Optical aspheric robot elliptical vibration polishing device and method

Abstract

The invention belongs to the technical field of optical element precision machining, and relates to an optical aspheric robot elliptical vibration polishing device and method.The device comprises an elliptical vibration polishing assembly composed of a pressure adjusting air cylinder, a motor, an electric slip ring and an ultrasonic vibration polishing unit, and a main shaft of the motor penetrates through the electric slip ring to be in key connection with the ultrasonic vibration polishing unit; the ultrasonic vibration polishing unit comprises a shell and an ultrasonic elliptical vibrator coaxially fixed in the shell; the ultrasonic elliptical vibrator comprises an ultrasonic amplitude-change pole, a sleeve and a holding clamp which are coaxially arranged in sequence, the holding clamp penetrates through the shell and extends out of the shell, and a polishing rod is clamped and fixed to the tail end of the holding clamp; the pressure adjusting air cylinder pushes the ultrasonic vibration polishing unit to make soft contact with a workpiece, meanwhile, a main shaft of the motor drives the polishing rod to rotate, and the ultrasonic elliptical vibrator drives the polishing rod to make elliptical vibration through the ultrasonic amplitude-change pole. According to the method, the machining geometric accuracy of the aspheric surface is improved, the polishing efficiency is greatly improved, and the machining period is shortened.

Description

Technical Field

[0001] The present application belongs to the technical field of optical element precision processing, and more specifically, relates to an optical aspheric robot elliptical vibration polishing device and method. Background Art

[0002] Existing optical aspheric surface processing technologies include small grinding heads, air bags, magnetorheological fluid, ion beams, etc. Small grinding heads and air bag polishing control the amount of material removal by adjusting the dwell time and pressure, but the removal efficiency of small grinding heads is low, and the air bag has high requirements on the motion accuracy of the machine tool, which makes it difficult to control. The shaping accuracy range of magnetorheological fluid and ion beam polishing is narrow, and the equipment cost is high. In order to improve the polishing efficiency, some polishing devices combined with ultrasonic vibration technology have been proposed in recent years. For example, Chinese invention patent CN112775728A discloses an ultrasonic polishing device used in conjunction with a robot. This solution mainly relies on the shear and friction generated by torsional vibration to achieve the polishing effect. It is suitable for rough polishing of workpieces, and its torsional characteristics may leave specific tracks and scratches on the surface of the workpiece. Chinese invention patent CN104476378A discloses a single-excitation ultrasonic elliptical vibration polishing device. Although the device can produce an elliptical vibration polishing trajectory, due to structural limitations, the device cannot independently and flexibly regulate the vibration in two directions, and can only be used at a fixed frequency point. The frequency modulation is limited, and due to the device structure, it can only be used for flat polishing and cannot be expanded to the field of complex curved surface polishing. Chinese invention patent CN105171537B discloses an ultrasonic vibration polishing grinding head device that can suppress the intermediate frequency error of optical components. In this technical solution, the vibration of the entire tool will inevitably aggravate the fatigue characteristics of the motor and transmission parts, seriously affecting the service life of the tool. Secondly, although the flexible hinge grinding head moves irregularly under vibration, it cannot effectively affect the intermediate frequency error left by the polishing tool under the fixed polishing trajectory, and is limited by the grinding disc structure and cannot be used for polishing complex curved surfaces. Chinese invention patent CN109571158A discloses a circular-driven ultrasonic vibration-assisted polishing tool and Chinese invention patent CN109623509A discloses a central-driven ultrasonic vibration-assisted polishing tool, both of which convert displacement vibration into spatial multi-dimensional vibration by designing a spring damping rod, a ball head push rod, etc. at the end of the ultrasonic vibration standard shank. However, adding a complex device to the ultrasonic shank will introduce additional vibration nodes and reflection points, significantly reducing the vibration transmission efficiency. And the complex structure will change the overall mass and stiffness distribution of the device, thereby affecting the resonant frequency. Such a structural design will greatly increase the difficulty of debugging and the stability of the device, and may affect the quality and efficiency of processing, so this method has not been widely used in the processing field.

