Cleaning attachment and method for machining, in particular structuring, of a surface of a workpiece by means of a laser

Abstract

The present invention relates to a cleaning attachment (5) for a workpiece (1) having a surface (8) to be processed by laser radiation, wherein the workpiece (1) has a cavity (10) open on at least one side of the workpiece (1), and wherein the surface (8) to be processed is a surface disposed within the cavity (10). The cleaning attachment includes: a central opening (6) through the cleaning attachment (5); at least one cleaning gas supply channel (11) extending through the cleaning attachment (5) and having a connector (13) for a cleaning gas supply line at a first end and an outlet opening (14) at a second end; at least one cleaning gas suction channel (12) extending through the cleaning attachment (5) and having a connector (16) for a cleaning gas discharge line at a first end and... The second end has an inlet opening (17), and the outlet opening (14) of the at least one cleaning gas feed channel (11) and the inlet opening of the at least one cleaning gas suction channel (12) are arranged on opposite sides of the central opening (6); and at least one centering portion is designed to interact with a centering region arranged on the side of the workpiece (1), such that the central opening (6), the outlet opening (14), and the inlet opening (17) communicate with the chamber (10). The invention also relates to a method for processing, particularly structuring, the surface of a workpiece using a laser, and to a method for manufacturing a sensor for determining at least one process variable of a medium in a container.

Description

Technical Field

[0001] This invention relates to a cleaning accessory and to a method for processing, particularly structuring, the surface of a workpiece using a laser. Background Technology

[0002] Material removal methods can be used to structure the surface of workpieces made of metal or metal alloys (e.g., steel). A specific case of surface structuring is surface roughening. For example, surface roughening is used to allow for better adhesion of coatings or to prepare the surface of a workpiece so that another component can be adhered to it. Methods known in the art for structuring, and particularly roughening, workpiece surfaces include blasting methods, in which granular or powdered abrasives are atomized onto the surface to be processed. An example of such a method is sandblasting.

[0003] Instead of particle beams, laser radiation can also be used to structure or roughen surfaces. For this purpose, a pulsed laser beam focused on the surface of the workpiece is used. This pulsed laser beam intensely heats the material of the workpiece locally and transforms the material into a molten phase. This results in roughening of the irradiated surface.

[0004] The technical challenge lies in roughening the surface of the workpiece on the inner surface of a cavity arranged in a recess or as part of the workpiece's interior, open on one side. Figure 1 An example of such a workpiece 1 is schematically shown in longitudinal cross-section. This is a component of a vibration sensor used to detect measured variables of a medium, such as fill level or limit level, viscosity, or density. The vibration sensor has an oscillating fork. Workpiece 1 includes an oscillating fork having two oscillating elements 2, such as two metal rods or tips, symmetrically arranged on a membrane 3 made of metal. The disc-shaped membrane 3 is held in a tubular housing (also referred to as a tubular extension) 4 such that the membrane 3 closes the housing 4 on one side.

[0005] For measurement, the oscillating element 2 is oscillated, and the measured variable is detected in a known manner based on changes in the resonant frequency and / or oscillation amplitude. An electromechanical transducer unit is used to excite the oscillation. This electromechanical transducer unit is attached to the back side of the membrane 3 during manufacturing. To improve adhesion, the back side of the membrane 3 (i.e., the back side 5 facing the interior of the housing 4) is first cleaned and roughened. For this purpose, one of the aforementioned spraying methods is typically used.

[0006] In fact, satisfactory results can be obtained during roughening through blasting methods, especially sandblasting. However, a disadvantage in this case is that after the sandblasting process, it is necessary to... Figure 1The workpiece 1 shown is thoroughly cleaned to remove (e.g., by blowing out with compressed air) any particles remaining in the housing 4 and on the back side of the membrane before the electromechanical transducer unit can be bonded to the back side of the membrane. This requires manual processing steps and makes automating the manufacturing process difficult or impossible.

[0007] It is conceivable that the roughening of the back side of the membrane could be achieved by using laser structuring instead of sandblasting. However, even during laser processing of the workpiece, soot, fumes, and undesirable particles can form, adhering to the workpiece or remaining in the chamber surrounded by the housing. To avoid and / or remove such particles, suction devices or inert gas nozzles for cleaning are used in the prior art. For example, variable position gas nozzles are known to be used in laser welding processes.

[0008] DE 10 2006 040 784 A1 discloses a laser beam processing machine for laser processing workpieces, the machine having a dust discharge device for collecting and discharging dust generated due to the application of a laser beam to the workpiece. The dust discharge device includes an air inlet chamber and a dust collection chamber, as well as an air supply device for supplying air to the air inlet chamber. Furthermore, the dust discharge device includes a vortex generating device for generating vortices or flows in the dust collection chamber. A cover member mounted at the lower end of a condenser for applying the laser beam to the workpiece surrounds the air inlet chamber and the dust collection chamber.

[0009] Such devices, known from the prior art, can be used to remove and / or extract particles generated during laser processing on flat surfaces; however, such devices are not well-suited for use on surfaces arranged within the cavity of a workpiece (such as, for example...). Figure 1 Laser structuring of the back side of the membrane 3 of workpiece 1 (as shown) is problematic because conventional gas nozzles or suction devices arranged in the area of ​​the laser optics cannot be brought close enough to the surface to be structured, and / or the large gas nozzles block the laser radiation used for processing the back side of the membrane. Therefore, in processing such workpieces, not all contaminants and interfering particles can be reliably prevented or removed using conventional methods during laser processing. Summary of the Invention

[0010] The object of the present invention is to provide an apparatus and method that allows for improved gas cleaning during laser processing of a workpiece having a surface to be processed, the surface to be processed being arranged in a cavity open on at least one side of the workpiece.

