Stratasys Turns Waste Powder into Parts with SAF Sustainability Upgrade

3D printing has been touted for over a decade as a “green” manufacturing technology.  Using a layer-wiser approach to produce a part, material can be saved.  Allowing for geometrically complex and lighter components can minimize energy demands in a larger system. Manufacturing small batches or individual components eliminates part waste.  Printing items where needed cuts down on transport and the associated fuel consumption.  These strategies are numerous and vary in efficacy from considerable to theatrical.

One often neglected consideration when evaluating additive’s green credentials, however, is material waste within the process itself, and it is this that Stratasys (Nasdaq: SSYS) is tackling head on with its Selective Absorption Fusion platform (SAF).

The Problem with Powder 3D Printing Waste

Among 3D printing technologies, polymer powder bed systems in particular are prone to generating significant amounts of waste due to a requirement known as the “refresh rate.” This refers to the fact that non-sintered powder, which has already gone through a print cycle, can only be reused a limited number of times. After this threshold, the material can no longer be consolidated effectively by the printer. To maintain print quality, a portion of the used powder must be mixed with virgin material, often up to 50%. The rest is disposed of, contributing to waste.

Currently, this discarded material is factored into the economics of powder bed printing. However, with the average cost of nylon powder at $50/kg, the cumulative financial burden for companies using the technology at scale can be substantial, reaching six figures annually due to material waste alone.

More troubling is the environmental impact. The production of 1 kg of nylon powder generates approximately 8 kg of CO2e. According to Additive Manufacturing Research, the total nylon powder shipment in 2023 was 6.3k metric tonnes, which corresponds to 50k metric tonnes of CO2e emissions—equivalent to 12,000 cars driving 10,000 miles each. Given that an average of 25% of this material is wasted, the pressure to reduce both economic and environmental costs becomes clear.

Stratasys has recognized this issue as an opportunity for innovation. Through its SAF platform, the company has introduced a solution that could dramatically recycle waste, leveraging unique design elements and an advanced infrared (IR) fusing strategy. This differs from the Multi Jet Fusion (MJF) process by HP, and it holds potential to significantly recycle powder waste.

How SAF Turns Waste into Parts

As powder undergoes multiple print cycles, its molecular structure changes. Chain elongation, as well as increases in molecular weight, minor oxidation, and alterations in particle morphology all affect the powder’s behavior. In particular, aged powder shrinks more, and has reduced mechanical properties after printing. This can cause quality issues, especially in systems like laser sintering or MJF, where the time between heat cycles is not uniform across the print bed, which can produce issues with the printed parts.

However, SAF overcomes this challenge with a crucial architectural difference: it uses a unidirectional print carriage, unlike MJF, which relies on two carriages moving in perpendicular  directions. This means that, in SAF systems, every position on the build bed experiences the same amount of time between recoating, heating, and cooling. The result is consistent thermal input, leading to uniform shrinkage.

Because of this higher degree of control over the thermal environment, SAF can effectively consolidate waste nylon powder that competing technologies were sending to landfill.

Making 3D Printing Greener and Cheaper

In practice, Stratasys’s SAF platform offers two benefits. First, users of SAF systems will experience a lower material waste factor, reducing their overall material costs. More compellingly, however, the SAF system can repurpose waste powder from other powder bed technologies, making it an ideal solution for companies looking to minimize their environmental footprint while maintaining production efficiency.

Several pilot customers, such as Wehl Green in Spain, having been producing production and tooling parts with reclaimed waste polymer powder from laser sintering printers and reporting positively on the surface finish and mechanical properties of printed parts.  With feedback from these pilot customers, Stratasys is confident that the SAF system, with its waste powder printing upgrade, could find and lockdown a unique niche in the market.

This project has been on-going internally for several years within Stratasys, and with additive manufacturing industry surveys increasingly stating sustainability as a high priority issue for 3D printing users, the company has moved to announce this new initiative this year at Formnext 2024, launching with the ability to print unfilled PA12 powders.