casting mold

Abstract

The present application relates to the technical fields of epoxy sheet manufacturing, and particularly relates to a pouring mold, which comprises a mold body and a negative pressure generating unit, the mold body is provided with a cavity and a liquid storage cavity which are communicated along the up-down direction, and the negative pressure generating unit is communicated with the cavity to generate negative pressure in the cavity. Its beneficial effects are that the cavity can maintain the shape of the epoxy resin and help the epoxy resin to form; the liquid storage cavity can store the liquefied epoxy resin, and when the negative pressure generating unit generates negative pressure on the cavity, the epoxy resin in the liquid storage cavity can be adsorbed into the cavity to help the epoxy resin to form and reduce the bubbles generated during pouring.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin sheet manufacturing technology, and in particular to a casting mold. Background Technology

[0002] Epoxy resin insulating materials are functional materials with electrical insulation properties, formed by cross-linking and curing a matrix resin containing epoxy groups. Due to their excellent dielectric properties, good stability, and many other advantages, they not only hold an important position in the electrical industry but also have wide applications in various fields such as medicine, aerospace, civil engineering, rail vehicles, and integrated electronic products.

[0003] To ensure the excellent performance of epoxy resin, both formulation design and the casting and curing process are crucial. In the casting and curing process, the casting mold is indispensable. For the preparation of sheet-type epoxy resin products, the small mold cavity makes it difficult to fully inject the resin, resulting in poor casting effect and defects such as air bubbles in the cured product, severely affecting product performance. Furthermore, the design of casting molds often focuses on molding rather than process considerations, making it difficult to control the product defect rate. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing mold casting effect is not good, and the solidified product is prone to defects such as air bubbles.

[0005] To solve the above-mentioned technical problems, the present invention provides a casting mold, including a mold body and a negative pressure generating unit. The mold body has a cavity and a liquid storage cavity connected in the vertical direction. The negative pressure generating unit is connected to the cavity to generate negative pressure in the cavity.

[0006] In the above technical solution, the mold body includes a first body and a second body. The first body has a cavity extending through its upper and lower ends, and the second body has a liquid storage cavity. The second body is detachably installed at the lower end of the first body, and the negative pressure generating unit communicates with the cavity through the upper end of the first body.

[0007] In the above technical solution, the second body is made of silicone rubber material.

[0008] In the above technical solution, the negative pressure generating unit includes a vacuum pump and a filter unit, and the vacuum pump is connected to the cavity through the filter unit.

[0009] In the above technical solution, the filtration unit includes a vacuum filter and an air guide tube, and the vacuum pump, the vacuum filter, the air guide tube and the cavity are connected in sequence.

[0010] In the above technical solution, the upper end of the first body is provided with an extension, a part of the cavity is opened in the extension, and the air guide tube is connected to the cavity through the extension.

[0011] In the above technical solution, the gas guide tube is a transparent steel wire reinforced vacuum tube.

[0012] In the above technical solution, the vacuum filter is a pipeline vacuum filter.

[0013] In the above technical solution, the vacuum pump is a rotary vane vacuum pump.

[0014] In the above technical solution, the air guide tube is a transparent air guide tube.

[0015] Compared with the prior art, the casting mold of the present invention has the following advantages: the cavity can maintain the shape of the epoxy resin and help the epoxy resin to form; the liquid storage cavity can store liquefied epoxy resin. When the negative pressure generating unit generates negative pressure on the cavity, it can adsorb the epoxy resin in the liquid storage cavity into the cavity to help the epoxy resin to form and reduce the bubbles generated during casting. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the casting mold according to an embodiment of the present invention; In the figure, 1 is the first body; 2 is the second body; 3 is the cavity; 4 is the extension; 5 is the air guide tube; 6 is the vacuum filter; 7 is the vacuum pump; and 8 is the liquid storage chamber. Detailed Implementation

[0017] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "inner," and "outer," etc., used in this invention to indicate the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0019] In the description of this invention, it should be understood that the terms "connected," "linked," and "fixed," etc., used in this invention should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or a welded connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly defined. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0020] like Figure 1 As shown, a preferred embodiment of the present invention provides a casting mold, which includes a mold body and a negative pressure generating unit. The mold body has a cavity 3 and a liquid storage cavity 8 connected in the vertical direction. The negative pressure generating unit is connected to the cavity 3 to generate negative pressure in the cavity 3.

