An induction heating device for thermoset plastic molding

Abstract

The utility model discloses an inductive heating device for thermosetting plastic forming processing belongs to thermosetting plastic forming processing field. The device includes heating coil, solidification ring, magnetic core and apron subassembly. Heating coil is formed by hollow metal pipe winding, and its inside constitutes heat management medium runner, solidification ring is by high temperature resistant castable casting and will heating coil encapsulation in, magnetic core is around in solidification ring outside, apron subassembly is through connecting piece and is clamped fixed above -mentioned part. The utility model through magnetic core restraint and strengthen alternating field, and carry out temperature control to coil in combination with heat management medium runner, solved traditional heating device temperature control precision difference, cannot continuous use, preheating process cumbersome problem, realized to thermosetting plastic's quick, even heating, improved production efficiency and product yield rate significantly.

Description

Technical Field

[0001] This utility model belongs to the field of thermosetting plastic molding and processing technology, specifically relating to an induction heating device for rapidly and precisely heating and melting thermosetting plastics during injection molding or compression molding. Background Technology

[0002] Thermosetting plastics (such as phenolic plastics, epoxy plastics, and phenyl molding plastics) require heating and melting, injection into a closed mold cavity, and cooling and solidification during the molding process to form the final product. The heating process is crucial; its efficiency and the precision of temperature control directly affect the material's flowability and subsequent curing quality, ultimately determining the product's mechanical strength, insulation properties, and lifespan. Currently, traditional processing often uses hot plate conduction heating devices, which have the following main drawbacks:

[0003] 1. Poor temperature control accuracy and unstable product quality: Traditional heating devices have high thermal inertia, resulting in inaccurate temperature control and temperature fluctuations often exceeding ±15℃. This excessive deviation makes it difficult to control the material curing reaction at its optimal state, directly causing the molded parts to fail to meet mechanical properties (such as impact strength) and electrical properties (such as insulation and breakdown strength). Moreover, these defects are difficult to detect in this process, leading to a large number of defective products in subsequent tests.

[0004] Second, the preheating process is cumbersome and the production efficiency is low: In order to reduce thermal shock and ensure that the material is fully melted, the traditional process requires the plastic raw material to be preheated to 200°C and kept at that temperature for up to two hours. At the same time, the heating device itself also needs to be preheated to 250°C and then cooled down to the working temperature. The whole preheating process is time-consuming and energy-intensive, which seriously restricts the production cycle and efficiency.

[0005] 3. Inability to operate continuously and stably, resulting in low yield: Due to heat accumulation and heat dissipation issues, traditional heating devices are difficult to operate continuously. Temperature stability deteriorates further during mass production, directly leading to poor product consistency, an overall yield of less than 60%, and high production costs. Utility Model Content

[0006] The purpose of this invention is to solve the problems of low product qualification rate and low production efficiency caused by poor temperature control accuracy of heating devices, cumbersome preheating process and inability to operate continuously and stably in existing thermosetting plastic molding processes. The invention proposes a heating device based on the principle of electromagnetic induction, which has the ability to respond quickly, control temperature accurately and operate continuously.

[0007] To achieve the above objectives, the technical solution provided by this utility model is as follows:

[0008] An induction heating device for thermosetting plastic molding is provided, comprising a heating coil, a curing ring, a magnetic core, and a cover plate assembly;

[0009] The heating coil is made of a hollow metal tube, which forms a heat management medium flow channel for circulating the medium to achieve temperature cyclic control of the heating coil; the heating coil is used to generate an alternating magnetic field when energized to inductively heat the thermosetting plastic placed inside it.

[0010] The curing ring is cast from a high-temperature resistant casting material and encapsulates the heating coil inside, providing structural support, electrical insulation, and thermal protection.

[0011] The magnetic core is made of magnetically conductive material and surrounds the outside of the solidified ring to confine and enhance the alternating magnetic field;

[0012] The cover plate assembly includes an upper cover plate and a lower cover plate. The upper cover plate and the lower cover plate clamp and fix the magnetic core, curing ring and heating coil through connectors to form an integral structure.

