Multi-cavity hot runner mold for injection molding machining of car lamp and forming process

Abstract

The invention relates to the technical field of car lamp injection molding machining, in particular to a multi-cavity hot runner mold for car lamp injection molding machining and a forming technology.The multi-cavity hot runner mold for car lamp injection molding machining comprises a lower fixed mold, an upper movable mold, a base and a supporting table; the lampshade cavity is formed in the surface of the lower fixed mold; the hot runner unit is formed in the upper movable mold and corresponds to the lampshade cavity; the independent temperature control area is arranged outside the hot runner unit; the injection molding opening is formed in the surface of the upper movable mold; the hot runner unit comprises an injection molding channel arranged below the injection molding opening, four main runners arranged below the injection molding channel, eight branch runners arranged at the end parts of the four main runners and nozzle parts arranged at the end parts of the branch runners; a high-balance multi-cavity total hot runner system is formed through the multiple cavities and the hot runner, and the defects of chromatic aberration, flash, shrinkage and the like are effectively eliminated by combining the multiple independent temperature control areas divided by the hot runner system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle lamp injection molding, and particularly relates to a multi-cavity hot runner mold for vehicle lamp injection molding and a molding process. BACKGROUND

[0002] With the rapid development of global new energy automobile industry, the market demand for small electric passenger cars (such as A00 / A0 level vehicles) continues to rise due to their economy and urban commuting advantages. As a key appearance and safety functional part, the vehicle lamp cover (including daytime running lamp cover, turn signal lamp cover, tail lamp cover, etc.) not only needs to meet the stringent optical performance requirements such as high light transmittance (≥90%) and high surface gloss (no welding line, no flow mark, no black spot), but also needs to have good dimensional stability and assembly consistency. Currently, such lamp covers are generally made of transparent engineering plastics such as polycarbonate (PC) or polymethyl methacrylate (PMMA) through injection molding.

[0003] During the injection molding of the automobile lamp cover, the traditional cold flow runner has serious waste of condensed material, low material utilization rate, and limited production capacity of single cavity or few cavities, which is difficult to meet the demand of mass production. If the runner layout is asymmetric, the temperature control precision is insufficient, or the gate design is unreasonable, the melt filling pressure and temperature of each cavity will be different, which will easily cause color difference, shrinkage, flash or welding line position deviation, etc.

[0004] Therefore, a multi-cavity hot runner mold can be designed to prepare a vehicle lamp by forming a high-balance multi-cavity full hot runner system through "multi-cavity + hot runner". SUMMARY

[0005] In order to overcome the problems of traditional cold flow runner, such as serious waste of condensed material, low material utilization rate, and limited production capacity of single cavity or few cavities.

[0006] The technical scheme of the present application is as follows: a multi-cavity hot runner mold for vehicle lamp injection molding, comprising a lower fixed mold, an upper movable mold, a base and a support table; further comprising a lamp cover cavity opened on the surface of the lower fixed mold, a hot runner unit corresponding to the lamp cover cavity opened in the interior of the upper movable mold, an independent temperature control area arranged outside the hot runner unit, and an injection port arranged on the surface of the upper movable mold, the hot runner unit comprising an injection channel arranged below the injection port, four main flow channels arranged below the injection channel, eight branch flow channels arranged at the end of the four main flow channels, and a nozzle portion arranged at the end of the branch flow channels, the length and cross-sectional area of the main flow channels and each branch flow channel are strictly symmetrical, the bottom of the nozzle portion is a reverse triangle, a needle valve type nozzle driven by a pneumatic drive is installed inside the nozzle portion, the gate position corresponding to the nozzle portion is arranged at the edge buckle area of the lamp cover cavity, an inflation mechanism for assisting the smooth demolding of the product is arranged outside the edge buckle area, and an electromagnetic vibrator is integrated at the back of the upper movable mold to apply high-frequency micro-amplitude vibration before ejection to destroy the molecular adsorption force between the plastic and the mold surface. The independent temperature control zones include a main flow channel zone arranged outside the main flow channel, a branch flow channel zone arranged outside the branch flow channel, and a nozzle zone arranged outside the nozzle part, and the main flow channel zone, the branch flow channel zone, and the nozzle zone are respectively provided with corresponding independent heaters and micro thermocouples.

