Several important experiences and techniques of CNC Steel Parts

CNC steel parts machining is a precision manufacturing process carried out through numerical control machining tools. By means of precise control through computer programming, CNC machining demonstrates outstanding processing quality, high precision, high repeatability, and excellent processing capabilities for complex surfaces, while also significantly enhancing processing efficiency. However, in actual operation, human factors and rich operational experience have a profound impact on the quality of the final product. Next, we will share twelve crucial experiences in CNC steel parts processing.

★In the process of CNC steel parts processing, the division of procedures is of vital importance. Reasonable process division can ensure the efficiency of processing and product quality. So, how can the CNC processing procedures be scientifically and reasonably divided?

The division of processing procedures for CNC steel parts can follow the following several methods:

Tool concentration sorting method. This method divides the process according to the tools used, that is, first use one tool to complete all the achievable parts on the part, and then switch to the second and third tools to complete the other parts. This can reduce the frequency of tool changes, shorten the idle travel time and lower the positioning error.

★Sorting method of processing parts. For parts with numerous processing contents, the processing sections can be classified into internal shapes, external shapes, curved surfaces or planes, etc., according to their structural characteristics. Usually, planes and positioning planes are machined first, and then holes are machined. Process simple geometric shapes first, and then complex geometric shapes; Process the parts with lower precision first, and then the parts with higher precision.

★The sequential method for rough and finish CNC machining. For parts that are prone to processing deformation, since they may deform after rough machining and need to be straightened, rough and finish machining should be separated.

When dividing processes, it is necessary to comprehensively consider the part structure, processability, machine tool functions, numerical control processing capacity, installation frequency and production organization status, and flexibly apply the principle of concentration and dispersion. Meanwhile, the arrangement of the processing sequence should ensure that the rigidity of the cnc steel parts is not damaged. The sequence generally follows the structure of the parts, the condition of the blank, and the positioning and clamping requirements.

►1. Ensure that the CNC machining of the previous process does not interfere with the positioning and clamping of the next process, especially when interspersed with general-purpose machine tool machining processes in the middle, a comprehensive consideration is required.

►2. Follow the sequence of processing the inner shape and cavity first and then the outer shape.

►3. Try to continuously arrange CNC machining processes that use the same positioning and clamping methods or the same tool to reduce unnecessary repetitive positioning, tool changing and the frequency of moving the pressure plate.

►4. For multiple processes completed in the same installation, the one that causes less rigidity damage to the cnc steel parts should be arranged first.

Next, we will discuss several aspects that should be noted when determining the workpiece clamping method: When selecting the positioning reference and clamping scheme, the following three points need to be paid attention to.

►1. Ensure that the benchmarks adopted in the design, process flow and programming calculation remain consistent.

►2. Minimize the number of clamping operations as much as possible and strive to complete all the surfaces to be processed through CNC machining after a single positioning.

►3. The scheme of manual adjustment on machine tools should be avoided.

►4. The design of the fixture should be unobstructed, and its positioning and clamping mechanisms should not impede the tool movement during CNC steel part processing (such as in case of collision). If such a situation occurs, you can consider using pliers or adding a base plate and using screws for clamping.

Next, we will explore how to reasonably determine the tool setting point and understand the relationship between the workpiece coordinate system and the programming coordinate system.

■The tool setting point can usually be set on the workpiece to be machined, but it is necessary to ensure that this point is a reference position or a part that has already undergone fine machining. Sometimes, after the first process, the tool setting point may be damaged due to CNC machining, making it impossible to find the tool setting point in subsequent processes. Therefore, when performing tool setting in the first process, it is recommended to set up a temporary tool setting position at a place that maintains a relatively fixed dimensional relationship with the positioning reference. In this way, even if the original tool setting point is destroyed, it can be retrieved based on these relative positional relationships. This temporary tool setting position is often located on the machine tool worktable or fixture. Its selection should follow the following principles:

1) It is easy to align.

2) Simple programming.

3) The tool setting error is very small.

4) The inspection during the processing is convenient and traceable.

■. The origin position of the CNC steel part coordinate system is set by the operator through precise tool setting after the workpiece is clamped. This origin reflects the distance relationship between the workpiece and the zero point of the machine tool. Once the workpiece coordinate system is determined, it is usually not changed easily. Meanwhile, to ensure the accuracy of processing, the coordinate system of the steel part must be consistent with the programming coordinate system.

The tool path refers to the movement trajectory and direction of the tool relative to the workpiece during numerical control machining. A reasonable tool path is crucial to the machining accuracy and surface quality of cnc steel parts. When determining the cutting route, we mainly consider the following aspects:

1. Foremost ensure that the machining accuracy of CNC steel parts meets the predetermined requirements.

2. It is convenient for numerical calculation, thereby reducing the workload of programming.

3. Strive to find the shortest cnc machining route to reduce idle tool time and thereby enhance the efficiency of cnc machining.

4. Minimize the number of program segments as much as possible to make it more concise.

5. Ensure that the roughness of the workpiece contour after cnc machining meets the standard. Usually, the processing of the final contour is arranged to be completed continuously in the last pass.