[0013] Furthermore, the heating coil has a double-layer winding structure with 4 turns in the inner layer and 4 turns in the outer layer.

[0014] Furthermore, the heating coil is made of T2 copper tubing with a diameter of 10mm and a wall thickness of 1.5mm.

[0015] Furthermore, the heating coil is provided with a high-temperature resistant insulating sleeve between the turns, which has a temperature resistance of not less than 600℃.

[0016] Furthermore, the magnetic core is assembled from silicon steel sheets to form a cylindrical structure.

[0017] Furthermore, the silicon steel sheet is 66mm long and 11mm wide, and the magnetic core is surrounded by a clip with a width of 6mm.

[0018] Furthermore, the high-temperature resistant casting material is an aluminate cement-based composite material with a temperature resistance of not less than 1600℃ and a compressive strength of not less than 60 MPa.

[0019] Furthermore, the connecting components are bolts and mating nuts.

[0020] Furthermore, the overall shape of the device is cylindrical, with an inner diameter of 72mm, an outer diameter of 100mm, and a height of 55mm.

[0021] Furthermore, the lead-out length of the heating coil is 120mm.

[0022] The advantages of this utility model are:

[0023] 1. The induction heating device for thermosetting plastic molding provided by this utility model effectively constrains and enhances the magnetic field through the magnetic core, and combines the precise temperature control of the heating coil through the thermal management medium flow channel, thereby achieving highly precise management of the heating process of thermosetting plastic. The temperature fluctuation range is much lower than ±15℃ of the traditional device, thus ensuring the full and uniform curing reaction of the material, enabling the molded parts to reliably meet the stringent requirements of subsequent impact, insulation, breakdown and life tests, and thus greatly improving the first-pass yield of the products.

[0024] 2. Based on the principle of induction heating and optimized structural design, this device has low thermal inertia and rapid response. Materials only need to be preheated from room temperature to 170°C before use, which completely eliminates the cumbersome process of long-term heat preservation of raw materials and preheating of the equipment itself in traditional processes, significantly shortening the production cycle and reducing time and energy costs.

[0025] 3. The unique composite structure of the "heating coil-curing ring-magnetic core" of this utility model works synergistically with the efficient cooling circulation system to ensure that the device can dissipate its own resistance heat and process waste heat in a timely manner, thereby achieving stable and reliable continuous operation capability. It has been verified that it can continuously process more than 7 parts without performance degradation.

[0026] 4. Through precise temperature control, simplified production process, and comprehensive improvement in continuous operation capability, this device directly leads to a significant increase in the yield of the final product. Trial production results show that the yield has steadily increased from less than 60% in the traditional method to over 85%.

[0027] 5. The curing ring, integrally cast with high-temperature resistant castable, provides solid mechanical support, reliable electrical insulation, and excellent thermal protection for the internal coil, enabling the device to withstand severe thermal shocks. It has explosion-proof, crack-proof, and detachment-proof characteristics, and the overall structure is robust, significantly extending its service life. Attached Figure Description

[0028] The above and / or other features and advantages of the present invention will become more readily understood from the following description with reference to the accompanying drawings, which are not drawn to scale and some features are enlarged or reduced to show details of specific parts.

[0029] Figure 1 This is a perspective view of the overall shape of the induction heating device for thermosetting plastic molding process according to this utility model.

[0030] Figure 2 This is a cross-sectional view of the induction heating device of this utility model;

[0031] Figure 3 This is an exploded view of the assembly of the induction heating device of this utility model;

[0032] Figure 4 This is a schematic diagram of the heating coil structure in this utility model;

[0033] Figure 5 This is a schematic diagram of the curing ring in this utility model;

[0034] Figure 6 This is a schematic diagram of a single silicon steel sheet that makes up the magnetic core in this utility model;

[0035] Figure 7 This is a schematic diagram of the structure of the upper cover plate in this utility model;

[0036] Figure 8 This is a schematic diagram of the structure of the lower cover plate in this utility model.

