Medical tibia tray composite polishing device and material removal rate calculation method

Abstract

The invention discloses a medical tibia tray composite polishing device and a material removal rate calculation method. The composite polishing device for the medical tibia support comprises a polishing groove, a rotating clamp arranged in the polishing groove and used for driving the medical tibia support to rotate, a composite machining head arranged above the polishing groove and a power mechanism used for controlling the composite machining head to move. A vortex cavity with an opening facing the polishing groove is formed in the combined machining head, a coil is arranged on the periphery of the combined machining head, an inlet flow channel for introducing magnetorheological polishing liquid into the vortex cavity to form vortex is formed in the upper portion of the combined machining head, and the inlet flow channel becomes narrow and then becomes wide. The invention further discloses a material removal rate calculation method which is obtained through calculation according to the pressure of the polishing machining point, the cavitation collapse impact strength of the cavitation bubbles and the pressure of the bottom of the combined machining head. The medical tibia support has the advantages that pressure in the center area and pressure on the periphery are basically equal, it is guaranteed that abrasive particles are in a high-speed turbulence state when flowing through the surface of the medical tibia support, and the polishing effect is improved.

Description

Technical Field

[0001] The invention relates to the technical field of polishing, and in particular to a medical tibial tray composite polishing device and a material removal rate calculation method. Background Art

[0002] Magnetorheological finishing (MRF) is an advanced processing technology for optical surface polishing that uses magnetorheological polishing fluid to transform into a quasi-solid clamping abrasive under the action of a magnetic field. This technology uses a magnetic field to regulate the rheological properties of the magnetorheological polishing fluid, so that it exhibits quasi-solid properties when a magnetic field is applied. It can be effectively used for the processing of complex surfaces without causing subsurface damage commonly seen in traditional mechanical processing. During the magnetorheological polishing process, the magnetorheological polishing fluid between the magnetorheological polishing fluid vortex extrusion composite processing head and the surface of the medical tibial tray is activated to form a semi-solid state similar to Bingham fluid. When the magnetorheological polishing pad moves relative to the surface of the medical tibial tray, the magnetic particles in the magnetorheological polishing fluid are arranged under the action of the magnetic field and form controllable grinding forces. These forces exert shear forces on the material valleys and peaks on the surface of the medical tibial tray, thereby achieving microscopic and macroscopic surface polishing. The processing process can achieve ultra-high-precision surface flatness and is suitable for optical component processing that requires extremely low surface roughness and precision. It can also process complex curved surfaces and irregular shapes, which is more flexible than traditional methods. Compared with traditional grinding and polishing methods, it will not introduce surface microcracks or subsurface damage, ensuring processing quality and long-term stability. By precisely controlling the magnetic field strength and processing parameters, a highly controllable processing process can be achieved to ensure the consistency and quality of each medical tibial tray. Overall, magnetorheological polishing technology has been proven to be an advanced and effective optical surface processing method, especially suitable for applications with extremely high requirements for surface quality and precision, such as laser optical components, semiconductor manufacturing, etc.

[0003] Magnetorheological polishing fluid polishers have attracted much attention because they can use magnetic fields to control the rheological properties of magnetorheological polishing fluids for precision polishing, but there are indeed some challenges and limitations in practical applications. On the one hand, the polishing pads of magnetorheological polishing fluids are usually flexible, which helps to avoid the formation of sub-surface damage, and can respond quickly and is relatively easy to control. These characteristics give them advantages when dealing with high-precision surface processing. However, the shear yield stress of the magnetorheological polishing fluid itself is relatively low, which limits the ability to provide efficient material removal rates in a single extrusion shear mode and makes it difficult to ensure the uniformity of processing. During the extrusion process, as the extrusion gap decreases, the extrusion normal force tends to increase, which may cause the pressure in the center area to be less than that in the surrounding area, thereby affecting the uniformity of the polishing effect. Summary of the invention

[0004] The purpose of the present invention is to provide a medical tibial tray composite polishing device and a material removal rate calculation method, which can at least partially solve the above technical problems.

