Main shaft of the machine tool below high speed condition / metabolic of system of cutting tool connection is finite yuan of analysis
- Time:
- Click:64
Com/magiczoomplus.
Foreword of Css" Type=text/css Rel=stylesheet>1 20 centuries since 80 time, as the comprehensive progress of production technology, high speed / one of main development trends that exceed high speed cutting to already became cutting to machine. Technology of cutting of applied high speed can raise treatment efficiency and treatment precision not only, reduce finished cost, and the treatment requirement of the difficult cutting material such as hard steel of OK and contented temper by dipping in water. The development of high speed processing technique raised new requirement to processing a system. System of treatment of a cutting is main by system of connection of machine tool, cutting tool and cutting tool cutting part 3 parts are formed. According to domestic and international research report, at present high speed, medium high-power, tall rigid machine tool already entered practical phase, razor blade of all sorts of high-powered cutting tool data, cutting already also developed a success in succession, because system of connection of this cutting tool becomes the weakest link in treatment system. When working as a result of system of cutting tool connection, certain clearance exists inevitably between surface of a few connection, because this meeting brings about little vibration of the system, the influence machines precision and treatment surface quality, shorten even cutting tool life, this kind of circumstance when high speed is machined particularly apparent, make machine tool and function of cutting razor blade raise brings benefit to be restricted thereby. Accordingly, accelerate those who study system of cutting tool connection to be out of shape problem, the system of cutting tool connection with development better, more reliable property already made the one ring with at present all in all development of high speed processing technique. Current, the 7:2 that machining center uses generally4 taper connection satisfies the treatment requirement of high accuracy, high-power, high rotate speed very hard. The system of cutting tool connection below effect of 2 centrifugal force 2.
The cutting tool diameter with the problem different basis that system of connection of the cutting tool in treatment of 1 high speed exists, current and general main shaft rotate speed the cutting of above of 10000 ～ 20000r/min regards high speed as cutting. Drive of the main shaft that high speed cutting packs clip and machine tool to cutting tool material, cutting tool, structure, feed and CNC system raised special requirement. After rotate speed achieves certain limits, centrifugal force becomes main load. Below powerful centrifugal force effect, machine tool main shaft and knife handle can happen expand be out of shape, but differ as a result of deflection, make clearance appears between main shaft and knife handle, bring about connection to become loose, the axial position of knife handle is changed, connection stiffness is reduced, affect the dynamic balancing performance of knife handle at the same time. 2.
When 2 centrifugal master piece are out of shape with what fall the circumstance rotates when main shaft high speed, because the radius of main shaft and knife handle and quality are different, because what this suffers,leave mental efforts difference very big. When hollow disc rotates, will happen below centrifugal force effect expand be out of shape, its be out of shape displacement heft set two homocentric disc 1, 2 circle symmetrical axis to rotate with identical angular velocity, when be used by centrifugal master piece, the displacement quantity U1 that R1 of radius of two disc random, R2 is in, U1 is type respectively in: A1, b1 -- it is dish of internal diameter of 1 and external diameter A2 respectively, b2 -- it is dish of internal diameter of 2 and external diameter respectively, and B1=a1 criterion as a result of,the displacement quantity specific value that U1, U2 manages in A1, B2 is A1=b2, b1>a2, because of this ratio [U1 (a1)]/[u2(b2)]>1, fall in aleatoric rotate speed namely, dish the displacement quantity that the displacement volume that 1 internal diameter handles all is more than dish of 2 external diameter to be in, because this is in roll dish 1 with dish 2 won't produce a contact. This shows, the it is certain to cooperate to need interference between main shaft of any system of cutting tool connection and knife handle, in order to assure connection stiffness. Rotate in high speed below the circumstance, measure very hard so that the connection performance when touching receives between knife handle and main shaft through experimental method, because this article is used finite yuan of method (finite yuan of analytic software ANSYS 5.
