Requirements for STL files

The design of the 3D models also contributes to high-quality manufacturing results. Problematic STL files can result in flawed manufacturing results or broken tools.

In the following, we provide a few tips to avoid common mistakes when you prepare STL files. Correct errors in STL files with your CAD application or export them with suitable settings.

Common errors in the 3D mesh

These errors are primarily mathematical problems with the 3D mesh from which objects are made. These objects are often non-manifold. “Non-manifold” refers to a geometry that cannot exist as a physical object in the real world.

You can have the integrated object viewer analyze these errors. See Use the object viewer.

Error	Description	Targeted value
Degenerated triangles	Degenerated triangles have an area of almost 0. They can slow down CAM calculations or lead to calculation errors. They are often caused by export errors.	0
Double triangles	In this case, multiple identical triangles lie exactly on top of one another. Duplicate triangles increase the file size and can lead to surface issues.	0
More than 1 geometric shape	The object must consist of 1 continuous geometric shape. Use exactly 1 file for each specimen.	1
No closed/watertight 3D mesh	The object’s 3D mesh must form a completely closed volumetric solid. There may be no holes or open areas.	Sealed/waterproof
Non-manifold corner points	A corner point is non-manifold if the surfaces cannot be arranged seamlessly and clearly around that point. Non-manifold corner points can cause problems when calculating tool paths.	0
Non-manifold edges	A non-manifold edge is shared by more than two triangles at the same time	0
Open edges	Open edges occur where a triangle has no directly adjacent face. They often indicate holes or open areas.	0
Orientational conflicts	The triangles do not have a uniform area standard The normal is a vector that is perpendicular to the surface of an object. As a result, programs cannot clearly distinguish between what is inside and what is outside.	0

Preparation margin too thin

If the preparation margin of the object is too thin, parts of the object may break off.

Incorrect preparation margin

If the preparation margin of the object contains errors, the manufacturing results will be unusable.

Surface too rough

If the surface of your object is too rough, problems with fittings may occur.

Resolution too low or too high

Models in STL files are made of triangles. The higher the resolution of the STL files, the more triangles are used and the smaller the triangles become. More triangles mean more surface details, but also larger files.

If the resolution of the STL file is too low, triangles will become too big and there will not be enough surface details for proper manufacturing.

If the resolution of the STL file is too high, the file size will be too large. This results in long loading and processing times. These STL files will contain more surface details than your machine can manufacture.

Appropriate file sizes of common indications

Indication	Typical number of triangles	Typical STL file size
Abutment	50,000	3 MB
Bite splint	280,000	15 MB
Bridge	110,000 550,000	5 MB (5 units) 25 MB (14 units)
Coping	100,000	6 MB
Single crown (fully anatomical)	50,000	3 MB
Implant bar	15,000	6 MB
Inlay	80,000	4 MB
Clamp prosthesis	75,000	4 MB
Implant bridge with a gingival portion	100,000	7 MB (14 units)
Telescopic crown	25,000	2 MB
Veneer	25,000	2 MB

Interdental errors

If there are incorrect surfaces between teeth, the manufacturing result will become unusable.

Acute angles

Acute angles lead to the material thickness becoming infinitely small at the tip.

What's next?

If you want to import objects directly

Importing objects

If you want to check an object for errors first:

Use the object viewer