The dry cutting technology of new century

  • Time:
  • Click:169
  • source:EAMOM CNC Machining
Summary: Dry cutting makes a technology as a kind of new-style green, can prevent the cutting fluid pollution to the environment not only, and the manufacturing cost that can reduce a product substantially. The article discussed the domestic and international current situation that dry cutting studies, discussing cutting fluid on the foundation of original function, the cutting tool technology of dry to coming true cutting, machine tool technology and engineering technology had systematic analysis and research, introduced technology of accurate dry cutting and its application, looked into dry cutting technology the development henceforth. The 1 preface swift and violent development as high speed processing technique, the cutting fluid dosage that in machining a process, uses is bigger and bigger, its discharge is as high as 80 ～ sometimes 100L/min. But the use of many cutting fluid caused very outstanding negative effect: (The manufacturing cost of 1) spare parts rises substantially, in the totle drilling cost that machines in the spare parts, cutting fluid charge occupies 16% about, and 4% what the charge of cutting tool holds totle drilling cost only. (2) creates the serious pollution of didymous environment, be like a cutting fluid without processing to emit into sea of river river lake, can pollute land, fountainhead and air, floral of serious shadow sound of sth astir grows, destroy zoology environment. (What 3) harms workshop worker directly is healthy, the uses extensively water in be being produced at present base cutting fluid contains harmful to human body chemical part. In cutting (grinding) in the process, cutting fluid be heated volatilizes form mist, often diffusing in the workshop unpleasant peculiar smell, can cause a lot of disease of jockey person lung and respiratory tract, hand and cutting fluid are contacted directly, still can cause a variety of skin disease, affect worker health directly. Afore-mentioned negative effects, already became the one big obstacle that machinist industry grows. This makes people can raise a such questions: In machining can need not or use cutting liquid less? Dry cutting (Dry Cutting) technology is namely below such historical setting emerge as the times require, and from what rapid development rises since 90 time metaphase. Do Europe of cutting technology traceable, be in at present Western Europe each country also most be current. The German company that according to statistic already 8% is control now used dry cutting technology. To 2003, german manufacturing industry will have 20% above to use dry cutting technology. Study in dry cutting and use a field, at present Germany is in international lead position. Japan already developed the machining center doing type that does not use cutting liquid successfully. Of the dry cutting system with cooling liquid nitrogen, extract tall purity nitrogen from inside air, below normal temperature with 5 ～ the pressure of 6 atmosphere sends liquid nitrogen toward cutting area, can realize dry cutting smoothly. Material of strong to exceeding cutting tool and technology of cutting tool coating had had the unit such as university of industry of institute of tool of our country Chengdu, Shandong and Tsinghua university systematic research, cutting tool of pottery and porcelain already formed certain productivity at present in our country, these research that are dry cutting technology and application laid abecedarian technology foundation. Institute of Beijing machine tool develops the KT series machining center that can realize high speed successfully to do cutting recently. Simple disuse cutting fluid can not realize the function of 2 cutting fluid and the dry cutting of main difficult point that realize dry cutting. Must analyse it is after fluid of cutting of out of service, can you appear what problem? What measure should adopt to remove these adverse effects? For this, answer cutting fluid to there is a comprehensive, thorough knowledge in the action in machining and function above all. In machining, cutting fluid basically has 3 big functions: Lubricant function -- after entering cutting area when cutting fluid, it is mixed to cutting tool, workpiece with respect to meeting infiltration cut the interface between bits, form a lubricating film. This lubricating film can reduce the attrition of cutting process, reduce cutting force, reduce the felt phenomenon that cuts bits and cutting tool to restrain the generation of the tumour that accumulate bits, be helpful for improving quality of treatment surface technology. Cooling function -- the energy that cutting process place wastes 90% above translate into heat in metal cutting. Cutting fluid the treatment area from the machine tool takes away an effectively heat in metal cutting quickly, reduce the temperature rise of area of machine tool cutting greatly thereby, raise the treatment precision of the durability of cutting tool and workpiece. Assistance is discharged bits and break bits -- the strong lotion that cutting fluid regards high pressure as large flow, can cut bits pettily to rush from workpiece or cutting tool, will cut bits rapid from the eduction in the machine tool, at improving the treatment of the spare parts with benefit precision is mixed the service life of cutting tool. Banding the geometrical structure that cuts bits to basically rely on cutting tool will achieve bit, but the auxiliary function with high-pressured cutting particular to breaking bits and platoon bits to also rise fluid. When undertaking doing cutting, in the absense of afore-mentioned lubricant, refrigeration of cutting fluid and auxiliary platoon bits and stop the action such as bits, consequently heat in metal cutting can increase quickly, the machine tool machines area temperature to rise apparently, cutting tool durability is reduced greatly. Want desiccate cutting to be able to go on wheels, achieve or exceed the treatment quality when wet treatment, productivity and cutting tool durability, must mix from cutting tool, machine tool each respect takes work a series of measure. Because this dry cutting technology is a huge systematic project, among them the biggest difficult point is doing the performance in cutting at how raising cutting tool, also wait to material of machine tool structure, workpiece and process at the same time raised new requirement. The cutting tool of cutting tool technology of 3 dry cutting whether bear the tremendous heat energy when dry cutting, it is the key that realizes dry cutting. Main measure has: Graph the relation of hardness of 1 different material and temperature uses new-style cutting tool material to do cutting to ask cutting tool material has very tall red rigid and hot tenacity not only, and still must have good wearability, heat-resisting is pounded and fight caking property. Graph 1 listed the relation of the hardness of material of a few kinds of cutting tool and temperature. See by the graph, cutting tool of pottery and porcelain (Al2O3, si3N4) , cermet (the hardness of the material such as Cermet) also is reduced rarely below high temperature, have very good red rigid namely, accordingly very agree with the dry cutting of common goal. But like this kind of material more fragile, hot tenacity is bad, do not apply to undertake interrupted cutting. Stand to change boron for nitrogen (CBN) , get together brilliant diamond (PCD) , exceed fine grain hard alloy to wait exceed material of strong cutting tool to be used extensively at doing cutting. Use coating technology to undertake to cutting tool coating is handled, it is the important way that improves cutting tool performance. Coating cutting tool divides kinds big: One kind is " hard " coating cutting tool, wait for Xu layer cutting tool like TiN, TiC and Al2O3. Hardness of surface of this kind of cutting tool is tall, wearability is good. Another kind is " soft " coating cutting tool, be like: The coating cutting tool such as MoS2, WS, cutting tool of this kind of coating also is called " self-lubricating cutting tool " , the coefficient of friction of it and workpiece material is very low, have 0 only.

