First, the principle of coarse and then fine
In the CNC machining, according to the machining accuracy of the parts, rigidity and linear changes in the machining process, should be divided in accordance with the separation of roughing and finishing to divide the process, that is, first complete roughing, then semi-finishing and finishing. For a certain machined surface, should be completed in the order of roughing, semi-finishing and finishing. In rough machining, in order to ensure the machine tool - fixture - tool - workpiece processing system processing quality, tool durability and rigidity of the premise, should give full play to the performance of the machine tool and cutting performance of the tool, and through a large number of cutting times, so that the processing conditions of each part before processing as uniform as possible. Finishing processing is mainly to ensure the machining accuracy and surface quality of the parts, so usually the final contour of the parts should be made by the last cut continuous finishing. In order to ensure the processing quality, generally should maintain 0. 2-0 to 6mm for finishing allowance, preferably between roughing and finishing interval, fully recover the deformation of roughing parts, and then precision machining to improve the machining accuracy of the parts.
Second, the process maximum concentration, a positioning principle
In general, in the CNC machine tools, especially in the machining center on the processing parts and processes can be concentrated to the maximum extent, that is, the parts should be completed in a fixture as far as possible most or all of the processes that our CNC machine tools can process, and CNC machining tends to focus on the work program, which can reduce the number of machine tools and workpiece clamping times, reduce unnecessary positioning errors and improve productivity. For the processing of coaxiality requirements of the hole system, once installed, the processing of all the same axis hole system should be completed by continuous replacement sequence, and then the other positions of the hole to eliminate the impact of repeated positioning errors and improve the coaxiality of the hole system.
Third, the principle of first near and then far, first surface and then hole
cnc hardware machining according to the distance of the machined parts relative to the tool point, usually first to the parts near the tool point, and then to the parts away from the tip of the tool, in order to shorten the tool movement distance and reduce the empty stroke time. In turning, it is beneficial to maintain the hardness of the embryo or semi-finished product and improve the cutting conditions. For the machining of parts with milled surfaces and bores, milling can be done in the order of milling first and then boring. Due to the large cutting force when milling the plane, the part is easy to deformation, milling the surface first, then boring, so that it can recover for a period of time, and then boring, which is conducive to ensuring the accuracy of the hole processing. Secondly, if the hole is bored first and then the plane is milled, the hole will produce burrs and flying edges, which will affect the assembly of the hole.
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