Of hard alloy and high-speed steel cutting tool be ground again and again coating is current common craft. Although cutting tool is heavy,be ground or again the one fraction that the price of coating makes cost for new cutting tool only, but can prolong cutting tool life however. Weighing grinding work art is special cutting tool or price the typical processing technique of costly cutting tool. Can undertake weighing grinding or again the cutting tool of coating includes broach, milling cutter, hob and figuration cutting tool to wait. Of cutting tool grind again in broach or milling cutter in grinding a process again, blade of need grinding cutting with eliminate former coating, because what this uses,emery wheel must have enough hardness. The pretreatment that grinds pair of cutting blade again is very crucial, the geometrical appearance of primitive cutting blade after wanting to make sure cutting tool is ground again not only can be withheld by completely accurate ground, and the requirement is ground again must be to PVD coating cutting tool " safe " . Accordingly, must prevent unreasonable grinding craft (for example: The kibble that high temperature brings about cutting tool surface layer to be damaged or dry grind) . Cutting tool of gear of high-speed steel of coating of graph 1 TiN pursues 2 coating are aged by the shave of coating of comparative figure 3 TiN of purify around the purify of knife coating is in cutting tool again before coating, all coating with original purify of usable and chemical method. Chemical purify law is commonly used at complex cutting tool (be like) of hob, broach, or for many times the cutting tool of answer besmear and the cutting tool that produce a problem because of coating ply. The method of chemical purify coating is confined to high-speed steel cutting tool normally, because this method can damage hard alloy matrix: Use law of chemical purify coating to will divide cobalt from the filter on hard alloy matrix, cause matrix appearance down to of stoma of loose, generation undertakes hard again coating. "Chemistry goes to what be used at high-speed steel hard coating except law first selection corroding purify " technical officer Mr Dennis Quinto of coating company points out Baerchasi. "Because be contained in hard alloy matrix with the similar chemical class status in coating, because this is chemical,purify dissolvent damages hard alloy matrix more easily and not be high-speed steel matrix " . "The time that cutting tool keeps in coating purify solution is crucial " vice-president Mr Bill Langendor Fer of Venus coating company points out. "The time that takes cutting tool in solution is longer, to cutting tool corrode more serious. Although be opposite high-speed steel, corrode rate should low much, but still be answered to take out cutting tool hand-in-hand travel to clean instantly by purify hind when the former coating on cutting tool " . in addition, still a few apply to the has patent chemical method of purify PVD coating. In solution of purify of the coating in these chemical methods and hard alloy matrix only and tiny chemistry reacts, but at present these methods had be notted use extensively. Additional, still other cleans the method of coating, if laser beam machining, abrade gush is arenaceous,wait. Chemical purify law is the most commonly used method, because it can offer consistency of good exterior coating purify. is current and typical again coating craft is grind craft purify cutting tool through weighing original coating. Again the cutting tool coating with the commonnest economy of coating has TiN, TiC and TiAlN. Other exceeds hard nitrogen / the coating of carbide also has application, but not quite general. Cutting tool of PVD diamond coating also can undertake weighing grinding mixing again coating. Be in again in coating process, cutting tool should by " protect " in order to avoid the loss of critical surface. often has this kind of case: The user was bought not after the cutting tool of coating, have coat again when cutting tool needs to be ground again, or the coat that has differring on new cutting tool or the cutting tool after be being ground again. Mr Bill Langendorfer says: "Below a lot of circumstances, the TiN coating on our purify cutting tool, coating of the TiAlN on recoat. Because the user hopes to improve the manufacturing efficiency of cutting tool, and TiAlN coating tool compares rate of cutting of TiN coating tool taller, more high temperature resistant also. It is OK that the user often hopes from the acquired character can be better new coating cutting tool over there tool manufacturer, accordingly ' the new cutting tool that tool manufacturer must develop a kind possibly to contain TiAlN coating afresh ' . But with new development photograph of this kind of new cutting tool is compared, go from old cutting tool divide TiN coating and the time that place of coating of the TiAlN on besmear spends wants short much. " again the limitation of coating can be ground again for many times like a cutting tool same, the cutting blade of cutting tool also can have coat for many times. And " the cutting tool face that has wearinging again obtains the coating with adhesion good performance is the key that improves cutting tool performance. " chief inspector of sale of home of IonBond LLC company Mr Rob Bokram points out. Divide cutting blade beyond, repair every time in cutting tool when grinding, the others of cutting tool surface perhaps does not need purify coating or again coating, this depends on the cutting parameter that uses in the type of cutting tool and treatment. Hob and broach are to make purify needs when coating again the cutting tool of all former coating, otherwise cutting tool function will be reduced. Before the conglutinate problem that causes in stress becomes outstanding, cutting tool can undertake a few a few again coating and do not want eliminate old coat. Although PVD coating has the remains that is helpful for metallic cutting to press stress, but this kind of pressure can increase along with the addition of coating ply, the coating after the bounds that and be in exceeds a certain to secure is worth will begin to appear statified phenomenon. In not purify old coating and undertake again when coating, a ply increased on the external diameter of cutting tool. To broach, the aperture that means place getting is in greaten. Because this must consider coating additional the ply influence to cutting tool external diameter, consider this both to be opposite even at the same time by the influence of public errand of treatment aperture dimension. A broach can be in not below the circumstance of purify old coating again coating 5 ～ 10, but serious error problem will be faced after this. Dennis Klein of vice president of Spec tool company thinks: Inside the error limits of ± 1µm, coating ply won't become an issue; But be in when the error 0. 5 ～ 0.
Inside 1µm limits when, must consider the impact that coating ply brings. Want coating ply not to become an issue only, so again it is better that the coating, cutting tool that grinds again compares original performance completely possibly. CNC Milling
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