A method for performing electric spark roughening treatment on the ball screw raceway surface

Abstract

The invention relates to a machining method, in particular to a method for performing electric spark roughening treatment on a ball screw raceway surface, comprising the steps of setting discharge parameters, rotating the speed of a discharge spindle, slowly adjusting the vertical position of a solid ball head cylindrical tungsten rod electrode on a vertical transmission shaft by a servo motor, so that the electrode is slowly fed to a thread section at a starting end of the ball screw, until a reasonable discharge gap is reached between the solid ball head cylindrical tungsten rod electrode and the thread raceway surface of the ball screw; setting the speed of a stepper motor, a horizontal scanning speed of the solid ball head cylindrical tungsten rod electrode matched therewith, and a spraying speed of a coolant, performing servo control on the solid ball head cylindrical tungsten rod electrode by a servo motor, realizing compensation of a tool electrode, so that the ball screw and the electrode are always in a suitable discharge gap, and the like; compared with the prior art, after the ball screw is treated by the electric spark treatment, micro-pits on the outer raceway surface of the ball screw can reduce the friction and wear of the ball screw pair, thereby increasing the product life.

Description

Technical Field

[0001] The invention relates to a mechanical processing method, in particular to a method for performing electric spark roughening treatment on a ball screw raceway surface. Background Art

[0002] like Figure 1 As shown, the ball screw consists of a screw 1, a nut 2 with an integrated reverser 3, a steel ball 4, etc. Its main function is to convert rotational motion into linear motion or torque into axial repetitive force. It is the most commonly used transmission element in tool machinery and precision machinery. It has the characteristics of stable, accurate and efficient transmission. It is widely used in machine tools, robots, medical equipment, semiconductor manufacturing, microelectronics assembly and other fields. During the working process, a tunnel-shaped ball raceway is formed between the outer raceway surface of the screw and the inner raceway surface of the nut. The rotation of the screw drives the steel ball to roll in a circle in the track to transfer the load and realize the linear reciprocating motion of the nut. The outer raceway surface of the screw and the steel ball, and the steel ball and the inner raceway surface of the nut contact to form a relative motion friction pair.

[0003] In industries such as machine tools, semiconductor manufacturing, and microelectronics assembly, screws are required to frequently reciprocate at high speeds. With high-frequency transmission, friction and friction heat are bound to be generated between the friction pairs, which in turn leads to wear of the screw outer raceway, steel balls, and nut inner raceway, ultimately destroying the screw's accuracy, stability, and life.

[0004] In order to reduce the friction and wear between the friction pairs, the prior art is to open an oil filling hole at the relevant part of the nut, open a cavity connected to the oil filling hole inside the nut, open through holes distributed at equal distances on the inner wall at the bottom of the cavity to communicate with the steel ball, and use an oil gun to lubricate the steel ball inside the nut through the oil filling hole. However, because the spherical surface of the steel ball of the screw fits with the outer raceway surface of the screw and the inner raceway surface of the nut, under the action of the axial load, the lubricating oil cannot enter the friction pair well or squeeze out from the raceway surface and the steel ball, resulting in dry friction between the steel ball, the screw and the nut, which not only aggravates the wear, but also causes oil dripping and waste, and pollutes the environment to a certain extent. At the same time, the steel ball is spherical, the outer raceway surface of the screw and the inner raceway surface of the nut are in the shape of an arc groove, and the contact form is surface contact, resulting in a large contact area between the steel ball and the screw and the nut, further aggravating the friction and wear of the screw pair.

[0005] In addition, the raceway surface of the nut, the reverser mounting surface and other essential surfaces are difficult to process internal structures, and also have the function of adjusting the screw preload. If a cavity and oil channel connected to the oil injection hole are opened inside the nut, the structural complexity of the nut body and the difficulty of design and processing will be increased. Summary of the invention

[0006] In view of the above technical problem or one of the technical problems existing in the prior art, the present invention proposes a method for performing electric spark roughening treatment on the ball screw raceway surface. The technical solution adopted comprises the following steps:

[0007] Step 1: Perform ultrasonic cleaning on the finished screw rod for more than two times to remove surface oil and other debris, and dry it naturally in the air after cleaning;

[0008] Step 2: Install the cleaned and dried screw rod horizontally on the EDM machine through the top and the clamp to ensure that the spatial posture of the screw rod's rotation axis is horizontal;

