CN107649890A - One kind is based on high-precision spiral master gear and worm geared precision indexing turntable and assembly method - Google Patents

Abstract

The invention belongs to the technical field of precision machining and testing, and proposes a precision indexing turntable and assembly method based on high-precision helical standard gear and worm drive, which adopts open-loop control and high-precision harmonic motor drive and a worm with self-locking function and Helical gear helical angle meshing transmission; the tension spring anti-backlash mechanism is used to eliminate the backlash between the worm and the helical standard gear, reducing the reverse empty stroke error of the indexing table; the indexing table adopts radial reference and high-precision dense ball shafting The structure and the homogenization effect of the error can make the radial comprehensive error of the indexing table less than 0.5μm; the axial reference adopts a plastic-coated sliding bearing structure, which has high rigidity and vibration absorption. The indexing accuracy of the well-assembled indexing table can reach below 10". The invention can realize intermittent indexing or continuous indexing at any angle, and has the advantages of simple structure, high indexing accuracy, high structural rigidity, stable indexing accuracy, With the advantage of low cost, it can be used in light-load precision machining and testing occasions.

Description

One kind based on high-precision spiral master gear and worm geared precision indexing turntable and Assembly method

Technical field

The invention belongs to Precision Machining and technical field of measurement and test, is related to a kind of processing and test for precision indexing element Index table.

Background technology

Index table is machining and a very important device in testing field, and its core indexing component mainly has The several types such as worm and gear, rack-and-pinion, sheave, index dial, end-toothed disc and direct driving motor.Wherein, end tooth indexing means Indexing accuracy highest, typically can reach 0.5 ", can reach 0.1 "；Next to that indexing disc type indexing means, highest indexing essence For degree up to 5 "~10 ", general indexing accuracy is 10 "~30 ".But this two classes indexing component uses opened loop control, indexing essence more Degree depends entirely on the indexing accuracy of indexing component itself, and can not realize continuous division at any angle.It is straight to drive indexing mode It is a kind of high-accuracy high-efficiency indexing mode to grow up in recent years, it eliminates mechanical dividing element, utilizes closed-loop control Technology realizes the direct Continuous Drive of torque motor, and indexing accuracy may be up to 5 "~15 ", however use the indexing mode into This is higher, and indexing stability is also high without the precision of mechanical dividing device.

The control form of high-precision dividing apparatus has open loop and closed-loop and semiclosed loop three types, steady from cost and indexing Qualitatively said in angle, opened loop control cost is relatively low, and indexing stability is preferable；Closed-loop control cost is higher, indexes stability one As；Half-closed loop control falls between.

Vibration and noise are small, excellent with auto-lock function etc. greatly, in transmission process with single staged transmission ratio for Worm Wheel System Point, extensively using in the indexing system in being equipped with machine-building.In open-loop control system, the indexing essence of Worm Wheel System Degree depends primarily on the machining accuracy of worm and gear, and manufacturing cost is relatively low, and indexing accuracy is typically 1 '~3 '；In closed-loop control In system, the indexing accuracy of Worm Wheel System depends primarily on machining accuracy and the feedback detection grating encoding of worm and gear The indexing accuracy of device, indexing accuracy can be to 30 "~1 ' then manufacturing cost it is higher.

Because the manufacturing cost of worm gear is higher, and the highest accuracy of manufacture is 3 grades.Therefore, it is less demanding in indexing accuracy Occasion under commonly use helical gear and replace worm gear, transmission is engaged using worm screw and helical gear.Such as vehicle shift is held Row mechanism (ZL 2010202211182.4), vehicular clutch executing agency (ZL 2010202211169.9), car light, which turn to, to be driven Dynamic device (ZL 201120094520.5), vehicle steering shaft control (ZL 201320170000.7) and manual window opening machine (ZL 20152100426.0) etc., the helical gear and worm screw for employing low cost are driven.Because helical gear and worm screw pass It is point contact during dynamic, therefore the kind of drive of the type is not suitable for the occasion of heavy duty；In addition, the biography of worm screw and helical gear Dynamic precision depends primarily on the machining accuracy of helical gear, to improve its indexing accuracy, need to use high-class helical tooth Wheel.

