Tooth form machines the key that is whole gear cutting. According to treatment principle, tooth form treatment can be divided mix for figuration law extend a law two kinds. Tine of mill of milling cutter pointing to shape, dish broach of tine of mill of form milling cutter, gear pulls internal gear to wait is example of dentiform of figuration law treatment, and tine of gear hobbing, shave, inserting tine to wait is to exhibit a law to machine dentiform example. Introduce a few kinds to use now exhibit a law to machine dentiform to machine a method. Gear hobbing of characteristic of gear hobbing of ⑴ of 1 gear hobbing is tooth form the productivity in treatment is taller, use method of the widest a kind of treatment. And versatility of gear hobbing treatment is good, can machine columnar gear, worm wheel to wait, yi Ke machines involute tooth form, circular arc tooth form, cycloidal tooth form to wait. Gear hobbing can machine gear of small modulus, small diameter already, can machine gear of big modulus, big diameter again, treatment inclined tine is very convenient also. Gear hobbing can machine 9 ～ directly gear of 8 class precision, also can regard above of 7 class precision as the rough machining of gear and semifinishing machining. Gear hobbing can obtain taller athletic precision. Because the tooth flank when gear hobbing is,become, the tooth number that joins cutting is limited, the exterior surface roughness of reason tooth flank is worth bigger. Machine precision and tooth flank quality to rise, appropriate parts gear hobbing of thick, essence. Quality of treatment of ⑵ gear hobbing is analysed 1) the machining error that affects transmission accuracy analyses the main reason that affects transmission accuracy is, the hob in be being machined and was happened to change by the relative position of treatment gear and opposite motion. The change of relative position (geometry is prejudicial) error of generation gear radial, it beats with tine circle radial Δ Fr comes assess; The change of opposite motion (motion is prejudicial) generation gear is tangential error, it changes with length of public law line Δ Fw comes assess. Try to discuss respectively now: The radial error of ① gear. The radial error of gear is when pointing to gear hobbing, the circumgyrate axes when because age,the circumgyrate axes of base and gear work not coincide (occurrence geometry is prejudicial) , the pitch that the teeth of a cogwheel that makes cut gear produces radial deflection and causes accumulates an error (graph 1) . From the graph 1 can see, the tine base when O is angrily centre of turning circle, o ′ is tine base the geometrical center of fiducial aperture (namely the) of centre of turning circle when gear works. When gear hobbing, the coincide of centre of turning circle of the basic circle center of gear and workbench at O, it is even that each tooth form that such cutting go out distributings relative to O of basic circle center (the P1 ＝ P2 on circle of the solid line in be like a graph) , but when gear works, be to circle what ′ of O of fiducial aperture center turns (assume to prejudicial) is not had when installation, at this moment each tooth form distributings relative to ′ of O of graduation the centre of a circle inhomogenous (the) of ′ of P2 of P1 ′ ≠ that if pursue medium,double dot underlines a circle to go up. Apparent the change of this kind of pitch makes tooth profile radial deflection is caused, reason calls the radial error of gear again. R, the R of reference circle radius when gear hobbing, it is with ′ of aperture axes O rotate when the center, the reference circle radius that tine encircles pursues 1 geometry is prejudicial of the gear wheel of radial error ② that cause tangential error: Of gear tangential the error is to point to: Error of tine drive catenary is divided because of gear-hobbing machine when gear hobbing, cause instantaneous drive to be not stabilized than generation, make machine tool workbench differs fast rotate, workpiece circumgyrate speed, the edge of teeth of a cogwheel that cuts gear is tangential the pitch that produces displacement place to cause accumulates an error. If pursue,2 are shown. Graph of 2 gear tangential error by the graph 2 can see, appear when teeth of a cogwheel tangential when displacement, the every other in the graph ages the length that measures public law line differs. Be like 2, the length of public law line between 8 tine is more than apparently 4, the length of public law line between 6 tine. Can see accordingly, through length of public law line fluctuant Δ Fw can mirror a gear pitch to accumulate an error (tangential partial) , because length of line of this aborning public law is fluctuant and OK,serve as assess gear to hand one of quota of athletic accuracy. The circumgyrate error of machine tool workbench, basically depend on the transmission error of catenary of the drive that divide tine. In the each drive component of catenary of the drive that divide tine, the mainest link that affects transmission error is the graduation worm wheel below workbench. The pitch that graduation worm