Linear feed drive reachs its technology heat

The choice of 1 main transfer machinery is indirect feed drive feedbacks by electric servo drive, mechanical drive and position 3 parts composition, if pursue,2 are shown. Graph the composition of drive of 2 indirect feed is seen from inside the graph, the displacement instruction Xs that cutting tool contrail is generated after the part that needs treatment passes numerical control process designing and decomposes X axis, classics position control, speed control, electric current control and electromotor of servo of the drive after power magnifies, the circumgyrate motion of servo electromotor is changed into sharp movement drive to carry out component part to realize the displacement of a requirement through mechanical main transfer machinery. Detect by measurement unit actual displacement, give the position control error feedback, still have speed feedback and voltaic feedback return in addition, in order to assure working stability of the system. The mechanical main transfer machinery of indirect feed drive basically has: Guide screw nut rack of deputy, gear deputy with worm rack deputy 3 kinds, respective characteristic is shown 3 times like the graph. See from inside the graph, different mechanical main transfer machinery is in the respect such as efficiency of mobile distance, driving force, drive all differs somewhat, suit different operating mode and different machine tool type. The feed that feed drive wants to complete cutting process and the sudden shift when machine tool component locates or changing a knife. According to statistic, in process of machine tool treatment, the time that is used at cutting occupies 35 ％ about, change the auxiliary campaign time such as knife and X/Y/Z axis fixed position to occupy 60 ％ above. The feed speed when cutting accepts craft restriction, general far the function limit under feed drive; Conversely, the distance of sudden shift, speed, acceleration and adding acceleration is the essential factor that reflects performance of trends of feed drive system however. Graph the mechanical main transfer machinery of drive of 3 indirect feed because this, in the circumstance of 50 Mm of quick stroke ＜ , to shorten machine tool component assists time mobily, the scale gain Kv of the acceleration of feed system and controller is most important. In the circumstance of journey of 200 Mm of ＞ of shift of machine tool component, need shift rate is rapid move in order to shorten time, the auxiliary time that saves when acceleration ＞ 10 M/s2 right now does not have too great sense to the time of whole and mobile process, namely the acceleration of prep above 10 M/s2 is not big to overall effect impact, kv value also belongs to secondary. 2.

The elimination with 2 unoccupied place backs has intermediate link as a result of indirect drive, inevitable existence back is unoccupied place between transmission component, because this eliminates a back unoccupied place the key that is design of indirect feed drive to the influence of orbit precision. Nut of ball guide screw deputy although the back is unoccupied place,mix creeping phenomenon is slight, but when high speed and high frequency motion, still cause an effect to precision, because this is in application,meet commonly deputy to ball guide screw undertake be tighteninged beforehand. If the graph is shown 4 times, ball nut divides composition by two, screw to opposite way or among add those who adjust spacer place generation to tighten force to be able to make the axial clearance of guide screw achieves negative worth beforehand, can eliminate a back not simply unoccupied place, deputy tigidity also gets guide screw drive rise, if pursue,4 are shown. But tighten force to cross congress to increase attrition power beforehand, bring about give out heat and wear away quickly. In addition, besides constant outside tightening force beforehand, rise as the rotate speed of nut, ball still can produce corresponding radial active force to guide screw, force is tightened beforehand when bringing about high speed to move too big. Accordingly, nut tightens force to should not be more than ball guide screw beforehand the 12 ％ of the biggest dynamic load, general and desirable 8 ％ of 6 ～ . Graph 4 tighten force to eliminate gear rack drive to carry unoccupied place method on the back to have 2 to the action Nextpage 　 of guide screw ball beforehand. The method is have the aid of the tooth form amlposition of two gear will eliminate a back unoccupied place, if pursue,5 are shown. Installation of two helical gear in the graph is in same servo electromotor on the axis, wheel load of a tine cooperates to install the awl ministry in electromotor axis; Another gear installation is in spline axis place, OK below the action of bedspring axial is mobile, the tooth form amlposition of two helical gear eliminates have the aid of the back of gear and rack drive is unoccupied place. Graph 5 eliminate gear rack drive to carry unoccupied place method on the back the 2nd kind of one method is to use advocate, will eliminate a back from two servo electromotor unoccupied place, its principle is shown 6 times like the graph. Graph 6 eliminate gear rack drive to carry unoccupied place method on the back 19 gear part with two electromotor drive, with its torque coming back differs generation to tighten force to be apart from beforehand, difference takes torque coming back commonly electromotor is highest output 20 ％ ～ 30 ％ . Although increased to control systematic complexity,use two servo motor, but because general power is higher, when fast feed but instead turns with Xiang Xuan, raise speed rate. 2.

