Exceed the technical difficulty that imperceptible cutting machines and countermeasure

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Summary: Analysed the mechanism that exceeds imperceptible cutting treatment, characteristic and technical difficulty, right the relation of ply of the smallest cutting and radius of circular arc of cutting tool point undertook quantifying an analysis. Of the small vibration in discussing cutting course, cutting tool wear away and the element such as the changes environment of characteristic, treatment stability of the minim cutting processability of collapse blade, material, machine tool is right the impact that exceeds imperceptible cutting process, put forward to solve measure. 1 foreword is imperceptible processing technique is the production processing technique that points to small size part. As the development of industry of aerospace, national defence, modern medicine and biology project technology, appeared more and more miniaturization, miniature spends equipment and small size part, all sorts of small machine that use imperceptible processing technique to make if pump of sensor of miniature electromotor, miniature, miniature having increasingly wide application perspective. Modern production technology is higher and higher also to the requirement of imperceptible treatment, already developed to exceed imperceptible treatment; To the treatment of existing production technology the limit is challenged, development superprecision, exceed imperceptible treatment and accept rice processing technique, already made the way of a development of modern production technology. Imperceptible processing technique includes all sorts of traditional accurate machining methods not only, be like,still include at the same time the non-traditional machining method such as electron beam treatment, ionic bundle of treatment, chemical treatment. These non-traditional machining methods received very good application in imperceptible treatment domain at present, and the imperceptible, cutting treatment that exceeds imperceptible domain is existing however difficulty of a few technologies, restricted its wide application. Because even if traditional machining, not identical also to the treatment mechanism of small size and average size and method. The article exceeds the mechanism of imperceptible treatment through research, the analysis exceeds the technical difficulty in imperceptible treatment to reach its the influence to machining a process, put forward to solve measure. Common cutting and small fine cutting are machining the mechanism that 2 exceed imperceptible cutting to machine each are not identical on mechanism. When common cutting, because workpiece size is larger, permission cutting deepness, feed all bigger; And when imperceptible cutting, because workpiece size is small, do not allow to use bigger cutting deepness and feed from intensity, stiffness, it is the requirement that assures work measure precision at the same time, the surface of final precision work excises a ply to must be less than its precision value, because of this cutting dosage must very small. Average metallic data is by diametical amount to micron is formed to the grain of hundreds micron. Because the cutting deepness of imperceptible cutting is very small, especially inferior of micron and accept rice class exceed imperceptible cutting, normally cutting deepness is less than the grain diameter of material, make cutting can undertake inside grain only, at this moment cutting is equivalent to discontinuous to each body undertaking cutting, so imperceptible cutting is a kind of interrupted cutting. Because material is put in the inhomogenous sex that microcosmic blemish and material distributing character, make the cutting tool cutting force change when cutting bigger, and cutting blade will get bigger impact and vibration. Imperceptible cutting machines the cutting force feature of imperceptible cutting is one kind exceeds minim depart technology, the cutting force near point of cutting tool of the diamond when cutting is inferior Newtonian step is smaller even. Cutting force reflects the purify course that cuts bits can clearly, because this studies cutting force model,conduce to understanding cutting the cutting character of bits. The cutting force feature when imperceptible cutting is: Cutting force is small, unit cutting muscularity, and cut fight force greatly to be more than advocate cutting force; Cutting force follows cutting to reduce and increase of deepness, and cutting deep very hour cutting force can increase quickly. This is the dimension effect of cutting force. Of the physical model of force of the cutting when imperceptible cutting and cutting tool point inferior micron construction concern is close. As a result of the existence of radius of circular arc of cutting blade point, cutting blade measures class cutting in accept rice from time to tome a very large part before losing, make cutting is out of shape increase, the unit cutting muscularity when reason cutting; In the meantime, because imperceptible cutting often undertakes in grain interior, cutting force must be more than the element of crystal interior, atomic adhesion, make the cutting force on unit cutting area increases quickly consequently. Increase along with the accretion of cutting deepness with force of the cutting when common cutting different, the cutting deepness when imperceptible cutting and feed are very small. As a result of the existence of radius of circular arc of cutting tool point of a knife and radius of point circular arc, make cutting is out of shape increase apparently. Cutting deepness very hour, what radius of circular arc of point of a knife causes is add be out of shape hold proportion of total cutting metabolic very big. As a result of the dimension effect of cutting force, cutting deepness is so smaller, cutting power is greater (the influence of deepness of the cutting when imperceptible cutting to cutting force shows) 1 times like the graph. Graph the influence of 1 cutting deepness to cutting force cuts ply of thinness the smallest cutting to be when machine tool condition is optimal imperceptibly, use extremely sharp diamond cutting tool to be able to realize the cutting of the successive stability of accept rice class. The ply of the smallest effective cutting of can stable cutting calls ply of the smallest cutting, the physics of the circular arc radius of the ply of the smallest cutting that imperceptible cutting can achieve and point of diamond cutting tool, material that be cut is mechanical function is relevant. Graph if the influence of ply of 2 the smallest cutting to radius of edge circular arc pursues show 2 times, fc of force of cutting of acceptor acceptor of point of point of the A on workpiece reachs his the action of perpendicular force Fd, form F of join forces of join forces F(dissoluble also the way that handles for A dot Xiang Li N and attrition force µN) , the direction of join forces F suffers for A spot place namely stress direction. Nod when A when the included angle W of stress direction and cutting speed direction is 45 ° about (process data to what differ, asks included angle measurement is different also, when machining aluminium alloy with diamond cutting tool, included angle is 38 ° ～ about 45 ° ) , a nods above to be formed to cut bits by treatment material accumulation, and be machined under A dot material classics flexibility, plasticity is out of shape, form treatment surface, the limit that right now A dot is ply of the smallest cutting namely is bit more critical. HDmin of ply of the smallest cutting can pass the limit next type get: In HDmin=r(1-cosq)(1) type: R -- radius of circular arc of cutting blade point by the graph 2 knowable, q+w+b=90 ° , namely Q=90 ° - (in W+b)(2) type: B -- the angle of friction of cutting tool and workpiece material, ) of Tgb=µ(coefficient of friction, the coefficient of friction when using aluminium alloy of cutting of diamond cutting tool is about 0.

