Processing technique of integral impeller electric spark studies

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Integral impeller blades range is sophisticated, machining space is limited, treatment precision demand is high, kinetic performance demand is good, already became current mechanism to make one of difficult point of the domain. Current, numerical control milling, nicety is cast more application receives in integral impeller treatment. But, when numerical control milling undertakes machining to lamina of difficult cutting material, small passageway, because suffer cutting tool tigidity to restrict very difficult treatment; Nicety casts production the process is complex, technical difficulty is great, percent defective is tall, apply to only but casting alloy. Electric spark machines the instantaneous high temperature that uses discharge generation, as will opposite as electrode workpiece surface is fused, gradually corrode removes material, achieve the goal of treatment. Consequently, electric spark treatment is in without the cutting force, dominant position that does not accept workpiece hardness to restrict a respect to having other treatment method to be able to not be likened to [1-3] . The electrode that place of impeller of whole of electric spark treatment uses can design type of composition bodily form and integral form, immediate impact wears electrode form to be machined the precision of the spare parts. Fission electrode treatment is formed easily on blade face build accept chance to extricateoneself from an awkward position, make blade face produces outline to spend an error, affect the figuration precision of integral impeller thereby. The article makes full use of the three-dimensional model that the three-dimensional model function with SolidWorks powerful software built integral impeller, the structural characteristic that combines integral impeller designed integral type electrode; What install a form in the light of workpiece and electrode is different discussed plan of two kinds of treatment; Appear to avoid electrode to machine what the problem interferes in the process, to electrode motion undertook imitate, undertook interfering checking; Undertook study to the workmanship of figuration electrode finally. Impeller of whole of integral impeller modelling is comprised by hub and the lamina along Zhou Xiangjun cloth. Blade modelling is key of integral impeller formative, normally of blade model face data is basis blame is decided constant model of three-dimensional stickiness fluid undertakes complex numerical value is calculated, after be being amended via the experiment, get, cannot use analytic type expression commonly, pass however give blade a certain number of sectional model value drop will describe. Blade is three-dimensional formative is basic the method is: Choose side of → line → , generate sectional curve by the several foothold of disperse, generate curved surface by certain regulation by sectional curve. SolidWorks uses NURBS (Non-Uniform Rational B-Spline) the method has curved surface model [4] . NURBS realized the unity of analytic geometry and free curve curved surface 2 times, through local change reference point or authority factor can adjust figure of local curvilinear curved surface namely, and do not affect other part, have good geometrical quality [5] . Definition K second the expression of NURBS curve: Among them, ω I (I=0, 1, ... N) the authority factor that fastens to connect with reference point; Ni, k (U) be by node vector U=[u0, u1, ... Un+k+1] is pressed heart is Boer -- take an examination of a gram this the K that recurrence formula decides second B batten base function. In applying actually, to make batten head extreme nods as apical as control coincide, often take U0=u1= of arrow of two upright node... =uk=0, un+1=un+2= ... =un+k+1=1, and ∈ of U of curvilinear definition region [0, 1] . K × L second the justifiable cent type of NURBS curved surface expresses to be: Among them, control apical Di, j, i=0, 1, ... M; J=0, 1, ... N presents rectangular array, form reseau of a control; ω I, j is with apical Di, the authority factor that J photograph contacts; Ni, k (U) , i=0, 1, ... M and Nj, l (V) , j=0, 1, ... N is U respectively to K second with V to L second B batten base function. Combine the characteristic of NURBS function, when blade modelling by foregone model value drop calculates reference point instead, reoccupy parameter method has curve and curved surface model. Because by blade the Xie Gen that sectional data place generates is plane, and Xie Gen and the part that the surface outside hub intersects are columnar face, rise to join Xiegen and hub, add the sectional curve with as sectional as Xie Gen identical curve artificially, make blade lengthens along Xiegao direction. Incorporate blade and hub next, have blade circumferential array, form integral impeller, if pursue,1 is shown. Figuration electrode designs electric spark to machine integral impeller to use milling law and figuration to copy a law normally. Law of electric spark milling uses ball electrode commonly