[0009] Step 3: Connect the clamp to the high-precision stepper motor to drive the screw to rotate at a constant speed;

[0010] Step 4: Check and adjust the rotation accuracy of the screw rod to within the set runout error, and then pause the rotation of the stepper motor;

[0011] Step 5, clamping the tool electrode on the rotating discharge spindle driven by the servo motor of the EDM machine, the spatial posture of the spindle axis is vertical, and the servo motor speed is adjustable; the tool electrode is a solid ball-head cylindrical tungsten rod electrode, the diameter of which is equal to the diameter of the steel ball, and the convex and concave matching of the spiral outer raceway surface on the screw rod; during the discharge process, the outer raceway surface of the screw rod is reversely copied to the ball head end of the solid ball-head cylindrical tungsten rod electrode, so that the working end of the electrode continues to maintain a ball head shape;

[0012] Step 6: Turn on the power of the EDM machine, connect the screw to the negative pole, and connect the solid ball-end cylindrical tungsten rod electrode to the positive pole;

[0013] Step 7: Adjust the horizontal position of the solid ball-end cylindrical tungsten rod electrode so that its vertical axis is coplanar with the horizontal axis of the screw rod;

[0014] Step 8: Adjust the horizontal position of the solid ball-end cylindrical tungsten rod electrode so that its vertical projection coincides with the thread section at the starting end of the screw rod;

[0015] Step 9, set the discharge parameters, rotate the speed of the discharge spindle, and slowly adjust the vertical position of the solid ball-end cylindrical tungsten rod electrode on the vertical transmission shaft through the servo motor, so that it slowly feeds to the thread section at the starting end of the screw rod until the solid ball-end cylindrical tungsten rod electrode and the thread track surface of the screw rod reach a reasonable discharge gap;

[0016] Step 10, setting the rotation speed of the stepper motor, the horizontal scanning speed of the solid ball-end cylindrical tungsten rod electrode matched therewith, and the spraying speed of the coolant, and performing servo control on the solid ball-end cylindrical tungsten rod electrode through the servo motor to realize the compensation of the tool electrode, so that the lead screw and the electrode are always in a suitable discharge gap;

[0017] Step 11: With the uniform rotation of the screw and the horizontal uniform movement of the tool electrode, the solid ball-end cylindrical tungsten rod electrode ablates the outer guide surface of the entire screw, and randomly superimposed and disorderly arranged micro-pits are generated on the outer guide surface of the screw, thereby forming a capillary lubrication channel.

[0018] Compared with the prior art, the micro-pits on the outer raceway surface of the ball screw after the electric spark treatment of the present invention can reduce the contact area between the screw and the steel ball, so that the lubricating oil can directly and evenly act on the friction pair, avoiding the pressure extrusion of the lubricating oil between the guide surface and the steel ball, improving the oil catching, oil storage and self-lubricating performance of the ball screw pair, thereby reducing the friction and wear of the ball screw pair and increasing the product life. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of an existing screw rod.

[0020] Figure 2 It is a structural schematic diagram and a partial enlarged diagram of the ball screw after the electric spark treatment of the present invention.

[0021] Figure 3 It is a structural schematic diagram of a nut of the present invention.

[0022] Figure 4 It is a structural schematic diagram of the oil supply cleaner of the present invention.

[0023] Figure 5 A schematic structural diagram of the oil supply cleaner disc of the present invention.

[0024] Figure 6 A schematic cross-sectional view of the oil supply cleaner disc of the present invention.

[0025] Figure 7 A schematic structural diagram of the oil supply head, spring and sealing screw of the oil supply cleaner of the present invention.

[0026] Figure 8 A schematic structural diagram of a cleaning head, a spring and a sealing screw of an oil supply cleaner of the present invention. DETAILED DESCRIPTION

[0027] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0028] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] A method for performing electric spark treatment on a lead screw of a ball screw comprises the following steps:

[0031] Step 1: Perform ultrasonic cleaning on the finished screw rod for more than two times to remove surface oil and other debris, and dry it naturally in the air after cleaning;

[0032] Step 2: Install the cleaned and dried screw rod horizontally on the EDM machine through the top and the clamp to ensure that the spatial posture of the screw rod's rotation axis is horizontal;

