Thursday, January 5, 2012

No 3D Glasses Required

How do you build all of the blocks for an 83’ gaff schooner without access to the machinist, the fabricators, or the boatbuilders (who are respectively already too busy, too busy, and way too busy to take on additional work before launch)? It’s a pretty tall order but we may have found a solution in steriolithography files, overnight 3D printing, multi-axis milling and computer numerically controlled (CNC) routers.

While we haven’t completed any blocks yet, stay tuned — the test run looks promising. The ash shells are made right down the road at Tim Marchetti’s shop. Tim uses a CNC router to produce parts to our design. We sent him a few boards of Ash and a 3D computer model of the completed block assembly.

He took it from there to generate a tool path for the CNC router to follow.  It wasn’t more than a day or two later that Tim called to say that our parts were ready. The intricate shapes arrived complete with precision holes bored for the sheave axle pin, coin, and perimeter rivets. Each piece is a perfect duplicate and entirely interchangeable with the next. This should significantly reduce headaches and speed up the whole process come assembly time.

The bronze straps are going to be machined just a few miles from here, and while we never had any concerns that Richard Maxcy and his team could produce exactly what we needed, we did have some concerns about whether the parts from Knox Machine, Tim’s shells, and the sheaves being custom manufactured in Holland would all fit together once they arrived. We needed a way to test fit the metal parts and refine the design if necessary before committing to the significant expense of having all of those parts made. It turns out we’re not the first people to have this problem, and a pretty clever fellow named Charles Hull invented a solution in 1984.

The first 3D printers directed a very precise UV laser beam to a photo curable liquid polymer. These days it’s more common to use equipment that extrudes a hot thermoplastic or fuses individual granules of a special powder, either by means of precision applications of a glue binder, or again with a laser beam. Take your pick, the technology is pretty impressive. We used a company called Red Eye On Demand. It took longer to provide our name, address, and credit card details than it did to upload the 3D model of the metal part to the company’s server. Three days later the part arrived in a box.

Rockport Marine boatbuilder Tom Dayhoof took a box a parts down to the shop and assembled them into 3 blocks to see how long the process would take and test the accuracy of the fit. If necessary we’d have the opportunity to refine the design one last time before placing the order for the straps.  But they fit like they were designed to go together,  which of course they were.

-Brendan Riordan

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Location: Rockport, Maine, United States

Rockport Marine is a group of talented craftspeople who design, build and restore wooden yachts with unparalleled expertise.