A precise injection mold with self-lubricating function and a self-lubricating control method

Abstract

This invention discloses a precision injection mold with self-lubricating function and a self-lubricating control method, belonging to the field of injection molding technology. The precision injection mold includes a fixed mold and a moving mold arranged opposite each other, and an ejector pin for ejecting the molded product. The moving mold has a guide hole for the ejector pin to pass through, and an oil groove is formed on the inner wall of the guide hole. An oil pusher ring, which slides in cooperation with the oil groove, is fixedly fitted on the ejector pin. An oil scraper ring and an oil return hole are provided at the end of the guide hole near the fixed mold to return residual lubricating oil on the ejector pin surface to the oil circuit. Pressure limiting valve assemblies are provided on both ends of the oil pusher ring, which automatically open to overflow when the oil pressure is too high. The oil circuit includes an oil filter assembly with a double-layer filter tube, a hydraulic sensor, and a temperature sensor, and is equipped with an analysis and judgment unit to monitor the oil pressure and temperature in real time, and to judge the lubricating oil status and generate prompt information based on the injection molding machine process parameters. This invention drives the lubricating oil to circulate in a closed oil circuit through the oil pusher ring, and, in conjunction with the oil scraper ring, achieves lubricating oil recovery and filtration, realizing continuous self-lubrication and intelligent maintenance of the precision injection mold, effectively avoiding problems such as ejector pin jamming and lubricating oil contamination of the product.

Description

Technical Field

[0001] This invention relates to the field of injection molding, specifically to a precision injection mold with self-lubricating function and a self-lubricating control method. Background Technology

[0002] Injection molding, also known as injection molding, is a molding method that combines injection and molding. The advantages of injection molding include high production speed and efficiency, automated operation, precise product dimensions, easy product updates and replacements, and the ability to produce complex shapes. It is suitable for mass production and molding of complex-shaped products. Under a certain temperature, plastic material is completely molten through a screw agitation, injected into a mold cavity under high pressure, and then cooled and solidified to obtain the molded product.

[0003] After injection molding, the product needs to be demolded. Traditional demolding methods include manual demolding and ejection demolding. Manual demolding is the simplest and most basic method, where operators use hand tools to remove the plastic part from the mold. It is suitable for larger, simpler plastic parts, but it requires a high level of skill from the operator and has low production efficiency. Ejection demolding is a common automatic demolding method, where ejector pins push the plastic part out of the mold. It is suitable for smaller, simpler plastic parts and can improve production efficiency, but it requires higher standards in mold design and manufacturing.

[0004] During the ejection and demolding process, the ejector pin needs to perform long-term reciprocating motion within the guide hole, thus requiring lubrication of the clearance between the ejector pin and the guide hole. In existing technologies, lubricating oil is often only injected into the clearance between the ejector pin and the guide hole using methods such as injection or spraying before the injection mold leaves the factory or during mold maintenance. While this method can temporarily maintain the smooth movement of the ejector pin, it has significant technical drawbacks:

[0005] Firstly, during injection molding, the mold is subjected to high temperature and high pressure for extended periods, making the lubricant prone to evaporation or loss due to heat, resulting in inconsistent lubrication. As the ejector pin reciprocates more frequently, the lubricating oil deteriorates due to frictional heat, even producing solid residues. This not only affects lubrication but also accelerates wear between the ejector pin and the inner wall of the guide hole. If the ejector pin lacks effective lubrication, jamming may occur during ejection and resetting, potentially leading to issues ranging from product failure to demolding to damage to the ejector mechanism and the mold itself.

[0006] Secondly, residual lubricating oil on the ejector pin surface can easily enter the mold cavity with the movement of the ejector pin. The lubricating oil evaporates and carbonizes at high temperatures, easily contaminating the surface of the product, causing product scrap or increasing secondary cleaning costs. Especially for injection-molded products with high appearance requirements (such as optical lenses, automotive lighting components, and medical consumables), oil contamination directly affects product yield.