3 guide screw disturb prevent ball guide screw to be one long and thin cylinder, rotate in high speed or suffer generation of the meeting below outside force drive to disturb, the first-order natural frequency of guide screw and its stiffness, diameter, impending length, rotate speed is relevant. Its expression is: Among them C is guide screw stiffness, m is its quality, kv is the speed gain of electric machinery. The first-order natural frequency of general ball guide screw is in about 50 ～ 70 Hz, accordingly, the academic speed upper limit of system of feed of ball guide screw is 100 Mm/s. How to increase the first-order natural frequency of guide screw, it is one of crucial points that feed drive system optimizes. 　 of drive of 3 direct feed 3.

The characteristic of drive of 1 direct feed is direct feed drive is support linear electromotor is primary and sub the magnetic force shuttle table between, there is mechanical drive component among, slideway is general like actuating device of ball guide screw. Because do not have the flexibility of axis of guide screw, nut, shaft coupling, electric machinery and bearing, immediate effect is in cutting load and athletic quality on linear electromotor. With photograph of drive of ball guide screw relatively, the acceleration of steep drive is taller, floating rate is rapid, can fast fixed position, servo takes the advantage such as bounty. In addition, because linear electromotor does not have a contact to transfer power, mechanical attrition loss and creeping phenomenon are almost 0, can obtain taller than ball guide screw precision and reliability. According to the tectonic characteristic of linear electromotor, its are first-order natural frequency is decided by the electric character of electromotor only, its expression is: The Kv in type is the speed gain of electromotor, and Kp is positional gain. With technical level is at present computative, the first-order natural frequency of linear electromotor drive is 165 Hz about, far it is than drive of ball guide screw tall. But, the total mass of the acceleration of linear electromotor and motion becomes inverse ratio, become direct ratio with electromotor driving force. Its acceleration is not fall in all circumstances system of nut of excel ball guide screw. For example, the acceleration of the linear electromotor that the ball guide screw that two kinds of lead are 20 Mm and 40 Mm respectively and driving force are 8 KN and 2 KN respectively is like a graph quite 7 are shown. Graph the acceleration of 7 direct drive and indirect drive ability is seen from inside the graph, linear electromotor is in only bear the weight of tall acceleration is achieved when the volume is minor, and drive of ball guide screw maintains his to quicken ability inside big range however, because move,inertial course decelerate is mirrorred to circumgyrate electromotor than ability. 3.

Linear electromotor divides the type of 2 linear electromotor to be mixed for synchronous and linear electromotor the reaction is sharp electromotor two kinds, the stator of induction motor by the metal form, the stator of synchronous electromotor is formed by magnetically hard material. The biggest thrust that commercial synchronous electromotor produces amounts to 15 ～ 20 KN, rated thrust 6 ～ 8 KN, far the biggest thrust that compares induction motor 5 ～ 10 KN, rated thrust 0.

8 ～ 2 KN is tall, apply to the machine tool of heavy cut. And commercial reaction is sharp electromotor because comparing of hold in esteem is tall (small-sized reaction is sharp electromotor weight only 1.

5 Kg) , because this suits relatively medium or small the machine tool of requirement tall acceleration is used. Nextpage 　 　 3.

Tall, inorganic instrument contacts the acceleration that the design of 3 direct drive wants to nod linear electromotor and the delivers component part characteristic intermediate, need to consider systematic rigid dynamics and static stiffness only, but need considers the following impact: (Of 1) linear electromotor calorific bigger, be as high as 100 ℃ even, need water is normally cooling, in order to avoid adverse to generation of machine tool structure effect. (The low frequency mode of machine tool structure may appear when the workbench of 2) heavy-duty machine tool or pillar use direct drive to move below high speed, tall acceleration. This kind of inertial vibration is in by installation the testing system collect on workbench, be not stabilized with respect to what create control system possibly and machine exterior diminution of quality. Because this is medium or small,the machine tool uses direct drive to have larger dominant position. (3) linear electromotor is done not have from locking character, to assure safety in operation, the athletic rod of linear electromotor drive, especially perpendicular movement rod, must want additional deploy deserve to be mixed again locking orgnaization. 3.