[0007] As preferred, the periphery of the lampshade cavity is provided with a conformal cooling water channel, which includes a central lens zone, an edge thin-wall zone, and a mounting buckle zone, each zone is provided with independent water inlets and outlets, the water inlets include a first water inlet communicating with the central lens zone, a second water inlet communicating with the edge thin-wall zone, and a third water inlet communicating with the mounting buckle zone. The outlets are respectively provided with three groups corresponding to the central lens zone, the edge thin-wall zone, and the mounting buckle zone.

[0008] As preferred, the inflation mechanism includes an L-shaped air channel, a micro-hole arranged at the root position of the edge buckle zone, and a quick-plug air connector detachably mounted on both sides of the lower fixed mold, the size of the micro-hole is Φ0.5~1.2mm.

[0009] As preferred, the L-shaped air channel communicates with the micro-hole and the quick-plug air connector, after the mold is opened, the control system starts a short-term blowing, forming an air film between the product and the lower fixed mold, eliminating vacuum adsorption, and assisting the product to be smoothly demolded.

[0010] As preferred, the needle valve type nozzle includes a long valve needle, a short valve needle attached to the outside of the long valve needle, a sealing plate fixed to the upper end of the long valve needle and the short valve needle, and a high-temperature spring fixed between the top of the upper movable mold pneumatic driving zone and the sealing plate, which is used for the reset of the sealing plate, so that the long valve needle can cut off the gate.

[0011] As preferred, the nozzle part and the outer part of the upper movable mold pneumatic driving zone are provided with an independent hidden blowing channel, which includes an external air inlet channel and a branch connection channel, and the external air inlet channel extends to the outer surface of the lower fixed mold.

[0012] As preferred, the branch connection channel is used for connecting the nozzle part and the pneumatic driving zone of the upper movable mold, the lower end of the upper movable mold pneumatic driving zone is provided with an air hole for the movement of the short valve needle, the branch connection channel communicates with the air hole, and the short valve needle is used for guiding and sealing the air hole. After the external air inlet channel is filled with air, the sealing plate is pushed upwards, when the sealing plate moves upwards to the upper end of the branch connection channel, the gas will enter the channel below the short valve needle from the branch connection channel, and then enter the inside of the nozzle part to blow out the residual melt at the bottom.

[0013] As preferred, low-thermal-conductivity ceramic heat insulation rings are embedded around the main flow channel zone and the branch zone, and high-thermal-conductivity copper alloy inserts are embedded around the nozzle zone, and the high-thermal-conductivity copper alloy inserts transmit heat to the external forced air cooling fins of the mold through high-thermal-conductivity copper alloy pipes, so that the forced air cooling fins can be quickly cooled after being turned on.

[0014] As preferred, the micro-thermocouples are respectively arranged at the intersection of the main flow channel, the corner of the branch flow channel and the inverted triangular area of the nozzle part, the change of thermal load is predicted according to the injection cycle, the heating power is adjusted in advance, and the global temperature difference is stabilized within ±0.8℃.