[0005] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0006] A medical tibial tray composite polishing device comprises a polishing groove, a rotating fixture arranged in the polishing groove to drive the medical tibial tray to rotate, a composite processing head arranged above the polishing groove, and a power mechanism to control the movement of the composite processing head;

[0007] A vortex chamber with an opening toward the polishing groove is provided in the composite processing head, a coil is provided on the periphery of the composite processing head, and an inlet flow channel is provided on the upper part of the composite processing head for introducing magnetorheological polishing fluid into the vortex chamber to form a vortex. The inlet flow channel includes a first flow channel connected to the outside and a second flow channel connected to the vortex chamber. The cross-sectional area at the inlet of the first flow channel is larger than the cross-sectional area at the outlet of the first flow channel, the cross-sectional area at the inlet of the second flow channel is smaller than the cross-sectional area at the outlet of the second flow channel, and the outlet of the first flow channel is connected to the inlet of the second flow channel.

[0008] In the above-mentioned medical tibial tray composite polishing device, the bottom of the composite processing head is provided with an extrusion strengthening cavity connected with the eddy current cavity, and the extrusion strengthening cavity is trumpet-shaped with the larger end facing the medical tibial tray.

[0009] In the above-mentioned medical tibial tray composite polishing device, a plurality of concentric annular grooves are opened on the inner wall of the extrusion strengthening cavity, and the openings of the annular grooves are facing the medical tibial tray. The depth of all annular grooves close to the center of the extrusion strengthening cavity is greater than the depth away from the center of the extrusion strengthening cavity.

[0010] In the above-mentioned medical tibial tray composite polishing device, there are four inlet flow channels and they are evenly distributed along the circumference of the composite processing head.

[0011] In the above-mentioned medical tibial tray composite polishing device, a processing gap is left between the composite processing head and the medical tibial tray, and the processing gap is 1 mm to 2 mm.

[0012] In the above-mentioned medical tibial tray composite polishing device, the center height of the polishing groove is higher than the height of the periphery, and the periphery of the polishing groove is connected to a recovery pump.

[0013] In the above-mentioned medical tibial tray composite polishing device, the recovery pump is sequentially connected to the agitator, the collection container and the pressure pump, and the pressure pump is connected to the inlet flow channel.

[0014] In the above-mentioned medical tibial tray composite polishing device, the power mechanism includes a CNC slide rail and a CNC fixture slidably arranged on the CNC slide rail, the composite processing head is connected to the CNC fixture, and the CNC fixture is provided with a driving mechanism for driving the composite processing head to rotate.

[0015] The material removal rate calculation method of the medical tibial tray composite polishing device is used. When t = 0s, the magnetic field is turned on and the magnetic particles begin to move according to the Langevin equation.

[0016]

[0017] Where Fi is the electric force of all other dipoles and all images on the i-th dipole; η is the base fluid viscosity; -6πaηvi is the Stokes drag, the main hydrodynamic force of the particle; Ri(t) is the random Brownian force, and M is the mass of the particle;

[0018] The magnetorheological polishing fluid is squeezed in the annular groove, and the pressure in the adhesion core section of the annular groove inlet, i.e. the polishing processing point, is:

[0019]

[0020] Where η N (H) is the viscosity coefficient under the action of magnetic field; η N (0) is the viscosity coefficient without magnetic field; C 0 is the dimensionally normalized gap ratio, that is, the ratio of the gap at this position to the average gap; θ is the angle between the polishing point and the maximum gap;

[0021] When the mixed polishing fluid is injected into the composite processing head from multiple directions, a three-phase vortex flow field is formed in the central part of the vortex cavity. Due to the influence of the wall effect, the magnetorheological polishing fluid on the surface of the medical tibial tray presents a high-speed turbulent state. There are many tiny vortices in the high-speed turbulent flow field. These vortices cause the abrasive particles to make irregular and nonlinear motion on the surface of the medical tibial tray, thereby achieving the effect of surface material removal. During the polishing process, a large number of microbubbles formed in the inlet flow channel collapse under the action of the turbulent vortex. The shock wave and microjet generated after the bubble group collapse can accelerate the nonlinear motion of the abrasive particles. Linear motion, cavitation bubbles split into smaller vortices during the collapse process, and these vortices gradually disappear under the action of fluid viscosity; under the influence of wall effect, boundary disturbance and velocity gradient, new vortices are generated again to form a multiphase flow circulation system. Therefore, increasing the fluid turbulence intensity to produce more strong vortices can effectively enhance the relative motion between the abrasive and the medical tibial tray, thereby achieving the removal of the surface material of the medical tibial tray and achieving an ideal polishing effect. According to the principles of fluid mechanics, the intensity of the cavitation collapse impact at the distance r of the cavitation bubble can be deduced as:

