The crucial technology of process designing of CNC Machining of spare parts of large sculpture curved surface

Of Energy&Environmental Engineering, xihua University, chengdu 610039, sichuan) Abstract: Multi-axis NC Programming Is One Of The Most Important Tasks In Machining Of Large Parts With Sculptured Surfaces.

In This Paper, the Key Technology For NC Programming In 5-axis Machining Of Large Sculptured Surfaces Is Introduced, which Includes The Tool Path Generating, cutting Simulation, machining Process Simulation And Post-processing In The Programming.

Combining These Research Works With 5-axis NC Programming In Machining Of Hydraulic Turbine ' S Blades, the Developed Technology Has Been Widely Applied In Machining Of Large Hydraulic Turbine ' S Blades As A Programming Tool.

Key Words: NC Programming; CAM; NC Machining; Surfaces Machining 1.

Foreword is large the CNC Machining of sculpture spare parts is a very formidable task, if lamina of large hydraulic turbine, airscrew lamina is,by much Zhang Diao model curved surface comprises close spare parts of curved surface body, its machine an area to arrive from a few square metre tens of square metre. Using CNC Machining of 5 axes linkage is current the most effective treatment method, but the 5 axes linkage that general CAD/CAM software perhaps can not solve part of curved surface of this kind of complex sculpture well completely machines process designing problem [1] . The CNC Machining process designing of spare parts of large sculpture curved surface is one of crucial technologies that implement its digitlization to make [2] , it involves geometry of technology of treatment technology program, computer, maths, computation, differential geometry, artificial intelligence to wait for the knowledge of numerous course domain, process of process designing of its numerical control is emulation evaluation of a digitlization and optimized process. The numerical control process designing of spare parts of sculpture curved surface is to be on geometrical modelling and the foundation that machine technology program, the knife undertakes on the computer orbit computation, emulate, optimize and test and verify machines a process, satisfy 5 axes linkage to process the order of high quality CNC Machining of the requirement with be being generated effectively. Process designing of CNC Machining of spare parts of large sculpture curved surface involves the technology of many sided, its key technology includes [1-5] : The three-dimensional geometry modelling of ① sculpture curved surface; ② basis the sexual condition of curved surface of each pieces of sculpture on the spare parts, undertake a knife reasonably orbit program and computation; ③ cutting is emulated with cutting tool interference examines; Motion of ④ machine tool is emulated with collision interference examines; The postposition that ⑤ machine tool moves alternates; 2.

The process designing of CNC Machining of 5 axes linkage of spare parts of large sculpture curved surface compares the technological process of process designing of CNC Machining of spare parts of large sculpture curved surface process designing of treatment of general spare parts is complex much, basically use means of process designing leaving a line. To assure the dependability of CNC Machining program, use commonly in the light of specific treatment object characteristic and requirement, undertake in current CAM software development will finish a knife 2 times orbit computation, cutting is emulated with the machine tool motion is emulated. Although spare parts of each specific sculpture curved surface has alone characteristic, but process of the process designing in the CNC Machining of this kind of spare parts agrees basically. With large lamina kind the spare parts is exemple [2] , if the process designing process that we are in those who undertake developing coming true on SDRC/ Camand® software pursues 1 is shown. 3.

Large sculpture curved surface the knife of CNC Machining of 5 axes linkage the knife that orbit generates CNC Machining of 5 axes linkage orbit computation is a very serious problem in treatment of spare parts of large sculpture curved surface, good to obtain surface quality is led with tall treatment effect, ask the curved surface appearance of different on the spare parts area needs to take the treatment kind that suits to it. The law of unripe set prescription of cutting tool contrail of high quality is divided outside should assuring process designing precision and experience of have nothing to do with, should satisfy versatility at the same time tall, code measures efficiency of good, treatment small wait a condition a moment. To the much axis linkage of sculpture curved surface Duan Xi is machined, all use cut treatment way all right, all sorts of travel cut treatment way all but the treatment problem that end is the curve on curved surface, put forward how to generate correct knife according to the curved surface of treatment so the problem of orbit. Generate digit of knife of experience of have nothing to do with to plant according to basically having the following by curved surface model method: → of curved surface model does not have data of CL of → of interference CC data; Data of CL of → of model of polyhedron of → of curved surface model; → of curved surface model slants data of CL of → of buy side model; → of data of CC of → of curved surface model does not have interference CL data. Classics analysis, the 5 axes linkage in large sculpture curved surface uses kinds of method to generate knife digit to occupy commonly in treatment, its knife digit occupies the flow that if the graph is shown 2 times,generates a course. 3.

