Once you’ve finished designing your CAD model you are almost ready for printing. We’ve compiled a guide for preparing files for 3d printing to make sure you have what you need to get your perfect print. This article gives a few hints and tips on how to make sure you get the 3D print you want.

#1   Watertight Mesh

In order to print well, your 3D model will need to be a solid, waterproof mesh. Meshes that do not form a closed volume or object will not print properly. Models with intersecting faces are also likely to cause issues.

Picture showing a mesh with a missing face. i.e not watertight.

There are several key reasons as to why you might be generating non-manifold geometry and repairing it is dependent on the software you’re using. Some types of CAD software have built-in functions that can check for non-manifold geometry and advise on how to fix it. In general, if you design the model to be printed you are probably going to avoid the impossible geometry in the first place. A few common reasons for why a model might have non-manifold geometry:

  • The volume has zero thickness which cannot be recognised, it would be invisible in real life.
  • Mesh is not watertight. i.e it has one or more faces missing.
  • The volume has one or more intersecting faces. This makes it difficult for a computer to interpret the boundaries of your model.

If you’re still unsure whether your model is waterproof, you can upload it for a quote online or send it over via email and we’ll let you know if we encounter any issues. If we come across any minor meshing problems, we’ll usually fix them free-of-charge.

#2   Your mesh is fine enough

Exporting a file to a mesh (STL format) is all about finding a balance between achieving enough resolution and not making the file too large.

There are two main parameters that you can vary to change this: the maximum chord height and the tolerance angle of the file. The maximum chord height is the greatest distance from the surface of the STL to the surface of the original model. The smaller this value is, the more complexity you add to the model. A general rule of thumb for the chord height is to make it 1/20th of the minimum layer thickness, this will ensure you never lose any detail during the conversion. The tolerance angle sets the maximum angle between the normal of adjacent triangles. You can normally see the detail in the mesh after it is exported. Below are three of the same models exported with varying mesh density.

Mesh resolution in display

If you want to maximise detail, you can increase the parameters to refine the mesh. We recommend keeping the file size below 100Mb to avoid problems uploading and sending your files. If you encounter problems uploading files, sending them via WeTransfer usually solves the issue.

3.   Your walls are thick enough

Selecting the correct wall thickness for your models will ensure they are strong enough without adding a whole lot of unnecessary material. Walls that are too thin can cause errors in the printing process. Occasionally we see walls with zero thickness, these will not show up at all in the print, so it’s important to check your model for completeness. As with all 3D prints, thinking about how the part will be made from the start is key to a successful print. If it looks like your model is missing something, it probably is.

As a rule of thumb, we recommend a minimum wall thickness of 1.2mm.

Picture showing the minimum wall thickness of 1.2mm

4.   Your small features are sized properly

We can only print features as thin as the printing nozzle. Bear this in mind when designing your parts. It is worth noting that smaller features will generally come out with a better finish on sidewalls. You might want to bear this in mind when designing parts with a logo for example; the font in your logo must not get to beneath 0.5mm.

In order for your features to show in the print, they will need to be at least 0.5mm.Nozzle and feature size


We’ve uncovered the four main points to check before uploading your file for printing. You should now have a watertight mesh, a resolution that will do your model proud, and walls and features that are sized appropriately.

  • Mesh is watertight
  • Resolution is fine enough
  • Thinnest walls are above 1.2mm.
  • Smallest features are at least 0.5mm

If you’ve managed to tick each box, your model is good for printing. Next up, we’ll look at Selecting the Right Parameters for Your 3D Prints (coming soon).