After the merger with Objet in 2012, Stratasys became a manufacturer of PolyJet 3D printing systems, but the company was already well known for its fused model deposition (FDM) process, with which thermoplastics are extruded within a temperature-controlled box. At the IMTS show this year, however, Stratasys unveiled two new technology demonstrators that represented some out-of-the-box 3D printing processes, both figuratively and literally.
The Infinite-Build 3D Demonstrator removes the sixth side of the typical FDM box and allows massive prints to be manufactured with hypothetically infinite lengths. The Robotic Composite 3D Demonstrator uses a six-axis, industrial robotic arm to extrude composite materials onto a two-axis rotary table in open air, allowing for an automated method for manufacturing composites.
As unusual and unique 3D printing platforms, both 3D demonstrators are a bit difficult to wrap one’s head around for anyone who didn’t make it to IMTS. For this reason, ENGINEERING.com spoke to Scott Sevcik, director of manufacturing platform development at Stratasys, who was able to break the demonstrators down into easy-to-understand pieces.
The Infinite-Build 3D Demonstrator
The Infinite-Build 3D Demonstrator was the result of Stratasys' roughly 10 years of partnership with aerospace giant Boeing. During that time span, Sevcik influenced some of the requirements for future FDM technologies. Building off of Stratasys' largest FDM system, the Fortus 900mc, the company began work on the Infinite-Build over the past several years, with the specific goal of constructing large parts, such as aircraft interior panels and tooling to aid in the manufacturing process.
What's fairly clear to anyone who’s read about the Infinite-Build platform is that it takes Stratasys' traditional top-down 3D printing approach and, as Sevcik put it, “turned it on its side.” The build platform is rotated from a horizontal table to become a vertical wall. An extruder then 3D prints onto that wall layer by layer, as the bottom layer extends out into open air indefinitely. Though FDM is turned on its side, Stratasys still refers to the X, Y and Z dimensions of the build in the conventional way, referring to the extended axis as the Zaxis.What may be less clear are the specifics of how this technology works. An important element to ensuring a stable printing process is the heated chamber within which the printing takes place. Sevcik described it as an oven, saying, “We have a very highly controlled temperature profile within the oven, the region where the part is being built. As the part grows—as we add additional layers to the part—it extends out of that controlled thermal gradient and is brought out to room temperature. Because we’re building out of that sixth side of the box, we’re able to continue building indefinitely.”
One question that may occur is how the print bed is able to continue its expansion. Sevcik explained that the initial layers are printed onto a flat metal plate with a plastic covering to which the printing material adheres. Once a number of layers have been printed and the platform exits the oven, the metal plate is removed and the part simply continues to be built.
Uniquely, in order to support the print as it extends, the system prints a series of ribs along the bottom surface of the part, which are grabbed and pushed over. “You can think of it as pinching onto this rib and then pulling it further in Z and releasing,” Sevcik said. “We print, we grab those keels again and we move it over, so it's a continuous motion system that we’re actually printing in order to interface with the part as we go.”
To ensure that enormous prints don’t take an enormous amount of time, Stratasys also sped up the rate of deposition with a new miniature screw extruder capable of printing about 10 times as fast as traditional extruders. Unlike the company’s previous extruders, the Infinite-Build extruder relies on plastic pellets instead of filament, refilling its material supply continuously throughout the build. However, the system is flexible so that the extruder can be automatically swapped out for a different toolhead during the process.
“The extruder can go over to a tool changer and take a different extruder of the same material if it's detecting a potential failure condition and needs to maintain reliability, or it can be a different extruder carrying a different material,” Sevcik explained. “With this architecture, we're able to do multiple colors or a number of similar materials within each and every layer.”According to Sevcik, the new extruder also gives the system a high degree of control over the material output, allowing what Sevcik said is a closed-loop printing process. The Infinite-Build process can control the amount of material that is being extruded, allowing for less material when going around a corner or more material when printing long, straight lines. Additionally, the screw makes it possible to measure such variables as the pressure within the system in order to make changes automatically during the printing process.
Throughout the fabrication of a part, the Infinite-Build has a helpful friend in the form of an industrial robotic arm, which can add new material canisters, remove empty material canisters and stock the local tool exchanger. This robot demonstrates how the printer can be integrated into a manufacturing setting, with existing technologies capable of aiding in the printing process.
The Robotic Composite 3D Demonstrator
While the Infinite-Build was designed to 3D print very long thermoplastic parts, the Robotic Composite 3D Demonstrator is meant to make parts even lighter and stronger, and in a more automated way, than previously possible. Sevcik explained that the technology was developed in less than a year, due to Siemens’ existing commercial and near-commercial software and Stratasys' own technology.