[0022]

[0023] Where P f represents the fluid pressure; R represents the initial radius of the cavitation bubble; represents radial velocity; represents radial acceleration; r represents the distance between any point in the space fluid and the center of the cavitation bubble, that is, the distance between the cavitation bubble and the surface of the medical tibial tray;

[0024] After the coil is energized, an excitation magnetic field from top to bottom is formed inside the composite processing head. Under the action of this magnetic field, a brush-like magnetorheological polishing fluid is formed. The pressure at the bottom of the composite processing head is expressed as:

[0025]

[0026] In the formula, μ 0 represents the vacuum magnetic permeability; N represents the number of magnetic particles; k represents the kth magnetic particle; m represents the magnetic moment between two magnetic particles, R represents the radius of the magnetic particle, V represents its volume, and the magnetic susceptibility of the magnetic particle in a magnetic field with a magnetic field strength of H is χ; θ i represents the angle between two magnetic particles; r represents the distance between two magnetic particles, and its value can be expressed as 2R+2t, and t represents the thickness of the non-magnetic layer of the magnetic particle;

[0027] The total pressure during polishing is:

[0028]

[0029] The total material removal rate is expressed as:

[0030] MRR=K·P·V=K·(P s +P f +P m )·V

[0031] Wherein, K is the Preston constant, which comprehensively reflects the influence of factors other than force and speed-related factors on the material removal process of the component surface. These factors include the type and size of polishing particles, the material properties of the optical component, the moisture content of the polishing liquid and the pH value, which are calculated by taking the average value of multiple experiments; P is the force distribution applied to the surface of the medical tibial tray, and V is the relative speed distribution between the processing tools and the medical tibial tray.

[0032] Compared with the prior art, the advantages of the present invention are: by setting a vortex chamber in the composite processing head, the magnetorheological polishing liquid entering the composite processing head generates a vortex, which increases the polishing pressure on the medical tibial tray, thereby improving the polishing efficiency of the medical tibial tray, and the vortex can increase the pressure in the polishing center area, so that the pressure in the center area covered by the composite processing head and the surrounding area is basically equal. In addition, an inlet flow channel with a cross section from large to small and then to large is provided on the composite processing head. The inlet flow channel of this structure will produce a pressure lower than the saturated vapor pressure of the liquid, generate a large number of cavitation bubbles and cause severe cavitation. The hydraulic cavitation effect is used to increase the number of vortices in the flow field, and a larger vortex is formed after the small vortices in the vortex area are superimposed, thereby ensuring that the abrasive particles are in a high-speed turbulent state when flowing through the surface of the medical tibial tray, thereby improving the polishing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic structural diagram of the medical tibial tray composite polishing device of the present invention;

[0034] Figure 2 It is a schematic diagram of the structure of the composite processing head in the present invention;

[0035] Figure 3 It is a schematic diagram of the magnetorheological polishing fluid in the present invention flowing from the inlet flow channel into the eddy flow area to generate cavitation effect;

[0036] Figure 4 It is a schematic diagram of the structure of the inlet flow channel in the present invention.

[0037] The accompanying drawings are marked as follows:

[0038] Composite processing head 1, coil 2, magnetorheological polishing fluid 3, medical tibial tray 4, CNC clamp 5, CNC slide rail 6, pressure pump 7, collecting container 8, agitator 9, recovery pump 10, polishing tank 11, rotating clamp 12, vortex chamber 101, inlet flow channel 102, first flow channel 103, second flow channel 104, extrusion strengthening chamber 105, annular groove 106, magnetic particles 310, abrasive particles 320, cavitation bubbles 330, shock waves 340, and turbulent vortex 350. DETAILED DESCRIPTION

