The quality of the machine depends on the processing quality of the part and the assembly quality of the machine. The machining quality of the part includes the machining accuracy and surface quality of the part. The machining precision refers to the actual geometric parameters (size, shape and position) and ideal geometry of the part after machining. The degree to which the parameters match.
The difference between them is called the machining error. The size of the machining error reflects the level of machining accuracy. The greater the error, the lower the machining accuracy, and the smaller the error, the higher the machining accuracy. Main aspects that affect processing accuracy.
1. Dimensional accuracy
Refers to the degree to which the actual dimensions of the machined parts meet the tolerances of the part dimensions. Dimensional accuracy is controlled by dimensional tolerances. Dimensional tolerance is the amount of variation allowed for part size during machining. In the case of the same basic dimensions, the smaller the dimensional tolerance, the higher the dimensional accuracy.
2. Shape accuracy
Refers to the degree to which the actual geometry of the surface of the finished part matches the ideal geometry. The items for evaluating the shape accuracy include six items such as straightness, flatness, roundness, cylindricity, and line outline. The shape accuracy is controlled by the shape tolerance. The shape tolerances are divided into 12 precision grades except for the roundness and cylindricity. Level 1 is the highest and level 12 is the lowest.
3. Position accuracy
Refers to the difference in actual positional accuracy between the surfaces of the parts after machining. The items for assessing positional accuracy include eight items: parallelism, verticality, inclination, concentricity, symmetry, position, round runout, and full runout. Position accuracy is controlled by positional tolerance, and the positional tolerances of each item are also divided into 12 accuracy levels.