Mission:Build up

Selective laser melting and laser metal deposition are the two laser-based additive manufacturing methods. Here you can read about the current status of both methods.

Additive manufacture of metal parts in industry always involves building an object layer by layer, usually from powder and most frequently using a laser.

The method that has become synonymous with additive manufacturing in people’s minds and in the media looks like this: In a powder bed, a laser fuses metallic powder to form layers of material. The process occurs in a chamber flooded with inert gas. It is called selective laser melting (SLM) or powder bed fusion.

The process creates highly complex components with internal structures or components that are the image of their internal strains. Material is consolidated exactly where it is required to accept and conduct stresses.

Second career for LMD

Many components, however, do not have internal channels, cavities, and complex power flows. In addition, it is often favorable to apply additional material to existing components — adding a threaded mating surface to a pipe, for instance. In the past, a pipe would have been manufactured with a larger diametre than required and then everything except the connection would have been milled away. Or let’s say you wanted to change the surface geometry of a tool. In these cases, a different process becomes attractive.

Laser deposition welding, also known as laser metal deposition (LMD), inserts the filler material — powder or wire — directly into the melt pool formed by a laser beam, creating a layer of beads welded to each other.

The powder-based version is particularly promising, as it is 3D- capable: many layers build up to produce a body that — because the metal powder is supplied coaxially to the laser beam — can grow in every direction.

What makes deposition welding so exciting as a second additive process is not only the fact that the equipment technology is already fully developed and available, but — and more especially — the deposition volume and speed it can achieve.

With volumes of up to 500 cubic centimeters an hour, it beats conventional manufacturing processes not only from a technological perspective but often in terms of cost-effectiveness, too. And it imposes scarcely any restrictions on developers with respect to combining materials: it can produce almost any kind of sandwich structures and graded layers.

The process is carried out on the component in the ambient air. This reduces non-productive and setup times and means that even large components can be processed. All this reduces the costs per part.

Hopes and reality

Despite the huge potentials of additive manufacturing, skeptics point to many obstacles. The materials are still relatively expensive and the building an object layer by layer is very time consuming.

Heat input, melting times, cooling times, the volume that can be processed — all these things put limits on speed. And then there is the whole business of programming the process. Although the CAD model contains all the necessary data for the component, the machine still needs to be shown a path — fromOff White X Max 90