[0007] To address the aforementioned issues, several self-lubricating ejector pins or molds have emerged in recent years. For example, some solutions achieve self-lubrication by creating recesses on the ejector pin surface and filling these recesses with grease; others use atomizing nozzles directly opposite the ejector pin to automatically release lubricant during demolding; still others embed solid lubricants (such as graphite) into the mold guide components, utilizing frictional heat to create lubrication through friction between the solid lubricant and the mold. Furthermore, self-lubricating coating technologies such as DLC (diamond-like carbon) coatings have also been applied to mold ejector pins, reducing the coefficient of friction to 0.1-0.15.

[0008] However, the aforementioned existing technologies still have shortcomings: although the solid lubricant embedding scheme achieves maintenance-free self-lubrication, the consumption of solid lubricant is non-renewable and it is not suitable for precision injection molding scenarios with extremely high cleanliness requirements; the atomized spray scheme requires additional control components and oil storage devices, which are complex in structure and make it difficult to precisely control the amount of lubricant sprayed; in the oil storage scheme with the pit on the pushrod surface, the lubricant cannot be replenished after consumption, resulting in insufficient long-term effectiveness; and although the self-lubricating coating has a low coefficient of friction, there is a risk of wear and peeling off the coating during long-term reciprocating motion, and once the coating fails, it loses its lubrication function.

[0009] Therefore, how to achieve continuous, effective, and clean self-lubrication of ejector pins during the long-term continuous operation of injection molds, and avoid problems such as ejector pin jamming, wear, and lubricating oil contamination of products caused by lubrication failure, remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0010] In order to solve the above-mentioned technical problems, the present invention provides a precision injection mold with self-lubricating function and a self-lubricating control method.

[0011] The technical solution of this invention is implemented as follows:

[0012] In one aspect, the present invention provides a precision injection mold with self-lubricating function, comprising a fixed mold and a moving mold disposed opposite to each other, and an ejector pin for ejecting a molded product from the moving mold, wherein the moving mold has a guide hole for the ejector pin to pass through, the inner wall of the guide hole has an oil groove, and an oil pusher ring that slides with the oil groove is fixedly sleeved on the ejector pin; characterized in that:

[0013] An annular groove is formed on the inner wall of the guide hole near the fixed mold. An oil scraper ring is embedded in the annular groove. Several oil return holes are formed circumferentially at the bottom of the annular groove. The oil return holes are connected to the lubricating oil passage through an oil return pipeline embedded in the moving mold.

[0014] The oil pusher ring has overflow holes on both ends, and each overflow hole is equipped with a pressure limiting valve assembly. The pressure limiting valve assembly opens when the oil pressure on the corresponding side exceeds a preset threshold, so that the lubricating oil flows from the high-pressure side to the low-pressure side.

[0015] The oil circuit is equipped with an oil filter assembly, which includes an oil storage box and a double-layer filter tube disposed in the oil storage box;

[0016] The oil storage box is fixedly installed on the side wall of the moving mold. The open end of the oil storage box is detachably connected to an end cap. The end cap is provided with an oil injection port. The first pipe connects the inner wall of the oil storage box and the outer wall of the double-layer filter tube to form a cavity. The second pipe connects the inner cavity of the double-layer filter tube.

[0017] The oil inlet is connected to a quick connector on the outer wall of the moving mold via an extension pipe.

[0018] The pressure relief valve assembly includes a valve stem, a valve core, and an elastic element. The valve stem is movably disposed within the overflow orifice. The valve core is fixedly connected to one side of the valve stem near the corresponding end face. The elastic element is disposed between the other end of the valve stem and the end face of the pusher ring, and is used to provide a preload force to the valve core to close the overflow orifice.

[0019] In another aspect, the present invention provides a self-lubricating control method for injection molds, applied to injection molds, comprising the following steps:

[0020] During the demolding process, the reciprocating sliding of the oil pusher ring in the oil tank drives the lubricating oil to circulate between the oil tank, the first pipe, the oil filter assembly, and the second pipe.

[0021] The residual lubricating oil on the surface of the push rod is scraped off by the oil scraper ring, and the scraped lubricating oil is returned to the oil filter assembly through the oil return hole and the oil return pipeline;

[0022] Oil pressure data is collected by a hydraulic sensor, and lubricating oil temperature data in the reservoir is collected by a temperature sensor.

