Shell of oven is shown in Figure 1, with an external dimension of 532mm*305mm*34mm, and material is cold-rolled steel plate with a thickness of 0.6mm. Mouth of product has a full circle of inward flanging and inward sloping structure. Flanging fillet is R1.5mm, bevel angle is 60°, and bevel length is 4.0mm. There are 10 small holes of φ4mm on workpiece, including 4 on the surface, 4 on one side and 2 on the other side. Three-dimensional structure of workpiece is shown in Figure 2.

 

 

Material of inward flanging of mouth of part cannot be interrupted. After deep drawing, a pair of molds are used to flang material of mouth. Therefore, difficulty of forming part lies in inward flanging of mouth and demoulding of part after flanging.
Outer dimension of workpiece is relatively large, which is suitable for forming with a single-process mold. In addition, six processes such as blanking, deep drawing, trimming, punching, inward flanging, and beveling are required. Among them, blanking parts are larger in size, and are blanked with a shearing machine. In order to prevent formed part from wrinkling during deep drawing, a blank holder should be provided, so material for blank holder should be reserved for blanking when blanking. Blanking size is 620mm*390mm, drawing and trimming mold structure is simple and will not be introduced. Punching, inward flanging, and beveling mold structures are mainly described.

There are a total of 10 small holes on workpiece. In order to ensure roundness requirements, punching process is arranged after drawing process. In order to ensure position of 10 small holes among each other, 10 small holes are punched at the same time with a pair of molds, small holes on the side are punched with a slider. In order to ensure smooth operation of slider, guide posts and guide sleeves are installed on the slider. Unloading plate of upper die is large in size. In order to make unloading plate run smoothly, guide posts and guide sleeves are also installed. The lower die of punching die is shown in Figure 3, and structure of punching die is shown in Figure 4.

 

 

1. Lower mold plate 2, lower mold holder 3, slider spring 4, locking block 5, wedge 6, upper mold holder 7, upper template 8, slider 9, slider guide post fixing plate 10, slider guide post Guide sleeve 11, concave template 12, stripper plate guide post guide sleeve 13, punching die 14, punching punch 15, stripper plate 16, limit screw 17, stripper plate spring 18, side punching die 19, Side unloading plate 20, side punching punch 21, side unloading plate spring 22, guide post 23, guide sleeve 24, slider reset lever
Figure 4 punching die structure
Mold running process: Before starting punching, put drawn process piece with opening facing down, put it on concave mold plate 11, and process piece is positioned by its own gravity. Then start press, during downward movement of upper die, unloading plate 15 first presses process piece, upper die continues downward, and punching punch 14 punches out hole on upper surface of workpiece; upper die continues downward, wedge 5 contacts slider 8, and push slider 8 to move towards mold center, side unloading plate 19 presses side of workpiece against side of die plate 11, then side punching punch 20 punches out side hole on the side of workpiece. After side punching is completed, upper die rises, and under action of slider spring 3, side slider 8 resets. After upper mold rises to limit position, workpiece is taken out, next production cycle can be started.

In order to realize inward flanging of mouth of workpiece, a structure is designed in which inner and outer sliders are driven by inclined wedge to flanging and demoulding, and upper mold inclined wedge is designed as a double inclined plane structure, as shown in Figure 5(a). As shown, set inner and outer sliders in lower die, as shown in Figure 5(b).

 

Outer slider is in the shape of "P" and connected with tensioning block through connecting rod, as shown in Figure 6 (a), inner slider is in the shape of "L", and side pressure block is set on the step of inner slider, which is used to press side of workpiece tightly, and inner slider slides on connecting rod of outer slider, as shown in Figure 6(b) .