[0037] In the diagram: 1-Heating coil; 2-Curing ring; 3-Magnetic core; 31-Silicon steel sheet; 4-Upper cover plate; 5-Lower cover plate; 6-Bolt; 7-Nut; 100-Workpiece to be processed; 200-Push rod. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and exemplary embodiments thereof. It should be noted that the following detailed description of the present invention is for illustrative purposes only and is not intended to limit the scope of the invention.

[0039] It should be noted that, in the context of this utility model, the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not 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 limitations on this utility model.

[0040] First, the overall reference Figure 1 The figure shows a perspective view of the overall shape of an induction heating device for thermosetting plastic molding, as an exemplary embodiment of the present invention. As shown, in this embodiment, the device has a compact cylindrical structure with the following main body dimensions: inner diameter 72mm, outer diameter 100mm, and height 55mm. The components are tightly integrated, facilitating installation and use on injection molding equipment. This device is particularly suitable for the process of injecting phenyl-modified plastic into molded parts after three cycles of heating and cooling to achieve melting.

[0041] Combination Figure 2 and Figure 3The induction heating device includes a heating coil 1, a curing ring 2, and a magnetic core 3. The entire structure is clamped and fixed by an upper cover plate 4 and a lower cover plate 5 through connectors, forming a robust whole. The workpiece 100 being processed is located inside the device cavity. In this embodiment, the connectors consist of bolts 6 and nuts 7, but this is only an example and not a limitation. Provided that reliable clamping and fixing functions are ensured, the connectors for the cover plate assembly in this invention are not limited to bolts 6 and nuts 7. Those skilled in the art can adopt other common mechanical fastening methods based on actual installation space, disassembly frequency, and cost considerations. For example, a specialized snap-on quick-release mechanism can be designed to achieve rapid locking and separation of the upper and lower cover plates through specific snap-fit ​​points.

[0042] Reference Figure 4 The heating coil 1 is made of a hollow metal tube, with its main body being T2 copper tubing, measuring 10mm in diameter and 1.5mm in wall thickness. The heating coil 1 employs a double-layer tightly wound structure, with 4 turns in the inner layer and 4 turns in the outer layer, and the lead-out length of the coil winding is 120mm. High-temperature resistant insulating sleeves are installed between the turns of the heating coil 1, with a temperature resistance rating of up to 600℃, effectively preventing short circuits between turns. When high-frequency alternating current is applied, the coil generates a strong alternating magnetic field, inducing eddy currents and generating heat inside the workpiece 100 (thermosetting plastic) placed within its cavity, thus achieving induction heating. The hollow metal tube forms a heat management medium flow channel, allowing the flow of a medium such as water to circulate and control the temperature of the coil during operation. Specifically, this involves cyclically heating and cooling the coil to ultimately maintain a stable temperature.

[0043] Reference Figure 5 The curing ring 2 is cast from a known high-temperature resistant casting material, encapsulating and curing the heating coil 1 within it. In this embodiment, the high-temperature resistant casting material is an aluminate cement-based composite material conforming to GB / T2997 standards, specifically using A900 aluminate cement as a binder, mixed with high-quality high-alumina aggregate and ultrafine powder. This material has the following characteristics: temperature resistance up to 1600℃, compressive strength not less than 60 MPa, and also features explosion-proof, crack-proof, and detachment-proof properties. The curing ring 2 provides triple protection: structural support, electrical insulation, and thermal protection, ensuring long-term reliable operation of the device in high-temperature environments. Two through holes are provided on the side wall of the curing ring 2, for the two ends of the heating coil 1 to pass through. This design not only provides a fixed channel for the coil leads but also ensures accurate lead positioning, preventing damage due to movement during assembly and use.

[0044] Combination Figure 6The magnetic core 3 is assembled from multiple silicon steel sheets as shown in the diagram, and is cylindrical in shape. The silicon steel sheets are 66mm long and 11mm wide. A 6mm wide clamp is provided around the magnetic core 3 to constrain the silicon steel sheets and provide a clamping force point. These silicon steel sheets have high permeability, which effectively constrains and enhances the alternating magnetic field, forcing the magnetic field to concentrate through the heating area and significantly improving heating efficiency.

