When we talk about 3D printing, the Standard Tessellation Language (STL) file format comes into picture. Any type of 3D CAD file needs to be exported into a *.stl file format, which can be easily done in any CAD software. These digital models created in the Computer Aided Design (CAD) software illustrate huge number of triangles which fit together to form the desired geometrical shape. This not only gives you an overall idea and view of the type of model and its desired shape, but also helps you understand the technicality of the same, thus enabling you to detect the errors in it.
Let us understand what does one mean by an *.stl file. Basically, an *.stl file is the one which stores information related 3D models. *.stl is actually a file extension used for STL files. In this format, the surface geometry of a 3D shape is the only attribute displayed to you, and not the color, or texture, or similar CAD model features. This file format ciphers the 3D object’s surface geometry using a concept called Tessellation. In this method, the 3D models are converted into various small triangles.
Although this is quite fascinating and easier to work upon once you learn the basics, there are higher chances of common mesh errors occurring in your 3D file. Let me first explain to you how to identify the errors that are likely to be found in your mesh. Once your digital models are generated, the software intimates your 3D printer few instructions to create the shape, which may be in the form of *.gcode file, which is very common, or in the form of *.x3g binary files. Once you find out that the preview is quite different from the model that you created, invariably, it’s a cue for you that the reason is part meshing.
Some of the common Mesh errors that occur in 3D CAD files are as follows:
Suppose, you have an *.stl file and if few edges of this model do not connect to only one face, then the boundary edges are detected. If there is no connection between the edges and the face, the whole shape no more represents an enclosed surface, thus indicating the presence of holes in the structure. Although modernized softwares today are able to process *.stl files even if the file has open boundaries, there is no assurance of the output to be similar to the actual design. For fixing these boundary edges, modifications in the CAD or the *.stl file is suggested.
Non-manifold edges are found either in the form of an extra surface which divides the interior of the shape into two or in the form of a common edge shared by two or more bodies. The fact that this error of non-manifold edges doesn’t create any problem during slicing cannot be completely ignored. This is due to the fact that the concept utilized towards making of original design might differ from the actual result. Say, if two squares share a common edge, there might be confusion created regarding the final outcome, in the sense that the designer may want two pieces to be merged into a single one or to be printed as two separate objects. Adding some extra space(gap) or thickness to the 3D model, especially in the thin sections increases the clearance, which eliminates the scope of an error occurring.
Once two solid surfaces of the *.stl file clash with each other, error occurs in the form of intersecting faces. This situation arises when more than one body constitutes the same space. Intersecting faces generate failures during slicing process because, during this situation, the software cannot differentiate between the areas which are inside or outside the model. Modern 3D Printing softwares are available which can fix these errors, but the desired success is not usually achieved. Practicing good design, and timely checking the work being done, will not only create an efficient model but also help you save time and effort effectively. One can either do modifications in the original CAD model by integrating the single parts into a solid part or go for STL repair after the file is exported to *.stl file format.