Advanced metal components through optimal combination of additive manufacturing and welding techniques

Context

Manufacturing parts using additive manufacturing techniques (AM) is becoming more and more common. There are already 18 (!) [1] different techniques commercially available for additive manufacturing of metal parts.

Among the different AM techniques, metal powder bed fusion (PBF) based AM processes are capable of fabricating metallic parts using many engineering alloy powders. Selective laser melting (LPDF = SLM [2]) and electron beam melting (EBM) are the most commonly used PBF based AM processes. In SLM processes, layers of metallic powders are selectively melted by using a laser beam, resulting in a printed solid part on a base plate. In EBM processes, instead of a laser beam, an electron beam is used as power source.

Metal injection moulding (MIM [3]) is a metalworking process in which finely-powdered metal is mixed with binder material to create a "feedstock", which is shaped and solidified using injection moulding. The moulding process allows high volume, complex parts to be shaped in a single step.

Directed Energy Deposition (DED [4]) uses a focused energy source, such as a laser or electron beam to melt the material. However, the material is melted at the same time as it is deposited by a nozzle. In a way, the technology is at the frontier of material extrusion and powder bed fusion.

WAAM is a variation of the DED technology and uses arc welding processes for 3D printing of metal parts. WAAM works by melting a metal wire using an electric arc as the heat source.

On the market, the powder bed technology (SLM, EBM), cladding (= DED), WAAM and MIM-based techniques are most present, each technique having its specific advantages and disadvantages. SLM is mainly used in medical, aerospace and tooling. However, metal printing in construction, mechanical engineering and mechanical design is lagging behind.

Example of a part printed with WAAM	Example of a part printed with the SLM technology

More information 

• [1] Technology overview metal Additive Manufacturing 
• [2] LBPF: Metal Laser Powder Bed Fusion
• [3] MIM: Metal Injection Moulding
• [4] DED: Direct Energy Deposition
• [5] SLM: Selective Laser Melting

Needs

An important issue that needs to be solved before the AM techniques can find a widespread use is the maximum dimensions of the components that can be produced. Nowadays, the dimensions of the final components are limited by the size of the workspace of the machine, and it is very difficult to produce machines with a bigger workspace. An intriguing solution to overcome this limitation is to join the additive manufactured parts in order to obtain bigger components.

The following topics need to be investigated:

• Which processes can be used to connect metal-printed parts to conventionally manufactured pieces?
• Guidelines for the optimal combination of conventional techniques and AM techniques.
• What are the consequences of the applied welding process for the (mechanical) properties of the parts and for the connection itself?