Rise all: Need a strong AM system

Additive Manufacturing (AM), better known as 3D printing, or producing a product by adding material layer-by-layer, is currently at a technological and economic inflection point. AM offers tremendous advantages in terms of design freedom, on-demand production and low development lead time, while avoiding traditional processes such as cutting, milling, grinding and welding.

In AM, you can design a product any which way you want. For example, if you want a cooling channel in a die , in conventional manufacture you can only drill a straight hole, but not, say, a helical channel. With AM, you can.

Aerospace and bio-medical sectors were early adopters of AM. Titanium alloys are extensively used in the aerospace industry; the components require substantial machining, but these alloys are difficult to machine. AM resolves challenges of machining and wastage of expensive material. In the biomedical implant sector, AM helps in customisation as per patient requirements by realising the part needed directly from a scan, that too in a very short time.

However, many aspects of AM are not yet well understood and hence there are challenges. For example, AM will only enable building of required geometries but not always a metallurgically and functionally qualified component. The realisation of additive manufactured components requires a concerted effort through the whole value chain of design for AM, building strategies for complex shapes, metallurgical homogeneity of properties, post-processing, testing, and qualification application.

Second, most of the AM machinery manufacturers are foreign companies and they insist on using their proprietary powders. So, consumables are expensive, hampering the adoption of AM. AM is also a slower and more expensive process, compared with traditional mass production techniques.

As such, intensive R&D efforts are required in some key areas such as the use of multiple lasers, hybrid methods, automation for powder handling and recycling for powder bed fusion systems.

Yet another challenge is of the inhomogeneity that sets in when you add layer upon layer. When a metal part is built additively by powder bed fusion technique, a laser beam is scanned in multiple passes on a powder bed as per the required profile in the given layer resulting in melting and solidification of the metal in its path. Thus, the layer is formed. The powder bed is lowered and a fresh layer of powder is spread. The laser melting process repeats until the part building is completed.

Now, by the very nature of the process in addition to the formation of defects as in a welding process, each layer experiences a different thermal history leading to inhomogeneous microstructure and mechanical properties in the horizontal plane.

Inhomogeneity is a challenge but it can be tackled by methods such as pre-heating, post-heat treatment and part build orientation in a direction favourable to service conditions.

There are two major ways of carrying out laser assisted AM. One is ‘selective laser melting’ (SLM), which uses a laser beam to melt metal powder. The other method is ‘direct energy deposition’, where the material, either in the form of powder or wire, is fed into an energy source. The deposition head moves along the prescribed path. Currently, SLM is more popular in metal AM. All these techniques need to be mastered for a widespread adoption of AM.

In India, AM technology is in its infancy. The Indian AM market is expected to grow to $79 million this year, Significant work still needs to be done to develop new materials and understand how various process parameters affect the part quality.

Further, since most of the machines and raw materials are imported, AM is more expensive than conventional manufacturing techniques such as CNC machining and injection molding.

Service providers in India are limited, and most are not equipped with competitive AM and relevant supporting technologies compatible with plastic, metal, and ceramic materials all under one roof. The AM ecosystem needs to develop by aggregating all service providers on a single platform.

There are about 15 active R&D and industrial organisations engaged in AM technology in India. But most of them are working on metal AM. These include ARCI, Hyderabad, RRCAT Indore, CMTI Bengaluru, IIT Bombay, CSIR-CMERI Durgapur, CSIR-CECRI Karaikudi and IIT Hyderabad.

ARCI started AM four years ago by setting up an SLM facility. Since then, applications have been developed using a wide range of metals and alloys including stainless steels, aluminum alloys and Ni-based super-alloys. The possibility of creating complex and fine geometries in a short time enabled not only better functionality of the objects but also light- weighting.

Considering the need for indigenous sources of powders and the availability of in-house capability to produce through the gas atomisation route, several Ni-based alloy powders have been produced and tested for AM friendliness.

The potential of this technology is huge. To keep pace with rapid global manufacturing prowess, India needs to adopt an integrated approach to AM in all segments, including strategic and public sectors. The creation of a centralised facility as a hub and the R&D domains as spokes in a consortium mode can be an effective model for the launch of a National Initiative for positioning India at the forefront of development and adoption of AM. Such a mechanism not only promotes R&D but also acts as a translational research centre and enables the evolution of a strong ecosystem for fast adoption of this disruptive technology.

[The author is Director, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad]

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