[0003] In summary, how to ensure the geometric accuracy of aspheric surfaces while significantly improving polishing efficiency, shortening processing cycles, reducing production costs, and realizing mass production of optical aspheric surfaces is an urgent problem to be solved in the field of ultra-precision machining. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of the present application is to provide an optical aspheric robot elliptical vibration polishing device and method, aiming to solve the problem of improving the polishing efficiency and quality of hard, brittle and difficult-to-process materials.

[0005] To achieve the above-mentioned objectives, in a first aspect, the present application provides an optical aspheric robot elliptical vibration polishing device, comprising an elliptical vibration polishing assembly, wherein the elliptical vibration polishing assembly comprises a pressure regulating cylinder, a motor, an electric slip ring and an ultrasonic vibration polishing unit connected in series in sequence, wherein the main shaft of the motor passes through the electric slip ring and is key-connected to the ultrasonic vibration polishing unit; the ultrasonic vibration polishing unit comprises a housing and an ultrasonic elliptical vibrator coaxially fixed in the housing; the ultrasonic elliptical vibrator comprises an ultrasonic amplitude transformer, a sleeve and a clamp coaxially arranged in sequence; the clamp extends through the housing to the outside thereof, and a polishing head is clamped and fixed at its end; the pressure regulating cylinder is used to push the ultrasonic vibration polishing unit so that the polishing head achieves soft contact with the workpiece; the main shaft of the motor is used to drive the polishing head to rotate; the ultrasonic elliptical vibrator is used to drive the polishing head to perform elliptical vibration via the ultrasonic amplitude transformer.

[0006] Furthermore, the ultrasonic horn is made of aluminum alloy or titanium alloy.

[0007] Furthermore, the pressure regulating cylinder is a double-acting cylinder, on which a proportional pressure valve is provided, and the proportional pressure valve is used to adjust the cylinder thrust.

[0008] Furthermore, the cylinder push plate of the pressure regulating cylinder is connected to the output shaft of the motor.

[0009] Furthermore, the shell is a hollow cylinder, and the ultrasonic elliptical vibrator also includes a piezoelectric ceramic group and an end cover, the end cover, the piezoelectric ceramic group and the ultrasonic amplitude transformer are connected in sequence, and the end cover and the ultrasonic amplitude transformer are respectively provided with radially symmetrical stationary point mounting holes, and the shell is provided with a stationary point support threaded hole matching the stationary point mounting hole, and the stationary point mounting hole and the stationary point support threaded hole are connected by a screw.

[0010] Furthermore, the ultrasonic vibration polishing unit also includes an ultrasonic vibration controller, an ultrasonic power supply and a power amplifier group. The ultrasonic vibration controller is used to determine the resonant operating point of the ultrasonic vibration polishing unit and control the ultrasonic power supply to output an electrical signal of corresponding frequency for the power amplifier group; the power amplifier group is used to amplify the gain of the electrical signal and transmit it to the piezoelectric ceramic group, thereby driving the polishing rod to vibrate in an elliptical trajectory.

[0011] Furthermore, the robot elliptical vibration polishing device also includes an industrial robot and a polishing liquid supply module. The elliptical vibration polishing assembly is installed at the processing end of the industrial robot. The liquid outlet of the polishing liquid supply module is located above the polishing position and is used to supply polishing liquid during polishing.

[0012] According to a second aspect of the present application, a method for polishing using an optical aspheric robot elliptical vibration polishing device as described above is also disclosed, wherein the polishing is performed by traversing the surface of the workpiece according to a preset running trajectory of the polishing head, comprising: S1 adjusts the cylinder thrust of the pressure regulating cylinder to balance the cylinder thrust with the gravity of the ultrasonic vibration polishing unit; S2 continues to adjust the cylinder thrust of the pressure regulating cylinder to control the soft contact pressure between the polishing head and the workpiece; S3 controls the motor to rotate to drive the ultrasonic vibration polishing unit to rotate synchronously, and at the same time controls the ultrasonic elliptical vibrator to output a second-order longitudinal vibration signal and a fourth-order bending vibration signal with consistent resonant frequency to drive the polishing rod to perform elliptical vibration to achieve polishing of the workpiece.

[0013] Furthermore, before step S1, a fixed-point polishing method is used to obtain a removal function of the polishing head under a specific material and polishing environment; an interferometer is used to obtain surface error data of the workpiece to be polished, and the preset running trajectory of the polishing head is obtained using the removal function and surface error data of the workpiece to be polished, and the working parameters of the industrial robot and the corresponding polishing liquid flow rate are planned according to the surface error data and curvature of the workpiece.