[0023] The hydraulic pressure data and the injection molding machine's process parameters are imported into the analysis and judgment unit to determine the lubricating oil condition;

[0024] When the lubricating oil level is determined to be insufficient, an oil filling prompt signal is generated; when the oil pressure is determined to be too high, a prompt signal to replace the double-layer filter tube is generated; when the lubrication condition is determined to be normal, the current working state is maintained.

[0025] When the temperature collected by the temperature sensor exceeds a preset threshold, the heat dissipation structure outside the oil reservoir is activated to dissipate heat and a high temperature warning signal is generated.

[0026] It also includes the following steps: setting a friction sensor on the surface of the push rod to directly monitor the friction coefficient during the movement of the push rod. When the friction coefficient exceeds a preset threshold, a push rod wear or oil film abnormality warning signal is generated.

[0027] This invention achieves efficient, reliable, and predictable self-lubrication through a combination of structural innovation and intelligent monitoring. Specifically, it utilizes an oil pusher ring to actively drive lubricating oil to circulate in a closed oil circuit during the reciprocating motion of the ejector pin, achieving continuous dynamic lubrication between the ejector pin and the guide hole. Simultaneously, an oil scraper ring removes excess lubricating oil from the ejector pin surface and recovers it through return holes and pipelines, preventing lubricating oil from contaminating the mold cavity and affecting product surface quality, while also reducing lubricating oil consumption. A pressure-limiting valve assembly within the oil pusher ring automatically opens to balance pressure when oil pressure abnormally rises, preventing damage to the oil circuit system. Furthermore, the integrated hydraulic sensor, temperature sensor, and analysis unit monitor oil pressure and temperature in real time and, combined with injection molding machine process parameters, determine the lubricating oil status. It promptly generates prompts for oil injection, filter replacement, or heat dissipation when oil level is insufficient, oil pressure is excessive, or temperature exceeds limits, enabling fault warnings and intelligent maintenance. This significantly improves the smoothness of demolding and product accuracy, extends the service life of the ejector pin and mold, and ensures the continuity and yield rate of injection molding production. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a precision injection mold with self-lubricating function according to the present invention.

[0029] Figure 2 This is a schematic diagram of the moving mold structure of a precision injection mold with self-lubricating function according to the present invention.

[0030] Figure 3 This is a schematic diagram of the oil scraper ring of a precision injection mold with self-lubricating function according to the present invention.

[0031] Figure 4 This is a schematic diagram of the oil circuit of a precision injection mold with self-lubricating function according to the present invention.

[0032] In the diagram: 1-Moving mold; 2-Fixed mold; 3-Ejector pin; 4-Oil passage; 5-Oil pusher ring; 6-Oil scraper ring; 7-Overflow hole; 8-Pressure relief valve assembly; 9-Oil reservoir. Detailed Implementation

[0033] Example 1

[0034] like Figure 1-4As shown, this embodiment provides a precision injection mold with self-lubricating function, including a fixed mold and a moving mold arranged opposite to each other, and an ejector pin for ejecting the molded product from the moving mold. The moving mold has a guide hole for the ejector pin to pass through, and an oil groove is formed in the inner wall of the guide hole. An oil pusher ring that slides with the oil groove is fixedly sleeved on the ejector pin.

[0035] An annular groove is formed on the inner wall of the guide hole near the fixed mold. An oil scraper ring is embedded in the annular groove. Several oil return holes are formed circumferentially at the bottom of the annular groove. The oil return holes are connected to the lubricating oil passage through an oil return pipeline embedded in the moving mold.

