Hard turning actually not difficult

The surface of 0028mm is bright and clean degree, 0.

The circularity of 0002mm and ± 0.

The diametical public errand of 005mm, such precision is undertaking to the workpiece before temper by dipping in water is hard " soft turning " can achieve likewise on identical machine tool, thereby utmost land increased utilization rate of equipment and installations. But because some factories chose bit erroneously (saying exactly is cheaper razor blade) , or the pressure that is not clear that whether place has enough tigidity to be cut in order to bear at average car doubly with the machine tool, make thereby hard turning craft gives his without sufficient play tall effect. With a ha hold out a company (Hardinge) the specific application case that uses engineer Tom Sheehy to be in this company according to hard turning, think the beard when hard turning is paid attention to the following 8 respects. 1. Workpiece although the initial drop that 45HRC hardness is hard turning, but hard turning often undertakes on the workpiece of 60HRC above hardness. Hard turning material includes tool steel, bearing steel, cementite steel and chromic ferronickel alloy normally, be able to bear or endure corrode heat-resisting nickel base the special material such as cobaltic alloy of chromium of alloy, tungsten. According to metallurgy, cutting deviation of the hardness inside deep limits small (be less than 2 HRC) material can show best process to be able to forecast a gender. Most agree with the spare parts of hard turning has lesser long way to compare (L/D) , say commonly, of the L/D that does not have the workpiece that prop up than not be more than 4:1, of the L/D that has the work that prop up than not be more than 8:1. Although long and thin spare parts has rear push frame to prop up, but because cutting pressure passes,still cause Dao Zhen likely greatly. The system that adds hard turning for utmost ground is rigid, should reduce as far as possible dangerous extend. 1 what cutting tool extends length to must not be more than arbor height.

5 times. 2. Stiffness of machine tool machine tool decided the treatment precision of hard turning. The machine tool that nearly 15 ～ make inside 20 years has very good tigidity almost, enough bears hard turning. Below a lot of circumstances, it is more important that the overall condition of the machine tool compares use fixed number of year greatly, the common lathe that safeguards meticulously also can be used at hard turning.  increases tigidity and damp character to give hard turning the machine tool, ha Ting uses the character of a lot of advanced machine tools at turning center, include polymer composite material to strengthen baseplate, area among them pinchcock head (make main shaft is propped up approach work) direct formula main shaft and static press slideway.  system tigidity is the biggest change mean reduce impending, cutting tool as far as possible outspread extend with the spare parts, cancel shift unoccupied place piece with washerbed down the livestock, its target is to maintain all component to be close to as far as possible turn tower tool carrier.  3. Although bit is cubic nitrogen changes boron (CBN) the price of bit is high, but CBN razor blade most agree with hard turning. CBN razor blade can hold fixed position in interrupted cutting process changeless, safe cutting tool wear rate is offerred in successive cutting process. When using sound hard turning technology, CBN razor blade besides it is beyond grinding of be not a patch on of respect of control diameter public errand, other function is the first of all. Pottery and porcelain is inferior to CBN wear-resisting, because this is general,need not be less than ± at tolerancepublic errand 0.

