CNC programming main working program

Using CNC machined parts, the most important job is to compile NC machining programs for the parts. The numerical control programming process can be attributed to several basic steps such as the understanding of the process plan, workpiece clamping, establishing the coordinate system, inputting the tool parameters, inputting the numerical control program, verifying the program, adjusting and operating the machine tool.

The numerical control process scheme is the soul of processing. For the general workpiece, the focus of the process scheme is to improve the efficiency and reduce the cost. For critical parts, important parts, and complex parts, the process plan directly relates to the processing quality of the parts. The programmer should make more efforts on the process plan, sum up experiences, and start from every detail with practicality and earnestness. After clear objectives, process analysis is performed to determine the corresponding processes and steps, as well as process assurance measures for key parts. At the same time, the skill level of the operator, the configuration of the existing process equipment, tools, gages, and equipment should be considered. factor.

The main contents of CNC programming are as follows:

1. Parts NC machining process analysis

Based on the design drawings of the machined parts and related technical documents, the materials, rough types, shapes, dimensions, precision, surface quality, and heat treatment requirements of the parts are comprehensively analyzed.

The part design map defines the geometry and structural features of the part, its dimensions and tolerances, form and position tolerances, technical requirements, materials, and heat treatment requirements. In the numerical control programming of parts, it is also necessary to understand the state of the wool parts, including the type, specification, shape, heat treatment state, and hardness of the wool. These two parts constitute the main contents of the numerical analysis of the processed parts, and also determine what is The technical key of the part, the difficult point in the processing, the difficulty of the numerical control programming.

On the basis of using all the above original information, comprehensively consider other relevant factors to determine a reasonable numerical control machining program and numerical control processing method. Initially establish positioning and clamping benchmarks, reasonably select machine tools, determine machining tools and cutting amount, etc.

2. Numerical Control Machine Tool and Its Control System Performance Analysis

The performance analysis of CNC machine tools includes the processing range of the table, the spindle speed range of the machine tool, the power of the machine tool, the type and specification of the tool holder used in the machine tool, the composition of the tool system, the connection of the fixture and the machine tool, and the input method of the NC program.

The first consideration is whether the work area or workspace of the CNC machine tool can meet the requirements of the CNC machining of the part. The part must be installed in the fixture, so the CNC machine tool should be large enough. The total weight of parts and fixtures should not exceed the machine's specifications.

Secondly, we should also grasp and understand the contents of the rated power of CNC machine tools, the scope of spindle speed and feed speed, the number of tool positions, the tool system, and other accessories of the machine tool. Usually a small CNC machine has a higher spindle speed and a lower rated power, while a large machine has a lower spindle speed and a higher rated power.

3. Numerical control system performance analysis

The performance analysis of the CNC system includes the type of control system, the definition of the coordinate system, the definition of the spindle speed range, the feed rate, the tool identification and numbering method, the requirements for circular interpolation, the linkage of axes, and the corner control method. , Tool movement (fast motion, linear motion and arc motion) modes and other aspects; also includes the format of numerical control program, the grammar structure of numerical control program, common numerical control programming instructions and their usage rules.

The control system is the core part of the CNC machine tool. When programming the NC program, the programmer must have a clear understanding of the standard instructions of the control system. Only in this way can the unique functions and scientific programming methods of the CNC system be used, such as the machining cycle. , subroutines, macros, and other features.

It is recommended that programmers have a good understanding of CNC machine tools and numerical control systems. This is useful for writing high-quality, high-quality NC programs and is more innovative. The effective use of CNC system functions and the quality of NC programs reflect the programmer's understanding of the functions of CNC machine tools and their numerical control systems.

One important reason is that programmers are involved in the numerical control programming of parts. Of course, they also include subsequent numerical control programming, which increases the programmer's personal experience and expertise.

4. Parts NC programming data processing

Because the part design diagram mainly reflects the designing idea of ​​the designer, more considerations are taken in the aspects of the shape characteristics, size, and the mutual positional relationship between the parts. In terms of part structure, processability, etc., little or no consideration is given to the influence of processing. This includes the following:

(1) The design datum transformation data processing is represented by the design datum on the parts drawing. It is composed of points, lines, and faces that reflect the characteristics of the design idea. It is also the basis for establishing the part coordinate system. The establishment process of the machining coordinate system is the design. The process of linking the datum and the part coordinate system. The processing coordinate system is used as a reference for machining. First, consider whether the design reference is suitable for establishing the machining coordinate system of the part, that is, whether it can be established according to the design basis; if not, how to convert it; and secondly, consider the processing coordinate system determined by the design reference. Whether the location is easy to correct; the third is to consider whether the origin of the coordinate system is simple for numerical control programming.