[0014] Furthermore, when the industrial robot controls the elliptical vibration polishing assembly to traverse the optical curved surface of the workpiece along the polishing trajectory, the normal line of the polishing head coincides with the normal line of the optical curved surface of the workpiece.

[0015] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0016] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: (1) The elliptical vibration polishing assembly of the present application optimizes the design of the connection structure at the end of the amplitude change rod. The traditional cutting process is a process in which the diamond tool and the workpiece are in hard contact to remove materials. The diamond tool of the cutting device is locked at the end of the amplitude change rod by the upper fastening screw. The preload force, front angle and back angle position of the screw directly affect the elliptical vibration direction of the tool. The replacement of the tool requires re-frequency adjustment and precise position calibration. The vibration mode is greatly affected by the size of the tool. The tool is non-standard and customized, and the cost is high and the cycle is long. Polishing is a soft contact. The present application relies on a force control mechanism composed of a pressure regulating cylinder and a motor to press the polishing head against the surface of the workpiece to remove materials by friction. The polishing head is connected to the end of the amplitude change rod by a collet sleeve. The collet can adapt to polishing rods of different sizes and materials. It can also transmit the amplitude of the amplitude change rod to the polishing head, and a certain error is allowed without precise adjustment. In this way, the device can adapt to standard polishing heads of different sizes and reduce the cost of use.

[0017] (2) In this application, considering that the polishing process is a soft contact, the amplitude transformer is made of lighter aluminum alloy and titanium alloy to achieve the effect of amplitude amplification. Compared with the front cover plate of the traditional cutting device made of steel material, which provides a certain rigidity to the diamond tool during the hard-to-hard cutting process, but results in a smaller amplitude, the amplitude transformer made of aluminum alloy and titanium alloy amplifies the amplitude and is more suitable for polishing.

[0018] (3) Compared with a fixed cutting device, the present application adds a force control device and provides a polishing head (i.e., polishing rod) with rotational freedom. The additional rotation of the polishing head while vibrating can make the material removal more uniform, thereby obtaining a more stable polishing removal function and material removal amount. In addition, by adding a force control device, the contact force between the polishing head and the workpiece during the polishing process can be adjusted, thereby adjusting the processing removal amount.

[0019] (4) Compared with the traditional diamond cutting device, the processing quality and stability of the present application are greatly improved. Since the polishing head and the workpiece of the present application are in soft contact, the impact of node offset is very small, so the elliptical amplitude of the device is more stable, which is more conducive to improving the processing accuracy.

[0020] (5) The present application provides an optical aspheric elliptical ultrasonic vibration polishing method, which combines an elliptical ultrasonic vibration polishing device with a robot. It can not only realize flexible and adjustable multi-dimensional ultrasonic vibration, but also adapt to complex optical surfaces. It can further improve the polishing efficiency of optical surfaces based on hard and brittle materials, and greatly reduce the cost of polishing equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall assembly of the robot elliptical vibration polishing device provided in an embodiment of the present application; Figure 2It is a schematic diagram of the structure of the elliptical vibration polishing device provided in an embodiment of the present application; Figure 3 is a cross-sectional schematic diagram of an elliptical vibration polishing device provided in an embodiment of the present application; Figure 4 It is a schematic diagram of the driving principle of the elliptical vibration polishing device provided in an embodiment of the present application; Figure 5 It is a schematic diagram of the structure of an ultrasonic elliptical vibrator of an elliptical vibration polishing device provided in an embodiment of the present application; Figure 6 It is a schematic diagram of the structure frame of the package shell of the elliptical vibration polishing device provided in the embodiment of the present application; Figure 7 This is a vibration trajectory test diagram of the polishing head of the elliptical vibration polishing device provided in an embodiment of the present application; Figure 8 It is a schematic diagram of the vibration mode and nodes of the transducer of the elliptical vibration polishing device provided in the embodiment of the present application.