The treatment of 025mm. Pottery and porcelain does not agree with interrupted cutting, and cannot add cooling fluid, because thermal shock may cause bit rupture. The appearance of geometry of blunt predestined relationship of bit is the inherent characteristic of material of pottery and porcelain, this one characteristic makes cutting force increases and workpiece surface is bright and clean degree drop. Additional, point of blade of pottery and porcelain ruptures may be disastrous, it may bring about all cutting blade to all cannot be used.  cermet (cubic carbonization titanium) sclerotic to successive cutting cementite material is very effective, although it does not have CBN in that way wearability, but bit can become scale ground to wear away below most circumstance and do not rupture.  before horny razor blade because its cutting force is lesser, use in tigidity normally hard turning undertakes on not tall machine tool. About the most rational application of bit, proposal and tool supplier clasp, be in especially first phase, with achieving optimal cutting rate quickly.  4. Cooling fluid its are the biggest the problem is use or need not cooling fluid. To the interrupted cutting spare parts of gear and so on, had better use " dry turning " , otherwise feed and the thermal shock when retreating a knife cause bit rupture probably. As to successive cutting, the pliable but strong of high temperature enough that knife head produces in dry turning process is changed (bate) beforehand cutting area, reduce what material hardness makes to be cut easily thereby. Rate increasing when this phenomenon showed dry cutting is beneficial. In the meantime, have clear cost advantage without means of cooling fluid cutting.  is in successive cutting, cooling fluid may conduce to lengthen cutting tool life and improve the appearance bright and clean degree. The key of the problem is to want refrigerative fluid to be able to reach knife head, high-pressured cooling fluid is the best method that solves this problem, because it is not easy,evaporate below high temperature. In addition, high pressure can reduce the accumulation that cut bits, because cut bits block to flow to the influence of knife head to cooling fluid,decrease thereby. Another method is the coping that releases cooling fluid bit at the same time and bottom, in order to ensure cooling fluid reachs knife head continuously. If  uses cooling fluid, must be water radical. Bits is cut to be able to take away 80% ～ in what form in the hard turning course that matchs completely the quantity of heat of 90% (highest temperature can amount to cutting area 1700 ° F) . So blazing once contact oil of refrigeration of low burning point,cut bits, whole process will be destroyed thoroughly likely by. If be in,open wide type machine tool aspirant travel hard turning, must increase proper protector, avoid to operate personnel to be cut bits scald.  5. The quantity of heat that craft produces because of hard turning is major by cut bits to take away, treatment around undertakes checking can discovering whether whole process is harmonious to cutting bits. When successive cutting, cut bits to should show blazing orange yellow, be like the ground like a lace elegant and piece. If cut bits,press with the hand after refrigeration rupture basically, making clear the quantity of heat that cuts bits to take away is normal.  6. Change a layer in vain " Bai Hua layer (hot influence area) " in appearing may rebarbatively in hard turning and grinding operation, what form a naked eye to lose sight of in material surface namely is very thin (normally 1 μ M) incrustation. Bai Hua layer is formed in hard turning process, because bit passivation brings about overmuch quantity of heat to deliver a part,be commonly inside. Change a layer to often be formed on bearing steel in vain, and to bearing circle and so on needs to bear the spare parts of tall contact pressure is very harmful, as the elapse of time, the white likelihood that change a layer comes off and bring about bearing invalidation. To just beginning the plant that is engaged in hard turning, the head that the proposal is producing a few undertake selectiving examination randomly inside week, in order to decide every razor blade can turning how many spare parts and do not form Bai Hua layer. Additional, although a razor blade can machine 400 spare partses, become likely also blunt after machining 300 and begin to make the spare parts produces Bai Hua layer.  7. Bore hole the cutting pressure with very great need of boring oil hard data, because this often needs twice,increase boring lever susceptive torsional and tangential force. Use before horn (35 ° or 55 ° ) , razor blade of radius of small point of a knife can reduce cutting pressure. Raising cutting rate while reduce cut mix greatly feed speed, also be the way that reduces cutting pressure. When  bores hole, cutting tool must as homocentric as the spare parts or center of spare parts of summary prep above, the bending that causes because of cutting is out of shape make the position of real center line is reduced. Best clamp form is entire length runs from opposite directions sleeve, when boring oil hard data, entire length runs from opposite directions sleeve collet can offer highest knife to place stiffness. It is pinchcock head and collet of only place screw next.  8. Car whorl uses proper bit geometry figure is the key in whorl of the car on oil hard data, best whorl razor blade is the triangular razor blade that is similar to the installation on boring lever. When whorl of the car on oil hard data, to control cutting pressure is mixed prolong bit life, be necessary to increase knife number and be reduced cut deep. Another kind of choice is to use alternant type flank to cut way, changeable cutting force stands the position prolongs cutting tool life. CNC Milling CNC Machining