Most 3D printing technologies create parts that are substantially weaker in the Zaxis than in the X and Y. This characteristic, known as anisotropy, is exaggerated in 3D-printed composite parts, according to Sevcik, due to the fact that parts are only strong in the direction in which they are reinforced. Think of a piece of wood. It is easier to split the wood if you chop between the grains. FDM parts are the same.To solve this problem, Stratasys teamed with Siemens, already known for its motion control technology, to create a 3D printing system that can print in just about any direction necessary. The Robotic Composite 3D Demonstrator features a plastic extruder fixed to a six-axis robotic arm that prints onto a two-axis rotary positioning table. With this setup, it's possible to both reorient the part and the print head throughout the process so that the reinforcement fiber can be laid down along the proper axis for the greatest strength.
Incidentally, the ability to 3D print a part from any direction also does away with the need for support material, according to Sevcik, cutting the print time and travel time of the print head, as well as the material waste and post-processing associated with support structures.
As Sevcik explained, “What that does from a workflow standpoint is quite dramatic after the fact—you no longer have to spend time in the workflow removing the support before it moves on within the manufacturing process—but also you’re not continuously changing between a model material and a support material during the build.”“You're printing the model the entire time, which has allowed us to go significantly faster even with the traditional extrusion approach,” Sevcik added. “We're able to print parts that would have taken on the order of 14 or 15 hours and do them in about an hour and a half because of that design freedom.”
Though the platform was shown using a traditional filament extruder, the Robotic Composite system can also use the same miniature screw extruder featured on the Infinite-Build printer, further speeding up the process. Similarly, the robotic arm can swap out tool heads to bring in a subtractive head or an inspection head, depending on what’s needed during fabrication.
Existing methods for composite manufacturing are typically expensive and time and laborintensive. With Siemens, Stratasys is able to create a highly automated process for fabricating reinforced composite parts, thus bringing down the cost and opening the technology up to a wider number of customers and applications.
At the same time, composite parts can be further optimized through the benefits brought about by 3D printing. 3D printing is capable of producing geometrically complex parts that can increase the efficiency of the part and reduce the overall weight. Because composites are often used to create stronger, lighter weight parts, 3D printing can drop the weight even further through topology optimization.
One concern for those in aerospace or other high-performance industries is the percentage of reinforcement achievable with this 3D printing process. For instance, the Big Area Additive Manufacturing technology from Cincinnati Incorporated has, so far, only been shown to use a ratio of 20 percent carbon fiber to ABS plastic.
Sevcik would not give any specific numbers as to how high Stratasys could load the thermoplastic with reinforcement material, instead saying that it depends both on the resins and the filler that's being used.
“We use a variety of different materials ranging from metallic fills to carbon fiber fills to glass beads,” Sevcik continued. “The properties of the resin also determine how much you can fill and still be able to use the extrusion process. We can actually go to very, very highly filled levels with the right filler and the right thermoplastic. In many cases, those are material combinations that are already proven and accepted in the aerospace industry.”
Out-of-the-Box Manufacturing
In an announcement related to its full suite of product lifecycle management solutions for additive manufacturing, Siemens hinted at a platform that sounds strikingly similar to the Robotic Composite printer, writing, “For extruded materials such as plastics and carbon fiber–reinforced nylon, a new multiaxis, robotic FDM programming technology has been developed and is being field tested. After parts are printed, the same integrated NX system is used for post-printing NC operations such as intuitively programming the removal of support structures, machining of precision surfaces and other processing and inspection operations.”
Sevcik pointed out that he believes such industrial motion technology, like robotic arms, have unique benefits when coupled with 3D printing technology. As he explained, “Integration with industrial motion systems brings the ability to streamline the workflow, whether that is support removal or addressing workpiece holding issues, not having to reposition the part and tool for the part in each step along the process. It makes it possible to focus on the part itself.”
Stratasys has yet to provide a specific release date or price for the new technologies, but the company is looking into the right partners and applications for the Infinite-Build and Robotic Composite 3D Demonstrators.
As Sevcik elaborated, “At this stage, we’re closely engaging with customers that are expressing interest both on the Robotic Composite and Infinite-Build systems. As we've announced, both Ford and Boeing are actively involved, developing applications with [the Infinite-Build] system today. We are now exploring possibilities on the right partners and right applications for both the Infinite-Build and Robotic Composite 3D Demonstrators.”
The exact details of the release of these two highly unique systems may not yet be available. What is clear, however, is that they won't just bring 3D printing out of the box, they'll take manufacturing along with it.