Over the last few years, there has been a significant growth in interest in 3D printing. It has moved from clever demonstrations of technical capability, producing objects impossible by conventional methods, to commercial usefulness. Initially used for the creation of one-off models and prototypes, it can now create production components in small runs.
At the same time, it has spread from the laboratory to amateur and consumer use. Uses range from the creation of precision one-off parts for astrophotography to highly accurate scale reproductions of objects for dolls houses.
3D printing has been widely discussed as a route to sustainability. People talk about using less material, reducing waste, increasing efficiency in manufacturing, and being able to manufacture where the product is needed, reducing transport costs and impacts.
I wanted to know more about where we are with 3D printing and sustainability, so I attended a breakfast meeting organised by the KTN and hosted by Croft Additive Manufacturing. I learned that 3D printing can make a significant contribution to sustainability, and particularly carbon emissions, but not in the way I thought.
What is 3D printing?
But first of all a step back. 3D printing involves building up a structure as a series of thin layers. It is also called additive manufacturing to distinguish it from subtractive manufacturing where you start with a block of material and the bits that are not needed are progressively carved away. Additive manufacturing can be done with a variety of materials, including plastics, metals and ceramics.
There are different ways to create the layers. If the material melts and flows, you can extrude it through a nozzle, a bit like a computer-controlled hotmelt glue gun. This is the method we are used to seeing with consumer 3D printing. Another approach is to make a thin layer of powder and use a high-power laser to fuse those areas which will be part of the final structure. Another layer of powder, more fusing, and you build up the object. This method is often used for metals and ceramics. There are now seven different ways of building up the layers; each of which is particularly useful for different materials and different objects.
Sustainability benefits
So back to that breakfast meeting. What was the opinion of the experts there? How can 3D printing help sustainability?
The material saving and waste reduction are real. More of the material used ends up in the final product. In the case of the powder fusing methods for metals, 95% – 98% of the un-fused powder can be recycled without further processing.
Against that, the preparation of materials for 3D printing can be more demanding, there may be a need for further processing to get the right finish for engineering applications, and not all raw materials can be recycled as easily as metal powders.
Because 3D printing is currently only suitable for small production runs, energy consumption in manufacturing is not yet a big win.
Distributed manufacturing is an intriguing concept, but given the diversity of materials and forms of the products we need, the idea of downloading a file and making a part on the spot is some way off.
Reducing impact in use by better design
The really exciting sustainability benefit comes from the ability to design and manufacture components that would be completely impossible using conventional methods.
You can create lightweight components that reduce energy consumption in use. A study in 2014 showed that using a 3D printed titanium aircraft bracket, instead of conventional cast steel, reduced aircraft weight by 10 kg and the lifetime emissions for the bracket by 40%. Where the lifetime emissions of a manufactured product are dominated by the use phase, lightweighting through redesign and 3D printing can have a big effect.
You can also win by pushing design towards an optimum, and beyond what you can achieve with conventional manufacturing. GE has invested in 3D printed injector nozzles for their LEAP jet engine. They were able to combine 20 parts into a single unit, reduce the weight by 25% and extend the life by a factor of five. The new design gives a 15% improvement in fuel efficiency for the engine. GE already has orders for over 12,000 engines. A substantial drop in emissions for the global air fleet.
OK, that’s for aerospace where manufacturers are always operating on the bleeding edge of manufacturing capability, and tiny improvements in efficiency are worth a great deal financially and in terms of environmental impact. What about more mundane applications?
That takes me right back to Croft Additive Manufacturing, the company that hosted the breakfast meeting. Croft’s main business is providing a wide range of filter solutions to industry. They have been working with additive manufacturing to allow them to create bespoke filters more cost-effectively. Whilst working on that, they had the idea of using 3D printing to change the orientation of the holes in a metal filter. Normally these are more or less at right angles to the metal shape of the filter. That means for a basket or cone-shaped filter the fluid is forced to suddenly change direction, wasting energy in turbulence and eddies. Supposing they could make sure the holes were in line with the fluid flow, irrespective of the shape of the filter? That would mean less turbulence and less energy consumption.
This would be impractical using conventional manufacturing techniques, but Croft has been able to do it with 3D printing. Their Straightliner Filter uses 10% less energy for pumping than a conventional filter. Across all the applications for fluid pumping, filtering and straining, there are some real energy savings to be made.
The key thing I learned about 3D printing and sustainability is that the biggest benefits come from using the ability to redesign products so that efficiency in use is dramatically improved.
Why was that a surprise to me? Because I forgot that when thinking about sustainability it is vital to look at the entire lifecycle, not just the obvious bits.