Processing technique of mould high speed and strategy

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Summary: Summed up high speed processing technique to make medium application in the mould, introduced mould high speed to machine the requirement of system of pair of machine tools, numerical control and cutting tool, the craft of high speed treatment that analysed a pattern mainly and strategy taking a knife. The high speed processing technique that 1 foreword regards the mainest general character in contemporary and advanced production technology as one of technologies represented the development way that cutting machines, make the mainstream technology that cutting machines gradually. In high speed cutting " high speed " it is an opposite concept, to different treatment kind and workpiece material, the cutting rate that uses when high speed cutting is not same. Generally speaking, the cutting rate that high speed cutting uses is higher than groovy cutting speed 5 ～ 10 times above. Because the application of technology of high speed cutting can heighten treatment effect significantly,be led and treatment precision, reduce cutting force, reduce intensive of working procedure of the influence of heat in metal cutting to workpiece, implementation to change etc, because this already was made in aerospace, mould, the car is made, the domain such as accurate machinery gets applied extensively, obtained good technical economic benefits. Make in the figuration of contemporary mould in, because the shape face design of the mould is complex with each passing day, place of free curved surface occupies scale to increase ceaselessly, because this raised taller requirement to mould processing technique, should assure tall production precision and exterior quality not only namely, and what should seek treatment appearance is beautiful. As ceaseless to the research of high speed processing technique development, machining what the relevant technology such as software of system of machine tool, numerical control, cutting tool system, CAD/CAM develops ceaselessly to drive especially below, high speed processing technique applies increasingly already at the production treatment of the mould. High speed processing technique machined craft to produce tremendous effect to the mould, changed traditional pattern treatment to use " grinding of heat treatment → of → of treatment of anneal → milling " or " manual burnish of → of electric spark treatment, polish " wait for complex and lengthy technological process, treatment of cutting of usable even high speed replaces original whole process. High speed processing technique divides the applicable immediate treatment at strong pattern of temper by dipping in water antrum (especially semifinishing machining and finish machining) outside, in EDM electrode treatment, sudden appearance make wait for a respect to also get applied extensively. Mass-produced practice makes clear, the manual and abrade time of 80% is restricted in applying technology of high speed cutting to be able to save mould follow-up to machine, charge of managing finished cost is close 30% , mould surface machines precision to be able to amount to 1µm, efficiency of cutting tool cutting can raise one times. The oneself characteristic of the characteristic that because the mould is machined,2 moulds high speed machines the requirement to processing a system and high speed processing technique, the relevant technique that processes to mould high speed and machining complex (system of treatment machine tool, numerical control, cutting tool) put forward to machine higher demand than traditional pattern. The main shaft function of machine tool of high speed of machine tool main shaft is the fundamental condition that realizes treatment of high speed cutting. The rotate speed limits of main shaft of machine tool of high speed cutting is 10000 ～ 100000r/mim, ask main shaft is had rise quickly fast, the function that showing emplacement allows to stop quickly (have extremely tall horn to add decelerate to spend) namely, because main shaft of this high speed often uses a liquid static pressure bearing type, air is static press type of bearing of in suspension of bearing type, magnetism to wait for configuration. System of machine tool drive is the need that contented mould high speed machines, the drive system that processes a machine tool should have following character: High feed rate. Consider to make clear, to small diameter cutting tool, raise rotate speed and every tine feed to be helpful for reducing cutting tool to wear away. At present commonly used feed speed limits is 20 ～ 30m/min, if use transmission of guide screw of big lead ball, feed speed can amount to 60m/min; Use linear electric machinery to be able to make feed speed achieves 120m/min. Tall acceleration. To the high speed of profile of three-dimensional and complex curved surface treatment asks drive system has good acceleration character, drive system acceleration should achieve 20 ～ 40m/s2. High speed gain factor (Velocity Gain Factor)Kv. To achieve precision of taller three-dimensional outline trends and the smallest lag, 30(m/min)/mm of ～ of Kv=20 of factor of gain of general requirement speed. The numerical control system with numerical control advanced system is to make sure the pattern is mixed the crucial factor of quality of treatment of curved surface high speed and efficiency, cutting of mould high speed machines logarithm to accuse main demand of the system to be: High-speed number dominates return circuit (Digital Control Loop) . Include: 32 or 64 processor and 1.

