A Georgia Tech startup has developed a 3D printing technology to transform the way costly metal parts, such as aircraft engine turbine blades and vanes, are designed and made.
DDM Systems Inc.’s new casting method makes possible faster prototype development times, and more efficient and cost-effective manufacturing procedures after a part moves to mass production.
Using additive manufacturing or “3D-printing” technology, DDM Systems can reduce the time it takes to make first castings of prototype turbine engine components from two years to three months or less. It eliminates 90 percent of material waste and reduces manufacturing cost by up to 65 percent, said Suman Das, professor of George W. Woodruff School of Mechanical Engineering who developed the technology and is DDM’s CEO.
The VentureLab company’s core technology is licensed from Georgia Tech and is based on $4.65 million in funding from the Defense Advanced Research Projects Agency (DARPA) awarded to Georgia Tech in 2008 through its Disruptive Manufacturing Technologies program. DDM also expects to raise $3 million from private investors.
DDM aims to alter a manufacturing process (investment casting) from the way it’s been done for the last 3,000 years, Das said.
Investment casting, a $11.6 billion industry worldwide, involves placing precision molded ceramic cores inside a wax replica of the final component. A ceramic coating is applied around the wax creating a shell. The wax is then melted out and the resulting mold is filled with liquid metal which solidifies to create the final component. The ceramic cores are removed to produce intricate objects with complex internal passages.
Investment casting is used to create precision parts in multiple industries, including aerospace, energy, biomedical, automotive, space, and electronics. DDM Systems’ current focus is on parts used in aircraft engines. DDM is working with turbine-engine airfoils – complex parts used in jet engines.
The most sophisticated parts made by investment casting are high-pressure turbine blades and vanes, said Das, who directs the Direct Digital Manufacturing Laboratory in the Georgia Tech Manufacturing Institute (GTMI). “That’s what we got funded by DARPA to develop the technology for,” he said.
How it works
Most precision metal castings are typically designed using computer-aided design software. But the next step – creating the ceramic mold with which the part is cast – involves a sequence of seven operations requiring expensive precision-machined dies and hundreds of tooling pieces. It’s a costly process that typically produces many defective molds and waste parts before a useable prototype is achieved. This trial-and-error development phase often requires many months to cast a part that is accurate enough to enter the testing and evaluation stage.
DDM’s approach involves buildin ceramic molds from computer-aided design software. Using a device called Large Area Maskless Photopolymerization (LAMP), the process involves digitally slicing the component’s design into hundreds of layers. Each “slice” is converted into a high-resolution black and white image in which the white portion corresponds to the cross-section of the part. The image is then projected, using ultra violet light, into a solution containing ceramic particles. When the light shines on the liquid, a chemical reaction is triggered that binds the ceramic particles in the same pattern that corresponds to the white parts of the image. The technique places one 100-micron layer on top of another until the structure is complete. The result is a fully ceramic structure into which molten metal – such as nickel-based superalloys or titanium-based alloys – are poured, producing a highly accurate casting.
The challenge was to produce highly accurate 3D-printed ceramic molds made of the same raw material as conventional ceramic molds to ensure durability of the final product, Das said.
DDM’s process not only creates testable prototypes but could also be used in the actual manufacturing process. That would allow more rapid production of complex metal parts, in both low and high volumes, at lower costs in a variety of industries, Das said.
DDM is in late stage trials with the Department of Defense. Das expects to have a commercial product by the end of the year and said the technology has drawn interest from “every major aircraft engine maker.”
A first generation LAMP machine is building six high pressure turbine-blade molds in six hours. Das’s lab at Georgia Tech is conducting final tests on a second generation LAMP machine that will produce more than 100 molds and cores at a time in about 24 hours.
See article in the Atlanta Business Chronicle by Urvaksh Karkaria.
Photo by Gary Meek.