The formulation method of cutting parameters of CBN tool:
When rough machining, should be as far as possible to ensure a higher metal cutting rate and the necessary tool durability, so the general priority is to choose as large a cutting depth AP, followed by a larger feed f, and finally according to the tool durability requirements, determine the appropriate cutting speed.
When finishing, the machining accuracy and surface quality requirements of the workpiece should be guaranteed first, so the smaller feed and cutting depth are generally selected, and the higher cutting speed is selected as far as possible.
1. Selection of cutting depth
(1) The cutting depth should be determined according to the machining allowance of the workpiece. During rough machining, except for the finishing allowance, all the allowance should be removed as far as possible. When the machining allowance is too large, the process system stiffness is low, the power of the machine tool is insufficient, the tool strength is not enough or the impact vibration of discontinuous cutting is large, can be divided into multiple cutting tool. When cutting castings with hard surface layer, the thickness of cutting depth should be greater than that of hard surface layer as far as possible to protect tool tip.
(2) The machining allowance of semi-finishing and finishing is generally small, and can be removed once, but sometimes in order to ensure the machining accuracy and surface quality of the workpiece, it can also be used twice.
(3) Many times when cutting, should try to take the cutting depth of the first cutting larger, generally 213-3144 of the total machining allowance) in the medium power of the machine tool, rough cutting depth can reach 8-10mm, semi-finishing (surface roughness of RA6.3-3.2um ), the cutting depth is 0.5-2mm, finishing (surface roughness is RA1.6-0.8um), the cutting depth is 0.1-0.4mm.
2. Choice of feed
After the cutting depth is selected, the largest feed f should be selected as possible.
During rough machining, due to the large cutting force acting on the process system, the selection of feed is limited by the following factors. The rigidity of the machine tool - workpiece system, the strength of the machine feed mechanism, the effective power and torque of the machine tool, and the strength of the blade in discontinuous cutting.
In semi-finishing and finishing machining, the maximum feed is mainly limited by the roughness of workpiece surface. In the factory, the feed quantity is generally selected in a certain table based on experience (see related tables in chapters of turning, drilling, milling, etc.). If conditions are available, the cutting database can be searched and optimized.
3. Choice of cutting speed Vc
After the cutting depth AP is selected, the value of cutting speed Uc can be determined by means of calculation or table look-up method under the condition of ensuring reasonable tool durability. When determining Vc values, observe the following principles:
(1) Rough cutting, cutting depth and feed are large, so choose a lower cutting speed. When finishing, choose a higher cutting speed.
(2) The better the cutting performance of the tool material, the higher the cutting speed can be selected. Therefore, the cutting speed of carbide tool can be selected several times higher than the height of high speed steel, and the cutting speed of cubic boron oxide tool can be selected much higher than the carbide tool. In addition, when determining the cutting speed of finishing and semi-finishing, attention should be paid to avoiding the area where chip bumps and scales occur. In the case of easy vibration, the cutting speed should avoid the critical speed of self-excited vibration, in the processing of casting and forging with hard skin, processing of large parts, slender parts and thin wall parts, and intermittent cutting, should choose a lower cutting speed.
