Feeding formula for a soft magnetic powder molded part for a solenoid valve and its preparation method

Abstract

The present invention relates to the technical field of metal powder injection molding, and particularly to a feed formula and a preparation method for a soft magnetic powder molded part for a solenoid valve, comprising the following materials in mass ratio: 9% of a binder and 91% of soft magnetic powder. The binder comprises the following raw materials in mass ratio: 86% of polyoxymethylene (POM), 5% of polyethylene (PE), 3% of polypropylene (PP), 1.5% of stearic acid, 1.5% of antioxidant, and 3% of paraffin wax. The soft magnetic powder comprises the following raw material: FeNi50.

Description

Technical Field

[0001] The present invention relates to the technical field of metal powder injection molding, and particularly to a feed formula for a soft magnetic powder molded part for a solenoid valve and a preparation method thereof. Background Art

[0002] The application of solenoid valve switches in the field of automation is indeed very extensive, and they play an important role in industrial automation control systems. However, when producing solenoid valve soft magnetic parts such as solenoid valve switches by the existing CNC process, there are some technical problems, which mainly include the complexity of the production process, the low production efficiency, and the material waste problem, resulting in relatively high costs.

[0003] First of all, the production process of the CNC process is usually relatively complex, which not only includes multiple steps such as programming, setting, machining, and post-processing, but also requires precise control and operation in each step. Such a cumbersome process not only increases the production time, but also requires highly skilled operators to operate, further increasing the labor cost.

[0004] Secondly, due to the complexity and multi-step operation of the CNC process, the production efficiency is relatively low. The processing time for each part is relatively long, which cannot meet the requirements of large-scale production, and to a certain extent, limits the market supply capacity of solenoid valve switches.

[0005] In addition, a large amount of material waste will be generated during the processing of the CNC process. Since the cutting processing method is used to cut the raw material into the required shape, a large amount of material is cut off to form waste, resulting in low material utilization rate. Especially when processing parts with complex shapes, the material waste is more serious.

[0006] Therefore, a feed formula for a soft magnetic powder molded part for a solenoid valve and a preparation method thereof are proposed. Summary of the Invention

[0007] In order to overcome the deficiencies of the prior art, the present invention provides a feed formula for a soft magnetic powder molded part for a solenoid valve and a preparation method thereof.

[0008] To solve the above technical problems, the present invention provides the following technical solution: a feed formula for a soft magnetic powder molded part for a solenoid valve, including the following materials in mass ratio: 9% of binder and 91% of soft magnetic powder. The binder includes the following raw materials in mass ratio: 86% of polyoxymethylene (POM), 5% of polyethylene (PE), 3% of polypropylene (PP), 1.5% of stearic acid, 1.5% of antioxidant, and 3% of paraffin wax. The soft magnetic powder includes the following raw material: FeNi50.

[0009] A preparation method for a soft magnetic powder molded part for a solenoid valve includes the following steps:

[0010] S1. Add raw materials into a kneader according to the feeding formula for kneading, and then extrude and pelletize to obtain MIM raw materials.

[0011] S2. Pour the MIM raw materials into an injection molding machine, heat them to the melting temperature, inject the melted raw materials into a mold for cooling and shaping, and take them out of the mold after shaping to obtain green compacts.

[0012] S3. Send the green compacts into a debinding bath to remove part of the binder, and then send them into a debinding furnace to remove the remaining binder to obtain brown compacts.

[0013] S4. Send the brown compacts into a sintering furnace, control the sintering temperature just below the melting point of the metal, and let the metal powder fuse together to form an integral body to obtain solenoid valve soft magnetic parts.

[0014] S5. Use a surface grinding process to machine the plane that needs to be sealed on the solenoid valve soft magnetic parts.

[0015] As a preferred technical solution of the present invention, the following steps are further included between S4 and S5:

[0016] S4.5. For the solenoid valve soft magnetic parts with bending deformation during sintering, put the solenoid valve soft magnetic parts into a special profiling shaping mold installed on a four-column hydraulic press, and cooperate with the pressure applied by the four-column hydraulic press for shaping.

[0017] As a preferred technical solution of the present invention, S1 further includes the following steps:

[0018] S101. Before blanking, turn on the press head for 10 minutes to let the water vapor volatilize, and then pelletize.

