Apparatus and method for electrolyte flow control in electrochemical polishing apparatus

Abstract

A method and apparatus for controlling electrolyte flow about a component in an electrochemical polishing process, wherein the component or components are located in a polishing chamber and held by a holder, and an electrolyte supply system is provided including one or more adjustable nozzles through which the electrolyte is introduced and directed into the chamber and around the one or more components, wherein the current at the surface of the component or components is measured and the output and / or direction of the electrolyte from the one or more nozzles is adjusted to produce substantially a required flow profile of the electrolyte solution to achieve the required surface finish of said component or components external surface.

Description

[0001] Apparatus and Method for Electrolyte Flow Control in Electrochemical polishing apparatus

[0002] The present invention relates generally to the field of electrochemical polishing, and more specifically to a system and method for controlling the flow of electrolyte fluid around a submerged component using computational fluid dynamics (CFD) to achieve a target level of surface roughness or uniformity. In particular the invention is directed at providing a relatively uniform surface finish on a surface of a relatively complex shape.

[0003] Electrochemical polishing is a widely used technique for the finishing of metal components by inducing a reduction reaction at the surface of the same, and the work undertaken offers a variety of benefits such as improved surface quality, reduced friction, and / or enhanced corrosion resistance. However, achieving the desired target levels of surface roughness and uniformity can be challenging due to the complex flow patterns of the electrolyte fluid around the component, which can lead to uneven polishing rates in components with non-uniform geometries and in different regions or areas of the component surface. It is known that flowing electrolyte across a surface can increase the rate of reduction at certain portions or areas compared to others which can result in uneven polishing of non- uniform components. This problem is exacerbated when the shape of the surface is relatively complex and includes recesses, protrusions and the like in large numbers and / or of relatively small dimensions.

[0004] A conventional method for determining the desired electrolyte flow about the component is to model the same using CFD software and calculate the desired flow rate. However, there is often no means of feedback in this method, which may still result in uneven and varying polishing effects due to one or more external factors such as, for example, temperature, variation in flow, inconsistencies in the article surface, or the like.

[0005] Another known method is to constantly monitor the surface of the component, visually or by using graphic card technology, as it undergoes polishing However, this method can be time-consuming and / or resource-intensive, and is problematic in terms of being able to obtain sufficient clarity of view of the surface due to the electrolyte fluid in which the component is located.

[0006] As a result, current methods for controlling electrolyte flow are often limited in their precision and ability to be useful for relatively complex shaped surfaces and / or to adapt to changing conditions, resulting in sub-optimal polishing outcomes. Therefore, there is a need for a more advanced system and method for controlling electrolyte flow in electrochemical polishing processes to achieve target surface roughness and uniformity.

[0007] An aim of the present invention is to address the problems indicated above with respect to the current methods known in the art by providing a system that enables uniform polishing of a surface of a component and in particular components with a non-uniform surface geometry.

[0008] A further aim of the invention is to provide a means to accurately determine the time to terminate the polishing process such that at said time the required polishing and surface finish effect has been completed substantially uniformly across the surface of the component, and prevent the expense and additional time being spent which will have no additional beneficial effect. In a first aspect of the invention there is provided a method for controlling electrolyte flow about a component in an electrochemical polishing process, said method comprising the steps of: locating said component in a chamber with an electrolyte fluid, connecting said component and / or a component holder to act as an anode, providing the chamber and / or another member to act as a cathode, said anode and electrode connected to a power supply to create a material reduction at the exposed surface of the said component; measuring the electrical current at the interface between the surface of the component and the electrolyte fluid; including at least one nozzle through which the electrolyte fluid passes to be introduced into and / or moved within the chamber; calculating a required flow profile of the electrolyte fluid within the chamber to produce a predetermined reduction across at least one portion of the exposed surface of the component; monitoring the electrical current during electrochemical processing; and adjusting and controlling the electrolyte output and / or direction of the at least one nozzle with respect to said required flow profile of the electrolyte fluid reduction if necessary so as to produce substantially said required flow profile of the electrolyte solution, and hence achieve the required surface finish of said component.

[0009] In one embodiment the control is provided in order to achieve the flow profile to allow a substantially uniform reduction across the surface of said at least one portion of the component, and hence a substantially uniform surface finish. Typically, the monitoring of the electrical current and adjustment, if necessary, of the control parameters, occurs continuously or at time intervals.

[0010] In one embodiment the said component has a non-uniform surface geometry and the control of the electrolyte fluid is made with respect to the whole surface of the component to allow a substantially uniform surface finish to be achieved.