The knife that linkage of 1 5 axes machines the characteristic of each pieces of curved surface that orbit plans to be aimed at spare parts of sculpture curved surface, undertake reasonable knife orbit program and computation, it is efficient below the premise that assures to machine quality to ask one of techniques that process a large part key. The knife that is like large lamina CNC Machining in orbit program, the fluid motive force that should consider blade above all is characteristic, decide and optimize cutter track diameter. The 2nd pace should design a requirement according to geometry of blade curved surface, control and reasonable allocation error [3] , use the appearance of cutting tool geometry that suits each curved surface and parameter, reasonable and affirmatory pace taking a knife grows and walk along computation of knife row spacing to give cutting tool to cut touch (CC) the data of the dot. Treatment of large curved surface can use the CC contrail that waits for law of leftover height program to search computational photograph adjacent, finish computation of knife row spacing. The knife in large sculpture curved surface want to control machining error strictly already in orbit program, want to improve treatment efficiency as far as possible again. Current CNC system is average when 5 axes linkage is controlled function of interpolation of only wired sex, and the linkage rule of each rod that 5 axes linkage processes is complex nonlinear relation, in CAM system, by bow tall error is decided machining error and feed condition are chief approximately, and swing without what consider rotor the length influence to machining error [3] . In treatment of additional explicit and large lamina, of rotor swing length is average opposite bigger, these are nonlinear it is important that the error machines treatment blame to be to large sculpture curved surface [3] , can use a consideration three-dimensional nonlinear the error will be calculated knife condition is chief [2] . The 3rd pace, should distributing according to the curvature of each curved surface circumstance, way of affirmatory and logical knife axle control, vector of computational cutter shaft, realize knife of 5 axes linkage orbit computation. 3.

The Normal > is in the process of curved surface of CNC Machining of 5 axes linkage, cutter shaft vector is be in by the definition knife the local coordinate on orbit is (Frenet coordinate is worn) Nok="f" Gradientshapeok="t" O:cOnnecttype="rect"> (heel part) and (place corner) two angle will decide [2] . At that time, hang down for cutting tool axis the fashion carrying mill that consists the surface, at that time, for parallel of cutting tool axis the side mill means at machining the surface. Means of knife axle control is a when affect 5 axes linkage to machine the effect main factor, its decide the principle is to achieve tall cutting efficiency, the exists possibly cutting tool in considering to machine at the same time interferes a phenomenon. Additional, it waits to the state getting power of the cutting life of cutting tool, machine tool influential. Pilot of the cutter shaft in treatment of 5 axes linkage is top the state is to have what change along with curved surface to get used to ability oneself, first-rate is obtained to machine the effect below the premise that averts interference. As a result of the complexity of the problem, be in commonly in current CAM system means of treatment of mill of end of 5 axes linkage provided Sturz means, namely manual input secures dip angle, the 5 axes linkage that how decides these two angle become sculpture curved surface machines a knife problem of orbit calculative key. Normal > machines a knife in the 5 axes linkage of spare parts of sculpture curved surface when computation, according to the characteristic that each pieces of curved surface machines, decide its command two point of view of the attitude of cutter shaft. Effective treatment makes clear, with the value too big, reduce treatment efficiency not only, and worsened the cutting condition of cutting tool. To the curved surface of small curvature, use milling cutter of big diameter face, need to adjust only commonly can. Because this is in actual project, to improve computational efficiency, when deciding cutter shaft vector, the interference that can take no account of arbor and curved surface of whole spare parts first (collision) circumstance an underside of consideration bit body and the interference that treatment nods surface of around local treatment (gnaw cut) circumstance, its can simplify by what be as follows methodological computation is affirmatory [2] . Normal > simplifies the cutting tool model of current treatment cutting tool to be equal to the upright milling cutter that radius of effective cutting tool is for radius, the differential geometry structure that sets treatment surface nods the surface for sunken ellipse (machine the surface namely advocate curvature and be more than 0) , milling cutter and treatment surface are cut touch nod at CC, in CC the dot builds local coordinate department, set and be in CC point point to machine the surface respectively the law curvature of edge direction and direction. Take, pass derivation analysis, should bit body and cut contact between small area hands-off, the heel part of cutting tool should satisfy: Normal > ... ... ... ... ... ... ... ... ... ... (1)normal > because the effective cutting radius of cutting tool is the change that follow and change, take: Normal > ... ... ... ... ... ... ... ... .

