Sandia National Laboratories team built a telescope demonstrating how to design for additive manufacturing in order to make the most of 3D printing’s strengths and weaknesses, according to Sandia Labs News.
Rather than focusing on printing precise parts, the team focused on how to assemble less precise 3D printed parts with more precise tools. This allowed researchers to take advantage of rapid prototyping and additive manufacturing.
“That’s the nuance that seems to get lost, that you have to design differently,” said Ted Winrow, mechanical engineer who led the project. “It doesn’t plug into a standard design process.”
The team was able to create a lightweight and less expensive ground-based telescope in one-third of the amount of time it would take to create a traditional telescope. The 3D telescope assembly consisted of 3D printed components, a modular design and image-correction algorithms.
As additive manufacturing forms the material, it is also creating the part, an ongoing, simultaneous process. Machining can make a part, but cannot often make unique 3D printed designs that offer advantages in function and weight. Ongoing research is determining whether changes in a material’s properties matter when using the part for a specific use.
The design process is separate from the creation process and raises other questions.
“Can we design a system that doesn’t care if your material is not as good as you expected it to be? Can you design a system that doesn’t care that your parts aren’t as dimensionally accurate?” Winrow said. “If you make yourself insensitive to the things that additive’s not very good at, you take advantage of all its good things.”
For example, normally a standard camera includes a ledge that helps define the position where the lens sits. Instead, Sandia’s researchers created a telescope with a straight cylinder and no ledges.
“We hold the lens at a very precise position using very precise tooling. We hold the lens in the right spot and then we inject epoxy around it and lock it into place,” Winrow said. “We can make parts that are less precise as far as dimensions are concerned because of the epoxy in the process. It’s the tooling that’s precise.”
Additionally, Sandia applied for a patent for a monolithic, titanium flexure that is included in the telescope mirror mount. The flexure represents an array of elements used, such as joints between rigid bodies. Rigidly mounting metal to glass is not possible because the two materials expand and change temperatures at different rates. The glass could potentially crack or distort, therefore, the flexure acts as a spring. In total, three flexure mounts attach to the mirrors with epoxy, which relieves the expansion and contraction stress.
Winwor said the lens is capable of creating an image but it contains errors, so the software algorithms correct these inaccuracies.
“The thought was you could have less precise optics and correct for it with software, essentially after the fact. Similar to how we designed the mechanical hardware to be insensitive to additive manufacturing shortfalls and take advantage of its benefits, Jeff optimized the optics of the system so the software maintained the image properties the algorithms could not have done as good a job correcting,” Winrow said. “You could get the same performance you could have if you spent three times as much money on better optics.”
Although the project has ended, the designers are still using information from the project.
“That was what the project was looking at, how these ways could make it faster and cheaper and just as good,” Winrow said. “If you talk about things you can give up, things you can compensate for after the fact, it opens up realms on the design side.”
Filed Under: 3D printing • additive manufacturing • stereolithography, Rapid prototyping