[0011] In one embodiment any, or any combination, of flow rate, flow pattern, flow velocity, pressure output and / or direction of the nozzle with respect to the component is variable by said control means. Typically a plurality of nozzles are provided and each is independently controllable.

[0012] In one embodiment the variation of the operation of the nozzles is such as to direct relatively fresh or clean electrolyte liquid to those parts of the surface at which an increased rate of material reduction is required in comparison to other parts of said surface.

[0013] In one embodiment the control means varies the output and / or direction of the at least one nozzle by varying the output of a pump by which the nozzle is supplied and / or varying the angle and / or cross section of a conduit for the emission of the electrolyte fluid by an actuating means. In one embodiment the fluid conduit includes a shutter mechanism which can be moved between open, partially closed, and closed positions.

[0014] In one embodiment any or any combination of the parameters is measured substantially continually and / or at increments throughout the polishing, such that the flow profile may be adjusted continually throughout the polishing. In one embodiment the flow profile is calculated by a fluid dynamics computational module, said module using computational fluid dynamics algorithms. Typically, the computational module implements artificial intelligence to calculate the flow profile.

[0015] In one embodiment the computational module receives input data comprising any or any combination of the geometry of the component, desired surface roughness or uniformity targets, electrolyte properties, nozzle output and / or data from the nozzle control means.

[0016] In one embodiment the nozzle control means comprises a processor, memory, and input / output devices for communication with the fluid dynamics computational module and the adjustable nozzle.

[0017] In one embodiment the calculated flow profile is such that a higher electrolyte flow rate occurs at areas of the surface of the component where the measured electrical current is lower, such that the reduction rate is increased.

[0018] Typically, the electrolyte flow rate and the distance between the surface of the component and an activated electrode influences the rate of reduction at a location on the surface of a component.

[0019] Typically the electrolyte solution is an ionic solution.

[0020] Typically there are a plurality of nozzles and in one embodiment each nozzle output and / or direction is independently controlled.

[0021] In another aspect of the invention there is provided apparatus for an electrochemical polishing process, said apparatus including: control means for controlling electrolyte flow about at least one component; a chamber containing an electrolyte solution; a component holder for positioning the component within the chamber; an electrolyte supply system for moving the electrolyte in the chamber and / or introducing fresh electrolyte into the chamber and around the component including at least one nozzle for directing the electrolyte flow within the chamber.

[0022] In one embodiment the apparatus includes a monitoring means to measure the electrical current at the surface of the component; said control means calculating a flow profile of the electrolyte solution within the chamber necessary to produce a pre-determined reduction across the said at least portion of said surface of the component so as to achieve a predetermined surface finish, said control means receiving output data from the measuring means continuously or at time intervals to calculate the surface finish during operation of the apparatus and adjusting the output and / or direction of the at least one nozzle and / or determining that the electrochemical polishing process is complete.

[0023] In one embodiment the flow profile is calculated by a fluid dynamics computational module, said module using computational fluid dynamics algorithms.

[0024] In one embodiment the said component has a non-uniform profile and / or substantially all of the external surface of the component is contacted by the electrolyte. In one embodiment the holder and / or component acts as an anode and the apparatus includes a cathode, both of which are in contact with the electrolyte fluid.

[0025] In one embodiment the chamber acts as the cathode.

[0026] In another embodiment a cathode is inserted into the electrolyte fluid.

[0027] Typically the chamber is formed of a electrical current carrying material. In one embodiment the said material is conductive and in one example the chamber is formed of stainless steel.

[0028] In one embodiment, the apparatus includes a video capturing means so as to allow images of the component surface to be captured and assessed so as to perform an evaluation visually or using visual processing apparatus of the condition of the surface finish during the process.

[0029] In one embodiment, the component holder is provided to allow movement of the same with respect to the chamber such as to allow the removal of the component from the chamber and hence electrolyte fluid to a sufficient extent to allow a visual analysis to be performed.

[0030] In one embodiment, the component and holder are moved at least once during the process to allow at least one visual analysis to take place. More typically, the holder and component may be moved a plurality of times at timed intervals during the process to allow the visual analysis to be performed. Of a result of the visual analysis, the decision made may be to continue the process as it is, adjust one or more parameters of the process or stop the process as the required surface finish has been achieved.

[0031] Specific embodiments of the invention are now described with reference to the accompanying drawings wherein:

[0032] Figures la-c illustrate an embodiment of the apparatus and method for controlling electrolyte flow in accordance with the invention;

[0033] Figures 2a-c illustrate a further embodiment of apparatus in accordance with the invention;

[0034] Figures 3a-e illustrate the chamber of Figures 2a-c and holding system; and

[0035] Figure 4 illustrates a yet further embodiment of apparatus in accordance with the invention.

