Ultra-precision EDM motion table

Abstract

The present invention discloses a motion table for ultra-precision electro-discharge machining, comprising: a support module, which comprises a horizontal base and a gantry support arranged horizontally; an X-axis motion module, which comprises an X-axis base and an X-axis slide assembly that reciprocates along the X-axis direction; a Y-axis motion module, which comprises a Y-axis base and a Y-axis slide assembly that reciprocates along the Y-axis direction, and a working liquid tank is provided on the Y-axis slide assembly; a Z-axis motion module, which comprises a Z-axis base and a Z-axis slide assembly that reciprocates along the Z-axis direction, and an electro-discharge head that extends into the working liquid tank is provided on the Z-axis slide assembly; wherein a pair of X-axis air-floating guide rails are provided on the X-axis base, and a pair of X-axis air-floating block groups that are adapted to the pair of X-axis air-floating guide rails are provided on the X-axis slide assembly. The present invention improves the machining accuracy, system rigidity and stability of the motion table for electro-discharge machining, so that the electro-discharge machining process can be applied to ultra-precision machining of high-performance materials.

Description

Technical Field

[0001] The present invention relates to the field of electric spark machining equipment, and more particularly to a motion table for ultra-precision electric spark machining. Background Art

[0002] Electrospark machining is a process that uses electrical energy and thermal energy to process the workpiece. The difference between electrospark machining and traditional cutting machining is that during electrospark machining, the electrode of the electrospark tool does not contact the workpiece to be machined. Instead, pulsed spark discharges are continuously generated between the electrospark tool motor and the workpiece to be machined, and the local and instantaneous high temperature generated during the discharge is used to gradually erode the metal material. The existing motion platforms for electrospark machining are mostly supported by linear rails, driven by servo motors and lead screws, and their overall machining accuracy and support capabilities are limited. With the development of industrial production and the advancement of science and technology, new high-performance materials with high melting point, high hardness, high strength, high brittleness, high viscosity and high purity are constantly emerging. These high-performance new materials have high machining accuracy requirements. Among them, in superhard materials In the cutting process, such as the cutting process of cemented carbide, hardened steel and polycrystalline diamond, the workpiece of superhard material has a large mass, and the rigidity and stability of the processing motion platform are also required to be high. Most of the existing motion platforms for electrospark machining adopt CNC machine tools. For example, the invention patent with publication number CN116786919A_ discloses an electrospark machining machine tool, and its mounting position is provided with two guide rails. The driving component of the same mounting position is slidably installed on the two guide rails. The driving component includes a motor and a lead screw nut pair connected to the motor shaft, and the lead screw nut pair is a ball screw device. The disclosed electrospark machining machine tool adopts linear rail support, servo motor and lead screw drive. Its overall processing accuracy and rigidity are difficult to be applied to the ultra-performance material processing technology with ultra-precision processing requirements. Summary of the invention

[0003] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0004] Another object of the present invention is to provide a moving table for ultra-precision electrospark machining, which combines air floating support, slider support, and small hole throttling air film support, thereby improving the machining accuracy, rigidity and stability of the moving table for electrospark machining, so that the electrospark machining technology can be applied to the ultra-precision machining of new materials with ultra-performance.

[0005] Another object of the present invention is to provide a motion table for ultra-precision EDM machining, which has a plurality of working fluid tanks on a horizontal base, and a plurality of EDM heads driven by a Z-axis motion module on the crossbeam of a gantry bracket, thereby realizing simultaneous machining of the same process in EDM operation and sequential machining of different processes, and improving the efficiency of ultra-precision EDM operation.

[0006] In order to achieve these purposes and other advantages according to the present invention, there is provided a motion table for ultra-precision electrospark machining, comprising:

[0007] A support module, the support module comprises a horizontal base arranged horizontally and a gantry support arranged at the end of the horizontal base;

[0008] An X-axis motion module comprises an X-axis base arranged on the horizontal base, an X-axis slide assembly mounted outside the X-axis base, and an X-axis linear drive assembly driving the X-axis slide assembly to reciprocate along the X-axis direction;

[0009] A Y-axis motion module, comprising a Y-axis base arranged on the X-axis slide assembly, a Y-axis slide assembly mounted outside the Y-axis base, and a Y-axis linear drive assembly driving the Y-axis slide assembly to reciprocate along the Y-axis direction, wherein a working fluid tank is provided on the Y-axis slide assembly;

[0010] A Z-axis motion module comprises a Z-axis base arranged on the crossbeam of the gantry bracket, a Z-axis slide assembly mounted outside the Z-axis base, a Z-axis linear drive assembly driving the Z-axis slide assembly to reciprocate along the Z-axis direction, and a pair of cylinder assemblies balancing the Z-axis load gravity, an air-floating turntable is hung on the inverted side of the Z-axis slide assembly, and an electric spark head extending into the working fluid tank is arranged on the rotating table surface of the air-floating turntable;

[0011] Among them, a pair of X-axis air-floating guide rails are provided on the X-axis base along the X-axis direction, and a pair of X-axis air-floating block groups adapted to the pair of X-axis air-floating guide rails are provided on the X-axis slide assembly, and any X-axis air-floating block group includes a first air-floating block arranged opposite to the top of the X-axis air-floating guide rail on the side and a second air-floating block arranged opposite to the outer side of the X-axis air-floating guide rail on the side.

[0012] Preferably, a pair of Y-axis air flotation guide rails are provided on the Y-axis base along the Y-axis direction, a pair of Y-axis air flotation blocks facing the outside of the pair of Y-axis air flotation guide rails and a small hole throttling unit arranged at the bottom of the Y-axis slide assembly are provided on the Y-axis slide assembly, the Y-axis air flotation block is provided with an air inlet hole connected to the air source and a plurality of throttling air outlet holes, the air outlet direction of any throttling air outlet hole is toward the outer side surface of the Y-axis air flotation guide rail on that side, the small hole throttling unit is connected to the air source, and its air outlet direction is toward the top of the Y-axis air flotation guide rail on that side.

