• 2023-08-21
• 485
• 5 Comments

How to effectively improve the accuracy of mold processing

The extrusion die is the basis of the extrusion process, which not only determines the shape, dimensional accuracy and surface state of the extrusion product. The quality requirements are getting higher and higher, and the processing requirements for molds are also increasing. Machining accuracy is the biggest requirement of machining, so how to effectively improve the machining accuracy of the mold has become a difficult problem to solve.

1.1 Mold processing quality includes processing accuracy and surface quality
Machining accuracy is the degree of conformity between the actual size, shape and position of the surface of the machined part and the ideal geometric parameters required by the drawing. The ideal geometric parameter, for the size, is the average size; For the surface geometry, it is the absolute circle, cylinder, plane, cone and straight line. For the mutual position between surfaces, it is absolutely parallel, vertical, coaxial, symmetric, etc. The deviation between the actual geometrical parameters and the ideal geometrical parameters of the part is called the machining error.

Machining accuracy and machining error are both terms used to evaluate the geometric parameters of machined surfaces. Machining accuracy is measured by tolerance grade, the smaller the grade value, the higher the accuracy; The machining error is expressed by numerical value, and the larger the numerical value, the larger the error. High processing accuracy means small processing error, and vice versa.

The actual parameters obtained by any processing method will not be absolutely accurate, from the function of the part, as long as the processing error is within the tolerance required by the part drawing, the processing accuracy is considered to be guaranteed.

The quality of the machine depends on the machining quality of the parts and the assembly quality of the machine. The machining quality of the parts includes the machining accuracy of the parts and the surface quality of the two parts. The machining accuracy refers to the degree to which the actual geometric parameters (size, shape and position) of the parts after processing are consistent with the ideal geometric parameters. The difference between them is called machining error. The size of machining error reflects the machining precision. The larger the error, the lower the machining accuracy, and the smaller the error, the higher the machining accuracy.


2 Main aspects affecting machining accuracy

2.1 Dimensional accuracy
Refers to the degree of conformity between the actual size of the machined part and the tolerance zone center of the part size.
Dimensional accuracy is controlled by dimensional tolerances. Dimensional tolerance is the allowable variation in the size of a part during cutting. In the case of the same basic size, the smaller the dimensional tolerance and the higher the dimensional accuracy.

2.2 Shape accuracy
It refers to the degree of conformity between the actual geometry of the machined part surface and the ideal geometry. There are 6 items to evaluate shape accuracy, such as straightness, flatness, roundness, cylindricity and line profile. Shape accuracy is controlled by shape tolerance, and each shape tolerance is divided into 12 accuracy levels except for 13 accuracy levels of roundness and cylindricity. Level 1 is the highest and level 12 is the lowest.

2.3 Position accuracy
Refers to the difference in actual position accuracy between the relevant surfaces of machined parts. There are eight items to evaluate position accuracy, such as parallelism, perpendicularity, inclination, coaxiality, symmetry, position, round runout and full runout. Position accuracy is controlled by position tolerances, which are also divided into 12 accuracy levels.


3. Relationship between dimensional accuracy, shape accuracy and position accuracy

Usually, when designing machine parts and specifying the machining accuracy of parts, attention should be paid to controlling the shape error within the position tolerance, and the position error should be less than the dimensional tolerance. That is, the shape accuracy requirements of precision parts or important surfaces of parts should be higher than the position accuracy requirements, and the position accuracy requirements should be higher than the dimensional accuracy requirements.