[0036] Referring firstly to Figure la there is illustrated a system for electrochemical polishing of a component 2 which, in this case, has a non-uniform geometry. The component 2 is connected to a positive terminal 4 of a power supply. The component 2 is located within a chamber 6 and submerged in an electrolyte 8 which is an ionic solution. Also substantially located within a chamber is an electrode 10 connected to a negative terminal 12 of a power supply, in this embodiment the same power supply as the positive terminal.

[0037] The component 2 is located by a component holder 14 located proximal to the electrode 10. The chamber includes a plurality of sensors 16 that remotely measure the electrical current across the surface of the component 2. Located within the chamber 6 is an adjustable nozzle 18. The nozzle 18 supplies a jet within the chamber 6 to create a flow of electrolyte about the component 2.

[0038] Figure lb illustrates the system on activation of the electrodes. The electrode 10 connected to the negative terminal 12 acts as a cathode, and the electrolyte solution 8 enable reduction to occur at the metal surface of the component 2. Given the non-uniform geometry of the component 2, the rate of reduction is greater on the surface of the component 2 that is located closer to the cathode 10.

[0039] The products of the reduction are suspended within the solution 8 proximal the component 2, forming a layer 20. This layer 20 reduces the rate of reduction at the surface of the component 2 as it acts as an insulating layer, increasing electrical resistance. At areas of higher rate of reduction on the surface of the component 2, the layer will be deeper, and the electrical current at the surface of the component will be reduced.

[0040] The sensors 16 measure this variance of electrical current across the surface of the component 2. This measurement is received by a computer, which determines which flow rate across the surface of the component will result in a substantially uniform electrical current measurement across the same. This computer includes a fluid dynamics module which determines the necessary direction of the adjustable nozzle 18 and the flow rate, cross-sectional area, pressure and profile of the jet 22 from the same, as seen in Figure 1c.

[0041] The electrical current across the surface of the component 2 will continue to be monitored throughout the polishing process, and these measurements will be continually received by the computer. The computer implements machine learning or another suitable artificial intelligence procedure to continually adapt the output and direction of the one or more nozzles 18 so as to adapt the output and / or direction of flow in response to the monitoring data and so as to substantially maintain a uniform polishing effect on the surface of the component. The direction of the nozzle 18 is selectively variable by a positioning arm (not shown) and the output of the nozzle 18 is determined by varying the output of an electrolyte pump not shown) supplying the nozzle 18. In another example, the supply of electrolyte solution to the nozzle 18 from the pump may be fixed, and the output from the same is varied by the actuation of a mechanical flow deflector or conduit. Such deflector may include a shutter mechanism, including panels that may be selectively angled by an actuating means controlled by the controller.

[0042] The process will continue for a predetermined period of time before the electrodes are disconnected from the power source. Alternatively, an additional sensor may be included in the chamber to measure the surface roughness of the component 2, which may trigger the power source to be disconnected upon reaching a threshold surface roughness. Further alternatively, the computer may be programmed to detect the changes in the electrical current levels of the surface of the item 2 as it undergoes the polishing process, as the polishing process ends and a passive layer forms, the electrical current will significantly decrease.

[0043] Referring now to Figures 2a-e, there is illustrated apparatus in accordance with a further embodiment of the invention. In this embodiment, the same reference numerals are used for the same components as referred to in Figures la-c. The apparatus again comprises a chamber 6 which acts as a bath 7 and submerged in the electrolyte 8. The holder and component act as the positive terminal 4 or anode and in this embodiment, the chamber itself acts as the electrode 10, with the chamber formed, for example, of stainless steel. In this embodiment, the chamber is formed in an octagonal form as illustrated in the plan view of the chamber in Figure 2c but also could be of other geometrical shapes and may be for example circular. In addition, the chamber is provided with a plurality of nozzles 18 at spaced locations on the side walls and each of which is independently controllable and faces inwardly of the chamber so as to allow the directional flow of electrolyte fluid therefrom. In this embodiment, the walls of the chamber are shaped so as to form three stages, an upper stage 30 in which the walls are substantially vertical, a second stage 32 in which the walls converge at a uniform angle and a third stage 34 at which the walls converge further at a shallower angle. Each of the stages includes a plurality of nozzles 18 in the side walls as illustrated in Figure 2c so that in this example, 24 nozzles would be provided. The nozzles 24 are provided to be substantially flush with the walls of the chamber 6, so as to reduce the effect of the electrochemical polishing on the nozzles and the adjusting mechanisms themselves. Due to the change in angle of the walls in the different stages, the nozzles are directed to emit electrolyte fluid at different angles into the bath of electrolyte fluid by default, and may be further adjusted to allow variation in the angle within a predetermined range of movement. Typically, the nozzles are operated between on and off positions and / or to allow variation in the amount of fresh electrolyte fluid which is introduced from each nozzle so as to allow the direction of fresh electrolyte fluid towards those areas, typically, at which a greater surface finish effect and material reduction is required than others and / or to cause a disruption in the flow of electrolyte fluid within the bath, with typically, the aim being to provide either a uniform surface finish effect across the portion of the external surface of the component and / or various surface finish effects to be created at different portions of the said external surface. The parameters are typically adjusted so as to provide a substantially uniform electrical current at all parts of the external surface portion when a uniform surface finish to be achieved and the variation in the parameters can be related to the flow, temperature, pH and / or conductivity of the electrolyte material.

