Powder Bed Fusion Processes

PBF is a type of additive manufacturing where a powder material is selectively fused together layer by layer using a focused energy source, like a laser or electron beam.

SLS is a specific PBF process where a laser beam selectively melts and fuses powdered material, creating a solid object layer by layer.

PBF processes are versatile and can use a wide range of materials, including polymers, metals, ceramics, and composites.

Powder fusion in PBF processes can occur through various mechanisms, including solid-state sintering, chemically induced sintering, liquid-phase sintering, and full melting depending on the material and process parameters.

Process parameters in PBF processes are crucial for the final product quality and include factors like laser power, scan speed, layer thickness, and powder bed temperature.

Powder Bed Fusion (PBF) is an additive manufacturing process where a powder material is selectively fused together layer by layer using a focused energy source, like a laser or electron beam.

Modifications to the basic PBF process can improve machine productivity, enable the use of different materials, and avoid patented features.

LS is a specific PBF process that utilizes a laser to melt and fuse powder, creating a solid object layer by layer.

LS uses a laser to scan and fuse thin layers of powder, with the build platform moving down after each layer to create a 3D object.

A powder leveling roller is used to evenly distribute the powder onto the build platform before each layer in LS.

Nitrogen gas is used in the LS chamber to prevent oxidation and degradation of the powdered material during the process.

LS can be used to process a wide range of materials, including polymers, metals, ceramics, and composites.

Examples of materials used in LS include nylon and composites for polymers, stainless steel, titanium, and aluminum alloys for metals, and various ceramic materials for ceramics.

LS is increasingly being used for direct digital manufacturing of end-use products, as the produced objects have properties comparable to traditionally manufactured parts.

Thermoplastics can be melted and reshaped repeatedly while thermosets solidify permanently and cannot be remelted.

A mathematical equation that relates the rate constant of a chemical reaction to the activation energy, temperature, and pre-exponential factor. It helps predict the rate of a reaction at different temperatures.

The minimum amount of energy that reactant molecules must possess to overcome the energy barrier and initiate a chemical reaction.

As temperature increases, the rate constant increases because molecules have more energy to overcome the activation energy barrier and react more readily.

A catalyst lowers the activation energy of a reaction by providing an alternative reaction pathway with a lower energy barrier, speeding up the reaction rate.

A process where chemical reactions between powders and atmospheric gases form a byproduct that binds the powder together, forming a solid material.

A sintering process where a liquid phase forms during the sintering process, allowing for faster densification and faster material transport.

Chemically-induced sintering often results in some porosity in the final material, requiring additional processing to achieve full density.

Post-processing, such as infiltration with reactive elements or furnace sintering, is often necessary to achieve the desired density and mechanical properties for most applications.

A process where powder particles fuse together due to the melting of a lower-melting-point constituent, acting as a glue for solid particles.

Used in traditional powder metallurgy to create materials like cemented carbide cutting tools, where Co is used to bind WC particles.

LPS can be utilized as a fusion mechanism in AM, particularly in Powder Bed Fusion (PBF) processes.

A type of LPS in PBF where the entire material region is melted, exceeding the layer thickness, creating strong bonds.

The heat from subsequent scans re-melts a portion of the previously solidified structure, ensuring strong bonding and high density.

Engineering metals and polymers are ideal for full melting PBF processes, with examples including nylon, titanium, stainless steel, and CoCr alloys.

The most common material used in PBF with full melting is nylon polyamide, due to a distinct melting point.

Full melting is crucial in PBF for materials like nylon to achieve maximum strength and density.

pLS machines use CO2 lasers and a nitrogen atmosphere with a small amount of oxygen. This environment is not suitable for directly melting and fusing pure metals or ceramics, which require higher temperatures.

Nylon polyamide materials are the most popular materials for pLS. However, other polymers and indirect processing of metals and ceramics with polymer binders are also possible.

EBM uses an electron beam, which is a stream of electrons moving at near the speed of light, while laser-based systems use photons traveling at the speed of light.

EBM has proven to be successful in PBF because it allows for the manufacturing of complex metal parts with high accuracy and density.

EBM uses the high energy of electrons to melt and fuse metal powder particles, creating a solid object layer by layer.

EBM and SLM are both PBF processes, but they differ in their energy source (electrons vs. laser) and temperature control. EBM operates in a vacuum with a high-energy electron beam, while SLM utilizes a laser in a controlled atmosphere.

Electron beam melting (EBM) is used in 3D printing to fuse powdered metal by selectively melting it with an electron beam. It's often used for creating complex and dense metal parts in a vacuum environment.

Powder bed fusion processes can utilize a broad range of materials, including polymers, metals, ceramics, and composites. This versatility makes it a popular choice for various applications and industries.

The surface finish and accuracy of powder-based additive manufacturing are typically inferior to liquid-based methods due to the nature of the powder. Finer particles lead to smoother surfaces, but handling them is challenging. Larger particles are easier to work with but impact surface finish, feature size, and layer thickness.

It's a method in powder bed fusion where a mask defines the areas to be sintered. The mask blocks the energy source (like a laser) from reaching unwanted regions, allowing selective fusion.

Adding an agent that absorbs more energy from the laser beam to specific areas increases the localized temperature, promoting sintering in those regions only, while other areas remain untouched.

Printing a substance that prevents sintering in undesired regions ensures controlled fusion in specific areas while keeping others untouched.

Using loose powder instead of a dedicated support material simplifies the process, saving time and resources during part construction and post-processing.

These systems use either temperature to control the material state (like melting and solidifying) or a chemical change (like curing or drying) to achieve bonding.

The process of introducing the feedstock material into the extrusion system, often in a powder or filament form.

The process of melting or dissolving the feedstock material to create a liquid or viscous state suitable for extrusion.

The process of pushing the liquefied material through a nozzle to form a continuous, controlled stream, building a layer of the final product.

The process of the extruded material transitioning back to a solid state, hardening and bonding to previously deposited layers.

The ability to precisely move the extrusion nozzle in 3D space, ensuring accurate layering and building of the desired shape.

A common extrusion-based additive manufacturing process where thermoplastic materials are melted and extruded layer by layer to create a 3D part.

Specialized extrusion techniques used to create biocompatible scaffolds for tissue engineering and regenerative medicine.