1、General all-steel punching dies punching accuracy Accuracy of panel punching part is display the press accuracy of the die exactly. But the accuracy of any punching parts linear dimension and positional accuracy almost depend on the blanking and blanking accuracy,. So that the compound mould of comp
2、ound punchings accuracy, is typicalness and representation in the majority. Analyse of the dies accuracy For the analyse of pracyicable inaccuracy during production of dies to inactivation, we could get the tendency when it is augmentation in most time. From this we could analyse the elements. When
3、the new punch dies pt into production to the first cutter grinding, the inaccuracy produced called initial error； if the die grinding more than twenty times, until its discard, the inaccuracy called conventional error； and before the dies discard, the largest error of the last batch permit, called l
4、imiting error. at job site, the evidence to confirm life of sharpening is the higher of the blanking, punched hole or punched parts. Because all finished parts had been blanked ,so it is especially for the compound dies. Therefore, the analyse of burr and measurement is especially important when do
5、them as enterprise standardization or checked with . The initial error usually is the minimal through the whole life of die. Its magnitude depend on the accuracy of manufacture, quality, measure of the punching part, thickness of panel, magnitude of gap and degree of homogeneity. The accuracy of man
6、ufacture depend on the manufacture process. For the 1 mm thicked compound punching part made in medium steel, the experimental result and productive practice all prove that the burr of dies which produced by spark cutting are higher 25%30% than produced by grinder ,NC or CNC. The reason is that not
7、only the latter have more exact machining accuracy but also the value of roughness Ra is less one order than the formmer, it can be reached 0.025m. Therefore, the dies initial blanked accuracy depends on the accuracy of manufacture, quality and so on. The normal error of the punch die is the practic
8、able error when the fist cutter grinding and the last cutter grinding before the die produce the last qualified product. As the increase of cutter grinding, caused the measure the nature wear of the dies are gradual increasing, the error of punching part increase also, so the parts are blew proof. A
9、nd the die will be unused. The hole on the part and inner because the measure of wear will be small and small gradually, and its outside form will be lager in the same reason. Therefore, the hole and inner form in the part will be made mould according to one-way positive deviation or nearly equal to
10、 the limit max measure. In like manner, the punching parts appearance will be made mould according to one-way negative deviation or nearly equal to limit mini measure. For this will be broaden the normal error, and the cuttergrinding times will be increased, the life will be long. The limit error in
11、 punching parts are the max dimension error which practicable allowed in the parts with limit error. This kind of parts usually are the last qualified products before the die discard. For the all classes of dies, if we analyse the fluctuate, tendency of increase and decrease and law which appeared i
12、n the dies whole life, we will find that the master of the error are changeless； the error that because the abrade of the cutter and impression will be as the cutter grinding times increased at the same time. And that will cause the error oversize gradually； and also have another part error are unco
13、nventional , unforeseen. Therefore, every die s error are composed of fixed error, system error, accident error and so on. 1. fixed error At the whole process when the New punching die between just input production to discard, the changeless master error that in qualified part are called fixed error
14、. Its magnitude is the deviation when the die production qualified products before the first cutter grinding. Also is the initial error, but the die have initial punching accuracy at this time. Because of the abrade of parts, the die after grinding will be change the dimension error. And the increme
15、nt of deviation will oversize as the times of cutter grinding. So the punching accuracy after cutter grinding also called “grinding accuracy” and lower tan initial accuracy. The fixed error depend on the elements factor as followed : (1) the material , sorts, structure, (form) dimension, and thick o
16、f panel the magnitude of punching gap and degree of homogeneity are have a important effect for the dimension accuracy. Different punching process, material, thick of panel, have completely different gap and punching accuracy. A gear H62 which made in yellow brass with the same mode number m=0.34, 2
17、mm thick and had a center hole, when the gap get C=0.5%t (single edge) , and punched with compound punching die, and the dimension accuracy reached IT7, the part have a flat surface ,the verticality of tangent plane reached 89.5, its roughness Ra magnitude are 12.5m, height of burr are 0.10mm； and t
18、he punching part are punched with progressive die, the gap C=7%t (single edge) , initial accuracy are IT11, and have an more rough surface, even can see the gap with eyes. In the usual situation, flushes a material and its thickness t is theselection punching gap main basis. Once the designation gap
19、 haddetermined flushes the plane size the fixed error main body； Flushesthe structure rigidity and the three-dimensional shape affects itsshape position precision. (2) punching craft and molder structure type Uses the different ramming craft, flushes a precision and the fixederror difference is real
20、ly big. Except that the above piece gearexample showed, the essence flushes the craft and ordinary punching flushes a precision and the fixed error differs outside a magnitude,even if inordinary punching center, uses the different gap punching, thefixed error difference very is also big. For example
21、 material thickt=1.5mm H62 brass punching, selects C = the 40%t unilateral I kind ofsmall gap punching compared to select C 4mm flushes, the size precision can lower some. Different dies structure type, because is suitable the rammingmaterial to be thick and the manufacture precision difference, cau
22、sesto flush a fixed error to have leaves. Compound die center, multi-locations continuous type compound die because flushes continuously toduplicate the localization to add on the pattern making error to bebigger, therefore it flushes a fixed error compound punching die to wantcompared to the single
23、 location Big 1 2 levels (3) the craft of punching dies manufacture the main work of punching die namely are raised, the concave moldprocessing procedure, to operates on the specification not to behigh, can time form a more complex cavity. But its processing surfaceapproximately is thick 0.03 0.05mm
24、 is the high temperatureablation remaining furcated austenite organization, degree ofhardness may reach as high as HRC67 70, has the micro crack, easilywhen punching appears broke the cutter or flaking. The Italian CorradaCorporations related memoir called the line cut the processing contruction to
25、have the disadvantageous influence to the superficialgold, in fact already changed the gold contruction. We must use theJingang stone powder to grind or the numerical control continual pathcoordinates rub truncate (cut to line) to make the precision work . In recent years country and so on Switzerland and Japan, has conductedthe thorough research to the electrical finishing equipment and abigger improvement, makes function complete high accuracy NC and theCNC line cutter, the processing
