First of all, compared to ordinary lathes, CNC CNC lathes have a constant wire speed cutting function, and they can be machined at the same linear velocity regardless of the end face of the car or the outer diameter of different diameters, which ensures that the surface roughness value is consistent and relatively small . The ordinary lathe is a constant speed, and different cutting speeds are different for different diameters. In the case of a fixed workpiece and tool material, finishing allowance and tool angle, the surface roughness depends on the cutting speed and the feed rate.
In the processing of surfaces with different surface roughness, a small feed rate is used for the surface with small roughness, and a larger feed rate is used for the surface with large roughness, and the variability is very good. This is difficult to achieve on ordinary lathes. Contoured parts. Arbitrary plane curve can be approximated by a straight line or an arc, and cnc precision machining has an arc interpolation function that can process various complicated contour parts. The use of cnc precision machining requires the careful use of the operator.
CNC precision machining includes fine cars, fine boring, fine milling, fine grinding and grinding.
(1) Finishing and finishing: Most of the precision light alloy (aluminum or magnesium alloy, etc.) parts of the aircraft are processed in this way. General use of natural single crystal diamond tools, blade radius of less than 0.1 microns. The precision of 1 micron and surface roughness with an average height difference of less than 0.2 micron can be obtained on a precision lathe with a coordinate accuracy of ±2 microns.
(2) Finishing: Used for machining complex aluminum or tantalum alloy structural parts. Rely on the accuracy of the guide rail and spindle of the machine tool to obtain high mutual position accuracy. High-precision milling using a finely ground diamond bit can obtain a precise mirror.
(3) fine grinding: used for machining shaft or hole parts. Most of these parts use hardened steel and have a very high hardness. Most high-precision grinding machine spindles use static or dynamic pressure fluid bearings to ensure high stability. In addition to the influence of machine tool spindle and machine bed stiffness, the precision of grinding is related to the selection and balance of the grinding wheel and the machining accuracy of the center hole of the workpiece. Grinding gives 1 micron dimensional accuracy and 0.5 micron out-of-roundness.
(4) Grinding: Use the principle of mutual grinding of the mating parts to select and process irregular raised parts on the surface to be machined. Abrasive grain diameter, cutting force and cutting heat can be precisely controlled, which is the most accurate machining method in precision machining technology. The hydraulic or pneumatic fittings in the precision servo parts of the aircraft and the bearing parts of the dynamic pressure gyro motor are all processed in this way to achieve an accuracy of 0.1 or even 0.01 μm and a microscopic roughness of 0.005 μm.