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.
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.
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.
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
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.
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 IH causes 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.
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.
High Vacuum: 5 x 10-4 mbar
Medium Vacuum: 5 x 10-2 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
The electron beam creates very deep and slender weld with minimized heat input and warpage of the workpiece.
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 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:
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.
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.
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.