High-precision metal injection molding mechanism and method

Abstract

A high-precision metal injection molding mechanism and method. The use of a connection and driving mode that "two ends of an integrated piston and piston rod are respectively connected to a feed screw and a material storage driving assembly, and the material storage driving assembly provides motion power" can reduce the length of the piston and the feed screw while ensuring a large material storage capacity, so that the strength is improved, and the stability of the mechanism is improved, thereby improving the injection precision. In addition, high-frequency response servo valves are respectively arranged on the oil inlet side and the oil outlet side of an injection oil cylinder for double-response control; in addition to controlling the injection speed by means of quick response-based valve opening adjustment on the oil outlet side, the injection speed of the piston is also controlled by controlling the oil inlet amount by means of quick response-based valve opening adjustment on the oil inlet side, achieving multi-stage control of the injection speed.

Description

High-precision metal injection molding mechanism and method Technical Field

[0001] The present invention relates to the technical field of metal injection molding, and in particular to a high-precision metal injection molding mechanism and method. Background Art

[0002] Magnesium's specific gravity is approximately two-thirds that of aluminum and one-quarter that of iron. It is the lightest of practical metals and boasts high strength and rigidity. Due to its low density, magnesium alloys offer the greatest advantage in lightweighting. These properties make magnesium alloys promising applications, such as lightweighting automotive parts.

[0003] Currently, magnesium alloy products are primarily produced using injection molding machines in conjunction with molds. Semi-solid injection molding, a key method for forming magnesium alloys, offers unparalleled advantages over other casting methods, such as cold-chamber die-casting. These include energy savings (magnesium alloys have a lower melting temperature: conventional magnesium alloy casting requires heating the alloy to 650-680°C, while injection molding only requires heating to 580-600°C), environmental protection (no need for protective gas: conventional magnesium alloy casting requires the use of environmentally harmful protective gases such as SF6 to prevent oxidation and combustion, while injection molding prevents the molten magnesium alloy from coming into contact with air), and safety (conventional magnesium alloy casting, despite the use of protective gas, still carries the risk of spontaneous combustion and explosion. Injection molding, however, prevents these risks by keeping the molten magnesium alloy in a sealed container away from air).

[0004] The magnesium alloy injection molding method involves feeding the magnesium alloy into a feed pipe, heating it to a molten state, then continuously feeding it through a rotating screw, and then injecting it into the mold at high speed. Numerous metal injection molding devices currently utilize this process. However, with the increasing demand for precision in the production of magnesium alloy parts, existing injection molding devices are no longer able to meet these demands.

[0005] For example, the Chinese patent application publication number CN101524747A provides a servo-controlled semi-solid magnesium alloy high-speed injection molding machine, which includes a clamping mechanism, an injection mechanism, a hydraulic mechanism, an electrical mechanism, and a frame, wherein: the injection cylinder in the injection mechanism is provided with a hollow floating piston; the feeding system is equipped with a feed screw assembly capable of forming the microstructure of the semi-solid magnesium alloy; the hydraulic mechanism includes a cartridge valve and a high-response accumulator; the high-speed injection speed control system is provided with a high-frequency response servo valve on the oil outlet side of the injection cylinder, and two pressure sensors PS1 and PS2 are provided on the oil outlet side of the injection cylinder to detect the pressure on the oil outlet side of the injection cylinder in real time; the electrical mechanism is provided with a high-speed CPU module to control the high-speed injection speed and perform real-time closed-loop control. In the device provided by this patent, the high-frequency response servo valve provided on the oil outlet side of the injection cylinder is used to achieve closed-loop control of the injection speed during the injection process, thereby achieving high-precision control of the injection speed and improving the precision of the injection molding. However, this device still has the following shortcomings in terms of precision control of injection molding:

[0006] (1) First, the high-frequency response servo valve can only be used to adjust the valve opening to control the accuracy of the injection volume. At the same time, there is a certain time difference in the response of the high-frequency response servo valve to adjust the valve opening, and it is impossible to achieve real-time control of the injection accuracy.

[0007] (2) Secondly, the precision control effect of the device depends on the response speed of the high-frequency response servo valve. Since the high-frequency response servo valve cannot play a deceleration and buffering role, it can only reduce the injection volume by reducing the valve opening. The long-term impact of the liquid can easily slow down the response speed of the high-frequency response servo valve, thus making the precision control effect of the device easily deteriorate.

[0008] (3) The third is to rely on a single high-frequency response servo valve to achieve precision control of the injection device, and its effect has the defect of being unstable. Summary of the Invention

[0009] In order to solve one or more of the above technical problems and to improve the precision of magnesium alloy injection molding, the present invention provides a high-precision metal injection molding mechanism and method.

[0010] The specific technical solutions of the present invention are:

[0011] In a first aspect, the present invention provides a high-precision metal injection molding mechanism, comprising an injection unit, a hydraulic unit, and a feeding unit, wherein:

[0012] The injection unit includes an injection cylinder, an integrated piston and a piston rod arranged in the injection cylinder;

[0013] The feeding unit includes a feeding screw and a storage drive assembly. The two ends of the integrated piston and piston rod are respectively connected to the feeding screw and the storage drive assembly, and are used to drive the integrated piston and piston rod to push the feeding screw to achieve the delivery of the injection liquid through the driving action of the storage drive assembly;

[0014] A high-frequency response servo valve is provided on both the oil inlet side and the oil outlet side of the injection cylinder.

