Processing technique of mould high speed and strategy
- source:FINKEL CNC Machining
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