Search coating of better miniature cutting tool
- source:EASCOR CNC Machining
Introduction Pfefferkorn, one of purposes of this experiment are a kind of machinery is founded to connect between hard alloy matrix and diamond coating. Pfefferkorn and project of machinery of guest state university and application are mechanical Robert W of department associate professor.
Carpick (he in Weisikang astral university Mai Dixun distributes the research that diamond coating ever devoted oneself to when school) reach its graduate student and partner to be in a problem " diamond coating miniature establishs milling cutter: Can right aluminous undertake small size does cutting " paper middle finger goes out, cobaltic bond can enhance the tenacity of cutting tool, but can weaken the combinative strength between diamond coating and matrix, be formed through restricting nucleus and restrain the growth of diamond. Pfefferkorn expresses, "The main reason from cobalt of matrix surface purify is it can hamper diamond grows. " go when cobaltic processing, need etchs selectively the properest amount that contain cobalt, and won't weaken the miniature cutting tool with very fine already itself overly. To prevent purify too much cobalt affects the integrality of cutting tool, the quantity containing cobalt of cutting tool (weight is compared) must not exceed 6% - 8% . Pfefferkorn says, "The cobalt in our very will thin surface layer etchs entirely, grow in order to prevent what it affects diamond process. We etch through control deepness, make its fall to the influence of cutting tool integrality to the smallest. " this paper points out, astral university Mai Dixun divides Weisikang the research group of school is finishing after etching, undertook brilliant operates bringing: Ultrasonic processing is used in acetone, with accept rice diamond pink is on matrix deposit diamond is atomic. The grain of introduce a fine variety had fixed position effect, diamond begins to grow in the place (namely form nucleus) . Accept rice diamond pink agglomerates can bring about make crystal inhomogenous, the growth that causes diamond is inhomogenous, accordingly, researcher uses the method that undertakes in alcohol solution ultrasonic is cleaned, in order to ensure the grain conglomeration with big purify, come true to make crystal equably thereby. Next, the heater chemistry gas phase that uses this research to group proper motion is designed and be made is deposit system, grow on cutting tool gave Na Mijing bead and fine grained diamond (Carpick affirms, the granuality of diamond of accept rice grain is 10 - 100nm, the granuality of fine grained diamond is more than 100nm, be less than 300nm) . This deposit system includes a deposit room, among them, temperature maintains at least protective gas is full of all round the tungsten filament in 1800 ℃ (be in especially hydric in the firedamp that dilute crosses) . The coating ply that deposit gets is about 60 - 200nm. The diamond coating ply of common cutting tool is 2 μ M or thicker, and this to miniature cutting tool Yan Taihou, because not the cutting blade radius of coating miniature cutting tool still often is less than 1 μ M. Carpick says, "The coating ply that is used at large scale cutting tool does not suit completely to use Yu Wei cutting tool, it will make cutting tool passivation, reduce its cutting performance greatly accordingly " . Pfefferkorn thinks, in fact, what the geometrical feature of miniature cutting tool does not hope like place is accurate in that way, "To the load cutting bits that produces when cutting, what what the cutting blade radius that miniature establishs milling cutter has expected than us is bigger " . Besides cooperate with the researcher that has heater CVD deposit experience beyond, this group chooses this kind of deposit technology, because use other CVD method,be (if be based on the deposit method of plasma) deposit coating ply change is bigger, more material is in by deposit on point of a knife, pfefferkorn says, "Grow on sharp cutting blade give a conglobation, resemble dog character same. I am not to say heater CVD is the method that can use exclusively, because it won't produce this to plant,a ground that chooses this method is ' dog bone effect ' . " coating wants not only thin, and must have good adhesiveness with matrix, still should mix continuously at the same time smooth, although hind a kind of character is quantified very hard. Carpick says: "To smooth sex, we are removing pair of limit that build appropriate model hard, accordingly, we still cannot be cut truly know coating needs to have many smooth. We also think, somewhat coarse likelihood is beneficial, because it conduces to probably,prevent workpiece material felt to arrive on cutting tool. " because coating of diamond of accept rice grain is very OK thin, because this can get used to appearance of matrix surface form, include what treatment of cutting tool grinding arises to grind the crackle that mark and acid etching processing cause, micron grain coating can cover these exterior flaw. Pfefferkorn says, "Miniature cutting tool has comparatived coarse, we do not need to make them coarser. " aluminous treatment establishing mill introduces