Technology of high speed cutting processes medium application in structure of aviation thin wall
- source:SHNMIN CNC Machining
Processing technique of cutting of high speed of structure of aviation thin wall (1) the processing technique of definition high speed of processing technique of high speed cutting is to point to use exceed hard data cutting tool, excise precision of rate, treatment and the contemporary processing technique that process quality through raising cutting speed and feed speed to improve data greatly. As a result of different treatment working procedure, different workpiece material has different cutting speed limits, give a certain numerical value very hard with respect to the speed limits of high speed cutting consequently. To different material, think the speed of high speed cutting of casting pig is 800 ～ 3000m/min, steel commonly it is 100 ～ 1000m/min, aluminium alloy to be 1000 ～ 7000m/min for alloy of 500 ～ 2000m/min, titanium. High speed cutting, it is high rate above all, namely high main shaft rotate speed. On the other hand, due high feed rate, to improve efficiency, the machine tool is had even sudden shift, fast change knife, tall main shaft acceleration and feed acceleration, achieved what afore-mentioned standard ability say to be high speed only. Normally the circumstance falls, inside the industry S>7000rpm of main shaft rotate speed, the milling treatment of above of 10000mm/min of cutting feed speed calls treatment of high speed cutting. (2) the definition of structure of aviation thin wall is in plane construction part, the state that according to its aboard bears the weight of and structural feature are cent of plane framework spare parts casing kind, bridge kind, contact kind, wainscot kind, costal region kind wait for a type. (3) the cutting of advantage high speed that high speed cutting machines Bao Bi structure machines Bao Bi have distinct advantage at conventional treatment relatively: Cutting force is small, machine Bao Bi kind the workpiece when the spare parts arises let a knife be out of shape reduce accordingly, the dimension precision that assures a spare parts easily and form precision. Heat in metal cutting decreases to the influence of the spare parts, heat of spare parts treatment is out of shape small, this thin to control wall heat is out of shape very advantageous. Treatment precision is tall, the incentive frequency of cutting tool cutting is far from the natural frequency of machining complex of thin wall structure, assured better treatment position, realized smooth cutting, card the precision of the spare parts and exterior surface roughness. Treatment efficiency is tall, taller than groovy treatment 5 ～ 10 times, rate of excision of unit time stuff can rise 3 ～ 6 times. Structure of thin wall of treatment of high speed cutting is right the respect such as process designing of program of dosage of cutting cutting tool, cutting, technology, numerical control raised new requirement. 2.
Cutting tool and its clip run a system 2.
The choice principle of structure of 1 cutting tool to cutting tool of razor blade of machine clip type, because bit helix angle is very small, cannot form big helix angle, want to machine the thin wall structural member of high quality truly so, do not use cutting tool of machine clip type to be used at high speed cutting. Mix to milling cutter of hard alloy of whole form of characters or letters solder type hard alloy milling cutter, besides solder hard alloy should assure type outside soldering firm sex, cutting tool makes should accord with following requirement: (1) have the point of view of cutting tool geometry that match: Bigger before the helix angle of the horn after horn is mixed and moderate; (2) reasonable short blade grows lever structure; (3) side tine, bottom tine is completely symmetrical; (4) use columnar power, without cut smooth structure; (5) place of cutter hub step uses round part excessive; (6) taller exterior surface roughness; (7) the appearance of cutting blade geometry of the design must cut bits to create character below condition of cutting of consideration high speed; (8) to raise stiffness, increase the size of cutting tool center as far as possible; (9) the sex that discharge bits is good. Nextpage2.
Choice of material of 2 cutting tool and material of cutting tool of cutting of high speed of cutting speed requirement must it is wear-resisting, good to fight concussion ability (include thermal shock and force impact) , hardness is as tall, small as workpiece material affinity; The cutting tool material of high speed cutting needs fibrous root occupies workpiece material and treatment property to choose; Usually, high speed cutting does not use high-speed steel cutting tool, use hard alloy cutting tool more; As a result of circular arc of the point of a knife after short time cutting radius and before knife surface contact the coating of the area appears fall off, coating hard alloy is actual the effect and without likeness of coating hard alloy, reason is not recommended use coating cutting tool. Because cutting tool produces huge to leave mental efforts when high speed cutting, those who splatter cut bits and collapse blade and the system of cutting tool clamp that become loose to have very high kinetic energy, axial trends force still exists in machining a process additionally, reason cutting tool should be used strictly inside limits of its safety rotate speed. 2.
The mix of choice cutting tool that clip of 3 cutting tool runs a system runs a system (knife handle) it is a crucial part when high speed cutting, rising to transfer the function of machine tool precision and torsion. The one aspect of the matter of knife handle is machine tool main shaft, other one aspect of the matter it is cutting tool. The knife handle when structure of thin wall of high speed cutting must have high speed machine all requirements of knife handle, for example: Very good dynamic balancing character, tall geometry precision and outfit clip repeat the demand such as the very precision, tall stiffness that hold clip. At present the connection of knife handle and main shaft is on machine tool of cutting of most high speed with conic and hollow handle (HSK) give priority to. In addition, bilge through heat cold shrink principle and working shrink covers a knife to place a system to was in Cheng Fei company to also receive wider and wider application with its advantageous character. 3.
