Skin & Bone Exercise

Jon Martin

Jason Wheeler

original shape

skin and bone assembly

grasshopper production

We used the shape of a distorted torus to explore our skin

and bone study. Using Grasshopper, we were able to rib the

shape and lay out pieces for laser cutting. The process of

ribbing a 3d shape (especially one with a hole in it) as

opposed to a surface, proved to have many unexpected

challenges, such as assembly process.

We used 1/8" hardboard for the ribs. All the pieces fit on

three 18"x32" sheets

Laser Settings were:

Pass1 - power: 100; Speed : 10; PPI: 250

Pass2 - power: 100; Speed : 10; PPI: 250

Pass3 - power: 75; Speed : 12; PPI: 250

We gave a material thickness of .110" in grasshopper to

account for space made by the laser thickness. This was to

make it so the pieces fit together tightly, to eliminate gluing

(Not a good idea!) The tight fit made the pieces almost

impossible to fit together, so a little slack might have made

our assembly process a bit easier.

We used the cnc to fabricate the external shell pieces for

the torus out of a piece of rigid insulation. The big

experiment here was trying to flip the foam over once one

side was milled and continue milling the backside. This would

give us thin layers of foam that we would cut out with a

knife and coat with fiberglass.

The cnc took 9 hours total. We started with a 1/2" rough

cut with 50% stepover and finished with a 1/4" parallel finish

with 20% stepover. In the process of flipping to the

backside we realized the x-direction was off by 1". To fix

this we re-oriented the origin to -1" from where it was. Our

thought process was to mark the outline of the board with

marker so that when it was flipped it would sit in the same

spot, but something is wrong with that process (probably in

setting the origin.)

The most tedious process probably comes with finishing and

coating the shell pieces. We didn't anticipate the problems we

would encounter with resin's eating away at the foam. Our plan

was to fiber glass over the panels, Bondo and spot finish, then

coat with a glossy car paint. Our first test piece wound up

looking more like a skin graft than any type of sleek sexy panel.

To fix this we had to apply several layers of WeldBond (a kind of

tacky glue) to make a watertight seal over the foam. From there

we could apply the fiberglass resin in multiple layers and finish

with lots of sanding. Foam still proved to be too brittle and weak

to attain any kind of flawless surface.