PC tem excelente desempenho, alta transparência, boa resistência ao impacto, resistência à fluência, ampla faixa de temperatura. As características do processo de PC são: a sensibilidade da viscosidade do fundido à taxa de cisalhamento é pequena, mas tem grande sensibilidade à temperatura, nenhum ponto de fusão óbvio, high viscosity of melt, easy hydrolysis of resin at high temperature and easy cracking of products. In view of these characteristics, we should pay special attention to the different treatment: to increase the fluidity of the melt, we should not increase the injection pressure but also adopt the method of increasing the injection temperature. The runner and gate of the mould are required to be short and thick to reduce the pressure loss of the fluid and to have a higher injection pressure. Before forming and processing, the resin should be dried sufficiently to keep its moisture content below 0.02%. Além disso, heat preservation measures should be taken to prevent moisture absorption during the process. Not only the reasonable product design is needed, but also the molding process should be correctly mastered, such as increasing the mold temperature and post-treatment of the products, etc. can reduce or eliminate the internal stress. Adjust the process parameters according to the different conditions of the product.
Here is the forming process
1. Injection temperature must be integrated with the shape, size and mold structure of the product. The performance and requirements of the products can only be made after considering the conditions. Geralmente, the temperature of the molding is between 270-320 ℃, if the material temperature is higher than 340 ℃, PC will decompose, the product color will become darker, and the surface will show defects such as silver wire, dark strip, black spot and bubble, and the physical and mechanical properties also decrease significantly.
2. Injection pressure has a certain influence on the physical and mechanical properties, internal stress and molding shrinkage of PC products, which has a great influence on the appearance and demoulding performance of the products. Low or too high injection pressure will cause some defects of the products. Geralmente, the injection pressure is controlled between 80-120MPa, and for products with thin wall, long process, complex shape and small gate, In order to overcome the resistance of melt flow and fill the cavity in time, the higher injection pressure (120-145mpa) is selected. Desta forma, the products with complete and smooth surface are obtained.
3. The pressure maintaining pressure, the pressure holding time and the length of the holding time have a great influence on the internal stress of PC products. The pressure maintaining pressure is too small, and the small shrinkage effect is easy to appear vacuum bubble or concave surface, too much pressure retaining pressure, and the large internal stress is easily produced around the gate. In the actual processing, the method of high material temperature and low pressure keeping is often used to solve. The selection of pressure holding time should be determined by the thickness of the product, the size of the gate and the mold temperature. Geralmente, the small and thin products do not need a long holding time. Pelo contrário, the pressure holding time of the large and thick products should be longer. The length of pressure holding time can be determined by the test of gate sealing time.
4. The injection speed has no obvious influence on the performance of PC products. Except for thin-walled, small gate, deep hole and long process products, medium speed or slow processing is generally adopted, preferably multi-stage injection, and the slow fast slow multi-stage injection method is generally adopted.
5. The mold temperature can be controlled at 80-100 ℃, and the shape of the products with complex shape, thin and high requirements can also be increased to 100-120 ℃, but it can not exceed the hot deformation temperature of the mold.
6. Screw speed and back pressure are characterized by high viscosity of PC melt, which can be beneficial to plasticizing, exhaust and maintenance of plastic machine, to prevent screw overload. The speed requirement of screw should not be too high. Geralmente, it is appropriate to control the screw speed at 30-60r/min, while the back pressure should be controlled between 10-15% of injection pressure.
7. PC should strictly control the use of mold release agent in the process of injection molding, and the use of recycled materials should not exceed three times, and the usage should be about 20%. Requirements for the molding machine for PC products: the maximum injection volume (including runner, portão, etc.) of the products shall not be greater than 70-80% of the nominal injection quantity. The screw shall be of single head thread equal pitch and gradient compression screw with check ring. The length diameter ratio of screw l/d is 15-20, and the geometric compression ratio c/r is 2-3.
Sobre JasonMould Industrial Company Limited
Jasonmould é um Fabricante de moldes da china de moldes de plástico- molde de injeção, moldes de fundição sob pressão, moldagem por sopro de plástico, moldagem rotacional, médico moldagem por injeção de plástico, dois tiros moldagem por injeção de plástico, inserir moldagem, sobremoldagem, moldagem por injeção de metal, moldagem por micro injeção, moldagem por injeção de pó, moldagem por injeção de cerâmica, moldagem por injeção de líquido, moldagem por injeção husky, molde doméstico, molde de fundição, ferramenta de molde, moldes personalizados, moldes da china, ferramentas de prototipagem rápida, ferramentas de prototipagem de plástico, ferramentas de punção, matriz e ferramentas para peças móveis / celulares, partes automotivas, aspirador de pó, ferramentas recarregáveis, telefones, copiadoras, computadores, alto-falantes multimídia, e muitos outros produtos eletrônicos e eletrodomésticos. E também um fabricante de produtos de plástico, fabricante de moldes China- peças de plástico, tanque de água de plástico, bolas de plástico, recipientes de plástico, fivela de plástico, âncora de plástico, cabide de plástico, colher de plástico, encaixe de tubo de plástico, tombo de plástico, talheres de plástico, copos de plastico, garrafas plásticas, bandeja de plastico, recipiente plástico de cosmético, caixa de plástico, recipiente de plástico para comida, cadeiras de plástico, tampas de plástico, tampa de plástico, tubos de plástico, canos de água de plástico, maçanetas de plástico, tubo de plástico, caixas utilitárias de plástico, prateleiras de plástico e assim por diante.
Contato:
Pessoa: James Yuan
Empresa: JasonMould Industrial Company Limited
Adicionar: LongGang Village,LongXi Town,BoLuo County,Cidade de HuiZhou,Província de Guangdong, China
Tel: 86-752-6682869
E-mail: [email protected]
Local: https://www.jasonmolding.com/custom-injection-molding/