The content of the invention

To solve the problems, such as that existing indexing means cost performance is not high, the invention provides one kind to be based on high-precision spiral standard Gear and worm geared precision indexing turntable,

Concrete technical scheme is：One kind is based on high-precision spiral master gear and worm geared precision indexing turntable, wraps Include circular table, dust cover, stiffening ring, circular dividing table base, spiral master gear, pressure ring, protecting cover, close pearl axle sleeve A, mandrel, axle Bearing, close pearl axle sleeve B, plastic sheet, support base, worm screw, Triangulum vertical shaft, close pearl axle sleeve C, worm screw case, small track base, flat close pearl Plate, handle, compensation ring, ring flange, yielding coupling, clutch seat, adapter sleeve, flange shaft, spring adjusting screw, vertical bearing, drawing Spring, spring base, eccentric shaft, knob, knob bearing, harmonic motor；

Plane is circumferentially provided with symmetrical T-slot and uniform workpiece connection screw thread hole on circular table, for workpiece or The connection of fixture；The flatness of plane is less than 2 μm on circular table, and the end face beat after assembling is not more than 5 μm；Under circular table Face is provided with raised annulus end face, uniform screwed hole on end face, is the installation locating surface of master gear, for spiral master gear Fixation；The flatness error of circular table lower surface is less than 1 μm, is less than 2 μm with the parallelism error in upper table face；Sired results Make the annular groove for 2~3mm that platform bottom surface has width to be more than dust cover wall thickness, labyrinth seal is formed with dust cover top structure；Sired results Make to be additionally provided with oil filler point on platform, be easy to the lubricating oil of filling lubrication worm screw and spiral master gear；

Dust cover is rolled from 1~2mm steel plate and formed, and bottom is welded and fixed with stiffening ring, and is led to circular dividing table base Cross bolt connection；Dust cover and stiffening ring junction stay a breach to prevent from interfering with worm screw case；

Big angle is fallen in the generally square sheet material of circular dividing table base, corner, is cast and processed using cast iron materials；Upper table Facial plane degree error is less than 3 μm, is machined with for connecting mandrel, support base, Triangulum vertical shaft, vertical bearing, knob bearing, dust-proof The screwed hole of the parts such as cover stiffening ring；Its bottom surface uses closed-in construction, and the annulus of circumferential side frame and intermediate projections is coplanar, flatness Error is less than 5 μm, is less than 5 μm with the parallelism error in upper table face；Uniform four are provided among bottom surface frame and annulus Reinforcement, for improving the rigidity of structure of circular dividing table base；

The helical angle of spiral master gear is equal to the lead angle of worm screw, transverse module m_t=0.5~1mm, due to spiral shell The contact area for revolving gear with worm screw is the point contact on a certain section, therefore in the condition for ensureing the helical gear rigidity of structure Under, the facewidth is the smaller the better；The indexing accuracy of the circular dividing table depends primarily on the tooth pitch precision of spiral master gear, according to using field Close, the tooth pitch precision of spiral master gear is more than 3 grades precision (GB/T 10095.1-2008)；Spiral master gear is axially fixed Position reference plane is not more than 2 μm relative to the end face beat of interior axially bored line；Spiral master gear is fixed on circular table by pressure ring On；The coaxiality of inner hole error of the endoporus and bearing block that assemble rear screw master gear is not more than 1 μm, the rotation of spiral master gear The parallelism error for turning the relatively former work top of locating surface is not more than 2 μm；

Support base is bowl shaped structure, and upper ring surface is axially mounted locating surface, and bears circular table, bearing block, close pearl axle Cover A, spiral standard and to be processed or test tool part weight；Lower anchor ring is determined for the installation of support base and circular dividing table base Plane, the respective flatness error of two anchor rings are not more than 2 μm, and parallelism error is not more than 2 μm；An annular groove is set among upper ring surface, For storing lubricant grease, laminating tablet, and being handled by scraping thereon；Support base after laminating plays the work of sliding bearing With；

Mandrel includes a bottom surface and two shaft part compositions；Upper shaft part is the radial reference of index table, and circularity is less than 0.5 μm, for cylindricity less than 1 μm, the error of perpendicularity of axis and bottom surface is less than 2 μm；The shaft part passes through close pearl axle sleeve A and close pearl axle sleeve B Coordinate respectively with bearing block and spiral master gear；The spherical rolling body of G5 levels above precision selected by close pearl axle sleeve and axle and hole The unilateral magnitude of interference be 0~3 μm；It is radially installed base of the mandrel relative to circular dividing table base that lower shaft end cylindricity, which is no more than 3 μm, Standard, coordinate with circular dividing table base mandrel positioning hole for gap；

