n-Hedral – Behind the Scenes, Part 2: Waterjet Cutting

June 4, 2014 Engineering
If you haven’t checked out my Masters Project, n-Hedral: Customizable Furniture System, then do so here!

The main joint construction for the n-Hedral system was designed to use a single aluminum extrusion profile to serve three different functions:

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This profile, however, is completely custom and does not exist.  One way to prototype it, would be to purchase a radius endmill and use a vertical mill to shape lengths of aluminum barstock into the profile, and then cut them to size.  This, however, would require significantly more time than I had at that point in the semester.  So, I chose to go the rapid manufacturing route, and got the pieces cut using the Waterjet Cutter at NextFab Studio.

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This incredible machine uses a stream of water at pressures exceeding 50,000psi to cut through any material including metals and stone.  With 5-axis motion capabilities, this machine can do a lot more than the simple straight cuts I needed, but for my purposes, all that was needed to do the cutting was a simple vector drawing of the pieces I wanted cut:

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The design requires two thickness for the parts, 0.500″ thick for the trim pieces, and 0.625″ thick for the joint connectors.  The Flow Water Jet Mach 4c can cut anything up to is Z-clearance limit, which is 11.75″, as long as you’re willing to wait, so my parts were no problem at all.  In total, I made 100 trim pieces, and 120 connector pieces, for a total of 220 parts.  While not a high volume order by any means, it was definitely high enough to make manual machining out of the question.

  • The incredibly knowledgeable Alexander Numann operating the Flow Water Jet Mach 4c.

Once waterjetting was done, I had to go and cut the small tab out to free the part.  I used a pneumatic saw to remove all of the parts, then a file to smooth down the remaining tab.  Finally, I put each batch of parts into the tumbler to smooth the sharp edges, and even out the surface finish.  The interior face with the tab marks is hidden for all uses of the profile, so it was ok if there were some irregular surface marks.

  • Cutting out the connector pieces.

After tumbling, the pieces needed to be drilled out.  By design, there were only three hole configurations for the connectors, all of which could be drilled with a drill press.  To improve accuracy and reduce setup time, I made some quick jigs from 3/4″ MDF and got to drilling.

  • The trusty drill press.

After fabrication, I dropped the parts off at Multi-Flex Plating Company in Collingdale, PA.  For a very reasonable price, they turned around the 220 parts in about a week (over Easter weekend, too!).  The parts came back with a deep, beautiful red finish.

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The next step was to press in the PEM nuts.  This, I did back in the PhilaU metal shop, and it only took an hour or so to press in all of the fasteners I needed.

  • Zinc-plated steel PEM nuts with the red anodized aluminum bracket.

The final trim and clamp pieces looked beautiful.  Hard work, but it was well worth it.

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Click here to see the next installment of n-Hedral – Behind the Scenes!

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