德语
The floor in a certain vehicle model is shown in Figure 1. The external dimensions are 2040mm×1200mm×275mm, which are low in the middle and high on both sides. The material is DC04 and the blank size is 2510mm×1560mm×0.9mm. During the CAE analysis, the part has defects of falling down the middle of the blank, and the molded parts have wrinkles when the mold is closed.
Process shape and defect description
The pressing surface of the process shape is slightly raised, as shown in Figure 2. The purpose is to store some materials during the pressing process to reduce the depth of drawing and reduce the inflow of material during the deep drawing process. In CAE analysis, the blank is large in size and low in the middle of the mould, and the blank cannot be supported. Under the action of gravity, the blank collapses. As shown in Figure 3, it causes wrinkles in the sheet during the edge pressing process, and residual imprints on the forming parts, resulting in mass defects.
Solutions for the collapse of blanks in closed state of floating mound
The general solution to down-sink defects: ① The pressing surface is processed into a plane, and the pressing state will be improved, but the depth of the drawing will increase, the material inflow will also increase, the wear of the mold parts will intensify, and the material utilization rate will be reduced; ② Change to double-moving drawing, the uplift of the pressing surface will become a downward trend, no longer affected by the down-sink caused by gravity, but the part cannot meet this production method due to the limitations of the press; ③ Add a blank support device (floating bolt), add support material to the mould to eliminate the down-sinking bolt, and realize pre-bending of the blank during the edge pressing process, but the mold structure is more complex than usual. After multiple verifications of the range and lifting height of the lifting material, the edge pressing process after adding the lifting material eliminates the wrinkle phenomenon and the parts have no risk of wrinkling, as shown in Figure 4.
Add floating mould to support material
According to the working principle of deep drawing forming, the floating mould is only used for blank support during the pressing process and does not participate in the forming of the parts. Their lifting and downward movements should be synchronized with the pressing ring and cannot be used for elastic driving. The floating mould should be in place at the same time as the pressing ring is raised to ensure that the blank is effectively supported when the blank is placed. When the pressing ring is closed and downward, the floating mould should go downward simultaneously with the pressing ring, but its stroke should be less than the pressing ring stroke. When the upper die goes down to the position of the floating mould and the deep drawing bolt, the floating mould stops moving and the upper die continues to move downward. At this time, the floating mould will participate in the forming of the parts together with the deep drawing bolt until the deep drawing process is completed.
1. Floating punch 2. Top rod pad 3. Spring guide components 4. Rectangular spring 5. Limit screw 6. Copper alloy self-lubricating guide plate 7. Edge pressing ring 8. Upper mold seat 9. Pier dead pad 10. Drawing punch 11. Lower mold seat
Figure 5 shows the state of the pull-out molded edge ring with a floating mould, with the compression ring stroke of 220mm. Under the action of the press hoist, the floating mould is consistent with the height of the compression ring after being lifted, which can effectively support the blank and avoid falling down the blank. Figure 6 shows the structure of the floating mould and the mold. The floating mould is installed inside the drawing mould. It is driven by the press's top rod. The bottom surface is equipped with an adjustment pad. The guide plate is guided around it, and an auxiliary elastic return position is set to drive the floating mould to go down synchronously with the pressing ring. Another function is to prevent the floating mould from falling out when the lower die is flipped. When the pressing ring goes down 145mm, the floating mould goes down synchronously to the same position as the drawing mould. The adjustment pad at the bottom of the floating mould comes into contact with the lower die seat. The floating mould stops moving and then breaks away from the pushing rod. The pressing ring continues to move downward for 75mm, and the drawing ends.
After the deflection forming is completed, the slider drives the upper die upwards, and the top rod pushes the pressing ring upwards. At this time, the top rod does not come into contact with the floating bolt, and the floating bolt is still in a stationary state. When the push rod continues to be pushed upwards for 75mm, the top rod comes into contact with the floating bolt. At this time, the drawn-out part has been removed from the drawing bolt and goes upwards for 75mm with the pressing ring upwards for 75mm. The floating bolt will not cause damage to the parts. The floating bolt continues to go upwards with the pressing ring under the action of the pushing rod and continues to go upwards for 145mm in synchronization with the pressing ring, and the rectangular spring 4 compresses 145mm synchronously, the top rod stops being pushed up, and the mold returns to the floating bolt state shown in Figure 5. During the final mold debugging, the floating mould is reliable in operation, and there is no wrinkle in the pressing state, which is consistent with the CAE analysis state.
Although floating moulds can play a role in supporting materials in the mold, their essence is still part of the drawing mould, and their assembly accuracy and processing accuracy still need to be guaranteed. The drawing punch and the floating punch are guided by copper alloy self-lubricating guide plates. After assembly, the convex model surface is processed together. The gap between the floating punch and the drawing punch should not be too large, and should be controlled within 0.5mm. The top rod pad is long (see Figure 7), which is both a top rod pad and a mounting plate for a rectangular spring assembly. It needs to be assembled from the bottom surface of the lower mold to the bottom surface of the floating mould (including a rectangular spring assembly fixed thereon), so as to deliver reliable movement transmission for the action of the floating mould; the setting of the rectangular spring can prevent the floating mould from breaking out when the mold is flipped, and can provide elastic return when the floating mould cannot move downward by its own gravity, making the mechanism more reliable.
The floating mould can effectively solve the problem of collapse of the depth drawing die blank. The structure is more complicated than the conventional deep drawing die. The setting area, lifting height, guiding accuracy, positioning accuracy, processing technology, assembly technology, reliability, etc. of the floating mould need to be demonstrated and analyzed. The application of this mechanism provides a reference for solving the problem of deep-drawing mold blank collapse, and meets the requirements of mold production and parts forming quality.
▍Original author: Zhang Xiuli, Li Xuekun, Yu Xuming
▍Author’s unit: Shandong Weifang Futian Module Co., Ltd.
Note: All pictures in the article are reprinted online, and will be deleted if infringed!