(2) The part processing graphics processing mainly considers the numerical control processing technology of the parts, and performs the necessary mathematical processing and numerical calculation on the part graphics. This can be summarized as follows: Simplified part drawing Extraction of curves and surfaces (characteristics) in part design drawings as NC machining drawings; or compression of certain manufacturing-independent features, such as features that do not require machining or machining (such as holes, Slots, fillets, threads, etc.). After these features are compressed, they can obviously feel intuitive programming, increase the speed of operation and make the tool path trajectory reasonable. Completing part drawings Rebuild or supplement the graphics that meet the requirements based on the requirements of the part's CNC machining. Add some processing auxiliary lines or auxiliary surfaces to build tool trajectory limit boundaries.

(3) The calculation of the base point, node and tool location shows that the contour curve of the part consists of different geometric elements such as straight line, circular arc, and quadratic curve. Before the program is compiled, some coordinate values ​​of the machining trajectory must be calculated. Input data for the program tool location. Data calculations include base point calculations, node calculations, and so on. For complex machining curves and surfaces, computer-aided calculations must be used.

5. CNC routing design

The numerical control process line design is a programming process for the programmer in combination with the specific conditions of the machine tool, considering the positioning of the workpiece, designing the fixture or selecting the fixture, and assisting the tooling and designing the NC machining program.

First determine the final part of the NC machining graphics or models; then determine the parts of the processing coordinate system, in order to reduce the positioning error, the processing coordinate system should be consistent with the design basis; Finally, the NC machining program design, including processing area division, processing route determination and Process design and other aspects.

6. Write NC machining program

According to the determined processing route, tool number, cutting amount, auxiliary actions, and numerical calculation results, the machining program is written paragraph by paragraph according to the use function instruction code and the segment format of the CNC machine tool. In addition, necessary machining schematics, tool layout drawings, machine adjustment cards, process cards, and necessary instructions should also be attached.

The process of numerical control programming is a process of gradually improving the numerical control process plan. Since the technological scheme is pre-imagined, it is not necessarily comprehensive. Therefore, it is necessary to constantly adjust and improve the numerical control programming.

7. NC program verification

The validation of NC programs is an indispensable part. You can't give up verification because of the time or ideological luck. The main contents of program verification include:

● Whether there is a syntax error in the NC program, and whether the input data is valid, that is, whether the CNC system can recognize it.
● The NC program is complete and reasonable.
● The tool movement path is correct.

The programmed NC program can usually verify the correctness of the program by displaying the tool path, ie, the tool's movement path, on the machine tool display.

The contents of the check section of the first trial cutting program can only prove the correctness of the movement of the tool path. Therefore, the first test of the workpiece should be performed to check the following aspects:

● If there is any interference between the tool, holder, fixture, and the machine, collision can occur.
● Whether the tool is reasonable, whether it can meet the processing requirements and whether there is overcutting.
● Whether the cutting amount is reasonable or not, whether the given values ​​such as spindle speed, feed speed, and cutting depth in the program can meet the processing requirements.

According to the actual verification of the content such as interference, over-cutting area, the rigidity and elastic deformation of the tool, workpiece and fixture, as well as the tool wear and other factors necessary for processing and adjustment. For the machining error, the cause of the machining error should be analyzed and corrected so that the accuracy of the part and the quality of the machining can be achieved.

8. CNC file curing

After completing the above work, all CNC process files must be perfected, cured and archived. The following lists the common CNC process documents, which can be improved and increased or decreased according to specific conditions.

● NC program list.
● NC program text can also be storage media.
● Machining path map.
● CNC step card.
● CNC process specification or operation chart.
● Operating instructions.
● Tooling list.
● Tool list.
● Blank map.
● Parts positioning and clamping diagrams, operating instructions.

CNC debugging and processing considerations.

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