Cutting dosage is reasonable the choice of cutting parameter, the high accuracy that ensures thin wall structure is machined not only, and it is the efficiency of play of high speed machine tool, assurance that is in optimal job status. Because this cutting quantity wants a foundation material of length of diameter of machine tool tigidity, cutting tool, cutting tool, workpiece, rough machining or finish machining mode and calm. The basis becomes flying company about high speed of structural member of Bao Bi of plane aluminium alloy, freeboard fast a series of cutting test data such as milling of low cutting force are referenced foreign data, sum up each cutting dosage choose a principle to be as follows: (1) cutting speed V: The cutting rate that machines aluminium alloy was not limitted. From theoretic tell, use higher cutting rate, can improve productivity, can decrease or avoid to go up in front of cutting tool form the tumour that accumulate bits, be helpful for cutting the eduction of bits. Of milling rate raise cutting tool of undoubted meeting aggravate wear away, but, the rises to enhance power of unit quantum of time effectively metal excision of milling rate is led, can raise workpiece surface to machine quality inside limits of certain speed of high speed cutting at the same time. Structure of thin to many aviation aluminium alloy wall (the wall is large 1.
0 ～ 1.
5 the left and right sides) spare parts, cutting speed is fiducial choice with cutting force. When thin wall of high speed cutting, the condition with deep changeless Ae is cut in radial, radial cutting force follows rate basic and changeless, mean limits of optional cutting speed very big, the basis has facility, can in rotate speed 22000rpm chooses 12000 ～ . (2) feed Fz: Increase feed Fz to be able to increase cutting power undoubtedly, this is machined to Bao Bi apparently adverse. When reason finish machining, do not choose big Fz, but Fz is too small also be harmful, because Fz spends a hour, extruding replaced cutting, can produce a large number of heat in metal cutting, aggravate cutting tool wears away, the influence machines precision. So, when finish machining, should choose relatively the feed of moderate, can choose to be in commonly 0.
1 ～ 0.
Between 2mm/z. (3) axial cuts deep Ap and radial to cut deep Ae: No matter the angle from force, still wait for an element considering temperature of leftover stress, cutting, using small axial to cut deep Ap and big radial to cut deep Ae is advantageous apparently, this is principle of choice of parameter of the cutting below condition of high speed cutting. To Bao Bi structural sidewall is machined, the radial load that produces apparently below small Ap condition is small, and in Ap little state of affairs falls, the addition of the Ae inside certain limits can not increase Bao Bi to be out of shape, can take bigger Ae to undertake machining so; The abdomen to thin wall structure board treatment, last knife uses big Ap to be able to raise treatment system stiffness, reduce celiac board to be out of shape, so, bigger Ap should be chosen to undertake machining when machining celiac board. Usually, axial cuts deep Ap to be able to choose between 2 ～ 10mm, radial cuts deep Ae to be able to be in 0.
5 ～ 0.
Undertake choosing between 9D. Want to be aimed at different treatment object, personnel of need process designing chooses contrail of reasonable cutting tool motion, optimize cutting dosage, choose suitable cutting career according to need, only such ability produce the advantage of technology of high speed cutting truly. Pass into flying company in last few years exploratory study, experiment through many cutting, built the cutting parameter database that accords with characteristic of equipment, cutting tool, product, good application received in the CNC Machining such as project of subcontract of military plan, civilian machine. 4.
Part of construction of thin wall of aviation of program of technology of typical case of construction of thin wall of high speed cutting presses characteristic of its craft, structure, can divide for casing kind, bridge kind, wainscot kind wait for a type. In the treatment of part of thin wall construction that in a large number of application technology of high speed cutting has, summary formed typical craft plan. (1) bridge kind characteristic of structure of program of spare parts technology: Bridge kind spare parts cent is bosseyed reach double-faced, on appearance of this kinds of spare parts many place involves airframe theory exterior, spare parts abdomen board with the predestined relationship ply all lesser, it is commonly 1.
5 ～ 2mm is controlled, the smallest part only 1.
5mm, dimension public errand is ± 0.
15mm, material excision rate is achieved 96% the left and right sides. Technology program: Hold clip, the spare parts is placed for horizontal, use two aperture one side to locate, setting of two craft aperture is on craft protruding stage, position position is better. It is all round the spare parts setting impaction chamfer, jockey person needs chamfer of impaction of spare parts of the impaction before be being machined only, the outfit that need not change a part in treatment process again places condition. Craft course: Use high speed to machine a machine tool, because processing technique of high speed cutting has the characteristic of high rotate speed, fast feed, light cutting, the spare parts that after making machine thereby, appears is out of shape got better land is controlled, incorporate rough machining, half rough machining and finish machining accordingly for a working procedure, basic implementation arrives from semifinished product the one-time treatment of the spare parts. (2) casing kind characteristic of structure of program of spare parts technology: On appearance of this kinds of spare parts many place involves academic exterior, inside form have groove, cave in, shut the production feature such as stage of bevel angle, protruding. Spare parts abdomen board with the predestined relationship ply all lesser, it is commonly 1.