[0013] Preferably, the X-axis slide assembly, the Y-axis slide assembly and the Z-axis slide assembly each include:

[0014] A mounting base plate, on which is provided a pair of anti-collision blocks for limiting the travel range of the mounting base plate;

[0015] A pair of preload plates, which are vertically arranged downward on both sides of the mounting base plate, and a permanent magnet is arranged on any preload plate;

[0016] A pair of baffles are arranged in parallel on the outer sides of a pair of pre-loading plates, wherein a dust-free drag chain is arranged between the pre-loading plate and the baffle on one side;

[0017] A pair of extension plates, which are respectively arranged on both sides of the mounting base plate, and the extension plates are connected to the preload plate and the baffle plate on the side;

[0018] Among them, the preload plate of the X-axis slide assembly is arranged along the X-axis direction, and the preload plate of the Y-axis slide assembly is arranged along the Y-axis direction; a pair of preload bars that are attracted and connected to a pair of preload plates extend from the bottom of the X-axis base and the Y-axis base; and a limit block that cooperates with the anti-collision block is provided on the X-axis base and the Y-axis base.

[0019] Preferably, the X-axis linear drive assembly, the Y-axis linear drive assembly and the Z-axis linear drive assembly all include a linear drive motor, a grating scale and a reading head cooperating with the grating scale, wherein the linear drive motor of the X-axis linear drive assembly has a stator arranged on the X-axis base, and a mover arranged on the bottom of the mounting base plate of the X-axis slide assembly; the grating scale and the reading head of the X-axis linear drive assembly are respectively arranged on the bottom of the mounting plate of the X-axis base and the X-axis slide assembly; the linear drive motor of the Y-axis linear drive assembly has a stator arranged on the Y-axis base, and a mover arranged on the bottom of the mounting base plate of the Y-axis slide assembly; the grating scale and the reading head of the Y-axis linear drive assembly are respectively arranged on the bottom of the mounting plate of the Y-axis slide assembly; the Z-axis linear drive motor has a stator arranged on the Z-axis base, and a mover arranged on the bottom of the mounting base plate of the Z-axis slide assembly, and the grating scale and the reading head of the Z-axis linear drive assembly are respectively arranged on the bottom of the mounting plate of the Z-axis base and the Z-axis slide assembly.

[0020] Preferably, both sides of the X-axis slide assembly, the Y-axis slide assembly and the Z-axis slide assembly are provided with an accordion shield assembly parallel to the movement direction of the slide assembly of the motion module, and the accordion shield assembly includes:

[0021] The accordion shield is arranged on both sides of the slide assembly of the module, and the telescopic direction of the accordion shield is consistent with the movement direction of the slide assembly of the module;

[0022] an end plate disposed at a free end of the accordion shield;

[0023] a pair of shield plates, which are arranged at the bottom of the accordion shield and are respectively connected to a pair of preload bars;

[0024] A pair of L-shaped baffles, the horizontal plates of which are arranged on a pair of shield plates, and the vertical plates respectively abut against the edges of both sides of the accordion shield.

[0025] Preferably, any cylinder assembly comprises:

[0026] A cylinder fixing seat, which is arranged on the side of the Z-axis slide assembly and is integrally arranged with the Z-axis base;

[0027] A cylinder body, comprising a cylinder connected at the bottom to the Z-axis base and a piston rod disposed in the cylinder, the piston rod passing through the cylinder fixing seat;

[0028] An electromagnetic locker is located between the cylinder and the cylinder fixing seat, and the electromagnetic locker is sleeved on the piston rod to lock the piston rod when power is off;

[0029] A cylinder adapter, one end of which is connected to the movable end of the piston rod, and the other end of which is connected to the Z-axis slide assembly, so as to balance the Z-axis slide assembly and the load gravity, and at the same time drive the Z-axis slide assembly to reciprocate along the Z-axis direction;

[0030] The Z-axis dust-free drag chain is arranged on one side of the Z-axis slide assembly.

[0031] Preferably, the bottom of the working fluid tank is set on the Y-axis slide assembly by screws, and a sealing rubber plug is provided on the top of the screw hole for installing the screw. A workpiece fixing clamp is provided in the working fluid tank and a drain pipe is provided at the bottom. A T-shaped slot is provided on the horizontal base, and the size of the T-shaped slot is sufficient for the space required for the drain pipe to move with the X-axis slide assembly and the Y-axis slide assembly.

[0032] Preferably, a plurality of X-axis motion modules are arranged on the horizontal base, a number of Z-axis motion modules no greater than the number of the X-axis motion modules is provided on the crossbeam of the gantry support, the Z-axis motion module is arranged on the crossbeam of the gantry support through an X0-axis motion module, and the X0-axis motion module includes:

[0033] An X0-axis base is arranged on the crossbeam of the gantry bracket or is integrally arranged with the crossbeam of the gantry bracket, and a pair of X0-axis linear guide rails are arranged on the X0-axis base along the X0-axis direction, and the X0-axis is arranged parallel to the X-axis;

[0034] An X0-axis slide assembly, which is connected to the X0-axis linear guide rail through a slider, the X0-axis slide assembly includes a plurality of X0-axis load plates, an X0-axis adapter plate is provided between adjacent X0-axis load plates, and a Z-axis motion module is provided on the X0-axis load plate;

[0035] X0-axis linear drive motor, whose mover is arranged on the X0-axis slide assembly and whose stator is arranged on the X0-axis base;

[0036] An X0 position feedback component, comprising an X0 axis reading head arranged on an X0 axis slide assembly and an X0 axis grating ruler used in conjunction with the X0 axis reading head, wherein the X0 grating ruler is arranged on the X0 axis base;

[0037] The X0-axis dust-free drag chain is installed above the X0-axis base through a drag chain mounting plate.

[0038] Preferably, X0-axis accordion shields arranged along the X direction are provided on both sides of the X0-axis slide assembly, and X0-axis end plates are provided at the ends of the X0-axis accordion shields.

[0039] Preferably, when multiple X-axis motion modules are provided, a supporting column is provided in the middle of the gantry bracket.