 

1. Lower mold base 2, connecting rod 3, tensioning block 4, inclined wedge 5, outer slider 6, outer slider locking block 7, outer slider return spring 8, spring baffle
Outer slider structure
1. Lower mold base 2, connecting rod 3, tension block 4, side pressure block 5, inner slider 6, wedge 7, outer slider 8, outer slider locking block 9, spring baffle
Structure of inner slider on outer slider
Heights of inner and outer sliders are different. Outer slider is higher and inner slider is lower. When upper mold is descending, upper mold wedge first contacts outer slider and then inner slider. Therefore, outer slider first drives tensioning block to open, and tensioning block is in a "P" shape. Upper part tightens and positions workpiece from inner surface of workpiece, then inner slider moves from side of workpiece to center of mold. Inner slider is in the shape of an "L". Steps of slider and upper part of tension block co-extrude workpiece to flang workpiece. Mold structure is shown in Figure 7.

 

1. Lower mold base 2, guide sleeve 3, guide post 4, connecting rod 5, outer slider 6, inner slider 7, wedge 8, upper mold base 9, side pressure block 10, tensioning block 11, upper mold Backing plate 12, pressure plate guide post and guide sleeve 13, process parts 14, upper mold pressure plate 15, pressure plate limit screw 16, side pressure block spring 17, pressure plate limit screw 18, upper template 19, outer slider locking block 20, Inner slider spring 21, connecting rod spring 22, spring positioning plate 23, positioning pin 24, wear-resistant sheet 25, lower template
Figure 7 Flanging die structure
Die operation process: press block 9 and tension block 10 before stamping are in reset state, and drawn process part 13 is set on tension block 10, then press is started. During downward movement of upper mold, upper mold pressing plate 14 presses process part 13 on upper surface of tension block 10; Upper mold continues to go down, upper mold wedge 7 drives outer slider 5, and moves around mold. Outer slider 5 is connected with tensioning block 10 through connecting rod 4. Tensioning block 10 is in a "P" shape. When outer slide block 5 moved around earlier, it drove upper part of tightening block 10 to tighten and position process part 13 from inner surface. Upper die continues to move downward, and when vertical surface of oblique wedge 7 was in contact with outer slide block 5, outer slide block 5 no longer moved around, and this moment, tensioning block 10 has fully tightened and positioned process part 13 from inner surface. Upper mold continues to move downward, inner slope of wedge 7 contacts inner slider 6, and inner slider 6 is squeezed toward center of mold. Inner slider 6 is in an "L" shape. When inner slider 6 moves closer to center of mold , side pressing block 9 first compresses side of process piece 13 to prevent side deformation of process piece, inner slider 6 continues to move closer to mold center, and steps of inner slider 6 turn mouth of process part 13 inwards. When patrix moves upwards, inner slide block 6, side pressing block 9 reset under effect of inner slide block spring 20 and side pressing block spring 16, outer slide block 5 resets under effect of connecting rod spring 21. Next production cycle starts after workpiece is taken out.

After flanging inwards, mouth of process part is horizontal, and it is necessary to use a beveling die to incline mouth of process part. Structure of beveling die is shown in Figure 8.

 

1, Lower mold plate 2, lower mold base 3, lower mold backing plate 4, concave mold 5, push plate 6, punch 7, upper mold backing plate 8, upper mold base 9, upper mold foot 10, upper mold limit rod 11. Upper mold pressing plate 12, upper mold spring 13, screw 14, lower mold limit rod 15, lower mold spring

Fig. 8 Structure of crimping die
Die running process: Before stamping, place process piece in die 4 with mouth facing upwards. Then start press, during downward movement of upper die, upper die pressing plate 11 first contacts process part, and upper die spring 12 is compressed, when sum of gravitational force of gravitation of gravitation of gravitation of gravity of upper die spring 12+upper die pressing plate 11+pushing plate 5 is greater than elastic force of lower die spring 15, lower die spring 15 is compressed, and upper die pressing plate 11 presses process part down. When push plate 5 was attached to backing plate 3 of lower die, upper die pressing plate 11 completely pressed process part into place, and lower die spring 15 was no longer compressed. Upper mold continues to descend, and under action of punch 6, mouth of process piece is pressed down to make it inclined. After upper die moves downward to limit position, upper die moves upwards, and under action of lower die spring 15, shaped part is pushed out.