3D printing is creating a whole new world for design engineers, enabling rapid creation of functional prototypes and end use parts. However, as The Manufacturer editorial team found out on a trip to 3D printing services provider Materialise, in Leuven, Belgium, it is far from a one-size-fits-all technology.
Additive manufacturing, to give 3D printing its proper title, is a multi-faceted technology involving a myriad of processes, techniques and materials (including metal, plastic and ceramics), each suited to different functions and end use applications.
Not only that, but those end uses for the technology are also becoming more varied. In the past, 3D printing was the sole domain of rapid prototyping. Now, more than 50% of the parts printed by Materialise are for end use. Here, we look at some of the technologies available to manufacturers thinking of introducing 3D printing into their processes.
Metal 3D Printing/SLM
Metal 3D printing, or selective laser melting (SLM), combines the design flexibility of 3D printing with the mechanical properties of high-performance metal alloys to create unique, strong and lightweight parts.
In the process, laser beams heat and fuse selected parts of the upper layer of a metal powder with underlying areas that are already solid. Once a layer is complete, the metal powder bed is lowered by one layer width and a new powder layer is applied – the laser then fuses selected areas of the metal powder again. By continuously repeating these steps, the component with its support structures is created layer by layer.
The supports are of great importance in SLM because they not only hold the component in position, but also absorb internal stresses, dissipate heat and thus prevent deformation and other construction errors.
The strengths of SLM lie in the combination of the design freedom of 3D printing with the material properties of the various metals that can be used. The technology makes it possible to implement highly complex geometries in a single component.
This makes it possible to create lightweight structures that bring major benefits not only to car manufacturing and aerospace, but also to all other applications in which parts are frequently accelerated and decelerated. SLM production can be useful for many end products, especially if they are required individually or in small batches. These include production tools, moulds and inserts, but also spare parts.
Multi Jet Fusion (MJF)
The fast build time offered by MJF provides an attractive alternative to injection moulding. With no support structures needed and surfaces that require minimal post-processing, this technology is well suited for functional prototypes and small series of even complex end use parts.
Although it is based on powder as the printing material, it does not use lasers. Instead, it uses two liquids as well as infrared light. The powder bed in the build area is heated evenly at the beginning, and the individual powder layers are applied stepby- step.
Due to this process, MJF offers good timing predictability; since the melting process is not based on laser movement, which varies depending on the area to be exposed, the printing process takes exactly the same time for each layer. This means that the printing time can be precisely predicted. Therefore, users can benefit from shorter lead times and the ability to produce more components of sufficient quality in one build job.
The strengths of components produced by MJF result from the fine-grained nature of the powder used. It enables ultra-thin layers of 80μm which produce components with higher density and low porosity when printed.
Fused Deposition Modelling (FDM)
FDM, also known as Fused Filament Fabrication (FFF), is one of the most popular 3D printing processes for the additive manufacturing of plastic components. FDM is based on thermoplastic modelling filament, which is meltable plastic provided in wire form on rolls. The filament is fed through an extruder nozzle, where the material is heated and then applied in layers to the required areas on a build platform. Once all areas of a layer have been applied, the nozzle is moved up and the next layer is printed on top of the one below.
FDM combines 3D printing’s design freedom and fast lead times with production-grade thermoplastics to create durable parts with excellent mechanical properties. FDM is a 3D printing process that can be used to create almost any geometry with particularly low distortion, as no thermal stresses are introduced into the component since heating is only carried out at specific points. In principle, the construction dimensions are unlimited, as the components can consist of different segments that can be joined together very easily after printing.
One of the major advantages of the process is that the mechanical properties of materials that can be used with FDM remain stable over time. As a result, the components are not only of high quality, but also last an exceptionally long time.
Selective Laser Sintering
Laser sintering is a popular and versatile 3D printing technology thanks to its high precision, design freedom and wide range of production-grade materials. Suitable for all stages of the production lifecycle, from prototyping to small series or custom manufacturing, laser sintered parts need no support structures, making it possible to produce even the most complex geometries.