7) analysis high speed rotates the function of cutting tool connection below condition. Because of main shaft of ISO 40# taper / the flange diameter of knife handle connection and connection of HSK-63A knife handle is approximate and equal, because this chooses these two kinds of connection,undertake contrasting analytic. System of the connection below condition of 3 high speed is out of shape the analysis is in treatment system, the action of system of cutting tool connection is pair of cutting tool fixed position, 2 be cutting tool clamp. The biggest curved moment that because bearing,cutting force brings, the stiffness of system of cutting tool connection is deciding the effective stiffness of whole treatment system greatly. As the development of technology of high speed cutting, come nearly a few years the ISO standard 7:2 that machining center applies generallySystem of 4 taper connection exposes an a lot of inadequacy gradually, and the system of connection of HSK series cutting tool that takes the lead in developing by Germany is receiving promotion application stage by stage at present. 3.
1 7:2System of 4 taper connection is out of shape analytic standard (ANSI B5.
50, ISO 7388, DIN 69871, 69872 wait) 7:24 taper connection is a kind reliable, solid and the connection system with relatively inferior cost. This kind of connection has a lot of advantages, if won't be locked up oneself, what can realize cutting tool is fast assemble and unassemble; Cutting tool is dangerous extend a capacity small, stiffness is taller; Demand of precision of dimension of a cone angle is only higher, the design is simple, production cost is low. But 7:24 taper connection also is put in blemish and inadequacy, basically use awl surface contact only because of its, and did not use the contact with main shaft end panel, such cone must have the effect of two respects at the same time, should make knife handle photograph accurate to main shaft already fixed position, want pair of knife handle clamp again, in order to offer enough connection stiffness. The main shaft below centrifugal force effect and knife handle are out of shape when high speed rotates, main shaft taper hole can use next generation to expand in centrifugal master piece be out of shape. Through using finite yuan of way is right main shaft of taper of ISO 40 # / system of knife handle connection undertakes imitate is analysed, attainable main shaft and knife handle when different rotate speed expand be out of shape circumstance, deflection gives priority to an axis or knife handle uses the radial deflection below in centrifugal master piece, x is the distance that is apart from main shaft end panel, similarly hereinafter) . Analyse a result by imitate knowable, of main shaft and knife handle front expand deflection is more than back end, its are to cause cone angle change as a result, form in main shaft front " horn mouth " . Be out of shape tighten the accretion of force beforehand along with axial to the affects connection system stiffness of radial stiffness and increase, reduce along with the accretion of cone angle error. According to ISO 7388 standard, the grade of taper public errand of knife handle is 13") of ～ of AT α =0 for AT4(angle public errand, the grade of angle public errand of main shaft taper hole is ～ of AT α =0 for AT6(angle public errand - 33") , the point of view that allows namely cooperates an error to be 0 ～ 46" . Angle error is great to the stiffness influence of connection system, although be below the condition that contented standard sets, it is respectively when the error 0 with 46" when, systematic stiffness also differs one times. Appear the reason of afore-mentioned results depends on: When main shaft and knife handle cooperate a state very good (angle error is very small) when, axial tightens force to will form evener osculatory pressure between interface beforehand, make awl surface contact and get all the situation of smooth surface contact of cloth pressure is similar. But when angle when the error is bigger, the osculatory pressure that axial tightens force to be formed between the interface of main shaft and knife handle beforehand is inhomogenous, in the diameter larger part pressure is greater, in the diameter minor part loses a contact possibly even, reduce effective contact length thereby. Accordingly, below centrifugal force effect, of main shaft and knife handle expand be out of shape will form in its front " horn mouth " , make cone angle happening changes, the osculatory state of connection system is exasperate, connection stiffness is reduced. Be out of shape to axial the affects cutting tool axial of fixed position precision repeats fixed position precision to depend on the size of its axial displacement. Below high speed condition, because be left mental efforts action, main shaft and knife handle expand be out of shape, cause the change of position of cutting tool axial finally. The concern of L of displacement of knife handle axial and bottom clearance D can express to be L=dsin θ type in, the cone angle that θ gives priority to axis and knife handle (7:2The cone angle of 4 taper connection is 8 ° 1750") . By go up type is knowable, dinky bottom clearance will make knife handle produces bigger axial displacement between main shaft and knife handle. Accordingly, below the centrifugal force effect of high speed cutting, of main shaft and knife handle be out of shape very will big to machining precision to arise impact. 3.
