The high speed hard milling of the mould
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03 ～ 0.
The catalogue item that the hard alloy of 1mm establishs milling cutter to already included a few manufacturer) the application of development and imperceptible milling craft, this makes a few narrow it is completely OK to seam an internal angle with dinky radius will undertake machining through using small diameter to establish milling cutter, the applied limits that causes electric spark treatment narrows further. According to German Frauhofer manufacturing technology institute was opposite 2004 tool and pattern company place undertake seek advice make clear, henceforth a few years (to 2008) high speed hard milling machines the place in craft to occupy portion to will grow 20% in tool and mould, and electric spark treatment will decrease 12% . This shows, craft of high speed hard milling gains more and more ground popularizing in mould manufacturing industry, craft of hard mill of this kind of high speed already made the critical process that the mould machines. Although treatment of high speed hard milling is made to the mould bring a lot of profit, but should use this kind of technology fruitfully, the enterprise must want to have certain requirement. Namely the enterprise is due the process designing personnel of taller profession quality and seasoned technologist and hep treatment craft, want to appropriate high speed machines a machine tool, should deploy agree with the knife mix that has high speed hard mill, cutting tool and choose reasonable cutting parameter to wait. The quality of professional and experience are the manufacturing technological process that fundamental premise optimizes a mould, aim to reduce treatment working procedure and improve treatment quality, using technology of high speed hard mill apparently is this kind of optimized main avenue. High speed is machined and the hi-tech such as CAD/CAM system means the high investment on treatment equipment not only, and still need to have the rich industry experience, professional that can solve actual production difficult problem. Want to rely on the personnel of hep production technology, according to the geometrical appearance of the mould, material the demand such as qualitative, hardness and precision makes reasonable manufacturing technological process. Here, the choice of hard mill craft, electric spark machines accept or reject, cutting tool form, norms and amount, cutting dosage is decided really, adopt when treatment why to plant the work out of cooling and lubricant means and NC program, quality of the manufacturing efficiency that machines the influence to the mould, treatment and production cost. A few moulds produce an enterprise to still lack practical experience in respect of craft of high speed hard mill, if some enterprises did not pass machine tool of 3 axes linkage,use experience accumulate and purchase machining center of 5 axes linkage directly. Except recruit and groom outside professional, undertake with works of machine tool manufactory, tool and professional research organization collaboration is an important way. In mould treatment, it is very important also to optimizing process to undertake necessary craft experiments. For example the model noting model of manufactory of a toy of our country, machining a machine tool is machining center of vertical of C800V of German Hermle company, use 9 different types establish milling cutter and ball head milling cutter, add man-hour to use large flow refrigeration to lubricate, handling time is 125 minutes. To make the decorative pattern pattern of modelling antrum bottom, want to undertake electric spark is machined then after milling is machined. The heart in the basis " the high speed in be being made with the mould in Chinese tool is machined " research project, to optimize the manufacturing technological process of this mould, the manufacturing management of university of German Darmstadt industry, craft and machine tool institute (PTW) the C30U machining center that is in Hermle company is aspirant went milling experiments, the treatment of the decorative pattern design of mould antrum bottom plans to pass craft of mill of high speed essence to replace electric spark to machine. Test result makes clear, at present treatment needs to use 6 cutting tool only, reduced 3 cutting tool, such, outside eliminating cost of economic cutting tool, still decreased to change knife time, reduced the auxiliary time of 30% thereby, whole handling time needs 99 minutes only, handling time is compared decreased formerly 26% . Add man-hour to use minim to lubricate, reduced cutting tool to wear away. Because discharged electric spark to machine (also omit electrode is made) , make the exterior surface roughness of decorative pattern design was reduced 50% , the loss that also avoided to machine the pattern that create to machine surface layer by electric spark at the same time (white layer) . Machine tool, cutting tool and knife clip are important assure for efficient the hard mill treatment that has a pattern with high quality ground, have very high demand to machine tool, cutting tool and knife clip. (1) the high speed machining center that the machine tool uses is due higher main shaft rotate speed, great power, tall tigidity, high dynamic performance and good damp character, and the control system with fast stock. Current, machine the high speed machine tool of the mould, main shaft rotate speed all is in commonly 40000 ～ 42000 (R/min) , like Mikro company HSM400 of center of milling of generation high speed, HSM700 is mixed the HSM600u of the 2nd generation (center of milling of high speed of 5 axes linkage) , the DMC100V of DMG, the C800V of Hermle (36000r/min) , the 700GC of Digma, 850HSC, the Hi-Dyn of the RFM 600 of Rers and PTW (60000r/min) wait. Such main shaft rotate speed basically can satisfy milling cutter of commonly used small diameter (2 ～ 12mm) treatment need. But the milling cutter to smaller diameter (0.
