Open Christmas Ball with Ribs 2025

A beautiful ball to accent your Christmas tree!

This is a fun and incredibly lightweight ornament.

I've provided my PrusaSlicer project file and GCODE for a Prusa MK3S+ printer.

Yes, you need supports - and not just at the base. You need at least 1 row of supports for the arms halfway up (I used 2 rows) to keep the arms from breaking as they print. Once they merge at the top, they are strong. Until then, they are weak and the taller they get, the weaker they get. Just use paint-on organic supports like I show in the screenshot. You also need supports for the roof of the ball. Supports for the loop are optional, but they help. The supports release effortlessly when I print with them and help guarantee a good print.

Use the Classic perimeter generator. I used 1 perimeter, no infill, and top and bottom set to 3. Then, I used height range modifiers to add an extra perimeter, 25% lightning infill, and top/bottom to 4 for 0-7.55mm. I also added an extra perimeter, 20% lightning infill, and top/bottom to 4 for 67.3 - 79.2mm. Above that, no infill with top/bottom set to 6. I usually print external perimeters first.