Triangle vertical shaft is connected on base, its axis passes through close pearl axle sleeve C connecting worm casees one end, worm screw perpendicular to base Case is with respect to triangle vertical shaft rotating；The worm screw case other end is connected with adapter sleeve, and its underrun is put down close pearl plate and is fixed on base Small track base coordinate, formed a sliding bearing；Adapter sleeve is connected with spring base close to the side of helical gear, in vertical bearing Extension spring is provided between spring base, for worm screw case to be pulled into spiral master gear, to eliminate the worm screw in worm screw case with tiltedly Radial clearance between gear；Spring adjusting screw passes through vertical bearing to be connected with extension spring, adjustable by adjusting spring adjusting screw Save the pressure between worm screw and spiral master gear；Adapter sleeve opposite side is connected with clutch seat, and its endoporus is matched somebody with somebody with eccentric shaft clearance Close；Handle is connected by knob with the interference of eccentric shaft upper end, facilitates the manual actuation of eccentric shaft, to realize worm screw and helical gear Quick separating；

Worm screw is connected in worm screw case by angular contact ball bearing；The order of connection is by inner and outer be respectively：Angular contact ball axle Hold A, worm screw, angular contact ball bearing B, compensation ring, ring flange, yielding coupling, flange shaft harmonic motor.

Further, above-mentioned bearing block and mandrel use GCr15 materials, and are not less than using quenching subzero treatment, hardness HRC58；Spiral master gear is using 40Cr materials and using quenching subzero treatment, hardness HRC45~50；Worm screw uses 38CrMoAlA tool steel materials, surfaces nitrided processing, more than hardness HV830.

The above-mentioned assembly method based on high-precision spiral master gear and worm geared precision indexing turntable, including it is as follows Step：

Step 1, mandrel is connected by screw on circular dividing table base；

The upper reference plane of the datum clamp face of mandrel and circular dividing table base is cleaned up, then applies one layer of lubricating oil；With Circular dividing table base is installed on the basis of the shaft part of mandrel；The countersunk head screwed hole connection suspension ring of circular dividing table base corner, for circular dividing table Carrying；

Step 2, support base is installed on circular dividing table base；

Using the axis of mandrel as radial reference, the upper reference plane for being circular dividing table base is axial benchmark installation village support base； Laminating scraping processing is carried out to reference plane on support base before installation, laminating material thickness is 0.707~1mm；Surveyed before and after laminating The parallelism error that reference plane on support base installs positioning reference plane relative to support seat is measured, has ensured that polytetrafluoroethylplastic plastic piece The uniformity of thickness, so that it is guaranteed that the precision and rigidity of the device axial direction reference for installation；

Step 3, spiral master gear and bearing block are installed on circular division platform；

First by spiral master gear by pressure ring and mode connects for screw to circle platform, and adjust spiral master gear endoporus Axis overlaps with circular table external cylindrical surface axis, then successively loads close pearl axle sleeve B, bearing block and close pearl axle sleeve A；With support Reference plane is axial benchmark on seat, rotates circular table as radial reference using mandrel and close pearl axle sleeve B, progressively will in rotation process The attachment screw of bearing block is tightened by diagonal order, thus ensure that bearing block and spiral master gear endoporus to greatest extent Axiality；Finally circular table UNICOM bearing block, spiral master gear and pressure ring are removed together, together to the axle after assembling The endoporus attrition process of bearing endoporus and spiral master gear；

Step 4, worm screw and anti-backlash mechanism are installed；

Triangulum vertical shaft, vertical bearing, knob bearing and small track base are connected by screw on circular dividing table base first, And the guardrail of close pearl plate stroke is put down in connection limitation on small track base, and then flat close pearl plate is put into guardrail；Then by worm screw Shafting loads in worm screw case；Erection sequence is angular contact ball bearing, worm screw, angular contact ball bearing, compensation ring, ring flange, elasticity Shaft coupling, flange shaft harmonic motor；According to fit-up gap by grind adjust compensation ring thickness, with eliminate worm screw relative to Worm screw case axial gap；Adapter sleeve is connected together by screw with worm screw case, and harmonic motor passes through screw and adapter sleeve Connect together；Then installation installation spring base and clutch seat on adapter sleeve；