[0040] The present invention has at least the following beneficial effects:

[0041] First, the ultra-precision EDM motion table provided by the present invention adopts an XYZC four-axis motion table, and the X-axis, Y-axis and Z-axis motion modules all adopt an air-floating support structure and are directly driven by a linear drive structure. On the basis of reducing the energy consumption of the EDM motion table, the straightness of the X-axis, Y-axis and Z-axis of the EDM motion table can be guaranteed to be within 0.5μm. The X-axis, Y-axis and Z-axis adopt a linear grating feedback structure to ensure that the positioning accuracy of the X-axis, Y-axis and Z-axis is within 0.3μm, which fundamentally improves the machining precision of the EDM motion table, so that the EDM process can be applied to the processing and production of ultra-performance materials with ultra-precision processing requirements. The C-axis is the rotating axis of the air-floating turntable, and the C-axis motion module adopts an air-floating support structure, is directly driven by a torque motor, and has a circular grating position feedback structure, which ensures the machining roundness of slender holes and the straightness of the machining hole axis in the EDM process;

[0042] Secondly, the X-axis motion module of the ultra-precision EDM motion table provided by the present invention adopts an air floating block structure in two directions to improve the rigidity and stability of the X-axis motion module, and the Y-axis motion module combines the air floating block structure and the small hole throttling structure to improve the rigidity and stability of the Y-axis motion module, thereby overcoming the defects of the existing EDM motion table in terms of insufficient rigidity and stability;

[0043] Thirdly, the Z-axis motion module of the ultra-precision EDM motion table provided by the present invention adopts a linear motor to drive the reciprocating motion of the Z-axis slide assembly, and uses a cylinder to balance the load weight, thereby improving the Z-axis motion accuracy. In addition, the Z-axis motion module has a brake function to prevent the Z-axis motion module from freely falling due to gravity when the power is suddenly cut off, causing danger;

[0044] Fourthly, the bracket module of the ultra-precision EDM motion table provided by the present invention is made of granite, which overcomes the defects of the complex manufacturing process and high cost of the forging bed structure of the existing EDM machine tool, and fundamentally solves the problem of complex casting process and high cost of the EDM motion table. The high rigidity and internal stress-free characteristics of the granite material further ensure the ultra-precision and high stability of the EDM motion table;

[0045] Fifth, the working liquid tank of the ultra-precision EDM motion table provided by the present invention is made of granite, and the flatness of its fixed mounting surface and workpiece mounting surface can be processed to within 3 μm, ensuring the installation accuracy of the working liquid tank and the workpiece clamping;

[0046] Sixth, the ultra-precision EDM motion table provided by the present invention can be equipped with multiple X-axis motion modules, Y-axis motion modules and working fluid tanks, and with multiple Z-axis motion components installed on the X0 axis, multiple groups of EDM operations can simultaneously perform the same process steps, and can also perform continuous operations of different processes, thus realizing the assembly line processing mode of EDM operations and improving the efficiency of EDM operations;

[0047] Seventh, the ultra-precision EDM moving table provided by the present invention applies the air-floating turntable structure to the EDM process for the first time, so that the EDM head can be processed downward during high-precision rotation, thereby improving the roundness of slender holes and the straightness of the axis of the processed holes, and further ensuring the precision of EDM using the moving table described in the present invention.

[0048] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic structural diagram of a motion table for ultra-precision electrospark machining in one technical solution of the present invention;

[0050] Figure 2 It is a rear schematic diagram of the ultra-precision electrospark machining motion table in another technical solution of the present invention;

[0051] Figure 3 It is a structural schematic diagram of the X-axis motion module in another technical solution of the present invention;

[0052] Figure 4 It is a first side schematic diagram of the X-axis motion module in another technical solution of the present invention;

[0053] Figure 5 It is a second side view schematic diagram of the X-axis motion module in another technical solution of the present invention;

[0054] Figure 6 It is a structural schematic diagram of the X-axis slide assembly in another technical solution of the present invention;

[0055] Figure 7 It is a structural schematic diagram of the working liquid tank described in another technical solution of the present invention;

[0056] Figure 8 It is a structural schematic diagram of the Z-axis motion module in another technical solution of the present invention;

[0057] Fig. 9 This is a schematic diagram of the rear of the Z-axis motion module in another technical solution of the present invention;

[0058] Fig.10 It is a schematic structural diagram of the ultra-precision electrospark machining moving table in multi-station operation in another technical solution of the present invention;

[0059] Fig.11 It is a structural schematic diagram of the X0-axis motion module in another technical solution of the present invention;

[0060] Fig.12 This is a schematic diagram of the support module structure when the moving table for ultra-precision EDM is operating in multiple positions in another technical solution of the present invention. DETAILED DESCRIPTION

[0061] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0062] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0063] like Figures 1 to 12 As shown, the present invention provides a motion table for ultra-precision electrospark machining, comprising:

[0064] A support module, comprising a horizontal base 1 arranged horizontally and a gantry support 9 arranged at an end of the horizontal base;

[0065] An X-axis motion module 2 includes an X-axis base 11 disposed on the horizontal base 1, an X-axis slide assembly 12 mounted outside the X-axis base 11, and an X-axis linear drive assembly driving the X-axis slide assembly 12 to reciprocate along the X-axis direction;

[0066] The Y-axis motion module 3 includes a Y-axis base arranged on the X-axis slide assembly 12, a Y-axis slide assembly mounted outside the Y-axis base, and a Y-axis linear drive assembly driving the Y-axis slide assembly to reciprocate along the Y-axis direction, and a working fluid tank 4 is provided on the Y-axis slide assembly;

[0067] The Z-axis motion module 7 comprises a Z-axis base arranged on the crossbeam of the gantry bracket, a Z-axis slide assembly mounted on the outside of the Z-axis base, a Z-axis linear drive assembly driving the Z-axis slide assembly to reciprocate along the Z-axis direction, and a pair of cylinder assemblies balancing the gravity of the Z-axis load, an air-floating turntable 6 is hung on the inverted side of the Z-axis slide assembly, and an electric spark head 5 extending into the working liquid tank 4 is arranged on the rotating table surface of the air-floating turntable 6; wherein, a pair of X-axis air-floating guide rails are arranged on the X-axis base 11 along the X-axis direction, and a pair of X-axis air-floating block groups adapted to the pair of X-axis air-floating guide rails are arranged on the X-axis slide assembly 12, and any X-axis air-floating block group comprises a first air-floating block 1282 arranged opposite to the top of the X-axis air-floating guide rail on the side and a second air-floating block 1281 arranged opposite to the outer side of the X-axis air-floating guide rail on the side.

