We know that precision machining requires high precision. Precision machining has good rigidity, high manufacturing accuracy and precise tool setting, so it can process parts with high precision requirements. So which parts are suitable for precision machining?
First of all, compared with ordinary lathe, CNC lathe has constant linear speed cutting function, no matter for turning end face or different diameter outer circle can be processed with the same linear speed, that is to ensure the surface roughness value is consistent and relatively small. While ordinary lathe is constant speed, the cutting speed is different for different diameters. Under the condition that the material of workpiece and tool, finishing allowance and tool angle are certain, the surface roughness depends on the cutting speed and feed speed.
When processing the surface with different surface roughness, a small feed speed is chosen for the surface with small roughness, and a larger feed speed is chosen for the surface with large roughness, with good variability, which is difficult to be achieved in ordinary lathes. Parts with complex contour shapes. Any plane curve can be approximated by a straight line or arc, cnc precision machining with arc interpolation function, can process a variety of complex contours of the parts. cnc precision machining needs the careful use of the operator's good or bad.
CNC precision machining mainly has fine turning, fine boring, fine milling, fine grinding and grinding processes.
(1) fine turning and fine boring: the majority of precision light alloy (aluminum or magnesium alloy, etc.) parts of aircraft are mostly processed by this method. Generally use natural single crystal diamond tools, the radius of the cutting edge is less than 0.1 micron. In the high precision lathe processing can obtain 1 micron accuracy and average height difference of less than 0.2 micron surface unevenness, coordinate accuracy can reach ± 2 micron.
(2) Fine milling: used for processing complex shape of aluminum or beryllium alloy structural parts. Rely on the accuracy of the machine's guide and spindle to obtain high mutual position accuracy. High-speed milling with carefully ground diamond tips can obtain accurate mirror surfaces.
(3) Fine grinding: used for machining shaft or hole type parts. Most of these parts are made of hardened steel, which has high hardness. Most high-precision grinding machine spindles use hydrostatic or dynamic pressure liquid bearings to ensure high stability. The ultimate accuracy of grinding is influenced by the machine tool spindle and bed stiffness, but also by the selection and balance of the grinding wheel and the machining accuracy of the center-center hole of the workpiece. Fine grinding can obtain a dimensional accuracy of 1 micron and an out-of-roundness of 0.5 micron.
(4) Grinding: Using the principle of mutual research of mating parts to selectively process the irregular raised parts on the machined surface. The grinding grain diameter, cutting force and cutting heat can be precisely controlled, so it is the most - high-precision processing method in precision machining technology. The hydraulic or pneumatic mating parts of precision servo parts of aircraft and bearing parts of dynamic gyro motors are machined by this method to achieve 0.1 or even 0.01 micron accuracy and 0.005 micron micro-unevenness.