[0022] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-elliptical vibration polishing assembly; 11-ultrasonic vibration polishing unit, 111-ultrasonic vibration controller; 112-ultrasonic elliptical vibrator, 1121-end cover, 1122-longitudinal vibration piezoelectric ceramic group, 1123-bending vibration piezoelectric ceramic group, 1124-ultrasonic amplitude transformer, 1125-piezoelectric detection element, 1126-sleeve, 1127-clamp, 1128-polishing head, 1129-station support threaded hole, 1130-station mounting hole; 113-dual-channel ultrasonic power supply; 114-power amplifier group; 115-housing; 12-electric slip ring; 13-motor; 14-pressure regulating cylinder; 15-mounting flange; 16-spindle; 21-industrial robot; 22-robot control system; 3-polishing liquid supply module, 31-polishing liquid barrel, 32-peristaltic pump; 4-polishing process software system; 5-aspherical optical element to be polished. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0024] The term "and / or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " in this article indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0025] The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects. For example, a first response message and a second response message are used to distinguish different response messages rather than to describe a specific order of the response messages.

[0026] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0027] In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more than two. For example, multiple processing units refer to two or more processing units, etc.; multiple elements refer to two or more elements, etc.

[0028] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0029] The present embodiment provides an optical aspheric robot elliptical vibration polishing device, comprising an elliptical vibration polishing component 1, an industrial robot 21 and a polishing liquid supply module 3. The elliptical vibration polishing component 1 is installed at the processing end of the industrial robot 21, and the liquid outlet end of the polishing liquid supply module 3 is located directly above the polishing position for adding polishing liquid during polishing.

[0030] Specifically, Figure 1 As shown, the industrial robot 21 is installed on the base of the polishing system, and is used to carry the elliptical vibration polishing assembly 1, so that when the elliptical vibration polishing assembly 1 traverses the optical surface along the polishing track, the industrial robot moves along the polishing track under the drive of the robot controller 22, and the normal line of the polishing head in the elliptical vibration polishing assembly 1 coincides with the normal line of the optical surface. More specifically, the polishing process software system 4 is mounted on an external controller, and is mainly used to generate the polishing track. Its functions include surface error data import, removal function generation or import, resident algorithm and polishing track calculation, etc., and can output NC files that can be read by the industrial robot 21, thereby driving the industrial robot 21 to perform the polishing action.

[0031] The elliptical vibration polishing assembly 1 is installed on the end flange of the robot, and includes a pressure regulating cylinder 14, a motor 13, an electric slip ring 12 and an ultrasonic vibration polishing unit 11 connected in series in sequence. The main shaft of the motor 13 passes through the electric slip ring 12 and is key-connected with the ultrasonic vibration polishing unit 11; the ultrasonic vibration polishing unit 11 includes a housing 115 and an ultrasonic elliptical vibrator 112 coaxially fixed in the housing 115; an ultrasonic horn 1124 is coaxially arranged at the end of the ultrasonic elliptical vibrator 112, and a piezoelectric detection element 1125 is arranged on the ultrasonic horn 1124, and Its end is sequentially sleeved with a sleeve 1126 and a clamp 1127, the clamp 1127 passes through the outer shell 115 and extends to the outside thereof, and a polishing head 1128 is clamped and fixed at the end of the clamp, and the shape of the polishing head 1128 can be selected according to actual needs, such as a ball head shape, a cylinder shape, or a cylinder with a ball head shape; the pressure regulating cylinder 14 pushes the ultrasonic vibration polishing unit 11 to achieve soft contact with the workpiece, and at the same time, the main shaft of the motor 13 drives the polishing head 1128 to rotate, and the ultrasonic elliptical vibrator 112 drives the polishing head 1128 to vibrate elliptically via the ultrasonic amplitude transformer 1124.

[0032] An aspheric optical element 5 to be polished is installed on the polishing workbench, and a corresponding polishing tool control system is provided on the polishing workbench. The elliptical vibration polishing assembly 1 is connected to the polishing tool control system by an electrical circuit, so that parameters such as the polishing head rotation speed, pressure, amplitude and frequency can be regulated.

[0033] The polishing liquid supply module 3 includes a liquid storage barrel 31 placed on the side of the workbench, an infusion tube led out from the liquid storage barrel 31, a peristaltic pump 32 and a polishing liquid control system. The polishing liquid control system is used to control the output of the polishing liquid pumped out by the peristaltic pump 32, so as to realize the quantitative addition of polishing liquid during the robot polishing process.