(2)normal > is analysed according to machining exterior curvature to calculate [the local sex condition of 2] affirmatory curved surface, outside hollow elliptical site, the double music point, hollow site that throw thing can be pressed on form calculation, to protruding the dot that throw thing and protruding ellipse are nodded, take: Can. 4.

The CNC Machining of large sculpture curved surface emulates Normal > is large the form of spare parts of sculpture curved surface is complex, although be opposite when numerical control process designing program of modelling of each pieces of curved surface, technology, knife the respect such as processing of program, postposition made very careful work, but the CNC Machining program that still cannot ensure place is generated is nonexistent any problems. The problem that produces possibly among them has: In machining a process cut too with owe cut, each motion component and spare parts mix arbor and connection system and spare parts, machine tool the interference between clamping apparatus collides, and of cutting tool of the cutting in machining a process cross bear to wait. In process of CNC Machining of spare parts of large sculpture curved surface, these problems often deadly, attaint machine tool, cutting tool and workpiece, cause huge loss thereby. Accordingly, machining a knife orbit or after the program is generated, must undertake examining to its validity, the problem that exists in the light of its undertakes modification, till the part program that forms qualification. To treatment of spare parts of large sculpture curved surface, the geometry that includes cutting course is emulated and machine tool motion is emulated. Undertake cutting process is emulated above all, check those who machine the lamina in the process to be cut too with owe cut. For the safety of machine tool and lamina, undertake machine tool motion is emulated further in case collision of component of machine tool motion and arbor interference is special must. Collide like the discovery in emulating and interfere, must revise treatment program to perhaps machine a method. CNC Machining of spare parts of large sculpture curved surface is a very complex process, pass the emulation treatment on the computer, can revise repeatedly perfect seek sound treatment technology program, optimize treatment program, the geometrical parameter that optimizes cutting tool and cutting parameter. Normal >CNC Machining emulation technology is the true treatment process blade map has in fictitious treatment environment, ask to adoption numerical control machine tool, treatment semifinished product of cutting tool, part reachs clamping apparatus to wait for real treatment environment to undertake map construction goes out above all emulate (fictitious) treatment environment. CNC Machining copy is to pass software imitate to machine method of environment, cutting tool and material resection procedure really, achieve the goal of process of imitate CNC Machining thereby. In the technology of CNC Machining of 5 axes linkage of the lamina of runner of large hydraulic turbine that develops in us, considering blade complexity of calculative of treatment of 5 axes linkage and project ask actually to machine a process to emulate calculative high reliability. Undertake on SDRC/Camand® and CGtech/Vericut® development will realize lamina of large hydraulic turbine to machine a process to emulate a function to ask, and realize a knife orbit computation and treatment process copy are compositive really. Knife the geometry that after orbit is generated, can undertake machining a process directly is emulated. This function of emulation system is shown 2 times like the graph, in should emulate an environment, the crucial geometry information of the machine tool in using numeric algorithm to get treatment course, cutting tool and spare parts, carry pair of swords (CL-Data) file or the interpreter of NC program, extraction gives statement of drive of treatment process motion, the basis is given time set is removed, make system of cutting tool scanning, through cutting tool scanning body and operation of spare parts model reflect the cutting process of the spare parts. Perfect through should emulating a system to be able to be revised repeatedly seek program of reasonable treatment technology, optimize treatment program, the geometrical parameter that optimizes cutting tool and cutting parameter, this already became a project the checking program in process of process designing of CNC Machining of actual and large lamina and optimize the step with treatment necessary program. If pursue 3 it is to hydraulic turbine of type of one large mixed flow blade undertakes cutting is emulated, if pursue 4 it is to one large shaft lamina of hydraulic turbine drifting type undertakes interference examines cutting a machine tool to move colliding emulate, emulate machine on center of CNC Machining of movable type of large dragon door. 5.