Then the worm screw case with after is connected on Triangulum vertical shaft by close pearl axle sleeve C, adapter sleeve is put into flat close pearl plate On；One end of extension spring is connected on spring base, the other end is connected on spring adjusting screw, is grown by the work for adjusting extension spring Degree, the radial pressure of adjustment worm screw and spiral master gear is after 0.3~1kgf, adjustment with nut by spring adjusting screw Fixed on vertical bearing；Eccentric shaft, knob and handle are finally connected, is manually operated, worm screw is departed from and spiral full-height tooth The engagement of wheel, realize the quick index of circular dividing table；

Step 5, the installation of dust cover and platform

Together with being spoted weld first by dust cover with stiffening ring, it is then fitted on circular dividing table base；Then rotational handle, make Worm screw disengaging is engaged with spiral master gear；Then by all close pearl axle sleeve ball room spaces, in the oil storage tank of support base, spiral shell Revolve the lubricating grease that low viscosity is filled in the teeth groove of master gear and in the helicla flute of worm screw；Then by close pearl axle sleeve B and connection spiral shell The circular table for revolving master gear and bearing block loads on mandrel, is finally gently pressed into close pearl axle sleeve A in mandrel and bearing block Between, untill the flange on close pearl axle sleeve A is snapped on bearing block.

The beneficial effects of the present invention are, propose it is a kind of using high-precision spiral master gear replace worm gear realize worm screw and The precision round subsection turntable of spiral standard engaged transmission, driven using opened loop control and high-precision harmonic motor；The worm screw of design Be less than Self-locking angle with helical gear helical angle, therefore the device has auto-lock function, using extension spring anti-backlash mechanism eliminate worm screw and Back clearance between spiral master gear, reduce the reverse idle stroke error of circular dividing table；Circular dividing table radial reference uses high precision dense bead Shafting structure, the leveling effect of error can make the radial composite error of circular dividing table be less than 0.5 μm, and axial benchmark uses laminating cunning Moving axis bearing structure, there is high rigidity and absorbing to act on.The indexing accuracy of the superior circular dividing table is assembled up to 10 " it is following, meet General Precision Machining and the indexing demand of test.Precise indexing table provided by the invention can realize interrupted division at any angle or Continuous division, there is the advantages of simple in construction, indexing accuracy is high, the rigidity of structure is high, indexing accuracy is stable, cost is low, can be used for The Precision Machining of underloading and test occasion, have good market application foreground.

Brief description of the drawings

Fig. 1 index table sectional views.

Fig. 2 circular tables (on).

Fig. 3 circular tables (under).

Fig. 4 circular dividing tables base (on).

Fig. 5 circular dividing tables base (under).

The installation of Fig. 6 helical gears and circular table.

Fig. 7 support bases.

Fig. 8 anti-backlash mechanisms.

Fig. 9 worm screw shaftings.

Figure 10 device internal structures

Figure 11 general assembly drawings.

In figure：1 circular table；1-1T type grooves；1-2 workpiece connection screw thread holes；1-3 bearing block connection screw thread holes；1-4 oilings Hole；1-5 bearing block mounting flanges；1-6 master gear datum clamp faces；1-7 master gears install locating surface；1-8 annular grooves；2 is anti- Dust hood；3 stiffening rings；4 circular dividing table bases；4-1 countersunk head screwed holes；4-2 mandrel positioning holes；4-3 connection screw thread holes；4-4 reinforcements； 4-5 installs locating surface；5 spiral master gears；6 pressure rings；7 protecting covers；8 close pearl axle sleeve A；9 mandrels；10 bearing blocks；11 close pearl axle sleeves B；12 plastic sheets；13 support bases；13-1 oil storage tanks；13-2 mounting holes；The upper reference planes of 13-3；13-4 support base datum clamp faces； 14 worm screws；15 Triangulum vertical shafts；16 close pearl axle sleeve C；17 worm screw casees；18 small track bases；19 flat close pearl plates；20 handles；21 compensation Ring；22 ring flanges；23 yielding couplings；24 clutch seats；25 adapter sleeves；26 flange shafts；27 spring adjusting screws；28 vertical bearings； 29 extension springs；30 spring bases；31 eccentric shafts；32 knobs；33 knob bearings；34 harmonic motors.