[0015] The researchers of the present invention found in the experiment that the present invention has a great effect on improving the precision of metal injection molding by using an integrated piston and piston rod in the injection unit and directly connecting it with the feed screw of the feeding unit. Further analysis of its principle is that in the existing technology, the piston in the injection cylinder is often connected to the feed screw via a driving component, or connected to the feed screw through other connecting structures. Therefore, the total length of the piston and the feed screw is often long, which will cause insufficient strength. During high-speed injection in actual production, there will be deformation problems causing reduced injection precision. After adopting the connection drive method of "the integrated piston and piston rod are directly connected to the feed screw of the feeding unit, and the storage drive assembly is connected at the end side to provide motion power", the length of the piston and the feed screw can be reduced, the strength can be improved, and the stability of the mechanism can be improved while ensuring a large storage volume. In this way, the injection precision can be improved.

[0016] High-frequency response servo valves are provided on both the oil inlet and oil outlet sides of the injection cylinder. The principle is that magnesium alloy is lighter than other metals. During actual injection, it has a greater acceleration when the same force is used to push it for injection. At the final stage of injection, it will have a greater injection speed compared with other metals. Therefore, at the final stage, it is particularly important to control the injection accuracy of magnesium alloy. The present invention provides high-frequency response servo valves on both the oil inlet and oil outlet sides of the injection cylinder for dual-response control. In addition to quickly responding to and adjusting the valve opening on the oil outlet side to control the injection speed, the oil inlet amount is controlled by quickly responding to the valve opening adjustment on the oil inlet side to regulate the driving force of the piston, thereby performing multi-stage control of the injection speed. At the same time, as described in the background technology, the injection speed control effect of the high-frequency response servo valve depends on the response speed of the high-frequency response servo valve. However, due to the limitation of the response speed of high-frequency response servo valve products on the market, the injection accuracy cannot be easily improved by replacing products with faster responses. In the metal injection molding mechanism provided by the present invention, high-frequency response servo valves are arranged on the oil inlet side and the oil outlet side of the injection cylinder to perform dual proportional valve ring control. Through multi-stage control of the injection speed, the problem of poor injection accuracy control caused by the slow response of a single high-frequency response servo valve on the oil outlet side can be avoided, and the problem that the response of a single high-frequency response servo valve cannot ensure the stability of injection speed control can be overcome.

[0017] It's important to note that the oil inlet and outlet sides of the injection cylinder are determined by the direction of linear motion of the integrated piston and piston rod. The oil outlet side is defined by the piston segment of the integrated piston and piston rod. That is, if one side is the oil outlet during injection, it will become the oil inlet during ejection.

[0018] As a preferred embodiment of the above technical solution of the present invention, the oil outlet side of the injection cylinder is provided with a first oil outlet and a second oil outlet, the second oil outlet is close to the end of the injection cylinder, and the diameter of the second oil outlet is smaller than the first oil outlet.

[0019] The problem of poor precision in metal injection molding in the existing technology also lies in the speed control problem at high injection speeds. At the end of the injection process, the injection speed is relatively fast, and the liquid is subjected to long-term impact, which can easily slow down the response speed of the high-frequency response servo valve. The present invention provides two oil outlets, one large and one small, on the oil outlet side. The small oil outlet is close to the end of the injection cylinder. During the injection process, in the pre-injection stage and the middle stage, the oil is discharged through the large outlet of the first oil outlet. In the final stage, the amount of oil on the oil outlet side is small and the speed is relatively fast, and the speed is buffered through the second oil outlet. The oil discharge on the oil outlet side during injection directly affects the acceleration and speed control of the injection. At the same time, near the end of the injection process, the hydraulic structure needs to protect the mechanical structure to prevent mechanical collision. During the injection process, when the injection position reaches the edge of the large oil drain hole, the oil on the oil outlet side of the injection cylinder returns to the oil tank through the second oil outlet of the small oil drain hole, realizing a mechanical-hydraulic brake. This not only has a better speed buffering effect, but also can avoid impact damage to the mechanism.

[0020] It's important to note that the second oil outlet has a smaller diameter than the first oil outlet. This means that at the same flow rate, less oil is discharged through the second oil outlet in the same amount of time as the first oil outlet. The requirement that the second oil outlet has a smaller diameter than the first does not necessarily require both the first and second oil outlets to be circular.

[0021] As a preferred embodiment of the above technical solution of the present invention, cylinder covers are respectively provided at both ends of the injection cylinder for sealing the inner cavity of the injection cylinder; and an oil drain groove is provided on the cylinder cover.

[0022] Researchers have discovered that improving the smoothness of the injection cylinder's oil return and drain during the injection process can also improve injection precision control. The present invention further incorporates an oil drain groove on the injection cylinder, which is used to seal the injection cylinder's inner cavity. This groove serves to buffer the flow of oil and improve the smoothness of oil drain, particularly for improving the smoothness of oil drain and return at the second oil outlet relative to the injection cylinder's inner cavity.