[0015] A multi-cavity hot runner molding process for vehicle lamp injection molding processing, comprising the following steps: S1: install the multi-cavity hot runner mold on the injection molding machine, ensure that the positioning accuracy of the four cavities is ≤0.02 mm, start the mold temperature machine, preheat the partitioned cooling system of the fixed mold to the set temperature, set 85-90℃ for the center lens area, 88-92℃ for the edge thin-walled area, and 90-95℃ for the installation buckle area, at the same time, start the hot runner temperature control system, gradually heat to the process temperature (PC material: 290-300℃) in three stages (main flow channel area, branch area, nozzle area), and keep for 30 minutes, ensure that the global temperature difference is ≤±1℃; S2: the injection molding machine is clamped, the clamping force is set to product projection area×80-100MPa, the injection unit is started, the melt flows into four main flow channels from the injection channel, and then enters the corresponding two branch flow channels of each main flow channel, and then enters the corresponding nozzle part, in this process, the corresponding independent heaters and micro-thermocouples of the independent temperature control area are opened at the same time, and the temperature difference of each flow channel is ensured to be ≤±1℃ by the central temperature controller PID; S3: when the melt is completely poured into the nozzle part, open the pneumatic drive module connected to the outside, the external gas enters the pneumatic drive area of the upper movable mold through the external gas inlet channel, the gas inlet amount is controlled to be 1 / 2 of the peak state, at this time the sealing plate is lifted to a certain height and located below the branch connecting channel, the long valve needle is separated from the inverted triangular area of the nozzle part, the gate is opened, and the melt enters the lampshade cavity of the lower fixed mold to form a product, a three-stage dynamic injection strategy is adopted in this stage, the first stage is low pressure and slow speed, filling to 50% of the far end of the product to prevent jet marks, the second stage is medium pressure and medium speed, completing the main body filling, and the third stage is high pressure switching, when the mold cavity pressure sensor feedback reaches the set threshold value, it is automatically switched to pressure holding, the eight needle valve type nozzles are adjusted according to the preset timing delay (0-50ms) to guide the weld line to move to the non-appearance area; S4: enter the gradient pressure holding stage, the first pressure holding: 80MPa, lasting 2.0s, the second pressure holding: 60MPa, lasting 1.5s, after the pressure holding is over, the gas in the pneumatic drive area is re-pumped back, at this time the long valve needle is quickly lowered to the bottom of the inverted triangular bottom of the nozzle part through the reset of the high-temperature spring, the gate is quickly closed and the melt is cut off, a small amount of melt is left at the tip of the nozzle part, at the same time the partition cooling system is started synchronously, the cooling water temperature is kept at 20℃ for the lens area, 25℃ for the edge area, and 30℃ for the buckle area, and the cooling lasts for 30-35 seconds, ensuring that the product ejection temperature is ≤110℃; S5: 0.5 seconds before the end of cooling, start the electromagnetic vibrator on the back of the upper movable mold, last for 0.3 seconds, destroy the molecular adsorption force between the product and the mold surface; S6: the injection molding machine opens the mold to the set position, the control system starts the inflation mechanism at the lower fixed mold to assist demolding, 0.3 MPa compressed air is introduced into the L-shaped air passage, lasts for 0.5 seconds, a uniform air film is formed between the product buckle root and the mold surface, combined with the mechanical hand grabbing, the demolding operation is completed; S7: after each continuous production mold, the control system starts the cleaning and blowing program: compressed air enters the branch connection channel through the external air inlet channel, and flows into the nozzle part through the short valve needle guided air hole, blows out the residual melt at the bottom to the waste collection port, and completes the online self-cleaning.

[0016] The beneficial effects of the present application are: 1. Form a high balance multi-cavity full hot runner system through "multi-cavity + hot runner", 4 cavities are symmetrically arranged in the lower fixed mold, the output per unit time is improved, 2 hot runner channels are arranged above each cavity of the upper movable mold, one main runner is connected to the upper end of each 2 branches, 4 main runners are arranged, which are connected to the midpoint positions of each branch at a certain inclination angle, the top of the main runner is connected into one feeding channel, the length and cross-sectional area of the main runner and each branch runner are strictly symmetrical, combined with the multiple independent temperature control zones divided by the hot runner system (such as the main runner zone, the branch zone and the nozzle zone), the temperature difference of each runner is ensured to be ≤±1℃, which effectively eliminates defects such as color difference, flash and shrinkage; 2. By setting the conformal cooling water channel, and dividing it into three functional zones of center lens zone, edge thin wall zone and installation buckle zone, each zone is independently temperature controlled, so that the shrinkage of the thick wall zone is fully compensated, the precise zoned cooling effectively inhibits warping and shrink marks; 3. Integrated "high frequency micro-amplitude vibration + micro-pore air film" double auxiliary demolding mechanism: the electromagnetic vibrator instantaneously destroys the molecular adsorption force between the plastic and the mold surface before the mold is opened, the L-shaped air passage and the Φ0.5~1.2 mm micro-pore form a uniform air film at the buckle root, and the vacuum adsorption is completely eliminated. The demolding force is reduced by more than 40%, the product surface is not scratched and has no indentation, the buckle root has no micro-cracks, and the safety hidden danger caused by stress cracking in use is eliminated; 4. A cleaning and blowing channel independent of the pneumatic driving system is added in the needle valve type nozzle structure, the short valve needle guides the sealed air hole to realize the intelligent switching of "sealing during injection molding and opening during blowing", and the nozzle bottom residual melt is removed by automatic pulse blowing every 1000 mold times, without the need of stopping and cleaning, which greatly improves the comprehensive efficiency of the equipment; 5. The main runner intersection area is embedded with a low thermal conductivity ceramic heat insulation ring to inhibit heat accumulation; the nozzle area is configured with a high thermal conductivity copper alloy insert sleeve and connected with a forced air cooling fin to actively strengthen heat dissipation, so that the global temperature difference is stabilized within ±0.8℃, effectively preventing the thermal degradation of PC / PMMA materials and ensuring the long-term stability of optical performance. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The diagram shown is a schematic representation of the overall assembly structure of the present invention; Figure 2 The diagram shown illustrates the installation structure of the present invention. Figure 1 ; Figure 3 The diagram shown illustrates the installation structure of the present invention. Figure 2 ; Figure 4 The diagram shown is a schematic representation of the lower mold structure of the present invention. Figure 5 The diagram shown is a schematic representation of the upper mold structure of the present invention; Figure 6 The diagram shown is a distribution diagram of the hot runner unit of the present invention; Figure 7 The diagram shown is a side sectional view of the upper moving mold and the lower fixed mold of the present invention; Figure 8 The diagram shown is a cross-sectional view of the upper moving mold and the lower fixed mold of the present invention. Figure 9 The present invention is shown Figure 8 Enlarged view of point A in the middle; Figure 10 The present invention is shown Figure 8 Enlarged view at point B in the middle; Figure 11 The present invention is shown Figure 7 Enlarged view of point C.