[0039] A medical tibial tray composite polishing device comprises a polishing groove 11, a rotating fixture 12 arranged in the polishing groove 11 for driving the medical tibial tray 4 to rotate, a composite processing head 1 arranged above the polishing groove 11 and a power mechanism for controlling the movement of the composite processing head 1; a vortex chamber 101 with an opening toward the polishing groove 11 is arranged in the composite processing head 1, a coil 2 is arranged on the periphery of the composite processing head 1, an inlet flow channel 102 for introducing a magnetorheological polishing fluid 3 into the vortex chamber 101 to form a vortex is arranged on the upper part of the composite processing head 1, the inlet flow channel 102 comprises a first flow channel 103 connected to the outside and a second flow channel 104 connected to the vortex chamber 101, the cross-sectional area at the inlet of the first flow channel 103 is larger than the cross-sectional area at the outlet of the first flow channel 103, the cross-sectional area at the inlet of the second flow channel 104 is smaller than the cross-sectional area at the outlet of the second flow channel 104, and the outlet of the first flow channel 103 is connected to the inlet of the second flow channel 104.

[0040] By setting a vortex chamber 101 in the composite processing head 1, the magnetorheological polishing liquid 3 entering the composite processing head 1 generates a vortex, which increases the polishing pressure on the medical tibial tray 4, thereby improving the polishing efficiency of the medical tibial tray 4, and the vortex can increase the pressure in the polishing center area, so that the pressure in the center area and the surrounding areas is basically equal. In addition, an inlet flow channel 102 with a cross section from large to small and then to large is provided on the composite processing head 1. The inlet flow channel 102 of this structure will produce a pressure lower than the saturated vapor pressure of the liquid, generate a large number of cavitation bubbles 330, and cause severe cavitation. The hydraulic cavitation effect is used to increase the number of vortices in the flow field, and a larger vortex is formed after the small vortices in the vortex area are superimposed, thereby ensuring that the abrasive particles 320 are in a high-speed turbulent state when flowing through the surface of the medical tibial tray 4, thereby improving the polishing effect.

[0041] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0042] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0043] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0044] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] See also Figures 1 to 4 This is an embodiment of the medical tibial tray composite polishing device of the present invention, which comprises a polishing groove 11, a rotating fixture 12 arranged in the polishing groove 11 to drive the medical tibial tray 4 to rotate, a composite processing head 1 arranged above the polishing groove 11, and a power mechanism for controlling the movement of the composite processing head 1;

[0046] The polishing groove 11 is in the shape of a groove, and the rotating fixture 12 is arranged in the polishing groove 11. A motor 13 for driving the rotating fixture 12 to rotate is arranged below the polishing groove 11, and the medical tibial tray 4 is clamped on the rotating fixture 12. The composite processing head 1 is arranged above the rotating fixture 12, and the composite processing head 1 is eccentrically arranged with the rotating fixture 12. In addition to rotating along its own axis, the composite processing head 1 can also be driven by a power mechanism to move radially along the polishing groove 11 so as to cover the entire polishing surface of the medical tibial tray 4.

[0047] The composite processing head 1 is made of ferromagnetic material, with a coil 2 wound on the outside. A vortex chamber 101 with an opening toward the polishing groove 11 is provided inside the composite processing head 1. The vortex chamber 101 is cylindrical. The coil 2 is provided on the periphery of the composite processing head 1. An inlet flow channel 102 for introducing the magnetorheological polishing fluid 3 into the vortex chamber 101 to form a vortex is provided on the upper part of the composite processing head 1. The inlet flow channel 102 includes a first flow channel 103 connected to the outside and a second flow channel 104 connected to the vortex chamber 101. The cross-sectional area at the inlet of the first flow channel 103 is larger than the cross-sectional area at the outlet of the first flow channel 103. The cross-sectional area at the inlet of the second flow channel 104 is smaller than the cross-sectional area at the outlet of the second flow channel 104. The outlet of the first flow channel 103 is connected to the inlet of the second flow channel 104. Figure 4As shown, in order to better produce the cavitation phenomenon, the slope of the side wall of the first flow channel 103 is greater than the slope of the side wall of the second flow channel 104, that is, an irregular channel that is wide at first, narrow then wide again is formed in the inlet flow channel 102, and the pressure at a certain point in the inlet flow channel 102 is lower than the saturated vapor pressure of the liquid, resulting in a large number of cavitation bubbles 330 and severe cavitation. The hydraulic cavitation effect is used to increase the number of vortices in the flow field, and small vortices in the vortex zone are superimposed to form a larger vortex, thereby ensuring that the abrasive particles 320 are in a high-speed turbulent state when flowing through the surface of the medical tibial tray 4.

