CN109624202B - Gas-assisted injection molding method for automobile roof handle - Google Patents
Gas-assisted injection molding method for automobile roof handle Download PDFInfo
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- CN109624202B CN109624202B CN201811221700.8A CN201811221700A CN109624202B CN 109624202 B CN109624202 B CN 109624202B CN 201811221700 A CN201811221700 A CN 201811221700A CN 109624202 B CN109624202 B CN 109624202B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/1703—Introducing an auxiliary fluid into the mould
- B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/76—Measuring, controlling or regulating
- B29C45/77—Measuring, controlling or regulating of velocity or pressure of moulding material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/76—Measuring, controlling or regulating
- B29C45/78—Measuring, controlling or regulating of temperature
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60N—SEATS SPECIALLY ADAPTED FOR VEHICLES; VEHICLE PASSENGER ACCOMMODATION NOT OTHERWISE PROVIDED FOR
- B60N3/00—Arrangements or adaptations of other passenger fittings, not otherwise provided for
- B60N3/02—Arrangements or adaptations of other passenger fittings, not otherwise provided for of hand grips or straps
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76494—Controlled parameter
- B29C2945/76498—Pressure
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76494—Controlled parameter
- B29C2945/76531—Temperature
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76494—Controlled parameter
- B29C2945/76551—Time
- B29C2945/76561—Time duration
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Transportation (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
Abstract
The invention belongs to the technical field of automobile parts, and particularly relates to a gas-assisted injection molding method for an automobile ceiling handle. The method comprises the following steps: (1) injecting the molten plastic into a mold cavity through 2 or more than 2 gates, and maintaining the pressure after the mold is full; (2) injecting inert gas into the molten plastic in the mold cavity through 2 or more than 2 gas inlets, wherein the pressure of the injected inert gas is greater than the pressure of injection molding and storage, and part of the molten plastic in the mold cavity flows back to the sprue to form a hollow state; (3) maintaining the pressure, cooling, opening the mold and taking out the product.
Description
Technical Field
The invention belongs to the technical field of automobile parts, and particularly relates to a gas-assisted injection molding method for an automobile ceiling handle.
Background
Gas-assisted injection molding (hereinafter "gas-assisted molding" or GAIM) has not been widely used commercially until the end of the last century as a relatively new polymer processing technology. Compared with the Conventional Injection Molding (CIM), the gas-assisted molding has the advantages of raw material saving, shortened molding period, reduced mold locking force, good dimensional stability of a workpiece and the like. In the gas-assisted molding process, high-pressure inert gas is generally used as penetrating gas to push and compress the polymer melt until the melt fills the whole mold cavity, then the melt is gradually cooled and solidified under the pressure maintaining effect of the gas, and when the temperature of a workpiece is reduced to the demolding temperature, the mold can be opened to take out the workpiece. The gas-assisted molding technology is more complex than the traditional injection molding technology in nature, on one hand, the gas-assisted molding technology needs to add a gas injection device on the traditional injection molding mold, the mold cost is increased, and the size and the position design of a gas nozzle need to be considered when designing the mold; on the other hand, gas-assisted forming requires consideration of more process parameters: such as gas delay time, gas injection pressure, and gas injection time.
In the following disclosed air-assisted molding method for automobile handles, such as a truck top handle air-assisted molding process disclosed in chinese patent application (CN 103802273a), and an air-assisted back-blowing handle process disclosed in chinese patent application (CN 103434083a) and a handle body thereof, a molten resin is injected into a mold cavity, then a compressed gas (mainly nitrogen) is introduced into a molten resin in the mold cavity through a special nozzle installed on a machine barrel or an air needle in the mold, and the gas is rapidly discharged after pressure maintaining and cooling. With these known techniques, there are various degrees of "gas finger" defects in production: the bubbles pass through the thin-walled region outside the product's airway, forming the "finger-mounted" branch. Severe "gas fingers" can reduce the strength of the plastic article, cause failure of the gas-assisted molding technique, or fail to take advantage of the gas-assisted molding technique. In addition, if the technological parameters of the gas-assisted molding process are not reasonably regulated and controlled, the gas-assisted molding process is easy to generate melt marks, the appearance image of an injection molding part is influenced, and the mechanical property is also influenced to a certain extent.