[0018] Explanation of reference numerals in the attached drawings: 1. Lower fixed mold; 2. Upper moving mold; 3. Injection port; 31. Injection channel; 32. Main runner; 33. Branch runner; 34. Nozzle section; 4. Base; 5. Support platform; 6. Electromagnetic vibrator; 7. Needle valve nozzle; 71. Long valve needle; 72. Short valve needle; 73. Sealing plate; 74. High-temperature spring; 8. Low thermal conductivity ceramic heat insulation ring; 9. Independent heater; 10. High thermal conductivity copper alloy inlay. 11. Lampshade cavity; 1101. Edge snap-fit ​​area; 111. Branch connection channel; 112. External air intake channel; 121. Central lens area; 122. Edge thin-walled area; 123. Mounting snap-fit ​​area; 1241. First water inlet; 1242. Second water inlet; 1243. Third water inlet; 125. Water outlet; 131. L-shaped air channel; 132. Micropore; 133. Quick-connect air connector. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Please see Figures 1-11The application provides an embodiment: a multi-cavity hot runner mold for vehicle lamp injection processing, comprising a lower fixed mold 1, an upper movable mold 2, a base 4 and a support table 5; further comprising a lamp cover cavity 11 opened on the surface of the lower fixed mold 1, a hot runner unit corresponding to the lamp cover cavity 11 opened in the inside of the upper movable mold 2, an independent temperature control area arranged outside the hot runner unit and an injection port 3 arranged on the surface of the upper movable mold 2, the hot runner unit comprises an injection channel 31 arranged below the injection port 3, four main flow channels 32 arranged below the injection channel 31, eight branch flow channels 33 arranged at the end of the four main flow channels 32 and nozzle parts 34 arranged at the end of the branch flow channels 33, the length and cross-sectional area of the main flow channels 32 and each branch flow channel 33 are strictly symmetrical, the bottom of the nozzle part 34 is a reverse triangle, the gate gradually becomes smaller, and is matched with a needle valve type nozzle 7, the needle valve type nozzle 7 is mounted in the inside of the nozzle part 34, the corresponding gate position of the nozzle part 34 is arranged at the edge buckle area 1101 of the lamp cover cavity 11, the outside of the edge buckle area 1101 is provided with an inflation mechanism for assisting the smooth demolding of the product, the upper movable mold 2 is integrated with an electromagnetic vibrator 6 at the back, high-frequency micro-amplitude vibration is applied before ejection, and the molecular adsorption force between the plastic and the mold surface is destroyed; the independent temperature control area comprises a main flow channel area arranged outside the main flow channel 32, a branch area arranged outside the branch flow channel 33 and a nozzle area arranged outside the nozzle part 34, the main flow channel area, the branch area and the nozzle area are respectively provided with corresponding independent heaters 9 and micro thermocouples, which are adjusted by a central temperature controller PID, and the temperature difference of each flow channel is ensured to be ≤±1℃.

