STEP vs STL vs DXF for gears

The right export depends on what happens to the gear next. CAD and CNC machining want a solid model, 3D printers want a mesh, and laser or waterjet cutters want a flat outline. Picking the wrong one usually means rebuilding the geometry by hand.

Which file format should you use for gears?

DXF and SVG are flat outlines, so they cannot describe the twist of a helical tooth. For helical gears use STEP or STL.

STEP: solid models for CAD and machining

STEP (ISO 10303, .step or .stp) is the neutral solid-model format that SolidWorks, Fusion, Onshape, FreeCAD, Inventor and most CAM software import. A STEP gear arrives as a closed solid you can fillet, cut a keyway into, or generate toolpaths from, rather than a mesh you have to convert.

• Spur gears export as smooth boundary-representation (B-rep) solids, built with the OpenCascade geometry kernel.
• Helical gears export as faceted solids built from thin twisted slices of the tooth profile. More slices are used as the helix angle rises, to keep the twist accurate.
• GearStudio loads the CAD engine on demand (about 7 MB), so the first STEP export of a session needs an internet connection and takes a few seconds.

STL: meshes for 3D printing

STL describes a surface as triangles and nothing else. It is what slicers such as PrusaSlicer, Cura, Bambu Studio and OrcaSlicer expect, but it is awkward to edit in CAD because the curves are already broken into flat facets.

• Draft gives the smallest files, for quick test prints.
• Standard suits general printing.
• Fine follows the involute and root fillets closely, for high-resolution resin printing or when the mesh is going on to machining.

STL files carry no unit. GearStudio writes them in millimetres, which is what slicers assume, so imperial designs import at the right size.

DXF: 2D profiles for cutting

DXF is the standard input for laser cutters, waterjets, plasma tables and 2D routers. GearStudio writes AutoCAD R12 DXF, the oldest and most widely readable version, with each part on its own layer: sun, planet, ring, the ring's outer rim, and bores when you have set them.

The outlines are written as individual line segments rather than one large polyline. Some programs render a big closed polyline as a filled shape, which can hide the tooth profile behind a solid block; separate segments avoid that. Coordinates are in millimetres whatever unit system you designed in.

SVG: drawings and documentation

SVG is a vector drawing format that browsers, Inkscape, Illustrator and many laser-cutter programs open directly. It is handy for documentation and illustration. SVG exports use the units you designed in, millimetres or inches.

Why won’t exported planetary gears assemble in CAD?

A planetary set only assembles if every gear is rotated so its teeth sit in the gaps of its neighbours. GearStudio computes that tooth phasing for the sun, each planet and the ring, and applies it to every export. Whole-assembly exports place each part at its working position, so the set meshes as soon as it is imported. You can also export a single part, every part as a separate file in a ZIP, or, for STEP and STL, the assembly together with carrier plates.

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