01 the left and right sides, can reduce cutting force and drop cutting temperature. Cutting experiment makes clear, can machine only without coating tap add 20 screw; 1000 screw can be machined when using TiAlN coating tap, and the tap of MoS2 coating can machine 4000 screw. After high-speed steel and coating of PVD of hard alloy course are handled, can use at doing cutting. Apply to the CBN cutting tool that has cast-iron dry cutting only so, also can use treatment after be handled through coating steel, aluminium alloy and other super- close forcedly. .

Actually, coating has the function that is similar to cooling fluid. It produces one thermal insulation, make heat up won't or pass into cutting tool rarely, can be in thereby longer when why inside the interest of hard He Feng that holds point of a knife. Coating still has the effect that does cutting middleman and guarantor to wait for cutting tool material not to get chemical response in high speed. In developing process of dry cutting technology, want special attention the effective application of coating cutting tool. Optimize cutting tool parameter and cutting dosage the geometrical parameter of cutting tool and structural design must satisfy dry cutting to be opposite bits and the requirement that discharge bits. There is very crucial effect to breaking bits in breaking bits chamfer to be machined in tenacity material. In lathe tool at present three-dimensional curved surface breaks the design of bits chamfer respect to make a technology had compared maturity, can be aimed at different workpiece material and cutting dosage, very fast design gives structure of corresponding the chamfer that break bits and measure, can rise greatly cut bits to break off ability and to cutting the control capacity of bits flow direction. High speed treatment has cutting power small, medicinal powder hot definitely, treatment process stability is good wait for an advantage, technology of high speed cutting and the organic union that do cutting technology, will achieve manufacturing efficiency quality of tall, treatment is good and wait for multiple interest without environmental pollution. The special problem that the consideration wants when the machine tool technology of 4 dry cutting designs dry cutting machine tool basically has two: One is heat in metal cutting send out; Another is the eduction that cuts bits and dirt. The quantity of heat that area generation machines in the machine tool when dry cutting is bigger, if go not in time from the eduction of main body structure of the machine tool, can make the machine tool produces heat to be out of shape, influence workpiece machines precision and dependability of machine tool job. To a few cannot the quantity of heat of eduction, relevant component should take adiabatic step. Discharge bits to facilitate. Dry cutting machine tool should use vertical main shaft and bend inclined lathe bed as far as possible. On workbench tilt cover board can be made with heat insulating materials. Send helix platoon bits chamfer a large number of eager bits directly. The in order to of system of circular air conditioning that uses inspiratory system to be able to prevent the place inside the accumulation of eager bits on workbench and other bearing component increases the thermal stability of machine tool machining complex. In the certain key that machines an area place installs temperature sensor, the metabolic circumstance of field of temperature of machine tool of monitoring of in order to, undertake through numerical control system mathematical error is compensated when necessary. Filter to the dust grain filter that the system can produce in process of will dry cutting is dropped and be sucked in time by convulsions system. The treatment division that produces dust should be mixed the main shaft component of the machine tool and hydraulic pressure, electrical system is tight add segregation. Still can pass these pair of components to bring to bear on in addition small pressure, with preventing dirt invade. Wait to aluminium alloy or fiber increase plastic when undertaking doing cutting, must use high speed machining center or machine tool of numerical control of other high speed, rotate speed of its main shaft is as high as 25000 ～ 60000r/min commonly, advocate electromotor power 25 ～ 60kW, use normally " electric main shaft " transmission structure means; Feed speed is as high as 60 ～ 100m/min, acceleration 2 ～ 8g(g=9.