[0021] Please refer to Figure 4 、 7 、8, the periphery of the lamp cover cavity 11 is provided with a conformal cooling water channel, the conformal cooling water channel comprises a center lens area 121, an edge thin wall area 122 and a mounting buckle area 123, each area is provided with an independent water inlet and a water outlet 125, the water inlet comprises a first water inlet 1241 communicating with the center lens area 121, a second water inlet 1242 communicating with the edge thin wall area 122 and a third water inlet 1243 communicating with the mounting buckle area 123; the water outlet 125 is provided with three groups corresponding to the center lens area 121, the edge thin wall area 122 and the mounting buckle area 123 respectively. The lower fixed mold 1 is divided into three cooling functional areas, each area is configured with an independent water inlet / outlet, connected with a multi-loop control system of a mold temperature machine, each area can be set to different water temperature, matched with local heat load, thick wall area slow cooling shrinkage, thin wall area fast cooling shaping, internal stress is inhibited, thick wall area shrinkage is fully compensated, precise partition cooling, warping and shrinkage are effectively inhibited.

[0022] Please refer to Figure 4 、 8, 10, the inflation mechanism includes L-shaped airway 131, micro-hole 132 opened in the root position of the edge buckle area 1101, and quick plug gas connector 133 detachably mounted on both sides of the lower mold 1, the size of the micro-hole 132 is Φ0.5~1.2mm, the L-shaped airway 131 is communicated with the micro-hole 132 and the quick plug gas connector 133, after the mold is opened, the control system starts to blow for a short time, forming an air film between the product and the lower mold 1, eliminating vacuum adsorption, assisting the product to be smoothly demolded, the demolding force is reduced by more than 40%, the product surface is not scratched and has no pressure mark, and the buckle root has no micro-crack.

[0023] Please refer to Figure 8 、 9 , the needle valve type nozzle 7 includes a long valve needle 71, a short valve needle 72 attached to the outside of the long valve needle 71, a sealing plate 73 fixed to the upper end of the long valve needle 71 and the short valve needle 72, and a high-temperature spring 74 fixed between the top of the upper movable mold 2 pneumatic driving area and the sealing plate 73, the high-temperature spring 74 is used for resetting the sealing plate 73, so that the long valve needle 71 can cut off the gate, the nozzle part 34 and the outside of the upper movable mold 2 pneumatic driving area are provided with independent hidden blowing channels, the hidden blowing channels include an external air inlet channel 112 and a branch connecting channel 111, the external air inlet channel 112 extends to the outer surface of the lower mold 1, and the branch connecting channel 111 is used for connecting the nozzle part 34 and the pneumatic driving area of the upper movable mold 2; a gas hole for moving the short valve needle 72 is arranged at the lower end of the upper movable mold 2 pneumatic driving area, the branch connecting channel 111 is communicated with the gas hole, and the short valve needle 72 is used for guiding and sealing the gas hole; after the external air inlet channel 112 is filled with air, the sealing plate 73 is driven upward, when the sealing plate 73 moves upward to the upper end of the branch connecting channel 111, the gas enters the channel below the short valve needle 72 from the branch connecting channel 111, and enters the inside of the nozzle part 34 to blow out the residual melt at the bottom. Separate the cleaning function from the injection driving to realize "sealing during injection and opening during blowing".

[0024] Please refer to Figure 7 、 11 , the main flow channel area and the branch area are embedded with low-thermal-conductivity ceramic heat insulation rings 8, and the nozzle area is embedded with high-thermal-conductivity copper alloy inserts 10, the high-thermal-conductivity copper alloy inserts 10 transmit heat to the external forced air cooling fins of the mold through high-thermal-conductivity copper alloy pipes, so that the forced air cooling fins can be quickly cooled after being opened, and the micro thermocouples are respectively arranged at the intersection of the main flow channel 32, the corner of the branch flow channel 33 and the inverted triangular area of the nozzle part 34, the heating power is adjusted in advance according to the injection cycle to predict the change of thermal load, the main flow channel is prevented from overheating, the nozzle area is prevented from being insufficiently heated, the global thermal balance is realized, and the global temperature difference is stably kept within ±0.8℃.

