Grand Rapids, Michigan-based Burton Precision is a machine tool distributor specializing in the application of metrology and 3D Printing products. Their involvement in manufacturing crisscrosses the breadth of industries with technologies that have a direct impact on successful product design and manufacture.

A unique opportunity involved the University of Michigan’s Human Submarine Team, which contacted Burton Precision to enlist its assistance in dealing with some CAD issues related to producing a propeller for a submarine that is designed and built by students.

Said Rick Kerkstra, Burton Precision vice president and 3D printing specialist, “We held an open house at Burton Precision for GR Makers in Grand Rapids, which is an open community lab that incorporates elements of a machine shop, a workshop and a design studio. Members there work on projects that range from the industrial to the delicate arts. It’s a unique community that focuses on enabling personal expression, providing education and supporting entrepreneurship. We were demonstrating our metrology and 3D printing products for them. I met an individual there who mentioned that his brother belonged to the Human Powered Submarine Team at the University of Michigan and they were having problems with a point cloud file for a propeller design. More specifically, they couldn’t convert the file to a ‘friendly’ file that they could put to a cutter path on a CNC machine to make the part.”

Jeremy Werner is with the University of Michigan’s Naval Architecture and Marine Engineering Department and the President of the Human Powered Submarine Team. He outlined the CAD issues they were having with a propeller design program called Open Prop, which wasn’t allowing them to export files in a format that they could use to create a toolpath. He provided Kerkstra’s team with the point cloud files, which did not include outward normal vectors. The units were in meters and arranged with 100 rows of points along the length of the prop blade, and 40 points per row (20 on either side of the blade). Ultimately, they wanted to make the toolpath in GibbsCAM®.

“I think Jeremy and I had about fourteen emails the first week so it wasn’t as simple as a file conversion,” said Kerkstra. “It usually never is. He sent me an STL file that I read into Geomagic® Studio Software in an attempt to create a nurbs surface.

“We were dealing with low resolution files and an edge on the blade that was giving the surface creation fits. Jeremy did four or five re-writes before we had a file that we could use. Once we had a good surface file to give back to him, I asked if we could 3D print it for him…and that opened another door. We had further discussions about strength of material, testing using a scale version and overall functionality of the 3D printed part. The first surface files that we provided failed the initial testing in their simulator because the blade thickness was too thin. That was enlarged and the thicker blade passed. We 3D printed the propeller on a 3D Systems ProJet 3500 HDMax printer in a plastic material called Crystal. The blade assembly was 10-inches long.

“For projects like what we provided for this propeller design, one to two days is necessary to complete the data conversion, if we have clean printable files. Because 3D Printing technology is new to most of our customers, we still have to do some educating as to what it takes to develop a 3D printable file…that ultimately takes only a few hours to print the part.”

Said Werner, “This kind of out-of-the-classroom training is at the core of our team’s mission statement, and everyone from outside U of M who contributes to that deserves special recognition.”

The full-scale, self-propelled test of the submarine and its systems were tested on April 22, 2014. “The test was successful…the propeller worked perfectly,” said Kerkstra, “…and we’re hoping to sell a 3D Printing machine to the University.”

Burton Precision
www.burtonprecision.com