1: DESIGN YOUR CHAIR

I wanted to create a sculptural stool chair design. I used Solidworks to loft together a column consisting of a hexagon, a square, a triangle and a circle:

• Sketch a hexagon ~300mm diameter on the top plane
• Create a new plane parallel to the top plane and 150mm above it
• Sketch a square ~150mm in width on this new plane
• Create a new plane parallel to the new plane and 150mm above it
• Sketch a triangle ~400mm in width on this new plane
• Create a new plane parallel to this new plane and 150mm above it
• Sketch a circle ~500mm in diameter on this new plane
• Create a new plane parallel to this new plane and 75mm below it
• Create a solid loft out of the hexagon, square, triangle and circle.

To make the concave seated area:

• Draw a sketch on the front plane of the curved section to be removed from the top of the lofted column
• Turn this sketch into a revolved surface
• Cut the lofted column with the surface cut feature

Extrude a hole through the centre of the column to add a rod through all the layers to give the column extra strength and allow the layers to be moved and create different shaped columns when the chair is assembled

Save an .stl

2: TRANSFORM YOUR SOLID STL FILE INTO MANY LAYERS

Autodesk's 123D Make has a very useful feature that transforms solid stl models into layered models and exports these layers onto a sheet size of your choice:

• Download Autodesk's 123D Make for free
• Import your .stl file
• Chose the Stacked Slices in the Construction Techniques menu
• Set your sheet size in the Manufacturing Settings menu (I used the 48"x96"x7/16" OSB sheet that the CBA shop uses)
• Define your object size (this will scale the .stl to whatever size you like)
• You will see your model transformed into lots of layers and the layers laid out on the your defined sheet size on the right hand side
• You can change the direction which the slices are oriented using the Slice Direction tool
• The Assembly Steps too allows you to remove the layers piece by piece to see how you will assemble the pieces
• Click Get Plans to export the images of the pieces laid out on the sheets that you will cut out (export an EPS file to import directly into Illustrator)
• I needed to edit these files to remove the numbers and locating lines and points that 123D Make automatically puts into these plan files. I also needed to spread the parts out a bit more to make sure that the end mill had enough room to cut the pieces out without the excess sheet inbetween the pieces falling apart!

The pieces to be cut out:

3: MAKE THE SHOPBOT PATHS USING PATHWORKS 3.5D AND CUT THE PIECES OUT ON THE SHOPBOT

The pieces fit snugly onto one piece of 4x8' sheet, but Tom advised leaving at least 1" gap between the pieces, so the pieces took up 1.5 sheets in the end.

When making the profile cutting paths in the Pathworks software, I also added some tabs to the pieces to lightly connect the cut out pieces to the rest of the material, and prevent the cut out pieces from coming loose and getting caught up in the moving CNC arm. This worked well and left minimal rough edges to finish after.

4: FINISH THE PARTS

• Sand the rough edges on the belt sander
• Sand any other bits with sand paper
• Paint/stain - I wanted to create a visual contrast in the layers so painted the flat sections an aqua blue, and will paint the edges a dark wood stain

6: ASSEMBLE THE PIECES

I wanted the layers to be able to slide across each other as you rotate the layers to reconfigure the shape, so I put a layer of card between each layer to minimise the friction. I cut these discs out of thin card on the laser cutter.

The pieces will be finally assessmbled by stacking them on top of each other, using an aluminium rod to secure the layers, and wood glue to stick the top layers together.