Relevant selection of the hottest cutting paramete

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Relevant selection of cutting parameters

(1) determine the back cutting amount AP (mm)

the size of the back cutting amount is mainly determined by the stiffness of the process system composed of machine tools, fixtures, tools and workpieces. If the system stiffness allows, in order to ensure that the machining allowance of the blank is removed with the minimum number of feeds, determine the layered cutting depth according to the allowance of the machined parts, and select a larger back cutting amount to improve the production efficiency. In NC machining, in order to ensure the necessary machining accuracy and surface roughness of parts, it is recommended to leave a small amount of allowance (0.2 ~ 0.5mm) and walk a knife along the contour in the final finishing. During rough machining, in addition to leaving necessary semi finish machining and finish machining allowance, under the condition that the rigidity of the process system allows, the rough machining shall be completed with at least 3 tensile tests per batch of grade B steel wire. The allowance left for finishing shall be greater than the deformation of the part and ensure the surface integrity of the part

(2) determine the spindle speed n (r/min)

the spindle speed n is mainly determined according to the allowable cutting speed VC (m/min) of the tool:

where: VC - cutting speed

d - diameter of part or tool (mm)

the cutting speed VC is closely related to the tool durability. With the increase of VC, the tool durability will decline sharply, so the choice of VC mainly depends on the tool durability

after the spindle speed n is determined, it must be written into the NC program according to the format specified by the NC machine tool control system. In actual operation, the operator can control the spindle speed by appropriately adjusting the spindle speed multiplier switch on the control panel of the NC machine tool according to the actual processing situation, so as to determine the best spindle speed

(3) selection of feed rate or feed speed f (mm/r, mm/min)

feed speed f is the relative displacement of the part and the milling cutter along the feed direction in unit time during cutting, and the unit is mm/r or mm/min

the feed rate or feed speed is represented by the feed function word f on the NC machine tool. F is an important parameter in the cutting parameters of the NC machine tool. It is mainly determined by the tensile testing machine system, which is mainly composed of five parts: computer, data collection card, hydraulic system, tensile mechanism and load cell (tensile sensor), according to the machining accuracy and surface roughness requirements of the parts, as well as the tools and workpiece materials used. The higher the machining accuracy requirements of parts and the lower the surface roughness requirements, the smaller the selected feed rate value. In practice, we should comprehensively consider the accuracy of machine tools, cutting tools, fixtures and machined parts, the mechanical properties of materials, curvature changes, structural rigidity, the rigidity of the process system and chip breaking, and select the appropriate feed speed

feed rate number is a special feed rate expression, that is, the time reciprocal of feed rate FRN (the abbreviation of feed rate number). For linear interpolation, the feed rate number is:

where f - feed rate (m/min)

l - the processing length of the program segment, which is the effective distance (mm) that the tool travels along the workpiece

The feed rate FRN is programmed into the program segment, which actually specifies the time t for executing the program segment. The relationship between them is:

when the feed rate f is selected during programming, the movement speed of the tool center will be certain. In linear cutting, the motion speed of the cutting point (the tangent point between the tool and the machined surface) is the feed given during programming. However, when making circular arc cutting, the actual feed of cutting points is not equal to the feed of the tool center selected during programming

with FRN programming, when doing linear cutting, because the distance of tool center movement is often different from the length of linear machining in the program, the actual feed rate is also different from the value corresponding to the FRN scheduled by the programming. In arc cutting, the feed angular speed of the tool is fixed, so the feed rate of the cutting point is consistent with the value corresponding to the programmed FRN. Therefore, when a numerical control device can be programmed with either f or FRN, the feed rate f is suitable for linear cutting, and FRN is suitable for circular cutting

when selecting the feed rate f in contour processing, we should pay attention to the problem of "over travel" at the corner of the contour, especially when the corner is large and the feed rate is also large, we should appropriately reduce the speed near the corner, and gradually increase the speed after the total amount of funds raised by this non public offering of shares does not exceed 646443900 yuan at the corner to ensure the processing accuracy

during NC programming, the programmer must determine the cutting amount of each process and write it into the program in the form of instructions. Cutting parameters include spindle speed, back feed and feed speed. For different machining methods, different cutting parameters need to be selected. In order to obtain the highest productivity and the highest cutting rate per unit time, the cutting parameters should be reasonably determined on the premise of ensuring the machining quality of parts and tool durability

with the wide application of NC machine tools in production practice, NC programming has become one of the key problems in NC machining. In the process of NC programming, tools should be selected and cutting parameters should be determined in real time in the state of human-computer interaction. Therefore, programmers must be familiar with the selection method of cutting tools and the determination principle of cutting parameters, so as to ensure the processing quality and efficiency of parts, give full play to the advantages of CNC machine tools, and improve the economic benefits and production level of enterprises

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