2HSK connection system is out of shape system of analytic HSK connection is a kind of knife handle that is development of main shaft of high speed machine tool technically by lab of machine tool of German Aachen university / orgnaization of main shaft connection, also be the system of cutting tool connection with the most excellent property that the past develops in ten years. Current, germany already developed HSK(short awl hollow handle) connection means and the systematic technology that have grade balance and main shaft self-poise to cutting tool, can use at turn up the exceeds high speed main shaft and cutting tool connection of 20000 ～ 46000r/min. Watch interference and axial tighten force interference beforehand (µm)7101520 axial tightens force beforehand (KN)4.
756.
7810.
113.
5HSK knife handle and structure of main shaft connection. Knife handle of HSK short awl uses 1:10 taper, its cone compares standard 7:24 awl handle is short, awl handle part uses thin wall structure, taper cooperates interference lesser, the tolerancepublic errand requirement of crucial to knife handle and ministry of main shaft end dimension is stricter. The main shaft below centrifugal force effect and knife handle are out of shape with finite the main shaft to HSK connection and knife handle are in yuan of analysis model to fall from mental efforts action be out of shape the circumstance undertakes finite yuan of imitate analysis, can get be when different rotate speed respectively of main shaft and knife handle expand deflection. Through be opposite knife handle and main shaft are contacted paragraph expand deflection undertakes multinomial plans to close, the dilate that the knife handle when attainable high speed rotates and main shaft issue in centrifugal force effect is out of shape circumstance. Those who pass knife handle and main shaft of pair of taper of standard of ISO 40 # , HSK-63A main shaft, knife handle expand be out of shape the circumstance undertakes comparative, can see: The deflection of main shaft of ISO40# standard taper and knife handle front is bigger than back end deflection much, the clearance between main shaft and knife handle is inhomogenous also, appear " horn mouth " appearance; And knife handle of structure of HSK-63A hollow Bao Bi will arise when high speed rotates bigger expand deflection, can expand in what main shaft makes up for on certain level be out of shape, accordingly the clearance between knife handle and main shaft cone should be less than system of connection of knife handle of 40# standard taper; In addition, the clearance after HSK-63A main shaft and knife handle are out of shape distributings the clearance after wanting to compare system of connection of 40# standard taper to be out of shape is gotten equably much, before its, the gap amount of back end differs very small, just appeared in the middle of connection bigger gap, but its deviation does not exceed 16% . Accordingly, of knife handle of structure of HSK-63A hollow Bao Bi expand be out of shape the characteristic is helpful for make up for the clearance between its and main shaft through interference. The public errand of dimension of HSK connection knife handle that interference and axial tighten force DIN standard to give out beforehand. The interference that is in in D1 and public errand are 10µm and ± 4µm respectively. A of HSK connection system important characteristic was to realize main shaft end panel and cone to contact fixed position at the same time. Below high speed condition, clearance can appear likewise between its main shaft and knife handle cone. The basis is finite yuan of analysis result, when main shaft rotate speed achieves 30000r/min, the gap amount between knife handle and main shaft taper hole achieves 5 ～ 6µm, to make up for this one clearance, the interference talent that needs to have 11 ～ 12µm realizes end panel and cone to contact fixed position at the same time. On the other hand, below so big interference, be in a static state when main shaft or when rotate speed is inferior, need is very big tighten power ability to realize the contact between main shaft end panel and knife handle flange to locate beforehand. Pass finite yuan of imitate analysis, attainable the axial that maintains main shaft and place of contact of knife handle end panel to need when different interference tightens force beforehand (see on watch) . The basis is finite yuan of imitate analysis result, to get used to the requirement that high speed cutting machines, the interference of HSK-63A connection system should be 15 ～ 20µm; To assure to contact the constant osculatory pressure between end panel, recommend adoption axial to tighten force to be 15 ～ 20kN beforehand. System of connection of knife handle of 4 conclusion HSK uses end panel and cone to contact orientation way and structure of hollow knife handle at the same time, have connection stiffness tall, axial and radial repeat fixed position precision dimension of tall, system small, weight light, structure is compact wait for a characteristic. With traditional 7:2Photograph of connection of 4 standards taper is compared, HSK connection system more apply to high speed treatment. The connection of knife handle and main shaft needs certain interference. The interference that sets in DIN standard slants small, the interference of HSK-63A connection system should be 15µm, here interference falls, contact fixed position at the same time to assure to the cone of knife handle and main shaft and end panel come true when low speed, what need tighten thrust Jian value to be 15 ～ 20kN beforehand. CNC Milling