1. Mold processing quality including machining accuracy and surface quality

Machining accuracy is the actual size of the surface of the processed parts, shape, location of the three geometric parameters and drawings required by the degree of compliance with the ideal geometric parameters.

Ideal geometric parameters, in terms of size, is the average size; in terms of surface geometry, is the absolute circle, cylinder, plane, taper and straight line, etc.; in terms of the mutual position of the surface is the absolute parallel, perpendicular, coaxial, symmetrical, etc. ... The deviation value of the actual geometric parameters of a part from the ideal geometric parameters is called the machining error.

Both machining accuracy and machining error are terms for evaluating the geometric parameters of a machined surface. Machining accuracy is measured by the tolerance grade, the smaller the grade value, the higher the accuracy; machining error is expressed in numerical terms, the larger the value, the larger the error. A high machining accuracy means a small machining 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 machining error is within the tolerance required by the part drawing, it is considered that the machining accuracy is guaranteed.

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

2. The main aspects affecting machining accuracy　

2.1 Dimensional accuracy　　

Refers to the actual size of the processed parts and the center of the tolerance band of the size of the parts in accordance with the degree of conformity.　　

Dimensional accuracy is controlled by dimensional tolerance. Dimensional tolerance is the amount of variation allowed in the size of the part in the cutting process. In the case of the same basic dimensions, the smaller the dimensional tolerance and, the higher the dimensional accuracy.　　

2.2 Shape accuracy　

Refers to the actual geometric shape of the surface of the machined part and the degree of conformity of the ideal geometric shape. Assessment of shape accuracy items are straightness, flatness, roundness, cylindricity, line profile and other 6 items. Shape accuracy is controlled by shape tolerance, the shape tolerance, in addition to roundness, cylindricity, divided into 13 accuracy levels, the rest are divided into 12 accuracy levels, the highest level 1, the lowest level 12.　　

2.3 Positional accuracy

Refers to the actual positional accuracy difference between the relevant surfaces of the processed parts. Assessment of positional accuracy of the project has a parallelism, perpendicularity, inclination, coaxiality, symmetry, positional, circular runout and full runout and other eight items. Positional accuracy is controlled by positional tolerance, the positional tolerance of each item is also divided into 12 accuracy levels.

Usually in the design of machine parts and parts machining accuracy, should pay attention to the shape error control in the position tolerance, position error should be less than the size tolerance. That is, precision parts or parts of the important surface, its shape accuracy requirements should be higher than the positional accuracy requirements, positional accuracy requirements should be higher than the size accuracy requirements.