Structural design of injection mold in the develop

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Structural design of injection mold in refrigerator product development

a good plastic product must first have a good structural design. A reasonable and optimized structural design can not only simplify the injection mold of plastic products and reduce the mold cost, but also simplify its molding process and improve the molding qualification rate of products

today, with the highly developed manufacturing industry, plastic products have entered thousands of households relying on its fashionable shape, beautiful appearance and good strength, ranging from Shenzhou VI spacecraft, various cars, ships, household appliances, to a children's toy, nut, electronic watch, plastic stool, mineral water bottle, etc. plastic products have brought a lot of convenience and beauty to our life. Exquisite and flawless plastic products can really decorate our bedroom and enrich our life. Plastic products with defects will not only affect its appearance, but also affect its function. An exquisite plastic product is often inseparable from an optimized injection mold, a reasonable molding process and raw materials with excellent performance. In addition, there is a prerequisite, that is, a constantly optimized structural design

Figure 1 design of refrigerator shelf cover

wall thickness

reasonable design of wall thickness is crucial for a plastic product. The transportation cost is high and inconvenient. The wall thickness of the product is generally within the range of 1 ~ 6mm, while the most commonly used wall thickness value is 2 ~ 3mm. Too thin wall thickness cannot guarantee the strength of the product. Too thick wall thickness will consume a lot of materials and increase the cooling and hardening time after the product is formed. In addition, it is easy to produce bubbles, dents, sandwiches and uneven shrinkage, resulting in stress concentration. The design of wall thickness generally helps the expansion and strength of aluminum group can body materials. The following principles should be followed: the design of products should try to ensure that the wall thickness is uniform and avoid sudden thickening or thinning; Where the wall thickness is too thick, the excess wall thickness shall be removed by adding process holes to eliminate the internal stress

design of demoulding slope

in order to take the plastic products out of the mold cavity smoothly, sufficient demoulding slope must be designed on the inner and outer walls of the products. The size of the demoulding slope depends on the nature of the plastic, the shrinkage rate, the wall thickness and shape of the product. The following situations are generally considered in the design: if the shape of the product is complex, the depth is deep, and it is not easy to demould, a larger demoulding slope should be selected; If the shrinkage of plastic is large, a larger slope value should be selected; For products with high dimensional accuracy requirements, a small demoulding slope should be selected; For higher and larger products, smaller demoulding slope should also be selected

design of stiffeners

generally, for products with large size and small wall thickness, we can improve the strength and rigidity of products by setting stiffeners at appropriate positions of products, but there are also many attentions to the setting of stiffeners, such as: stiffeners should not be designed too thick, otherwise it is easy to produce dents on their corresponding walls; The stiffener should have sufficient slope, and the bottom should be in arc transition; The layout of stiffeners should be reasonable and uniform, and the deformation and cracking caused by uneven shrinkage should be reduced; For large-area products, it is better to design more and shorter stiffeners

hole design

there are usually two kinds of holes on plastic products. One is the assembly hole for various purposes of the product itself, and the other is the process hole set to improve the performance of the product. No matter which hole is reasonably designed, it will have a good quality and facilitate the molding of the product. The specific application is mainly divided into three cases: when the products need to have side holes, it often makes the mold add side core pulling mechanism, which complicates the manufacturing of the mold. Therefore, we should try to improve the design, simplify the mold structure, and ensure the smooth demoulding; The position of the hole on the product should be set at the position that is not easy to weaken the strength of the product as far as possible, and it can also replace wood to make furniture such as jade aluminum flooring; For brittle products, a proper distance should be reserved between adjacent holes and between holes and the edge of the product to prevent cracking when connecting and fixing the products

design of fillet

fillet in the design of plastic products can not only make the appearance of plastic products more smooth and beautiful, but also avoid stress concentration, improve product strength, improve material flow and facilitate demoulding. Circular arc transition should be adopted on all sides and internal connections of the product. The size of the fillet design in the product can follow the following formula: 0.25

Design of inserts

in order to meet the requirements of connection and installation, products often use various inserts. Most inserts are made of metal. Due to the large difference between the size change of metal inserts and the thermal shrinkage value of plastic when they are cooled, large internal stress is generated around the inserts, which is easy to cause cracking of products. In order to prevent this phenomenon, attention should be paid to the design of inserts: the linear expansion coefficient of inserts and products should be as close as possible; All sharp corners of the insert shall be rounded to reduce internal stress; The inserts should be round or symmetrical as far as possible to ensure uniform shrinkage

Design of supporting surface

plastic products are easy to deform. Therefore, when the supporting surface of plastic products is a large plane, the deformation of the large plane often causes the unstable supporting surface. Therefore, the supporting surface of plastic products is generally composed of several small planes. It should be noted that when the product needs to be supported by one surface, the whole surface should not be used as the supporting surface in the design, but should be replaced by the shape of convex edge or support foot; When the product uses the lug as the support surface for fastening, in order to make the lug have enough strength to bear the fastening force, the support surface designed with stiffeners can be used

thread design

threads on plastic products can be made directly during molding. Due to the shortcomings of plastic threads such as poor strength, poor accuracy and easy to produce internal stress, the following points should be paid attention to in the design: plastic threads should be selected with larger thread size; The beginning and end of the plastic thread should not start and end suddenly, but should have a transition part; Considering the shrinkage of the pitch of plastic thread, the fitting length of plastic thread and metal thread should not be too long

to sum up, a good structural design, together with a well-developed mold for making deformable sticking mold and a reasonable molding process, is equal to a perfect plastic product. When we are designing the structure of plastic products, we are required to have the basic knowledge of plastic mold and plastic molding at the same time. After mastering these, we can design plastic products that satisfy both consumers and ourselves. (end)

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