[0045] Reference Figure 7 and Figure 8 The diagram illustrates the structure of the upper cover plate 4 and the lower cover plate 5. These two cover plates provide strong clamping force via bolts 6 and nuts 7, ensuring a tight fit between the components and maintaining the stability of the magnetic circuit structure. Notably, both the upper cover plate 4 and the lower cover plate 5 have a central hole, the diameter of which corresponds to the inner diameter of the heating coil 1, together forming the heating chamber of the device. The central hole in the upper cover plate 4 is used to insert the workpiece 100, while the central hole in the lower cover plate 5 is used for the passage of the injection molding machine ejector pin 200, enabling the workpiece 100 to be placed on the ejector pin 200 and for injecting molten plastic into the mold after heating.

[0046] Return to reference Figure 2 and Figure 3 The specific manufacturing process of the device provided by this utility model is as follows:

[0047] First, the heating coil 1 is fabricated: A T2 copper tube is wound into a double-layered, tightly wound coil body (4 turns inside and 4 turns outside), and water and electrical connection components are welded on. Silver-copper alloy brazing is used during welding, and the coil leads are wrapped with a damp cloth to prevent damage to the insulating sleeve. After welding, a special high-temperature wrapping tape is used to reinforce the insulation of the coil leads.

[0048] Next, the magnetic core 3 is assembled: the cylindrical magnetic core 3 made of silicon steel sheets is assembled on the lower cover plate 5 to ensure that the assembly is flat and tight.

[0049] Then, the curing ring 2 is cast and molded: This process consists of the following steps:

[0050] 1) Lay an 8mm thick high-temperature resistant castable pad at the coil installation position on the lower cover plate 5;

[0051] 2) Place the prepared heating coil 1 in, ensuring that the gap between the coil and the inner wall of the magnetic core 3 remains uniform;

[0052] 3) Pour the high-temperature resistant casting material, which has been prepared into a thick paste, into the gap between the coil and the iron core, and tamp it down with a bamboo stick;

[0053] 4) Use high-temperature resistant castable to cover the upper part of the coil, with the covered surface extending 5mm above the iron core;

[0054] 5) Cover the top cover plate 4 and clamp it with bolts 6 and nuts 7;

[0055] 6) Apply the same casting material to the inner wall of the coil, spread it evenly and smooth it out, so that the coating thickness at the edge of the coil tube reaches 2mm.

[0056] Finally, a curing process is performed: the coil is left to dry at room temperature for 36-48 hours to complete the hydration reaction; then it is placed in an oven and heated in stages to evaporate the moisture, first at 45-50℃ for 12 hours, and then at 100-120℃ for 24 hours. After drying, the insulation between the coil and the clamp and the iron core is measured to ensure that the resistance is greater than 200MΩ. Finally, the entire coil is cleaned and blown clean with compressed air.

[0057] The working process of this utility model is as follows:

[0058] Step 1, Raw Material Preparation and Loading: 3-3.3g of synthetic resin powder is die-cast into a cylindrical shape under a pressure of 10MPa to form the workpiece 100. The entire heating device is placed on the injection molding machine, ensuring the ejector pin 200 is raised so that its top end passes through the center hole of the lower cover plate 5 and slightly protrudes from the cavity. Then, the operator or automated loading mechanism inserts the workpiece 100 through the center hole of the upper cover plate 4, placing it directly on the top plane of the ejector pin 200. After placement, the ejector pin 200 can be slightly retracted or held in its current position, ensuring the workpiece 100 is stably centered within the heating cavity enclosed by the inner wall of the heating coil 1.

[0059] Step 2, Equipment Start-up: After the workpiece loading is completed, connect the cooling circulating water and high-frequency power supply of heating coil 1.