[0048] An extrusion strengthening chamber 105 connected to the turbulence chamber is provided at the bottom of the composite processing head 1. The extrusion strengthening chamber 105 is trumpet-shaped with the larger end facing the medical tibial tray 4. A plurality of concentric annular grooves 106 are provided on the inner wall of the extrusion strengthening chamber 105. The opening of the annular groove 106 faces the medical tibial tray 4. The depth of all grooves close to the center of the extrusion strengthening chamber 105 is greater than the depth away from the center of the extrusion strengthening chamber 105, that is, the cross-section of the annular groove 106 is wedge-shaped. Through the extrusion strengthening principle of the annular groove 106, the magnetic particles 310 are transformed from a single chain into a more stable body-centered cubic result, thereby improving the shear yield stress of the magnetorheological polishing fluid 3 and enhancing the clamping force and shear force on the abrasive particles 320.

[0049] Furthermore, there are four inlet flow channels 102 and they are evenly distributed along the circumference of the composite processing head 1, which improves the uniformity of the magnetorheological polishing fluid 3 entering the vortex cavity 101 in the composite processing head 1 and better forms vortices. A processing gap is left between the composite processing head 1 and the medical tibial tray 4, and the processing gap is 1mm to 2mm. Under the action of the vortex, the magnetorheological polishing fluid 3 becomes a turbulent state. After the coil 2 is powered on and excited, it is squeezed in the gradually converging processing gap under the continuous hydraulic action, and a more solid body-centered cubic structure is formed after chain breaking and reorganization from a single chain state, which improves the removal efficiency of the polishing processing area of ​​the magnetorheological polishing fluid 3.

[0050] In order to strengthen the recycling of the magnetorheological polishing liquid 3 after polishing, the center height of the polishing tank 11 is higher than the height of the periphery, that is, the polishing tank 11 is a structure with a high center and a low periphery, so that the magnetorheological polishing liquid 3 can be gathered to the periphery, and a recovery pump 10 is connected to the periphery of the polishing tank 11 to extract the magnetorheological polishing liquid 3 collected in the polishing tank 11. The recovery pump 10 is connected to the agitator 9, the collection container 8 and the pressure pump 7 in sequence, and the pressure pump 7 is connected to the inlet flow channel 102, thereby realizing the recycling of the magnetorheological polishing liquid 3.

[0051] Furthermore, the power mechanism includes a CNC slide rail 6 and a CNC fixture 5 slidably set on the CNC slide rail 6, the composite processing head 1 is connected to the CNC fixture 5, and the CNC fixture 5 is provided with a driving mechanism for driving the composite processing head 1 to rotate. Through the CNC slide rail 6, the moving distance of the composite processing head 1 along the radial direction of rotation of the medical tibial tray 4 can be accurately controlled, and the CNC fixture 5 can clamp the composite processing head 1 and drive it to rotate along its own axis, thereby realizing multi-track composite polishing of the surface of the medical tibial tray 4.

