3D Printing Technologies

As 3DP is one of the rapid growing industries, many technologies for 3D printing have been developed over the last few years. Here is the glimpse of the important 3D Printing technologies.

Stereolithography

Stereolithography Apparatus(SLA) is a liquid grounded process that builds corridor directly from CAD software. SLA uses a low-power ray to harden the print-sensitive resin and achieve polymerization. The Rapid Prototyping Stereolithography process was developed by 3D Systems of Valencia, California, USA, innovated in 1986. The SLA rapid-fire prototyping process was the first entry into the rapid-fire prototyping field during 1980s80’s and continues to be the most extensively used technology.

Process

The process begins with a 3D CAD train.

The train is digitally sliced into a series of resemblant vertical ccross-sectionswhich are also handed to the stereolithography

outfit( SLA) one at a time. A laser also traces the path of the cross-section on the photopolymer which solidifies to form a sub caste. The ray also solidifies the coming sampling. The process is repeated until the part is complete. Once the model is complete, the platform rises out of the handbasket and the redundant resin is drained. The model is also removed from the platform, washed of

redundant resin, and also placed in a UV roaster for final curing.

Photopolymer materials consist of:

a)Binder

b)monomer

c)Photo initiator 

Applications

1. The SLA technology gives styles for reducing time to

request, lowering product development costs, gaining lesser

control of their design process, and perfecting product design.

2. Models for conceptualization an developed conception),

Packaging, and donation.

3. Prototypes for design, analysis, corroboration, functional testing.

corridor for prototype tooling and low volume production

tooling.

4. Investment casting, beach casting and molding.

5. Tools for the institution and driving design, and product

driving.

Fused Deposition method

FDM is the second most widely used rapid prototyping technology, after stereolithography. A plastic filament is unwound from a coil and supplies material to an extrusion nozzle. The nozzle is heated to melt the plastic and has a mechanism that allows the flow of the melted plastic to be turned on and off. The nozzle is mounted to a mechanical stage which can be moved in both horizontal and vertical directions. As the nozzle is moved over the table in the required geometry, it  eposits a thin bead of extruded plastic to form each layer. The plastic hardens immediately after being squirted from the nozzle and bonds to the layer below. The entire system is contained within a chamber which is held at a  temperature just below the melting point of the plastic.  

Powder bed fusion

Powder bed fusion (PBF) is a process of production of additives and works on the same basic principle in that parts are formed by adding substances instead of extracting them by performing normal synthetic functions such as grinding. The PBF process begins with the construction of a 3D CAD model, 'cut' by numbers into a few different layers. In each layer, a heat source scanner is defined that describes both the boundary compound and the type of filling sequence, usually ,a raster pattern as the heat source is a field of energy (e.g. laser). There are several types of PBF, selected by the heat source used and the type of composite material.

Selective laser sintering

Selective Laser Sintering, also called SLS is a type of additive manufacturing based on powder bed manufacturing. It prints the model layer by layer, by fusing the powder into the top surface of the model. Powder quality design and processing are also part of the SLS.

Process:

1. The powder bed is heated just below the melting point of the powdered material.

2. Once the bed is heated enough, the laser is activated, usually a CO2 laser, an the laser beam traces the geometric layer previously provided. 

3. Laser heats the powdered material together and fuses that layer, and this process is repeated layer by layer.

4. Building chamber is allowed to cool down before removing the part.

Material: 

Materials usually used for SLS are mostly polymers, usually polyamides

Advantages:

1. Freedom of design

2. Lack of need of support structures

3. Low cost per part

4. Creation of very complex parts

5. High-performance products and accuracy

6. Mass production

Disadvantages:

1. Longer production time

2. Parts have a grainy surface

3. Longer time for cool-down

4. Parts are weaker along the Y-axis

Applications:

1. Aerospace industry

2. Dental implants

3. 3D printed prosthetics

4. Hearing aids

Selective laser melting

Selective Laser Melting is one of the powder bed fusion processes, which is the most widely used in the AM industry. SLM uses a laser beam that melts and fuses the metal powders.A thin layer of powder is deposited over a substrate plate or on the previously deposited layer and the laser beam melts and fuses the powder particles as dictated by the CAD  data. Several process parameters have to be tuned carefully to fabricate a defect-free part. Some important process parameters are laser power, laser scan speed, hatch distance, hatch overlaps, hatch style, etc, which have a significant effect on the mechanical properties of the parts. The entire process takes place inside a closed chamber, usually filled with an inert gas like N2 or Ar, depending on the reactivity of the metal powder to be used.

Advantages 

1. Simpler process setup, relatively low cost

2. Faster cycle time, increased functionality

3. Large range of materials

4. The ability to tune properties during the processing of the parts, increased functionality

Disadvantages 

1. It has a relatively slow process (because of the process speed limitations) acute size restrictions

2. High power usage, high initial costs

Electron Beam Machining

EBM is a thermal process that utilizes a focused beam of high-velocity electrons for machining.

K.E. of electrons is converted into heat necessary for rapid melting and vaporization.

Electrons are generated in a vacuum chamber. The production of free electrons ( negatively charged particles) is obtained an electron gun. 

Similar to cathode-ray tubes.

It can also be a non-thermal type, where electrons are used to accelerate the chemical reaction and cause material removal.

EBM process requires a vacuum, so workpiece size is limited to the size of the vacuum chamber.