[0044] Typically, the holder is provided in the form of a cassette 40 from which the component or components can be hung. The cassette 40 is movable along the length of a spigot 42 to lower and raise the cassette towards and away from the chamber 6 to submerge the component 2 in the bath 7 of electrolyte 8. The depth of submersion of the component into the bath is adjustable depending on the particular component, depth of the bath and parameters of the chambers. An example of a locating apparatus 39 is illustrated in Figures 3a-e. The cassette 40, hidden in Figure 3e, is located with an arm 44 to be aligned with the centre of the chamber 6. The arm 44 is mounted with the spigot 42 by a linear actuator 46 so that the height of the cassette 40 with respect to the chamber 6 is selectively variable, as indicated by arrow 36. A power source 48 drives the linear actuator, and the holding assembly 39 and chamber 6 are mounted on a stand 50.

[0045] Figure 4 illustrates a yet further embodiment wherein the chamber 6 acts as the cathode. In this case, the chamber is provided in the form of a trough in which the bath of electrolyte fluid 8 is located. The holder allows relative movement of the component located thereon with respect to the bath as indicated by the arrow 36. In this embodiment, visual inspection cameras 38 are provided. Periodically, throughout the electrochemical polishing of the component, the component is raised from the electrolyte and the cameras 38 are activated to perform visual inspection of the surface of the component. This inspection is then used as a means to verify the electrical current readings taken by the sensors 16 as to the surface quality of the component. On completion of the visual inspection which is analysed by a user and / or an artificial intelligence, the process may continue under the previous parameters, one or more parameters of the process may be adjusted or the process may be stopped as the required surface finish has been achieved.

[0046] There is therefore provided in accordance with the invention a method and apparatus which allows control of the flow of electrolyte during the electrochemical polishing process and, if necessary, the adjustment of the flow rate and direction to achieve target surface roughness or uniformity across the component. The apparatus includes the polishing chamber, a holder for one or more components, an electrolyte supply system, one or more adjustable nozzles through which the electrolyte is introduced and directed into the chamber and around the one or more components. The fluid flow is in one embodiment controlled using a monitoring and feedback system utilising a fluid dynamics computational module and a control system to allow subsequent parameter adjustments to be made if necessary. The method involves positioning the component in the polishing chamber, circulating the electrolyte, directing the flow using adjustable nozzles, calculating the flow patterns and velocities with the fluid dynamics computational module, generating optimal flow data, and adjusting the flow rate and direction based on the output data.

[0047] As a result of the invention there is provided an improved control over the electrolyte flow, resulting in enhanced surface roughness and uniformity in electrochemical polishing processes and as a result improved component quality and a reduction in component rejection.

Claims

CLAIMS1. A method for controlling electrolyte flow about a component in an electrochemical polishing process, said method comprising the steps of: locating said component in a chamber with an electrolyte fluid, connecting said component and / or a component holder to act as an anode, providing the chamber and / or another member to act as a cathode, and connecting said anode and electrode to a power supply to create a material reduction at the exposed surface of the said component; measuring the electrical current at the interface between the surface of the component and the electrolyte fluid; including at least one nozzle through which the electrolyte fluid passes to be introduced into and / or moved within the chamber; calculating a required flow profile of the electrolyte fluid within the chamber to produce a predetermined reduction across at least one portion of the exposed surface of a component; monitoring the electrical current during the electrochemical processing; and adjusting and controlling the electrolyte output and / or direction from the at least one nozzle with respect to the said required flow profile of the electrolyte fluid reduction, if necessary, so as to produce substantially said required flow profile of the electrolyte solution to achieve the required surface finish of said component external surface.

