HeeksCAD is a free and open source CAD application.
Functionality: Import solid models from STEP and IGES files. Draw construction geometry and lines and arcs. Create new primitive solids, or make solids by extruding a sketch or by making a lofted solid between sketches. Modify solids using blending, or boolean operations. Save IGES, STEP and STL. Printer plot the 2D geometry or to HPGL. Import and export dxf files; lines, arcs, ellipses, splines and polylines are supported. Use the geometric constraints solver to create accurate drawings from rough sketches.