81m/s2) . For the 10 times above of machine tool of ordinary numerical control, already replaced ball guide screw to achieve exercise of high speed feed with linear servo electromotor stage by stage now. The material of engineering technology workpiece of 5 dry cutting decided to carry out the possibility of dry cutting greatly. Of dry cutting " workpiece material / treatment method " combination expresses place to show as follows. See by the watch, exceed hard alloy and steel to be hard to undertake doing cutting most. Bore with a reamer of milling of turning of method of treatment of the workpiece stuff that is hard to have doing cutting and material of workpiece of watch of treatment method combination cuts tap bore × of aluminium alloy × of × of × of cast-iron steel × exceeds × of × of × of × of hard alloy × composite material notes: × expresses to be hard to undertake aluminium alloy conducts heat doing cutting coefficient is tall, the meeting in adding a process absorbs many heat in metal cutting; Hot Peng goes up coefficient is big, make workpiece happening heat is out of shape; Hardness and melting point are inferior, bits is cut to happen very easily with cutting tool in machining a process " glue solder " or adhesion, this is the biggest difficult problem that when aluminium alloy does cutting, encounters. The best method that solves this difficult problem is to use high speed to do cutting. In high speed cutting, the heat in metal cutting of 98% passed 95% ～ to cut bits, cut bits to be met on the interface with surface contact of the knife before cutting tool by local and fused. Form a paper-thin liquid state film, cut bits to be cut very easily to leave work in the instant consequently, reduced cutting force and the possibility that produce the tumor that accumulate bits greatly. Workpiece can hold normal temperature position, raise a factory to manufacture efficiency already, improved the treatment precision of aluminium alloy workpiece and exterior quality again. To reduce high temperature next cutting tool are mixed between workpiece of material diffuse and felt, should special attention the reasonable collocation between cutting tool material and workpiece. For example, diamond (carbolic element C) and iron element have very strong chemical affinity, although reason diamond cutting tool is very hard, but unfavorable process steely work at be being used; Titanium has titanium element in alloy and alloy of certain high temperature, because this also cannot undertake dry cutting with the coating cutting tool that contains titanium. Can be opposite like PCBN cutting tool again hard steel of temper by dipping in water, cold hard cast-iron undertake doing cutting with the horniness workpiece data that passes exterior thermal spraying, and when the work that processing medium, low hardness, life of its cutting tool is returned not as good as the life of common hard alloy is tall. Graph 2 laser assist dry cutting to pursue 3 with liquid nitrogen cutting tool of 4 PCBN of graph of cooling cutting tool is in the cutting tool after turning RBSN material wears away good car is a kind " with the car era is ground " new technology, with Yu Mou some unsuited the turn that has grinding rests the treatment of the spare parts, it is a kind of efficient dry cutting technology. Changing silicon to nitrogen (when Si3N4) workpiece has good car. Because this material has extremely high tensile strength, make any cutting tool very fast damaged. Can use laser to assist cutting, with stimulate beam of light to undertake warm-up to workpiece cutting area (2) seeing a picture, make workpiece material local bate (its tensile strength falls by 750MPa to 400MPa) , can reduce cutting resistance 30% ～ 70% , cutting tool wears away can reduce 80% the left and right sides, the vibration in dry cutting process also is reduced greatly. Raised material excision rate greatly. Desiccate cutting is able to go on wheels. Alloy of titanium aluminous vanadium (Ti6Al4V) and reaction agglomeration nitrogen change silicon (the difficult treatment material that RBSN) is a model, its conduct heat coefficient is very small, much heat produces in dry treatment, make cutting tool material produces chemistry to decompose, cutting tool very wear away definitely, the graph shows the new method that to use liquid nitrogen cooling cutting tool processes this kind of data 3 times. Held a thing of metallic cap shape on face of the knife before lathe tool, of its lumen and razor blade on the surface constitutes an airtight chamber jointly. The cap has the entrance of liquid nitrogen and export on account other people. In dry cutting process, liquid nitrogen flows in airtight room ceaselessly, absorb the heat in metal cutting on bit, make cutting tool does not produce exorbitant temperature rise. Maintain good cutting performance from beginning to end, successful implementation does cutting. Graph the 4 experimental results that are wear extent of the cutting tool when processing RBSN workpiece data with PCBN cutting tool. Length of turning of cutting tool of the PCBN when using cutting tool of liquid nitrogen refrigeration only 40mm, knife face wear extent is as high as 3mm after, cutting can no more undertake going down. After using afore-mentioned liquid nitrogen device, cutting tool wear out condition is improved greatly, after turning length 160mm, knife face wears away only after 0.

