containing the information of each layer that is going to be printed.
There is also a discussion of the relevant additive manufacturing processes and their applications and a review of how the parts are made using these additive manufacturing processes also discussed. The continuous and increasing growth experienced since the early days and the successful results up to date, there is optimism that additive manufacturing has a significant place in the future of manufacturing.
REFERENCES
S. Ashley, “Rapid prototyping systems,” Mechanical Engineering, vol. 113, no. 4, p. 34, 1991.
R. Noorani, Rapid Prototyping—Principles and Applications, John Wiley & Sons, 2006.
Image courtesy : Google.
GROUP 5
59_Ayush Yadav
60_Yahya Farooqui
61_Yash Yadav
62_Younis Giri
64_Shreyash Zalte
Awesome work Yash!
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