Injection molding method and mold for plastic products

Abstract

The present invention belongs to the field of plastic molding technology, and particularly relates to an injection molding method and mold for plastic products. The injection molding method for plastic products of the present invention divides the molding cavity into the first cavity to the Nth cavity along the first direction, and the second cavity to the Nth cavity all include a connecting chamber and a main chamber, and injection molding is performed into the main chamber of the Mth cavity and the connecting chamber of the M+1th cavity, and the above steps are repeated until all the molding cavities are injection molded. Since the core-pulling slider is not easy to deform during the entire injection molding process, the quality of the obtained plastic product is better and the yield rate is higher. In the injection molding mold for plastic products of the present invention, the second mold assembly includes a main mold and a connecting mold, and the second mold assembly has multiple injection molding positions. Injection molding is performed in multiple injection molding positions in sequence, and the desired plastic products can be injection molded, and the obtained plastic products have better quality and a higher yield rate.

Description

Technical Field

[0001] The invention belongs to the technical field of plastic molding, and in particular relates to an injection molding method and a mold for a plastic product. Background Art

[0002] Plastic injection molding is a common molding method in the production of thermoplastic plastic parts. This molding method is to inject molten material into the mold cavity, wait for the molten material to cool and solidify, and then form the desired product.

[0003] When the molded product is a long hollow structure, a core-pulling slider will be placed in the mold, and the molten material injected into the mold will cover the outside of the core-pulling slider. After the molten material cools down and solidifies, the core-pulling grinding rod is pulled out to form a hollow structure. However, the core-pulling slider is usually a slender structure. When the molten material is injected into the mold, the high temperature and high pressure brought by the molten material may cause the core-pulling slider to deform. Therefore, after the molten material solidifies, the finished product is prone to glue bias, resulting in unequal tube wall thickness of the finished product, which makes the structural strength of the finished product defective. When the degree of deformation of the core-pulling slider is too large, it may even cause holes on the surface of the finished product, making it a defective product.

[0004] In the related technology, for example, Chinese patent CN111660511B discloses an injection molding method, in which a sleeve is set on the core-pulling slider, and the sleeve is used to support the core-pulling slider to improve the structural strength of the core-pulling slider, so as to reduce the deformation effect of high temperature and high pressure on the core-pulling slider.

[0005] However, in the above injection molding method, the capsule will melt after absorbing the heat of the molten material, resulting in poor support effect of the capsule on the core-pulling slider, which still leads to the problem of low product yield. Summary of the invention

[0006] Based on this, it is necessary to provide an injection molding method for plastic products to solve the problem of low yield in the injection molding method in the prior art due to deformation of the core pulling slider, and also provide an injection molding mold for plastic products to solve the problem of low yield in the injection molding mold in the prior art due to deformation of the core pulling slider.

[0007] The above purpose is achieved through the following technical solutions:

[0008] A method for injection molding of a plastic product comprises the following steps:

[0009] S10: dividing the molding cavity into a first cavity to an Nth cavity along a first direction, wherein the second cavity to the Nth cavity each include a connecting cavity and a main cavity, and N≥3;

[0010] S20: injection molding into the connecting chamber of the first cavity and the second cavity;

[0011] S30: injection molding into the main chamber of the Mth cavity and the connecting chamber of the M+1th cavity, wherein M<N;

[0012] S40: Repeat step S30 until the molding cavity is completely injected.

[0013] Further, in step S10, the molding cavity is evenly divided into a first cavity to an Nth cavity along a first direction.

[0014] Further, in step S30, the connection chamber of the M+1th cavity is heated.

[0015] Further, in the second cavity to the Nth cavity, the connecting chamber is arranged in the middle of the main chamber.

[0016] Further, in step S20, the first cavity is cooled, and in step S30, the main chamber of the Mth cavity is cooled.

[0017] The beneficial effect of the injection molding method of the plastic product of the present invention is as follows: during injection molding, molten material is first injected into the connecting chamber of the first cavity and the second cavity, and the first plastic segment is obtained after the molten material is molded, which can support the core-pulling slider. When executing step S30, molten plastic is injected into the main chamber of the Mth cavity and the connecting chamber of the M+1th cavity. Due to the support of the M-1th plastic segment in the connecting chamber of the M-1th cavity and the Mth cavity, when executing step S30, the newly injected molten plastic is not easy to deform the core-pulling slider, and step S30 is repeated until all the molding cavities are injection molded. Since the core-pulling slider is not easy to deform during the entire injection molding process, the quality of the obtained plastic product is better and the yield rate is higher.

