Injection mold suitable for large injection molded parts and injection molding method thereof

Abstract

The invention relates to an injection mold suitable for large injection molded parts and an injection molding method thereof. The injection mold comprises a profiling inner mold and an outer mold. The profiling inner mold has a simulation cavity inside. The outer surface contour of the profiling inner mold matches the cavity contour. The profiling inner mold is provided with an injection port and an exhaust port. The profiling inner mold can be detachably installed in the outer mold. A distance is left between the outer surface of the profiling inner mold and the inner surface of the outer mold to form a heat exchange medium flow channel. An upper fluid inlet and a lower fluid inlet are provided on one side of the outer mold, and an upper fluid outlet and a lower fluid outlet are provided on the other side. The injection mold of the invention adopts an inner and outer double mold structure. The inner mold is suspended in the outer mold, and the space between the inner mold and the outer mold is used as a flow channel. The inner mold adopts a profiling design to match the outer surface contour with the cavity contour, so that the wall thickness of each part of the profiling inner mold is kept fixed, so that the temperature between the heat exchange medium and the inside of the cavity is uniformly transferred, thereby making the temperature distribution in the cavity more uniform.

Description

Technical Field

[0001] The invention relates to the technical field of injection molds, and in particular to an injection mold suitable for large injection molded parts and an injection molding method thereof. Background Art

[0002] Injection molds are molds used in the injection molding process to shape molten plastic into specific sizes and shapes. In the injection molding process of plastic products, the temperature control of the injection mold directly affects the filling, shaping, molding cycle and quality of the plastic products.

[0003] At present, conventional injection molds mostly use water or oil circuits as heat exchange media to control the temperature in the mold cavity. Usually, a serpentine through hole is directly opened on the injection mold as a flow channel for the heat exchange medium. However, due to the limitations of the cavity structure, the mold structure itself, and processing conditions, the flow channel of the heat exchange medium cannot match the shape of the cavity, resulting in uneven temperature in the cavity. For small injection molded parts, due to the low injection pressure requirements, the low strength requirements for the injection mold, the thin wall thickness of the cavity, and the fast temperature conduction speed, the product usually does not have problems such as dents, internal stress, cracks, and bad deformation.

[0004] For large injection molded parts, due to the high injection pressure holding requirements, the high requirements for the wall thickness of the injection mold cavity, slow temperature conduction, and the inability of the flow channel of the heat exchange medium to match the shape of the cavity, the problem of uneven temperature in the cavity will be magnified, and product quality problems such as dents, internal stress, cracks, and adverse deformation are very likely to occur; and, when the wall thickness of the mold cavity is thicker, a flow channel must be opened on the injection mold, which results in a larger injection mold volume, requiring more mold steel materials and extremely high manufacturing workload, and high manufacturing costs; in addition, the injection mold can only produce products that are consistent with the shape of the cavity, and the utilization rate is low. If different large injection molded parts are to be produced, it is necessary to reprocess and make a new injection mold that matches the cavity, which not only requires redesigning the flow channel of the injection mold, but also increases the production cost of the injection mold.

[0005] Therefore, the present invention proposes an injection mold suitable for large injection molded parts and an injection molding method thereof to solve the above problems. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide an injection mold and an injection molding method suitable for large injection molded parts, so as to solve the problems that the flow channel of the heat exchange medium cannot match the shape of the cavity, resulting in uneven temperature in the cavity, which makes the product prone to defects, and the high cost of mold production and low utilization rate.

[0007] In order to solve the above technical problems, the technical solution of the present invention is: an injection mold suitable for large injection molded parts, the innovation of which is:

[0008] The profiling inner mold has a simulation cavity inside, the outer surface contour of the profiling inner mold matches the contour of the cavity, and the profiling inner mold is provided with an injection port and an exhaust port;

[0009] The outer mold, the contoured inner mold can be detachably installed in the outer mold, a distance is left between the outer surface of the contoured inner mold and the inner surface of the outer mold to form a heat exchange medium flow channel, an upper fluid inlet and a lower fluid inlet are opened on one side of the outer mold, and an upper fluid outlet and a lower fluid outlet are opened on the other side;

[0010] The outer mold comprises a lower outer mold and an upper outer mold, a groove for accommodating the contoured inner mold is provided in the middle of the top surface of the lower outer mold, the upper outer mold is arranged above the lower outer mold, and moves up and down through a first driving guide mechanism to complete the opening and closing action with the lower outer mold;

[0011] The first driving guide mechanism comprises a first driving member, an upper mold frame and a plurality of vertically arranged first guide rods, the plurality of first guide rods being dispersedly arranged at the outer edges of the top surface of the lower outer mold, the upper mold frame being arranged on the top surface of the first guide rods and supported by the first guide rods, the upper outer mold being arranged between the upper mold frame and the lower outer mold, the upper outer mold being provided with first guide holes corresponding to the first guide rods one by one, the first guide rods being movably inserted into the corresponding first guide holes, the first driving member being arranged on the top surface of the upper mold frame, the telescopic end of the first driving member passing through the upper mold frame and connected to the top surface of the upper outer mold, and driving the upper outer mold to move up and down along the first guide rods, the inner side of the first guide rods being provided on the top surface of the lower outer mold, the bottom surface of the upper outer mold being provided with a plurality of first positioning pins corresponding to the first positioning holes one by one, when the upper outer mold is moved down and molded with the lower outer mold, the first positioning pins enter into the corresponding first positioning holes;

[0012] The profiling inner mold comprises a left inner mold and a right inner mold, both of which are installed in the lower outer mold, and the right inner mold is driven by the second driving guide mechanism to move horizontally to complete the opening and closing action with the left inner mold;

[0013] The second driving guide mechanism comprises a second driving member, a side mold frame, a push rod, a plurality of second guide rods and a guide plate, a third guide hole is opened on the side wall of the lower outer mold, one end of the push rod passes through the third guide hole to enter the lower outer mold and is connected to the right inner mold, and the other end is connected to the guide plate, the side mold frame is vertically arranged on a side of the guide plate away from the lower outer mold, a plurality of second guide rods are scattered around the push rod, the two ends of the second guide rod are respectively connected to the lower outer mold and the side mold frame, a second guide hole corresponding to each second guide rod is opened on the guide plate, each second guide rod is movably inserted into the corresponding second guide hole, the second driving member is arranged on a side of the side mold frame away from the guide plate, the telescopic end of the second driving member passes through the side mold frame and is connected to the guide plate, and drives the guide plate to move horizontally along the second guide rod;

[0014] The left inner mold and the right inner mold are respectively connected to the inner side wall of the lower outer mold and the push rod through a connecting assembly, and the connecting assembly includes a fixed shaft, a movable shaft sleeve and a limit shaft sleeve;

[0015] The fixed shaft is arranged horizontally, one end of the fixed shaft is connected to the inner side wall of the lower outer mold or the end of the push rod, and the other end face of the fixed shaft extends outwardly in the axial direction to form three second positioning pins, and the three second positioning pins are distributed in an equilateral triangle, and a positioning protrusion is formed on the side wall of one of the second positioning pins extending outwardly in the radial direction, the limiting sleeve is threadedly sleeved on the outside of the fixed shaft, the movable sleeve is threadedly sleeved on the side of the limiting sleeve of the fixed shaft close to the second positioning pin, and the end of the movable sleeve away from the limiting sleeve extends outwardly in the radial direction to form a clamping block;

[0016] The outer end surfaces of the left inner mold and the right inner mold are provided with positioning grooves for the second positioning pins to enter one by one, and an annular limiting groove for the clamping block to enter and rotate with the movable shaft sleeve. When the left inner mold or the right inner mold is pushed to make the second positioning pin enter the positioning groove, the clamping block enters the annular limiting groove at the same time, and then the movable shaft sleeve is rotated and tightened to tightly press the left inner mold or the right inner mold onto the fixed shaft through the clamping block, so as to realize a fixed connection between the left inner mold or the right inner mold and the fixed shaft, and finally the limiting shaft sleeve is rotated and tightened so that the end face of the limiting shaft sleeve is tightly against the end face of the movable shaft sleeve, so as to strengthen the fixation of the movable shaft sleeve;

[0017] The lower outer mold is sealed and connected with the upper outer mold through a first sealing assembly when the lower outer mold is molded together. The first sealing assembly includes a first sealing ring and a second sealing ring arranged on the top surface of the lower outer mold;