[0023] As a preferred embodiment of the above technical solution of the present invention, a rotating sealing ring is provided on the piston section of the integrated piston and the piston rod, so as to ensure that the integrated piston and the piston rod are in close contact with the inner wall of the injection cylinder;

[0024] A pressure reducing ring and a wear-resistant ring are also provided on the piston section of the integrated piston and the piston rod. The pressure reducing ring is provided on both sides of the rotating sealing ring, and the wear-resistant ring is provided on the side of the pressure reducing ring away from the rotating sealing ring.

[0025] During the injection process, the injection cylinder can experience oil leakage—that is, oil flowing from the outlet to the inlet—which can lead to poor injection precision control. The integrated piston and piston rod require both axial and rotational motion during operation. To meet the requirements of precise control and prevent oil leakage, high sealing requirements are required for the outer diameter of the piston and piston rod segments. The present invention employs a rotating sealing ring on the piston segments of the integrated piston and piston rod, ensuring close contact between the integrated piston and piston rod and the inner wall of the injection cylinder for sealing. However, the sealing ring's application limit depends on the product of the oil pressure P and the speed V it experiences. The value of P*V is limited, making it susceptible to seal failure during high-speed injection. The present invention further incorporates pressure-reducing rings on both sides of the rotating sealing ring, and further incorporates a wear-resistant ring on the side of the pressure-reducing ring away from the rotating sealing ring. This "wear-resistant ring, pressure-reducing ring, rotating sealing ring, pressure-reducing ring, and wear-resistant ring" seals the oil inlet and outlet sides of the injection cylinder, thereby addressing the oil leakage issue and improving injection precision.

[0026] As a preferred embodiment of the above technical solution of the present invention, the material storage drive assembly includes a servo motor and a transmission shaft, and the transmission shaft is spline-connected to the integrated piston and piston rod. The servo motor drives the transmission shaft to rotate through a transmission belt, thereby moving the integrated piston and piston rod.

[0027] As a preferred embodiment of the above technical solution of the present invention, it further includes a hydraulic unit, which includes a first high-response accumulator and at least one nitrogen gas storage cylinder, the high-pressure nitrogen side of the high-response accumulator is connected to the nitrogen gas storage cylinder, and the oil outlet side of the high-response accumulator is connected to the oil inlet side of the injection cylinder;

[0028] A proportional throttle valve is provided on the oil outlet side of the high-response accumulator and the oil inlet side of the injection cylinder, and a second high-response accumulator is provided on the proportional throttle valve.

[0029] As a preferred embodiment of the above technical solution of the present invention, pressure sensors are respectively provided on the oil inlet side and the oil outlet side of the injection cylinder to detect the inlet and outlet pressures of the injection cylinder in real time.

[0030] By setting pressure sensors on the oil inlet and outlet sides of the injection cylinder, the system pressure can be detected in real time. Real-time monitoring can improve the response speed and further improve the injection accuracy.

[0031] As a preferred embodiment of the above technical solution of the present invention, the high-precision metal injection molding mechanism further includes a whole-movement unit, the whole-movement unit includes a bearing assembly, and the bearing assembly is connected to the barrel;

[0032] The whole-shift unit also includes an injection seat, a whole-shift oil cylinder, and a whole-shift piston rod arranged in the whole-shift oil cylinder. The bearing assembly is connected to the whole-shift piston rod. The injection seat pushes the whole-shift piston rod to move in the whole-shift oil cylinder, so that the barrel and the fixed template move relative to each other.

[0033] As a preferred embodiment of the above technical solution of the present invention, the high-precision metal injection molding mechanism also includes a rotating unit, which includes a rotating oil cylinder and a rotating piston rod arranged in the rotating oil cylinder; the rotating unit also includes a connected middle bottom plate and a lower bottom plate, and the middle bottom plate and the lower bottom plate are respectively connected to the rotating oil cylinder, and a rotating locating pin is arranged between the middle bottom plate and the lower bottom plate. When the rotating piston rod moves in the rotating oil cylinder, the middle bottom plate rotates around the lower bottom plate with the rotating locating pin as the center.

[0034] In a second aspect, the present invention further provides a method for high-precision metal injection molding, comprising the following steps:

[0035] S1: The injection unit uses an integrated piston and piston rod connected to the feed screw, shortening the length of the injection unit and reducing deformation of the metal injection molding mechanism;

[0036] S2: Increase the sealing performance of the integrated piston, piston rod and injection cylinder;

[0037] S3: The injection unit is equipped with a deceleration structure to slow down the injection speed at the end of the injection stage;

[0038] S4: High-frequency response servo valves are installed on both the oil inlet and outlet sides of the injection cylinder to respond to user commands with high dynamic response.

[0039] In a third aspect, based on the above-mentioned high-precision metal injection molding mechanism or the above-mentioned high-precision metal injection molding method, the present invention also provides a high-precision metal injection molding machine.

[0040] The high-precision metal injection molding machine includes the high-precision metal injection molding mechanism described above. The use of the molding machine for metal injection molding of magnesium alloys has the advantage of high precision.

