Cutting force monitors cutting tool tatty a kind of method

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Of cutting tool of cutting of 1 introductive metal wear away with wear away the precision that condition is affecting machining directly, efficiency and economic benefits, because this cutting tool wears away,the monitoring of condition causes people more and more take seriously. Cutting tool tatty is online monitoring is flexible a of project of production system research main task. Make progress domestic and internationally in the research of this respect in recent years very fast, release with respect to know exactly about sth 10 kinds of methods, what can apply to production however is very few still. Although some methods can be used at actual production, but the very slashing requirement that raises to operating mode because of its however and limitation, popularize application hard. Because cutting force can reflect the dynamic action in machining a process directly, with cutting force consequently signal can monitor status of cutting tool job and wear extent secondhand, cause the attention of people. But already some monitors cutting tool tatty with cutting force signal a lot of method (if all be worth the law that monitor, variance to monitor mould of law, AR,monitor a law to wait) because did not make clear cutting force signal and cutting tool tatty are immanent rule of connection and its change, all have certain one-sided sex and unreliability. In view of this, the article puts forward a kind of cutting tool to wear away from theoretical analysis and experiment the method that monitor, frequency Duan Jun just is worth a law. Analyse related 2 cutting force and cutting tool tatty 1) in the process of cutting of fluctuant and characteristic metal of cutting force, machining complex is put in move or big or little vibration from beginning to end. Cutting tool is opposite the vibration at workpiece, bring about cutting force to produce wave motion subsequently directly. As a result of oscillatory existence, not only cutting area should produce periodic change, and real work angle also should produce cutting tool periodic wave motion. Once cutting force produced wave motion, will counteractive at machining complex, make a system oscillatory be able to restrain or strengthen. Can explain, the fluctuant cycle of cutting force and systematic vibration cycle are identical. 2) cutting tool wears away the influence A of pair of cutting force.

Cutting tool wears away the osculatory way between cutting tool and workpiece was changed after to the after affecting cutting tool knife of static cutting force face happening wears away, turn into by theoretic line contact surface contact. Make so the attrition force of face of the knife after cutting tool and workpiece is increased, penetration of a cutting tool fights force to increase, report is in 3 going up to cutting force direction is 3 all increase to cutting force. And increase of wear extent ceaselessly as cutting tool, attrition will continue aggravate, consequently 3 also will increase ceaselessly to cutting force. This that is to say, static cutting force has the character of wear extent of face of the knife after direct ratio Yu Dao is provided. B.

The discussion before the generation mechanism of force of add and dynamic cutting explains: Actual metallic cutting process always is a dynamic process, cutting force always should produce the wave motion of certain limits. In take no account of circumstance of cutting tool tatty to fall, this fluctuant limits is very big, but if existence of face of the knife after cutting tool wears away (actual cutting tool always is existence tatty) , this fluctuant limits will produce apparent change. The horn after working because of theory of this cutting tool becomes 0 ° , so, the property that angle cycle changes brings about cutting tool cycle to enter state of job of the horn after losing necessarily, produce to hand in consequently change force. Because this is handed in,change force is cutting tool happened to wear away of generation, say this is handed in here change force is force of add and dynamic cutting, next weighing that add momentum. The span that adds dynamic change and angle of cutting tool job is concerned, also concern with wear extent of face of the knife after cutting tool. When cutting tool is in status of job of the horn after losing, face of the knife after cutting tool wants work of partial ground impact, generate interference with workpiece, make workpiece generation is played, plasticity is out of shape, very apparent, the volume of cutting tool section of impact workpiece is larger, the impact power that needs is greater, add dynamic amplitude bigger; Interfere an area conversely smaller, arise add dynamic amplitude smaller. Add dynamic to produce those who increased dynamic cutting power to form, and by afore-mentioned analysises knowable, add motivation to move and cutting tool wear away same metabolic trend, increase as tatty of face of the knife after cutting tool consequently, dynamic cutting force will appear increase a current. The place on put together is narrated, as the accretion of cutting tool wear extent, static cutting force and dynamic cutting force will differ at the same time level land increases. 3) cutting tool wears away to add motivation is a periodic change to hand in to the influence sex of cutting position change force, this is handed in change force is counteractive at machining complex, produce certain effect to systematic vibration, also produce certain effect to cutting position thereby. Popularly is told, adding dynamic change curve is a complex successive change curve, mensurable description is very difficult. Add dynamic action and effect to discuss further, motivation is being added to change suppose here is section linear inside a cycle. Assume the K in adding type of dynamic amplitude Pk=kVB (1) -- scale is invariable; VB -- face of the knife after cutting tool grinds a quantity. The Ls in can be being pushed so that add dynamic change rule to be type -- machining complex vibration grows in the Zhen Wenbo on workpiece; X -- cutting length. Below this kind of circumstance, x of the Δ in the result type that adds dynamical P to be done to systematic place inside a cycle -- systematic vibration amplitude. By type (3) can see: AP is the successive function of VB, reason is in interval (0, a bit VBm exists at least inside Ls) , make AP is in this that is to say interval (0, a dinky value exists surely inside Ls) , put in a dinky value only in fact, drop of this dinky value is VB=VBm, be in (0, sheet of the AP inside VBm) is decreased, and in interval (VBm, ls)AP sheet is added. With optimize a method to be in interval (0, ls) can beg a VBm ≈ 0.