[0018] The first sealing ring is arranged inside the first positioning hole, the top surface of the lower outer mold and the bottom surface of the upper outer mold cooperate to form a first sealing groove, the first sealing ring is arranged in the first sealing groove, the inner side of the first sealing groove on the top surface of the lower outer mold is recessed downward to form a first horizontal step surface, the bottom surface of the upper outer mold bulges downward to form a second horizontal step surface, the first horizontal step surface and the second horizontal step surface cooperate to form a second sealing groove, and the second sealing ring is arranged in the second sealing groove;

[0019] The push rod is sealed and connected to the lower outer mold through a second sealing assembly, and the second sealing assembly includes a graphite sealing ring, a third sealing ring and an oil seal;

[0020] There are two graphite sealing rings, both of which are movably sleeved on the outside of the push rod and are respectively installed on the inner wall and outer wall of the lower outer mold through the sealing cover. The inner wall of the graphite sealing ring is tightly fitted with the outer wall of the push rod. A third sealing groove is opened on the hole wall of the third guide hole. The third sealing ring is arranged in the third sealing groove. A retaining ring and a retaining spring are respectively arranged on both sides of the third sealing ring. The retaining ring and the retaining spring are both installed in the third sealing groove corresponding to the third sealing ring. The inner wall of the third sealing ring bulges toward the middle to form an arc-shaped surface. The third sealing ring is deformed under the pressure of the retaining spring elastic force so that the arc-shaped surface is tightly pressed on the outer wall of the push rod. An oil seal matching groove is opened on the hole wall of the third guide hole, and the oil seal is installed in the oil seal matching groove.

[0021] The limiting sleeve is sealed and connected to the fixed shaft through a third sealing assembly, the third sealing assembly includes a fourth sealing ring, an outer wall of the fixed shaft is provided with an external thread on one side close to the second positioning pin, an inner wall of the limiting sleeve is provided with an internal thread matching the external thread on one side close to the movable sleeve, a fourth sealing groove is provided on the inner wall of the limiting sleeve on the side of the internal thread away from the movable sleeve, and the fourth sealing ring is arranged in the fourth sealing groove;

[0022] The left inner mold is sealed and connected with the right inner mold through the fourth sealing component when the left inner mold is closed. The fourth sealing component includes a contour sealing ring. The outer side of the parting surface of the left inner mold is concave inward along the axial direction to form a first axial step surface, and the outer side of the parting surface of the right inner mold is convex outward along the axial direction to form a second axial step surface. The first axial step surface and the second axial step surface cooperate to form a fifth sealing groove, and the contour sealing ring is arranged in the fifth sealing groove.

[0023] The technical solution of the present invention also provides: an injection molding method using the above-mentioned injection mold suitable for large injection molded parts, comprising the following steps:

[0024] Step 1: According to the structural characteristics of the injection molded part, a three-dimensional model of the simulation cavity is established, the position of the injection parting surface is clarified, and based on the contour of the simulation cavity, an absolutely safe value is added outward as the initial wall thickness d1 to form the initial three-dimensional model of the profiling inner mold;

[0025] Step 2: Take the wall thickness as a variable and the initial wall thickness d1 as the initial value of the variable, perform strength verification on the initial three-dimensional model of the contoured inner mold, and obtain the optimal safe wall thickness value d xs , then take the best safe wall thickness value d xs As the wall thickness, the final three-dimensional model of the contoured inner mold is established;

[0026] Step 3: According to the final three-dimensional model of the contoured inner mold, the mold steel is used as the base, and the left inner mold and the right inner mold are respectively made by 3D printing, and the contoured sealing ring prepared in advance according to the parting surface is installed on the left inner mold;

[0027] Step 4: After the outer mold is connected to the supporting equipment, the manufactured left inner mold and right inner mold are installed into the outer mold, and the left inner mold and the right inner mold are tested for mold closing;

[0028] Step 5, after the left inner mold and the right inner mold are tested and qualified, the left inner mold is molded together with the right inner mold, the upper outer mold is moved down to be molded together with the lower outer mold, hot steam is injected into the heat exchange medium flow channel to heat the contour inner mold, and when the temperature in the cavity of the contour inner mold reaches the requirement, molten plastic is injected into the cavity;

[0029] Step 6: After the molten plastic is injected, the pressure is maintained. During the pressure maintenance process, the hot steam in the heat exchange medium flow channel is quickly discharged, and medium-temperature water is injected into the heat exchange medium flow channel to pre-cool the contour inner mold, and then cooling water is injected into the heat exchange medium flow channel to cool the contour inner mold;

[0030] Step 7: After cooling, drain the cooling water in the heat exchange medium flow channel, then move the upper outer mold to open the mold, move the right inner mold to open the mold, and demold the plastic cooled and molded injection molded part.

[0031] Furthermore, in step 2, the optimal safe wall thickness value d is obtained by strength verification. xs The method is as follows: taking the initial wall thickness d1 as the initial value, the initial three-dimensional model of the profiling inner mold is strength-checked to determine whether the initial wall thickness d1 of the profiling inner mold meets the process requirements. If so, the initial wall thickness d1 minus the fixed value D is used as the new wall thickness d2, and the newly formed three-dimensional model of the profiling inner mold is strength-checked for the second time, until the wall thickness of the i-th strength check does not meet the process requirements, and the wall thickness d at the i-1-th strength check is selected. i-1 As the optimal wall thickness value, the optimal safe wall thickness value d is calculated according to the following formula xs :

[0032] d xs =σ1d i-1

[0033] Among them, σ1 is the first safety factor, and its value is 1.1-1.3.

[0034] Furthermore, in step 3, when the left inner mold and the right inner mold are 3D printed, a certain size needs to be reserved on the outer end surface of the printed inner mold for processing the positioning groove and the annular limiting groove. When processing the positioning groove and the annular limiting groove, it is necessary to ensure that the distance between the bottom surface of the limiting groove and the annular limiting groove and the wall surface of the simulation cavity of the inner mold body is greater than or equal to dxs .

[0035] Furthermore, in step 4, the method for detecting the closing of the left inner mold and the right inner mold comprises the following steps:

[0036] Step 4-1, preliminary mold closing test: before installing the manufactured left inner mold and right inner mold into the outer mold, use the injection molded part model obtained by 3D printing based on the three-dimensional model of the simulation cavity in advance, place the left inner mold and the right inner mold on both sides of the injection molded part model respectively, manually move the left inner mold and the right inner mold to close the mold, and use the three-coordinate measurement method to determine whether the parting surface joint of the left inner mold and the right inner mold is shifted, and complete the preliminary mold closing test;

[0037] Step 4-2, mold closing accuracy detection: After the preliminary mold closing detection is qualified, the left inner mold and the right inner mold are installed in the outer mold, the left inner mold and the right inner mold are closed, and an optical projector is used to detect whether the parting surface joint of the left inner mold and the right inner mold is shifted, and the mold closing accuracy detection is completed;

[0038] Step 4-3, mold sealing test: After the mold precision test is qualified, with the left inner mold and the right inner mold in the mold-sealed state, the upper outer mold and the lower outer mold are closed, and the heat exchange medium flows into the flow channel at the first safety limit flow rate v s1 After the hot steam is injected for the first time period t1, the hot steam in the heat exchange medium flow channel is emptied, and then the heat exchange medium flow channel is filled with hot steam at a second safety limit flow rate v s2 Inject cooling water for the second time period t2, drain the cooling water in the heat exchange medium flow channel, open the upper outer mold and the lower outer mold, remove residual water on the outer walls of the left inner mold and the right inner mold, open the left inner mold and the right inner mold, and observe whether water enters the cavity of the left inner mold and the right inner mold.

[0039] Furthermore, the first safety limit flow rate v s1 The calculation formula is: s1 =σ2v qmax ;

[0040] Among them, v qmax is the maximum flow rate of hot steam required by the injection molding process, σ2 is the second safety factor, and the value is 1.5-2;

[0041] The calculation formula for the first time period t1 is: t1=t qmax ;

[0042] Among them, t qmax The longest hot steam injection time required for the injection molding process;

[0043] The second safety limit flow rate v s2 The calculation formula is: s2 =σ3v wmax ;

[0044] Among them, v wmax is the maximum flow rate of cooling water required by the injection molding process, σ3 is the third safety factor, and its value is 1.2-1.5;

[0045] The calculation formula for the second time period t2 is: t2=t wmax ;

[0046] Among them, t wmax The longest cooling water injection time required by the injection molding process.

