Epoxy resin molds, also known as resin molds, have a short manufacturing cycle, low cost, and are particularly suitable for industrial fields with complex shapes and rapid product replacement; therefore, they have been widely used in advanced foreign countries, especially in the automobile manufacturing industry. , Toy manufacturing, home appliance manufacturing, hardware industry, plastic products and other industrial systems are more widely used. According to different structures and uses, epoxy resin molds are made of epoxy resins with various properties, curing agents, toughening agents and fillers (iron powder, aluminum powder, silicon powder, barite powder, etc.), etc. Made of glass fiber cloth and carbon fiber cloth as reinforcement materials.
According to different uses and technical requirements, epoxy resin molds can design different epoxy mold resin formulation components. From the actual application statistics of domestic and foreign epoxy resin molds, epoxy resins are suitable for the production of the following types of molds. The cold-pressing molds include: bending molds, drawing molds, falling hammer molds, casting molds, etc .; Molds include: plastic injection molds, injection molds, blow molds, suction molds, foam forming molds, leather and plastic product forming molds, etc. The manufacturing characteristics of epoxy resin molds are easy to manufacture, fast, and low cost; for example, some metal molds with complex shapes and difficult to form are made of epoxy resin, which can be formed at one time by using the casting method or the low pressure forming method, without the need for large precision Cutting machine tools can also eliminate the need for advanced fitters. Some metal molds have a manufacturing cycle of several months to half a year. The use of epoxy resin molds generally takes only 3 to 5 days to complete. The cost is only about 15 to 20% of the steel molds, and the resin molds have a long service life and wear. It can be patched soon and continue to be used. Therefore, the manufacture of epoxy resin molds is a new technology, new materials and new processes that break the traditional machining process. Epoxy resin molds are manufactured in specialized research centers set up by large factories abroad, but they are only developed in the defense industry in China. General factory enterprises lack manufacturing technology and formulas in this area. The speed of application, popularization and development of molds is very slow. In the future, with the development of new materials and technologies, the popularization of epoxy resin application technology, the comprehensive performance and manufacturing technology of epoxy resin molds have been widely introduced and recognized, the performance of epoxy resin composites has been improved, and the production process of resin molds And the simplification of the application process, epoxy resin molds will inevitably develop by leaps and become a new high-efficiency, low-cost advanced mold.
Second, the type of epoxy resin mold
1. Epoxy resin cold-pressed mold
(1) Bending die, forming die, drawing die, notching die, etc.
The epoxy resin composite material department is mainly used to manufacture concave and convex molds, which can be formed by casting or low-pressure molding. It can stamp or draw aluminum plates of 0.8 mm steel plates and 2 mm or less, and have a life of more than 10,000 times without wear. For large drawing molds, such as automobile cab top cover parts, the use of epoxy resin to make molds shows greater advantages, without the need for large cutting machine tools. The cutting die is used to manufacture large parts with complicated structure, and a steel band is embedded in the edge of the concave-convex die. The bending mold made of epoxy resin, the stamping parts include the fan blades of the ceiling fan, etc. The size of the fan blade surface is very high. Due to the relationship between the air volume and the use effect, the epoxy resin mold is fixed on a 100-ton punch press The molding and stamping times have reached more than 300,000 times, and the resin mold is still in use.
(2) Drop hammer mold
Using epoxy resin drop hammer die, you can stamp 2.5 mm thick aluminum plate and 1.5 mm thick stainless steel plate. The mold made of resin has good coordination performance, simple process, short manufacturing cycle, 3/4 time shorter than aluminum-zinc mold, and can also save a lot of non-ferrous metals and reduce costs.
Regarding the molds such as models, core boxes, mold plates, etc., the advantages of using epoxy resin to make molds:
①Resin mold manufacturing cycle is short, such as aluminum mold manufacturing cycle is about one month, and resin mold manufacturing takes only 3 to 5 days;
②The service life of the resin mold is long. If the aluminum mold is used 2,000 times, it needs to be overhauled, and the resin mold can be used 20,000 times;
③Resin mold repair is simple and convenient;
④The resin mold is light in weight and has high labor productivity.
Therefore, epoxy resin is widely used for casting molds at home and abroad. Structure: There are resin-coated compound molds and all resin integral molds.
In addition, epoxy resin can also be used to make hammering dies, explosion forming dies, hydroforming dies, tensile tires, transfer dies, inspection dies, etc. Most of the above resin dies are used to make airplanes, cars or rockets Another part. The manufacturing speed of epoxy resin molds is fast, the cost is low, and the coordination performance is good, which can solve the technical difficulties in the manufacture of general metal molds.
