When TCT spoke to Friend Vancraen on the Additive Insight podcast back in April, the Materialise CEO and founder described his pride in centring the company’s early mission statement on using 3D printing to create a better and a healthier world. He said: “We see this just as an extension of an evolution we have been in already for a long time because sustainability is now another word to define that better and healthier world."
Proving this was not just another platitude on the industry’s looming issue, the Belgian additive manufacturing leader has announced the development of a selective laser sintering-based process and material innovation called Bluesint, which makes it possible to 3D print with up to 100% re-used powder.
“The story of Bluesint starts almost 7 years ago, when we experimented with a CT scan to get very detailed impressions of our SLS prints,” Jurgen Laudus, VP & General Manager, Materialise Manufacturing told TCT. “The CT scan revealed very minor irregularities in the printed objects. Irregularities that weren’t visible to the naked eye and that we weren’t able to see before. The next step was to figure out what caused these irregularities. Slowly but surely we gained more insight about the process behind this and we learned what buttons we had to turn to impact the outcome. Once we were able to apply these insights to actually control the process, we decided to use these insights to address the issue of powder waste.”
The process has been engineered to overcome the so-called “orange peel” effect, a surface texture problem often found in laser sintered parts produced with only used powder from previous print jobs. The effect is caused by shrinking which occurs when the powder cools down between two consecutive sintering processes. Currently, the answer is a mix of used and virgin powder, but Laudus notes how this option is simply not sustainable.
With laser sintering, the second most commonly used 3D printing technology, up to 50% of the powder becomes waste,” Laudus explained. “The potential to recycle the used powder is limited and 3D printing with only used powder creates surface problems that make the 3D printed object unsuitable for most applications. That’s why manufacturers mix used powder with fresh powder, commonly in a 50/50 ratio. This makes the SLS print process not only more costly but it also creates a lot of waste. With our ability to better understand and control the 3D printing process, we knew this represented a great opportunity.”
Bluesint PA12 part printed with 100% re-used powder.
Bluesint works by controlling two lasers within the printer, one for sintering the powder, and a second to keep the powder above a certain temperature. This prevents it from cooling down between two layers, and as a result, eliminates the dreaded shrinking process. This breakthrough, Materialise claims, delivers 100% recycled parts featuring similar mechanical and visual properties to those printed with fresh powder.
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“As we gained a better understanding and control of the various printing parameters we were able to manipulate the process,” Laudus said, elaborating on the multi-laser technique. “There are two options: applying a local pre-heating before the actual sintering pass or applying a local post-heating after the actual sintering pass. Local means that it needs to be done by the laser and locally only where material needs to be sintered. Heating means that the energy delivered is not enough to melt the material, but just to pre-heat or post-heat.
“By preventing the powder to cool down, we can prevent the shrinking process that causes a deformation of the surface."
Just how sustainable is additive manufacturing?
As we explored in a recent issue of TCT, sustainability continues to stir up debate in the additive manufacturing sector as manufacturers and end-users question whether the process, long perceived as intrinsically more sustainable than traditional manufacturing methods, is in fact as green as we think. In a recent survey presented to Chinese manufacturers by Materialise, 85% of those asked said they believe this to be the case.
“This confirms a general consensus that AM is a sustainable manufacturing technology,” Laudus said. “But a recent LCA indicates that for large series of identical products, 3D printing is currently not the most sustainable choice. These kinds of studies are important to avoid greenwashing and substantiate what we do.”
Laudus does, however, believe we may need to cut AM some slack: “On the other hand, we need to give AM some credit: ‘young’ standard manufacturing technologies such as injection moulding have been optimised for production for over 75 years. 3D printing has been used in a production context for hardly 20 years. Moving forward, the question is not whether AM is a sustainable manufacturing technology, the question becomes: “what can we do to make AM more sustainable?””
Parts produced via the Bluesint method are said to boast similar mechanical properties to a standard PA12.
Materialise recently participated in a Lifecycle Analysis (LCA) study in partnership with BASF based on the series production of one million pairs of 3D printed midsoles to determine the environmental impact throughout the product’s life. When comparing data from three different 3D printing technologies and conventional polyurethane casting, every time additive was found to have a bigger impact on climate change and depletion of fossil fuels. While bucking the belief that AM is naturally more sustainable, Materialise recognises additive’s other unique advantages, such as the ability to customise products or bring smaller series production closer to the point of demand, could help balance its environmental impact.
Meanwhile, exploration of Bluesint is ongoing and Materialise intends to onboard select customers to a beta programme and load up several machines throughout next year with the powder to meet some serious material recycling ambitions.
“In the next few months we plan to run several laser sintering machines with Bluesint PA12," Laudus said.
"In this start-up phase alone we aim to re-use more than five tons of powder that would normally become waste. In addition we have created a beta programme for the Bluesint PA12 service and invite selected customers with diverse applications and a focus on sustainability to participate in the market validation process of the new technology. This beta programme will teach us which objects and which applications our customers choose to run with Bluesint PA12.”