The hard disk of 5Gb above; Cutty is linear time of electric machinery sampling (<500µs) ; Of speed and acceleration before make a present of is controlled (Feed Forward Control) ; The crawl of digital drive system is controlled (Jerk Control) . Advanced interpolation method (the batten interpolation) that is based on NURBS, in order to obtain good exterior quality, exact size and tall geometrical precision. Pretreatment (Look-ahead) function. The requirement has register of high capacity amortize, can be read beforehand and check many block (if DMG machine tool can amount to 500 block, simens system can amount to 1000 ～ 2000 block) , so that be being machined exterior figure (curvature) when producing change can adopt the measure such as change feed speed in time to wait with avoiding to cut. The error compensates a function. The hot error compensation that because the hair thermal conductivity such as linear electric machinery, main shaft is sent,includes, quadrantal error compensation, measure systematic error compensation to wait for a function. In addition, the demand that treatment of cutting of mould high speed transmits speed to data is very high also. The transmission speed that traditional data interface is like RS232 serial mouth is 19.

2Kbps, and a lot of advanced machining center already all used aether local area network (Ethernet) undertakes data is transmitted, speed can amount to 200Kbps. The main development trend of system of cutting tool of cutting of high speed of system of cutting tool of high speed cutting is the knife handle of type of double fixed position that hollow awl ministry and main shaft end panel contact at the same time (the) such as the KM knife handle of company of Kenamental of the HSK knife handle that is like German OTT company, United States, precision of its axial fixed position can be amounted to 0.

