1、91 FTM 2A- CNC Technology and New Calculation MethodsPermit Efficient System IndependentManufacturing of Spiral Bevel Gearsby: Dieter Weiner, Klingelnberg SOhne,r1American Gear Manufacturers AssociationiI1TECHNICAL PAPERCNC Technology and New Calculation Methods Permit Efficient SystemIndependent Ma
2、nufacturing of Spiral Bevel GearsDieter WienerKlingelnberg St_hneTheStatementsandopinionscontainedherein are thoseof theauthorandshouldnotbe construedas anofficial action oropinion of the American Gear ManufacturersAssociation.ABSTRACT:A strictly applied CNC technology on machines for cutting or gri
3、nding spiral bevel gears allows the machining ofdifferent gearing systems on one and the same machine. Based on this, the selection of the most favorable gearingsystem is possible, based on economicalissues, load bearing capacity and noise characteristics.Copyright 1991American Gear ManufacturersAss
4、ociation1500 King Street, Suite 201Alexandria, Virginia, 22314October, 1991ISBN: 1-55589-602-2CNC Technology andNew Calculation MethodsPen_t Efficient SystemInd_l_ndontManufacturingof Spiral Bevel GearsDr.-Ing. Dieter WienerExecutive Vice PresidentKlingelnberg SShneRemscheidGearing DivisionI. Introd
5、uction 2. CNC machine systemsCNC technology offers new opportunities for the 2.1 Soviet Union - zegiatEation (figuzt I)manufacture of bevel gears. Whilst traditionally, thepurchase of a specific machine at the same time The first machine known to us with a cross slidedetermined the system, CNC techn
6、ology permits the working at the work piece side is the machine, shownprocessing of bevel gears using a wide variety of in figure 1, according to the russian application formethods. The ideological dispute between “tapered patent SU 724487 A, dated March 30, 1980. On the lefttooth or parallel depth
7、tooth“ and “single indexing or figures side, the cross slide with its ways “3“ andcontinuous indexing“ no longer leads to an irreversible “12“ describes the circular motion of the tool. Thefundamental declsion. The systems have instead become actuation of the cross slide is a mechanical - hydraulicp
8、enetrable, and with existing CNC machinery it is system.possible to select this or that system according tofactual considerations at a later date.This essay, by giving a brief overview of themachines and systems available on the market or _ ,3 ,4,scurrently at the development stage, plans to discuss
9、 _ _the possibility of processing different types of gear ,i _ /6_09cutting on one and the same machine. Thereafter, the _ _ _characteristics of gear cutting systems will becontrasted with one another, and finally, thepossibilities of gear cutting optimization offered by _ .current calculation and m
10、anufacturing technology inconnection with CNC measurement technology will bediscussed.4Figure 1: Russian machine with X-Y cradle2.2 JHIcs:_l - zegistxati_ (fi_ 2) 2.4 Grinding m_ (f_ 4)A CNC-controlled_vel gear cutting_chine with Fibre 4 is showing a full CNC controlled _vel _cross slide is_ntioned
11、in an application for patent gear grinding_chine_C 80, made by Klingenberg. Theno. 255 296 A 1 of the co,any Modul in the former _rman generating motion of the tool, in this case the grindingDemocratic Republic. The principle of this machine is wheels, is performed by the y-axis (cra_e motion). Thel
12、ayed out in figure 2. The generating motion of the tool advantage of this syst_is the fact, that only threeis achieved by overlaying slide “F“ and “E“. This axes are in motion during the generating process: themachine is also e_ip_d with (co_uter controlled) z-axis (workpiece rotation), the y-axis (
13、workhead) andtilt axis and swivel axis. These are the axes “D“ and the x-axis (helical motion) . By intelligent“C“. superimposition of these three axes the tilt settingIf the work piece is cut with “tilt“, the C-axis is unnecessary. The do_le spindle wheelhead allows thehas to succeed continous path
14、 controlled, whilst the grinding of pinions, which were cut by the traditionaltilt-axis D is only a fixed setting axis. five cut _thod at the concave and the convex flanksseparately, in one setting.i iii i. I 19Fibre 2: Modul_chine with CNC-controlled X-Y cradle Fibre 4: CNC bevel gear grinding mach
15、ineKlingelr_berg _C 802.3 Japan - regiatzati_ (fi_ 3)In the Japanese application for patent no. 3643967 2.5 Phoenix (figuze 5)(figure 3) a machine is introduced, in which all themotions are appointed by the CNC control as well. The At the Phoenix machine (fibre 5), made bygenerating motion is, as we
16、ll as with the previous Gleason, the generating motion of the tool is done,mentioned machines, achieved by a cross slide. The x- like at the first three machines, by the crossaxis and the y-axis are used to achieve the generating slide, visible in the left side of the picture. Themotion of the tool.