2 ～ 1mm) , such main shaft rotate speed cannot make cutting tool achieves good cutting rate. For example, should use 160m/min.
when cutting speed, the milling cutter that is 1mm to the diameter needs 51000r/min.
main shaft rotate speed; And to 0.
The milling cutter of 2mm, need to be as high as the rotate speed of 250000r/min, and in main shaft top rotate speed falls for the circumstance of 42000r/min, can part to undertake milling with the cutting speed with 132m/min and inferior 26m/min only to two kinds of afore-mentioned milling cutter. The exemple treatment like model of a gear, diameter of adoption the smallest milling cutter is 0.
2mm, machine tool main shaft is highest rotate speed is 40000r/min, can achieve the cutting rate with so low 25m/min only right now. Accordingly, to get used to the development of imperceptible cutting, need develops the machine tool of higher rotate speed. Nextpage is current, high speed machines the axial acceleration of the machine tool to amount to 1 ～ 2g commonly, have individually achieve 3g (the HPM800 of Mikron) . Taller axial acceleration, mean a machine tool to have taller dynamic property, below the circumstance that direction of this free curved surface in treatment mould, feed changes ceaselessly, still can carry the feed rate of setting. Be helpful for improving the treatment precision of mould freedom curved surface and exterior quality thereby, forecast according to industry public figure, the axial acceleration of the machine tool is in recent 3 ～ are expected to achieve 3 ～ 5g inside 4 years. Although machining center of high speed of 5 axes linkage wants to compare machine tool of 3 axes linkage on the price a lot of taller, but it suits to use those who machine complex curved surface particularly model antrum. Machining deeper model when antrum and clear to protruding stage root, can pass additional two rotor (through torsion electric machinery the C axis of direct drive is mixed B axis, can offer as suitable as linear axis be equal to acceleration and feed speed) synchronous motion can be used thereby dangerous extend shorter establish milling cutter, enhanced cutting tool tigidity from this, avoid cutting tool and arbor and model the collision of antrum wall, when reducing cutting tool to machine shake or the danger of cutting tool damaged, be helpful for improving efficiency of the exterior quality of the mould, treatment and the life that prolong cutting tool thereby. (2) hard mill of cutting tool high speed is the most commonly used is small diameter (12mm is the following) establish milling cutter, basically have milling cutter of head of double blade ball, Shuang Ren milling cutter of round razor blade, end ages 6 blade stand milling cutter and of two but of dislocation round razor blade establish milling cutter. Among them integral hard alloy establishs milling cutter to have the good point with high tigidity of Xiaohe of round jumpy error. The hard coating of appropriate hard alloy cutter hub, heat-resisting and negative cutting tool point of view are hard mill the parameter of main cutting tool that achieves result. The careful grain that milling cutter basically collects appliance to have very good tenacity (0.
5 ～ 0.
8 μ M) and exceed fine grain (0.
2 ～ 0.
5 μ M) hard alloy is made. The azotic aluminium that the wearability of cutting tool fights oxidation function and inferior internal stress higher through having changes titanium (TiAlN) or TiAlCN coating will improve, only coat ply is 2 ～ 3 μ M, use PVD craft to undertake besmear Fu. Current, in advantageous geometrical border the condition falls, hard mill can machine hardness to be the workpiece of HRC65, and in be being produced actually, the hardness majority of the mould is inside 54 limits of HRC47 ～ . Use the milling cutter that exceeds fine grain hard alloy and TiAlN coating, when hard mill cutting speed can amount to 200 ～ 350m/min, every turn or every tine feed is 0.
1 ～ 0.
2mm. Treatment mould should use thick mill and mill of essence of life as far as possible two working procedure, go through mill of high speed milling major material surplus, stay 0 what be close to finished product outline.
