Cut and cutting parameter
- source:GAENOR CNC Machining
1 cutting process passes course of understanding metal cutting, we can know a metal is how cutting comes down, can understand cutting force, cutting tool to wear away to machine medium physical phenomenon with the cutting such as treatment surface quality, improve cutting efficiency to master, reduce cost and assure to machine the method of a few treatment such as quality to lay next foundations. Metallic cutting process is actual the plasticity that the generation below the extruding that is cutting tool be been in by cutting metal layer cuts slippage is out of shape process, bouncy also in cutting process be out of shape, but be out of shape with plasticity photograph comparing is negligible. And in cutting process, still can produce the tumor that accumulate bits, it produces an effect to cutting again conversely, the specification parts to these two respects under. (1) the in be out of shape the metal is machining a process meeting of metallic cutting process happens cut and slippage, graph the 4 skid wire that expressed a metal and contrail of going from place to place, among them transverse line is metallic flow trochoid, fore-and-aft line is a metal cut skid wire. Graph the 5 slippage courses that represented a metal. By the graph knowable, the plasticity of metallic cutting process is out of shape can differentiate normally 3 are out of shape area, each area characteristic is as follows: 1) the first be out of shape area cut metal from begin plasticity to be out of shape cut slippage to be finished basically, area of this one process is called the first be out of shape area. The plan will emerge flexibility to be out of shape above all below the extruding of the skid wire in process of 4 metals cutting and streamline cut metal in cutting tool, when the biggest cut what stress exceeds material to succumb when the limit, produce plasticity to be out of shape, if the graph is shown 4 times, the metal can cut slippage along OA line, OA is called only then skid wire. As the shift of cutting tool, this kind of plasticity is out of shape will increase stage by stage, when entering OM line, this kind of slippage is out of shape stop, OM is called eventually skid wire. Now with the some change in metallic cut the process explains. By the graph 5 are shown, in metallic cutting process, ceaseless Xiang Dao of a bit P provides the metal in cut cutting blade is mobile, when entering OA line at this o'clock, happen cut slippage, p is nodded to 2, the slippage of process relay add of 3 flow waiting for a dot, should enter this kind of when 4 o'clock slippage on OM line to stop, 2 ' - 2, 3 ' - 3, 4 ' - 4 measure for each slippage of before the point is opposite a bit. Of this area be out of shape the process can adopt a plan 5 figure express, the layer that here area is like cut to be folded pieces together piece, in cutting process middle-level piece between produced opposite slippage. The area between OA and OM is the first be out of shape area Ⅰ . Graph 5 the first be out of shape area metal slippage the first be out of shape the area is metallic cutting be out of shape the biggest in the process be out of shape area, inside this area, the metal will produce many heat in metal cutting, consume major power. This area is narrower, width only 0.
02 ～ 0.
2 ㎜. 2) the 2nd be out of shape the area produces material of cut of plasticity metabolic metal to pass the first be out of shape face of the knife before cutting tool of the edge after the area is poured out of, before stand by knife face place is formed the 2nd be out of shape area. If the graph shows Ⅱ 4 times,be out of shape area. Be out of shape in this area, because cut material is mixed by the extruding of face of the knife before cutting tool,chafe, be out of shape farther aggravate, material herein fiber is changed, rate of going from place to place is decelerated, even backwater is advanced on knife face. And, cut bits and before the pressure of knife face is very great, be as high as 2 ～ 3GPa, chafe from this the high temperature that the quantity of heat of generation also makes cut bits and tool cover temperature to rise to hundreds of degrees, range of the knife before the bottom that cut bits and cutting tool occurs felt phenomenon. After producing felt phenomenon, cut bits and before the attrition between knife face is not general external friction, and those who turn felt into layer and its superstratum metal inside attrition. This kind inside attrition and external friction are different, the character of stress of going from place to place of it and material and felt area are concerned, felt area is larger, attrition force also is jumped over inside big. Graph 6 showed the attrition state when producing felt phenomenon. By the graph knowable, according to attrition state, cent is the interface that cut bits two parts: Felt part is inside attrition, the unit of this part is tangential stress is equal to material succumb intensity τ S; External friction part is beyond felt part, namely sliding friction part, the unit of this