The reasons why STL files are not suitable for CNC machining:
Differences in Geometric Representation
STL files: Represent 3D models using a mesh of triangles, where each surface is approximated by numerous small triangles connected together. This approach works well for 3D printing, as 3D printers build objects layer by layer, with each layer being represented by a series of triangles.
CNC machining: Requires precise geometric descriptions. The CNC machine needs to know the exact position of every surface, line, and boundary to generate accurate cutting paths. These paths are created by CAM (Computer-Aided Manufacturing) software, which relies on detailed geometric data—not the triangulated mesh used in STL files.
Geometric Accuracy Issues
STL files: Since the model is represented by triangles, the accuracy of geometric features is limited. For instance, a perfect circle becomes a polygon made up of many straight line segments in an STL file. This approximation compromises the precision of the surface and fails to meet the high accuracy standards required for CNC machining.
CNC machining: Requires highly accurate geometric data. CNC machines produce parts with very precise shapes and dimensions, often measured in microns. If the geometric data is not sufficiently precise, the finished part may not conform to the intended design specifications.
Data Redundancy and Processing Complexity
STL files: Typically contain a large number of unnecessary triangles, which increase both the file size and processing time. For complex models, an STL file may contain millions of triangles, making the file difficult to process efficiently.
CNC machining: Requires optimized and simplified geometric data. To generate efficient machining paths, CAM software needs geometric information that is as concise and accurate as possible. Redundant triangles not only increase processing time but can also result in inaccurate cutting paths, which negatively impacts machining efficiency and quality.
Lack of Advanced Geometric Features
STL files: Cannot represent advanced geometric features, such as precise surfaces, complex boundaries, and topological relationships. This critical information is lost in the triangular mesh, making STL files unsuitable for CNC machining applications.
CNC machining: Requires detailed geometric and topological information. Formats like STEP files can contain precise descriptions of geometry, complex surfaces, and boundary conditions, which are essential for generating accurate machining paths and ensuring high-quality results.
