A two-color injection molding in-mold decoration molding process

Abstract

The application relates to the technical field and discloses a two-color injection molding in-mold decoration forming process, which comprises the following steps: S1, one-shot injection of a black material layer, black plastic is put into a hopper of an injection molding machine, and then the melted black plastic is injected into a cavity of a mold to form a black material layer; S2, mold rotation; S3, two-shot injection of a transparent layer, and an optical transmission texture IMD film piece is placed in the cavity of the mold, and then the melted transparent plastic is injected into the cavity of the mold to form a transparent layer; S4, cooling and solidification; and S5, demolding. Through the change of the glue injection position of the mold and the cooling structure of the low-temperature plastic part, the problem of poor light transmission caused by glue impact is solved, the PC+ABS plastic with a low melting point is first injected, then the PC plastic with a relatively high melting point is injected, the two-color IMD process is first promoted, single-machine stable continuous production is realized, the requirements of customers on light transmission and texture decoration are met, and the problems of low production efficiency, high defective rate and serious environmental pollution in the conventional process are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of IMD (In-Mold Decoration) technology, in particular to a two-color injection molding in-mold decoration forming process. BACKGROUND

[0002] Plastic products are widely used in the automotive, home appliance, communication, toy, and home furnishing industries. With the increasing demand for aesthetics and use, the texture decoration effect needs to be continuously improved. The emergence of IMD (In-Mold Decoration) technology solves this problem. IMD technology enables the surface of plastic products to have rich texture and gloss, while also having anti-scratch, anti-aging, and long service life characteristics.

[0003] With the increasing demand for product aesthetics, elements such as sound, light, and electricity are being used in products such as automobiles, home appliances, communications, toys, and home furnishings. Plastic products that combine light effects and appearance texture effects have emerged.

[0004] The earliest processing technology for such products is "IML injection + masking spray". First, an IML injection process is used to obtain a light-transmitting plastic product, and then a non-light-transmitting area is sprayed to prevent light transmission. This processing method is still widely used. However, this process is low in processing efficiency due to the characteristics of IML single-piece injection molding. The semi-finished product after molding needs to be transferred and subjected to secondary masking spray, baking, and other processes. The stability of the spray tooling and the preset theoretical coincidence degree cannot be completely consistent, resulting in high defect rates (qualified rate ≤ 85%) and serious environmental pollution in the spray painting process.

[0005] In addition, the conventional two-color injection molding process first injects PC with a high melting point, and then injects PC / ABS with a low melting point. The presence of an IMD film feeder prevents the cavity from rotating during production, making it impossible to combine two-color injection molding with IMD technology. Therefore, we need to propose a two-color injection molding in-mold decoration forming process. SUMMARY

[0006] The purpose of the present application is to provide a two-color injection molding in-mold decoration forming process. By changing the injection position of the mold and the cooling structure of the low-temperature plastic part, the problem of poor light transmission caused by injection is solved. PC+ABS plastic with a low melting point is first injected, and then PC plastic with a high melting point is injected, making it the first to introduce a two-color IMD process. This process enables stable and continuous production on a single machine, meets customer requirements for light transmission and texture decoration, and solves the problems of low production efficiency, high defect rate, and serious environmental pollution in conventional processes, thereby addressing the problems raised in the background technology.

[0007] To achieve the above purpose, the present application provides the following technical solution: a two-color injection molding in-mold decoration forming process, comprising the following steps:

[0008] S1, one injection of black material layer: put black plastic into the hopper of the injection molding machine, and then inject the molten black plastic into the cavity of the mold to form a black material layer;

[0009] S2, mold rotation: after the first injection is completed, the mold is opened and closed, and the black material layer is left on the back mold, and the mold is rotated 180° as a whole;

[0010] S3, two injections of transparent layer: put transparent plastic into the hopper of the injection molding machine, and place the light-transmitting texture IMD film sheet in the cavity of the mold, then inject the molten transparent plastic into the cavity of the mold to form a transparent layer, so that the transparent layer is tightly connected with the black material layer and covers the light-transmitting texture IMD film sheet;

[0011] S4, cooling and solidification: the heat inside the mold is taken away by the circulating cooling medium, so that the transparent layer and the black material layer are completely solidified to form the required product;

[0012] S5, demolding: after the transparent layer and the black material layer are completely solidified, the mold locking mechanism is released, and the product is pushed out of the mold by the ejection mechanism.