[0036] This invention utilizes the reciprocating sliding of an oil pusher ring within an oil groove to drive the continuous circulation of lubricating oil in the oil circuit, achieving automatic lubrication of the friction pair between the ejector rod and the guide hole, eliminating the need for manual periodic oiling. As the oil pusher ring slides, the flow direction of the lubricating oil aligns with the movement direction of the ejector rod, reducing the relative motion resistance between the lubricating oil and the ejector rod, resulting in smoother ejector rod movement and effectively preventing ejector rod jamming due to lubrication failure. Furthermore, by placing an oil scraper ring at the end of the guide hole near the fixed mold, residual lubricating oil on the ejector rod surface is scraped off before the ejector rod extends into the mold cavity, effectively preventing lubricating oil from being carried into the mold cavity and contaminating the injection-molded product. This invention is particularly suitable for precision injection molding scenarios with high cleanliness requirements, such as optical lenses, medical consumables, and automotive lighting components. Simultaneously, the lubricating oil scraped off by the oil scraper ring flows back to the oil circuit through the oil return hole and return pipeline, achieving lubricating oil recycling and reuse, avoiding resource waste. By setting up return oil holes and return oil pipelines, the lubricating oil scraped off by the oil scraper ring is directly guided back into the lubricating oil circuit to participate in circulation. Together with the first pipe, the second pipe, and the oil pusher ring, it forms a complete closed-loop circulation lubrication system, which enables the lubricating oil to automatically circulate and be reused during the demolding process. This effectively solves the problems of non-renewable lubricating oil and poor long-term effectiveness in the existing technology, and greatly extends the maintenance-free cycle of the lubrication system.

[0037] The oil pusher ring has overflow holes on both ends, and each overflow hole is equipped with a pressure limiting valve assembly. The pressure limiting valve assembly opens when the oil pressure on the corresponding side exceeds a preset threshold, so that the lubricating oil flows from the high-pressure side to the low-pressure side.

[0038] This invention incorporates pressure-limiting valve assemblies at both ends of the oil pusher ring. When the oil pressure on one side exceeds a preset threshold, the overflow valve automatically opens, allowing lubricating oil to flow from the high-pressure side to the low-pressure side. This prevents excessively high oil pressure in the oil groove from causing seal failure and leakage into the mold cavity, further ensuring product cleanliness. The pressure-limiting valve employs a mechanical structure, offering rapid response, high reliability, and automatic operation without external control signals.

[0039] The oil circuit is equipped with an oil filter assembly, which includes an oil reservoir and a double-layer filter tube disposed within the reservoir. This invention, by incorporating the oil filter assembly into the oil circuit and utilizing the double-layer filter tube to continuously filter the circulating lubricating oil, completes filtration and purification during each demolding process. This promptly removes solid residues from the lubricating oil, preventing them from exacerbating wear on the ejector rod and guide hole, thus extending the service life of the lubricating oil and the maintenance cycle of the ejector rod. Through the coordinated operation of the oil scraper ring and the oil filter assembly, a closed-loop cycle of "lubrication—oil scraping—recirculation—filtration—relubrication" is formed. This ensures the cleanliness of the ejector rod surface, prevents lubricating oil contamination of the product, and achieves the circulation, purification, and reuse of the lubricating oil, significantly reducing lubricating oil consumption and replacement frequency.

[0040] The oil circuit is also equipped with a hydraulic sensor, and the oil reservoir contains a temperature sensor. The hydraulic sensor collects oil pressure data, and the temperature sensor collects lubricating oil temperature data. This invention, by incorporating the hydraulic and temperature sensors, collects oil pressure and temperature data in real time and includes an analysis and judgment unit to intelligently assess the lubricating oil condition. This allows for timely detection of abnormalities such as insufficient oil volume, abnormal oil pressure, and excessively high oil temperature, generating corresponding alerts. This achieves online monitoring and fault warning of the lubrication status, facilitating timely handling by maintenance personnel and ensuring long-term stable mold operation. In this invention, the analysis and judgment unit receives process parameters from the injection molding machine (such as injection pressure and holding time) as input, making the lubricating oil condition assessment results more closely reflect actual working conditions. This avoids misjudgments due to changes in process conditions, improving the accuracy and reliability of monitoring.

[0041] The injection mold also includes an analysis and judgment unit, which receives the process parameters of the injection molding machine as input, judges the state of the lubricating oil based on the oil pressure data, and generates corresponding prompt information based on the judgment result.