[0052] Before the magnetic field is applied to the magnetorheological polishing fluid 3, the magnetic particles 310 are randomly distributed. At this stage, the magnetorheological polishing fluid 3 is a suspension. When t=0s, the magnetic field is turned on and the magnetic particles begin to move according to the Langevin equation. Where Fi is the electric force of all other dipoles and all images on the i-th dipole; η is the base fluid viscosity; -6πaηvi is the Stokes drag, the main hydrodynamic force of the particle; Ri(t) is the random Brownian force, and M is the mass of the particle. After 10ms, single chains are formed. At this stage, these chains are not straight, the microstructure has almost no lateral order, the fluid already has a yield shear stress, and its effective viscosity increases significantly. Over time, the microstructure develops into a three-dimensional ordered structure. At t = 0.5s, the magnetic particle 310 chain is straighter, some chains gather together, and lateral order begins to be established. After t = 2.2s, the chains gather to form thick columns. Although the column has a finite thickness in the xy direction and keeps the field direction in its preferred direction, in fact, the columnar structure has a body-centered tetragonal (BCT) lattice structure, the unassisted polymerization process is very slow, the thickness of the column produced is limited, and the actual polishing effect is not greatly improved. After the magnetic field is applied, the magnetorheological polishing fluid 3 is immediately compressed in the field direction, and then a shear force is applied. Single chains are generated within milliseconds under the action of the magnetic field. Compression and shearing force cause these chains to break and then reassemble within milliseconds to form thick magnetic columns with strong tops and ends. In addition, each column is composed of at least hundreds of chains. A robust microstructure of magnetic particle 310 chains is formed during the compression-assisted aggregation process, forming thick columns that are stronger at both ends than in the middle.

[0053] The bottom of the magnetorheological polishing fluid 3 vortex extrusion composite processing head 1 is provided with an annular groove 106, and the cross section of the annular groove 106 is a converging wedge shape. Under the centrifugal effect, the magnetic chain formed by the magnetic particles 310 flows in from the large-area cross section and flows out from the small-area cross section. During the process, it is squeezed in the wedge-shaped space to form a body-centered cubic structure with a larger shear yield stress. The magnetorheological polishing fluid 3 has a greater force to clamp the abrasive particles 320 during the extrusion process, thereby enhancing the polishing efficiency of the magnetorheological vortex extrusion composite polishing equipment. During the wedge extrusion process, the pressure at the polishing processing point is:

[0054]

[0055] Where η N (H) is the viscosity coefficient under the action of magnetic field; η N (0) is the viscosity coefficient without magnetic field; C 0 is the dimensionally normalized gap ratio, that is, the ratio of the gap at this position to the average gap; θ is the angle between the polishing point and the maximum gap.

[0056] When the magnetorheological polishing fluid 3 is injected from multiple directions, the magnetorheological polishing fluid 3 forms a three-phase vortex flow field in the central part of the vortex cavity 101. Due to the influence of the wall effect, the magnetorheological polishing fluid 3 on the surface of the medical tibial tray 4 presents a high-speed turbulent state. There are many tiny vortices in the high-speed turbulent flow field, which prompt the abrasive particles 320 to make irregular and nonlinear movements on the surface of the medical tibial tray 4, thereby achieving the surface material removal effect. During the polishing process, a large number of microbubbles formed in the inlet flow channel 102 collapse under the action of the turbulent vortex 350. The shock wave 340 and microjet generated after the bubble group collapse can accelerate the nonlinear movement of the abrasive particles 320. The cavitation bubbles 330 split into smaller-scale vortices during the collapse process, and these vortices gradually disappear under the action of fluid viscosity; and under the influence of the wall effect, boundary disturbance and velocity gradient, new vortices are generated again to form a multiphase flow circulation system. Therefore, increasing the fluid turbulence intensity to generate more strong vortices can effectively enhance the relative movement between the abrasive particles 320 and the medical tibial tray 4, thereby achieving the removal of the surface material of the medical tibial tray 4 and achieving an ideal polishing effect. According to the principles of fluid mechanics, the intensity of the cavitation collapse impact of the cavitation bubble 330 at a distance r can be deduced as:

[0057]

[0058] Where P f represents the fluid pressure; R represents the initial radius of the cavitation bubble 330; represents radial velocity; represents radial acceleration; r represents the distance between any point in the spatial fluid and the center point of the cavitation bubble 330, that is, the distance between the cavitation bubble 330 and the surface of the medical tibial tray 4.