[0018] A plastic product injection molding mold comprises a first mold assembly, a second mold assembly, a core-pulling slider and a driving mechanism. The core-pulling slider is fixedly connected to the first mold assembly and passes through the second mold assembly. The second mold assembly comprises a main mold and a connecting mold. Both the main mold and the connecting mold have an inner cavity. In a first direction, the connecting mold is located in front of the main mold. The driving mechanism can drive the second mold assembly to move along the first direction and enable the second mold assembly to have multiple injection positions. Injection molding is performed at multiple injection positions in sequence along the first direction to inject desired plastic products.

[0019] Furthermore, the second mold assembly includes a heating element for heating the inner cavity of the connecting mold.

[0020] Furthermore, the heating element is arranged at the bottom of the inner cavity connected to the mold.

[0021] Further, a projection of the connecting mold on the main mold along a direction opposite to the first direction is located in the middle of the main mold.

[0022] Furthermore, the driving mechanism is an electric push rod.

[0023] The beneficial effect of the injection molding mold for plastic products of the present invention is that during injection molding, the second mold component is first located at the first injection molding position, molten plastic is injected, a portion of the core-pulling slider close to the first mold component is submerged by the molten plastic, and after the first plastic segment is injected, the second mold component is driven by the driving mechanism to move along the first direction to the second injection molding position, and then the molten plastic is injected. Since the first plastic segment after molding can support the core-pulling slider, the newly injected molten plastic is not easy to deform the core-pulling slider, and this is repeated until the desired plastic product is injected. Since the core-pulling slider is not easy to deform during the entire injection molding process, the quality of the obtained plastic product is good and the yield rate is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flowchart of the injection molding method of the plastic product of the present invention;

[0025] Figure 2 It is a structural schematic diagram of the injection molding mold of the plastic product of the present invention;

[0026] Figure 3 for Figure 2 An injection molding mold of a plastic product and an exploded view of a first plastic section;

[0027] Figure 4 for Figure 2 A first state diagram of an injection molding mold for a plastic product;

[0028] Figure 5 for Figure 2 A second state diagram of the injection molding mold of the plastic product;

[0029] Figure 6 for Figure 2 A third state diagram of the injection molding mold of the plastic product in FIG.

[0030] Figure 7 for Figure 2 FIG. 4 is a diagram of the fourth state of the injection molding mold for a plastic product.

[0031] in:

[0032] 100, first mold assembly; 110, support plate; 120, molding plate; 200, core-pulling slider; 310, main mold; 312, injection port; 320, connecting mold; 322, connecting ring groove; 326, cylindrical cavity; 330, heating element; 342, liquid inlet; 344, cooling pipeline; 346, liquid outlet; 400, first plastic section; 410, connecting boss. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings). In the description of the present invention, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0035] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0036] Refer to the following Figure 1 , describing the injection molding method of a plastic product provided by an embodiment of the first aspect of the present invention:

[0037] The injection molding method of the plastic product of this embodiment comprises the following steps:

[0038] S10: dividing the molding cavity into a first cavity to an Nth cavity along a first direction, wherein the second cavity to the Nth cavity each include a connecting cavity and a main cavity, and N≥3;

[0039] S20: injection molding into the connecting chamber of the first cavity and the second cavity;

[0040] S30: injection molding into the main chamber of the Mth cavity and the connecting chamber of the M+1th cavity, wherein M<N;

[0041] S40: Repeat step S30 until the molding cavity is completely injected.

[0042] The injection molding method of plastic products in this embodiment is used to cast plastic products with long strips and hollow structures. The technical concept is to mold the plastic products through multiple castings, and the product module molded each time can support the core-pulling slider during the next casting, so that the core-pulling slider is not easily deformed during the casting process.

[0043] Among them, in step S10, the molding cavity refers to a cavity required for molding a plastic product through a single injection molding in an imaginary manner, and the imaginary molding cavity is used as a segmentation object, and it is segmented into the first cavity to the Nth cavity. Next, in steps S20 and S30, the first cavity to the Nth cavity are formed in sequence, and each formed cavity is injection molded to inject a plastic segment, corresponding to the first cavity to the Nth cavity, and each plastic segment is correspondingly named as the first to the Nth plastic segment. The first direction refers to the direction from the bottom to the top of the plastic product.