17、 At this machine, like the russian ways 16 and 20 are the machine ways for the cross_chine, no tilt and no swivel is provided, slide. Therefore, the cross slide motion is _r-formed by the tool, in the opposite to the previousdescried machines, this machine has the charac-teristics of continously mov
18、ing the_chine rootangle during the generating process. This _tioneliminates the tilt setting and the swivel setting.28 I_31 _9 3_38 R| 353=21 23FigUre 3: Japanese CNC machine23. _mazO_tt_mgSystm_The two decisive differentiating features of gearcutting systems are :continuous - single indexing proces
19、sparallel tooth depth - tapered toothIn principle, all varieties can be combined withone another. In practice, however, the followingprinciple combinations have become established:continuous with parallel tooth depth and epicycloidandsingle indexing process with tapered tooth and arcIn the case of p
20、arallel tooth depth, manufactureFigure 5: CNC bevel gear processing mechine Gleason is conducted on precise pitch cones (figure 7). UnlessPhoenix corrections are made, no crowning will occur. The geargenerating process is precise and does not result inprofile bearing, and as a result of the identica
21、l tool2.6 ENC (figure 6) radii of concave and convex flanks in a continuousprocess (figure 8), without a desired correction, noFigure 6 conclusively shows a full CNC bevel longitudinal convexity is produced. The advantage isgear cutting machine, the KNC 40 / 60 series of that it is simple to conduct
22、 all calculations on theKlingelnberg. At this machine, like the three crown gear in question; the complicatedthree-dimensionalmachines previously described, all the axes are CNC bevel gear problem becomes a simple two-dimensionalcontrolled. The E-axis is only used for single crown gear problem. Prof
23、ile bearing is producedpiece production and small lot size production.This precisely and specifically via the tool, and theaxis is setting the crowning eccentricity auto- longitudinal crown via the difference in radius of thematically when cutting bevel gears with the divided tool flanks for convex
24、and concave flank. Thecutter head. This axis is not used for high volume difference in radius is achieved via a separated bladeproduction, regardless whether the face milling or head (figure 9) in individual and small seriesface hobbing process is applied. The advantage of production, and in large s
25、eries production (figure 10),this machine is the great stiffness, since in the via the tool inclination or the gear generating process.single indexing process only three axis are in motionat the same time: the work piece rotation axis B,the workhead rotation axis A and the infeed axis X.Figure 6: CN
26、C bevel gear generating machine Figure 7: Manufacture on precise pitch conesKlingelnberg KNC 40/60- The continuous process is always a completingprocess: both flanks of the gear and pinion arecompleted simultaneously in each case. _-_._ The tapered tooth depth is normally not conductedaccording to a
27、 theoretically precise process and. therefore necessitates a precise pre-calculation.Depending on the branch, highly differing methods areused; key words are the five-cut method, in which the. / ring gear is prepared in two cuts (roughed down) andcompleted (finished) and the pinion is roughed down a
28、ndeach flank individually finished. However, the completingmethod is increasingly gaining in popularity here aswell, whereby the gear and pinion are completed in asingle operation. As in circular arc gear cutting the_ 1 blades for the inner and outer cutters have different7723 radii, the completing
29、method requires a special designeg. using the duplex-helical method. For circular arcgear cutting, highly efficient processing methods havebeen developed which can beused to particular advantageFigure 8:Tool radii in a continuous process if the ring gear can be produced in a plunging processon the b
30、asis of the transmission ration.i Differences in load capacity which are alwaysi suspected and claimed have not been proven in practicalexperiments (cf. AGMA meeting last year: report by TedKrenzer). Apparently, other design criteria are morei important than the gear cutting system, provided themain
31、 drive data are similar.One definite advantage of circular arc gearcutting is that it is possible to grind very8518 economically with cup wheels in completing designs. Itis also possible to grind the continuously produced gearcutting with a cup wheel with an epicycloid as the toothlongitudinal line.