[0068] In the above technical scheme, the ultra-precision EDM moving table includes a support module, an X-axis moving module, a Y-axis moving module and a Z-axis moving module, wherein the support module is made of granite material, and includes a horizontal base 1 and a gantry 9 arranged on the ground, the gantry 9 includes a crossbeam of the gantry support arranged away from the horizontal base 1 and vertical support columns arranged on both sides of the crossbeam of the gantry support, the vertical support columns connect the crossbeam of the gantry support and the horizontal base, and the support module made of granite material fundamentally solves the problems of complex forging process and high production cost of the moving table for EDM, and the support module made of granite material has the characteristics of high rigidity and no internal stress, which ensures the high precision and high stability of the moving table for EDM.

[0069] In the above technical solution, the X-axis motion module is used to drive the working liquid tank 4 for the electric spark operation to reciprocate along the X-axis direction. The X-axis motion module includes an X-axis base arranged on a horizontal base and an X-axis slide assembly that reciprocates along the X-axis direction relative to the X-axis. The X-axis base 11 is made of granite material. The high-rigidity granite X-axis base ensures the stability of the X-axis motion module, thereby ensuring the high-precision controllability of the X-axis motion module. The X-axis slide assembly 12 is mounted on the X-axis On the base 11, the X-axis base 11 is configured to be U-shaped with an open top, and two vertical ends of the U-shaped X-axis base 11 are provided with air-floating guide rails arranged along the X-axis direction, and the X-axis slide assembly 12 is configured to be U-shaped with an open top downward, and the U-shaped X-axis slide assembly 12 is mounted on the outside of the X-axis base 11 (the space between a pair of air-floating guide rails is the inner side of the X-axis base 11, and the opposite side is the outer side of the X-axis base 11), that is, the U-shaped opening width of the X-axis slide assembly 12 is greater than the U-shaped opening width of the X-axis base 11. The X-axis slide assembly 12 and the X-axis base 11 adopt a non-contact connection mode, which ensures that the straightness of the X-axis slide assembly 12 can be controlled within 0.5μm. The X-axis slide assembly is provided with air-floating blocks at the top and outer side of the air-floating guide rail, wherein the air-floating block arranged opposite to the top of the X-axis air-floating guide rail on that side is the first air-floating block 1282, and the air-floating block arranged opposite to the outer side of the X-axis air-floating guide rail on that side is the second air-floating block 1281. The first air-floating block 1282 and the second air-floating block 1281 form a double air-floating support structure, which improves the rigidity and stability of the X-axis motion module. The X-axis sliding assembly 12 is driven to reciprocate along the X-axis direction by the X-axis linear drive assembly, and positioning information is fed back by the linear grating system, so that the positioning accuracy of the X-axis motion module can be controlled within 0.3μm, which greatly improves the control precision of the EDM process, so that the EDM process can be applied to processing scenarios with high precision processing requirements, such as processing scenarios of high-performance new materials, and broadens the application scenarios of the EDM process.

[0070] In the above technical solution, the Y-axis motion module is used to control the working liquid tank 4 to reciprocate along the Y-axis direction. The Y-axis motion module includes a Y-axis base arranged on the X-axis slide assembly and a Y-axis slide assembly that reciprocates along the Y-axis direction relative to the Y-axis base. The specific connection structure of the Y-axis base and the Y-axis slide assembly is the prior art, see the utility model patent with announcement number CN214591001U and name Large Load Precision Air-floating Linear Stage, which will not be elaborated in detail in this application.

[0071] In the above technical scheme, the Z-axis motion module is used to control the electric spark head 5 to reciprocate along the Z-axis direction. The Z-axis motion module includes a Z-axis base arranged on the crossbeam of the gantry bracket and a Z-axis slide assembly that reciprocates along the Z-axis direction relative to the Z-axis base. The Z-axis slide assembly and the Z-axis base adopt an air-floating support structure to realize a non-contact connection mode between the Z-axis slide assembly and the Z-axis base. For its specific structure, please refer to the utility model patent with announcement number CN214583337U and name "Side-mounted vertical motion air-floating linear table".

[0072] In the above technical scheme, an air-floating turntable 6 is hung inverted on the Z-axis slide assembly, and an electric spark head 5 extending into the working liquid tank 4 is provided on the rotating table surface of the air-floating turntable 6. The electric spark head rotates with the rotation of the air-floating turntable 6. The figure mark 8 in the accompanying drawings is a liquid flushing pipe head for electrospark machining, which is arranged on the Z-axis slide assembly. The specific structure of the air-floating turntable 6 is detailed in the high-precision air-floating turntable structure disclosed in the utility model with announcement number CN214578349U and name "A high-precision air-floating turntable", which will not be elaborated in this application.

[0073] In the above technical scheme, the ultra-precision EDM motion table adopts an XYZ three-axis motion table, and the X-axis, Y-axis and Z-axis motion modules all adopt an air-floating support structure and are directly driven by a linear drive structure. On the basis of reducing the energy consumption of the EDM motion table, the straightness of the X-axis, Y-axis and Z-axis of the EDM motion table is ensured to be within 0.5μm. The X-axis, Y-axis and Z-axis adopt a linear grating feedback structure to ensure that the positioning accuracy of the X-axis, Y-axis and Z-axis is within 0.3μm, which fundamentally improves the machining precision of the EDM motion table and enables the EDM technology to be applied to the machining of ultra-performance materials.

[0074] In one of the technical solutions, a pair of Y-axis air flotation guide rails are provided on the Y-axis base along the Y-axis direction, a pair of Y-axis air flotation blocks facing the outside of the pair of Y-axis air flotation guide rails and a small hole throttling unit arranged at the bottom of the Y-axis slide assembly are provided on the Y-axis slide assembly, an air inlet hole connected to an air source and a plurality of throttling air outlet holes are provided on the Y-axis air flotation block, an air outlet direction of any throttling air outlet hole is toward the outer side surface of the Y-axis air flotation guide rail on that side, and the small hole throttling unit is connected to the air source, and its air outlet direction is toward the top of the Y-axis air flotation guide rail on that side.

[0075] In the above technical solution, the Y-axis motion module adopts a combined support structure of an air-floating support structure and a small-hole throttling air film support structure, which improves the rigidity and stability of the Y-axis motion module to support the working liquid tank 4. The Y-axis motion module air-floating block support structure is compounded with a small-hole throttling air film support structure, which cooperates with the double air-floating support structure of the X-axis motion module and the cylinder support structure of the Z-axis motion module to meet the support requirements of the motion table for electrospark machining.

