The precision of gear-hobbing machine of 0 drive numerical control is analysed
- source:NEWRGY CNC Machining
Gear-hobbing machine of error of gear-hobbing machine machine tool is one of machine tools with transmission most complex concern. Traditional gear-hobbing machine is passed inside, outside implementation of couplet drive catenary boils cut treatment, transmission chain is long, such not only the influence machines precision, return those who affect precision to maintain a gender. 0 drive gear-hobbing machine uses form of electric main shaft to realize the straight couplet of electric machinery and hob, electric machinery and workbench, each feed axis uses machine tool other electric machinery - shaft coupling - deputy form realizes ball guide screw whirligig is changed to what move point-blank, land of such very old rate shortened catenary of machine tool drive, the differential drive catenary that can cancel to machine the place when inclined tine to need even, utmost ground reduces expatiatory drive cable length the influence degree to machining precision. In addition, because structure of 0 drive gear-hobbing machine is simple, each axis all is controlled by numerical control system, achieve the linkage between each axis more easily than traditional structure, raise the treatment precision of the machine tool thereby. Although 0 drive gear-hobbing machine eliminated the source of a few errors in traditional machine tool, but the new configuration that it uses also can bring new influence to machine precision, the article will fasten proceed with of face of tripartite of system of all, feed and control system from main shaft, analyse the effect of structure of 0 drive machine tool to machine tool precision. 1.
System of main shaft of system of 1 main shaft is the core of gear-hobbing machine, it is affecting the treatment precision of gear greatly. The precision of main shaft component basically reflects the circumgyrate precision in main shaft and stiffness rise, and circumgyrate precision and stiffness are reached on the form of main shaft definitely again assemble a form. The hob main shaft of 0 drive gear-hobbing machine and workpiece main shaft all use form of electric main shaft. Because interior of electric main shaft is double bearing to support a construction, choose bearing of tall stiffness bearing to be able to raise character of stiffness of electric main shaft, reduce its flexibility to be out of shape, error of radial of circumgyrate sum of errors, the activity form that assures electric main shaft thereby is characteristic. To raise precision of electric main shaft further, bring to bear on to system of bearing of main shaft bearing proper tighten force beforehand, eliminate the windage of bearing interior not only so, the flexibility that still can make roll body produces certain amount is out of shape, increase the interface of scroll body to accumulate thereby, raise the circumgyrate precision of bearing, achieve the goal that raises main shaft precision. Besides the influence of bearing bearing, another main factor that affects precision of electric main shaft is electric main shaft medicinal powder hot issue. Below status of job of electric main shaft, the stator of electric machinery and rotor will produce much quantity of heat, will deliver main shaft to go up, these quantity of heat can affect precision of main shaft itself not only, more important is, it can cause the heat of main shaft bearing to be out of shape, the heat that affects electric main shaft thereby is characteristic. To remove hot metabolic effect, the design in electric main shaft has circular refrigeration system, the heat that it can take away the major quantity of heat that electric machinery produces to reach its bearing in order to reduce main shaft is out of shape. In the design of main shaft of 0 drive gear-hobbing machine, the chooses pair of machine tools to machine precision influence of electric machinery is crucial. In traditional gear-hobbing machine, electric machinery is passed advocate athletic drive catenary passes motion hob, the campaign that uses transmission catenary to allocate hob and workpiece axis through Fan Chengyun in order to satisfy strict drive compares a relation between them. The accurate drive that motion transfers medium big drive to compare deputy can reduce gear-hobbing machine transmission error, this bit is most apparent to the influence of the workbench of gear-hobbing machine. Although 0 drive gear-hobbing machine can increase the rotate speed of hob main shaft greatly, but be based on gear hobbing fundamental, the rate of workbench is very low still. Below the circumstance of 0 drive drive, electric machinery error is impossible to the influence of workbench to be reduced through decelerate main transfer machinery, because this is right demand of character of torsion of workbench electric machinery is very high, not only can do bear the weight of greatly of force can accuse circumgyrate, the accurate low speed that still can offer high resolution moves. Additional, 0 drive drive is very high also to the stability demand of electric machinery. Character of frequency of the physical characteristic that integrates electric machinery, quadrature, laden requirement, timing requirement, main shaft electric machinery chooses efficiency commonly tall, and the communication synchronism electric machinery with better character of high low speed. Gear hobbing is process of interrupted cutting treatment, because 0 drive gear-hobbing machine can offer higher hob rotate speed, this brings frequency of taller cutting vibration, to avoid the resonance undesirable effect to gear cutting, requirement report main shaft has taller natural frequency to be stimulated in order to be far from brace up area, from this, also rise accordingly to the requirement of the natural frequency of electric machinery. 1.
