Pick your pinion's module and pressure angle, then the number of teeth — the rack is exactly that many pitches long, with both ends in the middle of a tooth space, so printed segments join into a longer run. It uses the ISO 53 tooth form our spur gears are hobbed from, so the pair meshes with the designed 0.2 mm of backlash.
The real generator runs in your browser: set the parameters, then download STEP or STL. Nothing to install, no sign-up.
The first open downloads the CAD engine (about 20 MB).
Each parameter below rebuilds real geometry on every change — this is parametric CAD, not a scaled mesh.
| Parameter | Default | Range | What it does |
|---|---|---|---|
| ModuleMODULE | 2 mm | 1 – 5 | Must match the pinion's. |
| Pressure anglePRESSURE_ANGLE | 20 ° | 20 / 25 | 20° on every catalogue rack; 25° only to match a 25° pinion. |
| Number of teethTEETH | 15 | 2 – 120 | Length = teeth × π × module; 15 at module 2 is MISUMI's 100 mm stock rack (94.25 mm). |
| Face widthFACE_WIDTH | 10 mm | 3 – 40 | At least the pinion's face width. |
| Height to pitch linePITCH_HEIGHT | 18 mm | 9 – 60 | 18 at module 2 is the pitch line of a square-section rack (HPC, MISUMI stainless: 9 × module); KHK and MISUMI steel racks use 23. |
| Mounting holesHOLES | 0 | 0 – 6 | Sideways through the face width, evenly spaced, like KHK SRFD racks. |
| ScrewSCREW | M4 | M3 / M4 / M5 / M6 | Hole and counterbore sizes from MISUMI's rack tables. |
| CounterboredCOUNTERBORE | on | on / off | Sinks the screw heads into the -Y face. |
Every parameter can go in the page's link, so one link opens exactly the part you want. Example (Module 1.5, 40 teeth (188.5 mm), 2 mounting holes):https://www.forgent3d.com/en/generators/gear-rack-generator?MODULE=1.5&TEETH=40&HOLES=2
STEP AP214 in millimetres, exact B-rep — it opens directly in SolidWorks, Fusion, FreeCAD, Onshape or Inventor, and goes straight into a CNC quote form. STL for the slicer is one click too.
| This generator | Typical online STL generator | Vendor CAD library | |
|---|---|---|---|
| Any size within the range | Yes | Yes | Catalog sizes only |
| STEP with exact surfaces | Yes | Usually an STL mesh only | Yes |
| Changes the sliders don't cover | “AI edit” on the page | No | No |
| Account needed to download | No | Usually no | Often |
Every parameter is a link parameter; the link below opens the example part. ChatGPT, Claude or any assistant can write one like it from the parameter list (names, units, ranges) at: parameter list (JSON)
Example: https://www.forgent3d.com/en/generators/gear-rack-generator?MODULE=1.5&TEETH=40&HOLES=2
Press “AI edit” in the generator and say what to change — a keyway, holes, a different shape. The AI edits the part's model.py and it rebuilds in your browser, with undo. A few edits a day are free without signing in; to keep the result or go further, copy it into your models and continue with the AI agent.
Edit with AI →For bigger changes, several rounds, or a part you want to keep: copy it into your models (free account). The Forgent3D AI agent reads the model.py, edits it, rebuilds it and checks the result itself.
Copy and continue with the AI agent →Its centre sits at the rack's pitch-line height plus the pinion's pitch radius (module × teeth / 2): with the defaults, 18 + 20 = 38 mm for a 20-tooth module-2 pinion. That is the mounting distance KHK gives for any rack and pinion.
At module 2, 40 teeth (251.33 mm) lying straight on a 256 mm bed, or 53 teeth across its diagonal; 35 teeth (219.91 mm, no room left for a brim) on a 220 mm bed. For a longer run, print segments and join them — the ends are made for it.
Gear printing guides lay the tooth profile flat on the bed — smooth flanks, strong roots — so print the rack lying on its side; the side mounting holes then come out as clean vertical holes. PETG for a working rack, 4 or more walls.
200 / (π × 2) rounds down to 31 teeth, 194.78 mm: https://www.forgent3d.com/en/generators/gear-rack-generator?MODULE=2&TEETH=31 — the pinion's centre then sits 18 + 20 = 38 mm above the rack's bottom (pitch-line height + pitch radius). Make the pinion with the spur gear generator at the same module.
Yes: every rack here is a whole number of pitches with both ends mid-space. Butt them, mesh a short piece of rack across the joint to set the pitch — the method KHK and MISUMI give for their racks — then screw or pin both to the base.
Yes. Models you generate and the STL / STEP files you export are yours: print them, sell the prints, or use them in a product. No attribution to Forgent3D is required.
Already have your own .scad file? Convert OpenSCAD to STEP → · Preview it in the browser →