[0034] The elliptical vibration polishing assembly 1 comprises a pressure regulating cylinder 14, a motor 13, an electric slip ring 12 and an ultrasonic vibration polishing unit 11 connected in series, and the motor 13, the pressure regulating cylinder 14 and the ultrasonic vibration polishing unit 11 constitute a polishing tool control assembly. The main shaft of the motor 13 passes through the electric slip ring 12 and is key-connected to the ultrasonic vibration polishing unit 11, the lower cable of the electric slip ring 12 is connected to the ultrasonic vibration polishing unit 11, and the upper cable is connected to the ultrasonic vibration controller and the power amplifier, etc., mainly to provide external power supply for the ultrasonic vibration polishing unit 11.

[0035] like Figure 2 and Figure 3 As shown, they are respectively a structural diagram and a cross-sectional view of the elliptical vibration polishing assembly 1 provided in this embodiment. The pressure regulating cylinder 14 is fixed on a mounting flange 15 connected to the end of the industrial robot 21, and the cylinder push plate of the pressure regulating cylinder 14 is connected to the flange mounting plate of the motor 13 through another connecting plate.

[0036] The motor 13 is selected as a spindle servo motor, which drives its spindle 16 to rotate through a coupling, and the end of the spindle 16 transmits the rotational action to the ultrasonic vibration polishing unit 11 through a key connection, so that the ultrasonic vibration polishing unit 11 rotates closely against the polishing workpiece while superimposing elliptical ultrasonic vibration; The pressure regulating cylinder 14 is a double-acting cylinder, on which a proportional pressure valve (not shown) is arranged, which is used to adjust the cylinder thrust, and then control the soft contact pressure between the polishing head 1128 and the workpiece. During operation, the cylinder thrust is first adjusted to balance the cylinder thrust with the weight of the polishing tool, and then the pressure valve is continuously adjusted to control the contact pressure between the polishing head and the workpiece.

[0037] The ultrasonic vibration polishing unit 11 includes a housing 115 and an ultrasonic elliptical vibrator 112 coaxially fixed in the housing 115; an ultrasonic horn 1124 is coaxially arranged at the end of the ultrasonic elliptical vibrator 112, and the ultrasonic horn 1124 is made of aluminum alloy or titanium alloy and can amplify the amplitude.

[0038] like Figure 4 As shown, the ultrasonic vibration polishing unit 11 also includes an ultrasonic vibration controller 111, a dual-channel ultrasonic power supply 113 (driving circuit) and a power amplifier group 114. The ultrasonic vibration controller 111 includes a main control CPU and a main power supply, a power control circuit and a current sampling detection circuit. When the ultrasonic vibration polishing unit 11 is started, the power control circuit inside the ultrasonic vibration controller 111 starts to sweep the frequency, and the current sampling detection circuit receives the current signal sent back by the piezoelectric detection element 1125 of the ultrasonic vibration polishing unit 11, and determines the resonant working point of the ultrasonic vibration polishing unit 11 by analyzing the current changes and phase differences of the two groups of piezoelectric detection elements, and controls the ultrasonic power supply to output an electrical signal of the corresponding frequency; when polishing is in progress, the main control CPU continues to analyze the returned current signal, and performs impedance matching through the function control circuit, and changes the output voltage of the power supply according to the change of the load to ensure the stability of the working frequency, so that the ultrasonic vibration polishing unit 11 produces a stable elliptical vibration trajectory to ensure the polishing quality.

[0039] The aforementioned dual-channel ultrasonic power supply 113 is used to generate two high-frequency AC signals with independently adjustable amplitude and frequency. Through its internal synchronous timing circuit, it can accurately control the phases of the two signals and transmit the AC signals to the two-way power amplifier group 114 to achieve precise control of the elliptical vibration trajectory of the polishing head.

[0040] The aforementioned power amplifier is divided into a bending vibration power amplifier and a longitudinal vibration power amplifier, which are independently controlled to amplify the high-frequency sinusoidal electrical signal from the ultrasonic power supply and transmit it to the longitudinal vibration and bending vibration piezoelectric ceramic groups respectively, driving the end polishing head to produce elliptical trajectory vibration.