05mm mental allowance, use lesser row spacing width to have mill of essence of life next. Uses row spacing width affects handling time, quality and exterior surface roughness greatly. (3) the because use, is slightness small diameter milling cutter when knife clip machines a mould, bits ply is cut when milling lesser, cutting speed tall, treatment process suffers the effect of vibration of round jumpy sum of errors easily. Accordingly, requirement knife clip should have the long and thin structure of circumgyrate semmetry not only, have rigid good, round jumpy error even at the same time small, clip holds muscularity and slippery torque advanced character. Look from integral performance, what can satisfy these requirements most at present is one kind uses hollow awl power (HSK) shrinkage fitting is cold shrink type knife clip. The round jumpy error that this kind of knife places is 3 μ M only (in hang those who extend length to be 3 × D to examine measure on the club) , if be the knife clip of 6mm to installing knife diameter, can deliver the torsion of 22Nm. Clip of this kind of knife is used more generally already in mould treatment, with will assemble and unassemble the induction of cutting tool heats the accessory of random form a complete set that appearance already often regarded mould high speed as to machine a machine tool. To acquire longer cutting tool life and better treatment surface quality, machine tool, the knife is placed, the round jumpy error of cutting tool system should be in 12 μ M, had better not exceed 10 μ M, this chooses more accurate than common milling cutter milling cutter with respect to need, the round jumpy error of this kind of milling cutter should be commonly in 5 μ M. Such, the round jumpy error that is like a main shaft (it is commonly: 70mm of φ of main shaft diameter is 2 μ M, φ 90mm is 2.
5 μ M) , the knife is placed (3 μ M) with milling cutter (5 μ M) round jumpy error undertakes overlay by ultimate circumstance, its total circle is jumpy achieve 10.
5 μ M. When the hard milling of lubricant or cooling high speed when high speed hard milling, very high temperature arises in the meeting on cutting edge, when if use cooling fluid to undertake cooling,lubricating, can make cutting tool generates quick temperature mutation negative charge, the organization in causing hard alloy cutter hub produces tiny flaw. Such, cutting tool is met premature invalidation. Accordingly, should not be when high speed hard milling use cooling fluid to undertake cooling lubricating, should use dry type good treatment. But the cutting temperature when considering hard mill is rise and increase of hardness and cutting speed as workpiece, be in so workpiece hardness is not very high case falls, also can consider to use minim to lubricate when high speed hard milling. When workpiece when hardness is very tall, this kind of minim lubricates to also can cause hard alloy cutting tool to generate intense thermal shock negative charge. Accordingly, hard to this kind of high speed milling should be used compress cold air to undertake blowing dividing cutting bits, in order to avoid negative charge of generation thermal shock, cutting tool life can raise 20% ～ commonly 30% . In addition, establish milling cutter to 6 blade especially, use what bits cuts when compressing air to blow bits to still can avoid to machine to twine. Use when compressing cold air to play bit, compress airy pressure to should be achieved at least 6 cling to (0.
6MPa) . For example, a hardness is the mould of HRC61, when high speed hard mill, used pressure to be 6 cling to, refrigeration comes - the compression of 30 ℃ air. According to the introduction of German Franken company, such compression cold air is helpful for blowing not only except cut bits, and be below the most favorable situation can make the durability of cutting tool rises 30% . What should allude here is, the compression that uses here cold air is through special backset is in charge of device to will compress air to come quickly velocity of sound, in accelerating a process, make its depart becomes cold, heat two parts, part derivative, be produced from this amount to - the cold air of 30 ℃ , repass aims milling cutter edge to undertake playing bit of the plastic tube of nozzle. The principle that high speed hard milling should follow can obtain better exterior quality, shorter handling time and technological process, inferior treatment fee as a result of the high speed hard milling of the mould and receive wider and wider application. When mould of high speed hard milling, it is the effect with be achieved better, should follow following principle: (1) of cutting tool dangerous extend should as far as possible short, and in shrinkage fitting cold shrink knife handle of the cutting tool in type knife clip is due and enough long clamp length. (2) should use suitable mill means, so that improve the life of cutting tool (at least 20% ) with the treatment surface quality with be obtained better. (3) establish the round jumpy error of milling cutter to answer as far as possible a few smaller. (4) should abandon wet treatment, use frigorific compression as far as possible air undertakes blowing bits and cooling cutting tool. (5) should according to the material of the mould qualitative, hardness and treatment condition choose appropriate cutting rate and feed career. (6) major material surplus should be excised as far as possible when thick mill, stay about for mill of essence of life namely 0.
The mental allowance of 05mm, discharge foreword of half energy milling machine operator to produce technological process in order to shorten. CNC Milling