[0059] After the coil 2 is energized, according to Ampere's law, when the current passes through the conductor, a magnetic field will be formed near the current. The magnetorheological polishing fluid 3 vortex extrusion composite processing head 1 is an electrical pure iron with good magnetic conductivity. When energized, an excitation magnetic field is formed from the bottom to the top of the magnetorheological polishing fluid 3 vortex extrusion composite processing head 1; and from the top to the bottom of the interior. Under the action of this magnetic field, a brush-shaped magnetorheological polishing fluid 3 polishing pad is formed at the bottom of the magnetorheological polishing fluid 3 vortex extrusion composite processing head 1. The pressure of the gradient magnetic field is expressed as:

[0060]

[0061] In the formula, μ 0 represents vacuum magnetic permeability; N represents the number of magnetic particles 310; k represents the kth magnetic particle 310; m represents the magnetic moment between two magnetic particles 310, R represents the radius of the magnetic particle 310, V represents its volume, and the magnetic susceptibility of the magnetic particle 310 in a magnetic field with a magnetic field strength of H is χ; θ i represents the angle between two magnetic particles 310; r represents the distance between two magnetic particles 310, and its value can be expressed as 2R+2t, and t represents the thickness of the non-magnetic layer of the magnetic particle 310.

[0062] Therefore, the total pressure of the magnetorheological vortex extrusion composite polishing equipment during the polishing process is:

[0063] P=P s +P f +P m

[0064]

[0065] The total material removal rate is expressed as:

[0066] MRR=K·P·V=K·(P s +P f +P m )·V

[0067] Among them, K is the Preston constant, which comprehensively reflects the influence of other factors except the force and speed related factors on the material removal process of the component surface, including the type and size of polishing particles, the properties of the optical component material, the moisture content and pH value of the polishing liquid, etc. It is calculated by taking the average value of multiple experiments. P is the distribution of the force applied to the surface of the medical tibial tray 4. V is the relative speed distribution between the processing tool and the medical tibial tray 4.

[0068] Under the composite strengthening effect of vortex extrusion, the magnetorheological polishing liquid 3 provides a large polishing force; the driving method is simple, and only the magnitude of the excitation current and the power of the pressure pump 7 need to be simply controlled. Without the need for a complex electronic control system, precise control of the polishing device can be achieved, which is convenient for finding the optimal process parameters, subsequent maintenance and reducing costs.

[0069] The above description is only a specific embodiment of the present invention, but the technical features of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are included in the patent scope of the present invention.

Claims

1. A medical tibial tray composite polishing device, characterized in that: It comprises a polishing groove, a rotating fixture arranged in the polishing groove to drive the medical tibial tray to rotate, a composite processing head arranged above the polishing groove, and a power mechanism to control the movement of the composite processing head; A vortex chamber with an opening toward the polishing groove is provided in the composite processing head, a coil is provided on the periphery of the composite processing head, and an inlet flow channel is provided on the upper part of the composite processing head for introducing magnetorheological polishing fluid into the vortex chamber to form a vortex. The inlet flow channel includes a first flow channel connected to the outside and a second flow channel connected to the vortex chamber. The cross-sectional area at the inlet of the first flow channel is larger than the cross-sectional area at the outlet of the first flow channel, the cross-sectional area at the inlet of the second flow channel is smaller than the cross-sectional area at the outlet of the second flow channel, and the outlet of the first flow channel is connected to the inlet of the second flow channel.

2. The medical tibial tray composite polishing device according to claim 1, characterized in that: An extrusion strengthening cavity communicated with the eddy current cavity is arranged at the bottom of the composite processing head. The extrusion strengthening cavity is trumpet-shaped, and a larger end of the cavity faces the medical tibial tray.

3. The medical tibial tray composite polishing device according to claim 2, characterized in that: The inner wall of the extrusion strengthening cavity is provided with a plurality of concentric annular grooves, the openings of the annular grooves face the medical tibial tray, and the depth of all the annular grooves close to the center of the extrusion strengthening cavity is greater than the depth of the side away from the center of the extrusion strengthening cavity.

4. The medical tibial tray composite polishing device according to claim 1, characterized in that: There are four inlet flow channels which are evenly distributed along the circumference of the composite processing head.

5. The medical tibial tray composite polishing device according to claim 1, characterized in that: A processing gap is left between the composite processing head and the medical tibial tray, and the processing gap is 1 mm to 2 mm.

6. The medical tibial tray composite polishing device according to claim 1, characterized in that: The center height of the polishing groove is higher than the periphery height, and the periphery of the polishing groove is connected to a recovery pump.

