Monday, February 20, 2012

Hexagonal Table Made on the 5-Axis CNC Router

Here is a hexagonal table I designed and built as a test of 5-axis CNC wood joinery. It was cut in the Digital Fabrication Lab at the Taubman College of Architecture at the University of Michigan.

My idea for this project was to use a joinery technique that is difficult to make using conventional woodworking tools (table saw, sliding compound miter saw, etc). I choose to use all compound angles (non-right angles cut in two directions at once) with loose mortise and tenon joints. I'm using the 6mm x 40mm "biscuits" normally for use with the Festool Domino. The top is joined to the legs with dowels. There is a spline joint used between each side of the legs.

Here's the design (see-through so you can see the joinery):

Here are a few parts showing the joinery - on the top is a side, on the bottom is half a leg:

The wood I'm using is quarter-sawn white oak. It's stable when cut - and the figure evokes mission furniture which is a precursor to the look I'm after.

The top of the table sits in a rabbet in the sides. It is not secured to accommodate wood movement.

Here's the top, dry-fit. You can see the rabbet and storage available beneath the top. 

Here are some photos of the C.R. Onsrud router. This machine has a 12 h.p. motor.

In order to cut these pieces on the router, fixtures were required. These are simple CNC cut Medium Density Fiberboard (MDF) pieces, with grooves cut to allow the vacuum pressure form the table to be distributed under the workpiece thus holding it in place. The grove at the edge of each fixture holds a rubber gasket (removed in this image). It prevents the vacuum pressure from escaping the fixture.

The smallest piece - the stretcher parts between the legs - required some pins to hold the work from rotating. On work that small the vacuum pressure is not sufficient. For all other parts the vacuum from the table below was fine. 

Here are some parts, loosely dry-fit, before glue-up. You can see the knife edge on the leg parts. The spline joint was a huge help during the glue-up of these parts: 

Here's a video of the router in action cutting one of the six sides. You can see the vacuum table, the pods which lift the fixture and workpiece up to a sufficient height and transfer the suction to hold the board securely.

1 comment:

  1. Great stuff!

    I hate to think what the machine run time was on that puppy ;)