[0013] Preferably, before step S1, injection molding preparation is also needed, which includes:

[0014] Injection molding machine preparation: prepare a two-color injection molding machine, that is, a machine with two injection devices and two mold cavities, to inject different colored plastics;

[0015] Mold preparation: prepare a two-color injection molding mold and ensure that the mold has a suitable cavity and runner design to facilitate subsequent injection of black plastic and transparent plastic;

[0016] Injection molding material preparation: the injection molding materials include transparent plastic, black plastic, and light-transmitting texture IMD film sheet, among which the transparent plastic is PC plastic and the black plastic is PC+ABS plastic.

[0017] Preferably, before one injection of black material layer in step S1 and two injections of transparent layer in step S3, the injection temperature, injection pressure, injection speed, holding pressure time, holding pressure, and cooling time parameters of the injection molding machine are adjusted, and the running state of the injection molding machine and the filling condition of the mold are closely monitored during the process of injection molding black material layer to ensure that there is no bubble or material shortage.

[0018] Preferably, when one injection of black material layer is performed, the parameters of the injection molding machine are set as follows:

[0019] Injection temperature: 230-250℃;

[0020] Injection pressure: 40-120MPa;

[0021] Injection speed: 3-5g / s;

[0022] Dwell time: 18-25s;

[0023] Dwell pressure: 40%-50% of injection pressure;

[0024] Cooling time: 5-15s.

[0025] Preferably, when injecting the transparent layer, the injection machine is set as follows:

[0026] Injection temperature: 240-260℃;

[0027] Injection pressure: 50-130MPa;

[0028] Injection speed: 4-6g / s;

[0029] Dwell time: 20-30s;

[0030] Dwell pressure: 45%-55% of injection pressure;

[0031] Cooling time: 5-15s.

[0032] Preferably, in step S4, the two-color injection mold is equipped with a cooling system, the cooling system is provided with cooling liquid channels for flowing cooling water or cooling oil, the molten black plastic and transparent plastic are in direct contact with the cavity of the mold and transfer heat to the mold by heat conduction, and the cooling water or cooling oil flowing in the cooling liquid channels carries away the heat, so that the molten black plastic and transparent plastic are converted into solid state, so that the product has stable shape and performance.

[0033] Preferably, in step S5, when the product is taken out of the mold, in order to avoid damage or scratch of the product by the ejection mechanism, the ejection mechanism selects a top plate, and the size of the ejection force should be controlled when pushing out the product, so as to avoid damage of the mold or deformation of the product caused by large ejection force, and avoid failure to smoothly eject the product caused by small ejection force.

[0034] Preferably, the two-color injection mold comprises a fixed plate and a movable plate, the fixed plate is connected with a corinth column, the movable plate is movably installed on the corinth column, and two front molds are installed on the fixed plate, a rotating disc is installed on the movable plate, and two rear molds are installed on the rotating disc.

[0035] Preferably, the two injection barrels of the two-color injection machine are arranged in alignment with the two front molds, one of the front molds is provided with a mold transfer device, and the light-transmitting texture IMD film is installed on the mold transfer device.

[0036] Compared with the prior art, the beneficial effects of the present application are:

[0037] The present application solves the problem of poor light transmission caused by glue injection by changing the glue injection position of the mold and the cooling structure of the low-temperature plastic part, and realizes the injection of PC+ABS plastic with a low melting point first, and then the injection of PC plastic with a higher melting point, thus leading the double-color IMD process, realizing stable and continuous production of a single machine, meeting the requirements of customers on light transmission and texture decoration, and solving the problems of low production efficiency, high defect rate and serious environmental pollution in the conventional process. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The flow chart of the present application is shown in the figure.