[0041] like Figure 5As shown, the end of the ultrasonic transformer 1124 is sequentially sleeved with a sleeve 1126 and a clamp 1127, the clamp 1127 passes through the housing 115 and extends to the outside thereof, and a polishing head 1128 is clamped and fixed at the end of the clamp; the pressure regulating cylinder 14 pushes the ultrasonic vibration polishing unit 11 to achieve soft contact with the workpiece, and at the same time, the main shaft of the motor 13 drives the polishing head 1128 to rotate, and the ultrasonic elliptical vibrator 112 drives the polishing head 1128 to perform elliptical vibration via the ultrasonic transformer 1124.

[0042] The housing 115 is a hollow cylinder, and the ultrasonic elliptical vibrator 112 further includes a piezoelectric ceramic group and an end cap 1121. The end cap 1121, the piezoelectric ceramic group and the ultrasonic horn 1124 are connected in sequence. The end cap 1121 and the ultrasonic horn 1124 are respectively provided with radially symmetrical stationary point mounting holes 1130 for fixing the ultrasonic vibrator without affecting the working mode vibration shape of the overall polishing device.

[0043] like Figure 6 As shown, the housing 115 is provided with a stationary point support threaded hole 1129 matching the stationary point mounting hole 1130, and the stationary point mounting hole 1130 is connected to the stationary point support threaded hole 1129 by a screw rod, as shown in FIG. Figure 8 As shown, the vibration mode and node diagram of the ultrasonic elliptical vibrator 112 in the elliptical vibration polishing component 1. Through modal simulation, the elliptical vibrator (i.e., the ultrasonic vibration polishing unit 11) can achieve modal merging under the second-order longitudinal vibration and the fourth-order bending vibration, and has two overlapping standing wave nodes. Fixing the vibrator at these two standing wave nodes can effectively prevent the loosening of the fixing screws while ensuring the generation of high-frequency resonance, and improve the stability of the ultrasonic elliptical vibrator 112.

[0044] The piezoelectric ceramic group includes a longitudinal vibration piezoelectric ceramic group 1122 and a bending vibration piezoelectric ceramic group 1123. The longitudinal vibration piezoelectric ceramic group 1122 includes 2 annular piezoelectric ceramics, and the bending vibration piezoelectric ceramic group 1123 includes 8 semicircular annular piezoelectric ceramics, and each pair of two piezoelectric ceramics constitutes 4 annular piezoelectric ceramics. Adjacent piezoelectric ceramics are separated by electrode sheets, and the connection between the bending vibration piezoelectric ceramic group 1123 and the longitudinal vibration piezoelectric ceramic group 1122 shares an electrode sheet (not shown in the figure). The electrode sheet is used to transmit the electrical signals of the bending vibration power amplifier and the longitudinal vibration power amplifier to the bending vibration and longitudinal vibration piezoelectric ceramic group. The piezoelectric ceramic group converts the excitation electrical signal received by the electrode sheet into a composite vibration in the longitudinal and bending directions, thereby realizing high-frequency elliptical vibration of the polishing head, wherein the second-order longitudinal vibration and the fourth-order bending vibration have the same resonant frequency and have two overlapping standing wave nodes.

[0045] The aforementioned piezoelectric ceramic group and ultrasonic horn 1124 are both hollow open-hole structures, a countersunk hole is opened at the end cover 1121, and a thread is processed on the ultrasonic horn 1124, and bolts are used to nest and fix the end cover 1121, the piezoelectric ceramic group and the ultrasonic horn 1124. In addition, the end cover 1121 and the ultrasonic horn 1124 are both provided with stationary point mounting holes arranged symmetrically along the radial direction, which are used to stationary point fix the ultrasonic elliptical vibrator 112.

[0046] like Figure 7 As shown, the vibration trajectory of the tool tip at the clamping position of the elliptical vibration polishing component 1 is measured by a Doppler laser vibrometer, which can be fitted into an ellipse with a major axis of 4.9um and a minor axis of 1.9um. The phase difference between the two amplitudes is relatively consistent with the power excitation signal, and the vibration frequency reaches 49.735kHz, which proves the feasibility of the optical aspheric robot elliptical vibration polishing device provided in this application.

