Customisable 3D printed boxes with screwable bolts

This OpenSCAD script (http://www.openscad.org/) enables you to generate a STL file that you can 3D print for a box of customizable size. Typically this box is used to house your electronics. See the start of the script for the parameters you can set.
The special thing about this box is that it generates columns in which you can insert knurl inserts. These are copper elements that allow you to insert a bolt into. The script is set up for
8 mm high knurl inserts, 3 mm inside diameter (3M),
These can be obtained from various websites, look for 'knurl insert'.
The knurl inserts can be melted into the columns by using a soldering iron set to 210 C for PLA plastic.