[0047] Further, the supporting equipment includes an injection molding machine, a water tank, a refrigerator, a steam generator and a heat exchanger;

[0048] The nozzle opening of the injection molding machine is connected to the injection molding port of the outer mold through a first pipeline;

[0049] The water outlet of the water tank is connected to the water inlet of the refrigerator through the second pipeline, the water outlet of the refrigerator is connected to the lower fluid inlet of the outer mold through the third pipeline, the upper fluid outlet of the outer mold is connected to the water inlet of the water tank through the sixth pipeline, and is connected to the water inlet of the refrigerator through the seventh pipeline, which is a branch pipeline of the sixth pipeline;

[0050] The water outlet of the water tank is connected to the water inlet of the steam generator through a fourth pipeline, the steam outlet of the steam generator is connected to the upper fluid inlet of the outer mold through a fifth pipeline, and the lower fluid outlet of the outer mold is connected to the steam circulation port of the steam generator through an eighth pipeline;

[0051] The water outlet of the water tank is connected to the water inlet of the heat exchanger through the ninth pipeline, the water outlet of the heat exchanger is connected to the lower fluid inlet of the outer mold through the tenth pipeline, the steam outlet of the steam generator is connected to the air inlet of the heat exchanger through the eleventh pipeline, and the air outlet of the heat exchanger is connected to the steam circulation port of the steam generator through the twelfth pipeline.

[0052] The advantages of the present invention are:

[0053] (1) The injection mold of the present invention adopts an inner and outer double mold structure. The outer mold adopts a hollow design, and the inner mold is suspended inside the outer mold. The space between the inner mold and the outer mold is used as a flow channel. During injection molding, after the heat exchange medium enters the flow channel, it can fully and evenly surround the inner mold. In addition, the inner mold adopts a contour design so that the outer surface contour matches the cavity contour, so that the wall thickness of the contoured inner mold is kept constant, so that the temperature between the heat exchange medium and the inside of the cavity is evenly transferred, thereby making the temperature distribution in the cavity more uniform.

[0054] The profiling inner mold can be detachably installed in the outer mold. When producing large injection molded parts with different shapes, it is only necessary to remove the original profiling inner mold, remake a new profiling inner mold according to the shape of the large injection molded part, and install the new profiling inner mold in the outer mold for use, which not only improves the utilization rate of the outer mold, but also reduces the production cost of the mold;

[0055] In addition, when designing the contoured inner mold, the wall thickness can be designed to be as thin as possible while meeting the process strength requirements, thereby reducing the amount of mold steel material used, which can not only significantly reduce the production cost of the contoured inner mold, but also increase the temperature conduction rate and improve the injection molding efficiency.

[0056] (2) The present invention realizes precise mold closing between the upper outer mold and the lower outer mold through the mutual cooperation between the first guide rod and the first positioning pin, and improves the movement accuracy of the push rod through the mutual cooperation between the second guide rod and the guide plate, thereby realizing precise mold closing between the right inner mold and the left inner mold.

[0057] (3) The connection assembly of the present invention utilizes the second positioning pin to limit the radial position of the left inner mold and the right inner mold, and utilizes the movable sleeve to limit the fine axial position of the left inner mold and the right inner mold, thereby realizing the relative fixation between the left inner mold and the right inner mold and the fixed shaft, and the limiting sleeve is used to strengthen the fixation of the movable sleeve, so as to prevent the movable sleeve from loosening under the impact of high-speed fluid and affecting the mold closing accuracy and connection strength between the left inner mold and the right inner mold.

[0058] (4) The first sealing assembly of the present invention provides double protection for the sealing strength when the upper outer mold and the lower outer mold are molded together by arranging the first sealing ring and the second sealing ring on two horizontal step surfaces;

[0059] The second sealing assembly uses two graphite sealing rings to effectively seal the two sides of the third guide hole, and uses the third sealing ring to strengthen the seal between the push rod and the hole wall of the third guide hole, thereby improving the sealing effect of the reciprocating motion of the push rod. By setting a retaining ring, the elastic force of the retaining ring is used to always suppress the deformation of the third sealing ring, thereby improving the sealing effect. By setting a retaining ring, a retaining ring of appropriate thickness can be selected according to the deformation requirement of the third sealing ring to limit the third sealing ring, thereby reducing the difficulty of installing the third sealing ring. In addition, by setting an oil seal, a good lubrication effect is achieved, reducing the friction and wear of the push rod;

[0060] The third sealing assembly can effectively prevent the heat exchange medium from entering the threaded connection between the limiting sleeve, the movable sleeve and the fixed shaft by providing the fourth sealing ring, thereby protecting the threads from damage;

[0061] The fourth sealing component can improve the sealing performance of the left and right inner molds when they are closed and prevent the heat exchange medium from entering the cavity by setting the contour sealing ring on the axial step surface at the parting surface of the left and right inner molds, without affecting the connection of the parting surface between the left and right inner molds and the closing accuracy.

[0062] (5) In the injection molding method of the present invention, the profiling inner mold is manufactured by combining three-dimensional modeling, strength verification and 3D printing technology, which improves the one-time success rate of the profiling inner mold and effectively avoids rework and repeated production;

[0063] When injecting molten plastic into the cavity, the cavity is quickly heated up by injecting high-temperature hot steam, and the temperature is maintained at a high temperature to keep the plastic in a good molten flow state, ensuring that the plastic can fill the entire cavity and avoid premature solidification of the plastic due to an overly large cavity;

[0064] During the pressure holding process, medium-temperature water is first injected for temperature transition, and finally cooling water is injected for accelerated cooling. This cooling method can, on the one hand, prevent the plastic in the cavity from cooling too quickly and affecting product quality, and on the other hand, prevent the strength of each component from being affected by too fast temperature changes in the outer mold, thereby extending the service life of the parts and the contoured inner mold.

[0065] In addition, hot steam is used to heat the inner mold. Compared with other high-temperature liquids, on the one hand, it can be extracted more quickly to avoid contact with medium-temperature water, thereby reducing the vaporization of medium-temperature water. On the other hand, hot steam is obtained by heating water and has low cost.

[0066] (6) The present invention uses the initial wall thickness d1 as the initial wall thickness value for strength verification, and then gradually reduces the wall thickness until the optimal wall thickness that meets the process strength requirements is screened out, and the optimal wall thickness value is multiplied by the safety factor as the optimal safe wall thickness value d1 used in the final three-dimensional model. xs , while ensuring the strength of the inner mold and the economy of production, the safety of the inner mold injection molding process is improved.

[0067] (7) When inspecting the mold closing of the left inner mold and the right inner mold, the present invention adopts the sequence of preliminary mold closing inspection, mold closing accuracy inspection, and finally mold closing sealing inspection, thereby realizing comprehensive inspection of the inner mold and avoiding repeated operations, thereby improving inspection efficiency. In addition, the three-coordinate measurement method and the optical projector inspection method are successively used to inspect the joints of the parting surfaces of the left inner mold and the right inner mold, thereby improving the inspection accuracy of the mold closing accuracy.

[0068] (8) In the injection molding method of the present invention, when conducting the mold sealing test, the injection flow rate of hot steam and cooling water is multiplied by a safety factor based on the maximum flow rate required by the injection molding process, so as to improve the reliability of the sealing test, and the inner mold is opened only after the residual moisture on the outer walls of the left inner mold and the right inner mold is removed, so as to avoid the adverse effect of the residual moisture on the outer wall on the test result.

[0069] (9) The injection molding machine, water tank, refrigerator, steam generator and heat exchanger in the supporting equipment of the present invention are connected through pipelines, realizing the functions of plastic injection, cooling water circulation recovery, hot steam circulation, and heat exchange to prepare medium-temperature water, with low energy consumption and avoiding waste of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0071] Figure 1 Schematic diagram of the structure of a propeller in an embodiment of the present invention.

[0072] Figure 2 It is an exploded view of the contoured inner mold of the propeller of the present invention.

[0073] Figure 3 It is a structural schematic diagram of the injection mold of the present invention.

[0074] Figure 4 It is an enlarged view of point A of the present invention.

[0075] Figure 5 It is a cross-sectional view of the connection assembly of the present invention.

[0076] Figure 6 It is a schematic diagram of the outer end surface of the left inner mold or the right inner mold of the present invention.

[0077] Figure 7 It is a schematic end view of the fixed shaft and the movable sleeve of the present invention.

[0078] Figure 8 It is a cross-sectional view of the parting surface when the left inner mold and the right inner mold of the present invention are closed.

[0079] Fig. 9 It is a schematic diagram of the connection between the injection mold and the supporting equipment of the present invention.

[0080] Fig.10 Flow chart of the injection molding method of the present invention.

[0081] Fig.11 The present invention is a flow chart of the method for obtaining the optimal safe wall thickness value. DETAILED DESCRIPTION

[0082] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0083] This embodiment is described by taking the propeller of a large ship model for display as an injection molded part.