[0042] The oil circuit is also provided with an oil pipe assembly, which includes a first pipe and a second pipe. The first pipe is connected to the end of the oil tank away from the fixed mold, and the second pipe is connected to the other end of the oil tank. The first pipe and the second pipe are connected to each other through the oil filter assembly.

[0043] The oil storage box is fixedly installed on the side wall of the moving mold. The open end of the oil storage box is detachably connected to an end cap. The end cap is provided with an oil injection port. The first pipe connects the inner wall of the oil storage box and the outer wall of the double-layer filter tube to form a cavity. The second pipe connects the inner cavity of the double-layer filter tube.

[0044] The oil inlet is connected to a quick connector on the outer wall of the moving mold via an extension pipe.

[0045] The pressure-limiting valve assembly includes a valve stem, a valve core, and an elastic element. The valve stem is movably disposed within the overflow orifice, and the valve core is fixedly connected to the side of the valve stem near its corresponding end face. The elastic element is disposed between the other end of the valve stem and the end face of the pusher ring, providing a preload force to the valve core to close the overflow orifice. This invention achieves mechanical automatic control of the pressure-limiting valve through the cooperative structure of the valve stem, valve core, and elastic element. When the oil pressure exceeds the preload force of the elastic element, the valve core automatically opens; after the oil pressure returns to normal, the elastic element pushes the valve core to automatically reset and close. The structure is simple and reliable, requires no external energy or control signal, and can operate stably for extended periods.

[0046] Example 2

[0047] This embodiment provides a self-lubricating control method for injection molds, applied to injection molds, including the following steps:

[0048] During the demolding process, the reciprocating sliding of the oil pusher ring in the oil tank drives the lubricating oil to circulate between the oil tank, the first pipe, the oil filter assembly, and the second pipe.

[0049] The residual lubricating oil on the surface of the push rod is scraped off by the oil scraper ring, and the scraped lubricating oil is returned to the oil filter assembly through the oil return hole and the oil return pipeline;

[0050] Oil pressure data is collected by a hydraulic sensor, and lubricating oil temperature data in the reservoir is collected by a temperature sensor.

[0051] The hydraulic pressure data and the injection molding machine's process parameters are imported into the analysis and judgment unit to determine the lubricating oil condition;

[0052] When the lubricating oil level is determined to be insufficient, an oil filling prompt signal is generated; when the oil pressure is determined to be too high, a prompt signal to replace the double-layer filter tube is generated; when the lubrication condition is determined to be normal, the current working state is maintained.

[0053] When the temperature collected by the temperature sensor exceeds a preset threshold, the heat dissipation structure outside the oil reservoir is activated to dissipate heat and a high temperature warning signal is generated.

[0054] It also includes the following steps: setting a friction sensor on the surface of the push rod to directly monitor the friction coefficient during the movement of the push rod. When the friction coefficient exceeds a preset threshold, a push rod wear or oil film abnormality warning signal is generated.

[0055] This invention achieves closed-loop management of the self-lubricating process through the above control steps: the oil pusher ring drives the lubricating oil circulation for continuous lubrication; the oil scraper ring and oil filter assembly work together to recover and purify the lubricating oil; sensors collect oil pressure and temperature data in real time; and the analysis and judgment unit intelligently judges the lubricating oil status based on the oil pressure data and injection molding machine process parameters, generating corresponding prompts. The entire control process is highly automated, requiring no manual intervention, and achieves online monitoring and intelligent maintenance of the lubrication status, significantly reducing the frequency of manual inspections and maintenance costs.