[0021] Cavity 3 can maintain the shape of epoxy resin and help epoxy resin to form; liquid storage cavity 8 can store liquefied epoxy resin. When the negative pressure generating unit generates negative pressure on cavity 3, it can adsorb the epoxy resin in liquid storage cavity 8 into cavity 3 to help epoxy resin form and reduce air bubbles generated during casting.

[0022] Furthermore, the mold body includes a first body 1 and a second body 2. The first body 1 has a cavity 3 extending through its upper and lower ends, and the second body 2 has a liquid storage cavity 8. The second body 2 is detachably installed at the lower end of the first body 1, and the negative pressure generating unit is connected to the cavity 3 through the upper end of the first body 1.

[0023] It is understandable that the first body 1 has a cavity 3 extending through its upper and lower ends, so that the negative pressure generating unit and the liquid storage cavity 8 can be connected to the cavity 3 at the upper end and the lower end of the first body 1, respectively, to prevent the negative pressure generating unit from directly adsorbing epoxy resin without passing through the cavity 3, and to prevent the cavity 3 from not being filled with epoxy resin.

[0024] Preferably, the second body 2 is made of silicone rubber material to facilitate later disassembly for sealing the cavity 3.

[0025] Furthermore, the negative pressure generating unit includes a vacuum pump 7 and a filter unit, with the vacuum pump 7 connected to the cavity 3 through the filter unit.

[0026] Understandably, the vacuum pump 7 is used to generate negative pressure, and the filter unit can intercept the epoxy resin in the cavity 3 to prevent the epoxy resin from entering the vacuum pump 7.

[0027] Furthermore, the filtration unit includes a vacuum filter 6 and an air guide pipe 5, and the vacuum pump 7, vacuum filter 6, air guide pipe 5 and cavity 3 are connected in sequence.

[0028] Understandably, staff can roughly determine the epoxy resin filling status inside cavity 3 through air duct 5, and decide whether to turn off vacuum pump 7 based on the filling status.

[0029] Furthermore, the upper end of the first body 1 is provided with an extension 4, a part of the cavity 3 is opened in the extension 4, and the air guide tube 5 is connected to the cavity 3 through the extension 4.

[0030] Understandably, the extension 4 can provide a fixed position for the air guide tube 5, which is beneficial for the air guide tube 5 to connect the cavity 3 and the vacuum filter 6.

[0031] Preferably, the air duct 5 is a transparent air duct, so as to facilitate the staff to judge the epoxy resin filling status in the cavity 3.

[0032] Preferably, the gas guide tube 5 is a transparent steel wire reinforced vacuum tube.

[0033] Preferably, the vacuum filter 6 is a pipeline vacuum filter.

[0034] Preferably, the vacuum pump 7 is a rotary vane vacuum pump.

[0035] The working process of this invention is as follows: After the epoxy resin casting material is prepared, it is injected into the storage cavity. During the entire injection process, it is necessary to ensure that the level of the casting material is higher than the bottom of the mold. The vacuum pump 7 is turned on, and the mold cavity is evacuated through the air hole, the air guide pipe 5 and the vacuum filter 6, so that the epoxy resin in the storage cavity is injected into the mold smoothly. When the mold is filled and the casting material overflows from the air guide pipe 5, the vacuum pump 7 is turned off, the bottom of the mold is cleaned and the lower end of the cavity 3 is sealed.

[0036] In summary, the present invention provides a casting mold in which the cavity 3 can maintain the shape of the epoxy resin and help the epoxy resin to form; the liquid storage cavity 8 can store liquefied epoxy resin. When the negative pressure generating unit generates negative pressure on the cavity 3, the epoxy resin in the liquid storage cavity 8 can be adsorbed into the cavity 3 to help the epoxy resin to form and reduce the bubbles generated during casting.