Embodiment

(1) measure of rotary axis system precision is improved

Influence of the precision of rotary axis system to circular dividing table indexing accuracy is most important.Machining accuracy, dress from vital part Choice accuracy with spherical rolling body used in precision and close pearl axle sleeve ensures that circular dividing table is no more than the measure of 0.5 μm of radial error Have：

(1) machining accuracy of mandrel 9 is improved.The precision of positioning including mandrel 9 is with being used as circular dividing table radial reference shaft part Machining accuracy.The shaft part, the part especially contacted with the spherical rolling body in close pearl axle sleeve A and B, deviation from circular from are less than 0.5 μm, deviation from cylindrical form is less than 1 μm, and the error of perpendicularity of the axis of the shaft part and the positioning reference plane of mandrel 9 is less than 2 μm.Together The flatness of reference plane, ensures said reference by attrition process above and below Shi Tigao mandrels positioning reference plane, index table base The flatness in face is no more than 2 μm.

(2) machining accuracy and peace for the endoporus of the spiral master gear 5 and endoporus of bearing block 10 being connected with circular table 1 are improved Fill axiality.Endoporus and the diameter of bore of bearing block 10 difference of spiral master gear 5 are not more than 2 μm, and deviation from cylindrical form is not more than 1 μ M, the coaxiality error after assembling are not more than 1 μm.By first assembling, the method for rear integral grinding ensures above-mentioned precision index.

(2) assembling of index table

(1) mandrel 9 is connected by screw on circular dividing table base 4 first.By the datum clamp face and circular dividing table of mandrel 9 The upper reference plane of base 4 cleans up, and a thin layer of lubricating oil is then applied, in addition to antirust function, moreover it is possible to increase faying face Compatibility；Circular dividing table base 4 is installed on the basis of the shaft part of mandrel 9；The countersunk head screwed hole 4-1 connections of circular dividing table base corner Suspension ring, the carrying for circular dividing table.

(2) and then by support base 13 it is installed on circular dividing table base 4.It is circular dividing table using the axis of mandrel 4 as radial reference The upper reference plane of base 4 is that axial benchmark installs village support base 13.Reference plane on support base is carried out at laminating scraping before installation Reason, laminating material is polytetrafluoroethylplastic plastic piece 12, and thickness selects 0.707mm or 1mm specifications.Measurement support is intended to before and after laminating Reference plane 13-3 installs positioning reference plane 13-4 parallelism error relative to support seat on seat, has ensured that polytetrafluoroethylplastic plastic The uniformity of the thickness of piece 12, so that it is guaranteed that the precision and rigidity of the device axial direction reference for installation.

(3) spiral master gear 5 and bearing block 10 are installed on circular division platform 1 again.Spiral master gear is led to first Pressure ring 6 and mode connects for screw are crossed to circle platform 1, and adjusts axially bored line and the external cylindrical surface axle of circular table 2 in spiral master gear 5 Line overlaps, and then successively loads close pearl axle sleeve B11, bearing block 10 and close pearl axle sleeve A8.Using reference plane 13-3 on support base as axle To benchmark, using mandrel 9 and close pearl axle sleeve B11 as radial reference rotation circular table 1, progressively by the company of bearing block in rotation process Connect screw to tighten by diagonal order, thus ensure that the axiality of bearing block 5 and spiral master gear endoporus to greatest extent. Finally the UNICOM's bearing block 10 of circular table 1, spiral master gear 5 and pressure ring 6 are removed together, together to the bearing block after assembling The endoporus attrition process of endoporus and spiral master gear.

(4) worm screw and anti-backlash mechanism are installed

Triangulum vertical shaft 15, vertical bearing 28, bearing 33 and small track base 18 are connected by screw circular dividing table bottom first On seat 4, and the guardrail of the close stroke of pearl plate 19 is put down in connection limitation on small track base, and then flat close pearl plate 19 is put into guardrail.