[0076] In one of the technical solutions, the X-axis slide assembly 12, the Y-axis slide assembly and the Z-axis slide assembly all include:

[0077] A mounting base plate, on which is provided a pair of anti-collision blocks for limiting the travel range of the mounting base plate;

[0078] A pair of preload plates, which are vertically arranged downward on both sides of the mounting base plate, and a permanent magnet is arranged on any preload plate;

[0079] A pair of baffles are arranged in parallel on the outer sides of a pair of pre-loading plates, wherein a dust-free drag chain is arranged between the pre-loading plate and the baffle on one side;

[0080] A pair of extension plates, which are respectively arranged on both sides of the mounting base plate, and the extension plates are connected to the preload plate and the baffle plate on the side;

[0081] Among them, the preload plate of the X-axis slide assembly 12 is arranged along the X-axis direction, and the preload plate of the Y-axis slide assembly is arranged along the Y-axis direction; a pair of preload bars that are attracted and connected to a pair of preload plates extend from the bottom of the X-axis base 11 and the Y-axis base; and a limit block 116 that cooperates with the anti-collision block is provided on the X-axis base 11 and the Y-axis base.

[0082] like Figures 3 to 6 As shown, taking the structure of the X-axis slide assembly 12 as an example, in the above technical scheme, the X-axis slide assembly includes a mounting base plate 120, a pair of preload plates 121 forming a U-shaped structure with the mounting base plate 120, a plurality of hollow units 126 are provided on the mounting base plate 120 to reduce the dead weight of the X-axis slide assembly 12, and a pair of first air-floating blocks 1282 facing the top of the X-axis air-floating guide rail are provided on the mounting base plate 120 near the pair of preload plates 121, and a pair of second air-floating blocks 1281 facing the outer side of the X-axis air-floating guide rail are provided on the pair of preload plates 121. The first air-floating blocks 1282 and the second air-floating blocks 1281 form a double air-floating support structure of the X-axis motion module, thereby ensuring the rigidity and stability of the X-axis motion module.

[0083] In the above technical solution, the X-axis slide assembly also includes a pair of baffles 127 arranged parallel to a pair of preload plates 121. The preload plates 121 and the baffles 127 are connected by an extension plate 125, so that a dust-free drag chain 14 is arranged between the preload plates 121 and the baffles 127 on one side to pass through cables that provide power and signals to the X-axis linear drive assembly. The dust-free drag chain of the Y-axis slide assembly is used to pass through air pipes for ventilation of the air float block and the small hole throttling unit, as well as cables that provide power and signals to the Y-axis linear drive assembly.

[0084] In the above technical scheme, a permanent magnet 1210 is provided on the prefabricated plate 121, which is attracted and cooperated with the preload bar 111 arranged on the X-axis base 11, and the preload bar 111 is fixed to the horizontal base 1 by bolts. The double air-floating support structure, the preload plate 121 and the matching structure of the preload bar 111 jointly realize the non-contact connection structure between the X-axis base 11 and the X-axis slide assembly 12, eliminates the friction between the X-axis base 11 and the X-axis slide assembly 12, reduces the energy consumption of the linear motion of the X-axis slide assembly 12, and improves the accuracy of the linear motion of the X-axis slide assembly 12.

[0085] In the above technical solution, a pair of anti-collision blocks 124 are also provided on the X-axis slide assembly 12, which cooperate with the limit blocks 16 set on the X-axis base 11 to limit the travel range of the mounting base plate 120 along the X-axis reciprocating motion, thereby protecting the X-axis slide assembly 12 and improving the service life of the X-axis slide assembly.

[0086] like Figures 4 to 6 As shown, in one of the technical solutions, the X-axis linear drive assembly, the Y-axis linear drive assembly and the Z-axis linear drive assembly all include a linear drive motor, a grating ruler and a reading head that cooperates with the grating ruler, such as Figure 4 As shown, the linear drive motor of the X-axis linear drive assembly has a stator 115 arranged on the X-axis base 11, and a mover 122 arranged at the bottom of the mounting base plate of the X-axis slide assembly 12; the grating scale 114 and the reading head 123 of the X-axis linear drive assembly are respectively arranged at the bottom of the mounting plate 120 of the X-axis base 11 and the X-axis slide assembly 12. Figure 6 It can be seen that the reading head 123 is arranged at the bottom of the mounting plate 120 of the X-axis slide assembly 12 through the reading head mounting base 1230; the linear drive motor of the Y-axis linear drive assembly, its stator is arranged on the Y-axis base, and the mover is arranged at the bottom of the mounting base plate of the Y-axis slide assembly; the grating scale and the reading head of the Y-axis linear drive assembly are respectively arranged at the bottom of the Y-axis base and the mounting plate of the Y-axis slide assembly; the Z-axis linear drive motor, its stator is arranged on the Z-axis base, and the mover is arranged at the bottom of the mounting base plate of the Z-axis slide assembly, and the grating scale and the reading head of the Z-axis linear drive assembly are respectively arranged at the bottom of the Z-axis base and the mounting plate of the Z-axis slide assembly.

[0087] In the above technical solution, the X-axis slide assembly 12 is driven for linear motion by the X-axis linear drive assembly, and the Y-axis slide assembly is driven for linear motion by the Y-axis linear drive assembly, thereby ensuring that the straightness of the X-axis, Y-axis and Z-axis of the moving table for electrospark machining is within 0.5μm. The X-axis, Y-axis and Z-axis adopt a linear grating feedback structure, thereby ensuring that the positioning accuracy of the X-axis, Y-axis and Z-axis is within 0.3μm, fundamentally improving the machining precision of the moving table for electrospark machining, so that the electrospark machining technology can be applied to the processing of ultra-performance materials.

[0088] In one of the technical solutions, both sides of the X-axis slide assembly 12, the Y-axis slide assembly and the Z-axis slide assembly are provided with an accordion shield assembly parallel to the movement direction of the slide assembly of the motion module, and the accordion shield assembly includes:

[0089] The accordion shield is arranged on both sides of the slide assembly of the module, and the telescopic direction of the accordion shield is consistent with the movement direction of the slide assembly of the module;

[0090] an end plate disposed at a free end of the accordion shield;

[0091] a pair of shield plates, which are arranged at the bottom of the accordion shield and are respectively connected to a pair of preload bars;

[0092] A pair of L-shaped baffles, the horizontal plates of which are arranged on a pair of shield plates, and the vertical plates respectively abut against the edges of both sides of the accordion shield.