[0044] In order to connect the plastic segments to finally form the desired plastic product, the second cavity to the Nth cavity all include a connecting cavity and a main cavity. During injection molding, the molten material is first injected into the connecting cavity of the first cavity and the second cavity. After the molten material is molded, the first plastic segment is obtained, which can support the core-pulling slider. When executing step S30, the molten plastic is injected into the main cavity of the Mth cavity and the connecting cavity of the M+1th cavity. Due to the support of the M-1th plastic segment in the connecting cavity of the M-1th cavity and the Mth cavity, when executing step S30, the newly injected molten plastic is not easy to deform the core-pulling slider. Repeat step S30 until all the molding cavities are injection molded. Since the core-pulling slider is not easy to deform during the entire injection molding process, the quality of the obtained plastic product is better and the yield rate is higher.

[0045] Wherein, in step S30, M is less than N, and M is a numerical value that increases successively (i.e., 2, 3, 4, etc.), so that each plastic segment that is injected can be connected into the desired plastic product. When M is equal to N-1, injection molding is performed into the main chamber of the N-1th cavity and the connecting chamber of the Nth cavity, and the injection molding process is completed, and there is no need to inject the main chamber of the Nth cavity again. After the injection molding is completed, the plastic protrusion formed in the connecting chamber of the Nth cavity can be removed as needed.

[0046] In this embodiment, N may be 3, that is, step S30 is performed only once. In other embodiments, N may be 4, that is, step S30 needs to be performed twice.

[0047] In one embodiment, in step S10, the molding cavity is evenly divided into the first cavity to the Nth cavity along the first direction. Evenly dividing the molding cavity can make the length of each plastic segment more uniform, which can not only improve the quality of the plastic product, but also make the pressure of the molten plastic on the molding slider more uniform each time, so that the core-pulling slider is less likely to deform, and it is also convenient to form other cavities in sequence with equal spacing in the subsequent sequence.

[0048] In one embodiment, in step S30, the connecting chamber of the M+1th cavity is heated. Heating the connecting chamber can reduce the cooling rate of the molten plastic in the connecting chamber, so that the portion of the molded Mth plastic segment located in the connecting chamber is at a higher temperature. When the next step S30 is performed, the newly injected molten plastic can be better combined with the plastic segment molded last time, thereby improving the connection strength between the plastic segments, so that the molded plastic product has better integrity.

[0049] In one embodiment, in the second cavity to the Nth cavity, the connecting cavity is arranged in the middle of the main cavity. The connecting cavity is arranged in the middle of the main cavity, so that the connection part of two adjacent plastic segments is also located in the middle, so that the connection strength between the two plastic segments can be higher, thereby improving the structural strength of the plastic product. In other embodiments, the connecting cavity can be arranged at a position deviated from the middle of the main cavity.

[0050] In one embodiment, in step S20, the first cavity is cooled, and in step S30, the main chamber of the Mth cavity is cooled. Cooling the main chambers of the first cavity and the Mth cavity can accelerate the cooling speed of the molten plastic in the main chambers, thereby improving the injection molding efficiency. Specifically, the main chamber can be cooled by liquid cooling. In other embodiments, air cooling can also be used for cooling. The cost of air cooling is lower, but compared with air cooling, liquid cooling has higher cooling efficiency.

[0051] According to the following Figures 2 to 7 , describing the injection molding mold for a plastic product provided by an embodiment of the second aspect of the present invention:

[0052] The injection molding mold of the plastic product of this embodiment includes a first mold assembly 100, a second mold assembly, a core-pulling slider 200 and a driving mechanism. The core-pulling slider 200 is fixedly connected to the first mold assembly 100 and passes through the second mold assembly. The second mold assembly includes a main mold 310 and a connecting mold 320. The main mold 310 and the connecting mold 320 both have an inner cavity. In the first direction, the connecting mold 320 is located in front of the main mold 310. The driving mechanism can drive the second mold assembly to move along the first direction and make the second mold assembly have multiple injection positions. Injection molding is performed in the multiple injection positions in sequence along the first direction, and the desired plastic product can be injection molded. Specifically, the main mold 310 and the connecting mold 320 are both cylindrical, and an injection port 312 is provided on the main mold 310. The molten plastic is injected into the inner cavity of the main mold 310 from the injection port 312.

[0053] In this embodiment, the first direction refers to the direction from the bottom to the top of the plastic product. Before the required plastic product is injection molded, the positions of each injection molding position are first determined. Specifically, it is first assumed that the cavity required for the plastic product can be molded by one injection molding. The imaginary molding cavity is used as the segmentation object and is divided into the first cavity to the Nth cavity (N≥3). The second cavity to the Nth cavity all include a main cavity and a connecting cavity. The positions of the N cavities correspond one-to-one to the injection molding positions of the second mold assembly, that is, there are N injection molding positions, and the plastic segments correspondingly injected at the N injection molding positions are correspondingly named as the first to the Nth plastic segments. Among them, at the Mth injection molding position (M<N), the inner cavity of the main mold 310 constitutes the Mth cavity, and the inner cavity of the connecting mold 320 constitutes the connecting cavity of the M+1th cavity.

