Small hole blanking die for the hottest thick plat

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Thick plate small hole blanking die

1 introduction

Figure 1 shows the key parts on electrical appliances, which require a large output. The material is 35 steel, the material thickness is 5.4mm, and it is quenched and tempered before processing. The hardness is 17 ~ 23hrc. The six expensive 5.20+0.15mm through holes on it are the key holes for part assembly, and the position accuracy is required to be high. In the past, the drilling process has been adopted: the size of each step is processed in place (CNC lathe) → drilling 6 pre holes (4mm bench drill) → expanding 6 holes (5.20+0.15mm bench drill) → subsequent processes. The production efficiency is low, and there are shortcomings such as poor position accuracy and difficult to control the aperture, which can not meet the requirements of mass production. After analysis, a small hole blanking die is designed. After trial production, it basically meets the requirements of the product drawing, the production efficiency has been greatly improved, and certain economic benefits have been achieved

Figure 1 part

2 process analysis

the main differences between small hole blanking and ordinary blanking are: ① punch needs a reliable guide structure; ② The pressing force is large, about 10% - 15% of the punching force; ③ The blanking clearance is very small, about 1.7% of the material thickness; ④ The unloading accuracy of the die is good

considering the actual situation of the factory and the process requirements of the product, the die is designed to be produced on an ordinary 1000KN punch. For the punch, a full-length guide structure with high accuracy is not used, but a pair of small guide posts are added between the pressing plate and the upper template to improve the operation accuracy of the punch in the whole process of blanking

in order to make the product material under three-dimensional compression during blanking and reduce the influence of uneven force on the punch caused by the tensile action of the material at the initial stage of blanking, the heavy loaded rectangular spring made in Japan is selected as the medium pressure spring in the design, and the instant the punch contacts the material, the pressing force is about 72kn

for the blanking clearance, according to the information, 2z=0.017t=0.0901mm, but considering the processing accuracy of the mold and the manufacturability of the product (the two sides of the hole should be inverted 1mm × 45 ° angle), if the blanking clearance is designed and processed completely according to the data recommendation, the wear of the punch may be aggravated, and the requirements for machining accuracy and the accuracy of setting and closing the oil return valve and opening the oil delivery valve to raise the table are too high; However, if the blanking clearance is blindly increased, the length of the bright band of the product will not be enough to meet the product quality requirements. After many debugging in the actual trial production, it is found that the blanking gap is controlled at 2z=0.15 ~ 0.2mm, and the bright band of the hole is about 80% of the material thickness, which can meet the product requirements

punch length check:

lmax ≤ 270d2/p

where D - minimum diameter of punch

p - blanking force

lmax - minimum allowable free length of punch

blanking force p=1.3 τ t × six × 2πR=405kN,d= 5.3mm。

Lmax ≤ 60mm is obtained by substituting each value into the formula. In the design, the punch adopts stepped punch, so it is completely feasible

punch press stress check:

d ≥ 4T τ/σ Press

where T - material thickness τ—— Shear strength of materials σ Pressure - allowable stress of punch material D - minimum diameter of punch, and the corresponding experimental results are displayed at the same time

the values are obtained by substituting them into the formula σ The blanking requirements can be met only when the pressure is ≥ 2350mpa. In the trial stage of the die, because there is no material that can meet this condition, the punching punch temporarily adopts high-quality alloy tool steel Cr12MoV

3 mold design

3.1 mold working process

Figure 2 is the mold structure diagram. Place the workpiece on the tripper and position it by the female mold. When the upper die goes down, the pressing plate first presses the workpiece to make it close to the concave die surface, and the upper die continues to go down, increasing the pressing force for blanking. After blanking, the upper die goes up, the pressing spring helps the punch withdraw from the material, and the unloading spring pushes the workpiece out of the concave die surface

Figure 2 mold structure

1 Lower mold base 2 Special nut 3 Unloading spring 4 Unloader 5 Punching die

6 Guide post 7 Guide sleeve 8 Punching punch 9 Limit screw 10 Pressing spring

11 Upper mold base 12 Floating die handle 13 Backing plate 14 Fixing plate 15 Small guide post

16 Small guide sleeve 17 Pressing plate

3.2 design of mold parts

(1) the design and manufacture of punch is the key of this mold. As shown in Figure 3, punch consists of three steps. There is no stress concentration point at the connection of each step, and all parts at R are ground by grinder and polished. The blanking edge is smoothly transited by r0.1mm fillet, and sharp edges are not allowed. The size of the edge is 5 0150mm。 In addition, the hardness of punching punch should not be too high, and the hardness should be controlled at 55 ~ 58hrc

Figure 3 punch

(2) the length of the four limit columns should ensure that the compression spring has sufficient preload, generally 3% - 5% of the total length of the compression spring is appropriate, and the length of the four limit columns should be consistent, and the length tolerance should be controlled at 0.02mm to ensure the uniformity of force. The main body of the machine

(3) the positioning clearance of the die should be controlled within 0.02 ~ 0.04mm, and the position of 6 die holes

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