RALEIGH — The classroom is humming with the sounds of computers and the murmur of students clustered around screens.
“Move it over there,” one student tells another whose hand is moving the cursor around on the screen. There are plenty of geometric shapes being manipulated as the students use an engineering program to design a part for a piece of machinery.
“That’s pretty cool,” Dr. Tim Horn tells the group.
“The original piece was 1.6 kilograms and you’ve cut it to 0.6 kg. So you’ve cut a lot of weight. Good job,” Horn adds. Horn is an assistant professor at the Center for Additive Manufacturing and Logistics at North Carolina State University. The Center is hosting a camp for prospective engineering students from high schools across North Carolina.
The camp’s focus is additive manufacturing, which is better known as 3-D printing.
“It’s a totally different way of manufacturing,” says Horn. “This allows us to make designs, to do designs and to realize designs that couldn’t be manufactured any other way.”
You might know 3-D printing from the little animal figures, building models and other decorations that are made from a variety of materials. They all exhibit incredible detail.
And it’s because 3-D printing allows for creating objects with intricate geometric patterns, complex features and precise detailing that the process is revolutionizing manufacturing. Objects that were physically or even financially impossible to make not long ago can now be created.
“There are certain areas of manufacturing such as medical devices, custom medical implants and even parts for machines where we want low batch sizes of highly specialized, complex components,” explains Horn. “Those are high value added parts where only a few are needed and this is where additive manufacturing shines."
A good example of what 3-D printing can be used for is the project the students are working on. They were challenged to reimagine a brace for an airplane engine. Currently, the pieces are made in a traditional iron forge; a die was slammed onto a piece of hot metal. The end product is solid and heavy, weighing about 4.5 lbs.
The redesigned piece, made through additive manufacturing, weighs about 0.75 lbs. It is still made of iron, but the inside resembles a honeycomb.
The pieces are equal in strength, but engineers on a computer created the redesigned piece. Software was used to test it; material was added to areas with the greatest stress and excess material was removed where it wasn’t needed. The design was optimized before it was retested and built.
“The shape of the brace made through traditional manufacturing is constrained by the process in which it was made,” says Horn. “With additive manufacturing, because we don’t have a tool and die, we are free to put geometries wherever they fit, and we are free to remove material where it isn’t needed.”
In other words, the designer can add material to places where the stress on the piece is greatest and remove excess material that isn’t needed.
There are different types of 3-D printing and each employs a different technology that processes materials in different ways.
Stereolithography fires a laser into a vat of polymer resin, tracing one layer of the object to be printed. The resin hardens at the point where the laser hits the surface. Once the object is traced, the platform within the vat drops by a fraction and the next layer is traced. The process continues until the entire object is created.
Another version of additive manufacturing is laser melting, in which a beam is fired across a bed of material. The laser fuses the material. Once a layer is traced, the platform drops and work on the next layer begins.
There are new technologies and new applications continually being introduced in this rapidly changing field. But the common factor is that each item is manufactured one layer at a time, which allows for precision manufacturing. The challenge is to apply the proper material and design to the project at hand.
“We are working to develop new materials, new alloys, new systems and the process parameters to manufacture with those materials," adds Horn, who shows off almost a dozen types of 3-D printers at the Center, which is located in the middle the NC State campus. The machines vary in size and shape.
“Right now, we are testing manufacturing with nickel super alloys to see how they stand up to high temperatures and high-stress loads in the aerospace industry,” says Horn. “We’ve had years of experience working with these materials in casting and forging but now we have to see how they can be made using additive manufacturing.”
And the questions are basic to the manufacturing process. Do the materials process the same? Are the crystal properties the same? Is the strength and durability the same? Engineers know a lot about the materials but in this new design and manufacturing world, there is also a lot they don’t know.
What is known is that the technology is being utilized in designing and manufacturing a broader range of products. At Designbox in Raleigh’s warehouse district, not far from high tech center on NC State’s campus, LYF is a startup company making custom footwear. Same process—each piece made one layer at a time—but just like that brace for an airplane, it is customized to fit a need.