--- title: "What to check before you download a generated 3D model" description: "A one-minute checklist for a generated model: assumptions, dimensions, mating faces, the bed, overhangs, walls and the ghost of the last edit. Spend credits on a file that prints." canonical: https://speakcad.com/guides/check-a-model-before-you-download published: 2026-09-09 updated: 2026-09-23 publisher: SpeakCAD --- # What to check before you download a generated 3D model > A one-minute checklist for a generated model: assumptions, dimensions, mating faces, the bed, overhangs, walls and the ghost of the last edit. Spend credits on a file that prints. Turning the model around and reading its dimensions are free on every plan; AI requests are what cost credits (and, without a plan, downloads of AI work). So the moment before the download is where a minute of checking pays for itself, and the editor puts everything you need on one screen. ## Steps 1. **Read the assumption summary.** Under every render the AI lists what it decided on your behalf: wall thickness, clearances, fillets, orientation. If one of them is wrong for your printer or material, say so before you download. 2. **Compare the outside dimensions.** The readout under the model shows length, width and height. Check them against the space the part has to fit in and against your bed size. 3. **Tap the faces that matter.** Tap a face to read its size. Do this for the mating dimensions: the hole, the slot, the pocket, the lip. These are the numbers that decide whether the part fits. 4. **Look at it from below.** Orbit under the model. The bottom should be flat on the bed and there should be no floating geometry. Overhangs steeper than 45 degrees show up here. 5. **Check the ghost after an edit.** The previous version is shown as a ghost. Confirm that only the thing you asked for moved. If something else changed, say so; SpeakCAD moves up to a stronger model when an answer misses. 6. **Download the format your slicer prefers.** 3MF carries the unit and the name and keeps multiple parts separate; STL is universal. Both come from the same watertight mesh. ## Why check at all The model is generated from your description, so the most common problem is not a bad model but a description that missed something: a taper, a cable in the way, a wall the part has to clear. The checks below catch those in under a minute, before the printer spends two hours on them. ## 1. The assumption summary Every render comes with a short list of decisions: "2 mm walls, 0.2 mm press-fit clearance on the shaft, 3 mm standoffs, 0.5 mm chamfer on the base, printed open side up". Read it. If you print PETG and know your printer runs a little wide, "0.1 mm more clearance everywhere" is a one-line fix. If the part will take load, "2.5 mm walls" is another. ## 2. The dimensions readout Length, width and height are shown under the model, along with volume. The volume is a sanity check on wall thickness (a box that reports far more material than expected has solid walls) and a rough guide to print time. The dimensions tell you whether it fits the bed (220 mm is the default virtual bed; say your bed size if it is smaller) and the space it is going into. ## 3. Tap the mating faces Overall size rarely matters to the tenth of a millimetre. The hole for the shaft does. Tap the inside of a hole and the readout shows its diameter; tap a slot and it shows the width; tap the floor of a pocket and it shows the depth. The dimensions panel lists every named number in the model as well, so you can type the one you measured with callipers directly. ## 4. Look from underneath Orbit below the bed. Three things to look for: - **A flat bottom.** The largest flat face should be on the bed. If it is not, "lay it on its back" or "print it on the long side" reorients the part. - **Floating geometry.** A feature that starts above the bed with nothing under it will not print. The AI avoids this, but a strange request can produce it. - **Overhangs.** Faces steeper than about 45 degrees from vertical need supports. A chamfer instead of a horizontal step usually removes the need; ask for one. ## 5. Wall thickness Walls under about 1.2 mm print as a single fragile perimeter or not at all at a 0.4 mm nozzle. The AI's default is at least 1.2 mm and usually 2, but if you asked for a very thin feature (a living hinge, a flex clip) check that the number is deliberate. Wireframe mode shows the geometry the slicer will see, including any sliver walls where two features nearly meet. ## 6. The ghost After an edit, the previous version is drawn faintly behind the new one. This is the fastest way to confirm that "lip 5 mm" changed the lip and nothing else. If the ghost shows the whole part shifted or a hole moved, say "keep everything else where it was" and the AI re-applies the edit narrowly. ## 7. Multi-part files A box and its lid, or a test coupon and the full part, are laid side by side. In a 3MF they are separate objects you can print one at a time; in an STL they are one object. Pick the format to match how you will print. ## Then download STL or 3MF, included in every plan (4 credits without one). If the print reveals something the checks could not (the shelf was 18 mm, not 16), the fix is a sentence and the corrected file re-downloads free. The checklist is not about avoiding every reprint; it is about making sure the first print teaches you something the screen could not. ## About SpeakCAD SpeakCAD is the most intuitive CAD for 3D printing, made for people who own a 3D printer and need a part that fits something they have: tap a face and type a size to shape it with simple tools, or describe it to the AI, on your phone or computer, and download a print-ready STL, 3MF or G-code sliced for your printer. SpeakCAD works inside ChatGPT and Claude as a plugin (an MCP server): ask the assistant for a part with its measurements and SpeakCAD's own CAD AI designs it, shows it in 3D in the chat and hands over a print-ready STL, 3MF or G-code sliced for your printer. - Live demo, no account: https://speakcad.com/demo - In ChatGPT, Claude and other MCP clients: https://speakcad.com/chatgpt-plugin, https://speakcad.com/claude-connector, https://speakcad.com/mcp-server - Pricing: https://speakcad.com/pricing - FAQ: https://speakcad.com/faq - Site index for AI assistants: https://speakcad.com/llms.txt