Apparatus for electrochemically polishing metal workpieces

Abstract

The invention relates to an apparatus for electrochemically polishing metal workpieces, comprising: - a container for holding an electrolyte medium having a plurality of solid granulate particles and having a liquid electrolyte; - a first electrode which is arranged in the interior of the container or is electrically connected to the container; - a workpiece holder, which can be moved relative to the container, for detachably fastening the workpieces; - a second electrode which is electrically connected to the workpiece holder; - a voltage source for applying a voltage to the electrodes; and - an open-loop or closed-loop control device which is set up in terms of programming and which is designed for the open-loop or closed-loop control of the voltage applied between the electrodes and / or of the movement of the workpiece holder relative to the container. According to the invention, the container is equipped with a temperature-control device which has a heat exchanger arranged in the container, the heat exchanger being arranged in a temperature-control chamber of the container which is separated from a processing chamber of the container by means of a screen element suitable for retaining the solid granulate particles of the electrolyte medium.

Description

[0001] Device for electrochemical polishing of metallic workpieces

[0002] The invention relates to a device for the electrochemical polishing of metallic workpieces, comprising:

[0003] - at least one container for holding an electrolyte medium which contains, on the one hand, a plurality of solid granular particles and, on the other hand, at least one liquid electrolyte;

[0004] - at least one first electrode which is located inside the container and / or is in electrically conductive contact with the container;

[0005] - at least one workpiece holder that can be moved relative to the container for the detachable fastening of the workpieces;

[0006] - at least one second electrode which is in electrically conductive contact with the at least one workpiece holder;

[0007] - at least one voltage source to apply an electrical voltage to the electrodes in such a way that the first electrode has a negative voltage at least temporarily and the second electrode has a positive voltage at least temporarily; and

[0008] - a programmed control and / or regulating device, which is designed to control and / or regulate the voltage applied between the electrodes and / or the relative movement of at least one workpiece holder relative to the container.

[0009] For surface finishing of workpieces, so-called drag finishing processes are known, in which the workpiece is immersed in a bed of solid abrasive or polishing granules contained in a container and moved relative to the granules within the bed. Drag finishing machines are typically used for this purpose; these machines are a special type of vibratory finishing machine in which the workpieces to be processed are detachably fixed, for example, individually or on one or more clamping devices of a workpiece holder in the machine, in order to polish or grind them as a result of the relative movement with respect to the bed of granules. Such drag finishing machines often include a usually rotating part, essentially in the form of, for example, a...A rotary-driven plate, driven by a suitable gearbox, to which the workpiece holders are attached directly or indirectly, for example via lifting devices. This attachment is particularly eccentric with respect to the axis of rotation of the rotating part of the drag finishing machine. When this part – the so-called plate – of the drag finishing machine rotates, the workpiece holders attached to it describe a path. The workpieces, supported by the clamping devices of the workpiece holders, are immersed in the container, which is filled with a load of granules, often with the addition of liquid processing media such as water, surfactants, etc. Due to the relative movement of the workpieces with respect to the granules, their surface is treated in the form of a vibratory finishing process. Such drag finishing machines are known, for example, from DE 102 04 267 Gl, DE 200 05 361 Ul, or DE 10 2010 052 222 Al.

[0010] Alternatively or additionally, the container holding the granule particles can be moved relative to the workpieces, which are also moving (e.g., rotated around their own axis) or stationary, for example, around its own axis and / or along a path, such as a circular track. If only the container is moved and the workpieces themselves do not undergo any translational movement, this is also referred to as "immersion grinding" or "immersion polishing" as a special form of drag finishing. Machines in which the workpiece holder supporting the workpiece during surface treatment is essentially stationary are also called immersion finishing machines.

[0011] The granules can be of various origins, depending on the workpieces being treated. These can be of natural origin (e.g., organic material such as walnut or coconut shells, wood, cherry pits, etc.), mineral origin (e.g., silicates, oxides, etc.), and / or synthetic origin (e.g., plastics). Furthermore, as already mentioned, vibratory finishing can be performed dry or wet, using a liquid medium such as water, which may contain additives like surfactants.