wheel is being made and arises in installation accumulates an error, make corner error happens when workbench circumgyrate, these errors will forthrightly answer mirror tine base to make its produce pitch to accumulate an error. The another important segment that affects transmission error is to divide tine to hang annulus, cent tine is hanged annulus make and mounting error, also can deliver workbench to go up with larger proportion. To reduce gear tangential error, basically should raise the production of worm wheel of machine tool graduation and installation precision. To high accuracy gear-hobbing machine still can pass corrective device to compensate the graduation error of worm wheel, make be obtained by treatment gear the main error that taller treatment precision affects gear job to make the same score stability is deviation of teeth shape error, base pitch etc. The machining error cent of smooth stability of job of ⑵ influence gear is folded 1) the common teeth shape error after gear hobbing of ① of teeth shape error, if pursue,3 are shown. Among them tooth flank gives asymmetry of arris, tooth form and root to cut, can see directly; And error of cycle of sum of errors of tooth form horn needs to be measured through instrument ability piece. Should point out, the graph behaves a form a few kinds 3 shown errors are teeth shape error alone, factual teeth shape error often is the overlay of a few kinds of afore-mentioned forms. A) gives root of E) of periodic error of D) of error of horn of tooth form of arris B) asymmetry C) to cut a figure the main reason that teeth shape error produces ② of 3 common teeth shape error is: Hob is being made, blade is ground and the error exists in installation, the error of little periodic corner that is the existence in circumgyrate of machine tool workbench next. These errors are analysed below the influence to teeth shape error. ③ reduces the measure of teeth shape error: Analyse from above knowable, the production error that the main factor that affects teeth shape error is hob, mounting error and machine tool divide the error of the worm in tine drive catenary. To assure tooth form precision, besides choosing hob and machine tool correctly according to the accuracy class of gear, want special attention of hob grind precision and installation precision again. The tooth flank when tooth flank gives the main reason gear hobbing of arris gives edge sometimes, its are main the reason is: Hob tooth edge is circumferential sex of divide into equal parts is bad to mix the radial circle with the larger presence after hob is installed is jumpy reach axial change to move etc. By the graph 4 see, tooth existence differs when dividing an error, each tooth is relatively accurate lag of some of positional some lead, this kind of lead and lag make the hob of cutting blade deviate on tooth basic the whorl surface of worm. Consequently, in the process of rolling cut gear, can appear " cut too " and " cut for nothing " and generation teeth shape error. Graph 4c is the schematic diagram that takes out 3 tooth position to try to magnify from inside graph 4b. The position that double dot underlines the tooth when expressing not to have error of divide into equal parts in the graph (with involute tooth flank tangent) ; When solid line expresses to have error of divide into equal parts, tooth 2 cause point because of lag " cut for nothing " with tooth 3 cause point because of lead " cut too " circumstance. Error of sex of tooth divide into equal parts heals big, this kind " cut for nothing " and " cut too " more serious, tooth flank gives arris to heal apparent. Error of sex of tooth divide into equal parts is different to the involute dentiform influence of different curvature, tooth form curvature heals big (namely gear basic circle heals small) the influence heals big, this ages namely the pinion with little number why the reason that tooth flank gives edge easily. A) tooth differs 4 tooth of plan of plan of enlarge of C) of process of the rolling cut that divide B) differ after the hob of teeth shape error that cent causes is installed, if exist,axial change is moved, hob tooth face can arise likewise " cut too " or " cut for nothing " make tooth flank gives edge. The error of tooth form horn of the main reason gear wheel that produces error of tooth form horn basically decides the error of tooth form horn at hob tooth. The error of tooth form horn of hob tooth, blade grinds the sum of errors of tooth form horn that grinds tooth generation by the shovel when hob is made the blame that place of face of the knife before tooth produces is radial sexual error and error of blame axial sex and cause. The influence of error of tropism of diameter of blame of face of the knife before tooth to teeth shape error, if pursue,5 are shown. 