Stratasys to Launch Production-Scale 3D Printing

Industry giant Stratasys is launching a promising new polymer additive manufacturing technology. Dubbed Selective Absorption Fusion, or SAF, this technology is the highlight of Stratasys’ new H Series Production Platform and is aimed at filling a gap in the additive manufacturing market for consistent, reliable part quality at production level throughput.

At its core, SAF is a type of powder bed fusion (PBF) additive manufacturing, with some unique twists. Professor Neil Hopkinson, director of technology at Xaar 3D and an original inventor behind SAF, said that the initial idea dates back to over 20 years ago, when he was researching the use of injection molding and 3D printing together.

“I’d conducted some analysis of the economics,” he said. “If you’re going to start making parts by 3D printing in some kind of volume, there must be a point at which it makes sense to start injection molding.”

To his surprise, Hopkinson found that with small, complicated geometries, 3D printing can hold the economic advantage in manufacturing thousands of parts—much higher than initially anticipated. These impressive results brought to light the exciting potential to utilize the speed of 3D printing in mass production. However, to truly compete at the production scale, 3D printing would have to demonstrate economic viability at the tens, or even hundreds, of thousands of parts.

“I wanted to look at ways to make it more compelling,” said Hopkinson. “The essence of it was trying to get the economics of injection molding while retaining the agility of 3D printing.”

This would come down to two primary objectives: reducing the machine depreciation cost of the 3D printer, and improving the quality of the printed parts—all while maintaining production speed. After over a decade of research and development, Stratasys and Xaar believe that they have found the answer with SAF.

Braving uncharted territory for 3D printing, SAF has been designed as a manufacturing process from the outset.

“We will enable a shift of many applications from traditional manufacturing and also enable creation of products that can only be manufactured additively,” said Omer Krieger, executive vice president of product strategy and corporate development at Stratasys.

As mentioned, SAF can be classified as a PBF process at heart in that it operates using the concept of selective fusion. What this means is that with PBF, rather than attempting to deposit powder in the exact shape of the build geometry, powder is deposited in layers covering the entire build surface. The geometry of the build is then determined by the regions at which this powder is fused together. PBF technologies are currently the most widespread in both metal and polymer manufacturing due to their high resolution and speed compared to competing technologies.

SAF technology aims to retain the best aspects of the PBF process while improving on its shortcomings. In SAF, the bulk of the process is carried out using two carriages. The first carriage contains a print head that releases infrared-absorbing fluid as well as a fusing lamp. As it travels over the powder bed, this carriage emits the fluid and exposes it to infrared (IR) radiation in tandem, fusing the powder at select locations to create the desired geometry. Following closely behind it is the second carriage, which distributes the next layer of powder using a counter-rotating roller while simultaneously preheating this powder.

This elegant approach is expected to eliminate much of the unpredictability of PBF. One of the biggest hurdles the technology has faced is the lack of repeatability that arises due to the complex thermal history that parts undergo as they are built. In other words, because the powder bed is being repeatedly heated and then allowed to cool at varying locations, it is hard to predict how the geometry will deform during the printing process. This complexity also gives rise to heterogeneous grains, which lead to anisotropy, where a part experiences different mechanical properties in different directions.

The two-carriage approach should, however, allow for unprecedented thermal homogeneity. The key building steps are all carried out in the same direction across the print bed, which means that the time between fusing a particle and depositing the next layer of powder on top of it is the same anywhere on the bed. This elegant solution will go a long way toward providing repeatable results that manufacturers can count on.

The SAF architecture will also allow the processing of materials that have traditionally challenged conventional PBF systems. Stratasys is remaining tight-lipped on the details for the time being, but Hopkinson has alluded to this being a direct result of the unprecedented thermal environment that SAF can sustain.

Another innovation featured in this technology is the Big Wave powder management system, which contributes further to the thermal homogeneity of the process as well as improves powder recycling. With conventional PBF machines, a newly deposited layer of powder will absorb heat from the previous layer as it is being deposited. The amount of heat absorbed into the new layer changes depending on location. More heat is absorbed toward the end of the deposition process as the body of fresh powder grows smaller. The Big Wave eliminates this thermal complexity by ensuring that there is a sufficient amount of powder being deposited at any location on the bed to minimize heat absorption. Not only is this touted to improve the thermal environment, but it is also expected to reduce powder aging and therefore enhance its recycling.

SAF has big goals when it comes to part quality and repeatability, but what about cost considerations?

“As I looked into the economic cost of making the part,” said Hopkinson, “it was clear that a big chunk of [the cost] was down to machine depreciation.”

SAF machines were therefore designed to have minimal consumables to help bring the process even closer toward conventional manufacturing tools. For example, the print heads selected for use in SAF machines are industrial-grade print heads designed for grueling conditions. Hopkinson is adamant that they are not intended to be replaced on a routine basis, and this is anticipated to take a sizeable chunk out of the operational costs. Additionally, this design is expected to improve reliability even further. Anyone with firsthand experience of additive manufacturing will know that changing consumable parts requires tedious recalibration, since the slightest change in parameters can have an enormous compounding effect. The importance of having a constant, unchanging configuration from which to work cannot be overstated. Much like with the Big Wave, reducing operational costs and improving process reliability go hand in hand here.

Stratasys’ new H Series Production Platform, featuring SAF technology, is slated for commercial release in the third quarter of 2021.