according to Carpick, the research of this group is using coating miniature to establish milling cutter to process 6061-T6 aluminous data centrally mainly, because industry hope increases this material in all sorts of spare partses (include engine cylinder body) the application in making. In addition, aluminous very easy felt arrives on hard alloy cutting tool, but not easy felt arrives on diamond cutting tool, the coefficient of friction because of diamond lesser, caking property is inferior. Experiment to undertake cutting, researcher installed drive of a report and the main shaft of report of NSK-HES500 high speed that take bearing of pottery and porcelain on Ha Si TM-1CNC Milling. In full trial, the rotate speed of main shaft of this high speed is 40000rpm, give feed rate to be 500mm/min. Company of Performance Micro Tool offerred miniature to establish milling cutter for the experiment. The experiment uses dry cutting, but the humidity control system that one suit has two spray head blows humid air to pass point of a knife. Carpick says, "The wet attrition that machines an environment to be able to reduce cutting tool significantly and wear away. " " when dry cutting, the cutting force that brings to bear on to go up at diamond coating cutting tool wants under with not cutting tool of coating hard alloy cools in cutting fluid sparge the cutting force when cutting undertaking below the condition. " Pfefferkorn complement says, no matter whether use refrigeration of cutting fluid sparge, metropolis conglutinate is in aluminous bits not on coating cutting tool. In " diamond coating miniature establishs milling cutter function to analyse " mix to cutting force in the paper the analysis of axial thrust data shows, use respectively not coating establishs milling cutter, 0.
5 - the coating of fine grain diamond with 1 μ thick M establishs the Namijin with milling cutter and thick 200nm when firm stone coating establishs milling cutter to do milling 6061-T6 aluminium, wants cutting force size has clear improvement: Advocate cutting force and axial thrust part never 2 of coating cutting tool.
14N (± 0.
85N) with 4.
40N (± 0.
44N) fall 0 to cutting tool of coating of fine grain diamond.
49N (± 0.
09N) with 0.
34N (± 0.
04N) , and cutting tool of coating of accept rice diamond is farther reduce cutting force and axial thrust to 0.
18N (± 0.
07N) with 0.
17N (± 0.
02N) . These data make clear, the cutting force of coating cutting tool and axial thrust are more balanced, and not double the axial thrust of coating cutting tool is cutting force however. Of cutting force reducing should be attributed to the attrition with diamond smaller coating and felt. Accordingly, pfefferkorn suspicion, aluminium produces felt easily with hard alloy is to use not the reason with bigger thrust of the axial when cutting of coating cutting tool. Establishing mill is process of a kind of interrupted cutting, rotate in 180 ° only as a result of cutting blade workpiece of the cutting inside limits, consequently very few generation cuts bits continuously. And when doing cutting, not coating establishs milling cutter to also can arise to cut bits continuously now and then, because the felt cutting bits of a new generation is discharging bits chamfer surface,this is, in next new generation cut bits to be pushed to it, after with it solder is together, just basically be taken away. Pfefferkorn thinks, "Must have enough great force gift makes cut bits mutual elbow " . Small milling experiment returns discovery, the knife mark that diamond coating establishs milling cutter to machine the surface is more regular, evener, and not the treatment surface of coating cutting tool is bright and clean degree inhomogenous, this makes clear a large number of heat in metal cutting arose in cutting process. Carpick says, "The quantity of heat of the generation in cutting has very big effect to miniature knife, it is especially in high speed treatment. " Nextpage should study the paper points out, these function promotion are in only the durability of diamond coating is enough the ability when growing is obtained. The cutting tool of coating of fine grain diamond that has 80% about and the cutting tool of coating of accept rice diamond of 40% appeared coating flakes phenomenon, and after this kind of circumstance happens in cutting to begin a few minutes normally. After coating flakes, original coating cutting tool perhaps is shown with not the performance with coating similar cutting tool, produce complete invalidation suddenly perhaps. Accordingly, next need consider how to improve the conglutinate performance of coating. Reduce the heat in metal cutting that heat in metal cutting produces about be when small cutting, a few otherer the investigator of the university reached different conclusion. General crosses the research of the university to think, miniature cutting cutting tool won't produce a large number of heat in metal cutting. General crosses university machinery to be versed in Cheng technology fastens associate professor Mark Jackson to express, because miniature cutting tool needs high speed to rotate,this is, any quantity of heat of generation are cut instantly bits is taken away