[0012] To provide a rotational movement of the workpieces, such as around their own axis, as an alternative or additional to a translational movement relative to the granule particles, resulting in even more effective surface treatment, the workpiece holders of known drag finishing machines are often rotary-driven, for example by means of suitable motors (see, e.g., DE 10 2010 052 222 Al). Furthermore, workpiece holders for drag finishing machines are known whose clamping devices for the detachable fastening of the workpieces are rotatably mounted and can be set in rotation via a shaft rotatably mounted in the workpiece holder. For this purpose, the workpiece holder has, e.g.,A planetary gear with a central sun gear, which meshes with planet gears that are in turn rotationally fixed to a support shaft of a respective clamping device and are arranged around the circumference of the sun gear of the workpiece holder. Due to this movement of the clamping devices rotatably mounted on the workpiece holder, along with the workpieces, which consists of a translational movement (in the direction of rotation of the support element or the "plate" of the drag finishing machine) and a rotational movement (about the axis of the respective clamping device or about the workpiece axis), through the machining medium, a uniform machining quality is achieved with shorter machining times compared to a purely translational movement. Furthermore, alternatively or additionally, the workpiece holder itself can be rotatably fixed to the support element of the drag finishing machine in a corresponding manner (see, e.g.,DE 20 2009 008 070 Ul ) .

[0013] Furthermore, conventional drag finishing processes for polishing or grinding metallic workpieces of the aforementioned type have been further developed into electrochemical polishing processes in such a way that, on the one hand, the metallic workpiece is at least temporarily connected to a positive electrode (anode), and on the other hand, the granule particles flooded with a liquid electrolyte are at least temporarily connected to a negative electrode (cathode), whereby the electrodes are subjected to an electrical voltage and the workpiece is moved relative to the majority of solid granule particles, e.g., in the manner described above. The latter are part of an electrolyte medium which, in addition to the granule particles, comprises a liquid, electrically conductive electrolyte.

[0014] The surface quality of the processed workpieces can often be further improved by electrochemical polishing, which is itself a process of abrasive surface treatment. When the electrodes are subjected to an electrical voltage via a voltage source (see above), in addition to the purely mechanical surface treatment of the metallic workpieces, the electrical conductivity of the liquid electrolyte results in a current flow, which causes the surface anodic removal of material from the metallic workpieces. The electrodes can be supplied with either direct current or pulsed voltages, with the workpiece connected to the positive electrode (anode) and the electrolyte medium or the container holding it connected to the negative electrode (cathode).Typically, the workpieces are also moved in the electrolyte medium to ensure the desired relative movement of the workpieces with respect to the solid granule particles and to minimize the concentration gradient that forms on the surface of the workpieces. A generic method for the electrochemical polishing of metallic workpieces is known, for example, from WO 2024 / 056315 Al or DE 10 2024 112 828 Al, which was not yet published at the priority date of the present application. Furthermore, more recently, attempts have been made to improve methods for the electrochemical polishing of workpieces by using special electrolyte media that contain, on the one hand, a plurality of solid porous granule particles based on polymers, e.g., in the form of ion exchangers, and on the other hand, a liquid electrolyte consisting of an electrically conductive, hydrophilic liquid, e.g.,...from the group of strong inorganic acids and sulfonic acids, include .

[0015] However, it has been shown that, particularly during extended operation of devices of this type for the electrochemical polishing of metallic workpieces, the electrolyte medium, including the container holding it, heats up increasingly. On the other hand, in some cases, especially at the beginning of operation, it may also be desirable to bring the electrolyte medium to a specific operating temperature.

[0016] The invention is based on the objective of further developing a device for the electrochemical polishing of metallic workpieces of the type mentioned above in a simple and cost-effective manner in such a way that excessive heating of the electrolyte medium is reliably avoided even during prolonged operation of the device.

[0017] According to the invention, this problem is solved in a device for the electrochemical polishing of metallic workpieces of the type mentioned above by equipping the container with a temperature control device which has at least one heat exchanger arranged in the container, wherein the heat exchanger is arranged in a temperature control chamber of the container, which is separated from a processing chamber of the container by means of at least one sieve element suitable for retaining the solid granular particles of the electrolyte medium. The inventive design of the container with at least one integrated temperature control device ensures, on the one hand, a structurally simple, robust and, in particular, compact construction, wherein the heat exchanger provides the temperature control device with a large heat exchange surface.On the other hand, due to the separation of the temperature control chamber of the container, which contains the heat exchanger, from the processing chamber by means of the sieve element, only the liquid electrolyte of the electrolyte medium can penetrate the sieve element and come into thermally conductive contact with the heat exchanger, whereas the solid granule particles, which have less mass, are retained in the processing chamber of the container. This results in very efficient temperature control of the electrolyte medium during operation, the liquid electrolyte component of which undergoes significant agitation simply due to the workpiece holder moving relative to the container along with the workpieces being processed, thus largely preventing the formation of temperature gradients in the immediate vicinity of the heat exchanger.

