Laser in Vacuum (LaVa) - Technology

Laser in Vacuum supports supreme metallurgical properties of molten material

Laser Beam Generation - Principle

A laser emits a beam of electromagnetic radiation that is monochromatic, collimated and coherent. Lasers consist of three main components: 
– a pumping source: supply of stimulating energy

– laser medium: solid, liquid or gas

– an optical resonator: fully reflective mirrors and partially reflective mirror, which enables emission of beam.

Generation of Laser Beam Scheme of Principle / Source: Sciencedirect
Generation of Laser Beam Scheme of Principle / Source: Sciencedirect

Spatial coherence allows tight focusing of a laser and the beam stays parallel over great distances:

this is called “collimation”.

Temporal coherence emits light pulses in ultrashort femtoseconds with a very narrow wavelength spectrum, i.e. a single color of light.

Generation of Laser Beam / Source: Springer
Elektronenstrahlboren Beispiel / Quelle: Evobeam

Laser in vacuum machining requires requires ≤ 100 mbar in the working chamber. The picture sequence below  shows the impact of vacuum pressure on spatter behaviour.
 
Often only a single forepump can evacuate the chamber. The vacuum chamber and its designed cnfines the laser beam and potential reflections reliably in order to meet the safety requirements.

 

Evobeam’s laser in vacuum machining systems use pumps that minimize the evacuation time to increase productivity and production rates.

Impact of vacuum conditions on spatter with laser beam machining.

Laser im Vakuum

                              p= 1013 mbar                             p= 500 mbar                          p= 100 mbar                              p= 10 mbar

Laser in Vacuum fields of application

Most common laser in vacuum applications are welding and cladding.

Laser in Vacuum Welding / LaVa Welding

Electron Beam Weld Seams

As compared to atmoshperic pressure, Laser in Vacuum Welding can create much deeper and narrower seam with minimized heat input into the metal.

Warpage of the workpiece is significantly reduced or even avoided.

Applicable for magnetic materials as well.

Laser in Vacuum Cladding / LaVa Cladding

Laser in Vacuum Cladding

Laser in vacuum cladding technology enables precise control of layer properties with low heat input into the base material.

Laser in Vacuum - Systems & Options

Versatile range of laser in vacuum machining solutions supported by our scope of services

Electron Beam - Technology

Electron Beam is highly energy efficient and precise with respect to power density, focus, and deflection

Electron Beam Generation – Principle

Most commonly, a triode set-up is used to generate the electron.

The heating current Icauses the Tungsten filament to emitt electrons. These are accelerated by the acceleration voltage UA, between the cathode and the anode.

The Wehnelt cylinder applies the control voltage UW and allows very fast adjustments of the flux of electrons through the anode as an electron beam (EB).

The generation of a precise EB requires high vacuum conditions better than 10-4 mbar in the EB Generator chamber are mandatory.

Then the EB passes the electrical field of the focusing lense. The following deflection yokes enable a quasi inertia-free extremely dynamic and flexible handling and controlling of the beam properties with respect to geometry, focus levels, multi-process, multi-bed, oscillation figures, up-slope, down-slope, seam finding, seam tracking.

The vacuum (pressure, humidity) directly impacts the beam properties. This applies for the vacuum in the EB Generator as well as for the vacuum in the actual work chamber (see pictures below).

The vacuum is generated by specific pumps which evacuate the vacuum chamber and the housing of the EB Generator separately.

The vacuum chamber and its design shields the X-rays generated by the EB reliably in order to meet the safety requirements.

Evobeam’s electron beam machining systems generally features pumps that minimize the evacuation time to optimize productivity.

Scheme of Triode Setup / Source: Evobeam
EB Generator Scheme / Source: Tech Briefs 2011
EB Generator Scheme / Source: Tech Briefs 2011

The following pictures display the impact of vacuum on the electron beam. The visible beams are actually atoms that have been energized by the electron beam and emitt photons. The electron beam itself is invisible.

Electron Beam 5x10-4mbar

High Vacuum: 5 x 10-4 mbar

Electron Beam 5x10-2 mbar

Medium Vacuum:  5 x 10-2 mbar

Electron Beam 1000 mbar

Non-Vacuum: 1013 mbar

Electron Beam Fields of Application

Most common electron beam applications are: welding, drilling, cladding, surface treatment (e.g. hardening, surface structuring, engraving, polishing)

Electron Beam Welding / EB Welding

Electron Beam Weld Seams

The electron beam creates very deep and slender weld with minimized heat input and warpage of the workpiece.