[0037] Because epoxy resin and aluminum alloy have essentially the same coefficient of thermal expansion, and since these molds are mainly used in vacuum casting processes, which are largely done manually, aluminum alloy was chosen for ease of handling. However, due to the low hardness of the material, a hard anodizing treatment was applied to the surface, resulting in an oxide layer depth of 50μm and a surface hardness of 400–500 HV, thus improving the mold's wear resistance and corrosion resistance. For parts that are frequently disassembled during mold opening and closing, steel or copper components were used, minimizing damage during assembly and disassembly and extending the mold's service life.

[0038] Gating system design: The dimensions of the main flow channel, branch flow channels, and point bends were calculated, as these three components are closely related to the shear rate of the melt. The values ​​for each component are as follows: For the mainstream approach, take ; For the branch channel, take

[0039] For point-to-point tongue twisting, take

[0040] Mainstream track size From the shear rate equation of materials rheology, the diameter of the main channel can be obtained as:

[0041] In the formula: Q—the volumetric flow rate of the plastic flame, which is determined by the volume of the plastic part and the injection time; n—the non-Newtonian index of the melt, which is related to the melt temperature and shear rate.

[0042] Based on materials rheology and its shear rate equation, the channel diameter can be calculated as follows:

[0043] or

[0044] Gate size:

[0045] This invention employs a balanced arrangement of runners; otherwise, the dimensions of the gating nozzles need to be adjusted to ensure consistent flow rates and molding process conditions across all nozzles—this is the balance of the gating system. Generally, the ratio of the cross-sectional area of ​​the gating nozzle to the cross-sectional area of ​​the runner is 0.07-0.09. When the gate length is constant, the width and depth can be varied. Generally, a ratio of width W to depth H of approximately 3:1 is preferable.

[0046]

[0047] In the formula: SG is the cross-sectional area of ​​the gate, LR is the length of the runner, and LG is the length of the gate.

[0048] The cross-sectional shape of the flow channel is generally circular, trapezoidal, U-shaped, semi-circular, or rectangular. Trapezoidal cross-sections are commonly used in engineering design due to their good manufacturability and low heat dissipation and flow resistance of the molten plastic. The following empirical formula can generally be used to determine its cross-sectional dimensions:

[0049] In the formula, B is the width of the large base of the trapezoid (mm); a is the weight of the plastic part (g); L is the length of the runner (mm); and H is the height of the trapezoid (mm).

[0050] Average shrinkage rate method Based on the statistical laws governing mold manufacturing deviations and deviations caused by plastic part shrinkage, this statistical law shows that both mold manufacturing deviations and deviations caused by plastic part shrinkage follow a normal distribution. The probability of them taking the average value is the highest, while the probability of taking the maximum or minimum value is close to zero. If we further assume that the molding shrinkage rate of the plastic part, the manufacturing deviation of the working dimensions of the molded parts, and their wear are equal to their respective average values, then the dimensional deviations of the plastic part can also be obtained at their average values. Therefore, a series of calculation formulas for various dimensions such as cavities, cores, and center distances can be derived.

[0051] Taking the inner diameter of a cavity as an example, the outer surface of the molded plastic part is shown in the following figure: The cavity is a hole, and the plastic part is a shaft. The average dimensions of the outer and inner diameters of the plastic part are as follows:

[0052] Simplify the above equation and ignore the second-order minor quantity Δ / 2×S CP Then we have:

[0053] After specifying manufacturing tolerances, we have:

[0054] In the formula, L M —The radial working dimension of the cavity; L S —Radial dimensions of the plastic part; S CP —The average shrinkage rate; Δ — Dimensional tolerance of the plastic part; δ Z — Cavity manufacturing tolerances; δ C —Maximum allowable wear of the cavity; Similarly, the radial dimensions of the core, the depth dimensions of the cavity, the height dimensions of the core, and the center distance dimensions can be derived.