Although the cost of drive of 4 linear electromotor is linear electromotor is direct the dynamic function of drive is apparent drive of servo of excel ball guide screw. But compare with drive of ball guide screw, its cost is higher, if pursue,the cost of the plan of two kinds of drive of machine tool of a shunt-wound motion is compared 8 are shown. Graph the cost of 8 direct drive and indirect drive is seen from inside the graph quite, the price of linear electromotor is 3 times of servo electromotor about, although add the mechanical component such as ball guide screw and hinge, the cost of plan of drive of ball guide screw is the 75 ％ of linear electromotor drive only. 　 of heat of a few 4 technologies 4.

1 low tighten force nut structure to use beforehand reduce the method with unoccupied place back closely beforehand, can create the precision of ball guide screw, biggest load and life 3 person contradictory, to prolong the life that tightens force guide screw high beforehand, must make guide screw is falling under full load condition move. Solve the patent technology of this one contradiction, it is in a pair of ball nut is mixed between intermediate spacer, join two stretch gasket, if pursue,9 are shown. Graph among 9 flexibility of washerbed down the livestock after tightening force to deliver the effect to use this technology beforehand, although be in inferior tighten force to fall beforehand, ball still maintains the contact with screw and nut. The test shows as a result, of 3 KN tighten force beforehand can with 5 what have a design already.

5 KN equivalent, the life of ball guide screw but by 0.

4 × 109 turn promotion comes 1.

8 × 109 turn. 4.

The first-order natural frequency of orgnaization of nut of guide screw of ball of device of 2 slideway damp restricted the top speed of feed device. In stiffness, damp, weight 3 decide the parameter of natural frequency is medium, damp is adjusted the most easily through Electromechanical device. Recently the innovation of device of an active damp, can reduce amplitude considerably in place of the first natural frequency. If pursue 10 in green curve place is shown. Graph device of 10 slideway damp the principle of this system is, the unit of apply the brake of slide block of similar and linear slideway adds on workbench, through controlling systematic instruction, use the pottery and porcelain that suppress report to press guide course to increase attrition, the damp that changes feed system is characteristic. Study the result shows, because reduce first-order natural frequency greatly paragraph amplitude, of your feed system highest change to increase to 16 Hz by 8 Hz to frequency. 4.

3 axial are flexible the another way that bearing of ball guide screw raises system of ball guide screw to change to be led to frequency, it is the dynamical character that improves system of ball guide screw through reforming guide screw bearing comes. The improved program that offers at present has passivity and active pattern two kinds. Passive mode is shown 11 times like the graph, it is to will secure bearing to change by rigid material for guide screw is only rigid of 1 ％ flexible material is made, your guide screw but axial is adjustable, change systematic damp. Graph 11 axial are flexible ball guide screw deputy principle is active the working principle of mode is inside carapace of guide screw bearing device presses electric pottery and porcelain, through controlling systematic instruction, make press electric pottery and porcelain to bring to bear on to the ball bearing outer lane of bearing guide screw axial pressure, the damp that changes feed system is characteristic. 5 epilogue and the research heat of a certain number of principles that looked into the article to put forward to design linear feed drive and the essential factor that affect its trends performance and current abroad, design personnel and domestic function component to make a manufacturer consult for the machine tool. Ball guide screw is the form with the widest application of linear feed drive. Be in at present to high speed, reduce noise, quantify cut space, gently, raise DmN value and development of acceleration ability respect. The applied perspective of linear electromotor is wide, but need is reduced further cost and solve calorific problem. Although linear electric machinery is having very large dominant position in speed and acceleration respect, but also have its limitation, at present ball guide screw still enjoys enormous value and technical maturity advantage, because this is right the technical innovation activity of drive of ball guide screw is very brisk still. CNC Milling CNC Machining