Improvement of injection mold for the hottest conn

2022-09-23
  • Detail

Improvement of injection mold for connecting parts

1. Problem raising

a connecting part is a plastic part, and the monthly demand is about 150000 pieces. This product adopts injection molding. Because more sliders are needed in molding and the development time is short, some problems (such as the suspension structure of the shoulder sample) need to be improved after its development. At the beginning of its mass production, the product mainly had problems such as rough edges on the appearance of the product, frequent fracture of the inclined pin cavity of the die, etc. in order to solve some of the above problems, we made corresponding improvements to it

2. Mold improvement

2.1 product appearance burr improvement

the structural characteristics of the product determine that the place where the plastic part may produce burr is where its slider is formed

(1) product head burr

due to the requirements of the product function, its head is not allowed to have burrs (this is the appearance), and the originally designed slider uses only a diagonal pin designed on the cavity to guide and position the slider. In this case, the "tightness" between the two will be poor when the cavity core is closed, resulting in burrs. The cavity before improvement is shown in Figure 1

Figure 1: core and cavity slider before improvement

a -- core slider B -- cavity slider C -- combination of core and cavity slider

it can be seen from Figure 2 that during the molding of the improved product, the movement of the slider is guided by the inclined guide pin on the core (the inclined pin can also play a certain positioning role), and the positioning is completed by the "opposite" between the inclined plane on the cavity slider and the inclined plane of the core, In this way, the improved mold is equivalent to having two positioning mechanisms, and its area of positioning is much larger than that before the improvement. The product appearance diagram before and after the improvement shown in Figure 3 shows that the above improvement is feasible

Figure 2 improved core and cavity slider

a-- core slider b-- cavity slider c-- combination of core and cavity slider

Figure 3 product appearance before and after improvement

a-- product drawing before and after improvement b-- product drawing after improvement

the above improvement effect has been well confirmed in actual work, which provides a good reference for us when designing similar products

(2) burr at product overflow

it can be seen from Figure 3 that there are four square overflow holes on both sides of the product, and they are also formed with sliders

there are 16 surfaces in contact between the overflow cavity of the molding product before the improvement and its matching cavity, but only 4 surfaces are in contact after the improvement. As shown in Figure 4, the more surfaces between the cavities are in contact with each other, the more difficult it is to repair the cavity during assembly, and the more likely it is to cause burrs in the product. The improved cavity is made with r0.5mm arc around it, so the improved cavity is not only easy to assemble, but also there is no burr at this place during production (because making the arc around the overflow of the product has no impact on the function of the product, the manufacturing engineering unit has modified the product blueprint)

Figure 4 slide block diagram before and after improvement

a-- shape of slide block before improvement b-- shape of slide block after improvement c-- shape of cavity through which slide block after improvement passes during forming figure

2.2 improvement of oblique pin cavity fracture

due to the limitation of product structure, the part on the original sprue should now be excavated, and then a position should be reserved for sliding block core pulling of forming product overflow. Its cavity is shown in Figure 5

Figure 5 it is reported that the structure of the former cavity and core runner is improved

a-- the former cavity runner is improved b-- the former core runner is improved

in Figure 5, the round hole is used to pass through the draw joint, and the molten plastic flows to the mainstream through the draw joint during molding, which has become the wind vane of industry development. The former cavity will "overflow" to the hollowed out position on the core runner during molding, In this way, the sliding block on the core as shown in Figure 4B cannot be completely returned, so the inclined pin on the cavity cannot be inserted into the matching inclined pin hole on the core, which eventually leads to the fracture of the inclined pin on the cavity

it can be seen from the above that the cavity fracture defect can be improved as long as the overflow of molten plastic during molding is avoided. Therefore, the improvement is made as shown in Figure 6

Figure 6 mold improvement

a-- improved cavity runner b-- improved feed joint c-- cavity 2cavity

the contact between the feed joint hole of the runner on the cavity and the core runner becomes smaller (the feed joint used is much shorter than that before the improvement), so the improvement enlarges the distance between the cavity feed joint and the water level in the trough used for core pulling slider on the core, which is automatically controlled by 1 water level controller, And completely avoid the overflow of plastic during molding, so as to finally improve the defect of frequent fracture of inclined pin cavity

3. Conclusion

the connector has been mass-produced, and the improvement process of its mold is not very complex, among which the most critical is the improvement of product appearance burr and the fracture of inclined pin cavity. (end)

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