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Why the .stl file can not be used for CNC?

by: Jun 14,2024 573 Views 0 Comments Posted in CNC Machining

stl file cnc

Summary:       Due to the geometric representation, accuracy, data redundancy, and lack of advanced geometric features in STL files, they cannot be used directly for CNC machining. Even if STL files are converted to other formats such as STEP, the lack of original geometric information cannot be compensated for and therefore remains unsuitable for CNC machining. CNC machining requires the use of file formats that provide accurate geometric descriptions and detailed feature information, such as STEP or IGES, which ensures accurate machining paths and quality of machining results.

The reasons why STL files cannot be used for CNC machining are as follows:

Differences in geometric representation

  • STL files: use a mesh of triangles to represent the 3D model. Each surface is made up of many small triangles stitched together. This representation is ideal for 3D printing because 3D printers build objects layer by layer and each layer can be approximated by many small triangles.
  • CNC machining: precise geometric descriptions are required. the CNC machine needs to know the exact position of every surface, line and boundary in order to generate precise cutting paths. These paths are generated by CAM (Computer Aided Manufacturing) software based on detailed geometric information, which is not provided by the triangular mesh structure of the STL file.


Problems with geometric accuracy

  • STL files: Because the model is approximated by triangles, the accuracy of the geometric features is limited. For example, a perfect circle becomes a polygon consisting of many straight line segments in an STL file. This approximation leads to a loss of accuracy of the surface and does not meet the high accuracy requirements of CNC machining.
  • CNC machining: It requires highly accurate geometric descriptions. the results of CNC machining require very precise shapes and dimensions, often measured in microns. If the geometric information is not precise enough, the final machined part may not meet the design requirements.


Data redundancy and processing complexity

  • STL files: It usually contain a large number of unnecessary triangles, which increases the amount of data and processing time. For complex models, STL files may contain millions of triangles, which makes processing these files very difficult.
  • CNC machining: Optimized and simplified geometric information is required. In order to generate efficient machining paths, CAM software needs to process geometric information that is as concise as possible. Redundant triangles not only increase the processing complexity, but may also lead to the generation of unreasonable cutting paths, affecting the machining efficiency and quality.


Lack of advanced geometric features

  • STL files: cannot represent advanced geometric features such as precise surfaces, complex boundary conditions and topological relationships. This information is lost in the triangle mesh, making STL files unable to meet the needs of CNC machining.
  • CNC machining: requires detailed geometric and topological information. For example, the STEP file format can contain precise geometric descriptions, complex surfaces, boundary and feature information that is critical to generating accurate machining paths and ensuring machining quality.

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