The basic principle for determining the three elements is: according to the cutting requirements, first determine the post feed amount, then look up the table to get the feed amount, and then look up the table to calculate the main cutting speed through the formula. In many cases, we can use empirical data to determine the value of these three elements.

Selection method: Practice has proved that the selection of reasonable cutting parameters is related to many factors such as machine tools, tools, workpieces, and craftsmanship. The method of reasonably selecting the processing volume is as follows:

1. Rough machining is mainly to improve production efficiency, so choose a larger feed rate, a larger feed rate, and a lower cutting speed u.

2. When finishing, there are requirements for the size and surface accuracy of the main parts, so choose a smaller feed rate, a smaller feed rate, and a higher cutting speed.

3. In rough machining, it is generally necessary to give full play to the potential of the machine tool and the cutting ability of the tool. When customizing semi-finishing and finishing, CNC lathe manufacturers should pay attention to how to improve the quality of processing, and on this basis, strive to increase productivity. When the CNC lathe factory selects cutting parameters, it should be able to machine parts or tools, and the service life of the tools should not be less than one work shift or half a work shift. The specific numerical value of the CNC lathe factory should be selected according to the specifications of the machine tool manual, tool durability and practical experience. Selection of tool retraction: The selection of tool retraction should be determined according to the rigidity of the machine tool, fixture and workpiece, as well as the power of the machine tool. If the process system allows, try to choose a larger amount of back knife. In addition to leaving a margin for the follow-up process, the remaining rough machining allowance should be cut off as much as possible to reduce the number of passes.

On medium-power machine tools, the draft after roughing is generally 8-10mm (single side). CNC lathe factory's semi-finishing tool retreat is 0.5~5mm; the finishing machining tool retreat is 0.2~1.5mm. The determination of the feed rate: When the quality requirements of the workpiece can be met, in order to improve productivity, a higher feed rate can be selected. When cutting, turning deep holes or finishing turning, the CNC lathe factory should choose a lower feed rate. The feed speed should be compatible with the spindle speed and reverse feed. In rough machining, the choice of feed rate is limited by the cutting force.