together, these cutting although bits is very petty, but have very big surface to accumulate / bulk comparing. Jackson says, "The action of coating is not to take away quantity of heat, the quantity of heat that produces because of place is very small " . He points out, when treatment, limits of main shaft speed is 250000 - 750000rpm (depend on workpiece material and load circumstance) , temperature of point of a knife is 27 - 33 ℃ . The general before ever was engaged in what coating studies together with Jackson crosses university doctor Grant Robinson to agree with this one viewpoint, "The coating that designs to decrease and take away quantity of heat below macroscopical measure is done not have completely below microcosmic measure necessary, because be below microcosmic measure, heat in metal cutting is not to cause cause of cutting tool tatty. Main reason is by mechanical power (and be not heating power) the mechanical wear that cause " . Accordingly, he points out, the coating that uses Yu Wei cutting tool needs to be used at improving the wearability of cutting tool only. To decide the temperature rise when small treatment, the researcher that general crosses an university undertook finite yuan of computation, considered to be machined the element with a few relatively inferior melting point in material (wait like sulfur, calcic, Potassium) . Robinson explanation says, "If be when the element that machines a kind of melting point to be 50 ℃ , saw fused sign (like small fused droplet) , can say cutting temperature is 50 ℃ about. But the sign that we did not see any fusing, accordingly we conclude, small measure cutting won't produce a large number of heat in metal cutting. " because cutting temperature is inferior, because this adds man-hour not to need to use cooling fluid, but the researcher that general crosses an university will compress air to be brought to cutting area, with helping a platoon bits is mixed make workpiece material quickens oxidation. Jackson explanation says, "If the metal does not have fast oxidation, coefficient of friction can increase (including coating cutting tool even also is such) , bring about temperature to lift thereby, because such meetings produce the felt of metal and metal, the felt that is not metal and oxide " . The metal that the experiment machines includes steel of tool of 1020 mild steel, D-2, copper, brass and the soft material with all sorts of can rapid sclerotic meet an emergency, wait like niobium, Tantalum, tungsten. Researcher basically experimented to be able to offer commerciality application, diameter 250 - the hard alloy of 750 μ M establishs milling cutter, these cutting tool are sent there a business of main cutting tool coating to have PVD coat. Coating sort includes TiN, TiAlN, AlTiN, TiAlCrYN, CrN and TiAlCrZrN. Jackson says, "We experimented 20 - 30 kinds of coating. " to avoid passivation cutting blade, control of coating ply limits is in 300nm - 2 μ M, and its and ply limits 3 - the coating of groovy cutting tool of 5 μ M undertook contrast. The other issue beyond coating and those think to be in small treatment, cutting tool coating can raise productivity and the notion that prolong cutting tool life contrary, robinson thinks, cut to be formed effectively bits and have small treatment correctly, miniature cutting tool must from go up to undertake designing afresh at all. Because,this is, when the cutting tool that designs with convention undertakes microcosmic measure is machined, need overcomes point radius and the scale problem of the ply that cut bits. His explanation says, to the radius of cutting blade circular arc with specific some, also have specific not cutting is the smallest the ply that cut bits. "Change character, to some point radius, must have a specific material cutting depth, ability is formed cut bits. " he continues to explain say, in fact, what miniature cutting tool rotates so is fast, so that every turn only may ongoing 1nm, and to not cutting cuts bits ply and character, want to reach the critical level that forms the place that cut bits to need, this one distance is far insufficient. Rotate to advance at the same time at the same time when cutting tool when, just grinding (is not cutting) workpiece material. In achieve before forming the critical cost that cuts bits, the likelihood needs to rotate hundreds turn -- perhaps need not so much. Robinson says, "I do not think somebody had found out point radius and the critical cost that the ply that cut bits compares. " and without this one information, have coat to the miniature cutting tool that designs by groovy method, will hamper it is cut correctly further cut. "In small cutting domain, the problem that still has mechanism of many concerned cutting was not obtained solve, probably I still need to continue to be this business 30 years. " Jackson says so. Reasonable choose Jeff Davis of vice president of technology of company of cutting tool of Harvey of coating of miniature cutting tool to think, cutting tool coating is special the imperceptible treatment that is beneficial to difficult treatment material, "Those difficult treatment material contain a large number of nickel and cobalt, need to be machined with coating cutting