7. The medical tibial tray composite polishing device according to claim 6, characterized in that: The recovery pump is connected to a stirrer, a collection container and a pressure pump in sequence, and the pressure pump is communicated with the inlet flow channel.

8. The medical tibial tray composite polishing device according to claim 1, characterized in that: The power mechanism comprises a numerical control slide rail and a numerical control fixture slidably arranged on the numerical control slide rail, the composite processing head is connected to the numerical control fixture, and the numerical control fixture is provided with a driving mechanism for driving the composite processing head to rotate.

9. A method for calculating the material removal rate using a medical tibial tray composite polishing device, characterized in that: When t = 0s, the magnetic field is turned on and the magnetic particles begin to move according to the Langevin equation Where Fi is the electric force of all other dipoles and all images on the i-th dipole; η is the base fluid viscosity; -6πaηvi is the Stokes drag, the main hydrodynamic force of the particle; Ri(t) is the random Brownian force, and M is the mass of the particle; The magnetorheological polishing fluid is squeezed in the annular groove, and the pressure in the adhesion core section of the annular groove inlet, i.e. the polishing processing point, is: Where η N (H) is the viscosity coefficient under the action of magnetic field; η N (0) is the viscosity coefficient without magnetic field; C0 is the dimensionally normalized gap ratio, that is, the ratio of the gap at this position to the average gap; θ is the angle between the polishing point and the maximum gap; When the mixed polishing fluid is injected into the composite processing head from multiple directions, a three-phase vortex flow field is formed in the central part of the vortex cavity. Due to the influence of the wall effect, the magnetorheological polishing fluid on the surface of the medical tibial tray presents a high-speed turbulent state. There are many tiny vortices in the high-speed turbulent flow field. These vortices cause the abrasive particles to make irregular and nonlinear motion on the surface of the medical tibial tray, thereby achieving the effect of surface material removal. During the polishing process, a large number of microbubbles formed in the inlet flow channel collapse under the action of the turbulent vortex. The shock wave and microjet generated after the bubble group collapse can accelerate the nonlinear motion of the abrasive particles. Linear motion, cavitation bubbles split into smaller vortices during the collapse process, and these vortices gradually disappear under the action of fluid viscosity; under the influence of wall effect, boundary disturbance and velocity gradient, new vortices are generated again to form a multiphase flow circulation system. Therefore, increasing the fluid turbulence intensity to produce more strong vortices can effectively enhance the relative motion between the abrasive and the medical tibial tray, thereby achieving the removal of the surface material of the medical tibial tray and achieving an ideal polishing effect. According to the principles of fluid mechanics, the intensity of the cavitation collapse impact at the distance r of the cavitation bubble can be deduced as: Where P f represents the fluid pressure; R represents the initial radius of the cavitation bubble; represents radial velocity; represents radial acceleration; r represents the distance between any point in the space fluid and the center of the cavitation bubble, that is, the distance between the cavitation bubble and the surface of the medical tibial tray; After the coil is energized, an excitation magnetic field from top to bottom is formed inside the composite processing head. Under the action of this magnetic field, a brush-like magnetorheological polishing fluid is formed. The pressure at the bottom of the composite processing head is expressed as: In the formula, μ0 represents the vacuum magnetic permeability; N represents the number of magnetic particles; k represents the kth magnetic particle; m represents the magnetic moment between two magnetic particles, R represents the radius of the magnetic particle, V represents its volume, and the magnetic susceptibility of the magnetic particle in a magnetic field with a magnetic field strength of H is χ; θ i represents the angle between two magnetic particles; r represents the distance between two magnetic particles, and its value can be expressed as 2R+2t, and t represents the thickness of the non-magnetic layer of the magnetic particle; The total pressure during polishing is: The total material removal rate is expressed as: MRR=K·P·V=K·(P s +P f +P m )·V Wherein, K is the Preston constant, which comprehensively reflects the influence of factors other than force and speed-related factors on the material removal process of the component surface. These factors include the type and size of polishing particles, the material properties of the optical component, the moisture content of the polishing liquid and the pH value, which are calculated by taking the average value of multiple experiments; P is the force distribution applied to the surface of the medical tibial tray, and V is the relative speed distribution between the processing tools and the medical tibial tray.

Images