In laser sintering, plastic powder is distributed over the entire surface of a build platform using a roller or squeegee and then selectively bonded by melting with a high-power laser beam. Once the laser has completely processed the first layer, the platform lowers, and a new layer of powder is applied. The laser now melts the areas defined in this layer. This procedure is continually repeated, gradually creating the component.
One of the advantages of SLS is that no support structures are required, since overhanging structures are stabilised in the powder bed. As a result, any three-dimensional geometries can be created. These can have undercuts that cannot be produced in conventional mechanical or casting manufacturing. The process can also be used to create highly complex designs such as moving parts, hinges and chains in a single piece, which saves subsequent assembly steps or enables completely new design solutions and applications.
Another strength of laser sintering is that several independent components can be printed simultaneously in the build space. By strategically arranging the parts (nesting), the available build space in each machine can be optimally utilised, which makes the production of small series or different prototype variants, for example, relatively fast and cost-effective.
Stereolithography is one of the most widely used 3D printing technologies. Its surface quality, ability to produce fine details, and wide selection of materials make it well suited for highquality visual models and prototypes, complex aesthetic parts, and masters for techniques like vacuum casting and lost wax casting.
The basic version of the technology is based on UV sensitive liquid resins that are applied to a platform and then selectively cured by laser beam, from which different variants have evolved over time. During the manufacturing process, the platform gradually lowers and the component grows layer by layer. To prevent the printed object from moving in the resin bath, it is fixed to the build platform by means of support structures.
The strengths of SLA lie in the combination of very high dimensional accuracy, high surface quality and relatively short production times. Furthermore, apart from Polyjet, SLA is the only additive manufacturing technology that can also be used to create transparent objects. Stereolithography can also be used to produce large components in one piece.
In addition to its high detail and smooth surfaces, PolyJet offers the unique ability to print precision parts and assemblies with multiple materials, all in a single build. A single part can contain different colours, levels of transparency, and diverse physical and mechanical properties, making PolyJet well suited for complex visual models and prototypes.
In the process, photopolymer resins are applied in ultrathin layers to a build platform via print heads – similar to inkjet printers – and cured immediately after application using UV light. For complicated geometries and overhangs, a gel-like, water-soluble support material is also applied via the print head. Once a layer is complete, the platform moves down by one layer thickness and the next layer follows.
PolyJet printers have several print heads which allow different materials and different colours to be combined during printing. As a result, not only can specific colours and hardness be achieved, but a component with several colours and different mechanical properties can also be produced in a single printing process.
Another special feature of the polyjet process is that the light transmission of the material can be varied. Even complete transparency is possible. Furthermore, the technology enables the printing of very fine details, as the layers are only 32μm thick.
Jurgen Laudus (below), Vice President, Manufacturing Segment and Bart van der Schueren (bottom), CTO, Materialise, discuss the current trends within the additive manufacturing space.
How is the use of 3D printing changing?
BvS: As we know, the first use cases for 3D printing were in the field of prototyping. The most important evolution we’ve seen is customers are now looking to use the technology to make end use parts.
If you look at the production of implants as a typical example of an end use part, because additive manufacturing doesn’t require any product specific tooling, we can make huge advancements in mass personalisation. Plus, there is also a growing trend towards smaller series sizes which also lends itself well to additive manufacturing.
JL: More than 50% of the parts we print are for end use applications. Therefore, we are putting a lot of effort into the process control of 3D printing. We collect a lot of data from the printers and from post-processing, for example, and bringing all this data together has helped the industry to have a better understanding of what is happening in the machine and has enabled us to develop end use part applications.
A key difference from prototyping is that safety needs to be guaranteed for end use parts, particularly in highly regulated sectors such as aerospace and medical (where many of our products end up) – plus you need to ensure that the material and part characteristics are the same, day-to-day and year-to-year. You need repeatable production and data has been key to the evolution of the technology beyond merely prototyping.
