Additive manufacturing is gaining momentum as a process capable of manufacturing highly complex components quickly and directly.
In previous articles, we have already mentioned some advantages and applications of additive manufacturing and we have also explained how the additive manufacturing process works step by step.
This time, we will talk about the families in which additive manufacturing (AM) technologies are classified according to the ISO/ASTM standards and we will mention some of these technologies (encompassed in each family).
The main families of additive manufacturing
According to the above-mentioned standard, the additive manufacturing technologies are grouped into 7 families:
- Photopolymerization
- Material extrusion.
- Material Jetting .
- Binder jetting
- Powder bed fusion.
- Direct energy deposition
- Sheet lamination
At Mizar Additive we are specialists in material extrusion, material injection and powder bed fusion, each with their corresponding technologies.
Let’s take a look at the features and technologies of each of these families.
Material Extrusion
Material extrusion consists of depositing the polymer in filament form through the heated nozzle on a moving head. The bed where the object is to be created moves vertically while the nozzle moves horizontally, allowing the molten material to build the object layer by layer.
Proper adhesion of the layers is achieved by precise temperature control or the use of chemical bonding agents (industrial glue).
In this family, we find the additive process FDM (Fused Deposition Modeling). This is a manufacturing process generally used for prototype modelling and small-scale production, which consists of depositing the material in layers until the part is formed.
The FDM manufacturing process
To start the process, the plastic or metal filament is introduced into a nozzle that has previously been collected on a spool. The nozzle is above the melting temperature of the filament material and is driven by stepper or servo motors. Various nozzle, platform and motor combination options are available.
The deposition moulding process starts with software, which starts from a stereolithographic file (in .STL format). . It is oriented so that it can be printed and divided into layers. If necessary, temporary support structures are created which are removed after the workpiece has been machined.
Material Jetting
Material jetting or MJ is one of the fastest and most accurate additive technologies This technology is based on the selective deposition of a mixture of photopolymer material in droplets on a platform.
This allows single-pass layers to be created for curing and solidification by UV light. In other words, it builds parts using liquid photopolymer droplets that solidify under ultraviolet light.
Mizar Additive is a specialist in technology with the same name (Material jetting); below, we explain how the MJ manufacturing process is carried out.
The Material Jetting manufacturing process
In the material jetting technology, the manufacturing process of each layer is divided into two distinct stages:
- First stage: jetting of photoreactive polymers in a liquid state.
In this first phase, the material is injected by means of multiple nozzles in the areas of the platform where it is necessary for the construction of the part including support structures.
- Second stage: solidification of the material by UV light.
In this second phase, while the material is being deposited in a liquid state, lamps emitting UV light start the photopolymerization of the material to bring it to a solid-state.
Powder Bed Fusion
Powder bed fusion involves melting metal powder particles through a heat source, a laser or an electron beam, to form complex parts by superimposing fused layers.
Among the existing PBF technologies, at Mizar we specialize in the following:
- Selective laser melting (SLM), using metallic powder
- Electron beam melting (EBM), using metallic powder
- Selective laser sintering (SLS), using polymeric powder
PBF technology uses a laser or an electron beam to fuse powdered material.
Selective laser melting SLM is a similar process to Selective laser sintering SLS, but due to the difference in melting temperatures of the polymeric and metallic materials, there are certain differences in the process.
As an example, in the polymer section (SLS) the working chamber is preheated to a few degrees below the melting temperature of the material. In this way, the laser provides very little energy to melt the material. In this way, the laser provides very little energy to melt the material. As there is high thermal stability and hardly any gradient, the area to be melted does not suffer internal tension, making it possible to manufacture parts without supports or scaffolding.
In contrast, in the SLM metal process, due to the high melting temperatures of the material, it is not possible to work at temperatures in the vicinity. This causes the part to suffer a lot of internal stress and needs to be supported to avoid deformation during manufacture. Once the process is finished, these supports or braces should not be removed until a stress-relieving process has been carried out.
Both processes use an inert gas (usually Argon or Nitrogen) to prevent oxidation of the materials during melting.
Finally, the electron beam melting process EBM uses the electron projection to reach the melting temperatures of the material. In this case, the working chamber is at a temperature of approximately 800-900ºC. This avoids the generation of internal stresses, but it is necessary to use supports that act as energy dissipation when melting the corresponding layer.
PBF manufacturing process
As in any additive manufacturing process, the design of a part begins with the creation of the model by means of software. The piece is cut into different layers with an approximate thickness of between 20 and 60 microns.
After that, the steps are as follows:
- The printer fills a chamber with inert gas and then heats it to the appropriate printing temperature.
- A thin layer of powder is deposited on the tray in relation to the height previously defined by the machine software. The laser sweeps the cross-section of the workpiece, fusing the metal particles together. Once the layer is finished, the tray is lowered and another layer of powder is added, repeating the process until the final piece is obtained.
- Finally, the printer must be cooled down to remove the unfused powder from the container and clean the printed part.
At Mizar we specialize in the design and production of all types of custom components. We have a team of qualified professionals and advanced machinery, in addition to investing in a constant R&D effort.
For more information, contact us and we will help you!
