High speed cutting (go up)

The main shaft of technical key high speed of high speed cutting is the first requirement of high speed cutting, to different workpiece material, current cutting rate can amount to 5 ～ 100m/s. The diameter of the rotate speed of main shaft and cutting tool is concerned, when the ball head milling cutter that uses small diameter, main shaft rotate speed can amount to 100000r/min. (1) the main shaft majority that main shaft of ball bearing high speed equips on milling machine of cutting of current high speed is ball bearing dynamoelectric main shaft. If the graph is shown 1 times, dynamoelectric main shaft is comprised with the system that measure part by component of rotor, bearing, crust, electric machinery. Besides, when main shaft runs, still must deploy cooling system, lubricant system and frequency conversion drive electric unit. The bearing of high speed main shaft is 15º with pressure angle mostly or the horn of 25º contacts ball bearing, its accuracy class with exact form (C class) and exceed exact level (B class) give priority to. To increase the limited speed of bearing, some bearing plants added series of high speed bearing on common series foundation, what what differ basically is to use the steel ball with lesser diameter and cage to direct with outer lane raceway, the to bearing outer lane pressure that reduced steel ball to be caused by the action of centrifugal force thereby and the lubricant condition when improving cage to run. The newest development of bearing of high speed main shaft is so called mixture bearing, its inside, outer lane is become by bearing steeliness, but ball changes silicon pottery and porcelain to be made by nitrogen. Compare with steel ball bearing, density of ball of pottery and porcelain decreases 60% , can reduce centrifugal force substantially consequently. Additional, the stretch model volume of pottery and porcelain is higher than steel 50% , when identical ball diameter, mixture bearing has taller stiffness. The another characteristic that nitrogen changes silicon pottery and porcelain is coefficient of friction low, the attrition when can reducing bearing to run from this is calorific, wear away reach power loss. The rotate speed that compares not coaxial main shaft to facilitate is characteristic, use rotate speed eigenvalue to come commonly magnanimity, its definition is: Rotate speed of × of ＝ axis diameter divides rotate speed eigenvalue outside bearing, lubricant means also is a when limit of influence main shaft turns main factor, express 1 it is all sorts of bearing issue the eigenvalue that can achieve in different and lubricant condition. Expressing grease of eigenvalue of rotate speed of 1 dynamoelectric main shaft to lubricate is one kind uses most means, the advantage is a structure simple, safeguard convenient, dependability is mixed high cost is low. Defect is top rotate speed inferior, want to increase rotate speed, adopt the approach that uses ball of pottery and porcelain only. Oily mist lubricates to weigh gas again / oil-lubricated, must start lubricant plant first before main shaft starts, should device general lube and compress air to mix to pass pipeline to enter oily mist in season each bearing next. This kind of lubricant means is belonged to lubricate compulsively, below regular job circumstance, can assure good lubricant condition in order to increase rotate speed. Its defect is a structure complex, main shaft housing wants have as an attached institution a lot of must sealed lubricant passageway, production cost is higher. Additional, main shaft divides drive outside electric unit, still must have lubricant state monitoring system, appear with handy and lubricant system when breakdown, can jockey in time, avoid main shaft to suffer damage. Another defect with oily lubricant mist is oily bad news more, and when higher rotate speed, lube film and ball attrition are calorific, main shaft temperature rise is bigger, restricted rotate speed bigger rise. Want to raise rotate speed to must use oil gas to lubricate to say fuel injection is lubricant again further. This kind of lubricant means is minim lube drips to enter lubricant pipeline by fixed time-interval gush, oily drop is in pipeline with compress air interblend to close formed the oil gas with very low oil content. The consistency of this kind of oil gas is big under above mentioned oily mist, ball and the oily film between the outer lane inside bearing are very so thin, the attrition loss of bearing decreases accordingly from this, reduced main shaft to give out heat thereby, increased the top rotate speed of main shaft. The cost essentially similar that oil gas lubricates with oily mist, so great majority of dynamoelectric main shaft all uses the high speed of new generation oil gas is lubricant. The athletic precision of ball bearing main shaft basically depends on the precision of chooses bearing. Athletic error besides the low frequency error that by main shaft the appearance error of each spare parts causes, still have the error of high frequency motion of scroll body. These athletic errors not only the exterior surface roughness that affects work, and life of influence cutting tool. At present the highest circumgyrate precision of the main shaft of ball bearing high speed on the market can be amounted to 0.

