Additive Manufacturing And Its Various Process

What Is additive Manufacturing?

ASTM F42- Additive Manufacturing is the official industry term for all application of technology for additive manufacturing.

It is basically a process of joining of material and forming a 3D modal data by placing layer upon layer as opposed to subtractive manufacturing methodologies. There are various terms used for the indication of additive manufacturing such as additive fabrication, additive processes, additive techniques, additive layer manufacturing, layer manufacturing & freeform fabrication.

There are various applications of additive manufacturing in which primary applications include the designing or modeling, fit and function prototyping, and direct part production. Additive manufacturing is bringing a big change in the way organisation design and manufacture products. Which helps the industries to save an impressive amount of time and money. Companies state that additive manufacturing is helping in trimming the weeks or even months of designing, prototyping and manufacturing time by avoiding costly errors and enhancing product quality.

Additive Manufacturing process

Although the Additive manufacturing process is the same i.e. layer-by-layer fabrication of 3D object production techniques vary.

In 2010, the American Society for Testing and Materials (ASTM) grouped AM Process into seven categories:

  • Powder Bed Fusion
  • Vat Photopolymerization
  • Binder Jetting
  • Material Extrusion
  • Directed Energy Deposition
  • Material Jetting
  • Sheet Lamination

These Additive Manufacturing process includes a noteworthy variation on the layered 3D printing concept. Varying on the parameters of material state (powder, liquid, filament), light or heat sources (laser, thermal, electron beam, plasma arc), no. of print axes, feeding system, build chamber characteristics etc. Some additive Manufacturing techniques also require post-production processing also.

Power Bed FusionPower bed fusion process of additive manufacturing

Power bed fusion (PBF) is common process in the popular additive manufacturing techniques like, direct metal laser melting (DMLM), electron beam melting (EBM), directed metal laser sintering (DM LS), selective laser melting (SLM), selective laser sintering (SLS) & selective heat sintering (SHS)

PBF method involves melting the powder to at the sufficient temperature where particles fuse together to start forming a layer. In PBF particles are either partially or fully melted depending on the requirements. The ultrathin layer of melted particles is spread by a roller or blade in the layered format. The powder is fed from a reservoir below by following to a build podium that lowers to accommodate each successive layer of powder. At the end of the process, the unfused powder is blown away.

In general, EBM is a faster method than SLM and DMLM although it does not provide a smoother or thinner surface. This process helps additive manufacturing to grow in the medical sector for the orthopaedic titanium implants. In EBM wide range of metals, including titanium, stainless Steel, copper or cobalt chrome are used. It can also be used in the manufacturing of parts having less residual stress and distortion.

Vat photopolymerizationVat photopolymerization process of additive manufacturing

Vat photopolymerization is little different from other additive manufacturing process which is carried out by using liquid rather than powder or filament. As the printing technique differs since there is a use of photopolymer resins which are often tough, transparent and castable materials.

Stereolithography (SLA) is a photopolymerization process which is one of the oldest 3D printing processes that is actively being used today. It is light-activated, not a heat-activated process.

In this laser light comes from beneath the object, which is the reverse of the other additive manufacturing process that features the heat source directed from above. Resin solidifies as the laser maps each layer. After the contact between laser light and photo, polymer generates an object layer the platform rises, and more liquid resin gathers immediately underneath the object. UV light cures each layer.

Binder JettingBinder Jetting process of additive manufacturing

In binder Jetting process, it employs powder material and binding agent. In this additive manufacturing process nozzles of 3D printers deposit tiny droplets of a binder on an ultrafine layer of powdered metal, ceramic or glass.  In these multiple layers is formed from the powder bed moving downward after each layer is created.

The final result created is in a green state, in this, the post-processing is required. A cyanoacrylate adhesive is a common infiltrate when ceramic material is used. However, the ceramic results produced by binder jetting are brittle, so they are mostly used as architectural models or model for sand casting.

Material Extrusion

Most well-known additive manufacturing process is fused deposition modeling (FDM), or fused filament fabrication (FFF). In this process, a thermoplastic filament is extruded through a heated nozzle and onto the build platform and then solidifies as it cools. FDM uses a wide variety of thermoplastic filaments, including ABS, PLA, Nylon, PC and many more complex filaments like those that are metal filled or wood filled.

As the process is quite faster and inexpensive, companies are often using it for the prototyping purpose. There are still some come concerned related to the dimensional accuracy even though some FDM machines are producing functional prototypes.

This process is directionally dependent. As the material, I deposited along the X and Y axis the strength is an issue in Z direction. Some post-processing methods are required to improve the strength in the Z direction. Like creating a void across the layer during the printing of object that can be filled in post-processing by filling the voids with a hardening resin.

Directed Energy DepositionDirected Energy Deposition process of additive manufacturing

It is also called as direct metal deposition or metal deposition that develops highly focused thermal energy distributed via laser, electron beam or plasma arc to melt and fuse material jetted into a heated chamber from either powder material or wire filament.

The system is featured of metal deposition along 4-5 axes. This additive manufacturing process is basically used to repair worn to parts in automotive aerospace and defence sector.

In this LENS technology is used to make the solid parts as the solid is distributed from nozzles and melted by the laser. This solidifies melt pool on the build platform layer by layer.

During the process, metal melting happens through electron beam firing in the vacuum chamber. Each layer is consisting of fully melted metal powder or wire filament as thin as 20 microns each.

In the end, with rapid plasma deposition (RPD), a plasma arc melts a wire filament in an argon gas environment to produce parts that require little or no post-production machining. Like other additive manufacturing processes, RPD is often more cost-effective than traditional forging.

Material JettingMaterial Jetting process of additive manufacturing

Metal jetting is similar to the binder jetting process that uses drop-on-demand (DOD) technology. It works with the same concept of 2D inkjet printer in which tiny nozzles distributes droplets of waxy photopolymer, layer by layer. Then UV lights help for the creation of layer by hardening the droplets. Since the additive manufacturing is dependent on support structures, a next nozzle distributes a dissolvable polymer that helps object in printing after the completion of the project the support material dissolves away.

In material jetting liquids infused with the metal particle. Once the droplets are deposited onto the print bed the high temperatures in the heated build chamber cause the liquid to evaporate, leaving a layer of metal.

Sheet LaminationSheet Lamination process of additive manufacturing

In this process of additive manufacturing, an adhesive is used for the bonding of the ultra-thin layer of solid material. Due to the flexibility of using a variety of material during this additive manufacturing process, it is also called as laminated object manufacturing (LOM).

Ultrasonic additive manufacturing (UAM) is using metal sheets, foils or ribbons to build create a single layer of an object at a time. Titanium, stainless steel, copper and aluminium are used for these types of process. In this process, the metal layer is adjoined through ultrasonic welding and then compressed by a device that causes ultrasonic vibrations.

The consumption of the energy is less in the UAM process comparing to the other additive manufacturing process as no melting is required. For smother surface or removal of excess material can be done by CNC machines.