Working in short : 

It is a metal removal process by a high-velocity focused stream of electrons. As the electrons strike the workpiece with high velocity, their kinetic energy is transformed into thermal energy which melts and evaporates the material.

The electrons are accelerated while passing through the anode by applying a high voltage to the anode.

A  magnetic deflection coil is used to make an electron beam circular and to focus an electron beam at a point ( localized heating).

The process is carried out in a vacuum chamber to prevent electrons from colliding with molecules of the atmospheric air and to prevent tungsten filament from getting oxidized with air.

Advantages of EBM 

1. There is no mechanical contact between tool and workpiece, hence no tool wear.

2. Virtually all engineering materials can be machined by EBM.

3. Very small holes can be machined in every type of material with high accuracy.

4. Drilling of extremely small diameter holes down to 0.002 in.

5. Drilling holes with high depth/diameter ratios, greater than 100:1.

Disadvantages

1. The cost of equipment is high.

2. The rate of material removal is low.

3. It can be used for small cuts only.

4. Vacuum requirements limit the size of the workpiece.

5. Limited to 10 mm thickness.

Applications 

1. Drilling

2. Perforating of sheet

3. Welding

Laminated Object Manufacturing

Laminated object manufacturing is a process in which layers of plastic or layers of paper are fused, or laminated together using heat and pressure. The LOM technology uses layered material which is rolled on the building platform. Typically, the materials are covered with a paste layer and the feeding roller is heated to melt the glue. The layer is then pasted. A blade or laser is used to draw the geometry of a building object and to draw crosses across the space to facilitate the removal of final objects. Finally, the construction stage consists of a block made of materials and parallelepipeds that need to be removed.

Printed materials use paper and absorb materials such as wood, and can benefit from sand finishing, while paper materials are often covered with paint or lacquer to retain moisture.

The technology was introduced to the public by Cubic Technologies (formerly Helisys inc.) With a LOM plastic machine. Recently, MCr introduced their paper machine to add color to technology.

Materials that can be used:

This technology is very flexible as almost anything can be attached. During the process of producing additives, layers of adhesive paper, plastic, or metal are glued together in sequence. The most commonly used materials are paper as it is easily cut. Plastic can also be used, using a blade or laser during cutting. Metal sheets are very common because the cutting stage is complex.

Applications of Laminated object manufacturing:

LOM machines are mainly used for rapid prototyping plastic parts.LOM machines are widely used to make plastic prototyping parts faster. The low price and its speed make it easy to make prototypes, even though the products are far from the final use components.

  

Binder Jetting

Binder jetting is an industrial printhead that selectively applies a liquid binder to a thin layer of powder particles (sand, ceramic, metal, or composite moldings) to create high-quality, unique parts, and tools. It is a laminated molding process. Similar to printing from paper, this process is repeated layer by layer using the map in the digital design file until the object is complete.

Originally developed at the Massachusetts Institute of Technology in the early 1990s.

Types of Binder Jetting:

1. Furan Binder.

2. Silicate Binder.

3. Phenolic Binder.

4. Aqueous-Based Binder.

Working

The powder material is spread on the build platform with rollers

printheads apply binder adhesive to the powder at the required points

build platform is lowered by the thickness of the model layer

another powder layer in front A layer that can be spread over the layers of. The object is formed where the powder binds to the liquid

. The unbonded powder stays in place around the object

. This process repeats until the entire object is manufactured.

Advantages

o No support is required. This means less post-processing time and less material consumption compared to technologies such as melt deposition modeling and stereolithography.

o More economical: 100% of unused powder can be reused for future printing. With SLS 3D printers, only about 50% can be reused.

o No warpage or shrinkage: Because it does not use heat, it does not warp due to cooling differences like FDM 3D printers. However, please note that some shrinkage may occur during sintering after printing. No warpage means that a BinderJetting 3D printer is a great option for scalable component production.

o Full-Coloror Option: Few technologies are generally available for this option, only multi-jet fusion and material jetting.

Disadvantages

o Low part strength: Even with sintering or penetration, parts made with binder jets are not as strong as parts made with powder bed melting. They often have low mechanical strength and break / stretch with lower force.

o Less accurate than material jetting: Therefore, printing in full color may result in loss of binder jetting.

 

Material Jetting

The manufacturing process of Material Jetting 3D printing is generally similar to the standard 2D ink-jetting process. Using photopolymers, metals, or wax that hardens when exposed to light or heat (in the same way as stereolithography) ensures that the material is formed one layer at a time. The process of producing a jet of objects allows various objects to be printed 3D within the same component.

The material jet extracts a photopolymer from hundreds of tiny tubes to the print head to form a layer by layer. This allows asset jetting operations to incorporate a fast-paced construction, fashion-wise line, similar to other precise placement technologies that follow the process of completing a layer divider layer, also called a piece. The machine places droplets on the construction platform, and the UV lamps heal and strengthen them. Jetting Material processes require support, which is usually printed 3D at the same time during construction from a molten object. During the processing step, manufacturers remove the supporting material

Group Information

3D Printing: Home Assignment

Group ID: SY Mech D02

Group members:
1. Vivek Sanap (07)

2. Aarya Sangle (08)

3. Sanket Lavalekar (09)

4. Arya Sapre (10)

5. Atharva Shingade (18)

6. Siddharth Dhakar (20)