[0018] The heat exchanger of the temperature control device may preferably have at least one coil of pipe which can be supplied with a temperature control medium, wherein the length of the coil of the heat exchanger(s) can be chosen more or less freely depending on the required heat exchange surface.

[0019] In order to supply the heat exchanger of the temperature control device with a temperature control fluid, the heat exchanger expediently has at least one inlet and at least one outlet for the temperature control medium, which, for the purpose of simple and convenient contacting, are arranged particularly on the outside of the container and may, for example, be provided with connection nozzles for the temperature control fluid.

[0020] From a design perspective, it can be provided, for example, that at least one heat exchanger of the temperature control unit is arranged in the base of the container, whereby the heat exchanger can extend, depending on the desired heat exchange surface area, over the entire base of the container or only a section thereof. In this case, the temperature control chamber containing the heat exchanger is located in the base of the container and can be separated from the processing chamber located directly above it by means of the sieve element. Alternatively or additionally, it can be provided, for example, that at least one heat exchanger of the temperature control unit is arranged in the circumferential region of the container, whereby the heat exchanger can again extend, depending on the desired heat exchange surface area, over the entire circumference of the container or only a section thereof.In this case, the temperature control chamber equipped with the heat exchanger is located in the outer circumferential area of ​​the container and can be separated from the processing chamber, which is immediately connected radially inwards, by means of the sieve element.

[0021] According to a further development, the temperature control device may also include at least one double-walled section of the container, which in turn has, in particular, at least one inlet and at least one outlet for a temperature control medium, or with which at least one heat exchanger is connected in series and has at least one inlet and outlet common to it, so that the heat exchanger of the temperature control device, together with the double-walled section of the container, can be supplied with the temperature control medium. Since a purely double-walled design of the container provides a significantly poorer heat exchange compared to the heat exchanger according to the invention, a double-walled temperature control jacket can, for example, serve to pre-temper the temperature control medium before it is supplied to the heat exchanger.

[0022] If desired, it can also be provided that the temperature control chamber of the container, equipped with the heat exchanger, is connected to the processing chamber of the container via a recirculation line equipped with a pump, so that the liquid electrolyte component of the electrolyte medium can be actively returned to the processing chamber of the container after passing through the sieve element and contacting the heat exchanger.

[0023] Furthermore, the container may preferably have at least one temperature sensor designed to determine the temperature of the electrolyte medium and which can, for example, be used to monitor the process temperature during operation.

[0024] In this context, it may be provided that the control and / or regulating device is further configured to control and / or regulate the temperature control device depending on the temperature of the electrolyte medium determined by the temperature sensor. In this case, the sensor is connected to the control and / or regulating device of the apparatus, whereby the control and / or regulating device can, for example, control or regulate a valve in a supply and / or discharge line of the temperature control medium connected to the heat exchanger of the temperature control device, a pump circulating the temperature control medium, or the like.

[0025] Furthermore, it can be provided in a manner known as such in the field of drag finishing machines that the relative movement of the at least one workpiece holder in relation to the container is achieved by at least one relative movement from the group

[0026] - rotational movement of the workpiece holder and / or the container, in particular essentially about an axis of symmetry of the workpiece holder and / or the container;

[0027] - translational movement of the workpiece holder in relation to the container; and

[0028] - Vibration excitation of the workpiece holder and / or the container occurs.

[0029] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the drawings. These show:

[0030] Fig. 1 shows a schematic perspective view of an embodiment of a container equipped with a temperature control device for a device for the electrochemical polishing of metallic workpieces, which is not otherwise shown in the drawing;

[0031] Fig. 2 is a schematic top view of the container with the temperature control device according to Fig. 1; Fig. 3 is a schematic side view of the container with the temperature control device according to Figs. 1 and 2;

[0032] Fig. 4 shows a schematic perspective view of another embodiment of a container equipped with a temperature control device for a device for the electrochemical polishing of metallic workpieces, which is not otherwise shown in the drawing;

[0033] Fig. 5 shows a schematic cross-sectional view of the container with the temperature control device according to Fig. 4; and

[0034] Fig. 6 shows a cross-sectional view of the container with the temperature control device according to Figs. 4 and 5, essentially corresponding to Fig. 5.