[0084] like Figure 1 As shown, the structure of the propeller of the large ship model includes a cylindrical hub 1a and three blades 1b. The roots of the three blades 1b are connected to the hub 1a. The thickness of the blades 1b gradually decreases from the root to the tip. The tip is an arc-shaped slope. The propeller rotates in the water, and the blade surface of the blade 1b directly facing the impact of the water flow is the front, and the liquid surface on the other side is the back. The arc-shaped slope is inclined from the connection with the front toward the direction away from the center of the hub 1a.

[0085] The injection mold used to make the propeller adopts an inner and outer double mold structure, including a contoured inner mold 2 and an outer mold 3.

[0086] like Figure 3 As shown, the outer mold 3 adopts a hollow design, and the outer mold 3 includes a lower outer mold 3a and an upper outer mold 3b. A groove for accommodating the contoured inner mold 2 is opened in the middle of the top surface of the lower outer mold 3a. The upper outer mold 3b is arranged above the lower outer mold 3a, and moves up and down through a first driving guide mechanism to complete the opening and closing action with the lower outer mold 3a.

[0087] The first driving guide mechanism includes a first driving member 4a, an upper mold frame 4b and eight vertically arranged first guide rods 4c, the eight first guide rods 4c are dispersedly arranged at the outer edge of the top surface of the lower outer mold 3a, the upper mold frame 4b is arranged on the top surface of the first guide rods 4c and supported by each first guide rod 4c, the upper outer mold 3b is arranged between the upper mold frame 4b and the lower outer mold 3a, and the upper outer mold 3b is provided with first guide holes corresponding to each first guide rod 4c one by one, and each first guide rod 4c is movably inserted into the corresponding first guide hole. In the hole, the first driving member 4a is arranged on the top surface of the upper mold frame 4b, the telescopic end of the first driving member 4a passes through the upper mold frame 4b and is connected to the top surface of the upper outer mold 3b, and drives the upper outer mold 3b to move up and down along the first guide rod 4c, twelve first positioning holes are opened on the inner side of the first guide rod 4c on the top surface of the lower outer mold 3a, and twelve first positioning pins 4d corresponding to each first positioning hole are arranged on the bottom surface of the upper outer mold 3b. When the upper outer mold 3b moves down to close the mold with the lower outer mold 3a, the first positioning pins 4d enter the corresponding first positioning holes. The first driving guide mechanism realizes the precise closing of the upper outer mold 3b and the lower outer mold 3a through the mutual cooperation of the first guide rod 4c and the first positioning pins 4d.

[0088] like Figure 2As shown, the profiling inner mold 2 adopts a profiling design. The profiling inner mold 2 includes a left inner mold 2a and a right inner mold 2b. The left inner mold 2a and the right inner mold 2b form a profiling inner mold 2 after the mold is closed. The profiling inner mold 2 has a simulation cavity inside. The contour of the simulation cavity is consistent with the external contour of the propeller. The outer surface contour of the profiling inner mold 2 matches the cavity contour, so that the wall thickness of the profiling inner mold 2 is kept consistent, which is conducive to achieving uniform temperature transfer between the heat exchange medium and the inside of the cavity, thereby making the temperature distribution in the cavity more uniform; when designing the profiling inner mold 2, the wall thickness can be designed to be thinner as much as possible while meeting the process strength requirements, thereby reducing the amount of mold steel material, which can significantly reduce the production cost of the profiling inner mold 2, and at the same time improve the temperature conduction rate and improve the injection molding efficiency.

[0089] The left inner mold 2a and the right inner mold 2b are both installed in the lower outer mold 3a. The right inner mold 2b is driven by the second driving guide mechanism to move horizontally to complete the opening and closing action with the left inner mold 2a. After the left inner mold 2a and the right inner mold 2b are closed, a distance is left between the outer surface of the contoured inner mold 2 and the inner surface of the outer mold 3 to form a heat exchange medium flow channel. During injection molding, after the heat exchange medium enters the flow channel, it can fully and evenly surround the inner mold, thereby achieving uniform heat transfer and ensuring uniform temperature distribution in the cavity of the inner mold.

[0090] The second driving guide mechanism includes a second driving member 5a, a side mold frame 5b, a push rod 5e, eight second guide rods 5c and a guide plate 5d. A third guide hole is opened on the side wall of the lower outer mold 3a. One end of the push rod 5e passes through the third guide hole and enters the lower outer mold 3a to be connected to the right inner mold 2b, and the other end is connected to the guide plate 5d. The side mold frame 5b is vertically arranged on the side of the guide plate 5d away from the lower outer mold 3a. The bottom and top ends of the side mold frame 5b are connected to the lower outer mold 3a through the connecting plate 5f. The eight second guide rods 5c are connected to the lower outer mold 3a through the connecting plate 5f. 5c is dispersed around the push rod 5e, the two ends of the second guide rod 5c are connected to the lower outer mold 3a and the side mold frame 5b respectively, the guide plate 5d is provided with second guide holes corresponding to each second guide rod 5c, each second guide rod 5c is movably inserted into the corresponding second guide hole, the second driving member 5a is arranged on the side of the side mold frame 5b away from the guide plate 5d, the telescopic end of the second driving member 5a passes through the side mold frame 5b and is connected to the guide plate 5d, and drives the guide plate 5d to move horizontally along the second guide rod 5c. The second driving guide mechanism improves the moving accuracy of the push rod 5e through the mutual cooperation of the second guide rod 5c and the guide plate 5d, thereby realizing the precise mold closing of the right inner mold 2b and the left inner mold 2a.

[0091] In order to improve the utilization rate of the injection mold, the contoured inner mold 2 can be detachably installed in the outer mold 3. After the propeller injection molded part is completed, when it is necessary to produce a large injection molded part with a different shape, it is only necessary to remove the contoured inner mold 2 of the propeller, remake a new contoured inner mold 2 according to the shape of the large injection molded part, and install the new contoured inner mold 2 in the outer mold 3 for use. This not only improves the utilization rate of the outer mold 3, but also reduces the production cost of the mold.

[0092] The left inner mold 2a and the right inner mold 2b are connected to the inner side wall of the lower outer mold 3a and the push rod 5e respectively through connecting components. Figure 5-7 As shown, the connecting assembly includes a fixed shaft 6a, a movable shaft sleeve 6c and a limiting shaft sleeve 6b;

[0093] The fixed shaft 6a is arranged horizontally, one end of the fixed shaft 6a is connected to the inner side wall of the lower outer mold 3a or the end of the push rod 5e, and the other end face of the fixed shaft 6a extends outwardly in the axial direction to form three second positioning pins 6e, and the three second positioning pins 6e are distributed in an equilateral triangle. In order to facilitate the determination of the installation angle of the inner mold at the fixed shaft 6a, a positioning protrusion 6f is formed on the side wall of one of the second positioning pins 6e extending outwardly in the radial direction, and the limiting sleeve 6b is threadedly sleeved on the outer side of the fixed shaft 6a, and the movable sleeve 6c is threadedly sleeved on the side of the limiting sleeve 6b of the fixed shaft 6a close to the second positioning pin 6e, and the end of the movable sleeve 6c away from the limiting sleeve 6b extends outwardly in the radial direction to form a block 6d; the outer end surfaces of the left inner mold 2a and the right inner mold 2b are provided with positioning grooves 7a for the second positioning pins 6e to enter one by one, and an annular limiting groove 7 for the block 6d to enter and rotate with the movable sleeve 6c. b. When the left inner mold 2a or the right inner mold 2b is pushed, the second positioning pin 6e enters the positioning groove 7a, and the left inner mold 2a and the right inner mold 2b are radially limited. The block 6d enters the annular limiting groove 7b at the same time. Then, by rotating the movable sleeve 6c, the block 6d rotates while pushing the inner mold to move in the direction close to the fixed shaft 6a. When the movable sleeve 6c is tightened, the block 6d presses the left inner mold 2a or the right inner mold 2b tightly on the fixed shaft 6a, and limits the axial position of the left inner mold 2a or the right inner mold 2b, thereby realizing a fixed connection between the left inner mold 2a or the right inner mold 2b and the fixed shaft 6a. Finally, the limiting sleeve 6b is rotated and tightened, so that the end face of the limiting sleeve 6b is tightly against the end face of the movable sleeve 6c, and the movable sleeve 6c is strengthened and fixed to prevent the movable sleeve 6c from loosening under the impact of high-speed fluid and affecting the mold closing accuracy and connection strength between the left inner mold 2a and the right inner mold 2b.

