GAC Trumpchi GA3 car panel plastic mold

GAC Trumpchi GA3 car panel plastic moldFeatures:Name: GAC Trumpchi GA3 Car DVD PanelSize: 7-inch full touch screenWeight: 400gMaterial: PC+ABS (this series uses PC+ABS raw materials, high temperature

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  • 型号: GAC Trumpchi GA3 car panel plastic mold

GAC Trumpchi GA3 car panel plastic mold


广汽传祺GA3车载面板塑胶模具


Features:


Name: GAC Trumpchi GA3 Car DVD Panel


Size: 7-inch full touch screen


Weight: 400g


Material: PC+ABS (this series uses PC+ABS raw materials, high temperature resistance of 80 degrees, low temperature resistance of minus 40 degrees, good product toughness, good appearance, high brand quality)


Colour: Black


Applicable models: 7-inch GAC Trumpchi GA3 car panel






Product Details


Features: The surface is sprayed with black (original car style), fine workmanship, smooth lines, firmly pursuing the brand vision, committed to creating high-end brand effects for overseas cars, making high-end atmospheric car navigation panels, customized according to customer requirements!




Product advantages:




1.25 years of professional R&D and production experience in car navigation




2. Create professional design, production and processing services for car navigation panels




3. Free 30-day product structure warranty service for car navigation panels






Because plastic has light weight, good toughness, and easy molding. Low cost and other advantages, so in modern industry and daily products, more and more plastics are used instead of glass, especially in optical instruments and packaging industries, and the development is particularly rapid. However, due to the requirements for its transparency, abrasion resistance, and impact toughness, it is necessary for the composition of the plastic to be used in the process and equipment of the entire injection molding process. A lot of work has to be done for molds and so on to ensure that these plastics used to replace glass (hereinafter referred to as transparent plastics) have good surface quality, so as to meet the requirements of use.




Currently, the transparent plastics generally used in the market are polymethyl methacrylate (commonly known as acrylic or plexiglass, code PMMA) and polycarbonate (code PC). Polyethylene terephthalate (code-named PET), transparent nylon. AS (acrylonitrile-styrene copolymer), polysulfone (code-named PSF), etc., among which we are more exposed to PMMA. PC and PET three kinds of plastics, due to limited space, the following three kinds of plastics are used as examples to discuss the characteristics of transparent plastics and injection molding process.




1. The performance of transparent plastic




Transparent plastics must first have high transparency, and secondly they must have certain strength and abrasion resistance, impact resistance, good heat resistance, excellent chemical resistance, and low water absorption. Only in this way can they meet the requirements of transparency during use. Requirement and the same forever. PC is a more ideal choice, but mainly because of its high raw material price and difficult injection molding process, PMMA is still the main choice (for products with general requirements), and PPT has to be stretched to obtain good mechanical properties. Therefore, it is mostly used in packaging and containers.




2. Common issues that should be paid attention to in the process of transparent plastic injection molding




Due to the high light transmittance of transparent plastics, strict requirements on the surface quality of plastic products must be required, without any markings, pores, and whitening. Defects such as haze, black spots, discoloration, poor gloss, etc., so the raw materials and equipment are affected during the entire injection molding process. The design of molds and even products must pay great attention to and put forward strict and even special requirements.




Secondly, because transparent plastics mostly have high melting points and poor fluidity, in order to ensure the surface quality of the products, it is often necessary to make fine adjustments to the barrel temperature, injection pressure, injection speed and other process parameters, so that the mold can be filled with the plastic during injection. Will produce internal stress and cause product deformation and cracking.




In terms of equipment and mold requirements, injection molding process and product raw material processing, talk about the matters that should be paid attention to:




●Dry




Preparation and drying of raw materials Because any impurity in the plastic may affect the transparency of the product, it is stored and transported.




During the feeding process, attention must be paid to sealing to ensure that the raw materials are clean. In particular, the raw material contains water, which will cause the raw material to deteriorate after heating, so it must be dried, and when injection molding, a drying hopper must be used for feeding. It should also be noted that during the drying process, the input air should be filtered and dehumidified to ensure that the raw materials will not be contaminated.




●Cleaning of barrel, screw and accessories




In order to prevent the contamination of raw materials and the presence of old materials or impurities in the recesses of the screw and accessories, especially the presence of resin with poor thermal stability, screw cleaning agents should be used to clean all parts before use and after shutdown to prevent impurities from sticking. When there is no screw cleaning agent, the screw can be cleaned with PE, PS and other resins.




When temporarily shutting down, in order to prevent the raw materials from staying at high temperature for a long time and cause degrading, the temperature of the dryer and the barrel should be lowered, such as PC, PMMA and other barrels should be reduced to below 160 ℃. (The temperature of the hopper should be lowered to below 100°C for PC)




Problems that should be paid attention to in mold design (including product design)




In order to prevent the occurrence of poor flow back or uneven cooling, resulting in poor plastic molding, surface defects and deterioration;




Generally, the following points should be paid attention to when designing the mold:




●The wall thickness should be as uniform as possible, and the draft angle should be large enough;




●The transition part should be gradually. Smooth transition to prevent sharp corners. Sharp edges are generated, especially PC products must not have gaps;




●Gating. The runner should be as wide and short as possible, and the gate position should be set according to the shrinkage condensation process, and a cold well should be added if necessary;




●The mold surface should be smooth, with low roughness (recommended to be less than 0.8);




●Exhaust hole. The tank must be sufficient to expel air and gases in the melt in a timely manner;




●Except for PET, the wall thickness should not be too thin, generally not less than 1mm.




