Metal additive
manufacturing

Selective Laser Melting (SLM)

Powder bed fusion is the leading technology in the precision manufacturing of geometrycally complex metal components.

There are different processes depending on the heat source used (laser beam or electrons), and on the material melting degree (sintered or fusion).

The most widespread process to manufacture metal parts is the so-called selective laser melting or SLM. It is also known as DMLS (Direct Metal Laser Sintering) or Laser Cusing.

The process starts by creating a three-dimensional model (3D) using computer-assisted design (CAD) software. This 3D model is saved as a STL format file, which is the triangulated representation of the model. Then, the software divides the file data into individual layers and they are sent to the SLM equipment.

In the configuration of a SLM machine, a (laser) heat source selectively melts a layer of powder, previously deposited in very fine, even layers (the layers indicated in the 3D) on a platform, generating the contour and interior of the part. This building platform descends, in z-axis after each layer, by a distance equal to the layer thickness (normally between 20 and 50 microns), an action that is repeated until the part is completed.

After building the part, and depending on its application, finish enhancement activities and/or thermal treatments may be needed to improve the mechanical properties.

Currently, materials such as stainless steel, tool steel, titanium alloys, nickel-based alloys, and aluminium alloys, among others, can be processed by SLM.

Densities of over 99.9% are often achieved, with a surface finish of around 4-10 μm. Therefore, this technology is very useful to manufacture final parts with very complex shapes and structures, with thin walls and/or hidden cavities or channels.

What we are currently working on

  • Optimization of powder compositions in agreement with the characteristics of the SLM process.
  • Development of customized AD HOC alignments for SLM technology.
  • Optimization of process parameters to achieve a dense and effect-free material.
  • Pre-processing stages: design of manufacturing process, definition of optimal support strategy, optimal orientation, etc.
  • Numerical simulation models based on FEM (Finite Element Method): to predict distortions in process and offset to ensure quality and repetitiveness.
  • Determination and optimization of mechanical properties.
  • Post-processing stages: optimization of heat and surface treatments, elimination of supports, guarantee of dimensional tolerances, etc.
  • Quality assurance: development of monitoring system to detect defects, non-destructive inspection techniques (NDT).
  • Support to the process industrialization.

Specific Equipment

MCP SLM Realizer 250 (From Realizer)

  • Year: 2007.
  • Building platform size 250 x 250 x 220 mm.
  • 200 W fibre laser.

SLM 61 - SLM 280 HL (from SLM Solutions)

  • Year: 2014.
  • Building platform size: 280 x 280 x 350 mm.
  • 400 W fibre laser. Flow package upgrade 2018.

RenAM 500Q (from Renishaw)

  • Year: 2018.
  • Building platform size: 250 x 250 x 350 mm.
  • 2 fibre lasers 500 W
  • Double melt pool monitoring system.

Publications and downloads

Publications
2018
A.M. Mancisidor, E. Gil, F. Garciandia, M. San Sebastián, O. Lizaso, M. Escubi.
Stirling engine regenerator based on lattice structures manufactured by selective laser melting. Procedia CIRP, 74, 72-75
2018
A. Iturrioz, E. Gil, F. Garciandia, M.M. Petite, A.M. Mancisidor, M. San Sebastián.
Selective laser melting of AlSi10Mg alloy: influence of heat treatment condition on mechanical properties and microstructure. Welding in the World, 62, 885-892.
2018
I. Setien, M. Chiumenti, S. van der Veen, F. Garciandia, M. San Sebastian, A. Echeverria.
Empirical Methodology to Determine Inherent Strains in Additive Manufacturing. Computers and Mathematics with Applications
2016
A. M. Mancisidor, F. Garciandia, M. San Sebastián, P. Álvarez, J. Díaz, I. Unanue.
Reduction of the Residual Porosity in Parts Manufactured by Selective Laser Melting Using Skywriting and High Focus Offset Strategies. Physics Procedia, 83, 864-873.
2016
P. Alvarez, J. Ecenarro, I. Setien, M. San Sebastian, A. Echevarria, L. Eciolaza.
Computationally efficient distortion prediction in Powder Bed Fusion Additive Manufacturing
International Journal of Engineering Research & Science (IJOER), 2, 39-46.

Success Cases

Optimized active flow control actuators manufactured with SLM for UHBR engine-powered aircraft.

Challenge

Development of new active flow control actuators (AFC) with innovative aeronautical designs to improve the fluid flow in future UHBR engines.

Solution

Manufacture by SLM of flow control actuators with optimized and complex designs that can be installed in small spaces in aircraft with high-efficiency engines.

Partners or strategic alliances

Development carried out within the framework of the FLOWCAASH project (Clean Sky2 Call) with AIRBUS as partners.

Manufacture of hydraulic blocks by means of additive manufacturing.

Challenge

Design optimization so as to permit manufacture by SLM. Improvement of functionality by modifying trajectories and/or shapes of interior channels. Weight reduction.

Solution

71% weight reduction has been achieved by eliminating material that has no functionality. The functionality achieved with the additive blocks is comparable to that of the traditional block, but using less material. The technical feasibility of the additive hydraulic blocks has been proven.

Partners or strategic alliances

Development carried out within the framework of the ADHYBLOCK and SHOPEN projects, financed within the Hazitek call of the Basque government, with HINE as partners.

Challenges

Challenges to be faced in the coming years:

Weight reduction.
Zero defect manufacturing.
Digital factory.
Flexible manufacturing.

María San Sebastián, PhD.

Main Researcher in SLM Additive Manufacturing.

PhD in Industrial Engineering by the University of Navarra (2004). Industrial and Materials Engineer (TECNUN, University of Navarra, 2000). Master’s in Business Administration, MBA Executive (ESTE, University of Deusto, 2008). She carried out her doctoral thesis in the field of conformability at high temperatures of different nickel-based alloys at the technology centre, CEIT, within the framework of different industrial projects. She joined AMPO S.COOP. in 2004, as head of the fusion plant, focusing on production activities and leading R&D projects. Since 2006, she has been working as a researcher in the Processes area at LORTEK. She has carried out her activity in research projects related to the simulation of finite element manufacturing processes, microstructural characterization and mechanical behaviour, advanced joining technologies, and metal additive manufacturing.