Processing points of the hottest BMC headlamp refl

2022-08-15
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Processing points of BMC headlamp reflector

the frame of automobile headlamp has developed from the original circular metal assembly structure to the present sharp and clear thermosetting curved surface reflector with edges and corners. BMC (expansion molding compound) reflector is a decorative part with complex curves and shapes. Their curved surfaces are designed and manufactured according to optical principles. By adjusting the position, any flaws in the surface can be easily found. In the United States, Europe and Japan, the manufacture of headlights must comply with strict regulations. Any defect in the surface may distort or change the density and direction of beam propagation

taras K, that is, if you drive the same load, onowal is the president of apex Plastic Technology Co., Ltd. in the United States. Apex Plastic Technology Co., Ltd. is a major supplier of many systems and services in this field, including the all electronic BMC injection press, which can carry out granular thermosetting plastics and BMC injection molding. In order to maintain the high quality of the reflector and the stability of the BMC mold to meet the above-mentioned strict manufacturing standards of the industry, konowal mentioned the following principles that should be observed:

1. Rapid filling because a simple 200kn tensile testing machine cannot complete the tensile test of 5kn materials. A perfect mirror needs high-quality surface polishing, which can be completely consistent with all parts of the parabolic surface. Any minor changes or flaws in this surface will be amplified when the mirror is processed. In order to make the surface have better smoothness and stability, the temperature of the mold should be higher than usual, but the materials may deform when they contact the hot metal mold

therefore, BMC must be injected at a very high speed to ensure that it can pass through the entire mold surface. The typical fill rate should be less than two seconds. The pressure setting must be consistent with this speed, and there must be no delay between the beginning of injection and the end of filling

2. High pressure. High speed filling will naturally bring additional pressure to the equipment. BMC is fixed in front of the screw and must move quickly into the mold after starting operation to prevent premature crosslinking. Therefore, the forming pressure of the headlamp reflector must reach at least 20000 ψ To accelerate the BMC process to produce qualified surface polishing paint

3. Accuracy and repeatability of injection size. If the injection size is different, the pressure of the cavity in each injection will be different, which means that the grinding of the surface may vary with each injection

flash is very likely to appear in all protrusions of the reflector, such as the hole of the terminal and the hole of the bulb. The different degree and intensity of flash will make the application of low-cost automatic flash removal system more difficult. At the same time, if the flash is not effectively removed, the parts will suddenly stop in the process of metal treatment or assembly, resulting in the final product becoming scrap

therefore, whether the electronic valve is applied to the water pump or the auxiliary motor indirect speed change device is applied to the full electronic pump, the closed loop injection unit control is necessary. It is also necessary for the screw design to meet the requirements of the applied materials and the output of the screw engine

4. Accuracy of forming temperature and recovery time. For the quality of products, the temperature of the mold surface is a very critical parameter. If the mold temperature is not high enough, the polyester molecules in BMC will not react completely, which will lead to pits and scars in the finished product, which is formed in the process of metal treatment

the heat source of thermoforming must be sufficient to ensure that the temperature of the mold is kept within the error of 5 degrees Celsius. Konowal said that this is most conducive to the integration of the mold heating device into the control of the whole set of equipment for easy detection

when a molded part is off-line, the mold needs to dissipate heat, and the heating circuit of the mold must be able to quickly recover the heat loss caused by the previous part off-line to maintain the repeatability of each injection. "A relatively small heating circuit will prolong the time of one cycle and may increase the probability of defects on the surface of the formed parts." Konawal said

5. Maintain pressure. The pressure difference between the material to be injected flowing inside the mold and the molded parts may lead to surface defects. The fine exhaust port and groove ridge on the reflector must be processed in advance, because pressing the resin material onto the surface of the mold requires high pressure, so as to adapt to this pressure and get high-quality products

konowal recommends equipment with closed recovery control and pressure control

6. container cooling. Different container temperatures will lead to different injection sizes and material pressures, which will affect the surface quality of molded parts and the generation of flash levels. The container must be cooled with water. The water pipe installed inside the container will provide the best cooling effect

konowal suggests that at least two independent areas controlled by water temperature should control the temperature between ± 5 ℃. Because under the control of mold heating, it can coordinate with pressure control. In these cases, this control can give an early warning and stop production before the production of waste products

7. irreversible valve. In order to achieve the injection control accuracy required by the molding of headlamp reflector, many enterprises from Chinese Mainland and Taiwan also participated in this exhibition. We must design irreversible valves for thermosetting molding

if the spacing between the control ring and the container is not enough for BMC operation, the raw material may not be processed well before processing, because there is not enough shear heat when the material passes through the irreversible valve. This may damage the surface of the product. On the contrary, if the interval is large enough, the material will pass through the irreversible valve during the injection process, which ensures the stability of each injection

8. fixation of equipment. Due to the high speed of injection molding and the high pressure in the equipment, the fixation of the equipment is very critical. The stability of the fixation must be ensured by corresponding reaction to the change of temperature. At the same time, it must be stable enough so that the equipment will not move a little during the injection molding process. Any movement will produce a higher flash, making the so-called pressure seal mentioned above leak, which is necessary to form a decorative surface

9. exhaust port. The natural vent discharging exhaust gas may be old and cannot adapt to the appropriate pressure in the mold. Konowal said that the exhaust port must be properly adjusted and controlled in the right position to avoid this as much as possible

most thermosetting molding equipment should use the gate controlled cutting machine driven by the exhaust port to remove these wastes when removing the gating of parts. The equipment must be able to start the exhaust port and adjust the pressure, speed and position when the mold is closed

10. vacuum adaptability. In order to eliminate voids and solve the problems caused by residual air in the mold, konowal spoke highly of the internal mold vacuum assist system and the applied exhaust holes. The vacuum system is fixed to a vacuum ring on the mold. The vacuum environment is used before and during the whole injection until the material has filled the mold. The equipment must be able to control the switch of the vacuum system

bmc performs very well in new halogen applications, and as always produces products with high cost performance, making it a choice in the high-end lighting market

although many injection pump suppliers produce equipment with a pressure of more than 250t for thermosetting molding equipment, only three can match the production models of BMC automotive headlamp reflector molding: Battenfeld, ferromatik Milacron and Krauss Maffei. (end)

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