If 3D printing were a human being, it will be on the verge of adulthood. All the broad outlines are already there, but it might well still have some surprises up its sleeves. Here we take a look at the key trends. By Dr. Thomas Fehn, General Manager Additive Manufacturing, Trumpf.
3D printing is on everyone’s lips, but the term has come to mean very different things to different people – or perhaps it always did. In the case of metal 3D printing, new methods seem to be taking root on an almost annual basis. The idea of constructing parts layer by layer in a powder bed has inspired numerous engineers and developers. Three methods that have already become well established are laser metal fusion (LMF), electron beam melting and binder jetting. They share the limelight with the nozzle-based method of laser metal deposition (LMD) – another additive manufacturing (AM) process – as well as wire-based methods that are also classified as LMD. Measured by market share, LMF and LMD are currently the top AM methods for producing metal parts. But ask “What’s the best method for me?”, and there is unlikely to be an easy answer, because each method has its ups and downs. For example, LMF may be the best option for producing parts with delicate structures at the highest level of quality, but binder jetting can do the job between 10 and a hundred times faster.
If 3D printing were a human being, it would arguably be a gifted 17-year-old. The broad strokes of the teenager’s personality and talents are already visible. The parents can hazard a guess at which direction their offspring is likely to take but, however much the teenager tries to act cool, there is still much they need to learn. Yet so much has already been achieved: the child has learned to walk and talk, read and do math. They have already done their first part-time job and been praised for their efforts, and now they are busy cramming for their high school diploma. There’s something in the air, a sense of freedom and independence, a new dawn.
3D printing is at a similar stage. Engineers and universities are continuing to probe and develop new ways of using the technology. Yet 3D printers have also been in fully fledged industrial use for many years, especially in pioneering sectors such as the aerospace industry.
The teething troubles that dogged it in the early stages – especially with regard to the reproducibility and robustness of the process – have been left behind, conquered by the machine-makers’ skills. 3D printers are gaining ground on the shop floor and ready for industrial use.
More and more business people see the technology making inroads into their industry and are seriously considering jumping on board before their competitors take the plunge. But what are the key trends they should take into account before making their decision?
The Pros And Cons Of Multiple Lasers
The first thing to consider is the build chamber. In principle, it’s true that the more lasers you have in a 3D printer, the faster you can build parts.
This simple equation has fuelled the commercialisation of multi-laser machines with two, three or even more lasers. Unfortunately, however, it’s not that simple, because there are all sorts of other factors that play a role, too. One of the keys to boosting the productivity of 3D printing is to find the optimum combination of scan field, scan speed, temperature adjustment, temperature field, build speed, and gas flow in the work area. The number of lasers and their power output is just one factor among many – though it is certainly one of the most expensive of all the factors involved.
In some cases, a fourth laser can increase the cost of the system by 25 percent while only increasing productivity by a decidedly modest two percent. Often it can be more profitable to start with seemingly less trendy components of the machine such as the build chamber heating system. A smart heating concept is worth its weight in gold because it keeps the printing process stable and increases overall productivity.
Some multi-laser machines with large build chambers promise to speed up the job of producing bulky parts with the argument that two lasers can build the rear portion of the part while the others focus on the front. That also seems sensible at first glance. But the crucial question is what happens in borderline areas. If the lasers’ scan areas are too far apart – in other words if there is not enough overlap between their work areas – then the part ends up with non-homogenous sections and ugly seams. During use, these often mutate into unwanted, yet effectively predetermined, breaking points. What this comes down to is that you can’t identify a highly productive 3D printer by the number of lasers it has, but only by its overall design.
Another aspect of the trend toward multiple elements is the idea of combining 3D printing with other machining methods in a single machine, for example with milling and drilling. Unfortunately, that typically ends up transforming the unquestionable marvels of 3D printing into an annoying drag on the other built-in processes. The reality is that the expensive, integrated milling cutter spends half the day waiting around idly for the 3D printer to reach a certain stage in the build process. Then it leaps into action for two minutes, before returning to its slumber for the remainder of the day. No production planner with any sense would install a high-end milling machine on the shop floor if it was hardly ever going to be used.
Right now – and even in the longer term – the difference in processing speeds between 3D printing and traditional methods is simply too great to offer any good reason for combining them in the same machine. That is no longer the case for other additive manufacturing methods, however, such as laser metal deposition.
A Broader Perspective
However important it may be to ask “How many lasers does the part need?”, it brings into focus a perspective that has traditionally, and understandably, been very narrow. For years, everyone was fixated on the build chamber. Just like with any new method, engineers initially focused on how they could get the process under control and make it faster. And they succeeded: Over the past five years, they have managed to increase the productivity of the LMF process by a factor of three – a truly remarkable achievement in such a short space of time, and a trend that is likely to continue for some time to come.