or wafer electrode, the advantage is electrode is made simple, defect is blade figuration precision low, electrode loss is quick. Figuration copies a law to use the figuration electrode of as complete as blade face joint to undertake copying machining, blade figuration precision is taller, it is the effective method that machines integral impeller. The design principle that uses the electrode when figuration copies a law to machine is: (1) designs electrode face wants to agree with posture of face of blade face, the circle outside hub; (2) designs electrode wants mature the influence to discharge clearance, undertake to electrode face corresponding deflection is handled; (3) designs electrode wants to be able to have not been had cut the ground by treatment initiative position moves to machine stop bit buy; (4) designs electrode should be helpful for improving treatment efficiency, reduce the sources of energy to use up; (5) when electrode is designed, want mature arrive to install and search convenient. Electrode feed direction is the main factor that the consideration needs when electrode is designed, combine the characteristic of integral impeller, the impeller radial that when choosing blade model, uses regards the feed of the electrode when treatment as direction. Existing technology is right electrode treatment undertakes proper analyse is divided partly, use fission electrode to machine integral impeller (see a picture 2) . But, undertake machining from the two side of eddy turntable when electrode when, be in the coincide place of blade face easily to form build accept chance to extricateoneself from an awkward position, affect the figuration precision of blade thereby. And use integral electrode to machine integral impeller (see a picture 3) , can avoid effectively to build accept chance to extricateoneself from an awkward position, improve treatment efficiency. Because electric spark treatment is treatment of contact of a kind of blame, the presence is constant discharge clearance δ between tool electrode and workpiece [6] , when designing electrode need has electrode side deflection is handled, make discharge clearance exists between electrode face and integral impeller face. Consider electrode integratedly model face precision, installation and search convenient sex, if the graph is shown 4 times,design electrode. Machine tool of figuration of electric spark of numerical control of nicety of linkage of N850 of application of option of Nextpage treatment program 5 axes (see a picture 5) undertake machining to integral impeller, this machine tool has X, Y, Z 3 sharp movement rod, a axis (W axis) with C axis (U axis) two graduation runner shaft coming back. When electric spark is machined, electrode gives individual lamina along copy of feed of integral impeller radial above all, next, electrode or integral impeller graduation rotates, copy next lamina. Rotate according to graduation different design of the form program of two kinds of treatment: The first kind is electrode after linear feed treatment finishs a lamina, a axis revolving stage drives integral impeller to rotate the treatment process that enters next lamina (see a picture 6) ; The 2nd kind is integral impeller is secured do not move, linear feed treatment finishs electrode after a lamina, use C axis to drive electrode to rotate, the treatment process that enters next lamina (see a picture 7) . Although two kinds machine plan to all can complete the copy work of the circle outside blade and hub, but when adopting plan of the first kind of treatment, integral impeller is installed and search to comparing difficulty, and the load that brings to bear on on main shaft of numerical control revolving stage will make main shaft generation is out of shape certainly, affect fixed position precision thereby; And when adopting plan of the 2nd kind of treatment, do not need have the aid of to rotate at special numerical control revolving stage impeller, avoided the deflexion effect that gravity of integral impeller oneself causes to revolving stage thereby. Consider above factor integratedly, first choice machines plan the 2nd kind. Before Nextpage electrode carries movable mould plans to undertaking electric spark machines an experiment, need undertakes electrode motion imitate, with the appears possibly problem in prescient and effective treatment, reduce the odds that integral impeller discards as useless. According to designs electrode motion contrail, use SolidWorks animation motion to consider exemple module setting linear and motor to mix rotate motor, drive electrode moves, undertake machining emulation. The electrode when be being machined through observing individual lamina by initiative position (see a picture 8) move to terminate the position (see a picture 9) whole exercise process, can in time discover the interference circumstance of electrode and integral impeller. If produce interference, the athletic contrail that needs to install electrode afresh perhaps redesigns electrode, till till emulate,the electrode in the process and integral impeller do not produce