Wanhao manufacturer explains CNC machining accuracy in detail

CNC machining is a highly efficient and precise processing technology widely used in modern manufacturing. Machining accuracy is one of the important indicators for evaluating the quality of CNC machining, directly affecting the performance and lifespan of the final product. This article will conduct a detailed discussion from two aspects: the definition of CNC machining accuracy and the influencing factors.

1. What is CNC machining accuracy

CNC machining accuracy refers to the degree of conformity between the actual size, shape, position, etc. of the machined parts and the design requirements. It mainly includes dimensional accuracy, shape accuracy and position accuracy

Dimensional accuracy refers to the deviation between the actual size of the processed part and the designed size. The Tolerance zone is often used to represent it. The smaller the tolerance zone, the higher the dimensional accuracy.

2. Shape accuracy refers to the deviation between the actual shape of the processed part and the designed shape, including roundness, flatness, straightness, etc. The smaller the shape error, the higher the shape accuracy.

3. Positional accuracy refers to the deviation between the actual position of the processed part and the designed position, including coaxiality, symmetry, parallelism, etc. The smaller the positional error, the higher the positional accuracy.

What are the key factors that affect the accuracy of CNC machining?

In the actual CNC machining process, the machining accuracy is often influenced by the combined effect of multiple factors, which are interrelated and directly determine the final quality of the workpiece. Based on production practice, the main influencing factors can be summarized into the following categories:

The precision and performance of the machine tool itself

Machine tools are the core equipment for CNC machining, and their own quality directly lays the foundation for precision. On the one hand, the core manufacturing precision of machine tools (such as the guiding accuracy of guide rails and the rotational accuracy of spindles) is an inherent condition. On the other hand, the rigidity of the machine body structure is also of vital importance - high-rigidity machine tools can effectively resist the impact force and vibration generated during the cutting process, avoiding processing deviations caused by machine body deformation. Especially for machine tools that have been in use for a long time, problems such as guide rail wear and spindle clearance will gradually affect the stability of precision.

2. Precision and wear control of cutting tools

As the actuating component that directly contacts the workpiece, the precision state of the cutting tool has a significant impact on the processing result. The geometric accuracy of the cutting edge, the sharpness of the cutting edge and the uniformity of the tool material of the new cutting tool will all be directly reflected in the size and surface quality of the workpiece. During the processing, the wear of cutting tools is inevitable. The blunting and chipping of the cutting edge after continuous cutting will lead to an increase in cutting force, a deviation in the cutting path, and subsequently dimensional errors. Therefore, regularly inspecting the wear of cutting tools and replacing them in a timely manner is an important link to ensure accuracy.

3. Positioning and clamping effect of the fixture

The function of a fixture is to stably fix the workpiece. Its positioning accuracy and clamping reliability directly affect the processing reference of the workpiece. If there are errors in the positioning surface of the fixture or the positioning pins are worn, it will cause the installation reference of the workpiece to shift. Excessive clamping force can easily cause deformation of the workpiece, while insufficient clamping force may lead to loosening of the workpiece during the cutting process. All these problems will directly translate into machining accuracy errors.

4. Reasonable matching of processing parameters

The setting of core processing parameters such as cutting speed, feed rate and cutting depth is closely related to precision control. For instance, excessively high cutting speed can easily cause severe wear of the cutting tool and thermal deformation of the workpiece, while too low speed may lead to an increase in cutting force and cause vibration. Although an excessive feed rate can enhance efficiency, it will reduce surface accuracy. On the other hand, a too small feed rate may lead to the "tool biting" phenomenon. Only by precisely matching parameters based on the material of the workpiece, the type of tool, and the requirements of the processing technology can errors be controlled while ensuring efficiency.

5. Stability of the processing environment

The fluctuations in temperature and humidity in the processing environment are often overlooked factors affecting precision. The materials of the machine tool bed, guide rails and workpieces are different, and the coefficients of thermal expansion also vary. Changes in environmental temperature can cause uneven deformation of each component, thereby destroying the original precision matching. For instance, the increase in workshop temperature in summer may cause the machine tool guide rails to elongate, while in winter, they may contract. Therefore, maintaining a constant temperature and humidity environment in the processing workshop and properly compensating the temperature of the machine tool and the workpiece can minimize the precision error caused by thermal deformation to the greatest extent.