Dongguan CNC processing plant in the direction of machining accuracy is the actual size, shape, position of the machined part surface of the three geometric parameters and the drawing requirements of the ideal geometric parameters. The ideal geometric parameter, for size, is the average size; For the surface geometry, it is absolute circle, cylinder, plane, cone and straight line; For the mutual positions between surfaces, they are absolutely parallel, vertical, coaxial and symmetrical. The deviation between the actual and ideal geometric parameters of a part is called machining error.
1: Introduction
The machining accuracy of Dongguan CNC machining plant is mainly used to produce the degree of products. Machining accuracy and machining error are terms to evaluate the geometric parameters of machined surface. Machining accuracy is measured by tolerance grade. The smaller the grade value is, the higher the accuracy is; Machining error is expressed by numerical value. The larger the numerical value is, the larger the error is. High machining accuracy means small machining error, and vice versa. There are 20 tolerance grades from IT01, it0, it1, it2, it3 to it18. If IT01 indicates, the machining accuracy of the part is the highest, if it18 indicates, the machining accuracy of the part is the lowest. Generally speaking, it7 and it8 are medium machining accuracy.
The actual parameters obtained by any processing method in Dongguan CNC processing plant are not absolutely accurate. From the function of the parts, as long as the processing error is within the tolerance range required by the part drawing, it is considered that the processing accuracy is guaranteed.
The quality of the machine depends on the processing quality of the parts and the assembly quality of the machine. The processing quality of the parts includes the processing accuracy and surface quality of the parts. Machining accuracy refers to the degree that the actual geometric parameters (size, shape and position) of the machined parts 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: dimensional accuracy
Dongguan CNC processing factory refers to the conformity degree between the actual size of the processed parts and the tolerance zone center of the parts size. Shape accuracy: refers to the degree of conformity between the actual geometry of the machined part surface and the ideal geometry. Position accuracy: refers to the actual position accuracy difference between the relevant surfaces of the machined parts. Interrelation: generally, when designing machine parts and specifying 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 dimension tolerance. That is to say, the shape accuracy of precision parts or important surfaces should be higher than the position accuracy, and the position accuracy should be higher than the size accuracy.
3 adjustment method
1. Adjust the process system
Adjustment of trial cutting method in Dongguan CNC processing plant: through trial cutting - measuring size - adjusting the cutting tool's feed - cutting along the tool - cutting again and again until the required size is reached. This method has low production efficiency and is mainly used for single piece and small batch production. Adjustment method: by adjusting the relative position of the machine tool, fixture, workpiece and cutter in advance to obtain the required size. This method has high productivity and is mainly used for mass production.
2. Reduce the machine error
1) To improve the manufacturing accuracy of the spindle components, we should improve the rotation accuracy of the bearing
① High precision rolling bearing is selected;
② High precision multi oil wedge hydrodynamic bearing is adopted;
③ High precision hydrostatic bearing is adopted
It is necessary to improve the accuracy of the parts related to the bearing
① Improve the machining accuracy of box support hole and spindle journal;
② Improve the machining accuracy of the surface matching with the bearing;
③ Measure and adjust the radial runout range of corresponding parts to make error compensation or cancellation.
2) Proper preloading of rolling bearings: 1. Clearance can be eliminated; ② Increase the bearing stiffness; ③ The rolling element error is homogenized.
3) So that the spindle rotation accuracy is not reflected on the workpiece
3. Reduce the transmission error of transmission chain
1) The number of transmission parts is small, the transmission chain is short, and the transmission precision is high;
2) It is an important principle to ensure the transmission accuracy to adopt the deceleration transmission (I < 1), and the closer to the end of the transmission pair, the smaller the transmission ratio should be;
3) The precision of the end part should be higher than that of other transmission parts.