[0025] A multi-cavity hot runner forming process for vehicle lamp injection molding, comprising the following steps: S1: Install the multi-cavity hot runner mold on the injection molding machine, ensure that the four cavities are symmetrically positioned with an accuracy of ≤0.02 mm, start the mold temperature machine, and preheat the partitioned cooling system of the fixed mold to the set temperature. The center lens area 121 is set to 85-90°C, the edge thin wall area 122 is set to 88-92°C, and the installation buckle area 123 is set to 90-95°C. At the same time, start the hot runner temperature control system, gradually warm up to the process temperature (PC material: 290-300°C) in three stages (main runner area, branch area, nozzle area), and maintain for 30 minutes, ensuring that the global temperature difference is ≤±1°C; S2: Close the mold of the injection molding machine, set the locking force to product projection area x 80-100 MPa, start the injection unit, and melt from the injection channel 31 flows into four main runners 32, and then into two branch runners 33 corresponding to each main runner 32, and then into the corresponding nozzle part 34. During this process, open the corresponding independent heaters 9 and micro thermocouples in the independent temperature control area, and adjust the temperature difference between the runners to ≤±1°C by the central temperature controller PID; S3: When the melt is completely filled into the nozzle part 34, open the pneumatic drive module connected to the outside, and the external gas enters the pneumatic drive area of the upper movable mold 2 through the external air inlet channel 112, controlling the air intake amount to be 1 / 2 of the peak state. At this time, the sealing plate 73 is lifted to a certain height and is located below the branch connection channel 111, the long valve needle 71 is separated from the inverted triangular area of the nozzle part 34, the gate is opened, and the melt enters the lampshade cavity 11 of the lower fixed mold 1 to form a product. During this stage, a three-stage dynamic injection strategy is adopted. The first stage is low pressure and slow speed, filling to 50% of the product far end to prevent jet marks. The second stage is medium pressure and medium speed, completing the main body filling. The third stage is high pressure switching. When the mold cavity pressure sensor feedback reaches the set threshold, it automatically switches to pressure holding. The eight needle valve nozzles are adjusted according to the preset timing and opened with a delay of 0-50 ms, guiding the weld line to move to a non-visual area; S4: Enter the gradient pressure holding stage. The first pressure holding is 80 MPa for 2.0 s, and the second pressure holding is 60 MPa for 1.5 s. After the pressure holding is completed, the gas in the pneumatic drive area is retracted. At this time, the long valve needle 71 is quickly lowered to the bottom of the inverted triangular bottom of the nozzle part 34 by the reset of the high temperature spring 74, quickly closing the gate and cutting off the melt. A small amount of melt is left at the tip of the nozzle part 34, and at the same time, the partition cooling system is started simultaneously. The cooling water temperature is maintained at 20°C for the lens area, 25°C for the edge area, and 30°C for the buckle area. Cool for 30-35 seconds to ensure that the product ejection temperature is ≤110°C; S5: 0.5 seconds before the end of cooling, start the electromagnetic vibrator 6 at the back of the upper movable mold 2, and last for 0.3 seconds to break the molecular adsorption force between the product and the mold surface; S6: The injection molding machine opens the mold to the set position, and the control system starts the inflation mechanism at the lower mold 1 to assist demolding. 0.3 MPa compressed air is introduced into the L-shaped air duct 131, lasting for 0.5 seconds, forming a uniform air film between the product buckle root and the mold surface, cooperating with the mechanical hand to grab, and completing the demolding operation; S7: After every 1000 continuous production cycles, the control system starts the cleaning and blowing program: compressed air enters the branch connection channel 111 through the external air inlet channel 112, and flows into the nozzle part 34 through the gas hole guided by the short valve needle 72, blowing out the residual melt at the bottom to the waste collection port, completing the online self-cleaning.