Disclosure of Invention
The invention provides a novel air-assisted molding method aiming at the problems of the existing air-assisted molding technology of an automobile ceiling handle.
In order to achieve the above purpose of the invention, the following technical scheme is adopted: a gas-assisted injection molding method of an automobile ceiling handle comprises the following steps:
(1) injecting the molten plastic into a mold cavity through 2 or more than 2 gates, and maintaining the pressure after the mold is full;
(2) injecting inert gas into the molten plastic in the mold cavity through 2 or more than 2 gas inlets, wherein the pressure of the injected inert gas is greater than the pressure of injection molding and storage, and part of the molten plastic in the mold cavity flows back to the sprue to form a hollow state;
(3) maintaining the pressure, cooling, opening the mold and taking out the product.
Preferably, the dwell time in step (1) is from 1 to 5 s.
Preferably, the temperature of the plastic melt is 210-250 ℃ and the temperature of the mold is 50-70 ℃ during injection molding.
Preferably, the number of the air inlets is 2, the air inlets are respectively arranged at the left end and the right end of the die and used for vertically feeding air.
Preferably, the pressure of the injected inert gas is 5-20MPa, the temperature is lower than 25 ℃, and the gas injection time is 2-5 s.
Preferably, the inert gas is nitrogen or carbon dioxide or a mixture of nitrogen and carbon dioxide.
Preferably, the dwell time in step (3) is from 5 to 10 s.
Preferably, the cooling is carried out in liquid nitrogen at-100 to-180 ℃.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention adopts 2 or more than 2 gates, improves the injection molding efficiency, makes the flow direction of the melt disordered or disordered, and further inhibits the warping phenomenon of the plastic product;
(2) the invention adopts the plurality of air inlets to oppositely intake air, eliminates the welding marks generated by the confluence of a plurality of sprue melts, and reduces the air finger defects, thereby improving the performance of the product;
(3) in the invention, the inert gas pushes the melt to flow, and the redundant melt flows back to the sprue, so that the method is favorable for eliminating the welding marks and reducing the internal stress of the melt compared with the traditional gas-assisted forming method;
(4) in the invention, after the pressure is maintained by introducing gas into the die, the die is rapidly cooled, so that the residual internal stress of the product after demolding can be reduced, the buckling deformation is reduced, and the product strength is improved;
in general, the novel air-assisted forming method provided by the invention is beneficial to reducing the bad defects existing in the automobile ceiling handle injection molding part, improving the appearance image of the injection molding part and simultaneously enhancing the mechanical property of the injection molding part.
Drawings
FIG. 1 shows an example of a gas inlet and a gate in a gas-assisted molding process according to the present invention.
Detailed Description
The technical solution of the present invention is further described below by means of specific embodiments and accompanying drawings. The raw materials used in the examples of the present invention are those commonly used in the art, and the methods used in the examples are those conventional in the art, unless otherwise specified.
In one embodiment of the invention, the gas-assisted injection molding method of the automobile ceiling handle comprises the following steps:
(1) injecting the molten plastic into a mold cavity through 2 or more than 2 gates, and maintaining the pressure after the mold is full;
(2) injecting inert gas into the molten plastic in the mold cavity through 2 or more than 2 gas inlets, wherein the pressure of the injected inert gas is greater than the pressure of injection molding and storage, and part of the molten plastic in the mold cavity flows back to the sprue to form a hollow state;
(3) maintaining the pressure, cooling, opening the mold and taking out the product.
At present, most of existing automobile ceiling handle molds adopt a single pouring gate structure and a single-layer pouring mode, the speed of the pouring mode is low, the time for filling a cavity with a melt is long, the temperature of the melt is reduced, and the flow of subsequent gas in the melt is influenced; in addition, the single-gate injection molded product is easy to warp due to the fact that the melt flow time is too long, and the internal stress caused by flow and shrinkage is large. Adopt 2 or more than 2 runners, through the runner quantity that increases the mould, increase simultaneously along the runner of equidirectional, through pouring into the mould with melting plastics from different directions and a plurality of runners simultaneously like this, can change melting plastics's flow orientation effectively for the fuse-element flow direction can be more disorderly or unordered, and then suppresses the production of warpage phenomenon. However, the possibility of generating weld marks is greatly increased when the molten plastic enters the mold cavity through a plurality of gates. Therefore, the flow rate of the melt at the plurality of gates needs to be reasonably controlled, the melt at the plurality of gates is simultaneously filled in the die cavity through debugging, and the generation of welding marks is reduced.