●Issues that should be paid attention to in injection molding process (including the requirements of injection molding machine)




In order to reduce internal stress and surface quality defects, the following issues should be paid attention to in the injection molding process:




●The injection molding machine with a special screw and a separate temperature control nozzle should be used;




●The injection temperature should be higher if the plastic resin does not decompose;




●Injection pressure: generally higher to overcome the defect of high melt viscosity, but too high pressure will cause internal stress and cause difficult demoulding and deformation;




●Injection speed: In the case of satisfying mold filling, generally it should be low, and it is recommended to use slow-fast-slow multi-stage injection;




●Holding time and molding cycle: Under the condition that the product is filled with mold and does not produce dents or bubbles; it should be as short as possible to minimize the residence time of the melt in the barrel;




●Screw speed and back pressure: under the premise of satisfying the quality of plasticization, it should be as low as possible to prevent the possibility of degrading;




●Mold temperature: The cooling of the product has a great impact on the quality, so the mold temperature must be able to accurately control the process. If possible, the mold temperature should be higher.

Other issues




In order to prevent the deterioration of the upper surface quality, generally use as little release agent as possible during injection molding; when using recycled material, it should not be more than 20%.




Except for PET, all products should be post-treated to eliminate internal stress. PMMA should be dried with hot air circulation at 70-80°C for 4 hours; PC should be in clean air and glycerin. Liquid paraffin is heated at 110-135℃, the time depends on the product, it is recommended to use more than 10 hours. However, PET must undergo a biaxial stretching process to obtain good mechanical properties.

Third, the injection molding process of transparent plastic

Process characteristics of transparent plastic

In addition to the above common problems, transparent plastics also have some technological characteristics, which are described as follows:

1. Process characteristics of PMMA

PMMA has high viscosity and poor fluidity. Therefore, high material temperature and high injection pressure must be used for injection molding. The influence of injection temperature is greater than injection pressure, but the increase in injection pressure will help improve the shrinkage of the product.

The injection temperature range is wide, the melting temperature is 160°C, and the decomposition temperature is 270°C, so the material temperature adjustment range is wide and the manufacturability is better. Therefore, to improve fluidity, start from the injection temperature. The impact resistance is poor, the wear resistance is not good, it is easy to scratch, and it is easy to be brittle. Therefore, it is necessary to increase the mold temperature and improve the condensation process to overcome these defects.

2. Process characteristics of PC

PC has high viscosity, high melt temperature and poor fluidity, so it must be injected at a higher temperature (between 270-320℃). Relatively speaking, the temperature adjustment range of the material is narrow, and the manufacturability is not as good as PMMA. The injection pressure has little effect on the fluidity, but due to the high viscosity, the injection pressure is still higher. Correspondingly, in order to prevent internal stress, the pressure holding time should be as short as possible.

The shrinkage rate is large, the size is stable, but the internal stress of the product is large, and it is easy to crack. Therefore, it is better to increase the temperature instead of pressure to improve the fluidity, and increase the mold temperature, improve the mold structure and post-processing to reduce the possibility of cracking. When the injection speed is low, defects such as ripples are prone to occur at the gate. The temperature of the radiating nozzle must be controlled separately, the mold temperature must be high, and the runner and gate resistance should be small.

3. Process characteristics of PET

PET molding temperature is high, and the material temperature adjustment range is narrow (260-300℃), but after melting, it has good fluidity, so the manufacturability is poor, and it is often necessary to add anti-spreading devices in the nozzle. The mechanical strength and performance are not high after injection, and the performance must be improved through the stretching process and modification.

Accurate control of mold temperature is to prevent warpage. It is an important factor of deformation, so it is recommended to use hot runner molds. The mold temperature should be high, otherwise it will cause poor surface gloss and difficulty in demolding.

Fourth, the defects and solutions of transparent plastic parts

The shortcomings are as follows:

Silver pattern

Influenced by the internal stress anisotropy during the filling and condensation process, the stress generated in the vertical direction causes the resin to flow upward orientation, and the refractive index is different from the non-flow orientation to produce flashing silk patterns. When it expands, it may cause The product has cracks. In addition to paying attention to the injection molding process and mold, it is recommended that the product be annealed. For example, the PC material can be heated to above 160°C for 3-5 minutes, and then cooled naturally.

bubble

The water vapor and other gases mainly contained in the resin cannot be discharged (during the mold condensation process), or due to insufficient mold filling, the condensation surface condenses too quickly to form a vacuum bubble.




Poor surface gloss

The main reason is that the roughness of the mold is large, and on the other hand, the resin can not copy the state of the mold surface due to premature condensation. All these make the surface produce small irregularities and make the product lose its luster.

Shock

It refers to the dense ripples formed from the straight gate as the center. The reason is that because the melt viscosity is too large, the front end material has been condensed in the cavity, and then the material breaks through the condensing surface, causing the surface to appear shock lines.

White haze

It is mainly caused by dust falling into the raw materials in the air or too much water content in the raw materials.

White smoke and black spots

It is mainly formed by the decomposition or deterioration of the resin in the barrel due to partial overheating of the plastic in the barrel.