Then worm screw shafting is loaded in worm screw case 17.Erection sequence is angular contact ball bearing 1, worm screw 14, angular contact ball Bearing 2, compensation ring 21, ring flange 22, yielding coupling 23, the harmonic motor 34 of flange shaft 26.According to fit-up gap by grinding Mill regulation compensation ring thickness, with eliminate worm screw 14 relative to worm screw case 17 axial gap.Adapter sleeve 25 by screw with Worm screw case 18 is connected together, and harmonic motor 34 is connected together by screw with adapter sleeve；Then installed on adapter sleeve 25 Spring base 30 and clutch seat 24 are installed.

Then the worm screw case with after is connected on Triangulum vertical shaft 15 by close pearl axle sleeve C16, adapter sleeve 25 is put into flat On close pearl plate 16；One end of extension spring 29 is connected on spring base 30, the other end is connected on spring adjusting screw 27, passes through tune The active length of whole extension spring, adjustment worm screw and the radial pressure of spiral master gear use nut after 0.3~1kgf, adjustment Spring adjusting screw is fixed on vertical bearing 28.

Eccentric shaft 31, knob 32 and handle 20 are finally connected, is manually operated, worm screw 14 can be made to depart from and spiral standard The engagement of gear 5, realize the quick index of circular dividing table.

(5) installation of dust cover and platform

Together with being spoted weld first by dust cover 2 with stiffening ring 3, it is then fitted on circular dividing table base 4；Then rotational handle 20, depart from worm screw and engaged with spiral master gear；Then by all close pearl axle sleeve ball room spaces, the oil storage tank of support base The lubricating grease of low viscosity is filled in interior, spiral master gear teeth groove and in the helicla flute of worm screw；Then by close pearl axle sleeve B11 and The circular table for connecting spiral master gear 5 and bearing block 10 loads on mandrel 9, and close pearl axle sleeve A8 is gently finally pressed into mandrel 9 and bearing block 10 among, untill the flange on close pearl axle sleeve A8 is snapped on bearing block 10.

(3) operation of index table

(1) running-in

Because circular dividing table worm screw provided by the invention and spiral master gear instantaneous touch state contact for point, and by humorous Ripple slows down and worm and helical gear double reduction, slows down bigger, and occasion is indexed suitable for low speed rotation.In order to improve worm screw and spiral shell The contact condition of master gear is revolved, needs to carry out running-in to the device before use.After running-in, worm screw and spiral master gear Instantaneous Multi-contact state, instantaneous multiple cell domain face contact can be become, so as to improve worm screw and spiral master gear Contact stiffness.

(2) angular indexing is determined manually

The gearratio optional 120 of the speed reducing ratio of harmonic gear optional 30~50, worm screw and spiral master gear~ 180, the synthesis speed reducing ratio of the device is up to 3600~9000；By taking rotating speed 6000rpm motors as an example, the index table turns Speed is 4 °~10 °/s, therefore index table provided by the invention is low speed turntable, it is impossible to realizes circular dividing table using motor driving Quick index.The quick index of circular dividing table is realized, by the eccentric rotation axis 21 of handle 20, drives worm screw case 17 to be stood around Triangulum Axle 15 rotates, and departs from worm screw 14 and is completely disengaged with spiral master gear 5, after hand rotation circular dividing table to special angle, Handle 20 is moved, worm screw case 17 turns round in the presence of extension spring 29 around Triangulum vertical shaft 15, and worm screw 14 enters and presses spiral mark In the teeth groove of quasi- gear 5, so as to realize the quick index of circular dividing table.Using the circular dividing table, 1/z (wherein z can be achieved in indexing manually Determine angular indexing for the number of teeth integral multiple of spiral master gear；It is " following that indexing accuracy is up to 10.

(2) it is continuous automatic or determine angular indexing

Because the indexing means that the invention provides has auto-lock function, therefore it is any that servomotor driving can be utilized to realize Angle determines angle or continuous division, and indexing accuracy is up to 10 "~30 ".