[0033] Step 3: Connect the clamp to the high-precision stepper motor to drive the screw to rotate at a constant speed;

[0034] Step 4: Check and adjust the rotation accuracy of the screw rod to within the set runout error, and then pause the rotation of the stepper motor;

[0035] Step 5, clamping the tool electrode on the rotating discharge spindle driven by the servo motor of the EDM machine, the spatial posture of the spindle axis is vertical, and the servo motor speed is adjustable; the tool electrode is a solid ball-head cylindrical tungsten rod electrode, the diameter of which is equal to the diameter of the steel ball, and the convex and concave matching of the spiral outer raceway surface on the screw rod; during the discharge process, the outer raceway surface of the screw rod is reversely copied to the ball head end of the solid ball-head cylindrical tungsten rod electrode, so that the working end of the electrode continues to maintain a ball head shape;

[0036] Step 6: Turn on the power of the EDM machine, connect the screw to the negative pole, and connect the solid ball-end cylindrical tungsten rod electrode to the positive pole;

[0037] Step 7: Adjust the horizontal position of the solid ball-end cylindrical tungsten rod electrode so that its vertical axis is coplanar with the horizontal axis of the screw rod;

[0038] Step 8: Adjust the horizontal position of the solid ball-end cylindrical tungsten rod electrode so that its vertical projection coincides with the thread section at the starting end of the screw rod;

[0039] Step 9, set the discharge parameters, rotate the speed of the discharge spindle, and slowly adjust the vertical position of the solid ball-end cylindrical tungsten rod electrode on the vertical transmission shaft through the servo motor, so that it slowly feeds to the thread section at the starting end of the screw rod until the solid ball-end cylindrical tungsten rod electrode and the thread track surface of the screw rod reach a reasonable discharge gap;

[0040] Step 10, setting the rotation speed of the stepper motor, the horizontal scanning speed of the solid ball-end cylindrical tungsten rod electrode matched therewith, and the spraying speed of the coolant, and performing servo control on the solid ball-end cylindrical tungsten rod electrode through the servo motor to realize the compensation of the tool electrode, so that the lead screw and the electrode are always in a suitable discharge gap;

[0041] Step 11: With the uniform rotation of the screw and the horizontal uniform movement of the tool electrode, the solid ball-end cylindrical tungsten rod electrode performs electric spark ablation on the outer guide surface of the entire screw, and randomly superimposed and disorderly arranged micro-pits are generated on the outer guide surface of the screw, thereby forming a capillary lubrication channel.

[0042] If the superposition ratio of the micro-pits is not high, repeat steps 7-11, perform reciprocating scanning and ablation on the outer raceway surface of the screw rod twice or more, and finally form a capillary lubrication channel.

[0043] By adjusting the speed of the servo motor and / or the stepper motor, the shape and size of the micro-pits can be adjusted. Micro-pits are the most common type of texture morphology. The use of micro-pits arranged in a certain regular pattern can significantly improve lubrication conditions, store the function of detached abrasive particles, and reduce the contact area, solving problems such as oil shortage. In addition to this, the present embodiment also forms a capillary lubrication channel by superimposing and connecting the micro-pits, generating a capillary effect on the lubricating oil, and the lubricating oil can infiltrate, crawl, and store in the capillary lubrication channel, further improving and enhancing the lubrication performance.

[0044] In another preferred embodiment, the ball screw further includes an oil supply cleaner 5 fixedly mounted at both ends of the nut 2. The oil supply cleaner specifically includes

[0045] The disk body 51 has a central circular hole 511 with an inner diameter larger than the outer diameter of the screw rod 1, and a plurality of axial through holes 512 are evenly arranged on the end surface. A plurality of axial screw holes 21 are arranged on one end or both end surfaces of the nut 2 corresponding to the plurality of axial through holes 512; a fastening screw passes through the axial through hole 512 and is screwed with the axial screw hole 21 to fix the oil supply cleaner 5 on the nut 2; two stepped holes 513 with a smaller inner hole and a larger outer hole are relatively arranged along the radial direction of the disk body 51, and the outer section of the larger hole of the stepped hole 513 is a threaded section, and the axes of the two stepped holes 513 are at a distance of half a pitch of the screw rod 1, wherein one of the stepped holes 513 is an oil filling hole, and the other stepped hole 513 is a cleaning hole;

[0046] An oil supply head 52, which is in the shape of a stepped truncated cone as a whole, including a large truncated cone that is clearance matched with the large hole of the stepped hole 513 and a small truncated cone that is clearance matched with the small hole of the stepped hole 513, and a central oil passage 521 is axially provided at the center;

[0047] 1 cleaning head 53, the rest of which is the same structure as the oil supply head 52, except that it does not have the central oil passage 521;

[0048] Two sealing screws 54 are screwed to the threaded sections of the two stepped holes 513 respectively;

[0049] The two springs 55 have one end in contact with the oil supply head 52 or the cleaning head 53 and the other end in contact with the sealing screw 54 .

