Gear generator, with STL, SVG and DXF export

Pick the module (the size of the teeth) and the number of teeth for each gear in the generator at the top of this page, set the face width and the bore, and look at the checks under the preview. Then download the STL files, or both in one ZIP, and slice them like any other part. The gears are built flat on Z = 0, so they print flat on the bed with the axis vertical. Keep the backlash inside the FDM range 0.15 to 0.25 mm (rule dfam.feature.pip_mesh_backlash_mm) so printed teeth do not fuse, and print a test pair before a long print. The default pair (module 2, 20 and 40 teeth) came out as 2,720 and 5,280 triangles, 132.9 KB and 257.9 KB of STL and a 74.7 KB ZIP.

The module m is the pitch diameter divided by the number of teeth, in millimetres: m = d / z. It sets the size of the tooth, and two gears mesh only if they have the same module (and the same pressure angle). The preferred values of the ISO 54 series are 0.5, 0.8, 1, 1.25, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 10, 12, 16, 20 mm (rule mech.gear.module_standard_series). Inch based gears use the diametral pitch instead, P = 25.4 / m, so module 2 is about 12.7 teeth per inch.

For the standard 20 degree pressure angle a gear needs at least 17 teeth to avoid undercut (rule mech.gear.min_teeth_20deg), which is the 2 / sin^2 of the angle rounded to a whole tooth (17.1). Down to 14 teeth the undercut is slight (rule mechanical.spur_gear.gear_min_tooth_count_with_slight_undercut). Below that the root of the tooth is cut away in a real gear, and the tooth gets weak. The generator warns when a gear is under the limit and when the tip of one gear would dig into the root of the other. It does not offer profile shift, the usual cure for a small pinion, so use more teeth.

For two spur gears of the same module, a = m x (z1 + z2) / 2. The default pair, module 2 with 20 and 40 teeth, sits at 2 x 60 / 2 = 60 mm. For helical gears with the normal module m and the helix angle beta, a = m x (z1 + z2) / (2 x cos beta). The page shows the exact value, and the 3D preview places the gears at it. The backlash is made by thinning the teeth, not by moving the gears apart, so print the pair and mount the shafts at exactly this distance.

The ratio is the teeth of the driven gear over the teeth of the driver, i = z2 / z1, with gear 1 as the driver. 40 and 20 teeth give 2 : 1, so the output turns at half the speed and with twice the torque, less friction. One stage should stay between 1 and 10 (rule mech.gear.ratio_per_stage); for more, chain two stages. For gear trains and planetary gearboxes use the Gear Designer.

For an FDM printed pair the rules core gives 0.15 to 0.25 mm (rule dfam.feature.pip_mesh_backlash_mm), and 0.04 to 0.25 mm (rule mech.gear.backlash_range, stated for modules 1 to 5) for gears in general. The default here is 0.2 mm. The page measures backlash along the pitch circle and takes half of it off the tooth thickness of each gear. Printers differ, so print a test pair and change the value if the pair binds or rattles. The rules core has no backlash figure for resin or powder printers, so none is given for them.

Yes. Both files hold the 2D profile of the gears in millimetres, with 1 unit = 1 mm. The two gears sit side by side with a 5 mm gap so you can cut them apart, the DXF has one layer per gear, and the bore with its keyway is a hole in the profile. The outline is the nominal one: a laser removes a strip of material, so measure the kerf on your machine and allow for it in the backlash. The files hold the profile in the plane of rotation, so for a helical gear they are not a flat cutting pattern. The bore is drawn as a 40 sided polygon, the same as in the STL.

Yes. There is no account, no daily limit and no watermark on the files.

No. The gears are built inside your browser tab by code that runs on your own machine, using a geometry engine compiled to WebAssembly. The page loads its scripts and that engine from edufacturing.com when you open it, and it sends no design, no settings and no file anywhere.

You can convert the STL with the STL to STEP converter, which is free and runs in your browser. The STEP file it makes from triangles is faceted: the shape is kept, but every tooth flank stays a mesh of small flat faces. The converter does not recognise the involute curve, so do not expect an editable tooth profile in your CAD program. For a part you will edit in CAD, build the gear in a parametric CAD tool that draws the involute, and use the STL here for printing and the DXF for the profile.

Spur gears have straight teeth parallel to the shaft. Helical gears have teeth twisted along the face, so the teeth enter the mesh gradually, which is quieter and adds an overlap to the contact ratio, but pushes the shaft sideways. The rules core gives a helix angle of 15 to 45 degrees (rule mech.gear.helical_helix_angle). The two gears of a helical pair need opposite hands: the generator makes gear 1 right handed and gear 2 left handed, and the file names say so. The module you enter for a helical gear is the normal module.