[0019] S102. Preheat the kneader to 185 - 195 °C.

[0020] S103. Pour half of the soft magnetic powder in terms of mass ratio.

[0021] S104. Pour the binder in terms of mass ratio.

[0022] S105. Stir slowly, with specific parameters of 15 - 20 r / min.

[0023] S106. After 20 minutes, add the remaining soft magnetic powder.

[0024] S107. Increase the stirring speed, with specific parameters of 25 - 35 r / min. After stirring for 30 - 40 minutes, the raw materials form a maltose-like shape. Let it stand and observe the state every 10 minutes. Lower the set temperature to 160 - 170 °C, turn on the press head to let the water vapor volatilize, scrape off the soft magnetic powder or binder in the dead corners with a scraper, and then extrude and pelletize.

[0025] As a preferred technical solution of the present invention, the mold in S2 is designed to add a process notch to the flat grinding surface of the green body. The size of the process notch is larger than the machining amount of the flat grinding, so that the burrs generated by the flat grinding will not protrude from the process notch.

[0026] As a preferred technical solution of the present invention, the method further includes a surface grinding device, which includes a power control cabinet. A control circuit is arranged in the power control cabinet. A rotary worktable is rotatably installed on the tabletop of the power control cabinet. A driving mechanism for driving the rotary worktable to rotate at a fixed torque is installed in the power control cabinet. A plurality of jigs for clamping the solenoid valve soft magnetic parts are equidistantly installed on the tabletop of the rotary worktable. Clamping grooves adapted to the solenoid valve soft magnetic parts are provided on the jigs. A surface grinding assembly for grinding the sealing surface of the solenoid valve soft magnetic parts is installed on the tabletop of the power control cabinet. The surface grinding assembly includes a fixed end, a lifting end, a pushing end and a surface grinding motor. The grinding wheel is installed on the transmission shaft of the surface grinding motor. The grinding depth is adjusted by the up and down lifting of the lifting end. The feed amount is adjusted by the telescopic movement of the pushing end. The grinding speed is adjusted by controlling the rotation speed of the surface grinding motor. An industrial camera table is installed on the tabletop of the power control cabinet on one side of the surface grinding assembly. An industrial camera is installed on the industrial camera table. A dust suction pipe is rotatably installed through a hole in the middle of the rotary worktable. A plurality of dust suction holes are provided on the circumferential side of the dust suction pipe. A dust suction device is installed in the power control cabinet and the dust suction end is connected to the dust suction pipe.

[0027] As a preferred technical solution of the present invention, S5 includes the following steps:

[0028] S501. The solenoid valve soft magnetic part is fixed in the jig through feeding. The rotary worktable rotates at a fixed torque to align the solenoid valve soft magnetic part with the surface grinding assembly. The surface grinding motor drives the grinding wheel to rotate. The telescopic motor pushes the surface grinding motor to move towards the solenoid valve soft magnetic part, so that the grinding wheel grinds the surface of the solenoid valve soft magnetic part.

[0029] S502. The industrial camera takes a photo of the surface-ground solenoid valve soft magnetic part. After image processing and analysis, relevant values of the surface roughness, flatness and burr length of the solenoid valve soft magnetic part are obtained.

[0030] S503. A threshold value is set for the burr length, and weight distribution is carried out for the influence of the grinding depth, grinding speed and feed amount on the burr length according to the expert evaluation method. When the burr length reaches the threshold value, the parameters of the grinding depth, grinding speed and feed amount are reduced respectively according to the allocated weight ratio, so that the control circuit adjusts the frequency, height and advancing speed of the surface grinding motor to ensure that the burrs do not exceed the process notch.

[0031] S504. Threshold values are also set for the surface roughness and flatness, and when the threshold values are reached, the parameters of the grinding depth, grinding speed and feed amount are increased respectively according to the allocated weight ratio.

[0032] S505. When the values of the burr length, surface roughness, and flatness all reach the thresholds, the machine needs to be stopped, and the surface grinding assembly and the grinding wheel need to be maintained or replaced.

