KTH – Part for underwater robot 3d printed in stainless steel

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Swedish Maritime of Robotics (KTH)


Problem description:

Our customer SMaRC – Swedish Maritime Robotics Center at KTH Royal Institute of Technology contacted us for help with 3d printing the nose cone for their underwater craft. In the nose of this robot are attachments for cameras and other very expensive measuring equipment, which made this part of the robot very geometrically complex and with high tolerance requirements. Earlier prototypes were milled, but as the complexity is too high to mill everything in one piece, SMaRC was forced to manufacture these in parts and then assemble them into a complete nose cone. The joints between all these parts led to unwanted complexity and leakage which made SMaRC choose to explore the possibilities of 3d printing the entire nose cone in one piece.

Picture 1: Complete craft with the nose cone at the front left.


Solution – 3d printing in stainless steel 316L:

The high pressure down on the seabed, the highly corrosive environment at sea, the tight tolerance requirements, the relatively large component and the overall weight balancing in the craft made this project very challenging and interesting for us to be a part of. The decision of process and material fell on stainless steel 316L (1.4404) printed with DMLS, vibration polishing, painting and milling. Thanks to 3d printing in metal, all imagined details could be manufactured as one and the same component, and the CNC machining that we performed on the surfaces and holes with super high requirements could be done in only two rounds in a 5-axis milling machine. This allowed the machining that was carried out to maintain very high dimensional accuracy over the entire detail in comparison to a nose cone that was milled forward as previously consisting of many individually milled parts.


The result:

As always with this type of high-tolerance parts, we made a measurement and saw that we missed the tolerance by a few hundredths in the groove for the large o-ring that seals against the rest of the craft. According to calculations and simulations, there was a risk that this would not be completely tight, and since we could not re-mill this part of the geometry in a good way, SMaRC had to keep the incorrect nose cone. SMaRC could then run the samples they could run while waiting for us to manufacture a new one for them completely to tolerances. After a few weeks, they received the correct nose cone and with it they were able to perform the long-awaited underwater tests with a fully sealed nose cone made in only one piece. SMaRC is very pleased with the collaboration and we want to thank SMaRC for your trust.

Image 2: SMaRC's logo.

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