Claims

1. A precision injection mold with self-lubricating function, comprising a fixed mold and a moving mold arranged opposite to each other, and an ejector pin for ejecting the molded product from the moving mold, wherein the moving mold has a guide hole for the ejector pin to pass through, the inner wall of the guide hole has an oil groove, and an oil pusher ring that slides with the oil groove is fixedly sleeved on the ejector pin; characterized in that: An annular groove is formed on the inner wall of the guide hole near the fixed mold. An oil scraper ring is embedded in the annular groove. Several oil return holes are formed circumferentially at the bottom of the annular groove. The oil return holes are connected to the lubricating oil passage through an oil return pipeline embedded in the moving mold. The oil pusher ring has overflow holes on both ends, and each overflow hole is equipped with a pressure limiting valve assembly. The pressure limiting valve assembly opens when the oil pressure on the corresponding side exceeds a preset threshold, so that the lubricating oil flows from the high-pressure side to the low-pressure side. The oil circuit is equipped with an oil filter assembly, which includes an oil storage box and a double-layer filter tube disposed in the oil storage box; The oil circuit is also equipped with a hydraulic sensor, and the oil reservoir is equipped with a temperature sensor. The hydraulic sensor is used to collect oil pressure data, and the temperature sensor is used to collect lubricating oil temperature data. The injection mold also includes an analysis and judgment unit, which receives the process parameters of the injection molding machine as input, judges the state of the lubricating oil based on the oil pressure data, and generates corresponding prompt information based on the judgment result.

2. The precision injection mold with self-lubricating function according to claim 1, characterized in that, The oil circuit is also provided with an oil pipe assembly, which includes a first pipe and a second pipe. The first pipe is connected to the end of the oil tank away from the fixed mold, and the second pipe is connected to the other end of the oil tank. The first pipe and the second pipe are connected to each other through the oil filter assembly.

3. The precision injection mold with self-lubricating function according to claim 1, characterized in that, The oil storage box is fixedly installed on the side wall of the moving mold. The open end of the oil storage box is detachably connected to an end cap, and the end cap is provided with an oil injection port. The first pipe connects the inner wall of the oil storage box and the outer wall of the double-layer filter tube to form a cavity, and the second pipe connects to the inner cavity of the double-layer filter tube.

4. The precision injection mold with self-lubricating function according to claim 3, characterized in that, The oil inlet is connected to a quick connector on the outer wall of the moving mold via an extension pipe.

5. The precision injection mold with self-lubricating function according to claim 1, characterized in that, The pressure relief valve assembly includes a valve stem, a valve core, and an elastic element. The valve stem is movably disposed within the overflow orifice. The valve core is fixedly connected to one side of the valve stem near the corresponding end face. The elastic element is disposed between the other end of the valve stem and the end face of the pusher ring, and is used to provide a preload force to the valve core to close the overflow orifice.

6. The precision injection mold with self-lubricating function according to claim 1, characterized in that, The oil storage box is provided with a heat dissipation structure on its exterior, which is a heat dissipation fin or a semiconductor cooling chip.

7. The precision injection mold with self-lubricating function according to claim 1, characterized in that, The oil pusher ring has microchannels extending axially on its circumferential surface. The microchannels connect the two ends of the oil pusher ring and are used to ensure that the lubricating oil in the oil groove is evenly distributed when the push rod reciprocates.

8. A self-lubricating control method for injection molds, applied to a precision injection mold with self-lubricating function as described in any one of claims 1 to 7, characterized in that, Includes the following steps: During the demolding process, the reciprocating sliding of the oil pusher ring in the oil tank drives the lubricating oil to circulate between the oil tank, the first pipe, the oil filter assembly, and the second pipe. The residual lubricating oil on the surface of the push rod is scraped off by the oil scraper ring, and the scraped lubricating oil is returned to the oil filter assembly through the oil return hole and the oil return pipeline; Oil pressure data is collected by a hydraulic sensor, and lubricating oil temperature data in the reservoir is collected by a temperature sensor. The hydraulic pressure data and the injection molding machine's process parameters are imported into the analysis and judgment unit to determine the lubricating oil condition; When it is determined that the lubricating oil level is insufficient, an oil filling prompt signal is generated; When the oil pressure is determined to be too high, a prompt signal is generated to replace the double-layer filter tube; When the lubrication condition is determined to be normal, maintain the current working state; When the temperature collected by the temperature sensor exceeds a preset threshold, the heat dissipation structure outside the oil reservoir is activated to dissipate heat and a high temperature warning signal is generated.

9. The method according to claim 8, characterized in that, It also includes the following steps: A friction sensor is installed on the surface of the push rod to directly monitor the friction coefficient during the push rod's movement. When the friction coefficient exceeds a preset threshold, a push rod wear or oil film abnormality warning signal is generated.

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