[0039] Figure 2 The structure diagram of the double-color injection mold of the present application is shown in the figure. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0041] Please refer to Figures 1-2 The present application provides a technical solution: a double-color injection mold-in-decoration forming process, including the following steps:

[0042] S1, one injection of black material layer: the black plastic is put into the hopper of the injection molding machine, and then the molten black plastic is injected into the cavity of the mold to form a black material layer;

[0043] S2, mold rotation: after the first injection is completed, the mold is opened and closed, and the black material layer is left on the back mold, and the mold is rotated 180° as a whole; that is, the mold is rotated 180° together with the black material layer, so as to facilitate the positioning of the black material layer for the second injection and facilitate the addition of the transparent layer.

[0044] S3, two injections of transparent layer: the transparent plastic is put into the hopper of the injection molding machine, and the light-transmitting texture IMD film is placed in the cavity of the mold, and then the molten transparent plastic is injected into the cavity of the mold to form a transparent layer, so that the transparent layer is tightly connected with the black material layer and covers the light-transmitting texture IMD film;

[0045] The transparent layer is connected between the light-transmitting texture IMD film and the black material layer.

[0046] In steps S1 and S3, before the injection of the black layer and the transparent layer, the injection temperature, injection pressure, injection speed, holding time, holding pressure, and cooling time parameters of the injection molding machine are adjusted. During the injection of the black layer, the running state of the injection molding machine and the filling condition of the mold are closely monitored to ensure that there are no bubbles or material shortages.

[0047] By adjusting the parameters of the injection molding machine, it is ensured that the molten plastic can uniformly and completely fill the cavity of the mold.

[0048] When injecting the black layer, the parameters of the injection molding machine are set as follows:

[0049] Injection temperature: 230-250℃;

[0050] Injection pressure: 40-120MPa;

[0051] Injection speed: 3-5g / s;

[0052] Holding time: 18-25s;

[0053] Holding pressure: 40%-50% of the injection pressure;

[0054] Cooling time: 5-15s.

[0055] The selection of injection speed depends on the size and shape of the product. Faster injection speed can shorten the production cycle, but may increase internal stress. And the temperature of the mold should be controlled to ensure uniform flow and solidification of the plastic.

[0056] The injection of the black layer determines the basic shape and internal structure of the product.

[0057] When injecting the transparent layer, the parameters of the injection molding machine are set as follows:

[0058] Injection temperature: 240-260℃;

[0059] Injection pressure: 50-130MPa;

[0060] Injection speed: 4-6g / s;

[0061] Holding time: 20-30s;

[0062] Holding pressure: 45%-55% of the injection pressure;

[0063] Cooling time: 5-15s.

[0064] The injection pressure and speed of the transparent layer should be slightly higher than that of the black layer to ensure uniformity and glossiness. When injecting the transparent layer, the mold temperature may need to be slightly higher than when injecting the black layer to improve transparency and reduce internal stress. However, too high a mold temperature may cause material degradation or discoloration.

[0065] The purpose of injecting the transparent layer is:

[0066] Enhanced appearance: The transparent layer can provide a unique appearance effect for the product, such as high gloss, transparent or semi-transparent visual effect;

[0067] Functional enhancement: The transparent layer may be used to protect the internal decorative layer, such as text, patterns or colors, from wear and tear or contamination.

[0068] S4, cooling and solidification: the heat inside the mold is taken away by circulating cooling medium, making the transparent layer and black material completely solidified, forming the required product;

[0069] In step S4, the two-color injection mold is equipped with a cooling system, which is provided with a cooling liquid channel for the flow of cooling water or cooling oil. The molten black plastic and transparent plastic are in direct contact with the cavity of the mold, and the heat is transferred to the mold by heat conduction. The cooling water or cooling oil flowing in the cooling liquid channel takes away the heat, making the molten black plastic and transparent plastic change into solid state, so that the product has stable shape and performance.

[0070] During the cooling process, the flow rate of the cooling liquid also needs to be controlled, and the speed directly affects the quality and production efficiency of the product. Too fast cooling may increase the internal stress of the product, while too slow cooling may prolong the production cycle. The cooling speed of each part of the mold should be as consistent as possible to avoid deformation or warping of the product.