001mm. Below the centrifugal force effect that rotates in high speed, knife clip locking is more firm, its are radial and jumpy do not exceed 5µm. With the cutting tool data that processes at high speed cutting basically hard alloy, pottery and porcelain, cermet, cubic nitrogen changes boron (PCBN) , get together brilliant diamond. To satisfy the requirement that mould high speed machines, the respect such as the development of structure of the research that the development of cutting tool technology basically centers in new-style coating material and coating method, new-style cutting tool. Appearance of outline of the workpiece when 1 rough machining is opposite craft of treatment of 3 moulds high speed and plan delineation the affects rough machining of rough machining mould main goal of cutting tool load is the material purify rate inside pursuit unit time, prepare the geometrical outline of workpiece for semifinishing machining. The graph shows the effect of appearance of outline of the workpiece in be rough machining process to cutting tool load 1 times. See by the graph, because of cut metal in cutting process area happening changes, bring about load of cutting tool susceptive to produce change, make cutting process not stable, cutting tool wears away speed is inhomogenous, treatment surface quality drops. A lot of CAM software that develop at present can carry cutting condition through the following measure constant, acquire good treatment quality thereby. Constant cutting load. Achieve constant cut area and material purify rate through computation, make cutting load and cutting tool wear away rate keeps balanced, in order to improve cutting tool life and treatment quality. Avoid to change way of cutting tool feed suddenly. Avoid workpiece of cutting tool embedded. When be like treatment mould antrum, should avoid cutting tool perpendicular insert workpiece, and should use tilt means leaving a sword (commonly used banking angle is 20 ° ～ 30 ° ) , had better use the knife below screw type in order to reduce cutting tool load; When machining mould core, answer to cut work from the level after Dao Ran of the following outside workpiece first as far as possible. Cutting tool is cut, bend inclined should be used as far as possible when cutting a work (or circular arc type) cut, cut, avoid perpendicular cut, cut. Use climb cutting climbing type (Climb Cutting) can reduce heat in metal cutting, reduce cutting tool to get force and treatment sclerosis rate, improve treatment quality. The main goal of semifinishing machining of semifinishing machining mould is to make level off of workpiece outline appearance, surplus of exterior precision work is even, this is attached most importance to especially to tool steel mould should, because it will affect the change of the change of area of cut of the cutting tool when finish machining and cutting tool load, affect the stability of cutting process and quality of finish machining surface thereby. Rough machining is to be based on volume model (Volume Model) , finish machining is to be based on scale model (Surface Model) . And the CAD/CAM system that develops before is discontinuous to the geometrical description of the spare parts, after because do not have,describing rough machining, the intermediate information that the model processes before finish machining, the odd mental allowance of surface of reason rough machining distributings reaching the biggest odd mental allowance all is sealed. Because this answers,strategy of half-and-half finish machining makes optimizing have even odd mental allowance in order to assure surface of the workpiece after semifinishing machining. Optimize a process to include: The the computation of outline of rough machining rear wheel, computation of the biggest odd mental allowance, biggest the deciding that allows mental allowance, right odd mental allowance is more than the biggest allow mental allowance model face partition (the area that is less than radius of rough machining cutting tool like the radius blend such as groove, corner) and semifinishing machining. Existing mould high speed machines CAD/CAM software to have odd mental allowance to analyse a function mostly, can reach distributinging circumstance to use sound semifinishing machining strategy according to the size of odd mental allowance. If the Hyper Mill of Open Mind company and Hyper Form software offerred bunchy milling (Pencil Milling) and odd milling (the method such as Rest Milling) will keep clear of the odd mental allowance is bigger corner after rough machining in order to assure the mental allowance with follow-up even working procedure. The local milling of Pro/Engineer software (Local Milling) has similar function, the odd mental allowance that is like local milling working procedure takes value and rough machining equal, this working procedure keeps clear of only with milling cutter of a small diameter the corner that rough machining did not cut, undertake semifinishing machining again next; If take the odd mental allowance of local milling working procedure,the value serves as the odd mental allowance of semifinishing machining, criterion this working procedure can keep clear of not only the corner that rough machining did not cut, return achievable semifinishing machining. Graph the treatment of 2 combination curved surface pursues of 3 feed speed optimize the high speed finish machining that adjusts finish machining pattern strategy depends on the osculatory dot of cutting tool and workpiece, and the contact of cutting tool and workpiece nods the curved surface slope as treatment surface and cutting tool to have effect radius change and change. Machine to the complex curved surface that be combined by many curved surface and becomes (2) seeing a picture, answer to have successive treatment in a working procedure as far as possible, is not right each curved surface undertake machining respectively, carry in order to decrease the frequency of next knife, knives. However the change as a result of slope of the surface in treatment, if define the side penetration of a cutting tool of treatment only,measure (Step Over) , cause what differ in slope possibly apparently actual step pitch is inhomogenous, affect treatment quality thereby. The method that Pro/Engineer solves afore-mentioned problems is to be in while definition side penetration of a cutting tool is measured, define height of area of treatment surface remain again (Scallopheight) ; Hyper Mill was offerred wait for step pitch to machine (Equidistantmachining) means, can assure the amount of even side penetration of a cutting tool between cutter track diameter, and the restriction that does not accept exterior slope and curvature, make sure cutting tool bears from beginning to end in cutting process even load. Usually, 1 what the curvature radius of finish machining curved surface should be more than cutting tool radius.

5 times, in order to avoid the abrupt change of feed direction. In the high speed finish machining of the mould, cutting every time, when cutting a work, the change of feed direction should use circular arc as far as possible or the curve turns receive, avoid to use turn point-blank receive, in order to maintain the smooth stability of cutting process. Of feed speed optimize what at present software of a lot of CAM has feed rate adjust a function (like the graph 3 show) : In semifinishing machining process, lower feed rate when cut area is large, and cut area hour increases feed rate. Those who use feed rate optimize adjust can make cutting process smooth, improve treatment surface quality. The size of cut area is calculated automatically completely by CAM software, the adjustment of feed speed can be installed by the user according to machining a requirement. Processing technique of high speed of 4 epilogue mould is a variety of advanced processing technique is compositive, involve high speed to machine craft not only, and still include high speed to machine cutting tool of cutting of system of machine tool, numerical control, high speed and CAD/CAM technology to wait. Processing technique of mould high speed already was at present in the mould manufacturing industry of the developed country general application, and the applied limits that is in our country and applied level still remain to rise, develop energetically and processing technique of high speed of promotion application mould is right of level of technology of whole of manufacturing industry of mould of stimulative our country and economic benefits rise have important sense. CNC Milling