[0094] The left inner mold 2a and its corresponding fixed shaft 6a and the lower outer mold 3a cooperate to form an injection port 8 for injecting molten plastic into the cavity, and the left inner mold 2a and its corresponding fixed shaft 6a cooperate to form an exhaust port 9, the outlet end of the exhaust port 9 is located outside the lower outer mold 3a, and an upper fluid inlet 10a and a lower fluid inlet 10b are formed on one side of the lower outer mold 3a, and an upper fluid outlet 10c and a lower fluid outlet 10d are formed on the other side.

[0095] Due to the requirements of the injection molding process, hot steam and cooling water need to be injected into the heat exchange medium flow channel, which requires sealing of multiple joints to ensure the quality of the injection molded product and operational safety. Among them:

[0096] The first seal: Figure 3 As shown, the lower outer mold 3a is sealed and connected with the upper outer mold 3b through the first sealing component when the lower outer mold 3a is molded together. The first sealing component includes a first sealing ring 11a and a second sealing ring 11b arranged on the top surface of the lower outer mold 3a; the first sealing ring 11a is arranged on the inner side of the first positioning hole, and the top surface of the lower outer mold 3a and the bottom surface of the upper outer mold 3b are cooperated to open a first sealing groove, and the first sealing ring 11a is arranged in the first sealing groove on the top surface of the lower outer mold 3a, and the inner side of the first sealing groove on the top surface of the lower outer mold 3a is recessed downward to form a first horizontal step surface, and the bottom surface of the upper outer mold 3b is convex downward to form a second horizontal step surface, and the first horizontal step surface and the second horizontal step surface are cooperated to open a second sealing groove, and the second sealing ring 11b is arranged in the second sealing groove on the first horizontal step surface. This sealing structure in which the two sealing rings are arranged on two horizontal step surfaces provides double protection for the sealing strength when the upper outer mold 3b and the lower outer mold 3a are molded together. The first sealing ring 11a and the second sealing ring 11b can be O-rings.

[0097] Second seal: Figure 4 As shown, the push rod 5e is sealed and connected to the lower outer mold 3a through the second sealing assembly, and the second sealing assembly includes a graphite sealing ring 12b, a third sealing ring 12c and an oil seal 12f; there are two graphite sealing rings 12b, both of which are movably mounted on the outside of the push rod 5e, and are respectively installed on the inner wall and outer wall of the lower outer mold 3a through the sealing cover 12a, and a sealing ring installation groove is opened on the inner side of the sealing cover 12a, and the graphite sealing ring 12b is arranged in the sealing ring installation groove. The sealing cover 12a is installed on the lower outer mold 3a by bolts, and the end face of the graphite sealing ring 12b is attached to the side wall of the lower outer mold 3a, and the inner wall of the graphite sealing ring 12b is tightly attached to the outer wall of the push rod 5e, so that both sides of the third guide hole are effectively sealed.

[0098] There are two third sealing rings 12c, and two third sealing grooves are formed on the hole wall of the third guide hole. The third sealing rings 12c are respectively arranged in the corresponding third sealing grooves. A retaining ring 12d and a retaining spring 12e are respectively arranged on both sides of the third sealing ring 12c. The retaining ring 12d and the retaining spring 12e are both installed in the third sealing groove corresponding to the third sealing ring 12c. The inner wall of the third sealing ring 12c bulges toward the middle to form an arcuate surface. The third sealing ring 12c is deformed under the elastic pressure of the retaining spring 12e so that the arcuate surface is always tightly pressed on the outer side wall of the push rod 5e, thereby strengthening the sealing between the push rod 5e and the hole wall of the third guide hole, improving the sealing effect of the reciprocating motion of the push rod 5e, and according to the deformation requirement of the third sealing ring 12c, a retaining ring 12d of appropriate thickness can be selected to limit the third sealing ring 12c, thereby reducing the installation difficulty of the third sealing ring 12c. In addition, in order to reduce the friction and wear of the push rod 5e, the oil seal 12f has two oil seal matching grooves. The inner sides of the two third sealing grooves on the hole wall of the third guide hole are opened. The oil seal 12f is installed in the corresponding oil seal matching grooves to play a good lubrication role.

[0099] The third seal: Figure 5 As shown, the limiting sleeve 6b is sealed and connected to the fixed shaft 6a through the third sealing assembly, the third sealing assembly includes a fourth sealing ring 13a, an external thread is provided on the side of the outer wall of the fixed shaft 6a close to the second positioning pin 6e, an internal thread matching the external thread is provided on the side of the inner wall of the limiting sleeve 6b close to the movable sleeve 6c, a fourth sealing groove is provided on the side of the inner wall of the limiting sleeve 6b away from the movable sleeve 6c, and the fourth sealing ring 13a is arranged in the fourth sealing groove, which can effectively prevent the heat exchange medium from entering the threaded connection between the limiting sleeve 6b, the movable sleeve 6c and the fixed shaft 6a, and protect the thread from damage. The fourth sealing ring 13a adopts an O-type sealing ring.

[0100] Fourth seal: Figure 8 As shown, the left inner mold 2a is sealed and connected with the right inner mold 2b through the fourth sealing component when the left inner mold 2a is molded together. The fourth sealing component includes a contour sealing ring 14a. The outer side of the parting surface of the left inner mold 2a is concave inward along the axial direction to form a first axial step surface, and the outer side of the parting surface of the right inner mold 2b is convex outward along the axial direction to form a second axial step surface. The first axial step surface and the second axial step surface cooperate to form a fifth sealing groove. The contour sealing ring 14a is arranged in the fifth sealing groove of the first axial step surface. This sealing method can not only improve the sealing performance of the left inner mold 2a and the right inner mold 2b when the mold is molded together and prevent the heat exchange medium from entering the cavity, but also will not affect the connection of the parting surfaces between the left inner mold 2a and the right inner mold 2b and the mold closing accuracy.

[0101] The propeller needs to be injection molded by polypropylene material. The injection molding process parameters of the polypropylene material are shown in Table 1.

[0102] Table 1 Polypropylene injection molding process parameters

[0103] Melting point 160-175℃ Decomposition temperature 350℃ Melt temperature 200-240℃ Mold temperature 20-70℃ Injection pressure 70-150MPa Injection speed 100-150mm / s

[0104] A method for forming a propeller by injection molding using the above injection mold, such as Fig.10 As shown, the following steps are included:

[0105] Step 1: According to the structural characteristics of the propeller to be injected, a three-dimensional model of the simulation cavity is established, and the curved surface of the back of the three blades 1b of the propeller is clearly used as the position of the injection parting surface. The injection parting surface is required to be smoothly curved. On the basis of the contour of the simulation cavity, an absolutely safe value is added outward as the initial wall thickness d1 to form the initial three-dimensional model of the profiling inner mold 2. In this embodiment, d1=70mm;

[0106] Step 2: Take the wall thickness as a variable, take the initial wall thickness d1 = 70 mm as the initial value of the variable, input the parameters of the 45 steel used to make the profiling inner mold 2, perform strength verification on the established initial three-dimensional model of the profiling inner mold 2, and obtain the optimal safe wall thickness value d xs , then take the best safe wall thickness value d xs As the wall thickness, the final three-dimensional model of the contour inner mold 2 is established. The specific method is as follows:

[0107] like Fig.11 As shown, the initial wall thickness d1=70mm is used as the initial value, and the initial three-dimensional model of the profiling inner mold 2 is strength-checked to determine whether the initial wall thickness d1=70mm of the profiling inner mold 2 meets the process requirements. The value of the initial wall thickness d1 is selected based on experience. If it does not meet the process requirements after verification, the initial wall thickness d1 is re-selected for strength verification again until it meets the process requirements. In this embodiment, the initial wall thickness d1=70mm meets the process requirements, and the initial wall thickness d1=70mm minus the fixed value D=3mm is used as the new wall thickness d2, d2=67mm, the newly formed profiling inner mold 2 three-dimensional model is subjected to a second strength check, until the wall thickness d9=46mm of the 9th strength check cannot meet the process requirements, and the wall thickness d8=49mm at the 8th strength check is selected as the optimal wall thickness value. The optimal wall thickness value obtained by this method belongs to the optimal wall thickness value under ideal operating conditions, but in the actual operation process, there are various uncontrollable factors. Therefore, the safety factor needs to be considered to improve the construction safety. Therefore, the optimal safe wall thickness value d is calculated according to the following formula xs :

[0108] d xs =σ1d8=1.2×49=58.8mm

[0109] Wherein, σ1 is the first safety factor, and its value is 1.1-1.3. In this embodiment, σ1 is 1.2.