2 ～ 2mm is controlled, dimension public errand is ± 0.
15mm. Material excision rate is achieved 97% the left and right sides. Technology program: Hold clip, the spare parts is placed for horizontal. The spare parts uses two aperture one side to locate, setting of two craft aperture is on craft protruding stage, the major muscle as a result of the spare parts in same height, draft with muscle side fixed position. Because be in the part is larger, outfit clip disassembles no-go, use bolster plate tool, spare parts periphery sets craft protruding stage, make hole of heavy head impaction on craft protruding stage, whorl hole is made on bolster plate, secure with impaction of heavy head bolt go up in bolster plate tool. Craft course: Use processing technique of high speed cutting, incorporate rough machining, half rough machining and finish machining for a working procedure, arrive in order to come true from semifinished product the one-time treatment of the spare parts. Nextpage (3) wainscot kind characteristic of structure of program of spare parts technology: The spare parts is structure of double-faced chamfer antrum, without plane appearance, gush bolus figuration still needs after CNC Machining. Inside form include to have the geometrical feature such as stage of groove, cave in, protruding. Spare parts ply is thinner, groovy pitch is lower, major chamfer is deep be less than 3mm, spare parts abdomen board ply is inhomogenous, it is commonly 1.
5 ～ 3mm is controlled. Dimension public errand is ± 0.
2mm. Material excision rate is made an appointment with 90% . Technology program: Hold clip, because this kinds of spare parts completes treatment on vertical machine tool, accordingly the spare parts is placed for horizontal. Because the part is small, in machining a process extremely easy because of surplus purify not all and generation treatment is out of shape; And place of fixed position clamp is lacked on total construction, the abdomen that the spare parts when be being machined to decrease at the same time is out of shape and causes board ply exceeds small, use vacuum adsorption to machine. Craft course: Use processing technique of high speed cutting, incorporate rough machining, finish machining for a working procedure, treatment is sequential the choice is to machine the one side with little chamfer first, after machining this, be inside groovy antrum fill gesso, the fixed position that makes treatment searching an area is standard, all use vacuum adsorption to machine. 5.
The process designing of structure of thin wall of high speed cutting is politic (1) the technique that the process designing means that high speed cutting machines to the requirement high speed of CAM and method must process with high speed organic union, this raised taller requirement with respect to the CAM that machines to high speed. The CAM that high speed machines must satisfy the following requirement: The cutting condition with constant ① ; ② assures the biggest the cutting speed with stability; What ③ prevents acceleration of any cutter shaft shift is discontinuous with mutation; When cutting tool moves, ④ maintains constant main shaft feed, produce the cutting of identical bulk; Length of ⑤ cutting tool had better is less than with diametical comparing 10; ⑥ decreases to move without cutting; What ⑦ does not have perpendicular direction is jumpy; ⑧ does not have the revulsion of cutting direction; ⑨ falls in the premise that assures interpolation public errand, reduce paragraph of number as far as possible; ⑩ offers the digit of smooth suitable knife with successive height to occupy. ⑾ is cut automatically too (leftover) protective function. ⑿ system can provide the function of emulation test and verify. (2) the core that high speed cutting machines craft to the requirement high speed of cutting contrail is to make sure those who machine a process is successional as far as possible, make cutting tool is in feed movement condition constantly in milling treatment process, collect what consumed slips to enter, the means that retreat a knife, collect what consumed slips to move knife means and collect what consumed slips to turn knife. CAM satisfies the requirement of high speed cutting through special process designing kind and method, specific will come true through cutting contrail. Elaborate the cutting knife course that machines a requirement in the light of different high speed and drive method respectively below. Use process designing of method of corkscrewed yarn drive, cutting tool enters material to use successive helix and circular arc contrail to undertake milling as far as possible, in order to assure constant cutting condition; Climb slope to use one-way treatment, and do not use " " word treatment, avoid to go against mill, prevent radial to beat; Decrease to cutting tool is exited and enter the time of material afresh, maintain the cutting position with stable cutting tool, maintain cutting ply even; The curvature such as the corner when finish machining changes and cut the part with profound larger change to want foreclose, the made surplus that leaves to be the same as with other part photograph; Cutting contrail does not have mutation, contrail of cutting tool of the horn that do not have a needle is used in place of knife course turn; Rough machining should take the accuracy of appearance seriously, is not simple purify stuff, make sure mental allowance of follow-up working procedure is even. Surplus and cutting dosage should be united in wedlock with cutting parameter photograph, choose reasonable cutting parameter; Avoid cutting surplus mutation, when surplus increases, should lower feed rate, because of the change of bear, what can cause cutting tool is deflective, reduce treatment thereby quality of precision, surface and shorten cutting tool life; Use statified cutting; Have the place Xian Qinggen of protruding stage, avoid cutting tool stage of frequent collision protruding; Pass NURBS curve process designing, assured interpolation public errand already, can reduce block to count again (the interpolation that premise is curve of NURBS of support of system of machine tool control is calculated) . CNC Milling CNC Machining