[0033] Compared with the prior art, the beneficial effects that the present invention can achieve are as follows:

[0034] 1. Through the design of the feeding formula, the solenoid valve soft magnetic parts prepared by MIM can meet the performance requirements during the use of the solenoid valve. By utilizing the advantages of MIM preparation, the preparation process is simplified, the labor cost and production time are reduced, and a large number of solenoid valve soft magnetic parts can be produced simultaneously, greatly improving the production efficiency.

[0035] 2. By adding a surface grinding process and the setting of a process notch after the traditional steps of preparing solenoid valve soft magnetic parts by MIM, while ensuring the surface roughness and flatness required for the sealing of the solenoid valve soft magnetic parts, there is only one surface to be ground in the post-processing, and the step of removing burrs is also saved, making the process simple and the efficiency improved. At the same time, the waste of raw materials is reduced, which is beneficial to cost reduction.

[0036] 3. Through the setting of the surface grinding assembly and the industrial camera platform, the relevant numerical values of the surface grinding state of the solenoid valve soft magnetic parts can be obtained in real time, and the relevant parameters of the surface grinding assembly can be set to ensure that the solenoid valve soft magnetic parts reach a qualified and uniform quality level, and the stability information of the surface grinding assembly and the grinding wheel can be timely feedback to avoid the appearance of a large number of unqualified products. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic flow chart of the preparation method of the present invention;

[0038] Figure 2 is a schematic structural diagram of the surface grinding equipment for the preparation method of the present invention;

[0039] Figure 3 is a schematic structural diagram of the surface grinding assembly of the present invention.

[0040] Among them: 1. Power control cabinet; 2. Rotary worktable; 3. Fixture; 4. Surface grinding assembly; 41. Fixed table; 42. Linear guide rail 1; 43. Lifting table; 44. Linear guide rail 2; 45. Motor frame; 46. Motor; 47. Screw; 48. Motor bracket; 49. Telescopic motor; 5. Industrial camera platform; 6. Dust suction pipe; 7. Surface grinding motor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments. However, the following embodiments are only the preferred embodiments of the present invention, not all of them. Based on the embodiments in the implementation manners, other embodiments obtained by those skilled in the art without creative efforts all fall within the protection scope of the present invention. The experimental methods in the following embodiments are all conventional methods unless otherwise specified, and the materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0042] Example: As Figures 1-3 shown, a feeding formula for a soft magnetic powder molded part for a solenoid valve includes the following materials in mass ratio: 9% binder and 91% soft magnetic powder. The binder includes the following raw materials in mass ratio: 86% polyoxymethylene POM, 5% polyethylene PE, 3% polypropylene PP, 1.5% stearic acid, 1.5% antioxidant and 3% paraffin wax. The soft magnetic powder includes the following raw materials: FeNi50.

[0043] A preparation method for a soft magnetic powder molded part for a solenoid valve includes the following steps:

[0044] S1. Add raw materials to a mixer according to the feeding formula, mix them, and then extrude and granulate to obtain MIM raw materials.

[0045] S2. Pour the MIM raw materials into an injection molding machine, heat them to the melting temperature, inject the melted raw materials into a mold to cool and solidify, and take them out of the mold after solidification to obtain green compacts.

[0046] S3. Send the green compacts into a degreasing tank to remove part of the binder, and then send them into a degreasing furnace to remove the remaining binder to obtain brown compacts.

[0047] S4. Send the brown compacts into a sintering furnace, and control the sintering temperature just below the melting point of the metal to make the metal powder fuse together to form a whole, obtaining a solenoid valve soft magnetic part.

[0048] S4.5. For the solenoid valve soft magnetic part with bending deformation during sintering, put the solenoid valve soft magnetic part into a special profiling shaping mold installed on a four-column hydraulic press, and perform shaping in cooperation with the pressure applied by the four-column hydraulic press to ensure the product size and functional requirements and meet the appearance requirements after assembly.

[0049] S5. The plane of the solenoid valve soft magnetic part needs to be sealed during use. However, during the shrinkage process of sintering the solenoid valve soft magnetic part, it is impossible to ensure the surface requirements for sealing. Therefore, use a surface grinding process to process the plane of the solenoid valve soft magnetic part that needs to be sealed. The surface requirements of the solenoid valve soft magnetic part are flatness of 0.02 and roughness Ra of 0.6, so as to meet the sealing requirements.