[0041] Compared with the prior art, the present invention has the following technical effects:

[0042] (1) The present invention provides a high-precision metal injection molding mechanism, which has the following advantages:

[0043] ① In the existing technology, the piston in the injection cylinder is often connected to the feed screw via a driving component, or connected to the feed screw through other connecting structures. Therefore, the total length of the piston and the feed screw is often long, which will cause insufficient strength. During high-speed injection in actual production, there will be deformation problems, resulting in reduced injection accuracy. After adopting the connection and drive method of "the integrated piston and piston rod are directly connected to the feed screw of the feeding unit, and the storage drive assembly is connected at the end side to provide movement power", the length of the piston and the feed screw can be reduced while ensuring a large storage volume, the strength can be improved, and the stability of the mechanism can be improved, thereby improving the injection accuracy.

[0044] ② Furthermore, the present invention provides high-frequency response servo valves on both the oil inlet and oil outlet sides of the injection cylinder. Magnesium alloy is lighter than other metals. During actual injection, it has a greater acceleration when the same force is used to push it into the injection. In the final stage of injection, it has a higher injection speed than other metals. Therefore, in the final stage, it is particularly important to control the injection accuracy of magnesium alloy. The present invention provides high-frequency response servo valves on both the oil inlet and oil outlet sides of the injection cylinder for dual response. In addition to quickly responding to adjust the valve opening on the oil outlet side to control the injection speed, the rapid response valve opening adjustment on the oil inlet side controls the oil inlet volume to regulate the driving force of the piston, thereby performing multi-stage control of the injection speed.

[0045] ③ The present invention further provides an oil drain groove on the injection cylinder, which is used to seal the injection cylinder cavity, to buffer the flow of oil and improve the smoothness of oil drainage. In particular, it improves the smoothness of oil discharge and return at the second oil outlet relative to the injection cylinder cavity. By further improving the smoothness of oil return and discharge from the injection cylinder, the present invention improves the control effect of injection precision.

[0046] ④ The present invention further arranges a pressure reducing ring on both sides of the rotating sealing ring, and then arranges a wear-resistant ring on the side of the pressure reducing ring away from the rotating sealing ring, so as to arrange "wear-resistant ring, pressure reducing ring, rotating sealing ring, pressure reducing ring, wear-resistant ring" in the piston section of the integrated piston and piston rod to seal the oil inlet and oil outlet sides of the injection cylinder, thereby solving the problem of oil leakage and improving the injection accuracy.

[0047] (2) The present invention also provides a high-precision metal injection molding method, which is used to perform magnesium alloy metal injection molding and has the characteristic of injection precision control effect.

[0048] (3) The present invention also provides a high-precision metal injection molding machine, which is used to perform magnesium alloy metal injection molding and has the characteristic of injection precision control effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0050] FIG1 is a schematic structural diagram of a high-precision metal injection molding mechanism according to the present invention;

[0051] FIG2 is a schematic cross-sectional view of a high-precision metal injection molding mechanism according to the present invention;

[0052] FIG3 is a schematic diagram of a cross-sectional view of the piston section structure of the integrated piston and piston rod in FIG2 ;

[0053] FIG4 is a schematic diagram of the cross-sectional structure of the piston section on the oil outlet side of the injection cylinder in FIG2 ;

[0054] FIG5 is a schematic cross-sectional view of the injection detection unit in FIG1 ;

[0055] FIG6 is a schematic diagram of another structure of the injection detection unit in FIG1 ;

[0056] FIG7 is a schematic structural diagram of the entire shift unit in FIG1 ;

[0057] FIG8 is a schematic structural diagram of the entire shift unit and the rotation unit in FIG1 ;

[0058] FIG9 is a schematic structural diagram of the lifting unit in FIG1 ;

[0059] FIG10 is a schematic diagram of the hydraulic control principle of a high-precision metal injection molding mechanism according to the present invention shown in FIG1 .

[0060] Among them, the figure numbers are: 100, injection unit, 101, integrated piston and piston rod, 102, injection cylinder, 1021, first oil outlet, 1022, second oil outlet, 103, cylinder head, 1031, oil drain groove, 104, wear-resistant ring, 105, pressure reducing ring, 106, rotary sealing ring, 200, feeding unit, 201, feeding screw, 202, barrel, 203, storage drive assembly, 2031, servo motor, 2032, small pulley, 2033, synchronous belt, 2034, large pulley, 2035, drive shaft, 300, injection detection unit Element, 301, travel seat, 302, bearing, 303, travel rod, 304, magnetic scale, 305, reading head, 400, full-shift unit, 401, fixed template, 402, full-shift cylinder, 403, full-shift piston rod, 404, middle bottom plate, 405, guide rail, 406, slider, 407, limit block, 408, fixed block, 409, injection seat, 410, load-bearing assembly, 500, rotating unit, 501, lower bottom plate, 502, rotating cylinder, 503, rotating piston rod, 504, rotating positioning pin, 505, copper pad, 600, lifting unit, 601, guide column, 602, base hole, 603, lifting cylinder, A, oil inlet side during injection, B, oil outlet side during injection. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application.

[0062] In the following description, multiple embodiments of the present application are provided. Different embodiments may be replaced or combined, and therefore the present application may be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then the present application should also be considered to include embodiments containing one or more of all other possible combinations of A, B, C, and D, even though such embodiments may not be explicitly described in the following text.

[0063] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the elements described without departing from the scope of the present application. Various examples may appropriately omit, replace, or add various processes or components. For example, the described method may be performed in an order different from the order described, and various steps may be added, omitted, or combined. In addition, features described in some examples may be combined in other examples.