The gas is fed in through the plurality of gas inlets in opposite directions, and the inert gas pushes the melt to flow, so that the process is proved to be capable of eliminating weld marks generated by the confluence of a plurality of sprue melts, and the performance of the product is improved; and the air inlet process can be shortened by the air inlet of the plurality of air inlets, and the air finger defect is reduced. The inert gas pushes the melt to flow, and the redundant melt flows back to the sprue, so that compared with the traditional gas-assisted molding: the melt fills part of the mould, and the rest part of the mould is filled with the melt pushed by gas, so that the melt welding mark can be eliminated, and the internal stress of the melt can be reduced.
The dwell time in the step (1) is 1-5 s.
And after injection molding, the pressure is maintained for a period of time, and the internal stress of the product can be reduced by proper pressure maintaining time. And (2) with the increase of the pressure maintaining time in the step (1), the melt temperature is lower and lower, the thickness of the cooling layer is increased, so that the transverse filling resistance of the gas is increased, the gas longitudinally extends along the center of the gas channel along the principle of minimum resistance, and the gas finger effect is smaller and smaller. However, in the gas-assisted injection molding technology, the injection and pressure maintaining time cannot be too long, otherwise, after the melt in the gas channel of the product is solidified, gas is difficult to inject, and the due effect of gas-assisted molding cannot be achieved. And the internal stress of the product can be increased by maintaining the pressure for a long time. The melt gap generated by cooling and shrinking of the melt in the pressure maintaining process can be filled by pushing the melt to flow by the subsequently injected inert gas.
During injection molding, the temperature of the plastic melt is 210-250 ℃, and the temperature of the mold is 50-70 ℃.
The melt temperature and the die temperature have certain influence on the generation of gas finger defects in gas-assisted molding, the melt temperature is too high, the melt viscosity is reduced, and gas can easily overcome the melt resistance and enter a thin-wall area to generate gas fingers; the temperature of the mold is too high, the phenomenon of gas finger is easy to generate by the same principle, the temperature of the mold is too low, the temperature of the melt is rapidly reduced after the melt is injected into the mold, and inert gas is difficult to enter the melt.
The number of the air inlets is 2, the air inlets are respectively arranged at the left end and the right end of the die and used for vertically feeding air.
The air inlets are arranged at the left end and the right end of the mold and used for oppositely introducing air to push the fluid to move in opposite directions.
The pressure of the injected inert gas is 5-20MPa, the temperature is lower than 25 ℃, and the gas injection time is 2-5 s.
The phenomenon that gas penetrates into peripheral melt is increased along with the increase of the gas pressure, so that the gas pressure is increased to generally increase gas finger defects, but the pressure of injected inert gas needs to be higher than the melt pressure, so that the gas can push the melt to flow, the gas pressure needs to be higher than the injection storage pressure, the gas can push part of melt in a mold to flow back to a middle gate, and the melt is in a hollow state. When the number of the air inlets is 2 and the air inlets are respectively arranged at the left end and the right end of the mold, the pressure and the flow rate of the air inlets at the left end and the right end are controlled according to the position of the middle backflow gate, so that the melts at the left side and the right side simultaneously flow back to the middle backflow gate.
The temperature of the injected inert gas is lower than 25 ℃, the lower the gas temperature is, the higher the cooling speed of the gas channel and the surrounding melt is, a cooling layer is formed at the periphery of the gas channel, and the diffusion of the gas to the depth direction is inhibited, so that the effect of reducing the gas finger defects is achieved. Generally, the lower the temperature the better the effect.
The inert gas is nitrogen or carbon dioxide or a mixture of nitrogen and carbon dioxide.