32、 The difference between the arc formof the grinding wheel and the epicycloid form of theFigure 9: Split blade head for individual and small tooth in lengthwise direction is within the stockseries manufacture allowance. However, this form of gear cutting requiresseparate processing of the right and l
33、eft flank. Thecompleting design of circular arc gear cutting, on the- other hand, enables completion of both flanks viagrinding in a single step.4. Calculation_“ r.-_-. For all processes, calculation methods have since+_ been developed which simulate the manufacturing process_ _ _2_i_ )_ and the run
34、ning conditions in the drive unit._!_ The important factor is that the calculations function_ _“_+_i independently of the system. Only in this way is itpossible to achieve a comparison which is independentOf the process. In addition to the pure designcalculation on the basis of the load capacitycalc
35、ulation according to AGMA standards or DIN9015standards, which will hopefully soon be standardized,contact area analysis provides a reliable indicationof the running behaviour of a bevel gear in the driveunit. Optimization of a truck bevel gear set is givenas an example.Figure 10 :Single-part blade
36、head for series manufacture44.1 Opt4-41ation with =_3az,:l, to noisebehavou,As the gear set is noise-critical, in the original ._._-_design, i_ortance was attached to a low single-flank_,. gear generating error.Figure 11 shows the contact area and single-flank _“gear generating error (motion curve)
37、of the original L-design. The design has low convexity values due to thehigh noise requirements. For the drive, dislocationvalues below load classes I and II are known. These load .,_,_,_,_:,_? ,-“classes correspond to 30% and 100% nontlnal load Figure 12 shows load-free contact areas for the zero -
38、_ ,position and for the dislocations which correspond toload classes I and II.The large contact area indicates smell crownings. y Even at 30% nominal load, a sharp edgewear occurs, which worsens at full load.With knowledge of dislocation values, a gear *=“_-_“_cutting_thod was designed which was far
39、 less sensitiveto dislocations, although the single-flank gear generating 1191Conta_ area ana slngEeflank gearerror was further improved (figure 13). The relevant g_o_,at,n_.,a_arse, 95contact areas are illustrated in figure 14. The load- _ong.n,_,g.lfree area appears smeller, but nevertheless, thes
40、ingle-flank gear generating error is i_roved by afactor of 2.5. No edge wear occurs at partial and fullload (figure 14). The drive is far quieter in the entire Figure 11: Contact area and single-flank gear generatingload area than the original design, error of a gear set (original design)The followi
41、ng measures were implemented:- As the contact area tends to wander in thedirection of tooth length, the contact areasensitivity was reduced by switching from large _-cutter design to small cutter design.Sensitivity to contact area dislocations in the -direction of tooth length is smallest in the so-
42、called right-angled case (figure 15). _I=_:_ .- By means of the pin-pointed use of helical contacts(bias in) the overlap ratio was improved for all _- .load areas without making the gearing more I_._-_ E:!_sensitive to dislocations. -_The bevel gear set ground in this way is quieterthan a convention
43、ally manufactured gear set of theconventional design. By means of lapping, the noisekM_haviour would be worsened. _.-._“and two load c_es(o._n_ _es,gn)Figure 12: Contact areas with zero load and two loadclasses (original design)AFigure 13:Contact area and single-flank gear generating Figure 15: Arra
44、ngement of bevel gear and cutter inerrors optimized a“right-angled case“4.2 Optimization with _a_dto load capa_tyAnother example is intended to show how the loadcapacity of a gear set can be optimized usingcalculation and CNC-controlledmanufacture. The gear- “ in question is an offset gear set for a
45、 rail drive. The_ set suffers in of whichgear pittings case overloading,-.- occur initially as micro-pittings on the tooth head ofthe pinion. Obviously the hertzian stress is too high.Standard tooth contact area analysis reveals a goodcontact pattern in lengthwise direction (figure 16).Only the toot
46、h contact analysis (figure 17) under load_ =_= demonstrates, that the level at the tooth flankstension gets to high under overload. The Hertzian stress canbereduced by increasing the profile crowning, which issimply conducted by altering the input data for thegrinding process. One then receivesa con
47、tact pattern,which is more distinctive in the direction of the tooth- height (figure 18). The tooth contact analysis indicatesF_I“ a decrease of the maximum Hertzian stress from 2,600 N/I-_ n_nto 2,120 Nlmm, but one recieves tension peaks in the=-.-_.-_-I=_._:._ root relief of the pinion respectivel
48、y at the top of thegear. This can be prevented by means of tip relief atco ,.oo sooo,oo19198 the gear respectively root relief at the pinion. In thiscase, the Hertzian stress is not increased, but thetension peaks at the top of the gear teeth are avoided(figure 19). The extended lines indicate the r
49、eductionFigure 14: Contact area at zero load and two load classes of these tension peaks are reduced from 2,180 N/n_tooptimized 2,135 N/_n. By means of special software, the tip reliefcan also be conducted in a circular motion orelliptically (figure 20).I6Figure 16: Contact area example 2 Figure 18:Contact Pattern with smaller profile crowning_ IT,=28_INmI IT,.28_,NmIcoast side drive side coost s_de drive sideFigure 17: Load distribution Figure 19: Load distribution with smaller profilecrowningAvfillet radius flank form Prof
