Is laser additive manufacturing production ready?
Several structural components arranged on a base plate after a selective laser melting process. (Image: Fraunhofer EMI)
News from AILU - The Association of Industrial Laser Users
Dave MacLellan, executive director of AILU, asks whether additive manufacturing is ready for wide-scale implementation in volume manufacturing.
Additive manufacturing, or 3D printing with metals using lasers, has been a rapidly growing technology where the global market is roughly doubling in size every three years. In spite of successful growth and breakthroughs in performance, has the technology moved on from rapid prototyping to rapid manufacturing? This technology has really taken off in low-volume and high-value markets, such as autosport, orthopaedics and aerospace, but is it now ready for wide-scale implementation in volume manufacturing? To answer these questions, several parameters need to be considered, and AILU is running a workshop on 3 October (details below) where those seeking the answers can learn more from experts first hand.
Which method to use – DED or SLM?
There are two main methods in use, although each one is supplied with multiple acronyms. Both methods share a distinct advantage compared to ‘machining from solid’, that the efficiency of the process – producing a near net shape with minimum scrap material – is higher, providing a shorter manufacturing cycle and lower material cost.
In the first method the laser beam melts material supplied into the laser beam by a powder or wire feeder – we will choose to call this Directed Energy Deposition (DED). This method potentially allows for greater build speed and lesser finished component resolution (unless finished by final machining).
In the second method, which is perhaps getting more exposure from the machinery vendors, the laser is scanned across a bed of powder to melt/fuse a slice of a 3D CAD model one layer at a time – let’s choose to call this Selective Laser Melting (SLM). This method – with smaller spot sizes and fine powder diameters than DED – can achieve a better resolution and the surface finish can require limited post-process machining. This process has limitations on component size, due to the practicalities of powder chambers and scanning areas. Recycling of unused powder is also a feature of this method.
What materials can be used?
In both processes, it is necessary to consider the availability of the material in wire or powder form. Stainless steels and tool steels are routinely used, as well as titanium and aluminium alloys in medical and aerospace applications.
Some materials are pyrophoric (they ignite easily when coming into contact with air). In particular this is an issue when considering SLM: in fine powder form, materials like aluminium, titanium and magnesium, which are highly valued for lightweight designs, are also highly flammable in powder form, so it is essential to have the right handling processes in place. The range of new alloys becoming available continues to increase.
How fast and how big?
The economics of manufacturing requires continual improvements in the cycle time, to allow 3D structures to be built at commercially viable speeds and cost. Fibre laser development continues to provide higher powers and by combining several laser sources – several machine builders integrate four lasers in one machine – a combination of speed and precision can be achieved. Current size limits for SLM are typically less than 0.5m3, possibly extending to 800mm in one axis. Build times with SLM are usually in the tens of hours, although it is possible to make a large number of smaller parts in one batch. With DED there are far fewer limitations to the overall size of parts that can be built.
What about the human interface?
As with any rapidly developing technology, the usability of machines is important and software is needed to make the set-up of systems more automated. The fourth industrial revolution requires machinery to both work more efficiently and to minimise the tasks that the human operator must carry out. Many suppliers are therefore integrating modular loading and unloading to improve throughput.
What about validation and certification?
As 3D additive manufacturing takes over a production role – as opposed to prototyping – it becomes necessary to validate the components produced to make sure that they are consistent in geometry and quality. The possibility of material contamination needs to be prevented, therefore non-destructive testing and analysis is required, along with extensive machinery and material build trials to ensure the consistency of metallurgy. Aerospace, nuclear, automotive and medical markets need safety-critical certification to be confident that the process will work and reduce the risk of part failures.
Find out more
AILU is running a one-day workshop near Sheffield, UK, on 3 October to explore the issues raised above, entitled: Laser Additive Manufacturing: Overcoming the Barriers to Wider Adoption.
More details from www.ailu.org.uk/events or by calling +44 1235 539595.
Adding up in Aachen - Matthew Dale reports from the International Laser Technology Congress, AKL, where the potential for using additive manufacturing in series production was discussed