# STL Shape Generator

> An STL shape generator is a tool that makes basic 3D shapes, or primitives, as printable files with exact dimensions. Kenerate's free generator builds 11 shapes in your browser, from boxes and cylinders to spheres, tori and stars. Set the size in millimetres, check it in 3D and download STL, 3MF, OBJ or GLB, flat on the bed.

URL: https://kenerateai.com/stl-shape-generator
Publisher: Kenerate AI (https://kenerateai.com)
Last updated: 2026-10-01

## Key facts
- Price: Free, no account
- Shapes: Box, rounded box, cylinder, tube / ring, cone, pyramid, sphere, dome, torus, hex prism, star
- Dimensions: 1–250 mm per parameter
- Smoothness: 8–128 segments for round shapes
- Placement: Centred, flat on Z = 0
- Output: STL, 3MF, OBJ, GLB
- Real dimensions: Width, depth, height, diameters and wall sizes in mm — what you type is what prints.
- Spacers, rings and tubes: Set an outer and inner diameter for washers, spacers, bushings and napkin rings.
- Smoothness control: More segments make rounder curves and bigger files; 64 is plenty for most prints.
- Combine in your slicer: Load several shapes and arrange them — or use them as modifiers and negative volumes.
- Pick: Each shape has its own parameters — size, height, inner diameter, points.
- Generate: The mesh is generated from those numbers with your chosen smoothness.
- Orient: It's turned Z-up, centred and placed on the bed.
- Export: STL, 3MF, OBJ or GLB downloads instantly.
- STL (Stereolithography): Triangle mesh (binary or ASCII); by 3D Systems, 1987. Holds: Triangle surfaces, Facet normals. Lacks: Colour and textures, Units, Materials. Best for: 3D printing — every slicer opens it. Opens in: Cura, PrusaSlicer, Bambu Studio, OrcaSlicer, Blender.
- 3MF (3D Manufacturing Format): ZIP package with XML; by 3MF Consortium, 2015. Holds: Meshes with units (millimetres), Colours and materials, Several objects and build plates. Lacks: Animation. Best for: Modern 3D printing and multi-colour prints. Opens in: Bambu Studio, PrusaSlicer, OrcaSlicer, Cura, Windows 3D Builder.

## Steps
1. Choose a shape — Box, cylinder, tube, cone, sphere, torus, star…
2. Type dimensions — Set each size in mm with the sliders.
3. Set smoothness — Raise segments for round shapes if you'll print them large.
4. Download — Save STL or 3MF and print.

## In depth

### Facets and file size
STL stores flat triangles, so curves are approximated [1]. Doubling the segment count roughly doubles the triangles of a cylinder and quadruples those of a sphere. Beyond what your nozzle can resolve, extra segments only grow the file.

### Printing primitives
Overhangs up to about 45° print without supports [11]: cones and pyramids print fine point-up, spheres need help underneath. Rings and tubes print best standing on their flat face.

### Fits and tolerances
When a generated part must fit another, leave clearance — about 0.3 mm for moving parts is a common guide [11].

References:
[1] Wikipedia — STL (file format): https://en.wikipedia.org/wiki/STL_(file_format)
[2] Wikipedia — Wavefront .obj file: https://en.wikipedia.org/wiki/Wavefront_.obj_file
[3] Wikipedia — FBX: https://en.wikipedia.org/wiki/FBX
[4] Khronos Group — glTF: https://www.khronos.org/gltf/
[5] 3MF Consortium — 3MF specification: https://3mf.io/specification/
[6] Wikipedia — Universal Scene Description (USD / USDZ): https://en.wikipedia.org/wiki/Universal_Scene_Description
[7] Wikipedia — PLY (file format): https://en.wikipedia.org/wiki/PLY_(file_format)
[8] Khronos Group — glTF 2.0 specification: https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html
[9] Apple — AR Quick Look: https://developer.apple.com/augmented-reality/quick-look/
[10] three.js — documentation: https://threejs.org/docs/
[11] Prusa Knowledge Base — Modeling with 3D printing in mind: https://help.prusa3d.com/article/modeling-with-3d-printing-in-mind_164135
[12] Prusa Blog — lithophanes and filament transparency: https://blog.prusa3d.com/lets-play-with-filament-transparency-how-to-make-amazing-lifelike-color-photos-with-just-a-simple-color-change_104338/
[13] Polymers (2024) 16(20):2862 — FFF parameters and translucency of PLA: https://doi.org/10.3390/polym16202862
[14] Wikipedia — Lithophane: https://en.wikipedia.org/wiki/Lithophane
[15] W3C — CSS Values and Units Level 3 (absolute lengths): https://www.w3.org/TR/css-values-3/
[16] Adobe Substance 3D — OpenGL vs DirectX normal maps: https://experienceleague.adobe.com/en/docs/substance-3d/bakers/common-questions/what-is-the-difference-between-the-opengl-and-directx-normal-format
[17] Blender Manual — Normal Map node: https://docs.blender.org/manual/en/latest/render/shader_nodes/displacement/normal_map.html
[18] Wikipedia — Normal mapping: https://en.wikipedia.org/wiki/Normal_mapping
[19] SIL Open Font License: https://openfontlicense.org/