[0064] Example 1:

[0065] This embodiment provides a high-precision metal injection molding mechanism, as shown in Figures 1 to 10.

[0066] As shown in Figures 1, 2 and 3, a high-precision metal injection molding mechanism includes an injection unit 100, a hydraulic unit, a feeding unit 200, and an electrical unit, wherein: the injection unit 100 includes an injection cylinder 102, and an integrated piston and piston rod 101 arranged in the injection cylinder 102; the feeding unit 200 includes a feeding screw 201 and a storage drive assembly 203, and the two ends of the integrated piston and piston rod 101 are respectively connected to the feeding screw 201 and the storage drive assembly 203, and are used to drive the integrated piston and piston rod 101 to push the feeding screw 201 to move through the driving action of the storage drive assembly 203, so as to realize the delivery of the injection liquid; high-frequency response servo valves are provided on the oil inlet side and the oil outlet side of the injection cylinder 102.

[0067] The oil inlet and outlet sides of the injection cylinder 102 are determined by the direction of linear motion of the integrated piston and piston rod 101. The piston segment of the integrated piston and piston rod 101 serves as the boundary, and the side in the direction of linear motion of the integrated piston and piston rod 101 is the oil outlet side. That is, during injection, if one side is the oil outlet, it will become the oil inlet side during ejection. As shown in Figure 2, during injection, area A is the oil inlet side, and area B is the oil outlet side.

[0068] By adopting the connection and driving mode of "the integrated piston and piston rod 101 are directly connected to the feeding screw 201 of the feeding unit 200, and the storage drive assembly 203 is connected at the end side to provide movement power", the length of the piston and the feeding screw 201 can be reduced while ensuring a large storage volume, the strength can be increased, and the stability of the mechanism can be improved, thereby achieving an improvement in injection accuracy, which has a great effect on improving the accuracy of metal injection molding.

[0069] Magnesium alloy is lighter than other metals. During actual injection, it has a greater acceleration when the same force is used to push it for injection. At the final stage of injection, it will have a greater injection speed compared to other metals. Therefore, in the final stage, it is particularly important to control the injection accuracy of magnesium alloy. The present invention provides high-frequency response servo valves on both the oil inlet and oil outlet sides of the injection cylinder 102 for dual response. In addition to quickly responding to and adjusting the valve opening on the oil outlet side to control the injection speed, the oil inlet amount is controlled by quickly responding to the valve opening on the oil inlet side to regulate the injection speed of the piston, thereby performing multi-stage control of the injection speed.

[0070] As a preferred embodiment of this invention, pressure sensors are provided on the oil inlet and outlet sides of the injection cylinder 102 to monitor the system pressure in real time. By providing pressure sensors on the oil inlet and outlet sides of the injection cylinder 102 to monitor the system pressure in real time, real-time monitoring can improve response speed and further enhance injection accuracy.

[0071] As shown in Figure 4, as a preference of this embodiment, the oil outlet side of the injection cylinder 102 is provided with a first oil outlet 1021 and a second oil outlet 1022. The second oil outlet 1022 is close to the end of the injection cylinder 102, and the diameter of the second oil outlet 1022 is smaller than that of the first oil outlet 1021.

[0072] By setting two oil outlets, one large and one small, on the oil outlet side, with the small oil outlet close to the end of the injection cylinder 102, during the injection process, in the pre-injection stage and the middle stage, the oil is discharged through the first oil outlet 1021. In the final stage, the amount of oil on the oil outlet side is small and the speed is fast, and speed buffering is performed through the second oil outlet 1022. The oil discharge on the oil outlet side during injection directly affects the acceleration and speed control of the injection. At the same time, near the end of the injection, the hydraulic structure needs to protect the mechanical structure to prevent mechanical collision. During the injection process, when the injection position reaches the edge of the large oil drain hole, the oil on the oil outlet side of the injection cylinder 102 returns to the oil tank through the second oil outlet 1022 with the small oil drain hole, realizing a mechanical-hydraulic brake. It not only has a better speed buffering effect, but also can avoid impact damage to the mechanism. The oil flow rate is controlled by a one-way throttle valve.

[0073] The second oil outlet 1022 has a smaller diameter than the first oil outlet 1021. This means that at the same flow rate, the amount of oil discharged through the second oil outlet 1022 in the same period of time is less than that of the first oil outlet 1021. The requirement that the second oil outlet 1022 has a smaller diameter than the first oil outlet 1021 does not necessarily mean that the first oil outlet 1021 and the second oil outlet 1022 must be circular.

[0074] As shown in Figure 4 , as a preferred embodiment of this embodiment, cylinder caps 103 are provided at both ends of the injection cylinder 102 for sealing the inner cavity of the injection cylinder 102; an oil drain groove is provided on the cylinder caps 103. This embodiment further provides an oil drain groove 1031 on the injection cylinder 102 for sealing the inner cavity of the injection cylinder 102 to buffer the flow of oil and improve the smoothness of oil drainage. In particular, this improves the smoothness of oil discharge and return at the relative position of the second oil outlet 1022 to the inner cavity of the injection cylinder 102. This improves the control effect of injection precision during the injection process by improving the smoothness of oil return and discharge from the injection cylinder 102.

