Customizable Rounded Cube Pen Holder

#Customizable Rounded Cube Pen Holder

##by Robert Halter

Licensed: Creative Commons - Attribution - Non-Commercial - Share Alike (by-nc-sa)
see: http://en.wikipedia.org/wiki/Creative_Commons

##parametrizable user values
- *outer dimension* of hole Cube Pen Holder [mm] = 80 Range: [55:90]

##hidden parameter
- factor for *dimension to radius* [Number] = 12 / 80 // 0.15
- *wall thinkness* [mm] = 2.0 // [2:3]
- $fn = 50 // 50 for production, 15 for debugging
makes the Customizer slow but give a finer rounding