Selective Laser Melting (SLM) is an additive manufacturing process that can be used for many different applications.
The SLM process starts by numerically slicing a 3D CAD model into a number of finite layers. For each sliced layer a laser scan path is calculated which defines both the boundary contour and some form of fill sequence, often a raster pattern. Each layer is then sequentially recreated by depositing powder layers, one on top of the other, and melting their surface by scanning a laser beam.
The powder is spread uniformly by a wiper. A high power-density fibre laser with a 40µm beam spot size fully melts the pre-deposited powder layer. The melted particles fuse and solidify to form a layer of the component.
SLM has been effectively used for actual manufacturing of engineering components. New products are entering into the marketplace at a fraction of the product development time, as compared to conventional techniques, and the life cycle costs of existing products are minimised. The introduction of ALM also changes the manufacturing practice from a resource base to a knowledge base, which the manufacturing segments are moving from mass-produced, single-use products, to new mass-customized, high-value, life-cycle products.
A number of industries such as Aerospace, Oil and Gas and the Medical industry are actively working with additive manufacturing. The technology is suited to creating geometrically complex components that can’t possibly or feasibly be made by any other means. The process can build parts with large aspect ratios and large surface areas components that are low volume. This lends the process nicely to the heat exchanger applications.
The technology allows for the creation of parts for low volume fabrication, which means that parts can be individually customised to suit any need. This leads the medical industry to design optimised parts for implantation to meet the needs of individual persons, meaning a higher acceptance of parts in patients.
In the aerospace industry, parts need to be optimised for strength and weight. SLM provides the design freedom that is missing from conventional manufacturing methods. Components can be designed to have material only where it is needed; this reduces the weight of the overall part. As many parts are made from exotic expense materials, it is key that material wastage is minimised. SLM achieves this as material is only solidified where it is needed and any remaining metallic powder can be used for the next build.
Overall SLM enables the ability to manufacture for design and reduces design for manufacture.
SLM allows for better product development meaning reduced time to design test and more time for iterative design evolution. Low volume fabrication is possible due to the ability to bypass the need for expensive tooling. Functionally graded structures are possible allowing new possible design routes for components, this enables a combination for example low cost parts with high wear resistance.
TWI can control the temperature gradients seen by the manufactured parts during the process to deliver the highest quality components. There is vast expertise in procedures for the process optimisation for new materials this is due to Member organisations driving the advancement of material development.
TWI has two SLM machines on site at its South Yorkshire location. Both machines operate in an inert argon atmosphere and can process reactive materials and have heated process chambers. The SLM100 machine has a build area of 100mm diameter with around 80mm build height available. It uses a 50W laser to process the material.
The SLM250 machine has a larger build envelope at around 250 mm cubed with a higher laser power of 200W. The machine has the advantage of having a vacuum processing chamber so that the parts can be made in only 1ppm of oxygen.
Benefits of SLM:
- Optimise material usage saving of cost
- Improved production development cycle
- Allows for complex geometry to be made
- Ideal process for low volume production
- Improve buy-to-fly ratio
- Functionally graded parts can be produced
- Allows for fully customised parts to suit the individual
For further information or if you have any questions please do not hesitate to contact us.