1 - tooth 2 - the horn before the horn before workpiece A) is more than 0 B) is less than 0 graphs what the influence finish machining to teeth shape error uses error of sex of radial of blame of face of the knife before 5 tooth of hob before horn is 0 ° normally (namely face of the knife before tooth is inside radial plane) , blade is ground bad when the horn before can appearing (or negative) . As a result of the horn after side is being had after be being ground via the shovel at the back of tooth side, because error of the horn before this tooth causes tooth form part necessarily,change. Horn is before when, decrescent of tooth form horn, the tooth form that cuts ages the top becomes fat (graph 5a) ; Horn is before when losing, tooth form horn greatens, the tooth form that cuts ages the top becomes thin (5b) . Graph error of sex of axial of blame of face of the knife before 6 tooth is right the blame axial sex of the face of the knife before affecting tooth of teeth shape error error, it is axial of edge of face of the knife before pointing to straight chamfer hob the parallelism alignment error to aperture axes (graph 6) . This kind of error makes each tooth deviate proper tooth form place, and tooth controls value of deviate of two side edge to differ, produce axial pitch deviation already so, cause tooth form again askew. When the main reason gear hobbing that produces tooth form asymmetry, appear sometimes error of tooth form asymmetry, outside the influence that is not axial sex error besides face of the knife before tooth, basically be the hob when gear hobbing in be opposite bad. Hob is right in it is the hob when pointing to gear hobbing located axial position should make firstly tooth (or alveolar) symmetrical line passes tine base center (graph 7) . Hob is right medium, the tooth form that cuts is symmetrical; Cause tooth form asymmetry conversely. The tooth number of tooth flank of hob bag sth resembling a net heals little, workpiece tooth form heals big and tooth flank curvature heals big when, tooth form asymmetry heals serious. Friend is older to modulus and the gear wheel with tine less number, in answering to make hob right seriously before gear hobbing. A) is right in tooth form B) is incorrect in tooth form graph pursues 7 hob are right in to dentiform the influence produces tooth form cycle the radial circle after the main reason hob of the error is installed beats and axial change is moved, worm wheel of machine tool graduation deputy medium the radial circle of graduation worm beats and axial, these metropolises make the periodic error with scraggly tooth flank appears when gear hobbing. 2) base pitch deviation adds man-hour in gear hobbing, the base pitch of gear should be equal to the base pitch of hob. The base pitch of hob: 0 ≈ of α of 0cos of Pb0=pn0cos α 0=pt0cos λ the Pb0 in 0 type of Pt0cos α , the base pitch of hob; Pn0, the law of hob to pitch; Pt0, the axial pitch of hob; α 0, the law of hob to tooth form horn; λ 0, the reference circle helix of hob promotes role, general very small, 0 ≈ of reason Cos λ 1. Can see from this, want to reduce base pitch deviation, when hob is made, answer to control the error of axial pitch and tooth form horn strictly; Sum of errors of radial to affecting the blame of face of the knife before the tooth of error of pitch of axial of sum of errors of tooth form horn sex is not axial sex error, also should try to control. 3) the gear of machining error analysis that affects gear to contact precision contacts precision to be contacted by facewidth direction undesirable contact bad influence with tooth depth direction. Affecting tooth depth direction to contact undesirable main factor is Ff of Δ of teeth shape error and Fpb of Δ of base pitch deviation, the β of F of Δ of teeth directional error that affecting facewidth direction to contact undesirable main factor is gear, analyse the main factor that affects β of F of Δ of teeth directional error only here. β of F of Δ of teeth directional error is to point to go up in reference circle cylinder, inside limits of facewidth job section, include actual tooth trace and the distance is apart from for the end panel between the smallest two designs tooth trace. The main factor that teeth directional error causes in gear hobbing treatment is as follows: Slideway of tool carrier of ① gear-hobbing machine exists relative to workbench circumgyrate axes when parallelism alignment error, gear can produce teeth directional error (graph 8) . 1, tool carrier slideway 2, tine base 3, clamping apparatus base 4, machine tool workbench A) slideway is not parallel B) slideway pursues askew the influence of error of slideway of tool carrier of 8 gear-hobbing machine to teeth directional error ② because the verticality error of end panel of clamping apparatus bearing and rotor line, or the verticality error of end panel of tine base aperture and fixed position (the teeth directional error that the error holding clip of the workpiece such as graph 9) all can cause the gear wheel that be cut. L, workbench circumgyrate axes 2, arbor axes 3, axes of the aperture inside tine base 4, feed direction 5, tool carrier slideway 6, washerbed down the livestock pursues installation of 9 tine base is opposite askew when the helical gear of influence ③ rolling cut of teeth directional error, outside removing afore-mentioned influencing factor, machine tool differential is hanged annulus error, also can affect the teeth directional error of gear. 2 insert tine and comparing ⑴ to insert tine principle and motion to insert tine with characteristic of gear hobbing craft also is the method of uses generally a kind of angrily in production. 