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From a ChatGPT description to a file
ChatGPT wrote the part. SpeakCAD turns it into the STL, 3MF or G-code.
ChatGPT, Claude and Gemini are good at working out what a part should be: the outer size, the wall thickness, where the holes and cutouts go. The file is where they fall short: ChatGPT can write a basic STL for a box or a cylinder, not a checked, printable model of the part it just described. Paste that description, exactly as the assistant wrote it, into SpeakCAD: it becomes a parametric model you can see and edit, then a print-ready STL or 3MF, or G-code already sliced for your printer. On a phone or a computer, nothing to install.
How it works
Ask the assistant, paste the answer, print the part
The spec an assistant writes is already a good prompt: it names every dimension in millimetres and says what the part mates with. Keep it whole and paste it as is.2
Paste it in the box above
Paste the whole description and continue: after you sign up, it is waiting for you in the editor. The numbers are used exactly; anything left open, the AI decides and tells you what it assumed. Sending it is one AI request (2 credits). OpenSCAD code works too: pasted in the box, it opens as a project in your account.3
Check the render
The first render usually appears within a minute or two: a new part goes to the strongest models, which reason through the geometry, and small edits land in seconds. Turn the part, tap a face to read its size, open the dimensions panel to see every number it was built from, and see whether it has overhangs that would need supports.4
Fix it in one sentence
“Move the USB cutout 3 mm to the left”, “the lid is too loose”: each change is a request (2 credits) and leaves the rest of the part alone, and the previous version stays visible as a ghost. Typing a new number in the dimensions panel is free.5
Download STL, 3MF or sliced G-code
Download a watertight STL or 3MF for your own slicer (10 credits), or pick your printer (380+ models, official OrcaSlicer profiles) and download G-code that goes straight to the printer.What one part costs
| Step | Cost |
|---|---|
| Live demo: 3 AI edits of a real part, no account | Free |
| Sending the description (one AI request) | 2 credits |
| Each change by chat | 2 credits |
| Typing a new number in the dimensions panel, undo | Free |
| STL or 3MF download | 10 credits; small fixes after it re-download free |
| G-code sliced for your printer | +5 credits per slice without Pro or Unlimited |
| Starter credits | $5 once = 75 credits, about 4 parts with a couple of edits each; no subscription |
| Pro | $9.99 a month: 200 credits a month, sliced G-code included |
| Unlimited | $24.99 a month: unlimited requests and downloads |
Descriptions in the style assistants write them
These are typical of what people paste after a conversation with ChatGPT. Every number is honoured; the print rules (wall thickness, clearances, a flat base) are added for you.“Create a functional two-piece egg-shaped container for FDM printing. Assembled height exactly 100 mm, maximum diameter exactly 70 mm. Two separate parts: a lower cup and an upper cap joined by a 6 mm tall friction lip with 0.3 mm clearance. Wall thickness 2 mm. Both parts must sit flat on the bed with the open side up.”
Open this prompt in the editor“Design a compact 3D-printable electronics enclosure for a 58 x 38 mm PCB with four M2.5 mounting holes 3 mm from each corner. Internal height 18 mm above the standoffs. USB-C opening 9 x 3.5 mm centred on one short side, a 12 x 12 mm push-button hole on top, slot vents on both long sides. Lid held by four M3 screws into corner pillars. Walls 2 mm.”
Open this prompt in the editor“Make a wall bracket for a 30 mm diameter pipe: a 60 x 40 mm back plate 4 mm thick with two 5 mm countersunk screw holes 40 mm apart, a half-round cradle 20 mm deep, and 2 mm fillets on every outside edge. Designed for PETG.”
Open this prompt in the editorWhat ChatGPT can and cannot hand you
ChatGPT can reason about a part and write text, including OpenSCAD code, and its Python tool can write a simple STL (often ASCII) for boxes and cylinders. What it does not have is a CAD workflow around that file: it cannot compile OpenSCAD, gives you no live 3D model to check and edit, does not apply print rules for walls and clearances, and cannot slice with your printer's profile. So the STL it attaches for a real part is usually crude or broken, and the OpenSCAD it writes may have zero-thickness walls, overlapping solids or a hole that goes nowhere. You find out in the slicer.
SpeakCAD is the missing half. The AI inside it writes a parametric OpenSCAD program from your description, the browser compiles it into exact geometry, applies FDM design rules (minimum wall thickness, fit clearances, a flat face on the bed) and checks overhangs. What you download is a watertight, manifold mesh in millimetres, or G-code sliced with your printer's own profile.
ChatGPT gave me an STL, or STL text
If ChatGPT offered a download, or printed a block that starts with solid and goes on with facet normal … outer loop … vertex, that is an STL (the second one in ASCII form). Download the file, or copy the whole block into a plain-text file named part.stl on a computer. Then attach it in the SpeakCAD chat and say what to change: “make it 4 mm taller”, “add two M3 holes 40 mm apart on the back”. SpeakCAD measures its outer size and adds, cuts or rebuilds around it; that is a request like any other (2 credits). The details are on edit an STL.
Often the faster route is the description itself: paste what ChatGPT wrote about the part in the box at the top of this page, and SpeakCAD builds it from the numbers instead of from ChatGPT's triangles.
ChatGPT's OpenSCAD does not compile
It happens often: include <BOSL2/std.scad> or MCAD calls for libraries that are not installed, a missing semicolon or bracket, a function OpenSCAD does not have. And code that compiles can still be wrong: a variable assigned twice (OpenSCAD keeps the last value for the whole scope), or a difference() whose cutter only touches the surface and leaves a paper-thin skin.