[0075] As shown in Figure 3, as a preferred embodiment of this embodiment, a rotating sealing ring 106 is provided on the piston section of the integrated piston and piston rod 101, which is used to make the integrated piston and piston rod 101 in close contact with the inner wall of the injection cylinder 102; a pressure reducing ring 105 and a wear-resistant ring 104 are also provided on the piston section of the integrated piston and piston rod 101, and the pressure reducing ring 105 is provided on both sides of the rotating sealing ring 106, and the wear-resistant ring 104 is provided on the side of the pressure reducing ring 105 away from the rotating sealing ring 106.

[0076] The integrated piston and piston rod 101 requires both axial and rotational motion during operation. To meet the requirements of precise control and prevent oil leakage, the outer diameter of the piston section of the integrated piston and piston rod 101 must be highly sealed. The present invention provides a rotating sealing ring 106 on the piston section of the integrated piston and piston rod 101, allowing the integrated piston and piston rod 101 to be in close contact with the inner wall of the injection cylinder 102 for sealing. However, the application limit of the sealing ring depends on the product of the oil pressure P and the moving speed V. The value of P*V is limited, and the seal is prone to failure during high-speed injection. The present invention further arranges a pressure reducing ring 105 on both sides of the rotating sealing ring 106, and then arranges a wear-resistant ring 104 on the side of the pressure reducing ring 105 away from the rotating sealing ring 106, so as to arrange "wear-resistant ring 104, pressure reducing ring 105, rotating sealing ring 106, pressure reducing ring 105, wear-resistant ring 104" in the piston section of the integrated piston and piston rod 101 to seal the oil inlet and oil outlet sides of the injection cylinder 102, thereby solving the problem of oil leakage and improving the injection accuracy.

[0077] As shown in Figures 5 and 6 , the high-precision metal injection molding mechanism also includes an injection detection unit 300. The injection detection unit 300 is connected to the outer side of the integrated piston and piston rod 101. The injection detection unit 300 includes a travel seat 301, a bearing 302, a travel rod 303, a magnetic scale 304, and a reading head 305.

[0078] The stroke seat 301 and the integrated piston and piston rod 101 move axially simultaneously. However, when the integrated piston and piston rod 101 rotate, the stroke seat 301 does not rotate due to the presence of the bearing 302. The stroke rod 303 is fastened to the stroke seat 301 and moves axially simultaneously. The stroke rod 303 is mounted with a magnetic scale 304. The reading head 305 can detect the position movement of the magnetic scale 304 and calculate the movement speed based on the relationship between the position movement and the movement time. In this way, when the integrated piston and piston rod 101 drive the screw forward and backward, the reading head 305 detects the position movement of the magnetic scale 304 to calculate the position and speed of the screw movement, thereby realizing the calculation of the injection volume.

[0079] As shown in Figure 2, as a preferred embodiment of the present invention, the storage drive assembly 203 includes a servo motor 2031 and a transmission shaft 2035. The transmission shaft 2035 is connected to the integrated piston and piston rod 101 via a spline. The servo motor 2031 drives the transmission shaft 2035 to rotate via a transmission belt, thereby causing the integrated piston and piston rod 101 to move. Based on the connection and drive mode of "the integrated piston and piston rod 101 is directly connected to the feeding screw 201 of the feeding unit 200, and the storage drive assembly 203 is connected to the end side to provide motion power", the present embodiment sets the transmission shaft 2035 and the integrated piston and piston rod 101 to be connected via a spline to more flexibly control the movement of the feeding screw 201. Under the connection of the spline structure, it is possible to achieve the effect of a certain section of the rod moving while the end rod is stationary when necessary.

[0080] As shown in Figure 10 , as a preferred embodiment of this invention, the high-precision metal injection molding mechanism further includes a hydraulic unit comprising a first high-response accumulator and a nitrogen gas cylinder of suitable capacity. The high-pressure nitrogen side of the high-response accumulator is connected to the nitrogen gas cylinder, and the oil outlet side of the high-response accumulator is connected to the oil inlet side of the injection cylinder 102. Proportional throttle valves are provided between the oil outlet side of the high-response accumulator and the oil inlet side of the injection cylinder 102, and a second high-response accumulator is provided on the proportional throttle valve. By providing this second high-response accumulator, a small accumulator is installed on the proportional valve to provide pilot oil for the injection cylinder 102, thereby maintaining the proportional valve's high dynamic response.

[0081] As shown in Figures 7 and 8, as a preferred embodiment of this invention, the high-precision metal injection molding mechanism further includes a shifting unit 400. The shifting unit 400 includes an injection seat 409, a bearing assembly 410, a shifting cylinder 402, and a shifting piston rod 403 disposed within the shifting cylinder 402. The fixed plate 401 is connected to the shifting piston rod 403, and the injection seat 409 is connected to the barrel 202. When the injection seat 409 pushes the shifting cylinder 402 to move, the barrel 202 and the fixed plate 401 move relative to each other. The provision of the shifting unit 400 facilitates adjustment of the distance between the injection seat 409 and the fixed plate 401, facilitating mold disassembly.