Claims (3)

1. A precision indexing turntable based on high-precision helical standard gears and worm drive, characterized in that it comprises a circular table (1), a dust cover (2), a rigid ring (3), an indexing table base (4 ), spiral standard gear (5), pressure ring (6), cover (7), dense bead bushing A (8), mandrel (9), bearing seat (10), dense bead bushing B (11) , plastic sheet (12), support seat (13), worm screw (14), triangular seat vertical shaft (15), dense bead bushing C (16), worm box (17), small guide rail seat (18), flat dense bead Plate (19), handle (20), compensation ring (21), flange (22), elastic coupling (23), clutch seat (24), connecting sleeve (25), flange shaft (26), Spring adjustment screw (27), vertical support (28), extension spring (29), spring seat (30), eccentric shaft (31), knob (32), knob support (33), harmonic motor (34) ; The upper plane of the circular workbench is provided with symmetrical T-shaped slots (1-1) and evenly distributed workpiece connection threaded holes (1-2) along the circumference; the flatness of the upper plane of the circular workbench is less than 2 μm, and the deflection No more than 5μm; there is a raised circular ring end surface under the circular worktable, and the threaded holes are evenly distributed on the end surface, which is the installation positioning surface (1-7) of the standard gear; the flatness error of the lower end surface of the circular worktable is less than 1μm, which is consistent with The parallelism error of the upper worktable is less than 2 μm; the bottom of the round worktable has ring grooves (1-8) with a width greater than the wall thickness of the dust cover (1-8), which form a labyrinth seal with the top structure of the dust cover; There are oil injection holes (1-4); The lower part of the dust cover is welded and fixed with the rigid ring, and is connected with the base of the indexing table (4) by bolts; a gap is left at the connection between the dust cover and the rigid ring to prevent interference with the worm box; The flatness error of the upper working table of the base of the indexing table is less than 3 μm, the bottom surface adopts a frame structure, the surrounding frame and the raised ring in the middle are coplanar, the flatness error is less than 5 μm, and the parallelism error with the upper working table is less than 5 μm; The helix angle of the helical standard gear (5) is equal to the thread lead angle of the worm, and the modulus of the end surface is m _t = 0.5 ~ 1mm. The pitch accuracy of the helical standard gear is above grade 3; The end surface deflection of the axis is not greater than 2 μm; the spiral standard gear is fixed on the circular worktable through the pressure ring (6); after assembly, the coaxiality error of the inner hole of the spiral standard gear and the inner hole of the bearing seat is not greater than 1 μm, and the spiral standard gear The parallelism error of the rotating positioning surface relative to the original worktable is not more than 2 μm; The support seat (13) is a bowl-shaped structure, the upper ring surface is the axial installation positioning surface; the lower ring surface is the installation positioning surface of the support seat and the indexing table base, the respective flatness errors of the two ring surfaces are not greater than 2 μm, and the parallelism The error is not greater than 2μm; there is a ring groove in the middle of the upper ring surface, which is used to store lubricating grease, and a plastic sheet is pasted on it, and the support seat after the plastic paste plays the role of a sliding bearing; The mandrel consists of a bottom surface and two shaft sections; the upper shaft section is the radial reference of the indexing turntable, the roundness is less than 0.5 μm, the cylindricity is less than 1 μm, and the perpendicularity error between the axis and the bottom surface is less than 2 μm; The bead bushing A (8) and the dense bead bushing B (11) are matched with the bearing housing (10) and the spiral standard gear respectively; the dense bead bushing adopts the spherical rolling body with the precision above G5 level and the single side of the shaft and the hole. The interference amount is 0~3μm; the cylindricity of the lower shaft end does not exceed 3μm, which is the radial installation reference of the mandrel relative to the base of the indexing table, and it is a clearance fit with the positioning hole of the mandrel of the base of the indexing table; The base is connected with a triangular vertical shaft (15), whose axis is perpendicular to the base, and one end of the worm case (17) is connected through a dense bead sleeve C (16), and the worm case rotates relative to the triangular vertical shaft; the other end of the worm case is connected with the connecting sleeve (25) , the bottom surface of which is matched with the small guide rail seat (18) fixed on the base through the flat dense bead plate (19) to form a sliding bearing; the side of the connecting sleeve close to the helical gear is connected with a spring seat (30), on the vertical support A tension spring (29) is arranged between (28) and the spring seat (30); the spring adjustment screw (27) passes through the vertical support and is connected with the tension spring; the other side of the coupling sleeve is connected with a clutch seat (24), and The hole and the eccentric shaft (31) are in clearance fit; the handle (20) is in interference connection with the upper end of the eccentric shaft through the knob (32); The worm (14) is connected in the worm box through an angular contact ball bearing; the connection sequence from the inside to the outside is: angular contact ball bearing A, worm, angular contact ball bearing B, compensation ring (21), flange (22) , elastic shaft coupling (23), flange shaft (26) and harmonic motor (34). 