[0110] Step 3: According to the final three-dimensional model of the profiling inner mold 2, 45 steel is used as the matrix, and 3D printing is used to make the left inner mold 2a and the right inner mold 2b respectively. During 3D printing, a certain size needs to be reserved on the outer end surface of the printed inner mold for processing the positioning groove 7a and the annular limiting groove 7b. When processing the positioning groove 7a and the annular limiting groove 7b, it is necessary to ensure that the distance between the bottom surface of the limiting groove and the annular limiting groove 7b and the wall surface of the simulation cavity of the inner mold body is greater than or equal to d xs To ensure the safety of the inner mold, after the inner mold is made, the contour seal ring 14a prepared in advance according to the parting surface is installed on the left inner mold 2a. The contour seal ring 14a is made of a rubber block and is made using 3D printing technology;

[0111] Step 4: After the outer mold 3 is connected to the supporting equipment, the prepared left inner mold 2a and right inner mold 2b are installed into the outer mold 3, and the left inner mold 2a and right inner mold 2b are subjected to mold closing inspection, which specifically includes the following steps:

[0112] Step 4-1, preliminary mold closing test: before installing the manufactured left inner mold 2a and right inner mold 2b into the outer mold 3, use the injection molded propeller model obtained by 3D printing in advance based on the three-dimensional model of the simulation cavity to place the left inner mold 2a and the right inner mold 2b on both sides of the injection molded propeller model, manually move the left inner mold 2a and the right inner mold 2b to close the mold, and use the three-coordinate measurement method to determine whether the parting surface joint of the left inner mold 2a and the right inner mold 2b is displaced, so as to complete the preliminary mold closing test;

[0113] If displacement occurs, it is first necessary to determine whether the cavity surfaces of the left inner mold 2a and the right inner mold 2b are completely fitted with the propeller model. This can be determined by visual observation and shaking the model. If the cavity surfaces of the left and right inner molds 2b are completely fitted with the propeller model, it means that the inner wall surfaces of the left and right inner molds 2b are connected without misalignment, and there is a problem in the processing of the outer wall surfaces of the left and right inner molds 2b or the contoured sealing ring 14a, which needs to be corrected until the inner and outer wall surfaces of the left and right inner molds 2a and 2b are not misaligned and the preliminary mold closing test is qualified.

[0114] Step 4-2, mold closing accuracy detection: After the preliminary mold closing detection is qualified, the left inner mold 2a and the right inner mold 2b are installed in the outer mold 3, the left inner mold 2a and the right inner mold 2b are closed, and an optical projector is used to detect whether the parting surface joint of the left inner mold 2a and the right inner mold 2b is shifted, and the mold closing accuracy detection is completed;

[0115] The optical projector only uses a light source to project and magnify the outer wall surfaces of the left and right inner molds 2b to determine whether misalignment occurs. Under the condition that the preliminary mold closing test is qualified, if the outer wall surface is misaligned, the inner wall surface is also misaligned, indicating that there is a problem with the installation position of the left and right inner molds 2b or the accuracy of the second drive guide mechanism. The faults are then eliminated one by one until the outer wall surfaces of the left and right inner molds 2b are not misaligned when the mold is closed and the mold closing accuracy test is qualified.

[0116] Step 4-3, mold sealing test: After the mold precision test is qualified, the left inner mold 2a and the right inner mold 2b are in the mold-closing state, the upper outer mold 3b and the lower outer mold 3a are in the mold-closing state, and the heat exchange medium flows into the flow channel at the first safety limit flow rate v s1 After the hot steam is injected for the first time period t1, the hot steam in the heat exchange medium flow channel is emptied, and then the heat exchange medium flow channel is filled with hot steam at a second safety limit flow rate v s2 Inject cooling water for the second time period t2, drain the cooling water in the heat exchange medium flow channel, open the upper outer mold 3b and the lower outer mold 3a, and remove the residual moisture on the outer wall of the left inner mold 2a and the right inner mold 2b to avoid adverse effects on the test results caused by residual moisture on the outer wall of the inner mold. Then open the left inner mold 2a and the right inner mold 2b to observe whether water enters the cavity of the left inner mold 2a and the right inner mold 2b.

[0117] Among them, the first safety limit flow rate v s1 The maximum flow rate of hot steam required by the injection molding process v qmax Multiply by the second safety factor σ2, where σ2 takes a value of 1.5-2. In this embodiment, σ2 takes 1.8 for calculation. According to the injection molding process requirements, the hot steam flow rate is in the range of 0.1-0.2 m / s. Therefore, the first safety limit flow rate v s1 For: v s1 =σ2v qmax =1.8×0.2=0.36m / s;

[0118] The first time period t1 is the longest hot steam injection time t required by the injection molding process. qmax According to the injection molding process requirements, the hot steam injection time is 2-5min, then t1=t qmax =5min.

[0119] The second safety limit flow rate v s2 The maximum cooling water flow rate v required by the injection molding process wmax Multiply by the third safety factor σ3, where σ3 takes a value of 1.2-1.5. In this embodiment, σ3 takes 1.4 for calculation. According to the injection molding process requirements, the cooling water flow rate is in the range of 1.2-1.6 m / s. Therefore, the second safety limit flow rate v s2 For: v s2 =σ3v wmax=1.4×1.6=2.24m / s;

[0120] The second time period t2 is the longest cooling water injection time required by the injection molding process. According to the injection molding process requirements, the cooling water injection time is 10-50 minutes, so t2=t wmax =50min.

[0121] In the above-mentioned mold sealing detection method, the injection flow rates of hot steam and cooling water used are both multiplied by a safety factor based on the maximum flow rate required by the injection molding process, thereby improving the reliability of the sealing detection.

[0122] like Fig. 9 As shown, the supporting equipment used includes an injection molding machine 15a, a water tank 15b, a refrigerator 15c, a steam generator 15d and a heat exchanger 15e, wherein:

[0123] The nozzle of the injection molding machine 15a is connected to the injection port of the outer mold 3 through the first pipeline G1, and is used to inject plastic into the cavity of the contoured inner mold 2;

[0124] The water outlet of the water tank 15b is connected to the water inlet of the refrigerator 15c through the second pipeline G2, the water outlet of the refrigerator 15c is connected to the lower fluid inlet 10b of the outer mold 3 through the third pipeline G3, the upper fluid outlet 10c of the outer mold 3 is connected to the water inlet of the water tank 15b through the sixth pipeline G6, and is connected to the water inlet of the refrigerator 15c through the seventh pipeline G7, a branch pipeline of the sixth pipeline G6, to form a cooling water circulation and recovery system;

[0125] The water outlet of the water tank 15b is connected to the water inlet of the steam generator 15d through the fourth pipeline G4, the steam outlet of the steam generator 15d is connected to the upper fluid inlet 10a of the outer mold 3 through the fifth pipeline G5, and the lower fluid outlet 10d of the outer mold 3 is connected to the steam circulation port of the steam generator 15d through the eighth pipeline G8, forming a hot steam circulation system;

[0126] The water outlet of the water tank 15b is connected to the water inlet of the heat exchanger 15e through the ninth pipeline G9, the water outlet of the heat exchanger 15e is connected to the lower fluid inlet 10b of the outer mold 3 through the tenth pipeline G10, the steam outlet of the steam generator 15d is connected to the air inlet of the heat exchanger 15e through the eleventh pipeline G11, and the air outlet of the heat exchanger 15e is connected to the steam circulation port of the steam generator 15d through the twelfth pipeline G12, forming a medium-temperature water preparation system.

[0127] The installation of pumps and valves on each pipeline is conventional technology and will not be described here.

[0128] Step 5, after the left inner mold 2a and the right inner mold 2b are qualified in the mold closing test, the left inner mold 2a and the right inner mold 2b are installed in the lower outer mold 3a for closing, the upper outer mold 3b moves down to close the mold with the lower outer mold 3a, and the steam generator 15d injects hot steam into the heat exchange medium flow channel through the fifth pipeline G5, the hot steam flow rate is 0.1-0.2m / s, the hot steam temperature is 170-180℃, the profiling inner mold 2 is heated, and the temperature of the profiling inner mold 2 is maintained at 170-190℃, when the temperature in the cavity of the profiling inner mold 2 reaches the requirement, the injection molding machine 15a injects molten plastic into the cavity through the first pipeline G1, the plastic temperature at the nozzle of the injection molding machine 15a is 220-240℃, and the plastic injection speed is 120mm / s;

[0129] Step 6, after the molten plastic is injected, the pressure is maintained. During the pressure maintenance process, the hot steam in the heat exchange medium flow channel is quickly discharged, and the discharged hot steam returns to the steam generator 15d through the eighth pipeline G8 for recovery, and then the heat exchanger 15e injects medium-temperature water into the heat exchange medium flow channel through the tenth pipeline G10 to pre-cool the contour inner mold 2. The medium-temperature water of the heat exchanger 15e is obtained by heat exchange with the hot steam injected into the heat exchanger 15e by the steam generator 15d after the water in the water tank 15b enters the heat exchanger 15e. The temperature of the medium-temperature water is 70-95°C, and the flow rate of the medium-temperature water is 1.2-1.6m / s. Then, the refrigerator 15c injects cooling water into the heat exchange medium flow channel through the third pipeline G3 to cool the contour inner mold 2. The cooling water temperature is 25-35°C, and the cooling water flow rate is 1.2-1.6m / s;

[0130] When the cooling water is injected to replace the medium-temperature water, the medium-temperature water is returned to the water tank 15b through the sixth pipeline G6 for recycling. After the medium-temperature water is replaced, the cooling water is returned to the outer mold 3 through the sixth pipeline G6, the seventh pipeline G7, and the refrigerator 15c for circulation.