[0082] As shown in Figures 7 and 8, as a preferred embodiment of this invention, the high-precision metal injection molding mechanism further includes a rotation unit 500. The rotation unit 500 includes a rotating cylinder 502 and a rotating piston rod 503 disposed within the rotating cylinder 502. The rotation unit 500 also includes a connected middle base plate 404 and a lower base plate 501. The middle base plate 404 and the lower base plate 501 are respectively connected to the rotating cylinder 502. A rotation locating pin 504 is provided between the middle base plate 404 and the lower base plate 501. When the rotating piston rod 503 moves within the rotating cylinder 502, the middle base plate 404 rotates around the lower base plate 501 with the rotation locating pin 504 as the center. The provision of the rotation unit 500 facilitates regular replacement of the nozzle, screw, and barrel 202. In this embodiment, limit blocks 407 are provided at both ends of the middle base plate 404 to prevent the slider 406, the bearing assembly 410, and the components thereon from sliding off the guide rails during assembly and maintenance.

[0083] As shown in Figures 8 and 9 , as a preferred embodiment of this invention, the high-precision metal injection molding mechanism further includes a lifting unit 600. This lifting unit 600 comprises a lower base plate 501 and a guide post 601 disposed below the lower base plate 501. The guide post 601 and the base hole 602 provide guidance. A lifting cylinder 603 raises and lowers the lower base plate 501, thereby raising and lowering the entire injection station 409. This allows for adaptability to different workstations.

[0084] Compared with the prior art, this embodiment has the following technical effects:

[0085] ① In the existing technology, the piston in the injection cylinder is often connected to the feed screw via a driving component, or connected to the feed screw through other connecting structures. Therefore, the total length of the piston and the feed screw is often long, which will cause insufficient strength. During high-speed injection in actual production, there will be deformation problems, resulting in reduced injection accuracy. After adopting the connection and drive method of "the integrated piston and piston rod are directly connected to the feed screw of the feeding unit, and the storage drive assembly is connected at the end side to provide movement power", the length of the piston and the feed screw can be reduced while ensuring a large storage volume, the strength can be improved, and the stability of the mechanism can be improved, thereby improving the injection accuracy.

[0086] ② Furthermore, the present invention provides high-frequency response servo valves on both the oil inlet and oil outlet sides of the injection cylinder. Magnesium alloy is lighter than other metals. During actual injection, it has a greater acceleration when the same force is used to push it into the injection. In the final stage of injection, it has a higher injection speed than other metals. Therefore, in the final stage, it is particularly important to control the injection accuracy of magnesium alloy. The present invention provides high-frequency response servo valves on both the oil inlet and oil outlet sides of the injection cylinder to perform dual-response control. In addition to quickly responding to adjust the valve opening on the oil outlet side to control the injection speed, the rapid response valve opening adjustment on the oil inlet side is also used to control the oil inlet amount to regulate the injection speed of the piston, thereby performing multi-stage control of the injection speed.

[0087] ③ The present invention further provides an oil drain groove on the injection cylinder, which is used to seal the injection cylinder cavity, to buffer the flow of oil and improve the smoothness of oil drainage. In particular, it improves the smoothness of oil discharge and return at the second oil outlet relative to the injection cylinder cavity. By further improving the smoothness of oil return and discharge from the injection cylinder, the present invention improves the control effect of injection precision.

[0088] ④ The present invention further arranges a pressure reducing ring on both sides of the rotating sealing ring, and then arranges a wear-resistant ring on the side of the pressure reducing ring away from the rotating sealing ring, so as to arrange "wear-resistant ring, pressure reducing ring, rotating sealing ring, pressure reducing ring, wear-resistant ring" in the piston section of the integrated piston and piston rod to seal the oil inlet and oil outlet sides of the injection cylinder, thereby solving the problem of oil leakage and improving the injection accuracy.

[0089] Based on the above technical effects, the high-precision metal injection molding mechanism provided in this embodiment can achieve stepless speed regulation from 0.05 to 5 m / s, has high speed and high acceleration, can achieve high-precision injection at high speed, and improve product performance.

[0090] Example 2:

[0091] Based on the high-precision metal injection molding mechanism provided in Example 1, this embodiment provides a high-precision metal injection molding method, including the following steps:

[0092] S1: The injection unit uses an integrated piston and piston rod connected to the feed screw, shortening the length of the injection unit and reducing deformation of the metal injection molding mechanism;

[0093] S2: Increase the sealing performance of the integrated piston, piston rod and injection cylinder;

[0094] S3: The injection unit is equipped with a deceleration structure to slow down the injection speed at the end of the injection stage;

[0095] S4: High-frequency response servo valves are installed on both the oil inlet and outlet sides of the injection cylinder to respond to user commands with high dynamic response.

[0096] The high-precision metal injection molding method provided in this embodiment is used to perform magnesium alloy metal injection molding, which has the characteristic of effective injection precision control. The specific principle is described in the first embodiment and will not be elaborated here.

[0097] Example 3:

[0098] Based on the high-precision metal injection molding mechanism provided in the first embodiment or the high-precision metal injection molding method provided in the second embodiment, this embodiment provides a high-precision metal injection molding machine. The high-precision metal injection molding machine includes the high-precision metal injection molding mechanism described above.

[0099] The high-precision metal injection molding machine provided in this embodiment is used to perform magnesium alloy metal injection molding, which has the characteristic of effective injection precision control. The specific principles thereof are described in the first or second embodiment and will not be elaborated here.

[0100] It should be noted that for the aforementioned method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that this application is not limited by the order of the actions described, because according to this application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by this application.