[0093] like Figures 3-5 As shown, in the above technical scheme, taking the X-axis motion module 2 as an example, accordion shield assemblies are provided on both sides of the X-axis slide assembly 12 to play a role of dust and water prevention and protect the internal structure of the X-axis motion module. The accordion shield assembly includes accordion shields 13 arranged on both sides of the X-axis slide assembly 12, a shield plate 112 arranged at the bottom of the accordion shield 13 and an end plate arranged at one end of the accordion shield 13 away from the X-axis slide assembly. The accordion shield 13, the shield plate 112 and the end plate form a waterproof and dustproof space. The shield plate 112 is connected to the prefabricated strip 111 by bolts. An L-shaped baffle 113 is provided on the shield plate 112. The horizontal plate of the L-shaped baffle 113 is arranged on a pair of shield plates, and the vertical plates respectively resist the two side edges of the accordion shield 13 to prevent the accordion shield 13 from curling during the extension and retraction process and damaging the accordion shield 13.

[0094] like Figure 8 and Fig. 9 As shown, in one of the technical solutions, any cylinder assembly includes:

[0095] A cylinder fixing seat 752, which is arranged on the side of the Z-axis slide assembly and is integrally arranged with the Z-axis base 71;

[0096] The cylinder body comprises a cylinder 751 whose bottom is connected to the Z-axis base and a piston rod 753 disposed in the cylinder 751, wherein the piston rod 753 passes through the cylinder fixing seat 752;

[0097] An electromagnetic locker 76, which is located between the cylinder 751 and the cylinder fixing seat 752, and the electromagnetic locker 76 is sleeved on the piston rod 753 to lock the piston rod 753 when the power is off;

[0098] A cylinder adapter 78, one end of which is connected to the movable end of the piston rod 753, and the other end of which is connected to the Z-axis slide assembly 73, so as to balance the Z-axis slide assembly 73 and the load gravity, and at the same time drive the Z-axis slide assembly 73 to reciprocate along the Z-axis direction;

[0099] The Z-axis dust-free drag chain 72 is provided on one side of the Z-axis slide table 73 assembly through the Z-axis dust-free drag chain mounting plate 720 .

[0100] In the above technical scheme, the Z-axis motion module provided by the present invention has made the following improvements compared with the side-mounted vertical motion air-floating linear table disclosed in the utility model patent with announcement number CN214583337U and name Side-mounted Vertical Motion Air-floating Linear Table: the cylinder fixing seat 752 is integrally arranged with the Z-axis base, and can be carried and installed as a whole with the cylinder fixing seat 752. Compared with the detachable mounting structure, the integrated mounting structure does not require positioning of the mounting holes, which meets the requirements of ultra-precision control of the motion table for electrospark machining. One end of the cylinder adapter 78 is connected to the movable end of the piston rod 753 through a floating joint 77, allowing a certain deviation between the cylinder 751 and the piston rod 753, thereby improving the smoothness of the movement of the cylinder body. An electromagnetic locker 76 is arranged between the cylinder 751 and the cylinder fixing seat 752 to prevent the Z-axis motion module from freely falling due to its own weight when the power is suddenly cut off, thereby improving the safety of the motion table for electrospark machining.

[0101] like Figure 7As shown, in one of the technical solutions, the bottom of the working liquid tank 4 is set on the Y-axis slide assembly by screws, and a sealing plug is provided on the top of the screw hole for installing the screw. A workpiece fixing clamp is provided in the working liquid tank 4, and a drainage pipe 41 is provided at the bottom. A T-shaped slot is provided on the horizontal base 1, and the size of the T-shaped slot is sufficient for the drainage pipe 41 to move with the X-axis slide assembly 12 and the Y-axis slide assembly. The working liquid tank 4 includes a bottom panel 44 and a side panel 45. The bottom panel 44 of the working liquid tank is made of granite, and a screw hole 42 is provided at the bottom thereof to facilitate the fixing of the barrel screw to the Y-axis slide assembly. After the bottom panel 44 of the working liquid tank 4 is connected to the Y-axis slide assembly, the screw hole 42 needs to be sealed with a sealing plug to prevent leakage from the bottom of the working liquid tank 4. A drainage pipe 41 extending to the horizontal base 1 is provided at the bottom of the working liquid tank 4, and the drainage pipe 41 is a bent pipe. A slot 16 for the drainage pipe to move is provided on the horizontal base 1.

[0102] like Figures 10-12 As shown, in one of the technical solutions, a plurality of X-axis motion modules 2 are arranged on the horizontal base 1, and a Z-axis motion module 7 not greater than the number of the X-axis motion modules 2 is provided on the crossbeam of the gantry support, so that multi-station simultaneous operation is realized, and the Z-axis motion module 7 is arranged on the crossbeam of the gantry support through the X0-axis motion module 15, and the X0-axis motion module 15 includes:

[0103] An X0-axis base 90 is arranged on the crossbeam of the gantry support or is integrally arranged with the crossbeam of the gantry support. A pair of X0-axis linear guide rails are arranged on the X0-axis base 90 along the X0-axis direction, and the X0-axis is arranged parallel to the X-axis;

[0104] The X0 axis slide assembly is connected to the X0 axis linear guide 153 through a slider 154. The X0 axis slide assembly includes a plurality of X0 axis load plates. Fig.11 A first X0-axis load plate 1521 and a second X0-axis load plate 1523, an X0-axis adapter plate 1522 is provided between adjacent X0-axis load plates, and a Z-axis motion module 7 is provided on the X0-axis load plate;

[0105] X0 axis linear drive motor, whose mover 1561 is arranged on the X0 axis slide assembly and stator 1562 is arranged on the X0 axis base;

[0106] An X0 position feedback component includes an X0 axis reading head 157 disposed on an X0 axis slide assembly and an X0 axis grating ruler 158 used in conjunction with the X0 axis reading head 157, wherein the X0 grating ruler 158 is disposed on the X0 axis base;

[0107] The X0 axis dust-free drag chain 1551 is installed above the X0 axis base through the drag chain mounting plate 1550.