[0054] During injection molding, the second mold assembly is first positioned at the first injection molding position, and molten plastic is first injected into the connecting chamber between the first cavity and the second cavity. A portion of the core-pulling slider 200 close to the first mold assembly 100 is submerged in the molten plastic. After the first plastic segment 400 is injected, the driving mechanism drives the second mold assembly to move to the second injection molding position along the first direction. The second mold assembly and the first plastic segment 400 that has been formed form the connecting segment between the second cavity and the third cavity. Then, the molten plastic is injected. Since the first plastic segment 400 can support the core-pulling slider 200 after molding, the newly injected molten plastic is not easy to deform the core-pulling slider 200. This is repeated until the molding cavity is fully injected. Since the core-pulling slider 200 is not easy to deform during the entire injection molding process, the quality of the obtained plastic product is good and the yield rate is high.

[0055] In one embodiment, the driving mechanism adopts an electric push rod, which has higher control accuracy and can move the second component to an accurate position, thereby improving the injection molding accuracy. In other embodiments, the driving mechanism can also adopt a piston hydraulic cylinder.

[0056] In one embodiment, the first mold assembly 100 includes a support plate 110 and a molding plate 120 fixed together, the support plate 110 and the molding plate 120 are both disc-shaped, the support plate 110 is used to be placed on a support surface, the molding plate 120 is used to mold the bottom surface of the plastic product, and the core-pulling slider 200 is fixed on the surface of the molding plate 120.

[0057] In one embodiment, the second mold assembly also includes a heating element 330 for heating the inner cavity of the connecting mold 320. During injection molding, the heating element 330 can reduce the cooling rate of the molten plastic, so that the portion of the already molded plastic segment located in the connecting mold 320 is at a higher temperature, and the newly injected molten plastic can be better combined with the previously molded plastic segment, thereby improving the connection strength between the plastic segments and making the molded plastic product more integrated.

[0058] In one embodiment, the heating element 330 is disposed at the bottom of the inner cavity of the connecting mold 320, so that the end of the already formed plastic segment can be more easily combined with the newly injected molten plastic. In other embodiments, the heating element 330 can also be disposed on the side wall of the inner cavity of the connecting mold 320. In this embodiment, the heating element 330 includes a heating shell and a thermal resistance wire disposed in the heating shell. In other embodiments, the heating element 330 can also be a heating rod.

[0059] In one embodiment, the projection of the connecting mold 320 on the main mold 310 along the direction opposite to the first direction is located in the middle of the main mold 310. In this way, during the injection molding process, the connection portion of two adjacent plastic segments is also located in the middle, so that the connection strength between the two plastic segments can be higher, thereby improving the structural strength of the plastic product. In other embodiments, the projection of the connecting mold 320 on the main mold 310 along the direction opposite to the first direction can be located at a position deviated from the middle of the main mold 310.

[0060] In one embodiment, a cooling assembly is provided on the main mold 310, and the cooling assembly is used to cool the main chamber of the main mold 310, so as to accelerate the molding of the molten plastic in the main chamber, so as to quickly perform the next injection molding, thereby improving the injection molding efficiency. Specifically, the cooling assembly includes a liquid inlet 342, a cooling pipeline 344 and a liquid outlet 346 provided on the main mold 310, and the cooling pipeline 344 is circumferentially arranged around the main mold 310. The coolant enters the cooling pipeline 344 from the liquid inlet 342, and then flows out from the liquid outlet 346. During the flow process, the main mold 310 is cooled.

[0061] In one embodiment, the main mold 310 and the connecting mold 320 are detachably connected together. Specifically, the connecting mold 320 includes a molding section and a connecting section. The connecting section is provided with a connecting annular groove 322. The main mold 310 is provided with an annular protrusion for being inserted into the connecting annular groove 322. In order to facilitate the main mold 310 and the connecting mold 320, the main mold 310 is set as a split structure. The main mold 310 includes two halves that are symmetrical along the axial direction. The two halves are connected together to form a complete cylindrical structure. When installed, the semi-annular protrusions in the two halves are inserted into the connecting annular groove 322, thereby realizing the fixed connection between the main mold 310 and the connecting mold 320. In other embodiments, the main mold 310 and the connecting mold 320 can also be fixedly connected by a flange.

