Two numbers you already know, and you will find out before the print does. Most walls that look fine in Rhino disappear somewhere between 1:200 and 1:500.
| Scale | Model size | Your walls | Result |
|---|---|---|---|
| 1:500 | 80.0 mm | 0.40 mm | Disappears |
| 1:200 | 200 mm | 1.00 mm | Prints |
| 1:100 | 400 mm2 sections | 2.00 mm | Prints |
| 1:50 | 800 mm4 sections | 4.00 mm | Prints |
| 1:20 | 2000 mm8 sections | 10.0 mm | Prints |
Smallest you can safely go: 1:200
At 1:200 the model is 200 mm along its longest edge and your 200 mm walls come out 1.00 mm thick, which prints. That is on the thin side — it prints properly, but handle the model by its base rather than its walls.
Rule of thumb: whatever scale you print at, your thinnest wall needs to be at least that number × 0.8 mm in real life. At 1:200 that is 160 mm.
Scale is the one thing that changes every dimension in your model at once, and the only one nobody checks. A 200 mm wall is perfectly ordinary at full size. At 1:100 it is 2 mm and prints solidly. At 1:200 it is 1 mm — printable, but thin enough to flex. At 1:500 it is 0.4 mm, which is one line of plastic with nothing behind it.
The file still exports. The slicer still opens it. The printer still runs. What comes off the plate is a model with holes where the walls were, and it is usually discovered the night before a jury, which is the only night it cannot be discovered.
The fix is nearly always one of two things, and both are easier before you print: thicken the thin elements in the model, or print at a larger scale and accept that the model comes in sections. The table above tells you which.
Scale is the failure that costs a jury. The export settings are the one that costs an afternoon — wrong units, open edges, a mesh that is not watertight. The export guide covers Revit, Rhino, SketchUp and ArchiCAD, with the settings for each.