[0131] Step 7: After cooling, the cooling water in the heat exchange medium flow channel is drained, and the drained cooling water enters the water tank 15b through the sixth pipeline G6. Then the upper outer mold 3b is moved open, and the right inner mold 2b is moved open to demold the plastic cooled and molded propeller injection molded part.

[0132] In the injection molding method, the profiling inner mold 2 is manufactured by combining three-dimensional modeling, strength verification and 3D printing technology, which improves the one-time success rate of the profiling inner mold 2 and effectively avoids rework and repeated production; when injecting molten plastic into the cavity, the cavity is quickly heated up by injecting high-temperature hot steam, and the temperature is maintained at a high temperature, so that the plastic maintains a good molten flow state, ensuring that the plastic can fill the entire cavity, and avoiding premature solidification of the plastic due to an overly large cavity;

[0133] During the pressure holding process, medium-temperature water is first injected for temperature transition, and finally cooling water is injected for accelerated cooling. This cooling method can, on the one hand, prevent the cooling water from directly contacting the high temperature and vaporizing, causing the pressure in the outer mold 3 to rise sharply. On the other hand, it can prevent the strength of each component from being affected by excessively rapid temperature changes in the outer mold 3, thereby extending the service life of the parts and the contoured inner mold 2. In addition, compared with high-temperature liquids, hot steam is used to heat the inner mold. On the one hand, it can be extracted more quickly and reduce contact with medium-temperature water, thereby reducing the vaporization of medium-temperature water. On the other hand, the hot steam does not need to be separated after extraction, and can be directly mixed with water for heat exchange, thereby achieving full utilization of heat energy and reducing the energy consumption required for injection molding.

[0134] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An injection mold suitable for large injection molded parts, characterized in that: include: The profiling inner mold has a simulation cavity inside, the outer surface contour of the profiling inner mold matches the contour of the cavity, and the profiling inner mold is provided with an injection port and an exhaust port; The outer mold, the contoured inner mold can be detachably installed in the outer mold, a distance is left between the outer surface of the contoured inner mold and the inner surface of the outer mold to form a heat exchange medium flow channel, an upper fluid inlet and a lower fluid inlet are opened on one side of the outer mold, and an upper fluid outlet and a lower fluid outlet are opened on the other side; The outer mold comprises a lower outer mold and an upper outer mold, a groove for accommodating the contoured inner mold is provided in the middle of the top surface of the lower outer mold, the upper outer mold is arranged above the lower outer mold, and moves up and down through a first driving guide mechanism to complete the opening and closing action with the lower outer mold; The first driving guide mechanism comprises a first driving member, an upper mold frame and a plurality of vertically arranged first guide rods, the plurality of first guide rods being dispersedly arranged at the outer edges of the top surface of the lower outer mold, the upper mold frame being arranged on the top surface of the first guide rods and supported by the first guide rods, the upper outer mold being arranged between the upper mold frame and the lower outer mold, the upper outer mold being provided with first guide holes corresponding to the first guide rods one by one, the first guide rods being movably inserted into the corresponding first guide holes, the first driving member being arranged on the top surface of the upper mold frame, the telescopic end of the first driving member passing through the upper mold frame and connected to the top surface of the upper outer mold, and driving the upper outer mold to move up and down along the first guide rods, the inner side of the first guide rods being provided on the top surface of the lower outer mold, the bottom surface of the upper outer mold being provided with a plurality of first positioning pins corresponding to the first positioning holes one by one, when the upper outer mold is moved down and molded with the lower outer mold, the first positioning pins enter into the corresponding first positioning holes; The profiling inner mold comprises a left inner mold and a right inner mold, both of which are installed in the lower outer mold, and the right inner mold is driven by the second driving guide mechanism to move horizontally to complete the opening and closing action with the left inner mold; The second driving guide mechanism comprises a second driving member, a side mold frame, a push rod, a plurality of second guide rods and a guide plate, a third guide hole is opened on the side wall of the lower outer mold, one end of the push rod passes through the third guide hole to enter the lower outer mold and is connected to the right inner mold, and the other end is connected to the guide plate, the side mold frame is vertically arranged on a side of the guide plate away from the lower outer mold, a plurality of second guide rods are scattered around the push rod, the two ends of the second guide rod are respectively connected to the lower outer mold and the side mold frame, a second guide hole corresponding to each second guide rod is opened on the guide plate, each second guide rod is movably inserted into the corresponding second guide hole, the second driving member is arranged on a side of the side mold frame away from the guide plate, the telescopic end of the second driving member passes through the side mold frame and is connected to the guide plate, and drives the guide plate to move horizontally along the second guide rod; The left inner mold and the right inner mold are respectively connected to the inner side wall of the lower outer mold and the push rod through a connecting assembly, and the connecting assembly includes a fixed shaft, a movable shaft sleeve and a limit shaft sleeve; The fixed shaft is arranged horizontally, one end of the fixed shaft is connected to the inner side wall of the lower outer mold or the end of the push rod, and the other end face of the fixed shaft extends outwardly in the axial direction to form three second positioning pins, and the three second positioning pins are distributed in an equilateral triangle, and a positioning protrusion is formed on the side wall of one of the second positioning pins extending outwardly in the radial direction, the limiting sleeve is threadedly sleeved on the outside of the fixed shaft, the movable sleeve is threadedly sleeved on the side of the limiting sleeve of the fixed shaft close to the second positioning pin, and the end of the movable sleeve away from the limiting sleeve extends outwardly in the radial direction to form a clamping block; The outer end surfaces of the left inner mold and the right inner mold are provided with positioning grooves for the second positioning pins to enter one by one, and an annular limiting groove for the clamping block to enter and rotate with the movable shaft sleeve. When the left inner mold or the right inner mold is pushed to make the second positioning pin enter the positioning groove, the clamping block enters the annular limiting groove at the same time, and then the movable shaft sleeve is rotated and tightened to tightly press the left inner mold or the right inner mold onto the fixed shaft through the clamping block, so as to realize a fixed connection between the left inner mold or the right inner mold and the fixed shaft, and finally the limiting shaft sleeve is rotated and tightened so that the end face of the limiting shaft sleeve is tightly against the end face of the movable shaft sleeve, so as to strengthen the fixation of the movable shaft sleeve; The lower outer mold is sealed and connected with the upper outer mold through a first sealing assembly when the lower outer mold is molded together. The first sealing assembly includes a first sealing ring and a second sealing ring arranged on the top surface of the lower outer mold; The first sealing ring is arranged inside the first positioning hole, the top surface of the lower outer mold and the bottom surface of the upper outer mold cooperate to form a first sealing groove, the first sealing ring is arranged in the first sealing groove, the inner side of the first sealing groove on the top surface of the lower outer mold is recessed downward to form a first horizontal step surface, the bottom surface of the upper outer mold bulges downward to form a second horizontal step surface, the first horizontal step surface and the second horizontal step surface cooperate to form a second sealing groove, and the second sealing ring is arranged in the second sealing groove; The push rod is sealed and connected to the lower outer mold through a second sealing assembly, and the second sealing assembly includes a graphite sealing ring, a third sealing ring and an oil seal; There are two graphite sealing rings, both of which are movably sleeved on the outside of the push rod and are respectively installed on the inner wall and outer wall of the lower outer mold through the sealing cover. The inner wall of the graphite sealing ring is tightly fitted with the outer wall of the push rod. A third sealing groove is opened on the hole wall of the third guide hole. The third sealing ring is arranged in the third sealing groove. A retaining ring and a retaining spring are respectively arranged on both sides of the third sealing ring. The retaining ring and the retaining spring are both installed in the third sealing groove corresponding to the third sealing ring. The inner wall of the third sealing ring bulges toward the middle to form an arc-shaped surface. The third sealing ring is deformed under the pressure of the retaining spring elastic force so that the arc-shaped surface is tightly pressed on the outer wall of the push rod. An oil seal matching groove is opened on the hole wall of the third guide hole, and the oil seal is installed in the oil seal matching groove. The limiting sleeve is sealed and connected to the fixed shaft through a third sealing assembly, the third sealing assembly includes a fourth sealing ring, an outer wall of the fixed shaft is provided with an external thread on one side close to the second positioning pin, an inner wall of the limiting sleeve is provided with an internal thread matching the external thread on one side close to the movable sleeve, a fourth sealing groove is provided on the inner wall of the limiting sleeve on the side of the internal thread away from the movable sleeve, and the fourth sealing ring is arranged in the fourth sealing groove; The left inner mold is sealed and connected with the right inner mold through the fourth sealing component when the left inner mold is closed. The fourth sealing component includes a contour sealing ring. The outer side of the parting surface of the left inner mold is concave inward along the axial direction to form a first axial step surface, and the outer side of the parting surface of the right inner mold is convex outward along the axial direction to form a second axial step surface. The first axial step surface and the second axial step surface cooperate to form a fifth sealing groove, and the contour sealing ring is arranged in the fifth sealing groove.