[0108] In the above technical scheme, the present invention further provides a motion platform for EDM multi-station operation simultaneously, including a plurality of X-axis motion modules arranged on a horizontal base 1, a Y-axis motion module corresponding to the number of X-axis motion modules, and a Z-axis motion module less than the number of X-axis motion modules, after the Z-axis motion module drives the EDM head to complete the operation on the previous workpiece, move to the operation position facing the subsequent workpiece, continue to operate on the subsequent workpiece, and perform EDM operation on multiple workpieces in sequence. Further, considering that the EDM operation includes multiple processes, multiple Z-axis motion modules can also be set, and the EDM heads carried by different Z-axis motion modules perform operations of different processes in sequence, and the length of the X0 axis is appropriately extended, that is, the length of the X0 axis is greater than the length of the horizontal base 1, and the EDM heads carried by multiple Z-axis motion modules perform operations of different processes on the workpiece in sequence, forming an assembly line platform for EDM operation, and improving the processing efficiency of ultra-precision EDM operation.

[0109] In the above technical solution, multiple Z-axis motion modules are arranged on the crossbeam of the gantry bracket through the X0-axis motion module, and the X0-axis motion module includes an X0-axis base 90 and an X0-axis slide assembly that reciprocates along the X0-axis direction relative to the X0-axis base 90, and the X0-axis is arranged parallel to the X-axis, and multiple Z-axis motion modules are arranged on the X0-axis slide assembly, and the electric spark heads arranged on adjacent Z-axis motion modules correspond to the positions of the working liquid tanks arranged on adjacent Y-axis motion modules, and the X0-axis base is arranged on the crossbeam of the gantry bracket, such as Fig.12 As shown, as a preferred embodiment, the X0-axis base 90 can also directly serve as the crossbeam of the gantry bracket, and is integrally arranged with the crossbeam of the gantry bracket. The X0-axis base 90 is arranged in a U-shape, and the two ends of the U-shaped X0-axis base are provided with a pair of X0-axis linear guide rails. The X0-axis slide assembly is mounted on both sides of the X0-axis linear guide rails and reciprocates on the X0-axis linear guide rails. The X0-axis slide assembly includes a plurality of X0-axis load plates, and adjacent X0 load plates are connected by X0-axis adapter plates, such as Fig.11As shown, taking two X0-axis load plates as an example, the X0-axis slide assembly includes a first X0-axis load plate 1521, an X0-axis adapter plate 1522, and a second X0-axis load plate 1523 arranged in sequence. Adjacent X0-axis load plates are connected by the X0-axis adapter plate to reduce the difficulty of processing and facilitate the assembly of multiple Z-axis motion modules. The X0-axis load plate and the X0-axis adapter plate have different processing precision requirements. Processing the X0-axis load plate and the X0-axis adapter plate separately according to different precision requirements can reduce the production cost of the motion table for ultra-precision EDM. The X0-axis slide assembly is driven by an X0-axis linear drive motor. The mover 1561 of the X0-axis linear drive motor is arranged on the X0-axis slide assembly, and the stator 1562 is arranged on the X0-axis base. The precision control of the movement of the X0-axis slide assembly is controlled by the grating ruler and the reading head system, and its precision is high.

[0110] In one of the technical solutions, X0-axis accordion shields 151 arranged along the X direction are provided on both sides of the X0-axis slide assembly, and X0-axis end plates 150 are provided at the ends of the X0-axis accordion shields 151 to play a role in dust and water prevention.

[0111] like Fig.12 As shown, in one of the technical solutions, when multiple X-axis motion modules 2 are set, a supporting column is provided in the middle of the gantry bracket 9 to stabilize the X0-axis base 90.

[0112] The number of devices and processing scales described here are used to simplify the description of the present invention. Applications, modifications and variations of the ultra-precision EDM motion table of the present invention will be apparent to those skilled in the art.

[0113] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A motion table for ultra-precision electrospark machining, characterized in that: include: A support module, comprising a horizontal base arranged horizontally and a gantry support arranged at an end of the horizontal base; An X-axis motion module comprises an X-axis base arranged on the horizontal base, an X-axis slide assembly mounted outside the X-axis base, and an X-axis linear drive assembly driving the X-axis slide assembly to reciprocate along the X-axis direction; A Y-axis motion module, comprising a Y-axis base arranged on the X-axis slide assembly, a Y-axis slide assembly mounted outside the Y-axis base, and a Y-axis linear drive assembly driving the Y-axis slide assembly to reciprocate along the Y-axis direction, wherein a working fluid tank is provided on the Y-axis slide assembly; A Z-axis motion module, comprising a Z-axis base arranged on the crossbeam of the gantry bracket, a Z-axis slide assembly mounted outside the Z-axis base, a Z-axis linear drive assembly driving the Z-axis slide assembly to reciprocate along the Z-axis direction, and a pair of cylinder assemblies balancing the Z-axis slide assembly and the load gravity, an air-floating turntable being hung on the inverted side of the Z-axis slide assembly, and an electric spark head extending into the working fluid tank being arranged on the rotating table surface of the air-floating turntable; Wherein, a pair of X-axis air-floating guide rails are arranged on the X-axis base along the X-axis direction, and a pair of X-axis air-floating block groups adapted to the pair of X-axis air-floating guide rails are arranged on the X-axis slide assembly, and any X-axis air-floating block group includes a first air-floating block arranged opposite to the top of the X-axis air-floating guide rail on the side and a second air-floating block arranged opposite to the outer side of the X-axis air-floating guide rail on the side; A pair of Y-axis air-floating guide rails are provided on the Y-axis base along the Y-axis direction, a pair of Y-axis air-floating blocks facing the outside of the pair of Y-axis air-floating guide rails and a small hole throttling unit arranged at the bottom of the Y-axis slide assembly are provided on the Y-axis slide assembly, an air inlet hole connected to an air source and a plurality of throttling air outlet holes are provided on the Y-axis air-floating block, an air outlet direction of any throttling air outlet hole is toward the outer side surface of the Y-axis air-floating guide rail on the side, the small hole throttling unit is connected to the air source, and its air outlet direction is toward the top of the Y-axis air-floating guide rail on the side; Any cylinder assembly includes: A cylinder fixing seat, which is arranged on the side of the Z-axis slide assembly and is integrally arranged with the Z-axis base; A cylinder body, comprising a cylinder connected at the bottom to the Z-axis base and a piston rod disposed in the cylinder, the piston rod passing through the cylinder fixing seat; An electromagnetic locker is located between the cylinder and the cylinder fixing seat, and the electromagnetic locker is sleeved on the piston rod to lock the piston rod when power is off; A cylinder adapter, one end of which is connected to the movable end of the piston rod, and the other end of which is connected to the Z-axis slide assembly, so as to balance the Z-axis slide assembly and the load gravity, and at the same time drive the Z-axis slide assembly to reciprocate along the Z-axis direction; The Z-axis dust-free drag chain is arranged on one side of the Z-axis slide assembly.

