Selective Laser Melting

Schematic of the SLM process (reproduced courtesy of MTT Technologies Ltd)

Additive layered manufacturing (ALM) techniques, also known as Rapid Manufacturing, have been effectively used for actual manufacturing. New products are entering into the marketplace at 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 changed 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.

TWI has been involved in ALM processes since 2004, using Direct metal laser deposition (DMLD) technologies to repair engine components, hard-surfacing, and original part manufacture. The DMLD processes have extended the service life of aero components by up to 5 times and offer a substantial saving. It became evident that ALM processes hold the key of future manufacturing. In 2008, TWI expanded its ALM capabilities by acquiring two MCP Selective Laser Melting (SLM) systems, SLM 100 and SLM 250, so that industrial members can have access to this advanced technology and potentially improve their productivity.

SLM uses a 40µm beam spot fibre laser to fuse small particles of metal powders into a mass representing a desired 3D object. The laser selectively fuses powdered material by scanning cross-sections generated from a 3D CAD model of the part on the surface of a powder bed. After each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied on top, and the process is repeated until the part is completed.

Both SLM systems are fitted with a pre-heating build platform ideally for crack-susceptible alloys, and are capable of building very fine 20µm layer for good surface finish and high density parts. In addition, the TWI SLM 250 system has a unique vacuum processing capability, allowing oxygen sensitive materials, such as titanium, to be processed.

The SLM systems are designed not just for rapid prototyping applications. Among the common applications are, but not limited to the following:

• Product development
• Low volume
• High value component
• Functionally graded structures
• Complex geometry objects
• Reverse engineering

MCP SLM 100 machine at TWI	Example of intricate part that can be manufactured using selective laser melting

The following are among the commercially available materials used in the SLM systems at TWI:

- Titanium 6-4 (Ti-6Al-4V)

- Inconel 718 superalloy

- Rene 142

- Cobalt chrome

To discuss your potential application, to see a demonstration or to find out more about selective laser melting, please contact Robert Scudamore or Choon Yen Kong. lasers@twi.co.uk.