Additive Manufacturing continues to evolve rapidly in various industries, it has been widely regarded as manufacturing industries evolution as far as customization, speed and sustainability is concerned. Additive manufacturing also allows digital transformation of the traditional manufacturing and helps its transition to Industry 4.0.
Impossible Objects LLC, a Chicago-based company, has developed a new manufacturing technology for composites, called Composite-Based Additive Manufacturing (CBAM). This technology can produce Carbon Fiber Reinforced Plastic (CFRP) or Polymer Matrix Composite (PMC) parts.
High degree of build flexibility is one of the primary advantage the CBAM technology offers. The process can be used with carbon fiber, fiberglass and Kevlar composite sheet material and a number of high performance thermoplastic matrix materials including HDPE, nylon 6, nylon 12 and PEEK materials.
The CBAM process starts with a digital model, electronically slices the file into layers, and uses the bitmap layer data to print the image onto the composite sheets. Non-woven composite sheets are used as the build material. The sheets contain long fiber lengths and have a random fiber orientation throughout the sheet.
The composite sheets are conveyed to a print bed and uses the digital model slice layer data to deposit a water-like wetting fluid by utilizing inkjet printing type approach onto the sheet surface to create the layer image. The sheet with the wetted image continues moving to a powdering station where an overhead trough floods the composite sheet unselectively with a uniform thickness of thermoplastic plastic powder.
Next, the powdered sheet is conveyed to a depowdering station where the thermoplastic sticks to the wetted sheet region. Loose thermoplastic material on the sheet is blown off and recycled for future builds. A high level of recycling and material reuse is possible since the thermoplastic materials are deposited and removed at room temperature, causing no changes to the chemistry of the thermoplastic material.
Compressing the layers
Printed sheets are automatically aligned and stacked onto a tooling plate until all sheets that make up the digital model are printed. The process uses a heated press that heats the tool and the printed sheets to the thermoplastic materials melting point while compressing the part to the desired height.
The compression of the layers combined with the heat causes the thermoplastic to flow in between the long fibers of the unwoven sheet to form a composite part. This processing technology simplifies the post operation of the printed part.
In the final step the part is removed by bead blasting the build block to access the composite part. The blasting shears the fibers where there is no thermoplastic material, allowing for the non-woven fibers to be reused again making it a highly sustainable process.
Advantages of CBAM
Apart from material processing flexibility and sustainability that have been covered already, the CBAM process also offers specific mechanical and strength advantages.
CBAM parts tend to have similar weight to strength ratio as that of a aluminum alloy however are 50% lighter compared to aluminum parts.
Compared to traditional polymeric additive processes CBAM parts tend to have 2x to 10x tensile modulus as CBAM parts can utilize long fibers from the non-woven fiber sheets where traditional polymeric additive processes are limited to using short fiber lengths.
CBAM parts tend to produce good surface finish (can be finished to surface finish Ra of 20 micro inches), sharper details, geometrical tolerances, capability to produce thin walls, and did not have part warping compared to other conventional additive manufacturing processes. This is driven by the heated compression process step in the CBAM technology.
Some of the first industry CBAM part adopters are from the unmanned systems, robotics, and the electronics industries. The material properties along with similar strength to weight ratio and 50% lighter weight structures compared to aluminum allow for greater payloads and extended operating times—key product performance benefits for an unmanned system.
Aurora Flight Sciences, a leader in the development and manufacture of advanced unmanned systems, utilized the Selective Laser Sintering (SLS) 3D printing process to manufacture nylon mounting clips that attach the rear horizontal stabilator to body of the vehicle.
These SLS mounting clips would frequently break when the vehicle would make a hard landing. It was due to the lack of SLS material strength properties and stiffness. To resolve this matter, the SLS parts were replaced with CBAM made with a carbon fiber with nylon 12 matrix material.
Another emerging CBAM application family is for electronic enclosure cases. Customers are finding improved electromagnetic interference protection as well as lighter weight assemblies for enclosure cases made with the CBAM process.
Some of the emerging applications that utilize the design and build freedom of the composite-based additive manufacturing technology are to make integrated, monolithic structures like drone airfoils. They illustrate how internal structure such as core and stiffeners can be integrated into a single piece. This allows the designer to vary feature detail and part wall thicknesses to optimize structure for strength, weight, and ultimate performance.
What will be interesting to witness in the future is the use of different material build combinations enabled by the CBAM technology. The use of unidirectional carbon fiber materials will significantly increase part strength and stiffness by 3× to 6×, increase a larger number of thermoplastic matrix material options, and increase the potential to utilize other matrix materials. The ability to use materials like thermoset epoxies and powdered metal alloys to produce either thermoset parts or Metal Matrix Composite (MMC) parts will open exciting new opportunities.
Besides expanding the range of material build combinations, CBAM technology will continue to scale up to make larger part sizes and utilize robust printing technologies to achieve build speeds similar to traditional manufacturing methods. The result will be to further advance the technology to exciting new composite applications in other industries.
The author, KetanDeshpande, lives in Minnesota and writes about a variety of topics in his blog such as global economy, market and industry trends, successful strategies for businesses, and others. Leveraging his global strategic leadership experience from the manufacturing industry to offer insights in to how businesses can meet the sustainable growth and profitability goals.
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