5 μ M, already developed more the new-style and dynamoelectric main shaft of high accuracy. (2) liquid style is quiet press main shaft of bearing high speed to pursue 2 it is a liquid static press main shaft of bearing high speed, the geometrical appearance of its bearing component undertakes optimizing designing, rotate speed eigenvalue can amount to 1 × 106, axial diameter is the main shaft of 30mm, its are highest rotate speed can amount to 30000r/min above. Static press bearing to give out heat to reduce high speed to run, axial way shoulds not be too great, compare with photograph of ball bearing main shaft consequently, its radial stiffness is inferior. But axial stiffness can be far exceed ball bearing main shaft, because ball bearing suffers centrifugal force to restrict, its pressure angle is general and lesser for 15º or 25º , reason axial stiffness is lesser. Bigger to axial cutting force treatment circumstance, when if use ball head milling cutter,machining tool or mould, appropriate uses a liquid static press bearing main shaft. Additional, the liquid is static the oily film that presses bearing has very big damp, dynamic stiffness is very tall, special agree with the interrupted cutting process that resembles milling. The liquid is static the biggest characteristic that presses bearing main shaft is athletic precision very tall, circumgyrate error is in commonly 0.

2 μ M is the following. Consequently not only the service life that can improve cutting tool, and can achieve very tall treatment precision and low exterior surface roughness. When production mould, use a liquid static when pressing bearing main shaft to undertake milling can the working procedure of the grinding with final leave out and manual nap, improve manufacturing efficiency thereby, reduce product cost. Because the liquid is static,press the liquid attrition loss of bearing, loss of reason drive power is than ball bearing big. Why to because this is chosen,plant bearing, need fibrous root asks to decide according to specific applying. If material excision amount is large, very not tall to machining exterior surface roughness to ask when, want first consideration to use ball bearing main shaft. If the allow of treatment precision is poor small and exterior surface roughness asks very hour, should use a liquid static press bearing main shaft. (3) air is static press main shaft of bearing high speed the rotate speed that it can increase main shaft further and circumgyrate precision. Graph the 3 air that are a for high speed cutting development are static press main shaft of bearing high speed, its rotate speed eigenvalue can be amounted to 2.

7 × 106r/min, circumgyrate error is under 50nm, top rotate speed can amount to 100000r/min. Use diamond cutting tool to be able to undertake lens face milling, machine ranges of all sorts of sophisticated high accuracy form. Gas is static the good point that approachs bearing main shaft depends on tall circumgyrate precision, high rotate speed and small temperature rise, basically agree with consequently the situation that workpiece appearance precision and exterior surface roughness have high demand. Its defect is carrying capacity inferior, do not agree with the applied circumstance with material excision larger amount. In addition it asks high-definition clean is spent compress air, reason use charge and uphold charge taller. Appear to prevent main shaft overload to main shaft gets stuck dead and cause serious damage, reason should make careful analysis to its use condition. (4) it can achieve main shaft of high speed of magnetism float bearing higher main shaft rotate speed, if pursue,4 are shown. The rotor of magnetism float main shaft is mixed by two radial bearing of two axial bearing, rotor and bearing clearance are in commonly 0.

1mm left and right sides, because the attrition quantity of heat of air space is very small, the rotate speed eigenvalue of main shaft of reason magnetism float can amount to 4 × 106r/min, for double of ball bearing main shaft, if the top rotate speed of main shaft is identical, criterion magnetism float main shaft can adopt older axial way, have taller tigidity (be ball bearing main shaft about 10 times) with larger carrying capacity. The circumgyrate precision of magnetism float bearing, basically depend on the precision of the displacement sensor that uses inside main shaft and sensitivity and the precision function that control circuit. The circumgyrate precision of the magnetism float main shaft that uses at present can be amounted to 0.

