01/07/2020

Stability and Flexibility: A New Paradigm for eBeam Metal AM

The NeuBeam metal additive manufacturing process from Wayland Additive eliminates the trade-off many users have to navigate between stability and flexibility with their industrial metal applications.

Additive Manufacturing (AM) is no different to any other manufacturing process that relies on the interaction between a manufacturing system and the material of the product being manufactured. Wayland Additive understands this need from the user’s perspective and has made it its mission to develop a machine — from the ground up — that allows the user full, safe and accurate control of a metal AM process. The NeuBeam process from Wayland allows for an advanced machine architecture that presents a stable platform that does what it is asked to do, when it is asked to do but with great flexibility and control to accommodate the wide range of user applications.

Traditionally, stability and flexibility have not always comfortably complemented each other in the field of AM. Wayland Additive is operating to break this barrier down and when the team first closely reviewed additive processes (back in 2015) they were struck by the lack of stability, exhibited both in the machines and the output. With a background in electron beam (eBeam) systems the Wayland team reviewed the state-of-the-art and immediately set about removing the shackles from the eBeam process.

The physics of the process is fundamentally more favourable to AM in the following ways:

• kinetic energy transfer takes place between the electron beam and the powder
• extremely fast deflection speeds can be achieved as there are no mirrors to manipulate
• the incident power on the powder bed is easily measured and controlled
• there are no optical surfaces between the electron source and the powder bed to contaminate and deteriorate with time
• the process can run hot and so take place above the annealing temperature of the process material, resulting in stress free parts with less post processing
• the process takes place in a vacuum so powder contamination and oxidation is reduced and powder life extended
• in-process monitoring can take place using a range of photon and electron detectors and systems

Electrons have an inherent advantage over photons in that they are charged particles, which means that the beam can be deflected, focused and corrected very rapidly, without any physical contact, scattering or absorption. Within the context of AM to date, however, this has also proved to be a disadvantage. When charged particles are incident upon insulating materials, they tend to adhere and build up a surface charge. When this happens during the metal eBeam AM process (where the accelerating potential of the electrons is many thousands of volts and metal powders tend to have an insulating surface oxide layer) a considerable potential can build up on the powder bed, until the powder particles are caused by Coulomb forces to repel each other and a “smoke event” occurs. When this happens the particles become free flying within the chamber and the build is violently terminated, potentially to the detriment of the machine as well as the part(s).  This accumulation of charge occurs very rapidly and has to be managed throughout the build process in order for it to be reliably completed.

To date, the accepted way of overcoming this problem is to lightly sinter the powder together from the start of the build, layer by layer, across the entire surface of the build platform, with the consequence that the manufactured parts are encased in a block of sintered powder that needs to be blasted off.

NeuBeam Ensures Stability is Built-in

The NeuBeam process and the new Wayland system has been designed from the bottom up and incorporates many years’ of learning from the semiconductor industry — a hard task master. Quite simply, the machine is designed for production.

Without the need to pre-sinter and without the problem of powder charging, the NeuBeam process presents a new capability to the AM arsenal:

• It is stable, allowing the full range of AM powder sizes to be used while the build can still run above the annealing temperature of the material.
• It is clean: the “soot” problem present in laser systems requiring the cross flow of argon gas to prevent powder bed contamination does not exist. The process takes place under vacuum so there is less contamination of powder and therefore greater powder recyclability. The power delivery from the electron emitter to the powder bed is through free space and no contact with optics, which can become dirty.
• It is fast:electromagnetic deflection systems can move the beam at 1000s of meters per second. This fast deflection capability means higher beam powers can be used, which speeds up build times and ensures good control over the thermal process of the build.
• It is simple: build supports are minimal, thermal stresses do not need to be determined pre-build; powder freely flows out of the build, with only minor de-powdering needed; wire erosion is not needed to cut the build off the start plate; and post build heat treatments are not required.
• It is efficient: the build part is thermally isolated from its surrounding so less power is needed to keep the build temperature above the annealing temperature.
• It is adaptive: new materials can be rapidly developed; and in-process monitoring enables near real time process control.

In short, NeuBeam offers a manufacturing process that is both stable and flexible.