Gömböc

thingiverse

A gömböc or gomboc is a three-dimensional, convex body that rests on a flat surface with one stable and one unstable point of equilibrium. Russian mathematician Vladimir Arnold conjectured its existence in 1995, and Hungarian scientists Gábor Domokos and Péter Várkonyi proved it in 2006. This is a rescaled Gömböc from seanmichaelragan, separated into two parts for easier printing and possible material addition. Each shell measures 90 mm x 100 mm. Print two shells and bond them together to create a Gömböc! Fill the shells with synthetic plaster, which is inexpensive, liquid enough to fill half-shells, dries quickly, and is heavy. Bond the shells together at the end. The picture shows sanded outer perimeters and added smoothing product for a good-looking Gömböc. Printing parameters: Shell thickness: 0.4 mm Layer thickness: 0.2mm Fill density: 10% Bottom thickness: 0 mm Top thickness: 0.4mm Speed: Outer perimeter: 30mm/s Filling: 50mm/s Printing time: approximately 3h20 for each shell Caution: DO NOT use epoxy, as it gets extremely hot when polymerizing and can melt the PLA. Also, DO NOT use polyester due to solvent issues that can also melt the PLA. Disclaimer: This is not a real Gömböc in a mathematical sense. The real one is fully homogeneous with the correct shape, resulting in the intended behavior. Printing this Gömböc alters its material homogeneity due to the 10% filling percentage and adds weight to the bottom for it to work as expected. Don't worry if the shape or center of gravity isn't exactly right; your Gömböc may not be a perfect mono-monostable object, potentially meeting other unstable equilibrium points due to imperfections in shape or balance. But finding these points is nearly impossible, and your Gömböc will behave as expected in real life. For those seeking perfection, visit the Gömböc website at http://gomboc-shop.com/ for a mathematically precise Gömböc.