[0047] In traditional cutting processes, the impact of diamond tools during the processing process is large, which will cause the vibration node position to shift, resulting in changes in the resonant frequency. During this impact process, the diamond tool wear and the piezoelectric ceramic heats up, resulting in a shortened device life. At the same time, due to the increase in temperature, the processing trajectory deviates from the designed trajectory, and the impedance increases, the loss increases, the electromechanical conversion efficiency is reduced, and the processing quality and accuracy are further reduced. Since the polishing head and the workpiece of this application are in soft contact, the impact of node offset is very small, so the elliptical amplitude of the entire polishing device is more stable, which is more conducive to improving processing accuracy, and the processing quality and stability are also greatly improved.

[0048] In another embodiment, a method for polishing using the aforementioned optical aspheric robot elliptical vibration polishing device is disclosed, the steps of the method comprising: First, a fixed-point polishing method is used to obtain the removal function of the polishing head 1128 under a specific material and polishing environment, that is, the amount of material removed per unit time; an interferometer is used to obtain the surface error data of the workpiece to be polished, and the removal function and surface error data of the workpiece to be polished are used to obtain the running trajectory of the polishing head 1128, and according to the surface error equation, removal function and curvature of the workpiece, the motion position, speed and other working parameters of the industrial robot 21 and the corresponding polishing liquid flow rate are planned.

[0049] The four-point method is used to calibrate the workpiece to be polished at a fixed position on the workbench, and the positioning accuracy reaches the sub-millimeter level. The industrial robot's own repeated positioning accuracy can reach ±0.05mm to ensure the position accuracy between the polishing head and the polishing workpiece; when the industrial robot 21 controls the elliptical vibration polishing assembly 1 to traverse the optical surface of the workpiece along the polishing trajectory, the normal line of the polishing head 1128 coincides with the normal line of the optical surface of the workpiece. When the vibration polishing head moves to different polishing areas, the liquid supply system can control the liquid supply flow of the peristaltic pump according to the program setting to adapt to the process of rough polishing, fine polishing, etc.

[0050] During polishing, first adjust the cylinder thrust of the pressure regulating cylinder 14 to balance the cylinder thrust with the gravity of the ultrasonic vibration polishing unit 11. Continue to adjust the cylinder thrust of the pressure regulating cylinder 14 to control the soft contact pressure between the polishing head and the workpiece. Control the motor 13 to rotate to drive the ultrasonic vibration polishing unit 11 to rotate synchronously, and at the same time control the ultrasonic elliptical vibrator 112 to output the second-order longitudinal vibration signal and the fourth-order bending vibration signal with the same resonant frequency to drive the polishing head 1128 to perform elliptical vibration to achieve polishing of the workpiece.

[0051] It should be understood that expressions such as "including" and "may include" that may be used in the present application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In the present application, terms such as "including" and / or "having" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0052] In addition, in the present application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0053] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that the relative position relationship after connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference directions of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0054] In addition, in the embodiments of the present application, the mathematical concepts mentioned are symmetry, equality, parallelism, verticality, etc. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense, and allow a small amount of deviation, approximation to symmetry, approximation to equality, approximation to parallelism, approximation to verticality, etc. are all possible. For example, A and B are parallel, which means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0055] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An optical aspheric robot elliptical vibration polishing device, characterized in that: The invention comprises an elliptical vibration polishing assembly (1), wherein the elliptical vibration polishing assembly (1) comprises a pressure regulating cylinder (14), a motor (13), an electric slip ring (12), and an ultrasonic vibration polishing unit (11) which are connected in series in sequence, wherein the main shaft of the motor (13) passes through the electric slip ring (12) and is key-connected with the ultrasonic vibration polishing unit (11); the ultrasonic vibration polishing unit (11) comprises a housing (115) and an ultrasonic elliptical vibrator (112) coaxially fixed in the housing (115); the ultrasonic elliptical vibrator (112) comprises an ultrasonic amplitude transformer (1124) which is coaxially arranged in sequence ), a sleeve (1126) and a clamp (1127); the clamp (1127) passes through the housing (115) and extends to the outside thereof, and a polishing head (1128) is clamped and fixed at its end; the pressure regulating cylinder (14) is used to push the ultrasonic vibration polishing unit (11) so that the polishing head (1128) and the workpiece achieve soft contact; the main shaft of the motor (13) is used to drive the polishing head (1128) to rotate; and the ultrasonic elliptical vibrator (112) is used to drive the polishing head (1128) to perform elliptical vibration via the ultrasonic amplitude transformer (1124).