But the time has now come to adopt a wider perspective by focusing on the upstream and downstream stages of the process. These include unpacking the powder, refilling the machine, sieving the powder and checking it is mixed correctly, as well as blowing or shaking off excess powder, removing parts from the build plate, removing any supports they may contain, and carrying out finishing work on the surface. That’s where some of the greatest potential lies to accelerate and possibly automate individual steps, for example through powder management.
An automatic, self-contained powder handling system is also an appropriate response to occupational health and safety issues, which play a bigger role in the broader industrial environment than they used to. The problem here lies in the metal powder itself, which poses a health risk and should not, under any circumstances, be inhaled. Currently, however, only the biggest companies are opting for the most complete automation solutions for production integration.
In contrast, traditional job shops generally prefer to operate their 3D printer in isolation, rather than incorporating it directly in other production processes.
But however big or small their business, all 3D aficionados have a shared enthusiasm for good software. New concepts are opening the door to a self-contained software process chain without any frustrating interfaces – a chain that stretches from CAD data modelling right through to finishing work.
Apropos these post-processing stages: the supports required by the first generation of 3D parts once formed a magnificent bridge into the realm of this exciting new technology. They still have their uses today, but industrial-scale deployment has revealed their drawbacks by highlighting the increased cost and effort required during post-processing. This realisation is a great example of what industry needs right now: new ideas that cater specifically to 3D.
The visionary power of 3D printing has always stemmed from the design freedom it offers. Parts can be formed exclusively on the basis of their functionality – and nothing else. Yet the greatest advantage of 3D printing is, at the same time, its greatest challenge. One of the toughest tasks design engineers face is how to rethink existing parts and leave old conventions behind. Most part developers have learned to base their designs on the intended machining process, and in doing so they have assimilated a number of what they considered to be ‘golden rules,’ for example “You can’t drill around a corner”, “You can’t cast a cavity”, and so on.
Particularly in the early days of the 3D revolution, design engineers struggled to liberate themselves from this traditional mode of thinking. Many 3D printed parts greatly resembled their conventional counterparts. But now things have changed. More and more universities and apprenticeship schemes are teaching budding designers to think free form, with no inhibitions concerning the production process. Now the first of this new generation are graduating and looking for jobs.
Equally, some suppliers of 3D printing technologies responded quickly to the huge demand they saw in this area and began supporting their customers with training courses in free-form design. Unlimited design freedom is increasingly becoming a core component of training courses, especially in Germany and Switzerland. China, too, has seen which way the wind is blowing and is teaching its design engineers accordingly. The new generation of designers are likely to make fundamental changes to the shapes and forms of future parts.
At the same time, on the software front, design and simulation programs are improving all the time and automatically suggesting 3D-specific design options. All this will give industrial 3D printing even more of a boost – and that prompts the question of why the laser should only be melting metal.
Material diversity – a long underrated argument in the 3D printing debate – is now emerging as one of its most decisive strengths. Both LMF and binder jetting offer levels of flexibility in this respect that are quite simply beyond the scope of other methods. A huge array of metal powders are now commercially available. Users worldwide can acquire them quickly and easily, mixing them together to meet specific requirements. They include a class known as Inconel alloys, which can easily withstand temperatures in excess of 1,000 degrees Celsius in turbine blades. Equally impressive are the special alloys that allow parts to withstand extreme bending – alloys that can only be processed by 3D printers.
One of the key trends in 3D printing involves new functional materials that go beyond metals, because laser beams are also perfectly capable of melting other materials. Metallic glasses are one example: In the near future, we are likely to see high-grade optical components and mirrors coming out of 3D printers. Meanwhile, developers are currently working on ways to get ceramic powder into 3D printers – another material that is prompting a great deal of interest.
You Can Do It
The more sectors we see taking the plunge into 3D printing with their industry-specific requirements, the greater the variety of machines and production concepts that are likely to emerge.
Something that is good enough to meet the stringent quality standards of the aerospace industry is likely to be far too over-the-top for a moldmaker’s needs. This kind of differentiation is also compounded by the increasing wealth of available materials. Much of the road ahead is already clearly signposted, but there are bound to be a few surprises, too.
So here we have our 17-year-old, a gifted teenager striding proudly and boldly into the world of industry. The parents of 3D printing can finally sit back and relax, safe in the knowledge that their teenage prodigy can take it from here.
FOLLOW US ON: LinkedIn, Facebook, Twitter
READ MORE IN OUR LATEST ISSUE!
WANT MORE INSIDER NEWS? SUBSCRIBE TO OUR DIGITAL MAGAZINE NOW!