[0050] S1 also includes the following steps:

[0051] S101. Before blanking, open the press head for 10 minutes to let the water vapor volatilize, and then granulate.

[0052] S102. Preheat the mixer to 185 - 195 °C.

[0053] S103. Pour in half of the soft magnetic powder by mass ratio.

[0054] S104. Pour in the binder by mass ratio.

[0055] S105. Stir slowly, with specific parameters of 15 - 20 r / min.

[0056] S106. After 20 minutes, add the remaining soft magnetic powder.

[0057] S107. Increase the stirring speed, with specific parameters of 25 - 35 r / min. After stirring for 30 - 40 minutes, the raw material forms a maltose-like shape. Let it stand and observe the state every 10 minutes. Lower the set temperature to 160 - 170 °C, open the press head to let the water vapor volatilize, scrape off the soft magnetic powder or binder in the dead corners with a scraper, and then extrude and granulate.

[0058] During the surface grinding process, due to the low hardness of the soft magnetic material, edge burrs will be generated and are difficult to remove. To avoid the adverse effects of this phenomenon on actual use, the mold in S2 is designed to add a process notch to the surface grinding surface of the green body. The size of the process notch is larger than the machining amount of the surface grinding, so that the burrs generated by the surface grinding will not protrude beyond the process notch.

[0059] Such as Figure 2 and Figure 3As shown, the method further includes a surface grinding device, which is characterized by including a power control cabinet 1. A control circuit is provided inside the power control cabinet 1. A rotary worktable 2 is rotatably installed on the tabletop of the power control cabinet 1. A driving mechanism for driving the rotary worktable 2 to rotate at a fixed torque is installed inside the power control cabinet. The driving mechanism for driving the rotary worktable 2 to rotate at a fixed torque is a well-known prior art, usually composed of a motor and a gear set, which will not be elaborated here. A number of jigs 3 for clamping solenoid valve soft magnetic parts are equidistantly installed on the tabletop of the rotary worktable 2. Clamping grooves adapted to the solenoid valve soft magnetic parts are provided on the jigs 3, and the overall height of the clamping grooves is slightly lower than that of the solenoid valve soft magnetic parts. A surface grinding assembly 4 for grinding the sealing surface of the solenoid valve soft magnetic parts is installed on the tabletop of the power control cabinet 1. The surface grinding assembly 4 includes a fixed end, a lifting end, a feeding end and a surface grinding motor 7. The grinding wheel is installed on the transmission shaft of the surface grinding motor 7. The adjustment of the grinding depth is achieved by the up and down movement of the lifting end. The adjustment of the feed rate is achieved by the telescopic movement of the feeding end. The adjustment of the grinding speed is achieved by controlling the speed of the surface grinding motor 7. Specifically, the fixed end includes a fixed table 41, and the fixed table 41 is fixedly installed on the tabletop of the power control cabinet 1. A linear guide rail 42 is installed on the fixed table 41. The lifting end includes a lifting table 43, and the lifting table 43 is installed on the moving part of the linear guide rail 42. A linear guide rail 44 is installed on the bottom surface of the lifting table 43. The feeding end includes a motor frame 45, and the motor frame 45 is installed on the moving part of the linear guide rail 44. The surface grinding motor 7 is installed on the motor frame 45. A motor 46 is installed on the fixed table 41. A screw rod 47 is installed on the transmission shaft of the motor 46. A motor frame 48 is threadedly connected to the screw rod 47. A telescopic motor 49 is installed on the motor frame 48. The transmission shaft of the telescopic motor 49 is connected to the motor frame 45. An industrial camera table 5 is installed on the tabletop of the power control cabinet 1 on one side of the surface grinding assembly 4. A dust suction pipe 6 is rotatably installed through a hole in the middle of the rotary worktable 2. A number of dust suction holes are provided on the circumferential side of the dust suction pipe 6. A dust suction device is installed inside the power control cabinet 1 and the dust suction end is connected to the dust suction pipe 6. An industrial camera is installed on the industrial camera table 5. The industrial camera is used to photograph the surface of the solenoid valve soft magnetic parts to obtain the grinding effect and the length of the burr. The number of industrial cameras can be multiple and their positions and angles are different, and it is based on obtaining three data of the burr length, surface roughness and flatness of the solenoid valve soft magnetic parts after processing. Based on the above industrial camera, in cooperation with devices such as an image acquisition card and a computer, an embedded machine vision system is formed, which can obtain the surface roughness, flatness and burr length of the ground solenoid valve soft magnetic parts through photographing. The specific machine vision system is a well-known prior art and will not be elaborated here. It should be noted that the movement amplitude of the equipment and structure of the present application is controlled by setting sensors, and the sensor control method is a well-known prior art and will not be elaborated here. In addition, the loading and unloading function of the present application can be realized by adding a manipulator or manually, and the present application does not make a limitation.After grinding, the solenoid valve soft magnetic part is rotationally and fixedly moved by the rotary table 2 to correspond to the industrial camera table 5. The industrial camera takes a photo of the ground solenoid valve soft magnetic part, and judges whether the grinding effect and burr are within a reasonable range according to the photo. When the burr amount is too large or the grinding effect is not good, the control circuit adjusts the frequency, height and advancing speed of the surface grinding motor to adjust the grinding depth, grinding speed and feed rate, so as to adjust and obtain the best grinding effect, grinding efficiency and burr amount.