[0060] Step 3, Heating-Cooling Cycle: The equipment control program is activated, and the device automatically executes the preset "heating-cooling" cycle. Specifically, it starts heating from room temperature to 294°C, then disconnects the heating, cools down from 294°C to 200°C, then heats up from 200°C to 294°C again, then disconnects the heating, cools down from 294°C to 200°C, and finally heats up from 200°C to 294°C again. During this process, the heating coil 1 generates an alternating magnetic field to inductively heat the workpiece 100, causing it to gradually melt.

[0061] Step 4, Injection Molding: When the workpiece 100 is heated to its final molten state, the injection molding machine control system issues a command to drive the ejector pin 200 to move upward. The ejector pin 200 passes through the center hole of the lower cover plate 5 and acts precisely on the molten plastic, injecting it under high pressure into the mold cavity (not shown in the figure) located above the device, completing the molding process (this heating to injection process takes about 40 minutes).

[0062] Step 5, Cooling and Part Removal: After injection, the device enters the cooling stage. Once the temperature drops to room temperature, the mold is removed and the molded part is taken out, thus completing one processing cycle.

[0063] After trial production and verification, this device can maintain stable performance even after processing seven parts continuously. With this device, materials can be used after preheating from room temperature to 170℃, eliminating the cumbersome process of preheating raw materials to 200℃ and maintaining it for two hours as in traditional processes; the equipment coils do not require preheating and can process normally at room temperature; the product yield rate has been significantly increased from less than 60% with traditional methods to over 85%, effectively solving problems such as poor temperature control accuracy, inability to use continuously, and cumbersome preheating required by traditional heating devices.

[0064] Finally, it should be noted that the features mentioned and / or shown in the above description of exemplary embodiments of the present invention can be combined in the same or similar manner with one or more other embodiments, combined with features in other embodiments, or substituted for corresponding features in other embodiments. These combined or substituted technical solutions should also be considered as included within the protection scope of the present invention.

Claims

1. An induction heating device for thermosetting plastic molding, characterized in that: Includes heating coil, curing ring, magnetic core and cover plate assembly; The heating coil is made of a hollow metal tube, which forms a heat management medium flow channel for circulating medium to achieve temperature cyclic control of the heating coil; the heating coil is used to generate an alternating magnetic field when energized to inductively heat the thermosetting plastic placed inside it. The curing ring is cast from a high-temperature resistant casting material and encapsulates the heating coil inside, providing structural support, electrical insulation and thermal protection. The magnetic core is made of magnetically conductive material and surrounds the outside of the solidified ring to constrain and enhance the alternating magnetic field; The cover plate assembly includes an upper cover plate and a lower cover plate. The upper cover plate and the lower cover plate clamp and fix the magnetic core, the curing ring and the heating coil through a connector to form an integral structure.

2. The induction heating device according to claim 1, characterized in that: The heating coil has a double-layer winding structure with 4 turns in the inner layer and 4 turns in the outer layer.

3. The induction heating device according to claim 1 or 2, characterized in that: The heating coil is made of T2 copper tubing with a diameter of 10mm and a wall thickness of 1.5mm.

4. The induction heating device according to claim 2, characterized in that: The heating coil is provided with a high-temperature resistant insulating sleeve between its turns, which has a temperature resistance of not less than 600℃.

5. The induction heating device according to claim 1 or 2, characterized in that: The magnetic core is assembled from silicon steel sheets to form a cylindrical structure.

6. The induction heating device according to claim 5, characterized in that: The silicon steel sheet is 66mm long and 11mm wide, and the magnetic core is surrounded by a clip with a width of 6mm.

7. The induction heating device according to claim 1 or 2, characterized in that: The high-temperature resistant casting material is an aluminate cement-based composite material with a temperature resistance of not less than 1600℃ and a compressive strength of not less than 60 MPa.

8. The induction heating device according to claim 1 or 2, characterized in that: The connecting components are bolts and mating nuts.

9. The induction heating device according to claim 1 or 2, characterized in that: The device is cylindrical in shape, with an inner diameter of 72mm, an outer diameter of 100mm, and a height of 55mm.

10. The induction heating device according to claim 1 or 2, characterized in that: The lead-out length of the heating coil is 120mm.

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