12 ～ 0.

26 W -- the included angle of stress direction and cutting speed direction, the intensity of W value and workpiece material, outspread rate, coefficient of friction and the on any account that A chooses the place are concerned, according to ～ of experience W=38 ° 45 ° type (2) generation enters type (1) changes brief: When W=45 ° , type can simplify on for: Watch HDmin value and the ° of W=40 of relation HDminw=38 ° that R is worth µ=0 of ° of W=42 ° W=45.

120.

295r0.

271r0.

246r0.

214rµ=0.

260.

206r0.

158r0.

165r0.

138r by go up form is visible, the limit is the smallest the physics of itself of cutting ply HDmin and R of radius of point circular arc, material is mechanical function and cutting tool, the coefficient of friction between workpiece is concerned. Hdmin value and the relation that R is worth see right table. According to experience, desirable W=42 ° , when µ=0.

12 ～ 0.

26 when, HDmin=(0.

165 ～ 0.

246)r. This shows, if want to realize cutting ply to be the ultrathin cutting of accept rice class, the radius of point circular arc that uses diamond cutting tool right now should be 4 ～ 6nm, this is point radius minimum and very sharp cutting tool. Because the influence of cutting temperature cuts thinness cutting dosage imperceptibly minimum and diamond cutting tool and workpiece material have tall thermal conductivity, accordingly, compare with traditional cutting photograph, the cutting temperature of imperceptible cutting is quite low. But extremely tall to precision exceed imperceptible treatment for, the little change that machines temperature also is to machining the influence of precision cannot of oversight. In the meantime, cutting temperature wears away to cutting tool the impact is bigger, cutting temperature wears away in the chemistry of diamond cutting tool medium effect is very distinct also. Cut those who cut a course to complication imperceptibly dinky cutting deepness (accept rice class) , finite point radius, cutting ply is opposite quality of blade of the low rate at point radius, cutting and happen after a few cutting tool on knife face. 3 are out of shape of the area be out of shape, especially the 3rd be out of shape the cutting tool of the area, the attrition between workpiece and wear away as a result of the cutting tool that be caused by the stretch extensive resume a session of treatment surface, produce heat in metal cutting thereby, the influence machines exterior integrality, cause inferior exterior injury. Lie when cutting ply and point radius same amount class when, the change as a result of the horn before cutting tool (the horn before losing) and of generation slippery brush, the plough phenomenon influence to cutting process also is clearly. Imperceptible cutting machines the technical difficult point that 3 exceed imperceptible cutting to machine basically is to point to pair of spare parts dimension in 1mm precision of the following, treatment is 0.

01 ～ 0.