interference. Figuration electrode makes the production method of figuration electrode basically have the following kinds: Law of machining law, figuration of accurate casting, pulverous metallurgy and patterning method of electric spark line. The advantage of machining law is the treatment that completes electrode through mechanical milling, can machine the electrode of complex form, defect is periodic long, cost is high; Although accurate casting saves stuff, but process cost is high; Although law of pulverous metallurgy figuration is periodic short, but processability of electrode electric spark can be low; Cut of electric spark line uses pulse scintilla discharge to produce corrode of local instant high temperature to remove material, electrode and workpiece belong to blame contact treatment, have macroscopical active force hardly, the electrode precision that treatment comes out is tall. Integral impeller material employs high temperature alloy, consider stability of electrode loss, treatment and treatment rate integratedly, choose red copper to regard electrode as material. Because use machining law stress bigger, electrode arises easily be out of shape, the article chooses the method of cut of electric spark line with stress is little and tall precision. If the graph is shown 10 times,electrode line cut machines sketch map. Use machine tool of cut of silk thread of don't go yet to complete all process that electrode machines. To improve the production efficiency of electrode, managing electrode material, can machine many electrode, undertake permutation assorted to electrode according to the appearance of electrode. Above all, use machine tool of cut of silk thread of don't go yet to become cut of electrode semifinished product the cuboid figure that the graph shows 10 times, complete the treatment of datum plane of each fixed position. Next, treatment wears filar aperture. Before electrode of cut of silk of follow-up don't go yet, need machines the aperture that wear silk in the intermediate position of the aperture inside electrode. Next, by the graph 10 show installation electrode semifinished product, direction of semifinished product length and X axis are parallel, width direction and Y axis are parallel, the electrode that finish face is machined. Finally, circle semifinished product X axis to rotate 90 ° , fixed position searchs, face of the circle outside cut hub and datum plane of electrode fixed position, the electrode that finish is machined. Use in electrode face treatment " cut repair 3 " treatment craft, namely line cut finishs those who need treatment 3 times model face, the surplus with major purify of cut of first time line, purify of cut of the 2nd line the surplus of ten μ M, undertake light makes treatment the 3rd times, purify the surplus of M of a few μ , acquire good exterior quality. The production precision of electrode affects the figuration precision of integral impeller directly, accordingly, after electrode treatment is finished, answer crucial dimension to undertake detecting. Measure to the precision of electrode face, can use 3 coordinate to measure machine is special perhaps complex model face precision detects equipment undertakes detecting, the contact that also can use electric spark to machine a machine tool feels a function to undertake detecting to electrode face precision. The electrode after classics precision certificate of proof uses special unit to undertake saving as far as possible, reach in order to prevent electrode in move process deposit a process to be out of shape mediumly problem, and accomplish electric imponderability take put down gently, assure the precision stability of electrode. Impeller of last word whole because its material be hard to cutting, lamina range is sophisticated wait for an element, its machine the difficult problem that is mechanical manufacturing industry all the time. The article is aimed at the structural characteristic of blade, tie theory of model of complex curved surface, used SolidWorks software to undertake integral impeller modelling studies. Form easily in the light of fission electrode build receive the defect with low precision of figuration of step, lamina, designed the integral type electrode that suits integral impeller treatment, this electrode has precision of blade face figuration tall, the sources of energy uses up low good point. Through driving whole to A axis revolving stage impeller rotates and C axis drives electrode to rotate two kinds of different treatment program have trade off study, reach axis of first choice C drives electrode to rotate the conclusion that machines plan. Carry through electrode movable mould drafts, test and verify the validity of established motion contrail, the electrode in avoiding to machine a process thereby cuts integral impeller what interfere a circumstance namely to happen too. Finally, introduced the treatment method of electrode of cut of silk thread of don't go yet, use electrode to become group of production methods managing electrode material, improved the production efficiency of electrode. CNC Milling