During the processing of parts, due to the impact of various factors, the parts that are completed by the final processing usually cannot completely conform to the ideal state. Therefore, the concept of processing accuracy has occurred to represent the fineness of the processing of the parts.
This article will take you to understand the concept of processing accuracy and
What is the processing accuracy?
Simply put, the processing accuracy is the degree of compliance with the actual geometric parameters and ideal geometric parameters after the completion of the parts processing. The higher the degree, the higher the processing accuracy.
This processing accuracy contains three aspects: size accuracy, shape accuracy and position accuracy.
There are connections between the three. Generally, the shape tolerance should be limited to the position tolerance, and the position error should generally be limited to the size tolerance. When the size and accuracy requirements are high, the corresponding position accuracy and shape accuracy also require high. However, when the shape accuracy is high, the corresponding position accuracy and size accuracy sometimes do not necessarily require high, which should be determined according to the functional requirements of the part.
Because the mechanical processing is performed in the process system, the obtained by the size, geometry, and the relative positions between the surface depends on the relative position and mutual movement of the workpiece and tools in the cutting movement. The accuracy of the relative position between the surface depends on the precision of the process system of machine tools, fixtures, tools and workpieces.
The various errors in the process system are reflected in the processing error in different degrees and methods. The error of the process system is “cause”, the root cause, the processing error is “fruit”, and it is a manifestation. Therefore, the error of the process system is called the original error. The primitive errors will change the relative position or interrelationship relationship of the workpiece and tools, resulting in processing errors. For example, the following factors may affect the processing accuracy:
1) Plip: The piston is based on the stop and its end surface as the positioning benchmark, locate in the fixture, and insert it into the semi -sperm -based sales holes in the semi -sophisticated sales. The clamping force of the fixed piston acts on the top of the piston. Because the design benchmark (top surface) does not coincide with the positioning benchmark (stop end surface), and the position of positioning stop and fixture upper convex, diamond -shaped sales and sales holes will cause positioning errors. error. These two original errors are collectively referred to as workpiece clamp errors.
2) Adjustment: Before and after the installation of the workers, the machine tools, tools and fixtures must be adjusted, and after several workpieces, accurate fine -tuning must be performed to keep the workpiece and tools correct the relative position. Sometimes the position adjustment of the fixture on the workbench, the adjustment of the diamond -shaped sales and the spindle coaxiality, and the adjustment of the knife. Because adjustments cannot be absolutely accurate, adjustment errors will occur. In addition, the manufacturing errors of machine tools, tools, and fixtures itself exist before processing. This kind of original error is called the geometric errors of the process system. It should be noted that even if there is a fixture, a certain position adjustment should be performed before processing, so as to keep the processed workpiece and the processing knife be maintained correctly.
3) Processing: Due to the cutting force, cutting heat and friction during processing, they will cause the force deformation, heating deformation and wear of the process system, which affects the relative position between the workpiece and the tool, and causes processing errors. The original error caused by this type of processing during processing is called the movement error of the process system.
4) Measurement: During the processing process, the workpiece must also be measured. Any measurement method and measuring tool or measuring instrument cannot be absolutely accurate. The error caused by it is called the measurement error.
During the cutting process, the size and direction of various original errors are different, and the processing error is measured in the process size direction. Therefore, different original errors have different effects on processing accuracy. When the direction of the original error is consistent with the process size direction, its impact on the processing accuracy is the greatest.
Hope the above content is helpful to you.