Claims

1. A multi-cavity hot runner mold for automotive headlight injection molding, comprising a lower fixed mold (1), an upper moving mold (2), a base (4), and a support platform (5); characterized in that: It also includes a lampshade cavity (11) formed on the surface of the lower fixed mold (1), a hot runner unit formed inside the upper moving mold (2) corresponding to the lampshade cavity (11), an independent temperature control zone set outside the hot runner unit, and an injection port (3) set on the surface of the upper moving mold (2). The hot runner unit includes an injection channel (31) set below the injection port (3), four main runners (32) set below the injection channel (31), eight branch runners (33) set at the ends of the four main runners (32), and nozzles set at the ends of the branch runners (33). 34), the length and cross-sectional area of ​​the main channel (32) and each branch channel (33) are strictly symmetrical. The bottom of the nozzle part (34) is an inverted triangle. The nozzle part (34) is equipped with a pneumatically driven needle valve nozzle (7). The gate position corresponding to the nozzle part (34) is set in the edge snapping area (1101) of the lamp cover cavity (11). An inflation mechanism for assisting product demolding is provided on the outside of the edge snapping area (1101). The upper moving mold (2) integrates an electromagnetic vibrator (6) on the back. High-frequency micro-amplitude vibration is applied before ejection to destroy the molecular adsorption force between the plastic and the mold surface. The independent temperature control zone includes the main channel zone located outside the main channel (32), the branch channel zone located outside the branch channel (33), and the nozzle zone located outside the nozzle section (34). The main channel zone, the branch channel zone, and the nozzle zone are each equipped with a corresponding independent heater (9) and a miniature thermocouple.

2. A multi-cavity hot runner mold for automotive headlight injection molding according to claim 1, characterized in that: The lamp cover cavity (11) is provided with conformal cooling channels around its periphery. The conformal cooling channels include a central lens area (121), an edge thin-walled area (122), and a mounting clip area (123). Each area is equipped with an independent inlet and outlet (125). The inlets include a first inlet (1241) connecting the central lens area (121), a second inlet (1242) connecting the edge thin-walled area (122), and a third inlet (1243) connecting the mounting clip area (123). The outlet (125) is provided with three sets corresponding to the central lens area (121), the edge thin-wall area (122), and the mounting buckle area (123).

3. A multi-cavity hot runner mold for automotive headlight injection molding according to claim 1, characterized in that: The inflation mechanism includes an L-shaped air passage (131), a microhole (132) located at the root of the edge snap-fit ​​area (1101), and a quick-connect air connector (133) that is detachably installed on both sides of the lower mold (1). The size of the microhole (132) is Φ0.5~1.2mm.

4. A multi-cavity hot runner mold for automotive headlight injection molding according to claim 3, characterized in that: The L-shaped air channel (131) is connected to the micropore (132) and the quick-connect air connector (133). After the mold is opened, the control system starts a short blowing to form an air film between the product and the lower mold (1), eliminating vacuum adsorption and assisting the product to be demolded smoothly.

5. A multi-cavity hot runner mold for automotive headlight injection molding according to claim 1, characterized in that: The needle valve nozzle (7) includes a long valve needle (71), a short valve needle (72) attached to the outside of the long valve needle (71), a sealing plate (73) fixed to the upper end of the long valve needle (71) and the short valve needle (72), and a high temperature spring (74) fixed between the top of the pneumatic drive area of ​​the upper moving mold (2) and the sealing plate (73). The high temperature spring (74) is used to reset the sealing plate (73) so that the long valve needle (71) can cut off the gate.

6. A multi-cavity hot runner mold for automotive headlight injection molding according to claim 5, characterized in that: The nozzle section (34) and the pneumatic drive area of ​​the upper moving mold (2) are provided with independent hidden air blowing channels. The hidden air blowing channels include an external air intake channel (112) and a branch connection channel (111). The external air intake channel (112) extends to the outer surface of the lower fixed mold (1).

7. A multi-cavity hot runner mold for automotive headlight injection molding according to claim 6, characterized in that: The branch connection channel (111) is used to connect the nozzle part (34) and the pneumatic drive area of ​​the upper moving mold (2). The lower end of the pneumatic drive area of ​​the upper moving mold (2) is provided with an air hole for the movement of the short valve needle (72). The branch connection channel (111) is connected to the air hole. The short valve needle (72) is used to guide and seal the air hole. After the external air intake channel (112) takes in air, it drives the sealing plate (73) to push upward. When the sealing plate (73) moves to the upper end of the branch connection channel (111), the gas will enter the channel under the short valve needle (72) from the branch connection channel (111) and enter the nozzle part (34) to blow out the melt remaining at the bottom.

8. A multi-cavity hot runner mold for automotive headlight injection molding according to claim 1, characterized in that: Low thermal conductivity ceramic heat insulation rings (8) are embedded around the main channel area and the branch area, and high thermal conductivity copper alloy inserts (10) are embedded around the nozzle area. The high thermal conductivity copper alloy inserts (10) transfer heat to the external forced air cooling heat sink of the mold through the high thermal conductivity copper alloy tube, so that the forced air cooling heat sink can cool down quickly after it is turned on.