[0035] The containers 1 shown in Figures 1 to 3 and Figures 4 to 6 are each part of a device for the electrochemical polishing of metallic workpieces, not shown in detail in the drawings, as is known from the prior art. As already mentioned, the container 1 shown in such devices serves to hold an electrolyte medium, also not shown in the drawings, which contains on the one hand a plurality of solid granular particles and on the other hand a liquid electrolyte, wherein the granular particles are formed, for example, from plastic including various ion exchange materials and can be porous or non-porous. Such devices for the electrochemical polishing of metallic workpieces further comprise one or more movable components relative to the container 1, e.g.Workpiece holders (also not shown) that can be rotated around a pivot axis and / or moved translationally along trajectories are used to detachably secure the workpieces, which are generally positioned above the container 1, so that the workpieces supported by the workpiece holders can be completely immersed in the container 1 – or more precisely: in the electrolyte medium contained therein. Alternatively or in addition to the movement of the workpiece holders with the workpieces, the container 1 itself can also be movable, e.g., rotatable about its central axis. While a first electrode (cathode) is in electrically conductive contact with the container 1, a second electrode (anode) is connected to the container 1.The workpiece holders and the workpieces attached thereto are connected by an electrically conductive connection, the electrodes being connected to a voltage source to apply an electrical voltage to the electrodes such that the first electrode (anode) has a negative voltage at least temporarily and the second electrode (cathode) has a positive voltage at least temporarily. A control and / or regulating device, programmed by a computer, is typically used to control and / or regulate the voltage applied between the electrodes and the relative movement of the workpiece holder(s) relative to the container 1.

[0036] As can be seen from Figures 1 to 3 and Figures 4 to 6, the container 1 has a temperature control device 2, which in this case comprises a heat exchanger 2 arranged in the container 1. In the embodiment shown in the drawings, the latter is formed by a coil of pipe, the length and shape of which can be selected according to the required heat exchange surface and which can be supplied with a temperature control medium by means of an inlet 4a and an outlet 4b arranged on the outside and underside of the container 1, respectively (see Figure 2). The coil of the heat exchanger 3 is arranged in a temperature control chamber 1a of the container 1, which is protected by a sieve element 5 suitable for retaining the solid granular particles of the electrolyte medium (visible only in Figs. 1 and 3, omitted in Figs. 4 and 6 for illustrative purposes and shown in Fig. 1).5 (only indicated by dashed lines) is separated from a processing area 1b of the container.

[0037] In the embodiment shown in Figures 1 to 3, the temperature control chamber 1a of the container 1 is arranged in the bottom region thereof and extends only over a portion of the bottom surface, although it can, of course, also extend substantially over the entire bottom surface (not shown). The temperature control chamber 1a is separated from the processing chamber 1b of the container 1 located above the temperature control chamber 1a by means of the sieve element 5, which is arranged substantially parallel to the bottom of the container, so that only the liquid electrolyte component of the electrolyte medium can pass through the sieve element 5 to be tempered by thermally conductive contact with the heat exchanger 3, whereas the solid granular particles of the electrolyte medium can be retained in the processing chamber 1b of the container 1.If desired, a recirculation line (not shown in the drawing) equipped with a pump can also be provided, which connects the temperature control chamber 1a of the container 1, equipped with the heat exchanger 3, to the processing chamber 1b of the container 1 and serves to actively return temperature-controlled liquid electrolyte from the temperature control chamber 1a to the processing chamber 1b. In the embodiment shown in Figures 4 to 6, the temperature control chamber 1a of the container 1 is arranged in its circumferential region and extends essentially over the entire surface of the container 1. The temperature control chamber 1a is connected by means of a [missing information], which is only shown in the figures.The sieve element 5, indicated by dashed lines, is essentially cylindrical and arranged radially inside the heat exchanger 3, separating it from the processing chamber 1b of the container 1 located radially inside the temperature control chamber 1a, so that only the liquid electrolyte component of the electrolyte medium – e.g., supported by gravitational forces during operation, provided the container 2 is rotatable and / or the workpiece holders are movable essentially along a circular path – can pass through the sieve element 5 to be tempered by thermally conductive contact with the heat exchanger 3, whereas the solid granular particles of the electrolyte medium can be retained in the processing chamber 1b of the container 1.If desired, a recirculation line, not shown in the drawing and equipped with a pump, can also be provided in this case, which connects the temperature control chamber 1a of the container 1 equipped with the heat exchanger 3 to the processing chamber 1b of the container 1 and serves to actively return temperature-controlled liquid electrolyte from the temperature control chamber 1a to the processing chamber 1b.

