SketchUp is known for its "Push and Pull" method of modeling. The free web version is excellent for creating clean, architectural jewelry designs.

To export files specifically for 3D printing (STL), you may need to use specific web-based converters or plugins. 5. Meshmixer (Best for 3D Print Preparation)

These software options can help you create, design, and visualize your jewelry designs without spending a fortune. However, keep in mind that some of these free versions may have limitations or watermarks on exported designs.