part is tangential stress is reduced by τ S 0. Whole contact also showed in the graph inside area the distributinging circumstance of stress σ γ , place of point of a knife, stress is the greatest, reduce stage by stage 0. Graph 6 cut bits and before the attrition Nextpage3 of knife face) the 3rd extruding that is out of shape area metal cut already was machining the surface to get share of blunt circle of cutting tool edge produces plasticity with attrition to be out of shape partial area. If pursue,4 show Ⅲ share. The 3rd be out of shape blunt circle of the formation of the area and edge is concerned. Because edge cannot be absolutely sharp, why to no matter use,plant means blade is ground, edge always can have N of γ of one blunt round radius. N of the γ after blade grinds general high-speed steel is 3 ～ 10 μ M, 32 μ of the about 18 ～ after hard alloy cutting tool is ground M, if use grinding of granule diamond emery wheel, γ N is the smallest can achieve 3 ～ 6 μ M. Additional, wear away with respect to meeting generation after edge cutting, increase edge blunt circle. Graph 7 expressed what the surface already machined below blunt round circumstance to consider where a thing can be put to best use fashion a process. When cut approachs the crucial point with fixed rate, can appear cut with slippage, metal of metallic cut majority is passed the 2nd be out of shape of the area be out of shape along eventually direction of slippage layer OM is poured out of, as a result of the existence of edge blunt circle, the metallic cut that there is A of thick △ of one little part below in dot of blunt round O cannot be poured out of along OM direction, be squashed to go by edge blunt circle, after blunt round B orders where a thing can be put to best use of this part course, BC of face of the knife after getting paragraph extruding and attrition, through BC paragraph hind, this part metal begins flexibility to restore, restore to be △ H highly, in resuming a course with hind part of knife face CD produces clash, this part cut is in OB, BC, CD paragraph after extruding and attrition, formed the treatment mass that already machined the surface. Say so the 3rd be out of shape the area machines exterior quality to produce very big effect to workpiece. Graph 7 already machined the surface to form process above to be out of shape in cutting process to metallic cut area metabolic characteristic undertook introductory 3 times, if rise these 3 area integratedly, if the graph notifies a procedure 8 times,can regard. Enter when metallic cut the first be out of shape zone time, metallic happening cuts slippage, and metallic fiber is changed, when this cut approachs the crucial point, metallic fiber is longer lap it is all round cutting blade, in O the dot ruptures finally two parts, face of the knife before one part edge is poured out of become cut bits, another part is become edge to already machined the surface by the extruding of blunt round part and attrition, parallel of direction of exterior metallic fiber already machined the surface, this metal has the quality that differs with matrix organization. Graph the cutting of 8 cutting tool completes a process (2) below the formation of the tumour that accumulate bits and fixed to machining an influence to be in cutting rate and the condition that carry successive cutting, when processing plasticity data, in face of the knife before cutting tool often a section plane shows felt three cornuted nugget, this metal is called to accumulate bits tumour. The formation of the tumour that accumulate bits is OK basis the 2nd be out of shape the characteristic of the area will explain. When metallic cut from eventually when slide surface is poured out of, get the extruding of face of the knife before cutting tool and attrition, surface contact of the knife before cutting bits and cutting tool face temperature is elevatory, when extruding force and temperature reach certain level, produce felt phenomenon, often say namely " cold welding " . When cutting bits to had shed the ground floor with cutting tool conglutinate, the attrition inside generation, at this moment metallic occurrence treatment is sclerotic above ground floor, be together with rock-bottom conglutinate, be brought up gradually, become the tumour that accumulate bits, if pursue,9 are shown. Graph the generation that the 9 tumour that accumulate bits accumulate bits tumour to machining an influence and not only with the treatment of material sclerosis is concerned, and also concern with the temperature of the area before edge and pressure. The treatment sclerosis sex of average data is stronger, easier generation accumulates bits tumour; Temperature and pressure are too low won't produce the tumor that accumulate bits, temperature also won't produce the tumor that accumulate bits too high. Answer relatively with temperature, cutting rate is too low won't produce the tumor that accumulate bits, cutting rate is too high, the tumour that accumulate bits also won't happen, because cutting speed has bigger effect to cutting temperature. Hardness of the tumour that accumulate bits is very tall, the 2 ～ that are workpiece material hardness 3 times, can undertake cutting to the metal euqally with cutting tool. It can produce following effects to metallic cutting process. 