Due to concerns about infection in hospitals, AREVO also is printing single-use composite surgical guides to replace the metal guides that are autoclaved and reused. 3-D printing allows the single-use composite parts to be optimized for each patient.
Faster Printing Technologies
The team at Impossible Objects has been developing its new 3-D printing technology for six years. “Our goal has been to improve the typical 3-D or additive manufacturing processes in areas like speed, material properties and material selection,” says Bob Swartz, chairman, founder & CTO. “Composite materials, it turns out, have properties that made them extremely appropriate and applicable to what we were doing.
“When you start thinking about additive manufacturing, you realize very quickly that it’s a material science problem, and when you think about material science problems clearly composite have immense advantages over the typical polymers alone. So you ask if you can exploit that in some way, and the answer seems to be yes,” he says.
Impossible Objects will use PEEK polymer carbon fiber in additive manufacturing to produce high-performance parts with better strength-to-weight ratios than metals and with resistance to chemicals and temperatures up to nearly 300 C. But working with the high temperatures involved in PEEK printing meant the company couldn’t use its typical ovens and other equipment. In addition, PEEK powders exhibit a different behavior and rheology than others, which affects the printing process.
Impossible Objects employs what is fundamentally a graphic arts process in its composite-based additive manufacturing process (CBAM). It uses conventional thermal inkjet heads to print designs on sheets of reinforcement, like carbon fiber, Kevlar® or fiberglass. Each sheet is then flooded with a polymer powder causing the powder to stick where inkjet fluid has been deposited. Excess powder is vacuumed off, and the sheets are stacked, compressed and heated. The polymer powder melts and bonds the sheets together. The uncoated fibers are then mechanically or chemically removed, leaving a durable, lightweight object.
Although the company is not printing in large volumes today, it has produced small runs of objects like propellers for large drones. But that’s just for now. Swartz observes that high-speed inkjet printers can produce 15,000 to 18,000 sheets an hour, and he hopes to reach similar speeds using CFRP. “That will actually allow you to be substantially faster than it would be to injection mold,” he says.
Slashing Tool Production Time
The Department of Energy’s National Rotor Testbed project employs additive manufacturing of tools to produce wind turbine blades. Project partners include Oak Ridge National Laboratory (ORNL), Sandia National Laboratory, TPI Composites and Wetzel Engineering.