Why was my model rejected?
Almost every rejection is the same thing: the file is a surface, not a solid. If the popup offers “Fix it for me”, click it, that rebuilds the model and generates in one step. If it has already run once and still failed, repair the file in Optimize or re-export it as a single closed body. Your exact message is explained below.
Every message a Meshcast generator can show you, what it actually means, and the fastest way past it. Nearly all of them come down to one thing: a mold is the space around your model, so the file has to describe a solid object rather than a surface.
Before anything else: if the popup offers “Fix it for me”, use it. It rebuilds your model as a clean solid and generates in the same click, and it resolves the majority of these. It is offered once per model: if it has already run and the generation still failed, the file needs the deeper fixes below.
Your STL isn’t watertight
It has gaps, holes, or surfaces that don’t join cleanly.
This is the most common one by a distance. A mold is the space around your model, so the generator has to know what is inside and what is outside. A mesh with holes has no answer.
- Click “Fix it for me” in the popup. We rebuild the model as a solid and generate straight away. It works for most sculpted and scanned files.
- If we already rebuilt it once and it still failed, the file has a deeper problem than holes: overlapping shells, or several separate pieces stacked together. Open it in Optimize, which shows what is wrong.
- Re-export as one closed body. In Blender: select all, Mesh › Clean Up › Merge by Distance, then export as a single object.
We couldn’t process this model
Shown for “memory access out of bounds” and similar engine errors.
The geometry crashed the engine outright, which almost always means self-intersecting or corrupt triangles rather than anything you did wrong.
- Use “Fix it for me”, the same rebuild fixes most of these.
- If it repeats on the same file, reload the page first: after this error the engine needs a fresh start.
- Very dense scans are the usual source. Run it through Optimize to simplify, then try again.
Your model could not be repaired within the 60 second budget
From the server-side tools (candle, plaster, silicone, vase, press).
We try to repair every upload before molding it. Sixty seconds is the limit, and a mesh that needs longer is badly enough broken that repairing it would change the shape anyway.
- Repair it yourself in Optimize and upload the result.
- Simplify first. Repair time depends on how tangled the mesh is, not how big it is: a 20,000-triangle scan full of self-intersections is far worse than a clean 200,000-triangle model.
The generator took too long to respond
Also “Couldn’t reach the generator”.
The first is our server still working when your browser gave up; the second is the connection dropping, usually on mobile.
- Try again. Nothing is charged for a failed generation.
- If it keeps happening on one model, it is genuinely heavy: use Model detail: Faster in Advanced, or simplify in Optimize.
That model was still too large to upload
A 413, after we already reduced it automatically.
Usually the repair pass rebuilt the mesh denser than it started, which happens with badly broken scans.
- Switch Model detail to Faster in Advanced.
- Or reduce it once in Optimize and upload that.
This model is too small to build a mold around
Also “too thin to mold”.
The mold needs real wall thickness around your model. Below a few millimetres per side there is nothing left to print.
- Drag Model size up in the sidebar. Aim for at least a few millimetres on every axis.
- Check the units your file was exported in. A model exported in metres arrives a thousand times too small.
One half came out empty
Shown as “the split seam is too far off-centre”.
The parting plane moved past the edge of your model, so one side of the cut has nothing in it.
- Move Seam position back toward the middle. The slider is now limited to your model's real extent, so this is rarer than it was.
- On a very flat or very tall model, try a different cut axis.
This file doesn’t look like a valid STL
Also “No printable 3D shape found in this 3MF”.
The bytes are not the format the name claims. We now read the file's actual content, so a renamed 3MF or OBJ just works; this message means it is none of the three.
- Re-export as STL, OBJ or 3MF from wherever you made it.
- If it is a sliced print file (a Bambu, Orca or PrusaSlicer project), it holds printer instructions and no shape. Download the model file instead of the print profile.
We couldn’t read a clear shape from this image
From the image-based tools (cutter, lithophane, embosser).
The tracer needs an obvious light/dark split to find an outline.
- Use a bolder, higher-contrast picture with a plain background.
- A silhouette or logo works far better than a photo.
Still stuck
Send us the file through support and say which tool you were using. A real file beats a description every time, and a broken mesh usually tells us in seconds what no screenshot can.