1) O of γ of the horn before the horn before actual cutting tool increases cutting tool points to the included angle between knife face and tool reference plane, its concept will be in hind the section is discussed in detail. If plan institute is shown, because accumulate the conglutinate of bits tumour, the horn before cutting tool increased angle of B of a γ , be like a tumour that cut bits to regard cutting tool as the word of one part, the horn before undoubted and actual cutting tool increases, it is B of γ of γ O ＋ now. The horn before cutting tool increases can reduce cutting force, have positive effect to cutting process. And, the high Hb of cutting tumour is bigger, the part before actual cutting tool is larger also, cutting is easier. 2) actual cutting ply increases by the graph 9 can see, when cutting tumour exists, actual metallic cut ply is compared HD of a △ increased when having cutting tumour, apparent, this is adverse to the control of workpiece cutting dimension. Notable is, the addition of HD of this ply △ is not fixed, because cutting tumour is changing ceaselessly, it is a generation, grown, the periodic change process that falls off finally, such possibilities arise vibration in treatment. 3) the change that surface roughness of the surface after treatment increases the tumour that accumulate bits not only it is whole, and itself of the tumour that accumulate bits also has process of a change. The bottom of the tumour that accumulate bits compares stability commonly, and its coping is extremely flabby calm, via regular meeting burst, form again next. Cracked is followed partly cut bits to eliminate, another part stays in treatment apparently, make machine the surface to become very coarse. Can see, if want to raise the surface to machine quality, must control the happening of the tumour that accumulate bits. 4) the durability of cutting cutting tool reduces the conglutinate that goes up in cutting tool from the tumour that accumulate bits to look, the tumour that accumulate bits should have protective effect to the knife, it replaces cutting tool cutting, reduced cutting tool to wear away. But the conglutinate of the tumour that accumulate bits is not stable, it falls off can periodicly from cutting tool, when he falls off, the likelihood makes metal of cutting tool surface flakes, make cutting tool wears away thereby increase. To hard alloy cutting tool this are behaved particularly apparent. Nextpage [exemple 1] master of some plant lathe operator is in rough machining when a spare parts, he used the treatment method that produces the tumor that accumulate bits on cutting tool, and when finish machining, he avoids to accumulate the generation of bits tumour hard again, is excuse me this why? In prevent to accumulate bits tumour respect, you think to be able to use what method. Answer: According to this section the tumour that accumulate bits is opposite the influence analysis of treatment is knowable, the tumour that accumulate bits can increase the role before cutting tool is actual, make cutting easier, so this master used the treatment method that uses the tumour that accumulate bits when rough machining, but the tumour that accumulate bits is very flabby calm, it falls off can periodicly, this caused cutting tool actual cutting ply is changing, affect the treatment dimension precision of the spare parts, additional, of the tumour that accumulate bits flake and of appearance irregular make the spare parts machines the surface to become very coarse again, surface of influence spare parts is bright and clean degree. Be in so finish machining phase, this master avoids to accumulate the happening of bits tumour hard again. The account that produces according to accumulating bits tumour can know, the tumour that accumulate bits is attrition of face of the knife before cutting bits and cutting tool, attrition temperature reachs certain level, cut bits and before layer metal produces knife surface contact of the generation when treatment is sclerotic, because this can take the step of the following respects,will avoid accumulate the happening of bits tumour. · is solved from the phase of heat treatment craft before treatment above all. Pass heat treatment, raise the hardness of hardware data, the treatment that reduces material is sclerotic. · adjusts cutting tool angle, the horn before increasing, reduce thereby cut bits to be opposite the pressure of face of the knife before cutting tool. · moves low cutting rate, make face temperature reduces surface contact of the knife before cut and cutting tool, avoid the happening of felt phenomenon. · or use higher cutting rate, raise cutting temperature, because temperature is high it is certain to arrive degree, the tumour that accumulate bits also won't happen. · changes cutting fluid, use the cutting liquid with lubricant better performance, reduce cutting attrition. 2.