Electron Beam Drilling / EB Drilling

EB Drilling Sample

The use of electron beam technology in drilling significantly increases productivity.
The highly dynamic adjustment of the beam characteristics enables the drilling of holes with very different diameters and depths in one pass.

Electron Beam Cladding / EB Cladding

Laser in Vacuum Cladding

The Electron Beam enables precise dosing of additive material and adjustment of layer thickness.

 

This supports the exact control of the material properties with respect to formation and hardness.

Electron Beam Surface Treatment / EB Surface Treatment

The electron beam is not reflected from shiny surfaces.
The electromagnetic deflection and focusing of the electron beam is currently twice as fast as the mechanical deflection of the laser beam.

Therefore, the following methods of surface processes for mass production are applied:

  • EB Hardening
  • EB Surface Structuring
  • EB Engraving
  • EB Polishing

 

Additive Manufacturing - Technology

Evolving approach with new production possibilities for metal machining

Additive Manufacturing - Principles

Currently there are around 18 different methods for metal additive manufacturing and the technology is rapidly evolving.

Structures are basically built up layer-by-layer.

Evobeam focusses on two Metal Additive Manufacturing methods based Fused Deposition Modeling (FDM):

  • Powder Bed Fusion
  • Wire-feed Energy Deposition

 

In both cases either electron beam or laser beam can serve as energy source.

Example of component built with additive manufacturing / Source: idw-online
Example of component built with additive manufacturing / Source: idw-online

Additive Manufacturing Benefits 

Numerous Impacts on metal manufacturing

In general, additive manufacturing opens new approaches for production strategies as well as systems and offers the following benefits.

Rapid prototyping, rapid tooling, rapid manufacturing, and rapid repair

  • Rapid prototyping:
    This is the most common appliocation of additive manufacturing: direct conversion of virtual CAD model into a real world 3D-item. This can be in original size or scaled down or up.
    Often, the material properties and component properties as well as component strength and surface quality are irrelevant for the purpose of a prototype.

  • Rapid tooling: 
    Parts or items for real usage with high requirements towards material properties, strength, etc.. These tools can then manufacture components with the conventional machining methods.

  • Rapid manufacturing:
    Direct manufacturing of customized production of small series in near net shape based on the CAD model.

  • Rapid repair: 
    Direct application of material at damaged area in near net shape.

Expansion of design possibilities: unprecedented weight and strength properties

  • The design is less restricted by manufacturing and material if a structure can be sliced into layers. This enables unprecedented weight and strength properties:3D printing of metals enables unusual or complex geometries, maintaining stability while decreasing weight. Examples are: inner structures like load-optimized, bionic architectures (honeycombs) or inner channels for cooling fluids. Parts can be manufactured as one piece instead of as an assembly of components.

Near net-shape manufacturing of components and reduction of waste and energy consumption

  • 3D printing creates near net-shapes layer-by-layer with a minimum of excessive material and has a double impact on the environmental footprint.

  • Direct impact in production: when considering the complete process chain, 3D printing is directly building up structures and saves energy. Furthermore, only the essential structures are built. This reduces the post-processing as well as waste.

  • Indirect impact in usage of 3D printed parts: these parts can be significantly light-weighted vs. conventially produced parts. For vehicles and aircrafts, weight reduction minimizes energy consumption. At the end of its life cycle a 3D printed part leaves less material to recycle or to dump.

Additive Manufacturing – Systems & Options

Different technologies in vacuum for optimized additive manufacturing

Powder Bed Fusion

A beam source melts defined areas of a metal powder bed.
Layers are build by applying selective laser sintering principle and deposition modeling.

Deposition rates: 50 – 150 cm³/h
(depending on material and beam power)

Wire-feed Energy Deposition

Layers are built by either laser or electron beam controlled melting of a wire based on deposition modeling. 

Depending on material and beam power, following deposition rates can be achieved:

  • Laser beam: 200 – 500 cm³/h
  • Electron beam: 500 – 1500 cm³/h

Diffusion Bonding

Material is heated to 60% – 90% of the lower melting material in a vacuum and mechanical pressure (≈10N/mm2) is applied to bond material sheets together.