We know that the precision machining requirements of precision machining is very high, precision machining is good rigidity, high manufacturing accuracy, accurate 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. The surface roughness depends on the cutting speed and feed speed under the condition that the material of workpiece and tool, finishing allowance and tool angle are certain.
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In processing the surface roughness of different surfaces, the roughness of the small surface choose a small feed rate, the roughness of the large surface choose a larger feed rate, good variability, this is difficult to do in ordinary lathes; profile shape of complex parts, any plane curve can be approximated by a straight line or arc, precision machining with circular interpolation function, can process a variety of complex contour parts, precision machining of the use of Good or bad need the operator's careful use.
Precision machining mainly includes precision turning, precision boring, precision milling, precision grinding and grinding processes.
(1) fine turning and fine boring: most of the precision light alloy (aluminum or magnesium alloy, etc.) parts in the aircraft are mostly processed by this method, generally with natural single crystal diamond tools, the radius of the blade arc is less than 0.1 micron, in the high-precision lathe processing can be obtained 1 micron accuracy and the average height difference of less than 0.2 micron surface unevenness, coordinate accuracy can reach ± 2 micron.
(2) Fine milling: used for machining complex shape of aluminum or beryllium alloy structural parts, relying on the accuracy of the machine's guide and spindle to obtain high mutual position accuracy, the use of carefully ground diamond cutter head for high-speed milling can obtain accurate mirror surface.
(3) fine grinding: for processing shaft or hole parts. Most of these parts are made of hardened steel with high hardness, and 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 in addition to the selection and balance of the grinding wheel and the machining accuracy of the center hole of the workpiece, etc. 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 processing method to obtain the highest precision in precision machining technology. The hydraulic or pneumatic mating parts in the precision servo parts of aircraft and the bearing parts of dynamic gyro motor are processed by this method to achieve 0.1 or even 0.01 micron accuracy and 0.005 micron micro-unevenness.