[0062] In one embodiment, for a plastic product having a connecting boss 410 disposed at the end, a columnar cavity 326 may be disposed at the bottom of the groove of the connecting mold 320, and the columnar cavity 326 is used to form the connecting boss 410 at the end of the plastic product. Of course, in other embodiments, if the manufactured plastic product does not have a connecting boss 410, the columnar cavity 326 does not need to be disposed at the bottom of the groove of the connecting mold 320.

[0063] In one of the embodiments, the injection molding mold of the plastic product can apply the injection molding method of the plastic product provided by the embodiment of the first aspect of the present invention.

[0064] The use process of the injection molding mold of the plastic product of this embodiment is as follows:

[0065] Before injection molding the required plastic product, it is first assumed that the cavity required for the plastic product can be molded by one injection molding. The imaginary molding cavity is taken as the segmentation object and is divided into the first cavity to the Nth cavity (N≥3). The second cavity to the Nth cavity all include a main cavity and a connecting cavity. The positions of the N cavities correspond one-to-one to the injection positions of the second mold assembly, that is, there are N injection positions, and the plastic segments correspondingly injected at the N injection positions are named as the first to the Nth plastic segments, wherein, at the Mth injection position (M<N), the inner cavity of the main mold 310 constitutes the Mth cavity, and the inner cavity of the connecting mold 320 constitutes the connecting cavity of the M+1th cavity.

[0066] During injection molding, first place the second mold assembly in the first injection molding position. At this time, the second mold assembly is in the first injection molding position (such as Figure 3 As shown in FIG. 1 ), molten plastic (such as Figure 4 As shown in FIG. 1 ), a portion of the core-pulling slider 200 close to the first mold assembly 100 is submerged in the molten plastic. At this time, a cooling liquid passes through the cooling pipeline 344 on the main mold 310, thereby cooling the molten material in the main mold 310, thereby improving the injection molding efficiency.

[0067] After the first plastic segment 400 is injected, the second mold assembly is moved along the first direction to the second injection molding position (eg, Figure 5 As shown in FIG. 1 ), the second mold assembly and the first plastic segment 400 formed form a connecting segment between the second cavity and the third cavity, and then the molten plastic (such as Figure 6 As shown in the figure, since the first plastic segment 400 is formed, it can support the core-pulling slider 200, so the newly injected molten plastic is not easy to deform the core-pulling slider 200. At the same time, due to the presence of the heating element, the cooling speed of some plastic segments in the connecting chamber of the second cavity is slow, so that they can be better combined with the newly injected molten material, thereby improving the connection strength between the various plastic segments, so that the molded plastic product has better integrity. Repeat this process until the molding cavity is fully injected. Since the core-pulling slider 200 is not easy to deform during the entire injection molding process, the quality of the obtained plastic product is better and the yield rate is higher.

[0068] It should be noted that after the injection molding is completed, the plastic protrusion formed in the connecting chamber of the Nth cavity can be removed as needed.

[0069] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for injection molding a plastic product using an injection molding mold, which is used to cast a long strip of hollow plastic product, characterized in that: The injection molding mold includes a first mold assembly, a second mold assembly, a core-pulling slider and a driving mechanism. The core-pulling slider is fixedly connected to the first mold assembly and passes through the second mold assembly. The second mold assembly includes a main mold and a connecting mold. The main mold and the connecting mold both have an inner cavity. In the first direction, the connecting mold is located behind the main mold. The driving mechanism can drive the second mold assembly to move along the first direction and make the second mold assembly have multiple injection positions. Injection molding is performed at multiple injection positions in sequence along the first direction to inject the desired plastic products. The first direction refers to the direction from the bottom to the top of the plastic product. During injection molding, the second mold assembly is first located at the first injection position, and the connecting cavity between the first cavity and the second cavity is first injected. Molten plastic is injected into the mold, and a part of the core-pulling slider close to the first mold assembly is submerged in the molten plastic. After the first plastic segment is injected, the second mold assembly is driven by the driving mechanism to move along the first direction to the second injection position. The second mold assembly and the first plastic segment that has been formed form a connecting section between the second cavity and the third cavity. Then, the molten plastic is injected. Since the molded first plastic segment can support the core-pulling slider, the newly injected molten plastic is not easy to deform the core-pulling slider. This is repeated until the molding cavity is completely injected. The second mold assembly includes a heating element for heating the inner cavity of the connecting mold. The projection of the connecting mold on the main mold along the direction opposite to the first direction is located in the middle of the main mold.

2. The method for injection molding of a plastic product according to claim 1, characterized in that: The heating element is arranged at the bottom of the inner cavity connected to the mold.

3. The injection molding method of a plastic product according to claim 1 or 2, characterized in that: The driving mechanism is an electric push rod.

Images