[0101] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0102] The above is only an exemplary embodiment of the present disclosure and cannot be used to limit the scope of the present disclosure. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure herein, those skilled in the art will easily think of the implementation scheme of the present disclosure. This application is intended to cover any variation, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the art that are not recorded in the present disclosure. The description and examples are to be regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A high-precision metal injection molding mechanism, comprising an injection unit, a hydraulic unit, and a feeding unit, characterized in that: The injection unit (100) comprises an injection cylinder (102), and an integrated piston and piston rod (101) arranged in the injection cylinder (102); The feeding unit (200) comprises a feeding screw (201) and a material storage drive assembly (203); the two ends of the integrated piston and piston rod (101) are respectively connected to the feeding screw (201) and the material storage drive assembly (203), and are used to drive the integrated piston and piston rod (101) to push the feeding screw (201) to move through the driving action of the material storage drive assembly (203), so as to realize the delivery of injection liquid; High-frequency response servo valves are provided on both the oil inlet side and the oil outlet side of the injection cylinder (102).

2. A high-precision metal injection molding mechanism as claimed in claim 1, characterized in that: The oil outlet side of the injection cylinder (102) is provided with a first oil outlet (1021) and a second oil outlet (1022), wherein the second oil outlet (1022) is close to the end of the injection cylinder (102), and the diameter of the second oil outlet (1022) is smaller than that of the first oil outlet (1021).

3. A high-precision metal injection molding mechanism as claimed in claim 1, characterized in that: Cylinder covers (103) are provided at both ends of the injection cylinder (102) for sealing the inner cavity of the injection cylinder (102); an oil drain groove (1031) is provided on the cylinder cover (103).

4. A high-precision metal injection molding mechanism as claimed in claim 1, characterized in that: A rotating sealing ring (106) is provided on the piston section of the integrated piston and piston rod (101) so as to enable the integrated piston and piston rod (101) to be in close contact with the inner wall of the injection cylinder (102); A pressure reducing ring (105) and a wear-resistant ring (104) are also provided on the piston section of the integrated piston and piston rod (101); the pressure reducing ring (105) is provided on both sides of the rotating sealing ring (106); and the wear-resistant ring (104) is provided on a side of the pressure reducing ring (105) away from the rotating sealing ring (106).

5. A high-precision metal injection molding mechanism as claimed in claim 1, characterized in that: The material storage drive assembly (203) comprises a servo motor (2031) and a transmission shaft (2035); the transmission shaft (2035) is connected to the integrated piston and piston rod (101) via a spline; the servo motor (2031) drives the transmission shaft (2035) to rotate via a transmission belt, thereby causing the integrated piston and piston rod (101) to move.

6. A high-precision metal injection molding mechanism as claimed in claim 1, characterized in that: It also includes a hydraulic unit, the hydraulic unit including a first high-response accumulator and at least one nitrogen gas storage bottle, the high-pressure nitrogen side of the high-response accumulator is connected to the nitrogen gas storage bottle, and the oil outlet side of the high-response accumulator is connected to the oil inlet side of the injection cylinder (102); A proportional throttle valve is arranged on the oil outlet side of the high-response accumulator and the oil inlet side of the injection cylinder (102), and a second high-response accumulator is arranged on the proportional throttle valve.

7. A high-precision metal injection molding mechanism as claimed in claim 1, characterized in that: The invention also comprises a shifting unit (400), wherein the shifting unit (400) comprises an injection seat (409), a shifting oil cylinder (402), and a shifting piston rod (403) arranged in the shifting oil cylinder (402), wherein the shifting piston rod (403) is connected to a fixed mold plate, and the injection seat (409) is connected to a barrel, and the injection seat (409) is used to push the shifting oil cylinder (402) to move, so that the barrel and the fixed mold plate move relative to each other.

8. A high-precision metal injection molding mechanism as claimed in claim 1, characterized in that: The invention also comprises a rotating unit (500), wherein the rotating unit (500) comprises a rotating oil cylinder (502) and a rotating piston rod (503) arranged in the rotating oil cylinder (502); the rotating unit (500) further comprises a middle bottom plate (404) and a lower bottom plate (501) connected to each other, wherein the middle bottom plate (404) and the lower bottom plate (501) are respectively connected to the rotating oil cylinder (502), and a rotating positioning pin (504) is arranged between the middle bottom plate (404) and the lower bottom plate (501). When the rotating piston rod (503) moves in the rotating oil cylinder (502), the middle bottom plate (404) rotates around the lower bottom plate (501) with the rotating positioning pin (504) as the center.

9. A high-precision metal injection molding method, based on the high-precision metal injection molding mechanism according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1: The injection unit uses an integrated piston and piston rod connected to the feed screw, which shortens the length of the injection unit and reduces the deformation of the metal injection molding mechanism; S2: Increase the sealing performance of the integrated piston, piston rod and injection cylinder; S3: The injection unit is provided with a deceleration structure so that the injection speed is decelerated and buffered at the final stage of injection; S4: High-frequency response servo valves are installed on the oil inlet and outlet sides of the injection cylinder to respond to user instructions with high dynamics.

10. A high-precision metal injection molding machine, characterized in that: It comprises the high-precision metal injection molding mechanism as described in any one of claims 1 to 8.

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