How to improve the machining accuracy of mould effectively

With the rapid development of China's economic construction, the improvement of people's living standards, the rapid development of China's construction industry, the increasing demand for aluminum profiles, therefore, the demand for aluminum alloy extrusion mold design, manufacturing and production is also increasing.

Aluminum profile products are widely used in all walks of life, and the products are constantly developing towards diversification and complexity, and the requirements for the processing accuracy of products are increasingly high. Extrusion die is the basis of extrusion process, which not only determines the shape, size accuracy and surface state of extruded products. The quality requirements are higher and higher, and the processing requirements of the mould are also improved. Machining accuracy is the biggest requirement of machining, so how to effectively improve the machining accuracy of mold has become a more 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 machined part surface and the ideal geometric parameters required by the drawing. The ideal geometric parameter is the average size for the size, the absolute circle, cylinder, plane, cone and straight line for the surface geometry, and the absolute parallel, vertical, coaxial and symmetry for the mutual position between the surfaces. The deviation between the actual geometric parameters and the ideal geometric parameters is called machining error.

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

The actual parameters obtained by any processing method will not be absolutely accurate. From the function of the parts, as long as the processing error is within the tolerance range 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 and the surface quality of the parts. The machining accuracy of the parts refers to the degree that the actual geometric parameters (size, shape and position) after machining are consistent with the ideal geometric parameters. The difference between them is called machining error. The machining error reflects the machining accuracy. The larger the error is, the lower the machining accuracy is, and the smaller the error is, the higher the machining accuracy is.

2 main aspects affecting machining accuracy

2.1 dimensional accuracy

It refers to the degree of conformity between the actual dimension of the processed part and the tolerance zone center of the part dimension.

Dimensional accuracy is controlled by dimensional tolerance. Dimension tolerance is the allowable variation of part dimension in machining. In the case of the same basic dimension, the smaller the dimension tolerance is, the higher the dimension accuracy is.

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 the shape accuracy, such as straightness, flatness, roundness, cylindricity, line contour, etc. The shape accuracy is controlled by the shape tolerance. Each shape tolerance is divided into 12 Accuracy grades except the roundness and cylindricity. Level 1 is the highest and level 12 is the lowest.

2.3 position accuracy

It refers to the actual position accuracy difference between related surfaces of parts after machining. There are eight items to evaluate the position accuracy, such as parallelism, verticality, inclination, coaxiality, symmetry, position, circular runout and total runout. The position accuracy is controlled by the position tolerance. The position tolerance of each project is also divided into 12 accuracy levels.

3 Relationship among dimensional accuracy, shape accuracy and position accuracy

Generally, when designing machine parts and specifying the machining accuracy of parts, attention should be paid to control the shape error within the position tolerance, which should be less than the dimension tolerance. That is to say, the shape accuracy requirements of precision parts or important surfaces of parts shall be higher than the position accuracy requirements, and the position accuracy requirements shall be higher than the size accuracy requirements.