One topic we’ve skirted around in our carbon fiber series so far is large-scale composite printing processes. The reason for this is because it is both a big topic, literally and figuratively and involves material mixes that don’t quite fit with the continuous carbon fiber reinforcements we’ve discussed so far.
Oak Ridge National Laboratory (ORNL) is a pioneer in this space because the U.S. Department of Energy Lab almost single-handedly developed the technology, though it did so with the help of public tax dollars and partnerships with companies in the industry. Working with machine manufacturer Cincinnati Incorporated and Local Motors, ORNL developed the first large-scale plastic pellet 3D printer.
The project team used an old experiment additive construction that consisted of a large gantry system meant for extruding concrete. The printer was retrofitted with a screw extruder to process pellets made up of ABS with roughly five percent chopped carbon fiber filler. Using pellets has the advantage of much faster material handling, as well as reduced cost, since these are the same materials made for injection molding. Since injection molding pellets are available in wide supply and don’t need to be further processed into filament, the price is significantly lower.
The result was the Big Area Additive Manufacturing-CI system. The original BAAM-CI system was capable of printing 40 pounds of material per hour in a build volume of 7 ft x 13 ft x 3 ft. To demonstrate the sheer power of the machine, ORNL and its partners have 3D printed the chassis for a number of vehicles, including cars, boats and excavator cabs.
Since the first BAAM-CI printer was used to create a replica Shelby Cobra, its capabilities have grown greatly. Cincinnati Inc. now offers four sizes ranging from 11.7 ft x 5.4 ft x 3 ft to 20 ft x 7.5 ft x 6 ft, with a feed rate that has doubled to 80 lbs/hr. Cincinnati Inc. now offers a wider portfolio of 3D printers, including a Medium Area Additive Manufacturing system with a 1m x 1m x 1m build volume and 1 kg/hr deposition rate, as well as desktop-sized Small Area Additive Manufacturing printers.
The ability to handle composites with higher carbon fiber content has been achieved, as well. When 3D printing the first vehicle chassis for Local Motors, a 15 percent carbon fiber fill was used. In some cases, up to 50 percent carbon fiber content has been printed. Cincinnati states that “dozens of materials” have been used on its BAAM machines, such as ABS, PPS, PC, PLA, and PEI. In addition to carbon fiber, glass fiber and organic fiber have been used for reinforcement.
Taking a cue from its competitor, CNC manufacturer Thermwood developed its own large-scale additive extrusion technology, the Large Scale Additive Manufacturing (LSAM) series. Available with either a fixed or moving print table, the dual-gantry LSAM series is available with a print volume of 10 ft x 20 ft x 10 ft or 10 ft x 40 ft x 10 ft and can deposit 500 pounds of material per hour. And, while projects made by the BAAM printer require post-processing via CNC milling, the LSAM series has built-in machining capabilities that bring near-net-shape blanks to their final form.
To beat out everyone else in the manufacturing equipment space, Ingersoll Machine Tools worked with ORNL to develop the MasterPrint 3D printer, capable of 3D printing objects as large as 100 feet long, 20 feet wide and 10 feet tall at rates of 150 lbs/h to 1000 lbs/h. The system also features a CNC tool for machining parts to completion. We should note here that Thermwood claims its LSAM platform can be extended to be 100 feet long, though we have not yet seen such a setup.
Ingersoll sold its first MasterPrint system to the University of Maine, which it used to 3D print a 25-foot, 5,000-pound boat in under 72 hours. The ship, which will be used in a simulation program, had the distinction of achieving a Guinness World Record for the world’s largest solid 3D-printed item and largest 3D-printed boat.
The goal of the printer for Ingersoll is to fabricate massive tools for the aerospace industry. Upon the unveiling of the massive ship, CEO Chip Storie said, “The reality is we went into this technology targeting aerospace and you can print a large aerospace tool in a matter of hours or days where if you go the traditional route, it can take nine or 10 months to be able to build a tool. The cost difference for traditional tooling can run upwards of a million dollars to build an aerospace tool, where you can print a tool using our technology for tens of thousands of dollars. So, there’s a huge cost benefit. There’s a huge time benefit for the aerospace industry.”
The composites being used by these companies may only feature chopped reinforcement materials, but the speed and scale at which they can print is certainly impressive. In the case of Ingersoll, the company is working on incorporating hybrid modules that include fiber placement, tape laying, inspection and trimming.
We may see such systems as these become commonplace in certain manufacturing environments, particularly if continuous reinforcement can be integrated into the process. To learn more about the future of carbon fiber 3D printing, we’ll be looking at research endeavors in this field in our next section in the series.
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