1) the principle that insert tine: From the analysis on principle of the process that insert tine, the clench the teeth of columnar gear photograph that the knife that insert tine and workpiece are equivalent to one mutual to axes parallel, the knife that insert tine is ground with respect to the county before having, hind the high accuracy gear wheel that horn has cutting blade. 2) the main movement that inserts tine (graph 10) : ① cutting moves. Insert the fluctuation reciprocate of tine knife. ② divides tine to exhibit movement. The clench the teeth that should keep correct between the knife that insert tine and workpiece concerns. The knife that insert tine every move back and forth, the circumferential feed when the arc length that workpiece has turned on reference circle relative to cutting tool is treatment moves, the process of clench the teeth of reason cutting tool and workpiece namely circumferential feed process. Graph the 10 motion when inserting tine 3) radial feed moves. When inserting tine, come to be cut stage by stage complete tine is deep, the knife that insert tine is due and radial feed motion Fr. 4) motion letting a knife. When the knife that insert tine makes fluctuation reciprocate, it is working process downward. The tooth flank that already machined to avoid cutting tool abrade reduces tooth to wear away, when inserting tine knife to move up, workbench drives workpiece edge radial to quit cutting division a paragraph of distance, when journey of job of the knife that insert tine, workpiece extensive recovers from an illness. On the machine inserting tine of bigger norms, campaign letting a knife is finished by component of tool carrier of the knife that insert tine. ⑵ inserts tine and characteristic of gear hobbing craft to insert tine and gear hobbing to machine a method for commonly used tooth form together quite, their treatment precision and productivity comparative roughly also. But there is its characteristic severally again in the respect such as precision index, productivity and applied limits. Show an analysis to be as follows quite: 1) the treatment quality that inserts tine: The tooth form precision that ① inserts tine is taller than gear hobbing. Because insert tine knife,this is when be being made, can win exact involute tooth form through machine of high accuracy roll flute. The tooth flank surface roughness after ② inserts tine is worth smaller than gear hobbing. Its reason is the circumferential feed that inserts tine normally lesser, the cutting blade that tooth flank of subsidiary channels in the human body through which vital energy includes in the process that insert tine is counted relatively gear hobbing is much, the tooth flank surface roughness after inserting tine consequently is worth small. ③ inserts the athletic precision of tine to compare gear hobbing difference. Because be when gear hobbing, the tooth that one ship is hob some a few attends cutting, on workpiece all and alveolar these tooth are cut; And when inserting tine, the workpiece of cutting of each tooth in order on the knife that insert tine each are alveolar, consequently, the pitch on the knife that insert tine accumulates an error to will be passed directly be cut gear; Additional, the error of catenary of machine tool drive makes the Dao Xuan that insert tine changes the line of production unripe corner error, also make the gear after inserting tine has bigger athletic error. The teeth directional error that ④ inserts tine is bigger than gear hobbing. The teeth directional error that inserts tine basically decides to age at inserting contrail of reciprocate of machine main shaft and workbench rotor the parallelism alignment error of the line. The knife that insert tine reciprocate frequency is tall. Of main shaft and sleeve wear away big, because this inserts the teeth directional error of tine,often compare gear hobbing big. 2) the productivity that inserts tine: When cutting patternmaking to count larger gear wheel, the speed that insert tine should suffer reciprocate of main shaft of the knife that insert tine inertial restrict rigidly with the machine tool, cutting process has loss of time of light locomotive trip again, reason productivity wants than gear hobbing treatment low. But when the gear that machining size of tine of small modulus, much couplet, tine, the productivity that insert tine will be taller than gear hobbing. 3) the applied range that plugs tine: From above the analysis is knowable, insert tine to agree with treatment modulus lesser, job makes the same score small, facewidth the gear that stability asks taller and athletic precision demand is not quite high. The pinion in applying to gear of treatment internal gear, much couplet especially, rack and sector gear. But treatment helical gear needs to use helix guide, not as convenient as gear hobbing. CNC Milling