2. A method according to claim 1 wherein the required flow profile is to produce a substantially uniform reduction across the surface of said at least portion of the component and hence a substantially uniform surface finish thereon.3 A method according to claim 1 wherein the required flow profile is to produce a differential reductions at different parts of the surface of said at least portion of the component to provide a predefined surface finish thereon.

4. A method according to claim 1 wherein the monitoring of the electrical current and adjustment, if necessary, of the control parameters of operation of the nozzles occurs continuously.

5. A method according to claim 1 wherein the monitoring of the electrical current and adjustment, if necessary, of the control parameters of the said at least one nozzle, is performed at time intervals during the processing.

6. A method according to any of the preceding claims wherein the said component has a non-uniform surface geometry and adjustment of the electrolyte fluid provided to different parts of the said external surface is made so as to provide variation in the material reduction.

7. A method according to any of the preceding claims where any or any combination of flow rate, flow pattern, flow velocity, pressure, output and / or direction of output from the nozzle with respect to the component is variable by said control means.

8. A method according to any of the preceding claims wherein a plurality of nozzles are provided and each is independently controllable.

9. A method according to any of the preceding claims wherein the variation of the operation of the nozzles is such as to direct relatively fresh or clean electrolyte fluid to those parts of the surface at which an increased rate of material reduction is required relative to other parts of said surface.

10. A method according to any of the preceding claims wherein the control means varies the output and or direction of the at least one nozzle by varying the output of a pump by which the at least one nozzle is supplied with said electrolyte fluid and / or varying the angle and / or cross section of a conduit for the emission of the electrolyte fluid by actuating means.

11. A method according to claim 10 wherein the fluid conduit includes a shutter mechanism which can be selectively moved between open, partially closed and closed positions.

12. A method according to any of the preceding claims wherein any or any combination of the control parameters of the operation of the at least one nozzle are measured substantially continuously throughout the process.

13. A method according to any of the preceding claims wherein the measurement of any or any combination of control parameters of the operation of the at least one nozzle occurs at time intervals through the process.

14. A method according to any of the preceding claims wherein the said flow profile as calculated by a fluid dynamics computational module.

15. A method according to claim 14 wherein the computational module received input data comprising any or any combination of the geometry of the component, desired surface finish and / or uniformity requirements, electrolyte properties and nozzle output data.

16. A method according to any of the preceding claims wherein the nozzle control means comprises a processor, memory and input / output devices for communication with the fluid dynamics computational module.

17. A method according to any of the preceding claims wherein the calculated flow profile can, if a substantially uniform surface finish is required, direct a higher electrolyte flow and / or fresh electrolyte fluid towards areas of the surface of the component so as to enable the electrical current at that said component to be substantially the same as that at other parts of the external surface of the component so that there is a uniform electrical current value at all parts of the exposed surface of the component.

18. A method according to any of the preceding claims wherein electrolyte fluid is an ionic solution.

19. Apparatus for an electrochemical polishing process, said apparatus including: a control means for controlling electrolyte flow about at least one component held in a bath of electrolyte fluid; a chamber forming said bath and containing said electrolyte fluid; a component holder for positioning a component within the chamber and bath; an electrolyte supply system for moving the electrolyte in the chamber and / or introducing fresh electrolyte into the chamber and around thecomponent including at least one nozzle for directing electrolyte flow within the chamber.

20. Apparatus according to claim 19 wherein the apparatus includes a measuring means to measure the electrical current at the surface of the component; wherein said control means calculating a flow profile of the electrolyte solution within the chamber necessary to produce a predetermined reduction across the said at least one portion of said surface of said component so as to achieve a predetermined surface finish, said control means receiving output data from the measuring means continuously or at time intervals to calculate the surface finish during operation of the apparatus and adjusting the output and / or direction of the at least one nozzle and / or determining that the electromechanical polishing process is complete.

21. Apparatus according to claim 20 wherein the flow profile as calculated by a fluid dynamics computational module.

22. Apparatus according to any of claims 19-21 wherein the said component has a non-uniform profile and substantially all of the external surface of the component is in contact with the electrolyte fluid when the component is placed into the said bath.

23. Apparatus according to claim 22 wherein the holder and / or component acts as an anode and the apparatus includes a cathode, both of which are in contact with the electrolyte fluid and a power supply.

24. Apparatus according to any of claims 19-23 wherein the chamber acts as a cathode.

25. Apparatus according to any of the claims 19-24 wherein the anode is inserted into the electrolyte fluid in the bath.

26. Apparatus according to any of claims 19-25 wherein the chamber is formed of an electrical current carrying material.27 Apparatus according to claim 26 wherein the said material is conductive.

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