As the representative of advanced productive forces in the machinery manufacturing industry, CNC machining has played an important role in the automotive, aviation, aerospace and mold industries after more than 10 years of introduction and development.
CNC programming is an important aspect affecting the quality and efficiency of CNC machining, especially in high-speed and precision machining. In the mechanical industry, because the level of CNC programmers is different, it is necessary to establish certain specifications to avoid low-level errors and repetitive problems.
First, numerical control machining programming flow.
The general process of NC machining programming includes: determining the basis of programming, establishing process model, defining machining operation, generating tool path, machining path simulation, post-processing, NC machining program simulation, NC machining program checking, issuing on-site processing and NC machining program finalization.
1. confirm programming basis.
CNC programming basis mainly includes three-dimensional model, engineering drawings and parts manufacturing instructions (NC process specification), through NC programming basis can be obtained the following information: parts information, NC machining process plan, NC machine tool type, clamping positioning mode, cutting tools, procedures and steps, processing program number and product processing status. Wait.
2. establish process models
Based on the three-dimensional model of parts and engineering drawings, the process model is designed, which mainly includes trimming of the three-dimensional model of parts, establishing process reference surface, establishing process positioning hole, pressing plate and position design, and machining surface allowance processing.
3. define machining operations to generate tool path.
Define the machining operation and generate the tool path. The main contents include: Define the programming coordinate system, fully consider the machining material characteristics, tool cutting characteristics, machine tool cutting characteristics and the material conditions of the parts to be removed, define the machining methods (including various tool running strategies, etc.) and process parameters (including remainder) according to the process requirements. Quantity, feed speed, spindle speed, tool path span, etc. and auxiliary attributes (including tool point, safety surface and CNC machine tool attributes) eventually generate tool path.
4. machining trajectory simulation verification
The main contents of simulation verification of machining path include: checking whether the definitions of cutting tools, machine tools, workpieces and fixtures are complete and the dimensions are accurate; checking machining operations, defining whether the dimensions of the parts to be achieved in each process are correct; checking the machining methods in the definition of machining operations (such as rough machining strategy, tool repair machining and cavity machining). Etc.
Whether it is correct and reasonable; Check whether there are over-cutting, undercutting or collision interference between NC machine tool worktable, machined parts, tools and fixtures; Check whether the process parameters are reasonable.
5. post processing
Postprocessing can be an independent processing process, or can be integrated with the tool location file generation process, according to the function of the processing software, choose the appropriate processing method, and for the post-processing there are the following requirements:
The special post-processing software should be selected to generate the special NC system processing program; the development or customization of the post-processing software should be combined with the specific control system and the type of machine tool motion structure; the post-processing software should ensure the full conversion of tool position processing information and meet the requirements of control system syntax; the post-processing software should be used to develop or customize the post-processing software. When necessary, the necessary annotation instructions are automatically added to the processing program.
6. simulation verification of NC machining process
On the basis of programming software or combining with the function of NC simulation software, verify every aspect of CNC machining program as far as possible to ensure the correctness of the final machining program, and record the corresponding simulation verification of CNC machining program.
The simulation verification mainly includes the following contents: checking whether the annotation information is correct in the machining procedure; checking whether the machining method is correct in the NC machining procedure; checking whether the tool size information is correct in the machining procedure; checking whether the part size information that each working procedure should achieve is correct in the CNC machining procedure; Check whether the tool compensation information is correct in NC machining program, check whether there are over-cutting, under-cutting or collision interference problems in CNC machining program, check whether the spindle speed and feed speed matches the current NC machine tool, etc.
7. proofreading of CNC machining program
The proofreading of NC program is totally different from the proofreading of process files. The program format is a coordinate point. If we proofread the program content line by line, it will take a lot of time and is impractical.
The proofreading procedure is mainly considered from the following aspects.
(1) model. Model is the basic element to ensure the correctness of the program. It is necessary to check the correctness of the model and analyze whether all the data of the model are consistent with the elements of process documents.
Coordinate system. Check whether the direction of the machining coordinate system is in accordance with the requirements of the process documents, whether it is easy to operate, whether the selection of the coordinate system is reasonable and whether it is easy to control the size.
Third, the processing strategy. The program generated by different machining strategies is totally different, and the amount of program is also different. The rationality of the analysis of machining strategy is mainly to control the tool path of the program, control the machining quality and efficiency.
(4) cutting tools. Tool materials, specifications and forms are determined according to part materials and parts processing position. Different tools directly affect the processing efficiency and quality.
About the author