System of feed of 2 gear-hobbing machine is in numerical control gear-hobbing machine, the axial of workbench and radial feed motion are to pass slideway of servo electric machinery, linear scroll and ball guide screw to come true. The feed system of numerical control machine tool not only should have taller transmission precision and fixed position precision, still should have answer a gender goodly quickly, avoid crawl. The generation that crawls as a result of feed basically is the attrition force because of feed system bigger and send, introduce coefficient of friction in numerical control gear-hobbing machine small, high accuracy and have the Gao Gang that increases negative charge beforehand to spend linear scroll slideway, it not only the athletic precision that can raise part of machine tool shift, return the stability that can make sure workbench low speed moves, make workbench motion even, smooth thereby, without vibration, achieve precision of high fixed position and tall repeatability precision, achieve the enough stiffness that matchs with use condition photograph easily. Pass with the ball guide screw that moves point-blank at realizing workbench proper beforehand force, win 0 backs unoccupied place reach small hot loss, assured the athletic precision of workbench and fixed position precision further. In feed system, the join of servo electric machinery and ball guide screw comes true by flexibility shaft coupling. Flexibility shaft coupling has buffer, suck brace up the function with compensation error, in regarding feed as transmission flexible link, flexibility shaft coupling keeps apart the vibration of electric machinery effectively at lathe bed besides, raised machine tool precision. 1.
The fundamental of cutting of gear hobbing of 3 control precision is gear exhibit movement, accordingly, strict drive should be abided by to compare a relation between hob rotate speed and workbench rotate speed, its are specific athletic equation is as follows: In type: VZ, vy is the β of feed speed; of axis of Z, Y respectively, λ is gear workpiece helix angle and hob helix to rise horny;mn to be;nb of modulus of extent of helical gear method respectively, nc is hob rotate speed and workbench rotate speed respectively. 0 drive gear-hobbing machine cancels the gear in traditional gear-hobbing machine to differ extension compose, use electronic gear case to realize what each axis moves to match, use half closed circuit or full closed-loop control, be compensated through numerical control and correct mechanical error, the fixed position precision that raises each axis and repeat fixed position precision, simplify thereby machine tool structure, raise a machine tool to machine precision, increase machine tool dependability. The error that be changed in disperse to numerical control system and brings when processing operation data, numerical control software can be eliminated, assure the precision of numerical control system thereby. Following plan institute show the composition of a picture of numerical control knot of 0 drive gear-hobbing machine. Graph of system of gear-hobbing machine of 0 drive numerical control is each axis coder for electric machinery of each axis drive 2.
Gear hobbing processes process error 2.
1 hob and installation are in gear hobbing treatment, hob quality and hob installation precision are main craft error factor. According to statistical data, the base pitch deviation of the gear that be cut is made an appointment with 80% originate hob error, and teeth shape error is made an appointment with 65% originate hob error. From this, the precision that assures gear-hobbing machine must make sure hob and hob install precision. In gear hobbing process, the production error of hob itself is easy bring teeth shape error, if tooth flank gives asymmetry of arris, tooth form and error of tooth form horn to wait, these errors can affect the smooth stability of gear clench the teeth finally. To avoid afore-mentioned teeth shape error, general the gear of above of 6 class precision, need the hob of precision of the class that use AA, after must rolling edge to grind at the same time, undertake to hob precision examines. The mounting error of hob is affecting the treatment precision of gear directly, its basically are reflected in hob radial change of jumpy, axial is moved, hob axes tilts, in be opposite bad to wait for a respect. Accordingly, when installing hob arbor, should special attention the end panel of arbor and hob beats and radial beats, among them the clamp of hob should be reached through hob, axle sleeve adjust the static friction force between spacer end panel to achieve drive requirement. Additional, should contain in the hob system that high speed runs medicinal powder hot system in order to take away redundant quantity of heat, reduce the heat of cutting tool to be out of shape thereby. 2.
2 workpiece and installation cancelled transmission catenary as a result of gear-hobbing machine of 0 drive numerical control, when gear of reason rolling cut, workbench graduation worm wheel is making the Zhou Jie with the generation in installation accumulate an error to be eliminated. The influence is depended on by the main reason of precision of treatment gear motion workpiece installation is prejudicial, it is by line of axes of the aperture inside workpiece and centre of turning circle of machine tool workbench not coincide place arises. Install to avoid and be reduced prejudicial the influence to athletic precision, hob arbor is used can bilge arbor in order to raise centering precision. On the other hand, raise the stiffness of clamping apparatus and arbor as far as possible, assure the clamp degree of workpiece. Workbench main shaft passes 7 ∶ the taper aperture of 24 and arbor connection, ensure the circumgyrate precision of workpiece. Additional, the pitch that ages the geometrical precision of base is affecting gear directly accumulates sum of errors to age circle diameter jumps. Be counted to jump over by the tine of treatment gear much, the geometrical precision of tine base is smaller to the influence of pitch error. Because tooth flank is machined,often be datum plane with gear aperture and end panel, it is so in the outfit clip of workpiece, should notice the positional precision between precision of bore diameter dimension and datum plane particularly, when be being installed in order to control the aperture inside workpiece and the clearance between arbor and tine base inside aperture and error of end panel verticality avoid thereby and reduce teeth shape error. 3.
Last word gear-hobbing machine of 0 drive numerical control simplified greatly rigid structure, reduced the transmission error between electric machinery and main shaft, increased the slewing speed of high speed limit of main shaft, make boil cut treatment to precision gets assuring and rise somewhat below high-speed condition. CNC Milling CNC Machining