The treatment of the imperceptible dimension part of 001mm; Exceeding imperceptible treatment is to point to the treatment that exceeds tiny part below in 1µm to dimension; Accept rice class exceeds imperceptible treatment is to point to the treatment that has for the spare parts under 1nm to be being spent imperceptibly. Class of implementation accept rice exceeds imperceptible cutting to machine main existence difficulty of the following technology: The affects data purify process of material minim processability depends on not only cutting cutting tool, at the same time strict also be enslaved to be enslaved to is machined material itself. The choice that exceeds imperceptible cutting to process data is premise with the exterior quality of accept rice class, those who call material " minim processability " (surface roughness of appearance of stage of usable accept rice and right on some treatment distance cutting tool tatty but oversight sex will define) . The interior that the element of processability of influence material minim includes cutting tool of the diamond that be opposite by cutting material adds up to a gender in person (chemical reaction) , the crystal structure of material itself, blemish, distributing and heat treatment condition (if the anisotropy of polycrystal material is right,integrality of surface of spare parts treatment has bigger impact) . Unit cutting muscularity is imperceptible cutting is a kind of paper-thin cutting, cutting ply may be less than the size of grain, the feature of reason cutting force is cutting force tiny, but unit cutting power is very great. Realizing accept rice class to exceed the physical essence of imperceptible treatment is to sever the tie between material element, atom, realize the purify of atom or element, because this cutting force must exceed the element of crystal interior, atomic adhesion. When cutting deepness and feed minimum, the cutting force on unit cutting area will increase quickly, produce very big quantity of heat at the same time, make edge most advanced and local the temperature of area is elevatory, because this is when small fine cutting,ask to cutting tool taller, need to use hardness of wear-resisting, heat-resisting, high temperature intensity of tall, high temperature exceeds material of strong cutting tool well. When the nonferrous metal such as cutting aluminium alloy, the most commonly used is diamond cutting tool. Radius of point circular arc is right the radius of point of limitative cutting tool that exceeds minim cutting ply restricted his ply of the smallest cutting, radius of cutting tool point is smaller, ply of permission the smallest cutting is smaller also. By the watch 1 knowable HDmin=(0.

165 ～ 0.

The crucial point of the diamond cutting tool with current and commonly used 246)r is sharp degree it is R=0 about.

2 ～ 0.

5µm, ply of the smallest cutting can be amounted to 0.

03 ～ 0.

15µm; The cutting tool that grinds through special blade can amount to R=0.

1µm, ply of the smallest cutting can be amounted to 0.

014 ～ 0.

026µm. If need to machine cutting ply to be the workpiece of 1nm, radius of cutting tool point must be less than 5nm, and to this kind of very sharp diamond at present the blade of cutting tool is ground and apply special difficulty. Of cutting tool wear away to exist as a result of diamond cutting tool with damaged small wear away, in cutting after period of time, cutting tool wears away meeting gradually aggravate, can worsen suddenly even sometimes. The invalidation of diamond cutting tool has two kinds of forms: Collapse blade and wear away. The microcosmic cleavage that is in by edge causes the mechanical wear of diamond cutting tool and microcosmic collapse blade, its tatty essence is microcosmic cleavage accumulate. Accumulative diamond cutting tool wears away to basically happen in cutting tool before, hind on knife face, after the cutting length that passes hundreds kilometer, this kind wears away turn into inferior micron class wears away. As a result of oxidation, graphitization, diffuse and the action of carbonization, diamond cutting tool also can produce thermochemistry to wear away. Collapse blade is the stress that goes up when cutting tool point those who exceed diamond cutting tool is local bear happen when force, it is the most difficult forecast and pilot injury, and before be being compared to machining the influence of exterior quality, hind influence of knife face tatty wants big. Reduce cutting temperature to be able to reduce cutting tool effectively to wear away. In addition, undertake in be full of saturated carbon gas cutting also can control the carbonization function of diamond cutting tool. The appearance of form of surface of small oscillatory workpiece in cutting process is the result that goes up to workpiece as a result of the outline map of cutting tool, because this machines exterior surface roughness,reach appearance of cutting tool point to decide by the precision that moves relatively between cutting tool and workpiece. When imperceptible cutting, because cutting deepness often is less than the grain diameter of material, be equivalent to discontinuous to each body undertaking cutting so. This kind microcosmic the in moving characteristic meeting to cause cutting process small vibration of the interrupted cutting that go up and machine tool. The small vibration in imperceptible cutting is right the influence that machines exterior quality also nots allow oversight. Graph V of 3 cutting speed is right the influence of height of the tumour that accumulate bits pursues 4 feed F is right the influence of height of the tumour that accumulate bits accumulates bits tumour when the influence to machining a process exceeds imperceptible cutting, the influence of the tumour that accumulate bits nots allow to ignore. The tumour that accumulate bits affects cutting force and cutting to be out of shape, cold welding still can affect treatment surface surface roughness in the tumour accumulating bits on edge. The microcosmic flaw that eliminates where a thing can be put to best use has immediate effect to accumulating the generation of bits tumour outside, the effect that cutting speed and feed produce to accumulating bits tumour also is clearly. When imperceptible cutting, there is the tumour that accumulate bits to exist inside limits of all cutting speed, but the height that the size of cutting speed accumulates the influence bits tumour: Cutting rate is lower, the tumour that accumulate bits is taller (cutting speed V sees graph 3) to accumulating the influence of bits tumour height; Feed is smaller, the tumour that accumulate bits is taller also (feed F sees graph 4) to accumulating the influence of bits tumour height. 4 measure and method should solve those who exceed imperceptible cutting to machine existence afore-mentioned technical difficulty, add man-hour to should adopt measure of the following technology and method: Reasonable select material exceeds quality of imperceptible treatment surface to rise, should material of logical choice workpiece. The workpiece stuff with choice minim better processability (if be not crystal material or the stuff that have careful grain structure) the workpiece appearance with can get machining exterior integrality better. Reduce radius of point circular arc to exceed accurate cutting to process nonferrous metal and metalloid data with diamond cutting tool, can obtain Ra0.