2. A precision indexing turntable based on high-precision helical standard gear and worm drive according to claim 1, characterized in that the bearing seat and mandrel are made of GCr15 material, and quenched and cryogenically treated, the hardness is not lower than HRC58 ;The spiral standard gear is made of 40Cr material and quenched and cryogenically treated, with a hardness of HRC45~50; the worm is made of 38CrMoAlA tool steel material, the surface is nitrided, and the hardness is above HV830. 3. the assembly method of the precision indexing turntable based on high-precision spiral standard gear and worm drive according to claim 1 or 2, is characterized in that, comprises the steps: Step 1, connect the mandrel to the base of the indexing table through screws; Clean the installation reference plane of the mandrel and the upper reference plane of the indexing table base, and then apply a layer of lubricating oil; install the indexing table base based on the shaft section of the mandrel; the countersunk threaded holes at the four corners of the indexing table base Connect the lifting ring for the handling of the indexing table; Step 2, install the support base on the base of the indexing table; The axis of the mandrel is used as the radial reference, and the upper reference plane of the indexing table base is used as the axial reference to install the supporting seat; before installation, the upper reference surface of the supporting seat is plastic-coated and scraped, and the thickness of the plastic-coated material is 0.707~ 1mm; measure the parallelism error of the upper reference surface of the support seat relative to the installation and positioning reference surface of the support seat before and after the plastic application, to ensure the accuracy and rigidity of the axial installation reference of the device; Step 3, install the helical standard gear and bearing seat on the circular indexing table; First, connect the spiral standard gear to the round platform through the pressure ring and screws, and adjust the axis of the inner hole of the spiral standard gear to coincide with the axis of the outer cylindrical surface of the round table, and then install the dense ball bushing B, the bearing seat and the dense ball shaft successively. Set A; take the reference plane on the support seat as the axial reference, and use the mandrel and dense ball bushing B as the radial reference to rotate the circular table. During the rotation process, gradually tighten the connecting screws of the bearing seat in diagonal order; finally The round worktable is connected with the bearing housing, the spiral standard gear and the pressure ring together, and the inner hole of the assembled bearing housing and the inner hole of the spiral standard gear are ground together; Step 4, install the worm and anti-backlash mechanism; First, connect the triangular seat vertical shaft, vertical support, knob support and small guide rail seat to the base of the indexing table through screws, and connect the guardrail to limit the stroke of the flat dense bead plate on the small guide rail seat, and then place the flat dense bead plate Then put the worm shaft into the worm box; the installation sequence is angular contact ball bearing, worm, angular contact ball bearing, compensation ring, flange, elastic coupling, flange shaft and harmonic motor; Adjust the thickness of the compensation ring by grinding according to the assembly clearance; the connecting sleeve is connected with the worm box through screws, and the harmonic motor is connected with the connecting sleeve through screws; then install the spring seat and the clutch seat on the connecting sleeve; Then connect the assembled worm box to the vertical shaft of the triangular seat through the dense bead sleeve C, and put the connecting sleeve on the flat dense bead plate; connect one end of the tension spring to the spring seat, and the other end to the spring adjustment screw. By adjusting the working length of the tension spring, adjust the radial pressure of the worm and the helical standard gear to 0.3~1kgf. After the adjustment, fix the spring adjustment screw to the vertical support with a nut; finally connect the eccentric shaft, knob and handle, and manually Operation, so that the worm is out of mesh with the helical standard gear, so as to realize the rapid indexing of the indexing table; Step 5, installation of dust cover and platform; First spot weld the dust cover and the rigid ring together, and then assemble it on the base of the indexing table; then turn the handle to make the worm out of mesh with the helical standard gear; The oil storage tank of the screw, the tooth groove of the spiral standard gear and the spiral groove of the worm are filled with low-viscosity lubricating grease; Finally, press the dense ball bushing A into the middle of the mandrel and the bearing seat until the flange on the dense ball bushing A is stuck on the bearing seat.