6. Carefully consider the tool's entry and exit routes (entry and exit) to minimize the tool marks left by stopping at the contour (elastic deformation caused by sudden changes in cutting force), and also avoid scratching the workpiece by vertically lowering the tool on the contour surface.

After the alignment of the cnc steel parts and the program debugging are completed, the automatic processing stage can be entered. During this process, the operator needs to monitor the cutting situation in real time to prevent abnormal cutting, thereby ensuring the quality of the workpiece and avoiding other accidents. When monitoring the cutting process, the following aspects mainly need to be focused on:

1. Processing procedure monitoring

During the rough machining stage, the main objective is to quickly remove the excess allowance on the surface of the cnc steel parts. The machine tool will perform automatic cutting according to the preset cutting parameters and trajectory. At this point, the operator should closely monitor the changes in the cutting load and monitor it in real time through the cutting load meter. According to the load-bearing capacity of the cutting tool, adjust the cutting parameters in a timely manner to fully utilize the processing capacity of the machine tool.

2. Cutting sound monitoring

During the automatic cutting process, the sound of the cutting tool cutting the workpiece is an important basis for judging the cutting state. A stable cutting sound indicates that the machine tool is moving smoothly, while changes in the sound may suggest instability in the cutting process, such as hard spots on the workpiece, tool wear or clamping issues. Once abnormal cutting sounds are detected, the cutting parameters and conditions should be adjusted immediately. If necessary, the machine should be stopped to check the status of the cutting tools and cnc steel parts.

3. Monitoring of the finishing process

The finishing stage aims to ensure the dimensional accuracy and surface quality of cnc steel parts. Due to the relatively large cutting speed and feed rate, special attention needs to be paid to the influence of built-up edge on the machined surface. In addition, the problems of overcutting and tool deflection at corners during cavity processing should not be ignored. To ensure processing quality, it is necessary to adjust the spray position of the cutting fluid, observe the quality changes of the machined surface at the same time, and adjust the cutting parameters in a timely manner. If the problem persists, the machine should be shut down to check whether the original program is reasonable.

4. Tool monitoring

The quality of cutting tools is of vital importance to the processing quality of cnc steel parts. During the automatic processing, the status of the cutting tool should be continuously monitored through methods such as sound control, time control, pause inspection and surface analysis. Once abnormal wear or damage of the cutting tool is detected, it should be dealt with immediately to prevent adverse effects on the processing quality.

When choosing processing tools, multiple factors such as the material of the tool, rotational speed, cutting speed and cutting width need to be considered. Cutting tools made of different materials have different application scopes and performance characteristics, so it is necessary to make a reasonable selection based on specific processing requirements. At the same time, when determining the cutting parameters, multiple factors such as the characteristics of the cutting tool, the material of the steel part and the processing requirements also need to be comprehensively considered to ensure the stability and efficiency of the processing process.

★. When performing plane milling, it is recommended to use non-reground carbide end mills or end mills. In conventional milling operations, it is recommended to adopt two tool passes. For the first pass, end mills should be used for rough milling, and it is advisable to ensure continuous tool passes along the workpiece surface. The width of each tool pass should be controlled between 60% and 75% of the tool diameter.

★. End mills and end mills with carbide inserts are ideal choices for machining bosses, grooves and box mouth surfaces.

★. For the processing of curved surfaces and variable-angle contour shapes, ball cutters and round cutters (also known as round-nose cutters) are often used. Among them, ball cutters are mostly used for semi-finishing and finishing, while round cutters inlaid with hard alloy tools are often used for rough machining.

The processing program sheet plays a crucial role in the mechanical processing. It records in detail all the parameters and steps during the processing, and serves as an important basis for the operator to monitor and adjust the processing. In the processing program sheet, information about the workpiece, tool selection, cutting parameters, processing steps and precautions should be included to ensure the smooth progress of the processing and the compliance of workpiece quality.

★. The processing program sheet plays a crucial role in numerical control processing. It is not only an important component of the design of numerical control processing technology, but also a regulation that operators must abide by and implement. This document, which specifically describes the processing procedure, aims to enable the operator to have a clear understanding of key information such as the program content, clamping and positioning methods, selected tools, and precautions at a glance.

★. The processing program sheet should contain rich information, including the names of the drawing and programming files, workpiece names, clamping sketches, program names, the tools selected for each step of the program, the maximum cutting depth, the processing nature (such as rough machining or finish machining), and the theoretical processing time, etc. This information is crucial for ensuring the smooth progress of the processing procedure and meeting the quality standards of cnc steel parts.

Before determining the processing technology and preparing for numerical control programming, we must fully consider the following factors:

1. The clamping method of the workpiece will directly affect the stability and accuracy of CNC steel part processing.

2. The size of the workpiece blank determines the processing range and whether multiple clamping is required.

3. The material properties of the workpiece determine which cutting tool to use for processing.

4. Check the status of the inventory of cutting tools to avoid being forced to modify the program due to the lack of necessary tools during the processing. If specific tools are indeed needed, they can be prepared in advance.

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