Week 04 - Feb 8st 2012 - Computer-Controlled Cutting
Weekly Assignment - Model a press-fit kit
The assignment this week was to produce a press-fit kit using corrugated cardboard as the construction material. I decided to build a model of DNA as this would fulfil the criteria of designing and manufacturing a modular construction kit, and also counld serve as the basis for an educational product.
Component design
I began by designing the shapes in Sketchup, as this is an easy way of developing geometric designs and allowed me to develop how the pieces would fit together.
I then transferred the shapes to Adobe Illustrator to generate 2d representations. The notches were implemented using the Symbols function, allowing batch modification of cutout thickness once the optimal measurement had been determined.
Kerf characteristics
In order to have components that slotted together and held, it was necessary to laser cut a test shape from the cardboard. I decided to try 6mm and 10mm deep cutouts, with a variety of widths to see what dimension gave the best fit.
While the cardboard measured 2.7mm thick, the best joint dimension for a strong hold was 1.9mm for 6mm notches, and 2.1mm for 10mm notches.
Kit assembly
With 6mm x 1.9mm notches applied to my layout, I laser cut and assembled the pieces for my helix.
(CGI to remove the wire and tape central support to follow)
Lessons learned
My helix didn't hold together very well, although I was pleased with the quality of the individual base-pairs. The instability came from flexibility introduced by using very long supports (for the phosphate backbone). This put a lot of lateral flex on these joints which could not be supported by the cardboard. This design may work better with acrylic, or more likely would require additional 'props' vertically between the base-pairs.