And (4) keeping the pressure for 5-10s in the step (3). And maintaining the pressure for 5-10s by using gas to eliminate the internal stress of the product.
The cooling in the step (3) is carried out by placing the mixture in liquid nitrogen at the temperature of between 100 ℃ below zero and 180 ℃ below zero for cooling. After the pressure is maintained by introducing gas into the mould, the mould is placed in liquid nitrogen at the temperature of-100 to-180 ℃ for cooling, and the rapid cooling of the mould can reduce the residual internal stress of the product after the product is demoulded, reduce the warping deformation and improve the strength of the product; the defects of welding marks, dents, flow marks, ripples and the like on the surface of the injection molding product are eliminated, the glossiness and the smoothness of the surface of the injection molding product are improved, and the quality of the injection molding product is more perfect.
The following describes the air-assisted molding method of the vehicle roof handle according to the present invention in detail with reference to the example of fig. 1. In the figure, 1, 2 and 3 represent 3 gates, and the second gate (2) is arranged at the left end of the handle mold, which is approximately intersected by a vertical plane and a horizontal plane, but of course, the gate can be arranged at the right end. The first pouring gate (1) and the third pouring gate (3) adopt moon-shaped pouring gates, the moon-shaped pouring gates are in the structural form of arc-shaped submarine pouring gates, molten plastics are directly injected into a parting surface, and the injected molten plastics flow upwards and horizontally. The second pouring gate (2) adopts a straight pouring gate, the molten plastic directly enters the mold cavity from the large end of the main runner, and the injected molten plastic flows at a high speed. The melt flow rate of the 3 gates needs to be reasonably controlled, the flow channels of the first gate (1) and the third gate (3) are small, and the flow rate is slightly slow. The runner of second runner (2) is big, and the velocity of flow is very fast, makes the fuse-element of 3 runners be full of the mould die cavity simultaneously through control runner fuse-element velocity of flow, reduces the production of weld mark.
4 and 5 in the figure represent 2 air inlets, and a first air inlet (4) and a second air inlet (5) are respectively arranged at the left end and the right end of the handle mould and vertically feed air.
And injecting the molten plastic into a mold cavity through the first gate (1), the second gate (2) and the third gate (3), and maintaining the pressure for 1-5s after the mold is fully injected. Closing the first sprue (1) and the third sprue (3), then opening the first air inlet (4) and the second air inlet (5), injecting inert gas into the cavity melt through the first air inlet (4) and the second air inlet (5) to push fluid to flow, enabling redundant fluid to flow back to the injection molding system from the second sprue (2), enabling the plastic melt in the mold to be in a hollow state, maintaining the pressure for 5-10s, then placing the mold in liquid nitrogen at the temperature of-100 to-180 ℃ for cooling, opening the mold, and taking out a product.
In the following examples, the plastic used is polypropylene resin, under the designation K8303.
Example 1
As shown in FIG. 1, 3 gates and 2 air inlets provided in this embodiment inject molten polypropylene into a mold cavity through a first gate (1), a second gate (2) and a third gate (3), the melt temperature is 230 ℃, the mold temperature is 60 ℃, and the mold is kept for 2s after the mold is fully injected. Closing the first pouring gate (1) and the third pouring gate (3), then opening the first air inlet (4) and the second air inlet (5), injecting nitrogen into the cavity melt through the first air inlet (4) and the second air inlet (5), adjusting the pressure of the nitrogen in the second air inlet (5) to be 8MPa, the pressure of the nitrogen in the first air inlet (4) to be 5MPa, the temperature of the nitrogen in the two air inlets to be 0 ℃, injecting gas for 3s, pushing the fluid to flow by the nitrogen, enabling the redundant fluid to flow back to the injection molding system from the second pouring gate (2), enabling the plastic melt in the mold to be in a hollow state, maintaining the pressure for 6s, then placing the mold in liquid nitrogen at the temperature of-180 ℃ for cooling, opening the mold, and taking out a product.
