Quite a few small 3D printers look like microwaves. The 3D printer industry has handled the demand for larger parts by making what look like even bigger microwaves. The Stratasys Fortus 900mc is the size of a walk-in closet. But Stratasys recently revealed some thinking way outside the box…or the closet. Two such ways were shown in a press event held at the company’s headquarters near Minneapolis.
A Stratasys depiction of a manufacturing future - 3D print head on a robotic arm. A version of this was shown at the Stratasys press event to make carbon fiber reinforced parts. (picture by Stratasys)
Called “demonstrators,” Stratasys’ two new 3D printing systems appeared not quite ready for prime time.The systems are not neat products, but are instead hardware with exposed parts, wires and hoses in plain sight. They looked very much like works in progress—quite possibly the result of feverish engineering activity before the big International Manufacturing Technology Show (IMTS
) show in Chicago next month. Nevertheless, even in their current state, the systems are harbingers of breakthrough 3D printing technology concepts, providing some concerns (coming up) that will need to be addressed.
Stratasys CEO Ilan Levin, les that 2 months on the job, hosts a press event to announce a size breakthrough in 3D part printing.
Breaking out of the box from current 3D printers was done in two ways. One way was with a large carbon fiber printer that looks unlike most printers because it is essentially a 3D printer head mounted on a robotic arm. The second way was with what Stratasys claims to be an “infinite build” 3D printer, which would seem to suggest it can have parts of any size. But before you get too excited, infinity is only offered along one direction. The height and width of the printer are limited to 30 inches in height and 40 inches in width. An “infinitely long part 3D printer” would be more accurate, but “infinite build” does sound better.
While these systems are not fully productized—no pricing has been set for them—both concepts show the company's serious intention to address one of the main impediments of current 3D printing in industry: 3D printed parts are just too darn small. Industrial 3D printers have addressed this in the past by enclosing bigger and bigger volumes—even larger than walk-in closet sizes—as well has making bigger parts within parts and joining them together.
Stratasys composite printing head on a robotic arm has the potential of making large parts. 3D print head is being fed a filament that included chopped carbon fibers.
Composite Parts with a Robotic Arm
One way to escape the confines of the printer box is to attach a 3D printer head to a robotic arm, making it now free to move about and be limited only by the size of the robotic arm. While using a robotic arm in this way is not a new concept (see MX3D, Branch Technology, 3D Systems, LittleArm and Arevo Labs), everything introduced previously will look puny next to Stratasys’ KUKA robotic arm—a monster that looked like it could grab you from 15 feet away.
Arms but No Eyes
Signs warn of potential injury. We are reminded of grisly factory accidents from arms that have no eyes and microprocessors that have no feelings. A sudden lunge by the arm to make another feature made a few members of the assembled media jump back. The plexiglass safety barrier would have slowed down the KUKA only a little.
But the fact that the robotic arm can’t see or be aware of its exact place in space points to what could be its biggest problem. Responding only to G-code, what’s to tell the arm where it really is? There is no feedback from its surroundings and there are no corrections. Given the length of the arm and the movement in its joints, what is to ensure its precise deposit of print material and the accuracy of the part being made? Whereas the rigidity of X-Y positioning of the print head in a conventional 3D printer lends itself to greater accuracy, the position at the end of a long robotic arm seems more prone to error.
In aerospace, an industry where every ounce shaved off a part by an engineer is calculated as profit by an accountant, carbon fiber has emerged as the dream material.
Enter the Stratasys Robotic Composite 3D Demonstrator, with a print head that receives a filament of material in which chopped carbon fibers are embedded.
Chopped carbon fiber is the current Stratasys solution to the need for stronger aircraft parts. Chopped fiber parts are only about 2X as strong as a part that lacks that reinforcement.Real strength gains come from continuous carbon fiber, but that involves winding the fiber around a part or implementing a more advanced carbon fiber layup process. These processes are currently in use for aerospace parts as large as commercial aircraft wings and fuselages, and involve setups even larger that Stratasys’ KUKA robotic arm.
Stratasys also understands the need of continuous carbon fiber, which makes parts that are at many times stronger, but the company’s representatives did not commit to a time when a continuous carbon fiber solution would be available.
Chopped carbon fibers also contribute to the clogging of print heads, but according to Stratasys, its proprietary design alleviates this problem.
Stratasys’ other announcement was about its “Infinite-Build 3D Demonstrator,” which seems to be able to make parts that are up to 30 inches tall and 40 inches wide, but without any limit to length, save the distance to a wall or running out of material.
Stratasys manufacturing cell for its "Infinite-Build" is a 30" x 40" 3D printing assembly laid on its edge. The robotic arm fills the hoppers (shown empty here) with 3D printing “micro particles.” (Image courtesy of Stratasys.)
Think of a conventional X-Y gantry in a standard 3D printer, but which is now stood up on its side. As each layer is deposited, the table underneath moves the part horizontally away from the print assembly for the next layer. Allowing the part to be made layer to layer, now horizontally, limits the part length to the next wall, rather that the ceiling—or the top of a build volume.
Why did no one think of this before? It beats having to build long parts in pieces and bond them together.
The Infinite-Build 3D Demonstrator also uses a KUKA robotic arm, but only to fill material bins. This allows unattended operation.
Weak in the Zs
Long thin parts, now bigger, seem to be exactly what the Infinite-Build is suited for.
“We can now make wings for a commercial jet,” joked one Stratasys executive.
That would not be a plane you would want to fly on. Long and thin only work for a few of our favorite things. Fashion models. Cables and ropes—and those only in tension. We get away with using wood for long thin parts, like shelves, because wood is cut along the length of its fibers. Conversely, 3D printers have been historically weak in the Z dimension, since that is the dimension across the layers of deposited material. A long part without reinforcement in the Z direction would be prone to failure in bending, tension and twist.
When asked about this, Stratasys seemed aware of the problem, and recognized the need for reinforcement of parts in the Z direction.
“We will have to orient strengthening along the Z dimension,” they said.
Other companies are addressing this weakness along the Z-axis in various ways. Rize 3D, for instance, has developed a new material that is able to maintain a stronger bond between layers, losing only about 10 percent of strength on the Z-axis. Cosine Additive and Essentium Materials have introduced a thermal welding head to their printers to ensure proper bonding between layers.
It’s not unreasonable to think that Stratasys’ new technologies could leverage the freedom of motion granted by the KUKA robotic arms to 3D print from every angle and decrease the weakness typically found on the Z-axis. Whether or not the Infinite-Build 3D and Robotic Composite 3D Demonstrators will be able to pull this off is something we’ll have to learn when Stratasys ships them off to Chicago for IMTS.
How well the Infinite-Build 3D and Robotic Composite 3D Demonstrators will fit into the larger manufacturing landscape is something time – and testing -will tell. But for now, it is clear that 3D parts can now get a lot bigger, thanks to out-of-the-box thinking by Stratasys.