9. A multi-cavity hot runner mold for automotive headlight injection molding according to claim 8, characterized in that: Miniature thermocouples are respectively set at the intersection of the main flow channel (32), the corner of the branch flow channel (33) and the inverted triangle area of ​​the nozzle (34). Based on the injection cycle, the heat load changes are predicted and the heating power is adjusted in advance to keep the temperature difference within ±0.8℃.

10. A multi-cavity hot runner molding process for automotive headlight injection molding, characterized in that: The multi-cavity hot runner mold for automotive headlight injection molding as described in claim 9 includes the following steps: S1: Install the multi-cavity hot runner mold on the injection molding machine, ensuring that the symmetrical positioning accuracy of the four cavities is ≤0.02 mm. Start the mold temperature controller and preheat the fixed mold cooling system to the set temperature in each zone. Set the central lens area (121) to 85–90℃, the edge thin wall area (122) to 88–92℃, and the installation buckle area (123) to 90–95℃. At the same time, start the hot runner temperature control system and gradually raise the temperature to the process temperature according to the three-level zones, and keep it warm for 30 minutes to ensure that the temperature difference across the entire area is ≤±1℃. S2: The injection molding machine closes the mold, the clamping force is set to the product projection area × 80-100MPa, the injection unit is started, the melt flows from the injection channel (31) into the four main channels (32), and enters the two branch channels (33) corresponding to each main channel (32), and then enters the corresponding nozzle section (34). During this process, the independent heaters (9) and micro thermocouples corresponding to the independent temperature control area are opened at the same time, and the temperature difference of each channel is ≤ ±1℃ by the central temperature controller PID adjustment. S3: When all the melt flows into the nozzle section (34), the pneumatic drive module connected to the outside is opened. The external gas enters the pneumatic drive area of ​​the upper moving mold (2) through the external air intake channel 112. The air intake volume is controlled to be 1 / 2 of the peak state. At this time, the sealing plate (73) is raised to a certain height and located below the branch connection channel (111). The long valve needle (71) is removed from the inverted triangle area of ​​the nozzle section (34) and the gate is opened. The melt enters the lampshade cavity (11) of the lower fixed mold (1) for injection molding. This stage adopts a three-stage dynamic injection strategy. The first stage is low pressure and slow speed, filling to 50% of the far end of the product to prevent spray marks. The second stage is medium pressure and medium speed to complete the main body filling. The third stage is high pressure switching. When the mold cavity pressure sensor feedback reaches the set threshold, it automatically switches to pressure holding. The 8 needle valve nozzles are finely adjusted according to the preset timing to open the delay and guide the weld line to move to the non-appearance area. S4: Enter the gradient holding pressure stage. First holding pressure: 80MPa, lasting 2.0 s. Second holding pressure: 60MPa, lasting 1.5 s. After the holding pressure is completed, the gas in the pneumatic drive area is drawn back. At this time, the long valve needle (71) is quickly moved down to the bottom of the inverted triangle at the bottom of the nozzle part (34) by the reset of the high temperature spring (74). The gate is quickly closed and the melt is cut off. A small amount of melt remains at the tip of the nozzle part (34). At the same time, the partition cooling system is started. The cooling water temperature is maintained at 20℃ in the lens area, 25℃ in the edge area, and 30℃ in the snap-fit ​​area. Cooling takes 30-35 seconds to ensure that the product ejection temperature is ≤110℃. S5: 0.5 seconds before the end of cooling, start the electromagnetic vibrator (6) on the back of the upper moving mold (2) for 0.3 seconds to break the molecular adsorption force between the product and the mold surface; S6: When the injection molding machine opens the mold to the set position, the control system starts the air inflation mechanism at the lower fixed mold (1) to assist in demolding. 0.3MPa compressed air is introduced into the L-shaped air channel (131) for 0.5 seconds to form a uniform air film between the product buckle root and the mold surface. The robot arm grabs the product and completes the demolding operation. S7: After every 1000 consecutive production cycles, the control system starts the cleaning and purging program: compressed air enters the branch connection channel (111) through the external air intake channel (112) and flows into the nozzle part (34) through the air hole guided by the short valve needle (72), blowing the bottom residual melt to the waste collection port to complete the online self-cleaning.

Images