2. An injection molding method using the injection mold suitable for large injection molded parts according to claim 1, characterized in that: The following steps are involved: Step 1: According to the structural characteristics of the injection molded part, a three-dimensional model of the simulation cavity is established, the position of the injection parting surface is clarified, and based on the contour of the simulation cavity, an absolutely safe value is added outward as the initial wall thickness d1 to form the initial three-dimensional model of the profiling inner mold; Step 2: Take the wall thickness as a variable and the initial wall thickness d1 as the initial value of the variable, perform strength verification on the initial three-dimensional model of the contoured inner mold, and obtain the optimal safe wall thickness value d xs , then take the best safe wall thickness value d xs As the wall thickness, the final three-dimensional model of the contoured inner mold is established; Step 3: According to the final three-dimensional model of the contoured inner mold, the mold steel is used as the base, and the left inner mold and the right inner mold are respectively made by 3D printing, and the contoured sealing ring prepared in advance according to the parting surface is installed on the left inner mold; Step 4: After the outer mold is connected to the supporting equipment, the manufactured left inner mold and right inner mold are installed into the outer mold, and the left inner mold and the right inner mold are tested for mold closing; Step 5, after the left inner mold and the right inner mold are tested and qualified, the left inner mold is molded together with the right inner mold, the upper outer mold is moved down to be molded together with the lower outer mold, hot steam is injected into the heat exchange medium flow channel to heat the contour inner mold, and when the temperature in the cavity of the contour inner mold reaches the requirement, molten plastic is injected into the cavity; Step 6: After the molten plastic is injected, the pressure is maintained. During the pressure maintenance process, the hot steam in the heat exchange medium flow channel is quickly discharged, and medium-temperature water is injected into the heat exchange medium flow channel to pre-cool the contour inner mold, and then cooling water is injected into the heat exchange medium flow channel to cool the contour inner mold; Step 7: After cooling, drain the cooling water in the heat exchange medium flow channel, then move the upper outer mold to open the mold, move the right inner mold to open the mold, and demold the plastic cooled and molded injection molded part.

3. The injection molding method of the injection mold suitable for large injection molded parts according to claim 2, characterized in that: In step 2, the optimal safe wall thickness value d is obtained by strength verification. xs The method is as follows: taking the initial wall thickness d1 as the initial value, the initial three-dimensional model of the profiling inner mold is strength-checked to determine whether the initial wall thickness d1 of the profiling inner mold meets the process requirements. If so, the initial wall thickness d1 minus the fixed value D is used as the new wall thickness d2, and the newly formed three-dimensional model of the profiling inner mold is strength-checked for the second time, until the wall thickness of the i-th strength check does not meet the process requirements, and the wall thickness d at the i-1-th strength check is selected. i-1 As the optimal wall thickness value, the optimal safe wall thickness value d is calculated according to the following formula xs : d xs =σ1d i-1 Among them, σ1 is the first safety factor, and its value is 1.1-1.

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4. The injection molding method of the injection mold suitable for large injection molded parts according to claim 2, characterized in that: In step 3, when the left inner mold and the right inner mold are 3D printed, a certain size needs to be reserved on the outer end surface of the printed inner mold for processing the positioning groove and the annular limiting groove. When processing the positioning groove and the annular limiting groove, it is necessary to ensure that the distance between the bottom surface of the limiting groove and the annular limiting groove and the wall surface of the simulation cavity of the inner mold body is greater than or equal to d xs .

5. The injection molding method of the injection mold suitable for large injection molded parts according to claim 2, characterized in that: In step 4, the method for detecting the mold closing of the left inner mold and the right inner mold comprises the following steps: Step 4-1, preliminary mold closing test: before installing the manufactured left inner mold and right inner mold into the outer mold, use the injection molded part model obtained by 3D printing based on the three-dimensional model of the simulation cavity in advance, place the left inner mold and the right inner mold on both sides of the injection molded part model respectively, manually move the left inner mold and the right inner mold to close the mold, and use the three-coordinate measurement method to determine whether the parting surface joint of the left inner mold and the right inner mold is shifted, and complete the preliminary mold closing test; Step 4-2, mold closing accuracy detection: After the preliminary mold closing detection is qualified, the left inner mold and the right inner mold are installed in the outer mold, the left inner mold and the right inner mold are closed, and an optical projector is used to detect whether the parting surface joint of the left inner mold and the right inner mold is shifted, and the mold closing accuracy detection is completed; Step 4-3, mold sealing test: After the mold precision test is qualified, with the left inner mold and the right inner mold in the mold-sealed state, the upper outer mold and the lower outer mold are closed, and the heat exchange medium flows into the flow channel at the first safety limit flow rate v s1 After the hot steam is injected for the first time period t1, the hot steam in the heat exchange medium flow channel is emptied, and then the heat exchange medium flow channel is filled with hot steam at a second safety limit flow rate v s2 Inject cooling water for the second time period t2, drain the cooling water in the heat exchange medium flow channel, open the upper outer mold and the lower outer mold, remove residual water on the outer walls of the left inner mold and the right inner mold, open the left inner mold and the right inner mold, and observe whether water enters the cavity of the left inner mold and the right inner mold.

6. The injection molding method of the injection mold suitable for large injection molded parts according to claim 5, characterized in that: The first safety limit flow rate v s1 The calculation formula is: s1 =σ2v qmax ; Among them, v qmax is the maximum flow rate of hot steam required by the injection molding process, σ2 is the second safety factor, and the value is 1.5-2; The calculation formula for the first time period t1 is: t1=t qmax ; Among them, t qmax The longest hot steam injection time required for the injection molding process; The second safety limit flow rate v s2 The calculation formula is: s2 =σ3v wmax ; Among them, v wmax is the maximum flow rate of cooling water required by the injection molding process, σ3 is the third safety factor, and its value is 1.2-1.5; The calculation formula for the second time period t2 is: t2=t wmax ; Among them, t wmax The longest cooling water injection time required by the injection molding process.

7. The injection molding method of the injection mold suitable for large injection molded parts according to claim 2, characterized in that: The supporting equipment includes an injection molding machine, a water tank, a refrigerator, a steam generator and a heat exchanger; The nozzle opening of the injection molding machine is connected to the injection molding port of the outer mold through a first pipeline; The water outlet of the water tank is connected to the water inlet of the refrigerator through the second pipeline, the water outlet of the refrigerator is connected to the lower fluid inlet of the outer mold through the third pipeline, the upper fluid outlet of the outer mold is connected to the water inlet of the water tank through the sixth pipeline, and is connected to the water inlet of the refrigerator through the seventh pipeline, which is a branch pipeline of the sixth pipeline; The water outlet of the water tank is connected to the water inlet of the steam generator through a fourth pipeline, the steam outlet of the steam generator is connected to the upper fluid inlet of the outer mold through a fifth pipeline, and the lower fluid outlet of the outer mold is connected to the steam circulation port of the steam generator through an eighth pipeline; The water outlet of the water tank is connected to the water inlet of the heat exchanger through the ninth pipeline, the water outlet of the heat exchanger is connected to the lower fluid inlet of the outer mold through the tenth pipeline, the steam outlet of the steam generator is connected to the air inlet of the heat exchanger through the eleventh pipeline, and the air outlet of the heat exchanger is connected to the steam circulation port of the steam generator through the twelfth pipeline.

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