[0071] Optionally, the cooling system also includes a temperature monitoring device for real-time monitoring of the temperature changes of the mold and plastic, so as to adjust the production parameters in time.

[0072] S5, demolding: after the transparent layer and black material are completely solidified, the mold locking mechanism is released, and the product is pushed out of the mold by the ejection mechanism.

[0073] This process eliminates the spraying process, improves production efficiency, and reduces the scrap rate of semi-finished products.

[0074] The moving die part and the fixed die part of the mold are tightly attached together by the mold locking mechanism, ensuring that the molten plastic fills the cavity of the mold under high pressure.

[0075] In step S5, when the product is taken out of the mold, in order to avoid damage or scratching of the product by the ejection mechanism, the ejection mechanism selects a top plate, and the ejection force should also be controlled when pushing out the product, to avoid damage to the mold or deformation of the product caused by excessive ejection force, and to avoid the product being unable to be smoothly ejected due to insufficient ejection force.

[0076] The two parts of the mold should be kept synchronous during opening and closing to avoid damaging the mold or the product.

[0077] The mold closing process should be smooth to avoid generating excessive impact force or vibration, which helps to protect the mold and the product.

[0078] After demolding, the finished product is subjected to necessary post-processing such as deburring, polishing, painting, etc. to improve the appearance and texture of the product, and quality inspection is carried out to ensure that the product meets the design requirements and quality standards.

[0079] The light-transmitting textured IMD film is a film material with specific texture and light transmission, which is used in combination with plastic during injection molding to form a product surface with decorative effect. The light-transmitting textured IMD film contains design elements such as text and patterns, which are combined with plastic materials through the injection molding process to form an integrated decorative effect.

[0080] Before step S1, pre-injection preparation is also required, which includes:

[0081] Injection molding machine preparation: prepare a two-color injection molding machine, i.e. with two injection devices and two mold cavities, to inject different colored plastics respectively;

[0082] Mold preparation: prepare a two-color injection molding mold and ensure that the mold has appropriate cavity and runner design to facilitate subsequent injection of black plastic box and transparent plastic;

[0083] Injection molding material preparation: the injection molding materials include transparent plastic, black plastic, and light-transmitting textured IMD film, among which the transparent plastic is PC plastic and the black plastic is PC+ABS plastic.

[0084] PC plastic and PC+ABS plastic need to be heated to a molten state before injection molding.

[0085] PC plastic has excellent transparency, heat resistance and mechanical properties, making it suitable for products that require high transparency and durability. PC+ABS plastic combines the transparency of PC with the toughness and impact resistance of ABS, forming a material that is both transparent and has excellent mechanical properties. Combined with transparent PC plastic and light-transmitting textured IMD film, it forms a complex product with two-color effect and decorative texture.

[0086] For example, Figure 2As shown, the two-color injection mold includes a fixed plate and a movable plate, the fixed plate is connected with a corinthian column, the movable plate is movably installed on the corinthian column, and two front molds are installed on the fixed plate, a rotating disc is installed on the movable plate, and two rear molds are installed on the rotating disc.

[0087] The two injection barrels of the two-color injection molding machine are arranged in alignment with the two front molds, one of which is provided with a mold transfer device, and the light transmission texture IMD film is installed on the mold transfer device.

[0088] An infrared detector is also installed on the two-color injection mold to monitor and control the temperature of the mold, ensuring the stability of the injection molding process and the quality of the product; the infrared temperature measurement technology can non-contact irradiate on the surface of the injection mold, and through the detector receiving the infrared radiation energy emitted by the mold surface, the surface temperature is calculated and determined. This helps to understand and control the temperature state of the mold in real time, ensuring the smooth progress of the injection molding process.

[0089] The mold transfer device can ensure the accurate positioning of the IMD film during the injection molding process, prevent deviation or misplacement, and thus ensure the appearance and quality of the product.