2 μ M. The advantage of magnetism float main shaft is high accuracy, high rotate speed and tall stiffness. Defect is not only rigid structure is complex, and the sensor system that needs one a complete set of and control circuit, so the cost of magnetism float main shaft is the double above of ball bearing main shaft commonly. Another its defect is temperature problem, inside main shaft component besides drive electric machinery, still have the coil of axial and journal bearing, every coil is additional heat source. Accordingly, magnetism float main shaft must have very good cooling system, otherwise the temperature rise of main shaft will be very big. The treatment precision of Peng Xiang workpiece. (5) high speed of drive electric machinery changes inchoate dynamoelectric main shaft to be given priority to with drive of asynchronous electric machinery, its rotor and stator undertake assembly with the manufacturer of means supply main shaft of loose mail. Main shaft is the largest output power basically depends on the oldest concessional rate of electromotor rotor, this one speed accepts the intensity restriction of rotor material. The concessional speed of the rotor of common electric machinery is under 120m/s, concessional speed can amount to the rotor of special electric machinery 150m/s or taller, graph 5 it is the power of the biggest output that can amount to below all sorts of rotate speed circumstances. S1 is the power of main shaft output when concessional speed is 150m/s, s2 is corresponding and concessional the power of the biggest output when speed is 120m/s. Each are bit more scattered in the graph the data that represents manufacturer of different main shaft to be offerred in its catalogue item. This shows, the main shaft power that heretofore uses actually is mostly under the curve of 120m/s. Want to enhance the power of the biggest output of main shaft, must increase the strength of the rigid structure of rotor. The quantity of heat that another element of function of main shaft of influence of drive electric machinery is generation of electric machinery itself causes main shaft temperature rise, bring about drive shaft axial stretchy with the center tall happening change, it is treatment precision if really ever since constant in the process that main shaft runs wave motion, highlight particularly when using drive of asynchronous electric machinery. Outside giving out heat except the winding of stator because of asynchronous electric machinery, rotor also produces quantity of heat as a result of the action of short circuit annulus. The quantity of heat inside stator can be passed additional cooling system undertakes eliminating, but the quantity of heat inside rotor can pass the clearance between stator and rotor to be delivered outwards only, make rotor temperature easy elevatory cause stretchy. Settling the way with calorific rotor of asynchronous electric machinery is to use synchronous electric machinery. The rotor of synchronous electric machinery is You Yongjiu magnet is made, electric current is not formed inside the rotor when movement, oneself won't be so calorific. The quantity of heat that stator winding produces can be passed in that way like asynchronous electric machinery additional cooling system gives eliminate. Graph 6 be electromotor of pace of similarly hereinafter of condition of power of different main shaft and asynchronous electromotor quite. This shows, asynchronous electromotor main shaft applies to the circumstance with inferior rotate speed only. Become when rotate speed is higher, must use synchronous motor, the temperature rise that controls main shaft harder otherwise and axial are stretchy. 2. Main shaft of high speed of structure of machine tool of high speed cutting must pack the machine tool that can get used to high speed cutting in the structure, ability produces the numerous advantage of high speed cutting adequately. This has very high feed rate with respect to machine tool of cutting of requirement high speed, be in there still is tall fixed position precision below high speed very much. In addition, high speed feed should rely on very big acceleration to come true, so machine tool of high speed cutting should have very tall static stiffness not only, still must have very tall move stiffness. According to afore-mentioned a few requirement, machine tool of high speed cutting basically develops from two direction in 90 time: It is to the key on the foundation of general accuracy machine tool component undertakes improvement. 2 it is the new-style structure machine tool that development is different from general accuracy machine tool completely. (1) the slip drive system that high speed of feed drive system changes machine tool of high speed cutting is in what use drive of guide screw of big lead ball and the rotate speed that increase servo feed electric machinery to come true more at the beginning of 90 time, general feed speed can amount to 60m/min left and right sides. To can achieve higher feed rate, appeared in last few years system of drive of linear electric machinery. Because its very close to each other is unoccupied place, inertial small, stiffness is bigger and without wear away, through control circuit can realize high rate and high accuracy drive, 1997 feed speed already amounted to 120m/min. The basic construction of linear electromotor and common rotate electric machinery is similar, if the graph is shown 7 times, but the hypothesis rotates to electromotor edge generatrix is cut open and level make a linear motor. It need not other long move device to be able to produce sharp movement. Because electromotor and slip just were connected together, the stiffness of whole drive is taller, can achieve very wide adjustment thereby frequency band. The acceleration of drive system depends on the quality of the power of drive electromotor and slip. Compare with photograph of system of guide screw drive, the add quality on slip can affect the dynamic character of system of linear electromotor drive apparently. Nevertheless, because linear electromotor has wider adjustment frequency band can achieve taller than guide screw drive orbit precision. With rotate electromotor photograph is compared, the electric current of linear electromotor is calorific the loss is very big, when the power when electromotor is greater, must provide corresponding cooling system. (2) athletic component argue is changed and nicety of servo feed control changes a plan the 8 machining center that are cut of a high speed, the quality of the mobile component of axis of its X, Y, Z3 all more traditional structure is light, and all introduce drive of linear electric machinery, force of the biggest feed is 15000N, 10000N and 7500N respectively. Speed of each axis feed can amount to 100m/min, acceleration is in 9.

5 ～ 19m/s2. Use get together brilliant diamond (PKD) when milling cutter machines aluminium alloy, can use following cutting dosage: 100mm of bit body diameter, tooth is counted 12, cutting speed 5030m/min, enter knot speed 15m/min, 16000r/min of main shaft rotate speed, cut 50mm of ＝ of wide α E, 1mm of ＝ of P of cutting deepness α . The tracking error that moves to reduce high speed and obtain the smooth decelerate that add ／ , control of the look up before numerical control system applied contemporary control to be able to come true theoretically, before the flowing change of buy feedback and speed. Graph 9 it is milling machine of the large high speed that American Ingersoll company is company of British British Aerospace to offer face. Area of lathe bed bottom is 33m × 15m, have third floor about tall, it basically uses treatment spare parts of aircraft of large aluminium alloy. This machine tool contains 4 liquids are static press main shaft head to be able to undertake cutting at the same time, 245mm of main shaft diameter, length 240mm, main shaft electromotor is 150kW in the output power inside limits of 10000 ～ 20000r/min. When 4 main shaft work at the same time, the excision rate of workpiece material can amount to 26000cm3/min. CNC Milling