[0050] In another preferred embodiment, the small round cones of the oil supply head 52 and the cleaning head 53 extend out of the step hole 513 of the disc body 51 and abut against the outer raceway surface 11 of the screw rod 1;

[0051] In another preferred embodiment, the free ends of the small cones of the oil supply head 52 and the cleaning head 53 are hemispherical, and the diameters thereof are equal to the diameters of the steel balls.

[0052] In another preferred embodiment, the cleaning head is located at the lower part of the tray body, and the oil supply head is located at the upper part of the tray body.

[0053] The oil supply device and the cleaning device of the present embodiment are combined into one to form an oil supply cleaner 5, which is installed separately from the nut. The traditional nut with automatic oil supply function that is difficult to process is transformed into a kit composed of several parts with simple structure and convenient connection, which reduces the difficulty of integrated design and processing of the nut and improves the strength and load-bearing capacity of the nut.

[0054] The working end of the cleaning head is a hemispherical head. When working, it needs to be close to the outer raceway surface of the screw. The pressure can be adjusted by the sealing screw to clean the screw during its rotation. When replacing the cleaning head, remove the sealing screw, take the cleaning head out of the downward cleaning hole and replace it with a new cleaning head. Impurities will automatically fall out of the cleaning hole.

[0055] The working end of the oil supply head is also a hemispherical head. When working, it needs to be close to the outer raceway surface of the screw. The pressure can be adjusted by the sealing screw, and the screw can be lubricated during its rotation. Unscrew the sealing screw, inject the lubricating oil, and the lubricating oil will seep through the central oil channel and lubricate the outer raceway surface of the screw through the oil supply head. The capillary lubrication channel formed by the superposition and connection of micro-pits can fully capture and store the lubricating oil, and can evenly lubricate the contacting steel balls by itself. The oiled steel balls can lubricate the inner guide surface of the nut by themselves to form a better lubrication pair, which can reduce the contact area between the screw and the steel balls. After storing the lubricating oil, a micro-oil pool is formed, which forms a dynamic pressure lubrication effect during the high-speed reciprocating motion of the screw pair, further reducing friction and frictional heat, reducing wear and noise, making the steel balls move more smoothly, and using the least amount of lubricating oil to achieve a better lubrication effect, reducing the waste of lubricating oil and reducing the frequency of adding lubricating oil. The replacement method is the same as that of the cleaning head.

[0056] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

[0057] The matters not described in detail in the present invention are the prior art or common knowledge in the field.