2. Epoxy hot pressing type mold
(1) Injection mold
The mold used for the injection wax type is generally made of metal. The gypsum mold is also used for small batches and low requirements. The wax type is first injected with a wax injection mold, and then a shell mold is made according to the wax type, and the metal is poured after melting the wax. The resin injection wax mold has high strength, convenient molding, high finish, good wear resistance, and slightly lower thermal conductivity. When processing the shape of the sculpture, the economic benefit is higher.
(2) Plastic injection mold
With the rapid development and wide application of engineering plastics, the manufacture of plastic molds has become even more important. Epoxy resin injection mold is a new technology that is making great efforts at home and abroad. According to the information, epoxy resin injection molds are used as a simple and fast mold abroad because of its fast molding and accurate shape, but the disadvantage is poor heat resistance. Therefore, cooling water pipes should be considered when designing resin molds to increase the number of injections. . Several units in China are also developing such resin molds, and have achieved good applications. The number of injections has reached more than 10,000 times, and the epoxy resin mold surface has not changed. The optimization of the resin mold formulation design and the improvement of the mold structure enable the resin mold to have a higher level of thermal strength and thermal conductivity. Therefore, if the product profile is a sculptural profile that cannot be processed by machining, the superiority of the epoxy resin mold is more obvious.
(3) Blow mold and blister mold
This type of mold requires good thermal strength and thermal conductivity of the cured epoxy resin formulation. Its biggest advantage is that it is easy to form. These resin molds are all molds in development and application.
3. Materials and properties of epoxy resin molds
The base resin for manufacturing the resin mold includes phenolic resin, unsaturated polyester resin, epoxy resin and the like. Among these matrix resins, epoxy resin has the best mechanical and physical properties and good manufacturability. Therefore, epoxy resin is now used to make molds. For example, the highest strength composite materials are made of epoxy resin, boron fiber, and carbon fiber.
Matrix resin: Commonly used epoxy resins include bisphenol A epoxy resin, such as; YD-128, E-51, E-44, etc .; novolac epoxy resins F-44 and F-45; amino multifunctional epoxy Resins AFG-80, AFG-90; alicyclic epoxy resin R-122, etc. According to the mechanical strength requirements, heat resistance requirements and precision requirements of different resin molds, select the matrix resin type, and then design the formula.
Curing agent: amine curing agent: fatty amine, polycondensation amine, aromatic amine, modified aromatic amine, etc .;
Imidazole curing agents: 2-methylimidazole, modified imidazole, 2-ethyl-4-methylimidazole, etc .;
Anhydride curing agents: methyltetrahydrophthalic anhydride, modified methyltetrahydrophthalic anhydride, chlorobridge anhydride, pyromellitic dianhydride, etc.
Toughening agent: LDY-050 active toughening agent, LDY-052 reactive toughening agent, LDY-055 sea island structure toughening agent, high polymerization degree polysulfide rubber, carboxyl-terminated nitrile rubber, etc.
Fiber reinforced materials: glass fiber (cloth), carbon fiber (cloth), boron fiber (cloth), etc.
Filler: silicon powder, iron powder, aluminum powder, copper powder, alumina powder, barite powder, etc.
The epoxy resin mold composite material is composed of a matrix resin, a curing agent, a toughening agent, a filler, and a fiber-reinforced material, and achieves a high-performance mold resin by curing reaction. According to the different structure and technical requirements of different molds, different formulas are designed, the formulas are different, and the forming process and curing process are also different.
Typical mechanical and physical properties of epoxy resin mold casting body:
Compressive strength: 120 ~ 150MPa
Impact strength: 25 ~ 38KJ / m2
Flexural strength: 110 ~ 160MPa
Brinell hardness: 20 ~ 30MPa
0.2 ~ 0.5% shrinkage during curing
Fourth, the manufacturing method of epoxy resin mold
1. Casting process manufacturing
Weigh and mix according to the proportion of epoxy resin formula, then pour into the model mold, according to the requirements of the recipe process, use room temperature or high temperature curing molding. Vibration casting process can also be used.
2. Lamination process manufacturing
Glass fiber or carbon fiber reinforced epoxy resin molds, which do not require pressure during curing, are laminated with fiber reinforced materials in the model and coated with epoxy resin mixture, which is called the contact lamination process. If curing is carried out under pressure, the content of glass fiber can be increased, which is called pressure lamination process.
3. The mixture of short glass fiber reinforcement and resin can be formed in a simple metal mold.
In short, different molds, according to the structure of the mold, the type of mold, the technical requirements of the mold to design different epoxy resin formulations and manufacturing processes, can make a good epoxy resin mold.