Forming technology and progressive die design of t

2022-08-22
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High pressure sealing washer forming process and progressive die design

Abstract: in view of the problems existing in the original machining process of high-pressure copper washer, this paper puts forward the scheme of using mold to process and produce, analyzes the forming process characteristics of the washer, and introduces the part layout design and mold structure

key words: tooth extrusion molding; Layout scheme; Progressive die

1 introduction

high pressure sealing washers are shown in Figure 1. They are made of red copper (T4). Their force measuring part adopts a dynamic pendulum dynamometer

Figure 1 high pressure sealing washer

this part was originally machined on an ordinary lathe. This processing method has the following shortcomings:

(1) labor and time-consuming. Turning a washer requires cutting tool grinding → clamping bar → machining inner and outer diameters → cutting → changing fixture clamping → turning water line → turning around clamping → turning water line. Each takes about 15min

(2) waste materials. The outer diameter of the washer is φ 32mm, required diameter is φ For the processing of 35mm blank, the cutting position is 4mm and the clamping position of the lathe head is lomm, but the actual thickness of the washer is only 2m. The physical and mechanical properties of metal wire material are m

(3) poor quality. When one side of the tooth is machined and turned, the washer will be deformed due to stress, which makes it difficult to ensure the parallelism of the two tooth surfaces, and it is also difficult to avoid cutting burrs

due to the large demand for this part, in order to improve production efficiency, reduce costs and improve product quality, it is decided to use molds to produce gaskets

2 analysis of gasket extrusion process

cold extrusion is a processing method that makes the metal produce plastic deformation in the mold cavity at room temperature, so as to obtain the required part shape and size. Limited by the forming characteristics of parts and other conditions, as a common process in cold extrusion, it is mostly used in single process die. Due to the particularity of the part in Figure 1, the extrusion progressive die is tried to produce the part

as shown in Figure 1, the requirements for the tip degree of two tooth surfaces of parts are high. For example, the arc at the sharp corner of the tooth shape is m. The parallelism of the upper and lower planes is less than 0.05mm, which also points out the direction for the development of plastic granulator technology in China. It is not only the key of technical requirements, but also the difficulty of extrusion forming

there are two height dimensions of this part, and the large one is only 2mm, which belongs to a kind of plate-shaped extrusion. After analysis, there are two schemes to select the blank thickness for this extrusion

scheme 1: blank thickness is selected by referring to the height of inner and outer circles. At this time, the forming characteristics of the parts are mainly manifested in the severe reverse and forward extrusion of the upper and lower tooth profiles

scheme 2: the blank thickness is selected according to the tooth profile thickness. At this time, the forming center of gravity of the washer turns to radial (centripetal and centrifugal) extrusion of the inner and outer circle height

because the structure of the part limits the metal flow of the tooth shaped part, it is decided to adopt the second scheme from the perspective of meeting the forming requirements of key dimensions. Combined with the material specification, the blank thickness is taken as 2 ± 0.1mm

3 layout scheme

9 station progressive die layout is shown in Figure 2. Station 1 punches the positive hole and central pre hole, and cuts the gap on both sides; Station 2: guide and punch the circular incision; Station 4 pre extruded tooth profile; Station 5 fine extruding tooth profile; Station 7 punching inner hole; Station 9 sets the profile. The rest of stations 3, 6 and 8 are empty stations. The setting of empty positions not only ensures the strength of the die, but also provides space for unloading

Fig. 2 layout

because extrusion and stretching belong to three-dimensional deformation processes, there are some similarities between them, so the extrusion process design draws on the layout method of continuous stretching with materials. In order to overcome the influence of radial deformation of extruded parts on step length. The methods of punching notches and circular notches are also adopted. It should be noted that the yield width of the circular notch is determined according to the extrusion deformation, which is larger than the notch width of the general stretched strip (the notch value is widened due to the shrinkage of the material to the center due to the stretching of the part, and it is just the opposite in the radial extrusion). It is taken as 6mm in the design. The initial value of the outer diameter of the parts formed by the central pre hole punched in station 1 and the annular notch in station 2 has a margin of 1mm

the material flows due to extrusion, and the compressed air left at the sealing places such as the sharp corners in the die will make it difficult for the metal to fill up. Because the tooth spacing of this part is only 1.2mm, it is impossible to exhaust by using the gap between the die blocks, so the tooth shape secondary back pressure forming method is adopted. As shown in Figure 3, the sharp angle of the pre extrusion tooth shape is 60 °, and the height is 0.8mm, which overcomes the influence of the air obstruction in the die and the difficulty of filling the material at the sharp angle in the die on the extrusion forming, and achieves the expected effect

Figure 3 pre extrusion and fine extrusion tooth profile

a-pre extrusion tooth profile b-fine extrusion tooth profile

4 mold structure analysis

the progressive die structure of high pressure sealing washer is shown in Figure 4. The whole set of dies adopts a four guide pillar rolling guide die base, and at the same time, 4 pieces are used between the male die fixing plate, the discharge plate and the female die fixing plate φ 14mm guide post is used for guiding to ensure the relative position accuracy between punch, female die and discharge plate. The unloading plate is unloaded by high-quality cylindrical polyurethane rubber

Figure 4 progressive die for extruding teeth of washer

1 Upper die base 2 upper fixing plate 3 Punching pre hole punch 4 Notch punch 5 Upper backing plate 6 discharge plate backing plate 7 pre extruded tooth inserts

8 Precision extruded gear insert 9 Punch for inner hole 10 Polyurethane 11 Blanking punch 12 Lower die base 13 lower fixing plate 14 Insert 15 lifting pin 16 Pre extruded gear insert 17 fine extruded gear insert 18 The lower backing plate 19 punching inner hole concave die 20 blanking concave die 21 unloading plate

the belt is guided by the feeding mechanism through the guide pin, elastic pressing and side pressing device, and the materials are lifted by the lifting nails on both sides to ensure the smooth feeding of strips. For the convenience of manufacturing and maintenance, the female die adopts the form of inlaying. In view of the large deformation pressure of cold extrusion, die steel for gear extrusion should have high hardenability, high hardness and wear resistance. And the heat treatment deformation is small, and the plasticity and toughness at high temperature are good. After comparison, the die material is finally Cr12Mo1V1 die steel

the working process of the die is as follows: the upper die goes down, the unloading plate fits the strip with the working surface of the lower die through the lifting pin, and the punch and concave die pre extrude, fine extrude and blanking the blank. When the upper die goes up, the lifting pin will lift the strip, so that the automatic feeding mechanism can feed the strip. It should be noted that the height dimension and tolerance between the constituent inserts should be strictly controlled, which is the key factor to ensure the production of qualified parts

5 conclusion

after trial production, the part size meets the design requirements. In terms of performance, the test water pressure of 30MPa and test air pressure of 25MPa meet the technical indicators, formerly known as "packaging tax". Compared with the traditional process, the new processing method can save 50% of materials and improve work efficiency by 10 times, which better meets the production needs. (end)

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