BvS: 3D printing by nature has always been a digital technology, but for many years it has been isolated. That is something which is changing rapidly; that post-processing phase is undergoing a digital transformation and that fits into the general trends of Industry 4.0 where conventional manufacturing technologies are becoming more digitised. What that means today is additive manufacturing is no longer a siloed technology, but rather one of the steps in a larger production chain. And that is something that is enabled by digital technologies.
What advantages can 3D printing bring to help manufacturers navigate recent challenges?
BvS: There has been all manner of challenges over the last few years which have made manufacturers ask how to make production more resilient, and additive manufacturing certainly has a role to play. That is something manufacturers have learned from the COVID crisis, for example, where supply chains were suddenly broken.
Here, additive manufacturing showed that parts and components could be manufactured on-demand, where they are needed. That kind of change in the market, which was initiated during COVID, has been picked up by manufacturers to further mitigate against supply chain uncertainty. Moving towards additive manufacturing can increase resilience, because it helps companies to have a level of production capacity near to where they need parts.
This local production allows product development to be looked at in a completely different way. Parts can be produced and optimised immediately and manufacturers can even go into agile development and involve customers to really develop products that perform as required. This means that manufacturers can get to market quicker and at less cost, while also having a digital asset of the product to fall back on should there be further disturbances in the supply chain.
JL: We’ve seen a dramatic rise in manufacturers wanting to talk to us over the last few years because of the issues they are experiencing within their supply chains. Many have a huge inventory of stock lying around just in case there’s further disruption. We can greatly reduce the number of stock items thanks to a digital inventory where, if a manufacturer needs a part, they can simply print one.
Manufacturers have become aware that the supply chain should not be taken for granted; that not all parts which are produced on the other side of the world can be here in a matter of days or weeks. That has created a lot of interest for 3D printing and a growing number of manufacturers now want to see what the technology has to offer.
What benefits can 3D printing provide manufacturing?
JL: Firstly, you don’t need to make a mould, which eliminates the start-up costs typically associated with traditional manufacturing methods. Secondly, there is more freedom, enabling the design of parts to become far more complex without extra cost. And thirdly, parts can be produced more locally, minimising supply chain disruption.
More and more manufacturers are starting to become aware of these benefits. However, while some manufacturers have an idea of where they want to get to, others are struggling with knowing where to start.
As discussed, there is a wide landscape of technology and materials available, so what should manufacturers look at first? And how do they ensure that 3D printing provides them with the same outcome (or better) as they received from traditional manufacturing methods?
That’s why we believe our Mindware offering is so important. It shows manufacturers how to use technology in the best way; what are the right applications and parts to start with that involve taking the least risk. We help our customers get on the journey.
BvS: Technological evolution has made 3D printers far easier to use, and there are more materials available so manufacturers have more choice. In addition, the digital process is becoming more developed, and that is important because additive manufacturing is still a technology which is in its infancy.
There are still a lot of unknowns but by digitising the whole process, collecting data on the machine and making it available, it helps end users to better understand how the process is working and what you need to do to keep your production process stable. That is an important step towards mid-size volume production for additive manufacturing.
There are also environmental benefits. Additive manufacturing is not necessarily environmentally friendly per se, because a lot of energy is required to make the raw materials and to create the actual parts.
However, as discussed, producing parts where you need them is a feature of additive manufacturing, but this also has an environmental advantage. Most people don’t realise how many spare parts are produced. These are filling up warehouses and are often never used. 3D printing can mean on-demand production; manufacturers don’t have to go into overproduction and produce spare parts, and so the inventory risk is reduced.
In addition, additive manufacturing can provide weight savings. This is important for anything that features moving parts, because movement needs energy. So, the lighter the parts, the less energy required, and the better that product is for the environment.
What will be the role 3D printing in the future of manufacturing?
BvS: I’m convinced that additive manufacturing will become an integral part of the production chain. The freedom of production allowed by additive manufacturing enables the combination of more functions in a single component. That means you can save on assembly costs and create complex parts which couldn’t be produced with conventional technologies. Additive manufacturing is really growing into an established production technology.
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