tool normally. " nevertheless, to other material criterion cannot so say. Davis points out, "When aluminous or cutting is plastic, not was necessary for certain or need not requisition coating, with not aluminium of cutting of coating cutting tool already made a rule. " but also have exception, hope to reduce the manufacturing workshop that changes a knife as far as possible namely. Below this kind of circumstance, the ZrN that uses PVD deposit or TiB2 coating are more appropriate. Coating system and Gary Lake of president of company of service supplier CemeCon also agree with TiB2 coating to suit to be used at cutting aluminium alloy, but content of silicon of be confined to under the workpiece material of 10% . He says, when the silicon content prep above in aluminium alloy 10% when, tiB2 coating prevents workpiece material and cutting tool material effectively to produce felt and move hard. Accordingly, when silicon content prep above 10% when, in view of the abrasion of workpiece material, should use cutting tool of CVD diamond coating. Davis says, most coating company uses technology of deposit of cathode electric arc at all sorts of coating, can evaporate the target material of 90% above to arrive with deposit on cutting tool because of this method, compare with other method photograph, material is wasteful and very few. "In addition, the kinetic energy that concerns with this craft makes coating has very good conglutinate power. " the defect of craft of deposit of cathode electric arc is bulky grain can produce when deposit and smooth coating. Davis plants this bulky grain described as " melt droplet " , it is a kind of commonly used coating element -- titanium. It resembles the droplet that little splatters almost. This kind of droplet won't hamper possibly the control cutting bits of bigger cutting tool, but when cutting tool dimension more and more hour, its are negative action becomes more and more apparent, right now, business of cutting tool coating needs to adjust craft, make droplet size the smallest change or avoid occurrence droplet. Davis complement says, still have a kind of choice, be in after coating namely the premise that maintains coating integrality goes down to divide this kind of droplet. Davis says, if these bulky grain maintain same basic measure, the exterior grain of cutting tool can become not smooth, possible meeting hook cuts bits and make the extruding that cut bits is together. Lake expresses, "The bulky grain in coating is machined to small size cannot be accepted completely. When using coating of deposit of craft of cathode electric arc, final meeting gives the bulky grain that shows metallic photograph to be stuck in coating surface, because miniature cutting tool is very fine, cannot pass polishing purify bulky grain, resemble be being done to place of larger size cutting tool normally in that way. " Lake proposal, the ion that can offer with CemeCon company is splashed shoot craft to replace craft of cathode electric arc. Ion is splashed shoot suit coating of deposit miniature cutting tool more, because it is OK,deposit gives the smooth scumble layer that does not have bulky grain, coating ply can maintain in about 1 - between 2 μ M. Lake complement says, establish milling cutter to undertake coating basically is to improve productivity to hard alloy miniature, machine the cutting tool of material hard to those at cutting using especially. "If be opposite correctly coating of cutting tool of hard alloy miniature, will improve its performance, to cutting tool of any other hard alloy as much such. " the technical difficulty that has coat to miniature cutting tool no matter for the moment, a lot of commerciality coating companies are opposite the coating of this kind of cutting tool is indecisive, because be in unit process of cargo bandling,return, these fine and flimsy cutting tool are damaged very easily. According to Introduction Lake, in coating craft, want to implement 3 operations measure to cutting tool at least, it is take out cutting tool from the one by one in packing, move send to clean frame on; 2 it is cutting tool move arrives on the clamping apparatus of coating device; 3 be in packing cutting tool replace, so that over there carry back manufacturer. "If deliver the cutting tool of coating in good condition nondestructive, and you in coating process lieutenant general its damage, you need to compensate for. " if miniature tool him manufacturer has coating facility, this won't become an issue, but most manufacturer does not have this kind of equipment, because this can be relied on only,may damage more or less the exterior resource of a few cutting tool. Lake estimation, because be in,difficulty exists on coating technology, the miniature cutting tool that has 95% about does not have coating. Company of Harvey cutting tool gives other company the package outside the coating of its miniature cutting tool, and Davis expresses, it is OK to find very hard the miniature cutting tool with appropriate flimsy processing is willing to be opposite the company of its coating, "Cutting tool size is smaller, coating company damages his more likely. Coating company damages his more likely.. CNC Milling CNC Machining