2. The ultra-precision EDM motion table according to claim 1, characterized in that: The X-axis slide assembly, the Y-axis slide assembly and the Z-axis slide assembly all include: A mounting base plate, on which is provided a pair of anti-collision blocks for limiting the travel range of the mounting base plate; A pair of preload plates, which are vertically arranged downward on both sides of the mounting base plate, and a permanent magnet is arranged on any preload plate; A pair of baffles are arranged in parallel on the outer sides of a pair of pre-loading plates, wherein a dust-free drag chain is arranged between the pre-loading plate and the baffle on one side; A pair of extension plates, which are respectively arranged on both sides of the mounting base plate, and the extension plates are connected to the preload plate and the baffle plate on the side; Among them, the preload plate of the X-axis slide assembly is arranged along the X-axis direction, the preload plate of the Y-axis slide assembly is arranged along the Y-axis direction, and the preload plate of the Z-axis slide assembly is arranged along the Z-axis direction; a pair of preload bars that are attracted and connected to a pair of preload plates extend from the bottom of the X-axis base, the Y-axis base and the Z-axis base; and a limit block that cooperates with the anti-collision block is provided on the X-axis base, the Y-axis base and the Z-axis base.

3. The ultra-precision EDM motion table according to claim 2, characterized in that: The X-axis linear drive assembly, the Y-axis linear drive assembly and the Z-axis linear drive assembly all include a linear drive motor, a grating ruler and a reading head cooperating with the grating ruler, wherein the linear drive motor of the X-axis linear drive assembly has a stator arranged on the X-axis base, and a mover arranged on the bottom of the mounting base plate of the X-axis slide assembly; the grating ruler and the reading head of the X-axis linear drive assembly are respectively arranged on the bottom of the mounting plate of the X-axis base and the X-axis slide assembly; the linear drive motor of the Y-axis linear drive assembly has a stator arranged on the Y-axis base, and a mover arranged on the bottom of the mounting base plate of the Y-axis slide assembly; the grating ruler and the reading head of the Y-axis linear drive assembly are respectively arranged on the bottom of the mounting plate of the Y-axis slide assembly; the Z-axis linear drive motor has a stator arranged on the Z-axis base, and a mover arranged on the bottom of the mounting base plate of the Z-axis slide assembly, and the grating ruler and the reading head of the Z-axis linear drive assembly are respectively arranged on the bottom of the mounting plate of the Z-axis base and the Z-axis slide assembly.

4. The ultra-precision EDM motion table according to claim 3, characterized in that: Both sides of the X-axis slide assembly, the Y-axis slide assembly and the Z-axis slide assembly are provided with an accordion shield assembly parallel to the movement direction of the slide assembly of the motion module, and the accordion shield assembly includes: The accordion shield is arranged on both sides of the slide assembly of the module, and the telescopic direction of the accordion shield is consistent with the movement direction of the slide assembly of the module; an end plate disposed at a free end of the accordion shield; a pair of shield plates, which are arranged at the bottom of the accordion shield and are respectively connected to a pair of preload bars; A pair of L-shaped baffles, the horizontal plates of which are arranged on a pair of shield plates, and the vertical plates respectively abut against the two side edges of the accordion shield.

5. The ultra-precision EDM motion table according to claim 4, characterized in that: The bottom of the working liquid tank is set on the Y-axis slide assembly by screws, and a sealing plug is provided on the top of the screw hole for installing the screw. A workpiece fixing clamp is provided in the working liquid tank and a drainage pipe is provided at the bottom. A T-shaped slot is provided on the horizontal base, and the size of the T-shaped slot is sufficient for the space required for the drainage pipe to move with the X-axis slide assembly and the Y-axis slide assembly.

6. The ultra-precision EDM motion table according to claim 5, characterized in that: A plurality of X-axis motion modules are arranged on the horizontal base, and a number of Z-axis motion modules not greater than the number of the X-axis motion modules is arranged on the crossbeam of the gantry support, and the Z-axis motion module is arranged on the crossbeam of the gantry support through the X0-axis motion module, and the X0-axis motion module includes: An X0-axis base is arranged on the crossbeam of the gantry bracket or is integrally arranged with the crossbeam of the gantry bracket, and a pair of X0-axis linear guide rails are arranged on the X0-axis base along the X0-axis direction, and the X0-axis is arranged parallel to the X-axis; An X0-axis slide assembly, which is connected to the X0-axis linear guide rail through a slider, the X0-axis slide assembly includes a plurality of X0-axis load plates, an X0-axis adapter plate is provided between adjacent X0-axis load plates, and a Z-axis motion module is provided on the X0-axis load plate; X0-axis linear drive motor, whose mover is arranged on the X0-axis slide assembly and whose stator is arranged on the X0-axis base; An X0 position feedback component, comprising an X0 axis reading head arranged on an X0 axis slide assembly and an X0 axis grating ruler used in conjunction with the X0 axis reading head, wherein the X0 axis grating ruler is arranged on the X0 axis base; The X0-axis dust-free drag chain is installed above the X0-axis base through a drag chain mounting plate.

7. The ultra-precision EDM motion table according to claim 6, characterized in that: X0-axis accordion shields are arranged along the X direction on both sides of the X0-axis slide assembly, and X0-axis end plates are arranged at the ends of the X0-axis accordion shields.

8. The ultra-precision EDM motion table according to claim 6, characterized in that: When multiple X-axis motion modules are provided, a supporting column is provided in the middle of the gantry bracket.

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