2. An optical aspheric robot elliptical vibration polishing device as claimed in claim 1, characterized in that: The ultrasonic horn (1124) is made of aluminum alloy or titanium alloy.

3. The optical aspheric robot elliptical vibration polishing device according to claim 1, characterized in that: The pressure regulating cylinder (14) is a double-acting cylinder on which a proportional pressure valve is arranged, and the proportional pressure valve is used to regulate the cylinder thrust.

4. The optical aspheric robot elliptical vibration polishing device according to claim 1, characterized in that: The cylinder push plate of the pressure regulating cylinder (14) is connected to the output shaft of the motor (13).

5. The optical aspheric robot elliptical vibration polishing device according to claim 1, characterized in that: The housing (115) is a hollow cylinder. The ultrasonic elliptical vibrator (112) further comprises a piezoelectric ceramic group and an end cover (1121). The end cover (1121), the piezoelectric ceramic group and the ultrasonic horn (1124) are connected in sequence. The end cover (1121) and the ultrasonic horn (1124) are respectively provided with radially symmetrical stationary point mounting holes (1130). The housing (115) is provided with a stationary point support threaded hole (1129) matching the stationary point mounting hole (1130). The stationary point mounting hole (1130) and the stationary point support threaded hole (1129) are connected via a screw.

6. An optical aspheric robot elliptical vibration polishing device as claimed in claim 5, characterized in that: The ultrasonic vibration polishing unit (11) further comprises an ultrasonic vibration controller (111), an ultrasonic power supply (113) and a power amplifier group (114); the ultrasonic vibration controller (111) is used to determine the resonant operating point of the ultrasonic vibration polishing unit (11) and control the ultrasonic power supply (113) to output an electrical signal of a corresponding frequency to the power amplifier group (114); the power amplifier group (114) is used to amplify the gain of the electrical signal and transmit it to the piezoelectric ceramic group, thereby driving the polishing head (1128) to vibrate in an elliptical trajectory.

7. The optical aspheric robot elliptical vibration polishing device according to claim 1, characterized in that: The polishing device further comprises an industrial robot (21) and a polishing liquid supply module (3); the elliptical vibration polishing assembly (1) is mounted on a processing end of the industrial robot (21); and the liquid outlet end of the polishing liquid supply module (3) is located above the polishing position and is used to supply polishing liquid during polishing.

8. A method for polishing an optical aspheric surface using an elliptical vibration polishing device of an optical robot according to any one of claims 1 to 7, characterized in that: Traversing the workpiece surface for polishing according to the preset running track of the polishing head (1128) includes: S1 adjusts the cylinder thrust of the pressure regulating cylinder (14) so ​​that the cylinder thrust is balanced with the gravity of the ultrasonic vibration polishing unit (11); S2 continues to adjust the cylinder thrust of the pressure regulating cylinder (14) to control the soft contact pressure between the polishing head (1128) and the workpiece; S3 controls the motor (13) to rotate, so as to drive the ultrasonic vibration polishing unit (11) to rotate synchronously, and at the same time controls the ultrasonic elliptical vibrator (112) to output a second-order longitudinal vibration signal and a fourth-order bending vibration signal with a consistent resonance frequency, so as to drive the polishing head (1128) to perform elliptical vibration to achieve polishing of the workpiece.

9. The method according to claim 8, characterized in that Prior to step S1, a fixed-point polishing method is used to obtain a removal function of the polishing head (1128) under a specific material and polishing environment; an interferometer is used to obtain surface error data of the workpiece to be polished, and the removal function and surface error data of the workpiece to be polished are used to obtain the preset running trajectory of the polishing head (1128); and based on the surface error data and curvature of the workpiece, the working parameters of the industrial robot (21) and the corresponding polishing liquid flow rate are planned.

10. The method according to claim 8, characterized in that When the industrial robot (21) controls the elliptical vibration polishing assembly (1) to traverse the optical curved surface of the workpiece along the polishing trajectory, the normal line of the polishing head (1128) coincides with the normal line of the optical curved surface of the workpiece.

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