Example 2
As shown in FIG. 1, 3 gates and 2 air inlets provided in this embodiment are used, molten polypropylene is injected into a mold cavity through a first gate (1), a second gate (2) and a third gate (3), the melt temperature is 230 ℃, the mold temperature is 60 ℃, and the pressure is maintained for 6s after the mold is fully injected. Closing the first pouring gate (1) and the third pouring gate (3), then opening the first air inlet (4) and the second air inlet (5), injecting nitrogen into the cavity melt through the first air inlet (4) and the second air inlet (5), adjusting the pressure of the nitrogen in the second air inlet (5) to be 8MPa, the pressure of the nitrogen in the first air inlet (4) to be 5MPa, the temperature of the nitrogen in the two air inlets to be 0 ℃, injecting gas for 3s, pushing the fluid to flow by the nitrogen, enabling the redundant fluid to flow back to the injection molding system from the second pouring gate (2), enabling the plastic melt in the mold to be in a hollow state, maintaining the pressure for 6s, then placing the mold in liquid nitrogen at the temperature of-180 ℃ for cooling, opening the mold, and taking out a product.
Example 3
As shown in FIG. 1, 3 gates and 2 air inlets provided in this embodiment inject molten polypropylene into a mold cavity through a first gate (1), a second gate (2) and a third gate (3), the melt temperature is 230 ℃, the mold temperature is 60 ℃, and the mold is kept for 2s after the mold is fully injected. Closing the first pouring gate (1) and the third pouring gate (3), then opening the first air inlet (4) and the second air inlet (5), injecting nitrogen into the cavity melt through the first air inlet (4) and the second air inlet (5), adjusting the pressure of the nitrogen in the second air inlet (5) to be 8MPa, the pressure of the nitrogen in the first air inlet (4) to be 5MPa, the temperature of the nitrogen in the two air inlets to be 30 ℃, injecting gas for 3s, pushing the fluid to flow by the nitrogen, enabling the redundant fluid to flow back to the injection molding system from the second pouring gate (2), enabling the plastic melt in the mold to be in a hollow state, maintaining the pressure for 6s, then placing the mold in liquid nitrogen at-180 ℃ for cooling, opening the mold, and taking out a product.
Example 4
As shown in FIG. 1, 3 gates and 2 air inlets provided in this embodiment inject molten polypropylene into a mold cavity through a first gate (1), a second gate (2) and a third gate (3), the melt temperature is 210 ℃, the mold temperature is 50 ℃, and the mold is kept for 3s after the mold is fully injected. Closing the first pouring gate (1) and the third pouring gate (3), then opening the first air inlet (4) and the second air inlet (5), injecting nitrogen into the cavity melt through the first air inlet (4) and the second air inlet (5), adjusting the pressure of the nitrogen in the second air inlet (5) to be 9MPa, the pressure of the nitrogen in the first air inlet (4) to be 6MPa, the temperature of the nitrogen in the two air inlets to be 10 ℃, injecting gas for 2s, pushing the fluid to flow by the nitrogen, enabling the redundant fluid to flow back to the injection molding system from the second pouring gate (2), enabling the plastic melt in the mold to be in a hollow state, maintaining the pressure for 7s, then placing the mold in liquid nitrogen at the temperature of-180 ℃ for cooling, opening the mold, and taking out a product.
Example 5
As shown in FIG. 1, 3 gates and 2 air inlets provided in this embodiment inject molten polypropylene into a mold cavity through a first gate (1), a second gate (2) and a third gate (3), the melt temperature is 240 ℃, the mold temperature is 70 ℃, and the mold is kept for 2s after the mold is fully injected. Closing the first pouring gate (1) and the third pouring gate (3), then opening the first air inlet (4) and the second air inlet (5), injecting nitrogen into the cavity melt through the first air inlet (4) and the second air inlet (5), adjusting the pressure of the nitrogen in the second air inlet (5) to be 10MPa, the pressure of the nitrogen in the first air inlet (4) to be 7MPa, the temperature of the nitrogen in the two air inlets to be 2 ℃, injecting gas for 3s, pushing the fluid to flow by the nitrogen, enabling the redundant fluid to flow back to the injection molding system from the second pouring gate (2), enabling the plastic melt in the mold to be in a hollow state, maintaining the pressure for 8s, then placing the mold in liquid nitrogen at the temperature of-180 ℃ for cooling, opening the mold, and taking out a product.