569ls (5) by type (3) can see, adding momentum always is right usually the system does negative work, have damp effect to systematic vibration. But the different interval that in cutting tool wear extent VB changes, action of this kind of damp is having different metabolic tendency. Be in (0, inside VBm) , wear away as cutting tool of VB increase ceaselessly, add dynamic damp action to increase ceaselessly. Be lengthened what as a result of cutting tool wear extent VB itself always lets cutting time ceaselessly and increase, it is so inside this interval, systematic vibration has abate tendency as a result of the damp effect that adds motivation to increase ceaselessly. Define this condition to be position of metastable state cutting, apparent this kind of condition is advantageous to cutting treatment. In interval (VBm, inside Ls) , the metabolic trend of AP produced simple change. As the extension of handling time, add momentum oscillatory to the system damp action is ceaseless and abate, systematic vibration appears heighten a trend. Apparent the stability that this kind of condition machines to cutting is very adverse, use the occasion of hard alloy cutting tool especially. Because add momentum,increase along with the accretion of cutting tool wear extent on one hand, make the condition getting power of cutting tool ceaseless and exasperate; On the other hand systematic vibration increases ceaselessly, the change of cutting area subsequently acuteness, cause cutting tool probably to produce fatigue collapse blade so, call position of this kind of cutting position of cutting of blame stable state. Anyhow, of face of the knife after cutting tool although,wear away inevitable, but in cutting tool tatty inside certain limits, this wear extent is having the effect of stable cutting position however. Exceeded this range, cutting tool enters state of cutting of blame stable state. Should think this is common cutting tool wears away quickly the reason of blade of level happening collapse, reason should avoid cutting tool to enter this kind of state as far as possible. Before square value of 3 frequency Duan Jun and its test result already from theoretic reached such conclusion: ? Shan of widow Nuo poisonous Yao sees the accretion of B of Jun of Wu ニ Yu, the static heft of cutting force and dynamic heft will present big trend. To cutting force signal character, be signal all be worth and variance all increases. But no matter selection signal variance or signal all is worth exist to lose a share as quantity of feature of tatty of the cutting tool that monitor the inadequacy of useful information, mean square value was included at the same time all be worth the information with variance, it is an amount of better the feature that monitor. After undertaking to cutting force signal frequency domain is analysed, discover, in craft parameter choice changeless circumstance falls, structure of cutting signal frequency is very stable, its energy is centered around some chart peak for the most part. Believe comparing of a confusion of voices to rise, undertake taking connecting filter wave to cutting signal, undertake to cutting signal in whole cutting process mean square value is monitored next, measure so that its change trend (frequency of 947 ~ 1 514Hz paragraph) curve of change of value of feed force mean square. Experimental condition: ? T15 of Xi of poisonous Bu herd, kr=57 ° , kr=12 ° , γ =4 ° , α =19 ° , λ S=1 ° ; ~ of working hardness HRC53 55, diametical D=32mm; N=600r/min of main shaft rotate speed, cut deep Ac=1mm, feed F=0.

10mm/r, outside round turning, without cutting fluid. In afore-mentioned experiments, from mean square the value changes the curve is knowable, cutting tool produced collapse blade when 3417min, but in 33.

Value of mean square of the signal when 3min happened namely dash forward add, about dash forward added 2 ~ 3 times. This dash forward add can be opposite as foreboding signal of cutting tool wear away level undertakes monitoring. The foreboding signal that happens before producing collapse blade to cutting tool can become the following explanation. From theoretic analysis knowable, VBm of wear extent of face of the knife after cutting tool is in (0, an optimal VBm exists between Ls) , be in before VBm comes, cutting position is metastable state; Exceeded this value, of stable state of cutting position dispute. Cutting tool produced collapse blade, the likelihood is cutting tool entered state of cutting of blame stable state. In afore-mentioned experiments, can calculate VBm ≈ 0144mm, wear extent of face of the knife after cutting tool of this that is to say exceeded 0144mm, cutting tool entered state of cutting of blame stable state, value of signal mean square happened dash forward add. Thereafter, cutting tool sufferred the acuteness aggravation of power position to bring about collapse blade. 4 epilogue because wear extent of face of the knife after cutting tool the existence of VB, trends appeared to add momentum in cutting process, adding momentum always is right usually the system does negative work, have damp effect to systematic vibration. The static heft of cutting force and dynamic heft all with wear extent of face of the knife after cutting tool VB is concerned. Increase along with VB, the static heft of cutting force and dynamic heft increase at the same time. (VB concerns wear extent of face of the knife after 3) adds property of dynamic damp action and cutting tool. In VB<0.

When 569 1ls because add dynamic damp effect, the system is in position of metastable state cutting. When VB>0.

The system when 569 1ls is in position of blame firm cutting. Hard alloy cutting tool is in wear away quickly when level produces collapse blade, because wear extent of face of the knife after cutting tool exceeded certain limit,the likelihood is, make cutting tool entered state of cutting of blame stable state, add dynamic to increase to enhance joint action with vibration to be provided at the knife ceaselessly ceaselessly, make the condition getting power of cutting tool produced great change be caused by. As wear extent of face of the knife after cutting tool VB increases, the frequency structure of cutting force does not produce change, but distributing to have in the signal energy near the highest peak in a mountain range increase a current, and before blade of collapse of cutting tool happening its energy wants produce a mutation, produced frequency Duan Jun to just be worth a law from this. CNC Milling CNC Machining