[0090] Although embodiments of the present application have been shown and described, it will be understood by those having ordinary skill in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A two-color injection in-mold decoration molding process characterized by, The method comprises the following steps: S1, one injection molding black material layer: put black plastic into the hopper of the injection molding machine, then inject the molten black plastic into the cavity of the mold to form a black material layer; S2, mold rotation: after the first injection is completed, the mold is opened and closed, and the black material layer is left on the back mold, and the mold is rotated 180° as a whole; S3, two injection of transparent layer: put transparent plastic into the hopper of the injection molding machine, and place the light-transmitting texture IMD film sheet in the cavity of the mold, then inject the molten transparent plastic into the cavity of the mold to form a transparent layer, so that the transparent layer is tightly connected with the black material layer and covers the light-transmitting texture IMD film sheet; S4, cooling and solidification: the heat inside the mold is taken away by the circulating cooling medium, so that the transparent layer and the black material layer are completely solidified to form the required product; S5, demolding: after the transparent layer and the black material layer are completely solidified, the mold locking mechanism is released, and the product is pushed out of the mold by the ejection mechanism, In steps S1 and S3, before one injection molding black material layer and two injection of transparent layer, the injection temperature, injection pressure, injection speed, holding time, holding pressure, cooling time parameters of the injection molding machine are adjusted, and the running state of the injection molding machine and the filling condition of the mold are closely monitored during the process of injection molding black material layer, to ensure that there is no bubble and lack of material, When one injection molding black material layer, the parameters of the injection molding machine are set as follows: injection temperature: 230-250℃; injection pressure: 40-120MPa; injection speed: 3-5g / s; holding time: 18-25s; holding pressure: 40%-50% of the injection pressure; cooling time: 5-15s, When two injection of transparent layer, the parameters of the injection molding machine are set as follows: injection temperature: 240-260℃; injection pressure: 50-130MPa; injection speed: 4-6g / s; holding time: 20-30s; holding pressure: 45%-55% of the injection pressure; cooling time: 5-15s.

2. A two-shot in-mold decoration forming process according to claim 1, characterized in that: Before step S1, injection preparation is also needed, which includes: Injection machine preparation: prepare a two-color injection molding machine, that is, have two injection devices and two mold cavities to inject different colored plastics; Mold preparation: prepare a two-color injection molding mold and ensure that the mold has a suitable cavity and runner design to facilitate subsequent injection of black plastic and transparent plastic; Injection material preparation: the injection materials include transparent plastic, black plastic, and light-transmitting texture IMD film sheet, among which, the transparent plastic is PC plastic, and the black plastic is PC+ABS plastic.

3. A two-shot in-mold decoration forming process according to claim 1, characterized in that: In step S4, the two-color injection molding mold is equipped with a cooling system, and the cooling system is provided with a cooling liquid channel for the flow of cooling water or cooling oil. The molten black plastic and transparent plastic are in direct contact with the cavity of the mold, and the heat is transferred to the mold by heat conduction. The cooling water or cooling oil flowing in the cooling liquid channel takes away the heat, so that the molten black plastic and transparent plastic are converted into solid state, and the product has stable shape and performance.

4. A two-shot in-mold decoration forming process according to claim 1, characterized in that: In step S5, in order to avoid the ejection mechanism damaging or scratching the product, the ejection mechanism selects the ejector plate, and the ejection force should be controlled when the product is pushed out, so as to avoid the mold damage or product deformation caused by large ejection force, and avoid the product not being smoothly ejected caused by small ejection force.

5. A two-shot in-mold decoration forming process according to claim 1, characterized in that: The double-color injection mold comprises a fixed plate and a movable plate, the fixed plate is connected with a Corin column, the movable plate is movably installed on the Corin column, two front molds are installed on the fixed plate, a rotating disc is installed on the movable plate, and two rear molds are installed on the rotating disc.

6. A two-shot in-mold decoration forming process according to claim 5, characterized in that: The two injection barrels of the double-color injection molding machine are arranged in alignment with the two front molds, one of the front molds is provided with a mold transfer device, and the light transmission texture IMD film is installed on the mold transfer device.

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