[0038] In the exemplary embodiment shown schematically in Figs. 4 to 6, the temperature control device 2 comprises, in addition to the heat exchanger 3, a double-walled circumferential section of the container 1, which can be supplied with a temperature control medium, for example by means of an inlet not shown in the drawing and an outlet, e.g. in the form of a suction lance 6.

[0039] Furthermore, in both the embodiment schematically depicted in Figures 1 to 3 and in Figures 4 and 6, it can be provided that the container 1 is equipped with one or more temperature sensors, which serve to determine the temperature of the electrolyte medium and are in particular connected to the control and / or regulating device of the electrochemical polishing device in order to control or regulate the temperature control device 2 depending on the temperature of the electrolyte medium determined by the temperature sensor.

Claims

Patent claims 1. Device for electrochemical polishing of metallic workpieces, comprising: - at least one container ( 1 ) for receiving an electrolyte medium which contains on the one hand a plurality of solid granular particles and on the other hand at least one liquid electrolyte; - at least one first electrode which is arranged inside the container ( 1 ) and / or is in electrically conductive contact with the container ( 1 ); - at least one workpiece holder movable relative to the container ( 1 ) for detachably fastening the workpieces ; - at least one second electrode which is in electrically conductive contact with the at least one workpiece holder; - at least one voltage source to apply an electrical voltage to the electrodes in such a way that the first electrode has a negative voltage at least temporarily and the second electrode has a positive voltage at least temporarily; and - a programmatically configured control and / or regulating device, which is designed for controlling and / or regulating the voltage applied between the electrodes and / or the relative movement of the at least one workpiece holder relative to the container (1), characterized in that the container (1) is equipped with a temperature control device (2) which has at least one arranged in the container (1). comprising a heat exchanger (3), wherein the heat exchanger (3) is arranged in a temperature control chamber (1a) of the container (1), which is separated from a processing chamber (1b) of the container (1) by means of at least one sieve element (5) suitable for retaining the solid granular particles of the electrolyte medium.

2. Device according to claim 1, characterized in that the heat exchanger (3) of the temperature control device (2) has at least one coil of tubing which can be supplied with a temperature control medium.

3. Device according to claim 1 or 2, characterized in that the heat exchanger (3) of the temperature control device (2) has at least one inlet (4a) and at least one outlet (4a) for the temperature control medium.

4. Device according to claim 3, characterized in that the at least one inlet (4a) and the at least one outlet (4a) for the temperature control medium are arranged on the outside of the container (1).

5. Device according to one of claims 1 to 4, characterized in that at least one heat exchanger (3) of the temperature control device (2) - in the bottom area of ​​the container (1) and / or - is located in the perimeter area of ​​the container (1).

6. Device according to one of claims 1 to 5, characterized in that the temperature control device (2) further comprises at least one double-walled section of the Container (1) comprises.

7. Device according to claim 6, characterized in that the double-walled section of the container (1) - has at least one inlet and at least one outlet for a temperature control medium or - with which at least one heat exchanger (2) is connected in series and has at least one inlet and outlet common to it.

8. Device according to one of claims 1 to 7, characterized in that the temperature control chamber (1a) of the container (1) equipped with the heat exchanger (3) is connected to the processing chamber (1b) of the container (1) via a recirculation line equipped with a pump.

9. Device according to one of claims 1 to 8, characterized in that the container (1) has at least one temperature sensor which is designed to determine the temperature of the electrolyte medium.

10. Device according to claim 9, characterized in that the control and / or regulating device is further configured to control and / or regulate the temperature control device depending on the temperature of the electrolyte medium determined by the temperature sensor.

11. Device according to one of claims 1 to 10, characterized in that the relative movement of the at least one workpiece holder in relation to the container (1) is achieved by at least one relative movement from the group - rotary movement of the workpiece holder and / or of the container (1) , in particular substantially about an axis of symmetry of the workpiece holder and / or the container (1) ; - translational movement of the workpiece holder in relation to the container (1) ; and - Vibration excitation of the workpiece holder and / or the container (1) occurs.

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