4mm. Be added the circularity error of workpiece also is decreased from 20 μ M to 3.

2 μ M. Liquid nitrogen is a kind of raw material that obtains very easily low-cost still can use repeatedly. The dry cutting with 6 accurate dry dinkum cutting undertakes very hard sometimes, can use minimum right now lubricant technology (Minimal Quantity Lubrication) , abbreviation MQL. This kind of method is to will be compressed after air mixes aerification with a few lubricating fluid, eject arrives treatment area, to the treatment between cutting tool and workpiece place undertakes lubricating. MQL technology can decrease greatly " cutting tool, workpiece " and " cutting tool, cut bits " the attrition between, rise to restrain temperature rise, reduce cutting tool to wear away, prevent adhesion and the function that improve workpiece to machine quality. The lubricating fluid that it uses is very few. And the effect is very distinct however, improved work efficiency already, won't cause pollution to the environment again. Use for example (Ti, when cutting tool of Al)N+MoS2 Xu layer undertakes dinkum dry cutting to aluminium alloy workpiece. After cutting tool drills 16 hole, in cutting bits to allow bits chamfer in broach with respect to felt, make cutting tool cannot be used completely. After using MQL technology. Bore number is as high as 320. Broach also has not happened to wear away apparently or adhesion, add all Kong Dou that come out to satisfy a requirement. The lubricating fluid dosage that MQL law place uses is commonly 0.

03 ～ 0.

2L/h, be wet cutting about 60 thousand 1/0. Cleanness is compressed with the clean course that cut bits still can reclaim use, do not pollute an environment completely. Because this MQL law is called again " accurate dry cutting " (Near-Dry Cutting) . Technology of accurate dry cutting and photograph of coating cutting tool are united in wedlock, can obtain best result. For example, process X90CrMoV18 alloy steel with broach of high-speed steel coating. When undertaking working purely getting cutting with broach of TiAlN coating high-speed steel, get 3.

After the be favored with of 5m cuts length, get break be damaged; Use (broach of TiAlN+MoS2) compound coating and the smallest lubricant way, its are gotten cut length to increase 115m. 7 summary and looking into dry cutting technology is a when produce kind to the tradition major innovation, it is kind of brand-new clean production technology. The environmental protection code with world increasingly strict each country, be helpful for doing the promotion of cutting technology and application quickly; All sorts of exceeding hard, high temperature resistant the development of cutting tool material and its coating technology, created very advantageous condition to do cutting technology; The effective application of lubricant device and the aperture of all sorts of center alveolus machine minimum of standard cutting tool appear, more and more application were won in making allow to do cutting to be versed in in aluminium alloy and the Kong Jia of all sorts of difficult treatment material. Dry cutting technology from appear to now to have only weak point history of 10 years, it is a kind of burgeoning green makes a technology. Have important sense to carrying out the mankind to be able to develop the strategy continuously, the forward position that is new century makes a technology. CNC Milling CNC Machining