[0060] S5 includes the following steps:

[0061] S501. The solenoid valve soft magnetic part is fixed in the fixture 3 through feeding. The rotary table 2 rotates at a fixed distance to make the solenoid valve soft magnetic part correspond to the surface grinding assembly. The surface grinding motor 7 drives the grinding wheel to rotate, and the telescopic motor 49 pushes the surface grinding motor 7 to move towards the solenoid valve soft magnetic part, so that the grinding wheel can grind the surface of the solenoid valve soft magnetic part.

[0062] S502. The industrial camera takes a photo of the surface-ground solenoid valve soft magnetic part. After image processing and analysis, the relevant values of the surface roughness, flatness and burr length of the solenoid valve soft magnetic part are obtained.

[0063] S503. Set a threshold for the burr length, and allocate weights to the influence of the grinding depth, grinding speed and feed rate on the burr length according to the expert evaluation method. When the burr length reaches the threshold, reduce the parameters of the grinding depth, grinding speed and feed rate respectively according to the allocated weight ratio, so that the control circuit adjusts the frequency, height and advancing speed of the surface grinding motor to ensure that the burr does not exceed the process notch.

[0064] S504. Set thresholds for the surface roughness and flatness as well, and when the thresholds are reached, increase the parameters of the grinding depth, grinding speed and feed rate respectively according to the allocated weight ratio.

[0065] S505. When the values of the burr length, surface roughness and flatness all reach the thresholds, it is necessary to stop the machine and maintain or replace the surface grinding assembly 4 and the grinding wheel.

[0066] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those skilled in the art to which the present invention pertains.