Paste the code in the box at the top of this page: after you sign up it opens as a project in your account, where the browser compiles it. When it fails, or when you want it changed, ask the AI in the chat: that is one request (2 credits), and the AI repairs the program or rewrites it as a clean parametric model with the same dimensions. BOSL2 and MCAD are not available, so library calls are replaced with plain OpenSCAD helper modules. OpenSCAD itself is a desktop program; SpeakCAD compiles it in the browser tab, so this works in Safari on an iPhone too.
What to keep from the ChatGPT conversation
- Every dimension. Assistants are good at listing them. SpeakCAD uses them exactly, so a 62 x 42 mm hole pattern comes out at 62 x 42 mm.
- What the part mates with. "Fits a 20 mm pipe", "holds a 0.96 inch OLED module", "snaps onto a 3 mm shelf". That is what sets the clearances.
- Material and orientation, if it said so. "For PETG-CF", "printed lid-side down" are used.
- Its OpenSCAD, if it wrote any. Paste the code with what you want changed: the design continues from there instead of starting over.
Leave out the pep talk and the printing instructions the assistant added; they do not hurt, but they are not geometry.
Three ways in
- Paste. Copy the description into the box at the top of this page and continue. Works with any assistant, no setup.
- The SpeakCAD connector. Add the MCP server to ChatGPT or Claude and the assistant hands your description to SpeakCAD itself, or finds a ready-made model in the library. See the connector guide.
- A photo with a ruler. When the part exists and the assistant was only describing it, two phone photos next to a ruler give a parametric copy. See duplicate an object.
What comes out
- STL or 3MF, watertight and in millimetres, ready for PrusaSlicer, Bambu Studio, OrcaSlicer or Cura without repair.
- G-code sliced for your printer, using the official OrcaSlicer profile of 380+ printers (Bambu Lab, Prusa, Creality, Elegoo, Anycubic, Sovol, Qidi, Voron and others), with print profile, filament, infill, walls and supports chosen in the download dialog. Bambu printers get a sliced .gcode.3mf. See your printer's page.
- The OpenSCAD source, if you want to keep editing by hand.
Where it is not the right tool
SpeakCAD builds functional parts: enclosures, brackets, holders, adapters, stands, organizers, replacement clips and knobs, cookie cutters, gears. If ChatGPT described a figurine, a sculpture or a character, a mesh generator such as Meshy or Tripo is the better fit; the comparison explains where each one wins. For typing a part from scratch rather than pasting one, see text to STL.
Questions
Only simple ones. Its Python tool can write a basic STL (often ASCII) for boxes and cylinders, but it cannot compile OpenSCAD, gives you no live 3D model to check and edit, does not apply print rules for walls and clearances, and cannot slice with your printer's profile; its files often need repair. Paste the description or the code into SpeakCAD instead: the AI writes a parametric model from it, the browser compiles it and you download a watertight STL, 3MF or G-code sliced for your printer.
Yes. Paste the code in the box at the top of this page: after you sign up it opens as a project in your account, where the browser compiles it. To change it, or if it does not compile, ask the AI in the chat (one request, 2 credits): it edits the program, or rewrites it as a clean parametric model with the same dimensions.
Paste it into SpeakCAD and ask the AI to fix it: that is one request (2 credits). It repairs the syntax, replaces BOSL2 or MCAD calls with plain OpenSCAD (those libraries are not available here), removes zero-thickness walls, and keeps every dimension the code had. The usual causes are a library include, a missing semicolon or bracket, and functions OpenSCAD does not have.
Not the OpenSCAD app, which is a desktop program for Windows, macOS and Linux. Browser builds of OpenSCAD compiled to WebAssembly run in Safari, and SpeakCAD is one: paste the code in the box at the top of this page and, once you have signed up, it opens as a project that compiles in the tab, on an iPhone as on a computer. Asking the AI to change or repair the code is a request (2 credits); downloading the STL or 3MF is 10 credits.
Yes. The source of the description does not matter; what matters is that it names the dimensions in millimetres and says what the part has to fit. ChatGPT and Claude can also use the SpeakCAD connector (MCP) to send the description across directly.
Yes. Every size in the description becomes a named parameter of the model and is used to the millimetre. Sizes you did not give are chosen from FDM design rules and reported in the reply, and you can change any of them by chat or by typing a number in the dimensions panel.
Yes. Copy the description in the ChatGPT app, open this page in Safari or Chrome, paste it in the box and continue; the model renders in the same tab. STL, 3MF and G-code download to Files or Downloads. Nothing to install.
The first render usually appears within a minute or two: a new part goes to the strongest models, which reason through the geometry, and small edits land in seconds. A typical functional part, with a couple of edits and a dimension check, is a downloaded file in about 10 to 15 minutes.
Starter credits: 75 credits for $5 once (50 + 25 free), no subscription. Pro $9.99/mo (200 credits a month, sliced G-code included); Unlimited $24.99/mo (unlimited requests and downloads). Turning the model around in 3D and changing its numbers in the viewer are free; each AI request (a new part or a chat edit) spends 2 credits, whichever model answers; a download spends 10 credits (+5 for G-code sliced for your printer without Pro or Unlimited); small fixes after a download re-download free. The live demo (3 AI edits of a real part) needs no account.
Read more
Text to STLDescribe a part from scratch, in millimetres, and download the STL.Edit an STL you already haveUpload a download from Thingiverse or Printables, or ChatGPT's STL, and say what to change.Best AI tools for 3D printingAI CAD tools for parts with exact millimetres, mesh generators for figurines: which one fits your print.Use SpeakCAD from ChatGPT or ClaudeAdd the connector and let the assistant hand the part over itself.Prompting for CADWhat a good part description contains, and what to leave out.G-code for your printer380+ printers with their official slicing profiles, no slicer to install.