## FAQ
Q: How do I make a 20 mm calibration cube?
A: Choose Box and set width, depth and height to 20 mm, then download. Measure the print with calipers to check your printer's accuracy.

Q: What does smoothness (segments) do?
A: Round shapes are made of flat facets. More segments give smoother curves and larger files; 64 is smooth at most sizes, 128 for large parts.

Q: Can I make a hollow cylinder?
A: Yes — use Tube / ring and set the inner diameter smaller than the outer one.

Q: Can I combine shapes?
A: Load several into your slicer and arrange them, or combine them in CAD. This tool makes one shape at a time.

Q: Do spheres need supports?
A: Usually, below the equator. Print a Dome (flat-bottomed half sphere) instead if you can.

Q: How do I make an STL file?
A: For simple solids, pick a shape here, type its sizes in millimetres and download. For anything else, export STL from CAD or Blender, convert another 3D file with the free converters, or generate a model with AI in the Kenerate 3D Studio (any paid plan or credit pack) and convert it.

Q: Is it free?
A: Yes, with no account.

## Related pages
- AI 3D Model Generator: https://kenerateai.com/ai-3d-model-generator
- Image to 3D: https://kenerateai.com/image-to-3d-converter
- AI STL Generator: https://kenerateai.com/ai-3d-printing-model-generator
- Text to 3D: https://kenerateai.com/text-to-3d-generator

## Sources
- Wikipedia — STL (file format): https://en.wikipedia.org/wiki/STL_(file_format)
- Wikipedia — Wavefront .obj file: https://en.wikipedia.org/wiki/Wavefront_.obj_file
- Wikipedia — FBX: https://en.wikipedia.org/wiki/FBX
- Khronos Group — glTF: https://www.khronos.org/gltf/
- 3MF Consortium — 3MF specification: https://3mf.io/specification/
- Wikipedia — Universal Scene Description (USD / USDZ): https://en.wikipedia.org/wiki/Universal_Scene_Description
- Wikipedia — PLY (file format): https://en.wikipedia.org/wiki/PLY_(file_format)
- Khronos Group — glTF 2.0 specification: https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html
- Apple — AR Quick Look: https://developer.apple.com/augmented-reality/quick-look/
- three.js — documentation: https://threejs.org/docs/
- Prusa Knowledge Base — Modeling with 3D printing in mind: https://help.prusa3d.com/article/modeling-with-3d-printing-in-mind_164135
- Prusa Blog — lithophanes and filament transparency: https://blog.prusa3d.com/lets-play-with-filament-transparency-how-to-make-amazing-lifelike-color-photos-with-just-a-simple-color-change_104338/
- Polymers (2024) 16(20):2862 — FFF parameters and translucency of PLA: https://doi.org/10.3390/polym16202862
- Wikipedia — Lithophane: https://en.wikipedia.org/wiki/Lithophane
- W3C — CSS Values and Units Level 3 (absolute lengths): https://www.w3.org/TR/css-values-3/
- Adobe Substance 3D — OpenGL vs DirectX normal maps: https://experienceleague.adobe.com/en/docs/substance-3d/bakers/common-questions/what-is-the-difference-between-the-opengl-and-directx-normal-format
- Blender Manual — Normal Map node: https://docs.blender.org/manual/en/latest/render/shader_nodes/displacement/normal_map.html
- Wikipedia — Normal mapping: https://en.wikipedia.org/wiki/Normal_mapping
- SIL Open Font License: https://openfontlicense.org/