[0055] This invention effectively improves existing epoxy resin casting molds by using polishing technology to enhance the accuracy of the mold cavity dimensions and improve the surface fineness of the mold, thereby ensuring the safe use of high-voltage electrical appliances.

[0056] In epoxy resin casting, various compound materials, epoxy resin, and curing agents are simultaneously poured into a fixed mold, transforming the thermosetting fluid into a thermosetting solid to form the finished product. During the epoxy casting of insulating products, it is necessary to maintain a high level of aesthetic appeal and dimensional stability. With the increasing variety of high-voltage electrical appliances, the requirements for the quality and lifespan of epoxy resin casting molds are constantly rising. To effectively improve the quality and extend the lifespan of epoxy resin casting molds, the polishing requirements need to be appropriately enhanced to ensure the flatness and smoothness of the mold surface. For the polishing of epoxy resin wheel rim casting molds, the polishing process is somewhat similar to mirror polishing, primarily using mechanical polishing methods.

[0057] In this invention, the epoxy resin rim casting mold is first rough-polished. Generally, after precision milling, to effectively ensure the flatness of the epoxy resin rim casting mold surface, polishing with a grinding wheel is necessary. To improve the polishing effect, the polishing machine used needs to be properly specified; ideally, a polishing machine with a speed of 3500-40000 r / min should be selected to hold the abrasive wheel, resulting in a more prominent polishing effect. After rough polishing with the abrasive wheel, the polished texture of the epoxy resin rim casting mold surface is clearly visible. At this point, fine polishing is required for further polishing. During fine polishing, a polishing machine is also needed to hold the abrasive wheel to ensure the polishing effect. There are some narrow spaces within the mold. When dealing with these narrow spaces, an oilstone can be used as the polishing tool, with kerosene as a lubricant, to ensure the polishing effect of these narrow spaces.

[0058] Secondly, the epoxy resin rim casting mold needs to undergo semi-finish polishing. This polishing process uses sandpaper and kerosene as a lubricant to enhance the polishing effect. The sandpaper must be applied in a specific order. Generally, 1500# sandpaper is only suitable for mold steel with a hardness of 52HRC or higher; it is not suitable for pre-hardened steel. Using such high-hardness sandpaper on pre-hardened steel will severely damage the surface, significantly reducing the polishing effect. Finally, fine polishing. The main tools for fine polishing are diamond polishing paste and polishing cloth wheels. If using a polishing cloth wheel mixed with diamond polishing powder or paste, the typical polishing sequence is: 9µm (1800#), 6µm (3000#), 3µm (8000#).

[0059] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and substitutions without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A casting mold, characterized in that, It includes a mold body and a negative pressure generating unit. The mold body has a cavity and a liquid storage cavity connected in the vertical direction. The negative pressure generating unit is connected to the cavity to generate negative pressure in the cavity. The mold body includes a first body and a second body. The first body has a cavity extending through its upper and lower ends. The second body has a liquid storage cavity. The second body is detachably installed at the lower end of the first body. The negative pressure generating unit communicates with the cavity through the upper end of the first body. The second body is made of silicone rubber and can seal the cavity.

2. The casting mold according to claim 1, characterized in that, The negative pressure generating unit includes a vacuum pump and a filter unit, and the vacuum pump is connected to the cavity through the filter unit.

3. The casting mold according to claim 2, characterized in that, The filtration unit includes a vacuum filter and an air guide tube, and the vacuum pump, the vacuum filter, the air guide tube and the cavity are connected in sequence.

4. The casting mold according to claim 3, characterized in that, The upper end of the first body is provided with an extension, a part of the cavity is opened in the extension, and the air guide tube communicates with the cavity through the extension.

5. The casting mold according to claim 4, characterized in that, The gas delivery tube is a transparent steel wire reinforced vacuum tube.

6. The casting mold according to claim 4, characterized in that, The vacuum filter is a pipeline vacuum filter.

7. The casting mold according to claim 4, characterized in that, The vacuum pump is a rotary vane vacuum pump.

8. The casting mold according to any one of claims 4 to 7, characterized in that, The air duct is a transparent air duct.

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