How to design the molding process and die of the lead head? What are the processes and steps? Let me explain it to you!
The lead head shown in figure 1 is a part of a product, and the material is 6 mm? 25mm soft copper bus bar. The quality requirement of the product is: when the two ends of the bus bar are twisted by 90 degrees, a Z-bend is superimposed on the torsional deformation zone. Z-bend is required to ensure the size of 1 1 mm, and there is no special requirement for the torsional deformation zone of the part, so it can be naturally formed by die. Both ends must be straight within the size range of 30mm, and defects such as indentation are not allowed in each part. Due to the large batch of this part, it is required to use molds for molding.
Technical analysis of 1
The material of the part is soft copper bus bar, which has good plasticity and small bending rebound, which is beneficial to the forming and size guarantee of the part, but it is easy to appear indentation when bending, so it must be fully considered in the design and manufacture of the die. For torsion bending parts, it is generally required that the length of torsion bending deformation parts is 2.5b ~ 5b (6 is the width of copper bar) and the length of torsion bending parts is 70 mm, which meets the requirements of torsion bending process. Through the above analysis, the manufacturability of the part is good, and the key is to determine the process scheme and design the die structure.
2 Determination of process scheme
This part is a special part formed by torsion bending, and the deformed part overlaps with torsion bending and Z bending. If one-time molding is considered, it is obvious that the mold design is very difficult, and there is no similar example to learn from before. In order to reduce the risk and the difficulty of die design, it is decided to form two elbows respectively. Separate bends, which bend is the first key. It is difficult to determine the blank size of the intermediate process by bending Z first. If the size of the intermediate process is not properly determined, there will be problems in the dies of both processes, and bending Z first increases the difficulty of the torsion bending process. If the torsion bending is carried out first and then the Z bending is carried out, the size of the intermediate process is easy to determine, and the die design of the torsion Z bending process is relatively easy. Through the above analysis, the forming scheme of the part is determined as follows: firstly, after blanking, it is twisted and bent, and then it is Z-shaped. This scheme needs to design a set of torsion bending die and a set of Z bending die. In addition, the blanking length is difficult to determine, so the blanking length in the first trial production is appropriately lengthened, and the accurate blanking size is determined according to the measured size.
3 process calculation
3. 1 determination of torsion and bending resilience
Soft copper busbar is well formed and has small springback, so the springback effect can be ignored in bending with low precision requirements. Torsional bending is a special kind of bending, and there is no special data. In order to improve the accuracy of parts and prepare for the next process, this example uses 90-degree single-angle free bending to retrieve the spring angle in the design, and looks up the table to retrieve the spring angle as 2 degrees.
3.2 Estimation of Torsional Bending Force
For the calculation of bending force, there is no special formula for torsional bending deformation. In this case, it is estimated according to the empirical formula of free bending of V-shaped parts. P from =0.6kb？ 2? b/(r+？ ), where k= 1.3, the width b of the bending piece is calculated by the diagonal of the deformation zone, and b= (252+ 702) 1/2=74.4 mm,? =6 mm，？ B=200 MPa, and bending fillet r=6 mm according to the minimum material thickness, then P = 34,865,438+09N. According to the bending force and the equipment in the production site, JB 23-80 open pendulum press is selected.
4 Mold structure and working process
4. 1 Bending die
Fig. 2 shows the structure of the torsional bending die, which adopts a sliding guide post die frame, and the die is connected and fixed with the press through the die handle 7. Position the blank in the mold by positioning plate 14 and positioning pin 8. The position of the positioning plate 14 can be adjusted within a certain range, and the supporting pin 16 supports the blank. When bending, the upper die goes down, and the punch 1 1 presses the two sides of the copper bus bar respectively, so that the two ends of the copper bus bar are twisted in opposite directions, thus realizing the twisting of the copper bus bar. The locating pin 8 plays a role in locating and limiting the movement of the copper bus during the pressing process. The punch continues to descend, and the bus bar gradually adheres to the side steps of the punch and the die. When the slider reaches the bottom dead center, the mold closes and the torsion of the part ends. Three points should be paid attention to in the design of this die: (1) The springback angle should be considered in the design of punch and die. According to the above calculation, the rebound angle in this example is designed as 2 degrees; (2) All contact surfaces between the convex and concave die of the die and the bus bar must be smooth; (3) Indentations are easy to appear at the parts where the parts begin to twist and bend, so the sharp edges on both sides of the punch must be inverted into circular arcs.
4.2 Z bending die
Fig. 3 shows the structure of the Z-shaped bending die. The die is installed on the JB23-80 press and connected with the press through the die handle 8. When installing the mold, adjust the connecting rod and adjust the closing height of the press to a position 30 mm greater than the closing height of the mold. Firstly, the upper die is fixed on the press. When adjusting the position of the lower die, slowly adjust the connecting rod of the press downward, so that the side of the inclined wedge 6 contacts with the sliding wedge seat 9, and the sliding wedge seat is aligned with the side of the inclined wedge. At the same time, the blanking plate 12 completely presses the upper surface of the female die 1 1, and the lower die is fastened after adjustment. Put one end of the twisted semi-finished blank into the groove of the female die 1 1, and the other end into the groove of the sliding wedge 5, so that the end face of the part is flush with the turbulent surface of the sliding wedge. When bending, the upper die goes down, and the blanking plate 12 first contacts the part. Under the action of the spring 13, the part is pressed into the groove of the female die 1 1. When the upper die continues to descend, the inclined wedge 6 contacts with the inclined surface of the sliding wedge 5, pushing the sliding wedge to move and bending the parts under the action of the sliding wedge. The height of Z-shaped bending can be adjusted by adjusting the closing height of the press. Three points should be paid attention to when designing and manufacturing the die: the selection of (1) wedge angle, the calculation of the horizontal moving distance s and the stroke S 1 of the sliding wedge. In this case, the wedge angle is 40, because the stroke and stress on the sliding wedge are not large. Select, and calculate S= 23.5 mm and S/S 1=0 according to the part size. 839 1 is derived from the formula S 1=28 mm; (2) All surfaces in contact with the copper bus bar during bending must be smooth and sharp edges must be smooth, especially the sharp edges on both sides of the female die groove and the sliding wedge groove must be smooth; (3) Material selection of key parts of the mould. In this example, the materials of the inclined wedge, the sliding wedge, the sliding wedge seat and the concave die are all Cr 12MoV, and the heat treatment hardness reaches 58 ~ 62 HRC.
5 conclusion
The two sets of lead head forming dies introduced in this paper are simple in structure, easy to manufacture, easy to install, debug and use. It is verified by mass production that the dimensions of the parts fully meet the requirements of the drawings, and the technological scheme and die design of the lead head parts are successful, which can also be used for reference for the forming of similar parts.
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