Claims

1. A method for performing an electric spark roughening treatment on a ball screw raceway surface, the ball screw comprising a ball screw (1), a nut (2) with an integrated reverser, and a steel ball, characterized in that: The following steps are included: Step 1: Perform ultrasonic cleaning on the ball screw after fine processing for more than two times to remove surface oil and other debris, and dry it naturally in the air after cleaning; Step 2: Install the cleaned and dried screw rod horizontally on the EDM machine through the top and the clamp to ensure that the spatial posture of the screw rod's rotation axis is horizontal; Step 3: Connect the clamp to the high-precision stepper motor to drive the screw to rotate at a constant speed; Step 4: Check and adjust the rotation accuracy of the screw rod to within the set runout error, and then pause the rotation of the stepper motor; Step 5, clamping the tool electrode on the rotating discharge spindle driven by the servo motor of the EDM machine, the spatial posture of the spindle axis is vertical, and the servo motor speed is adjustable; the tool electrode is a solid ball-head cylindrical tungsten rod electrode, the diameter of which is equal to the diameter of the steel ball, and the convex and concave matching of the spiral outer raceway surface on the screw rod; during the discharge process, the outer raceway surface of the screw rod is reversely copied to the ball head end of the solid ball-head cylindrical tungsten rod electrode, so that the working end of the electrode continues to maintain a ball head shape; Step 6: Turn on the power of the EDM machine, connect the screw to the negative pole, and connect the solid ball-end cylindrical tungsten rod electrode to the positive pole; Step 7: Adjust the horizontal position of the solid ball-end cylindrical tungsten rod electrode so that its vertical axis is coplanar with the horizontal axis of the screw rod; Step 8: Adjust the horizontal position of the solid ball-end cylindrical tungsten rod electrode so that its vertical projection coincides with the thread section at the starting end of the screw rod; Step 9, set the discharge parameters, rotate the speed of the discharge spindle, and slowly adjust the vertical position of the solid ball-end cylindrical tungsten rod electrode on the vertical transmission shaft through the servo motor, so that it slowly feeds to the thread section at the starting end of the screw rod until the solid ball-end cylindrical tungsten rod electrode and the thread raceway surface of the screw rod reach a reasonable discharge gap; Step 10, setting the rotation speed of the stepper motor, the horizontal scanning speed of the solid ball-end cylindrical tungsten rod electrode matched therewith, and the spraying speed of the coolant, and performing servo control on the solid ball-end cylindrical tungsten rod electrode through the servo motor to realize the compensation of the tool electrode, so that the lead screw and the electrode are always in a suitable discharge gap; Step 11: With the uniform rotation of the screw and the horizontal uniform movement of the tool electrode, the solid ball-end cylindrical tungsten rod electrode performs an electrospark ablation treatment on the outer guide surface of the entire screw, and randomly superimposed and disorderly arranged micro-pits are generated on the outer guide surface of the screw, thereby forming a capillary lubrication channel; The ball screw further comprises an oil supply cleaner (5) fixedly mounted at one end or both ends of the nut (2), the oil supply cleaner comprising A disc body (51), wherein the inner diameter of the central circular hole (511) of the disc body (51) is larger than the outer diameter of the screw rod (1), and a plurality of axial through holes (512) are evenly arranged on the end surface; a plurality of axial screw holes (21) are arranged on one end or both end surfaces of the nut (2) corresponding to the plurality of axial through holes (512); a fastening screw passes through the axial through hole (512) and is screwed with the axial screw hole (21) to fix the oil supply cleaner (5) on the nut (2); two stepped holes (513) with a smaller inner hole and a larger outer hole are arranged opposite to each other along the radial direction of the disc body (51); the outer section of the larger hole of the stepped hole (513) is a threaded section; the axes of the two stepped holes (513) are spaced half the pitch of the screw rod (1); one of the stepped holes (513) is an oil filling hole, and the other stepped hole (513) is a cleaning hole; An oil supply head (52) is in the shape of a stepped truncated cone as a whole, comprising a large truncated cone that is clearance-matched with the large hole of the stepped hole (513) and a small truncated cone that is clearance-matched with the small hole of the stepped hole (513), and a central oil passage (521) is provided in the center along the axial direction; 1 cleaning head (53), the rest of which is the same structure as the oil supply head (52), except that it does not have a central oil passage (521); Two sealing screws (54) are screwed to the threaded sections of the two stepped holes (513) respectively; Two springs (55) have one end abutting against the oil supply head (52) or the cleaning head (53) and the other end abutting against the sealing screw (54).

2. The method for performing electric spark roughening treatment on the ball screw raceway surface according to claim 1, characterized in that: Repeat steps 7-11 to perform reciprocating scanning ablation on the outer raceway surface of the screw rod twice or more.

3. The method for performing electric spark roughening treatment on the ball screw raceway surface according to claim 1, characterized in that: The small round cones of the oil supply head (52) and the cleaning head (53) extend out of the step hole (513) of the disc body (51) and abut against the outer raceway surface (11) of the screw rod (1).

4. The method for performing electric spark roughening treatment on the ball screw raceway surface according to claim 1, characterized in that: The free ends of the small frustums of the oil supply head (52) and the cleaning head (53) are hemispherical, and the diameters thereof are equal to the diameters of the steel balls.

5. The method for performing electric spark roughening treatment on the ball screw raceway surface according to claim 1, characterized in that: The oil supply head (52) is located at the upper part of the disc body, and the cleaning head (53) is located at the lower part of the disc body.

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