02 ～ 0.

The lens face of 002µm, what ply amounts to 1nm can be cut to cut bits after abrade cutting tool subtly. What at present the point quality of diamond cutting tool basically relies on to rotating is cast-iron dish go up to undertake to point of diamond cutting tool careful and abrade, polish is obtained, and use ion bundle treatment and chemical polish treatment can make be had by treatment cutting tool inferior the appearance precision of micron class. Use the part before cutting of bevel of bevel angle cutting can increase actual cutting, reduce radius of cutting blade circular arc and limit ply of the smallest cutting, realize ultrathin cutting and imperceptible cutting thereby. When imperceptible cutting, the alternative that the choice of blade dip wants to consider range of brilliant of diamond cutting tool integratedly and blade are ground. Before choosing appropriate cutting tool, hind knife face is natural diamond has hardness tall, wearability intensity of strong, high temperature tall, thermal conductivity is good, as low as the coefficient of friction between nonferrous metal, can grind a series of exceedingly good character such as an extremely sharp the crucial point, accordingly, although natural diamond price is high, but still be cannot replace exceed material of imperceptible cutting cutting tool. Diamond crystal has intense anisotropy, accordingly before diamond cutting tool, hind the brilliant face of knife face chooses to appear particularly important. Use as normally before cutting tool, hind the diamond brilliant face of knife face is (face of brilliant of 1 0 0) and (face of 11 0) brilliant. With coefficient of friction small (face of brilliant of 1 0 0) serves as cutting tool before, hind knife face, can reduce cutting to be out of shape, the attrition between face of the knife after reducing cutting tool and treatment surface and the leftover stress that machine the surface. In the meantime, with (face of brilliant of 1 0 0) serves as cutting tool before, hind knife face, wearability is good, the microcosmic intensity of edge is high, produce microcosmic collapse blade not easily, this is sharp to holding edge degree, prolong cutting tool service life very advantageous. Stable machine tool moves character and treatment environment to want implementation to exceed imperceptible cutting, of logical choice machine tool it is very important also to move character and the stability that maintain treatment environment. Treatment machine tool should provide the minim feed unit of high accuracy, can come true accurate, stable, reliable with fast small displacement; Ask treatment should have the treatment environment that exceeds stability at the same time, in order to make sure treatment process is in strict constant temperature, constant wet, vibration isolation, super- undertake below net requirement, reduce the small vibration effect to treatment surface quality as far as possible. The change that because cutting dosage passes cutting temperature,reduces cutting temperature will affect cutting tool to accumulate bits tumour height, because this use cutting fluid drops cutting temperature,be to restrain the tumour that accumulate bits, reduce cutting tool tatty significant step. 5 epilogue exceed imperceptible cutting is a kind of microcosmic interrupted cutting, unit cutting muscularity, workpiece machines exterior quality to suffer a variety of elements to restrict, cutting treatment process is complex. The relation of ply of the smallest cutting and radius of circular arc of cutting tool point when the article exceeds imperceptible cutting through be opposite undertakes quantifying, the workpiece stuff with put forward to choose minim cutting sex good, use bevel angle cutting, careful abrade cutting tool, reduce radius of circular arc of cutting tool point, choice right diamond brilliant side serves as cutting tool before, hind knife face and reduce the implementation such as cutting temperature to exceed imperceptibly, point out at the same time, the machine tool of high accuracy and the treatment environment that exceed stability also are a when implementation exceeds imperceptible cutting fundamental condition. CNC Milling CNC Machining