The postposition commutation Normal > is a of technology of process designing of CNC Machining of spare parts of sculpture curved surface serious content, it will before narrate generated knife digit to agree with according to be being changed the athletic data of particular machine tool and CNC Machining program. Technical content includes its key: The machine tool is kinematic build model and beg error of structure of solution, machine tool motion of compensation, machine tool is nonlinear error school nucleus is amended, the nucleus amends the smooth sex school that the machine tool moves, nucleus of feed career officer is amended reach code changeover. Accordingly, effective postposition handles the treatment quality to assuring blade, efficiency and machine tool to move reliably have main effect. Those who need a specification is us center of adoption CNC Machining of movable type of large dragon door is the heart home made product at the beginning of 90 time, the system of numerical control of Sinumerik 880M CNC of configuration does not have G93 (speed of constant surface feed) instruction, the quality of curved surface surface that to 5 axes linkage treatment gives has relatively serious effect. According to speed of exterior cutting feed it is a machine tool the principle of result of complex of each axis motion, through postposition computation undertakes handling making this problem gets understanding definitely. 6.

Normal > is with the CNC Machining of 5 axes linkage of lamina of large hydraulic turbine exemple, in the consideration treatment asks to undertake foundation of formative of geometry of blade curved surface go up, combinative aforementioned theory considers to undertake developing in SDRC/Camand® software, we realize large lamina the knife of CNC Machining of 5 axes linkage orbit computation and treatment are emulated, the process designing tool that already regarded large lamina as CNC Machining of 5 axes linkage is used in the effective treatment of many projects. If pursue 5 for CNC Machining of lamina of hydraulic turbine of 3 gorge power station. The laryngeal diameter of runner of type of this mixed flow is Nok="f" Gradientshapeok="t" O:cOnnecttype="rect"> , weight is 460000kg, it is the runner of the biggest mixed flow type on eye preexistence bound. Blade is typical " X " model lamina of mixed flow type, of blade most Xiaobao allows body to be: 5500 (long) ´4650 (wide) ´1900 (tall) Mm, weight of every lamina semifinished product makes an appointment with 29000kg left and right sides, the weight after blade finish machining is 18700kg, the treatment area of every lamina is 40.

2. Those who use milling cutter of curved surface face to undertake milling cutter of face of thick mill, curved surface has half essence mill and blade of mill of essence of life, rear. Use the leftover height such as 5 axes to machine means to machine blade, rear. In same precision the requirement falls, compare through computation, use the knife that waits for leftover height computation to wait for parameter law mediumly than using CAM orbit overall length reduces nearly 15 ％ , rose greatly to machine efficiency. 7.

Last word Normal > large sculpture is generating electricity in the industry such as equipment, car, plane, mould by wide application, process designing of its CNC Machining is this kind of spare parts creates one of medium difficulty problems. The process of numerical control process designing that the article machines spare parts of large sculpture curved surface in the light of 5 axes linkage, reasonable knife orbit program and computation, cutting is emulated, machine tool motion is emulated, the crucial technology such as postposition commutation undertook study to develop. In be being machined in the light of large sculpture curved surface, want to control machining error strictly already, want to improve treatment efficiency as far as possible again, put forward to be being calculated 5 axes linkage machines a knife when use wait for leftover height knife program, consider three-dimensional nonlinear the error will be calculated the knife with knife chief condition orbit creates strategy. Analysis and the knife axle control in deciding 5 axes linkage machines spare parts of large sculpture curved surface are given and calculate method. Combine lamina of large hydraulic turbine requirement of technology of CNC Machining of 5 axes linkage, undertake developing on SDRC/Camand® , the process designing environment that tectonic lamina CNC Machining emulates, the knife of the CNC Machining of 5 axes linkage that realizes large runner lamina orbit computation and treatment are emulated. The process designing tool that already regarded lamina of large hydraulic turbine as CNC Machining of 5 axes linkage is used in actual production. CNC Milling CNC Machining