Hyperboloid Pen Holder

A strong and stylish pen holder that prints without supports and requires 0% infill!

The STL file has a height of 100 mm, an outer diameter of 90 mm, and an approximate inner diameter of 56.81 mm. There are 12 rods in each direction, connecting points that are 90º apart. The rods have a diameter of 4 mm, while the base is 2 mm thick (=rod radius).

You can change all those settings using the attached parametric OpenScad file. The inner diameter is computed based on the other parameters and shown in the preview render (see last pictures above).

About its geometry

Believe it or not, there are no curves in this design! All these rods are just straight cylinders at an angle, forming a Hyperboloid of One Sheet, one of the three doubly ruled surfaces that exists.

The hyperboloid of one sheet have nice structural properties that have been exploited in architecture before. Here, it provides rigidity and strength to the walls of this pen holder.

Recommended print settings

• 0.4 Nozzle
• 0.2 Layer Height
• 2 walls
• 0% Infill
• No Supports
• High retraction to avoid stringing (I've used 5mm in my Mini+)
• Concentric top and bottom layers (this is an aesthetic choice)