The section on element of metabolic of 2 influences cutting made the introduction to characteristic of metallic cutting metabolic, this will is opposite element of metabolic of influence metal cutting undertakes an analysis. Main from speed of ply of parameter of geometry of workpiece material, cutting tool, cutting and cutting 4 respects undertake introductory. (1) workpiece material passes a test, can discover workpiece data strength is mixed cut bits to be out of shape have close relationship. Graph 10 showed data strength is mixed cut bits to be out of shape the relation curve between coefficient, abscissa σ shows the strength of workpiece material, ordinate ξ represents material be out of shape coefficient, can see from the graph, as the accretion of workpiece data strength, cut bits be out of shape smaller and smaller. Graph 10 data strength is right be out of shape the influence of coefficient (2) parameter of cutting tool geometry is in parameter of cutting tool geometry, the horn before cutting tool is to affect the metabolic that cut bits important parameter, influence of the horn before cutting tool cuts bits to pour out of direction. By the graph 7 can see, when O of γ of the horn before cutting tool increases, cut will compare the metal that pours out of along knife face to be poured out of gentlily, the metal cuts bits be out of shape also meet decrescent. Through the cutting that makes to place of high-speed steel cutting tool the experiment also proved this. Below same cutting rate, o of γ of the horn before cutting tool heals big, material is out of shape coefficient heals small. In addition radius of circular arc of point of a knife is out of shape to cutting influential also, radius of circular arc of point of a knife is bigger, show point of a knife is blunter, bigger also to machining the surface to squash, exterior cutting is out of shape bigger also. (3) cutting speed by the graph 11 can see, the material that changes along with cutting speed is out of shape coefficient curve is not degressive all the time, be in however some paragraph have a wave crest, this is actual the influence that is generation of the tumour that accumulate bits. So cutting speed is two to cent of material metabolic influence paragraph, one is this paragraph to accumulate bits tumour, another is not to have the tumour that accumulate bits paragraph. Graph the material that 11 cutting speed changes is out of shape coefficient curve is in the tumour that accumulate bits paragraph, cutting rate basically cuts bits metabolic influence to come true through accumulating bits tumour to be opposite to cutting bits metabolic to affect. Level increases in the tumour that accumulate bits, the tumour that accumulate bits increases as the accretion of cutting speed, the tumour that accumulate bits is bigger, the part before actual cutting tool is larger also, cut bits be out of shape decrease relatively, be in so this phase, when cutting rate increases, material is out of shape coefficient ξ also decreases. As the addition of speed, the tumour that accumulate bits increases certain level to be met again subsidise, in subsidise phase, the tumour that accumulate bits is reduced as the addition of cutting speed, in the meantime, the horn before actual cutting tool also is reduced, of material be out of shape will increase, in the tumour that accumulate bits when complete subsidise, material is out of shape the will biggest. Be in wave crest position of the curve right now. Escape this accumulates bits tumour paragraph, material is out of shape coefficient is reduce as the addition of cutting speed. Because plasticity metabolic transmits speed,basically be slower than stretch metabolic, when rate is low, metal only then cut a face to be OA, when rate increases fixed cost, metallic flow rate is more than plasticity to be out of shape speed, be out of shape not adequately in OA face metal, be equivalent to only then after cutting an area, move to OA` face (see a picture 12) , cut face OM eventually also hind move to OM` , the first be out of shape move after the area, make material is out of shape coefficient is reduced. Additional, rate is older, coefficient of friction is reduced, material is out of shape coefficient also can be reduced. Graph 12 cutting speed is affected to cutting an area (4) if cutting ply pursues show 11 times, showed feed (namely cutting ply) affect to cutting bits metabolic. Be in without the tumour that accumulate bits paragraph, feed F is bigger, of material be out of shape coefficient ξ is jumped over small. CNC Milling CNC Machining