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Additive manufacturing by the selective laser melting process

Presentation

Manufacturing platform

The base of the experimental platform is a Phoenix PM100T machine.

Ses caractéristiques principales sont les suivantes :

  • 1064 nm continuous YAG laser,
  • Production volume : cylinder diameter 100 mm height 100 mm
  • Layering system with metal or ceramic roller
  • Manufactured chamber under controlled and heated atmosphere
  • Manufacture of base parts Aluminum, Copper, Iron, Nickel, Cobalt, Ceramic

Experimental modifications and related apparatus

The scientific exploitation of such a test means requires mastering the manufacturing parameters such as :

  • Basic materials : these are powders whose size, shape, flow properties are characterized by laser granulometry (10 nm-3 mm), density measurement, flow meter. These powders can be mixed for formulation purpose by turbulence or in the liquid phase.
  • Laser source: beam analyzer, power measurement, profile control (defocus, top-hat,)
  • The atmosphere by its measurement and control: measurement of pressures, oxygen level by electrolytic probe, residual atmosphere by mass spectrometer.
  • The temperature of the feed tank, the manufacturing tank, the melted zone and its periphery: measurement by thermocouples, optical pyrometry, remote thermal imaging (3-5 μm).
  • Thermal fields around the melted zone: thermal field measurement by visible cameras and / or coaxial SWIR (bath temperature, temperature gradients, heating rate and cooling).
  • Fusion and projection phenomena: high-speed camera visualization and synchronous laser illumination (808 nm).
  • The analysis of defects and their mastery through process-monitoring.
Expertise

The microstructures generated are studied and analyzed by optical and electronic microscopy, by X microanalysis. The surfaces and reliefs are measured by 3D optical profilometry. Morphological analysis is an increasingly important part of process monitoring. The looping of the thermal measurements with the finite element calculation takes all its dimension in the prediction of the microstructures, the residual stresses and the service behavior of the finished parts. The mastery of the process and the materials makes it possible to formulate new materials, not only adapted to this process but that only the intrinsic operating conditions make it possible to generate.

  • Experimental characterization of the materials from their elaboration to their properties in service
  • Development of process-specific instrumentation
  • Open and closed loop process control
  • Formulation of new materials with extended functionality
film 1 : Visualization of Powder Bed Lasers (Synchronous Laser Lighting Imaging)
 
The film highlights the ejection of particles during the lasage of a bed of powder. These particles, whose size is a few tens of microns, come from the formed liquid bath and not from the powder bed (consisting of particles of a few microns). These large particles ejected are one of the sources of manufacturing defect by SLM. These manufacturing defects, when they occur, lower the mechanical properties of the parts in operation.
 
 
film 2 : Thermal field measurement by coaxial SWIR vision (coming soon)
 
The coaxial vision during manufacture makes it possible to measure the thermal field around the melted zone. In general, the value and the stability of the thermal field conditions the microstructure of the materials during their solidification. Also, this type of very local measurement allows to consider the process monitoring of this type of machine. This will ensure the traceability of the manufacturing and the metallurgical stability of the parts produced.

The vertical line is a pointer that shows the variation of the thermal gradient back of the melted zone.

 

Additive manufacturing by the selective laser melting process - MINES ParisTech
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