The service life of NC punch die depends on reasonable die structure, high manufacturing accuracy, good heat treatment effect and correct selection of punch and installation accuracy of the punch. Besides, the correct use, maintenance and repair of the die can not be ignored. The following points should be noted:
(1) Before the installation and use of the mold, it should be strictly checked to remove the dirt, and check whether the guide sleeve and mold of the mold are well lubricated.
(2) Regularly check the rotary table of the press and the mold mounting base to ensure the coaxial accuracy of the upper and lower rotary tables.
(3) Install the male and female molds on the turntable according to the mold installation procedure to ensure that the direction of the male and female molds is consistent. Especially, the molds with direction requirements (non-circular and square) should be carefully installed to prevent incorrect and reverse installation.
(4) After the mold is installed, check whether the fastening screws of the mold installation base are locked correctly.
(5) The punch and die edges of the punch die should be stopped when they are worn, and they should be sharpened in time, otherwise the wear of the die edges will be rapidly expanded, the die wear will be accelerated, and the quality of the punch parts and the life of the die will be reduced.
(6) For the general molds used for mass production, there should be a backup to facilitate the rotation of production and ensure the production needs.
(7) The stamping personnel shall use soft metal (such as copper, aluminum, etc.) to make operating tools when installing the mold, so as to prevent damage to the mold when knocking or smashing during installation.
(8) The mold shall be handled with care during transportation, and it is not allowed to throw or touch the mold, so as to avoid damaging the cutting edge and guide of the mold.
(9) The mould shall be put back to the designated position in time after use, and shall be oiled for rust prevention.
(10) To ensure the service life of the mold, the spring of the mold should also be replaced regularly to prevent the fatigue damage of the spring from affecting the use of the mold. Common Problems in the Use of Punch Die
(1) The punch wears too fast
Main reasons: ① The die clearance is too small. It is generally recommended that the total die clearance is 20%~25% of the material plate thickness. ② Poor alignment of convex and concave dies, including insufficient precision of die base, die guide component and turret insert sleeve, etc. ③ The punch temperature is too high, mainly due to the overheating of the punch caused by the continuous stamping of the same die for a long time. ④ The improper grinding method of the die causes the die to be annealed and wear to be aggravated. ⑤ For partial unilateral punching, such as step punching, punching angle or shearing, the lateral force will make the punch deflect to one side, and the clearance of this side will be reduced, resulting in severe wear of the die. If the installation accuracy of the machine tool die is not high, the punch will deflect over the lower die, causing damage to the male die and female die.
(2) The mold carries the material problem
The die strip will cause the waste to rebound, and the related factors are: ① The sharpness of the die edge, the larger the fillet of the edge, the easier it will cause the waste to rebound. ② The input modulus of the mold and each station of the machine tool are fixed. The input modulus of the mold is small, which is easy to cause the rebound of waste materials. ③ Whether the die clearance is reasonable, if the die clearance is not appropriate, it is easy to cause scrap rebound. ④ Whether there is much oil on the surface of the processed plate. ⑤ The spring is damaged due to fatigue.
Methods to prevent the die from carrying material: ① Use a special anti carrying material die. ② The mold is often sharpened to keep sharp and demagnetized. ③ Increase the die clearance. ④ The die with inclined cutting edge is used to replace the die with flat cutting edge. ⑤ Die mounted ejector. ⑥ Reasonably increase the mold modulus. ⑦ Check the fatigue strength of the die spring or discharge sleeve.
(3) Mold pair neutral problem
During the use of the die, it is easy to have different wear amount at each side of the punch core. Some parts have large scratches and wear quickly, which is especially obvious on narrow rectangular dies. The main reasons for this problem: ① The design or processing accuracy of the machine tool turret is insufficient, mainly due to the poor alignment of the mold mounting base of the upper and lower turntables. ② The design or processing accuracy of the die can not meet the requirements. ③ The precision of the guide sleeve of the die punch is not enough. ④ Improper die clearance selection. ⑤ The mold mounting base or mold guide sleeve is not well aligned due to long-term wear.
In order to prevent inconsistent wear of the die, it shall: ① Regularly use centering mandrel to check and adjust the centering of the machine tool turret and mounting base. ② Timely replace the die guide sleeve and select the convex and concave die with proper clearance. ③ Adopt full lead die. ④ The operator’s sense of responsibility shall be strengthened, and the cause shall be found in time after discovery to avoid greater losses.
(4) Use of special forming dies
In order to meet the production needs, it is often necessary to use forming molds or special molds, mainly including bridge shaped molds, shutter molds, counterbore molds, flanging and threading molds, boss molds, stretching molds, combined molds, etc. The use of special or forming molds can greatly improve the production efficiency, but the price of forming molds is high, usually 4-5 times that of ordinary molds. To avoid mistakes, the following principles shall be observed:
① Check the direction when installing the mold to ensure that the installation direction of the male and female mold is consistent.
② The stamping depth of the die shall be adjusted correctly according to the requirements, and each adjustment shall not exceed 0.15 mm.
③ Use a lower blanking speed.
④ The plates shall be flat without deformation or warping.
⑤ The forming position shall be as far away from the clamp as possible.
⑥ The downward forming operation shall be avoided when the forming die is used.
⑦ When stamping, the common die shall be used first, and then the forming die shall be used.