Claims

1. A method for preparing soft magnetic powder molded parts for solenoid valves, characterized in that: The steps include: S1, adding raw materials into a mixer according to the feeding formula, mixing, and then extruding and granulating to obtain MIM raw materials; S2, pouring the MIM raw material into the injection molding machine, heating it to the melting temperature, injecting the molten raw material into the mold to cool and shape it, taking it out from the mold after shaping to obtain a green body, and designing the mold so that the flat grinding surface of the green body adds a process gap, and the size of the process gap is larger than the processing amount of flat grinding, so that the burrs generated by flat grinding will not protrude from the process gap; S3, sending the raw embryo into a degreasing tank to remove part of the binder, and then sending it into a degreasing furnace to remove the remaining binder to obtain a brown embryo; S4, sending the brown embryo into the sintering furnace, and controlling the sintering temperature just below the melting point of the metal, so that the metal powder is fused together to form a whole, and the solenoid valve soft magnetic parts are obtained; S5. Use flat grinding process to process the flat surface of the solenoid valve soft magnetic parts that need to be sealed; The preparation method also includes a flat grinding device, which includes an electric control cabinet (1), a control circuit is arranged in the electric control cabinet (1), a rotary table (2) is rotatably mounted on the table of the electric control cabinet (1), a driving mechanism for driving the rotary table (2) to rotate at a fixed torque is installed in the electric control cabinet, a plurality of fixtures (3) for clamping the solenoid valve soft magnetic parts are equidistantly mounted on the table of the rotary table (2), a clamping groove adapted to the solenoid valve soft magnetic parts is opened on the fixture (3), and a fixture for grinding the solenoid valve soft magnetic parts is installed on the table of the electric control cabinet (1). A flat grinding assembly (4) for the sealing surface of a magnetic part, the flat grinding assembly (4) comprising a fixed end, a lifting end, a propulsion end and a flat grinding motor (7), the grinding wheel being mounted on a transmission shaft of the flat grinding motor (7), the grinding depth being adjusted by lifting and lowering the lifting end, the feed amount being adjusted by telescoping the propulsion end, and the grinding speed being adjusted by speed control of the flat grinding motor (7), the table of the power control cabinet (1) being mounted with an industrial camera table (5) on one side of the flat grinding assembly (4), the industrial camera table (5) being mounted with an industrial camera; The S5 comprises the following steps: S501, the solenoid valve soft magnetic part is fixed in the fixture (3) after loading, the rotary table (2) rotates at a fixed torque to make the solenoid valve soft magnetic part correspond to the flat grinding component, the flat grinding motor (7) drives the grinding wheel to rotate, and the telescopic motor (49) drives the flat grinding motor (7) to move toward the solenoid valve soft magnetic part, so that the grinding wheel can grind the surface of the solenoid valve soft magnetic part; S502, an industrial camera takes a picture of the flat-ground solenoid valve soft magnetic part, and obtains relevant values ​​of the surface roughness, flatness and burr length of the solenoid valve soft magnetic part after image processing and analysis; S503, setting a threshold for the burr length, and assigning weights to the influence of grinding depth, grinding speed and feed rate on the burr length according to the expert evaluation method. When the burr length reaches the threshold, the parameters of grinding depth, grinding speed and feed rate are respectively reduced according to the assigned weight ratio, so that the control circuit adjusts the frequency, height and advancement speed of the flat grinding motor to ensure that the burr does not exceed the process gap. S504, setting thresholds for surface roughness and flatness, and when the thresholds are reached, increasing the parameters of grinding depth, grinding speed, and feed rate respectively according to the assigned weight ratios; S505: When the values ​​of the burr length, surface roughness and flatness all reach the threshold value, the machine needs to be stopped and the flat grinding assembly (4) and the grinding wheel need to be maintained or replaced.

2. The method for preparing a soft magnetic powder molded part for a solenoid valve according to claim 1, characterized in that: The following steps are also included between S4 and S5: S4.

5. When the solenoid valve soft magnetic parts are bent and deformed during sintering, the solenoid valve soft magnetic parts are placed in a special imitation shaping mold installed on a four-column hydraulic press and shaped with the pressure of the four-column hydraulic press.

3. The method for preparing a soft magnetic powder molded part for a solenoid valve according to claim 1, characterized in that: S1 also includes the following steps: S101, before unloading, open the press head for 10 minutes to allow the water vapor to evaporate before granulation; S102, preheat the mixer to 185-195°C; S103, pouring in half the mass ratio of soft magnetic powder; S104, pouring a binder in a mass ratio; S105, slow stirring, the specific parameters are 15-20r / min; S106, after 20 minutes, add the remaining soft magnetic powder; S107, increase the stirring speed, the specific parameter is 25-35r / min, after stirring for 30-40 minutes, the raw material becomes maltose-like, let it stand and observe the state every 10 minutes, lower the set temperature to 160-170℃, open the pressure head to let the water vapor evaporate, use a scraper to scrape off the soft magnetic powder or binder in the dead corner, and then extrude and granulate.

4. The method for preparing a soft magnetic powder molded part for a solenoid valve according to claim 1, characterized in that: A hole is opened in the middle of the rotary workbench (2) and a dust suction pipe (6) is rotatably installed thereon. A plurality of dust suction holes are opened on the peripheral side of the dust suction pipe (6). A dust suction device is installed in the power control cabinet (1) and the dust suction end is connected to the dust suction pipe (6).

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