Comparative example 1
Comparative example 1 is different from example 1 in that comparative example 1 has only one second gate (2), and the first gate (1) and the third gate (3) are not provided, and the others are the same as example 1.
Comparative example 2
Comparative example 2 differs from example 1 in that comparative example 2 has only one first inlet (4) and no second inlet (5), the second gate (2) is placed at the position of the original second inlet (5), and the excess melt is returned back to the injection system through the new second gate (2), otherwise the same as example 1.
Comparative example 3
Comparative example 3 is different from example 1 in that the mold of comparative example 3 is cooled by cold air at 0 c, and the other is the same as example 1.
The pull handles of examples 1-5 and comparative examples 1-2 were characterized for finger defects in the article by calculating the maximum finger size and maximum finger amplitude; the notched impact strength and tensile strength of the grips of examples 1-5 and comparative examples 1-2 were also measured and the results are detailed in Table 1.
TABLE 1
The gas finger level is characterized by the maximum gas finger size and maximum gas finger amplitude, as shown in table 1, the gas finger defect is the smallest for example 1, followed by examples 5 and 4, and comparative examples 1-3 have larger gas finger defects due to lack of the necessary technical features of the present invention. The gas finger defect is correlated with a reduction in the performance of the plastic article, so that the notched impact strength and tensile strength of comparative examples 1 to 3 are significantly lower than those of the examples.
In addition, the technical scope of the invention is not exhaustive, and new technical solutions formed by equivalent replacement of single or multiple technical features in the embodiment technical solutions are also within the scope of the invention; meanwhile, in all the embodiments of the invention, which are listed or not listed, each parameter in the same embodiment only represents one example of the technical scheme.
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
Claims (4)
1. A gas-assisted injection molding method of an automobile ceiling handle is characterized by comprising the following steps:
injecting the molten plastic into a mold cavity through a first pouring gate (1), a second pouring gate (2) and a third pouring gate (3), and maintaining the pressure for 1-5s after the mold is fully injected; closing the first sprue (1) and the third sprue (3), then opening the first air inlet (4) and the second air inlet (5), injecting inert gas into molten plastic in a mold cavity through the first air inlet (4) and the second air inlet (5), wherein the pressure of the injected inert gas is greater than the injection molding storage pressure, pushing fluid to flow by the inert gas, enabling redundant fluid to flow back to an injection molding system from the second sprue (2), keeping the pressure of the plastic melt in the mold for 5-10s, then placing the mold in liquid nitrogen at the temperature of-100 to-180 ℃ for cooling, opening the mold, and taking out a product;
the second gate (2) is a straight gate and is arranged at the left end or the right end where the vertical surface and the horizontal surface of the mold are intersected; the first pouring gate (1) and the third pouring gate (3) are moon-shaped pouring gates and are respectively arranged at the left end and the right end of the second pouring gate (2);
the first air inlet (4) and the second air inlet (5) are respectively arranged at the left end and the right end of the die and used for vertically feeding air.
2. The gas-assisted injection molding method of claim 1, wherein the temperature of the plastic melt is 210-250 ℃ and the temperature of the mold is 50-70 ℃ during injection molding.
3. The gas-assisted injection molding method according to claim 1, wherein the inert gas is injected under a pressure of 5 to 20MPa at a temperature of less than 25 ℃ for a gas injection time of 2 to 5 seconds.
4. A gas-assisted injection molding process according to claim 1 wherein the inert gas is nitrogen or carbon dioxide or a mixture of nitrogen and carbon dioxide.
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|---|---|---|---|---|
| CN111300727B (en) * | 2020-02-25 | 2022-04-05 | 金发科技股份有限公司 | Injection molding method and system for polymer |
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| CN109624202A (en) | 2019-04-16 |
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Application publication date: 20190416 Assignee: Ningbo yako vehicle parts Co.,Ltd. Assignor: Ningbo Shuaitelong Group Co.,Ltd. Contract record no.: X2021330000245 Denomination of invention: Gas assisted injection molding method for automobile ceiling handle Granted publication date: 20210601 License type: Common License Record date: 20210904 |
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