[0011] The cleaning attachment for a workpiece according to the invention comprises: a chamber open on at least one side of the workpiece; and a surface disposed within the chamber and to be processed by laser radiation.

[0012] The cleaning accessories include:

[0013] Passing through the central opening at the end of the rinse;

[0014] At least one cleaning gas supply channel extends through the cleaning accessory and has a connector for a cleaning gas supply line at a first end and an outlet opening at a second end;

[0015] At least one cleaning gas suction channel extends through the cleaning accessory and has a connector at a first end for a cleaning gas discharge line and an inlet opening at a second end, wherein the outlet opening of the at least one cleaning gas supply channel and the inlet opening of the at least one cleaning gas suction channel are arranged on opposite sides of the central opening; and

[0016] At least one centering portion is configured to interact with a centering region disposed on the side of the workpiece, such that the central opening, the outlet opening, and the inlet opening communicate with the chamber.

[0017] By arranging at least one or more cleaning gas supply channels with cleaning gas outlet openings and at least one or more cleaning gas suction channels with cleaning gas inlet openings in a cleaning attachment that can be placed on a workpiece, wherein when the cleaning attachment is placed on the workpiece, the cleaning gas inlet openings communicate with the chambers within the workpiece, allowing cleaning gas to be introduced into and / or drawn out of the chambers without obstruction of the cleaning gas flow by the workpiece walls. The inlet and outlet openings can also be arranged such that the accumulation of unwanted particles and contaminants is prevented even in areas where edges are formed between the inner walls of the chambers. Simultaneously, the structure is compact and allows laser radiation for surface processing to pass through the central opening without obstructing the laser beam from the cleaning nozzles or suction nozzles.

[0018] In an advantageous embodiment, the outlet opening of the at least one cleaning gas supply channel and the inlet opening of the at least one cleaning gas suction channel can be configured as elongated orifices.

[0019] The at least one cleaning gas supply channel may include a chamber formed within the cleaning accessory and communicating with a connector for a cleaning gas supply line and with the outlet opening. Similarly, the at least one cleaning gas suction channel may include a chamber formed within the cleaning accessory and communicating with a connector for a cleaning gas discharge line and with the outlet opening.

[0020] In another particularly advantageous embodiment, the cleaning accessory has two cleaning gas supply channels extending through the cleaning accessory and two cleaning gas suction channels extending through the cleaning accessory, wherein each of the cleaning gas supply channels has a connector for a cleaning gas supply line at a first end and an outlet opening at a second end, wherein each of the cleaning gas suction channels has a connector for a cleaning gas discharge line at a first end and an inlet opening at a second end, and wherein in each case, the cleaning gas suction channels and the cleaning gas supply channels are arranged on opposite sides of the central opening, i.e., the inlet opening and the outlet opening are opposite each other, such that the central opening of the cleaning accessory is arranged between the inlet opening and the outlet opening.

[0021] In this embodiment, the cleaning accessory may have, for example, four chambers of equal size, separated by partitions. These chambers may be arranged annularly around the central opening. Two of these chambers each form components of a cleaning gas supply channel, and in this embodiment, each of these two chambers communicates with a connector for the cleaning gas supply line and with an outlet opening. The other two chambers each form components of a cleaning gas suction channel, and in this embodiment, each of these other two chambers communicates with a connector for the cleaning gas discharge line and with an inlet opening. In each case, these chambers may communicate with either the outlet opening or the inlet opening, wherein in each case, the outlet opening and the inlet opening are arranged on opposite sides of the central opening.

[0022] Connectors for the cleaning gas supply channel of a cleaning gas supply line may include a compressed air adapter. Connectors for the cleaning gas suction channel may also include a compressed air adapter. The compressed air adapter can be used to optionally supply gas overpressure to the channel, such as supplying air, or supplying an inert protective gas (such as argon or nitrogen), or optionally, to supply negative pressure for suctioning the gas. Therefore, if the channel is subjected to gas overpressure, it is a cleaning gas supply channel, and if the channel is subjected to negative pressure, it is a cleaning gas suction channel.

[0023] Advantageously, the cleaning attachment can be annular, i.e., cylindrically symmetrical about a longitudinal axis or cylindrical axis extending perpendicular to the central opening. In this embodiment, the cleaning attachment may include four identical, annularly segmented chambers, each of which communicates with an inlet or outlet opening. In this embodiment, the inlet and outlet openings are advantageously designed as elongated holes, the cross-section of which is substantially annularly segmented. The arcs of the annularly segmented shapes of the chambers and elongated holes can be arranged concentric with the cylindrical axis of the central opening. Thus, in this embodiment, imaginary annexes extending through the cross-sections of all elongated holes can be concentric with the central opening. Similarly, imaginary annexes extending through the annularly segmented chambers in a plane perpendicular to the cylindrical axis of the central opening can be concentric with the central opening. This embodiment of the cleaning attachment is advantageous for machining the inner surface of the cylindrical housing chambers of the workpiece.

[0024] In one possible embodiment, the centering portion of the cleaning attachment may have a cylindrical surface extending about the longitudinal axis of the central opening and designed to abut against a contact surface of the workpiece to center the workpiece relative to the central opening of the cleaning attachment. In this embodiment, the contact surface corresponds to the aforementioned centering region of the workpiece.

[0025] The central opening of the cleaning attachment may have a first cylindrical symmetrical portion (which has a first cross-section) and a second cylindrical symmetrical portion, the second cylindrical symmetrical portion being coaxially arranged behind the first cylindrical symmetrical portion and having a second cross-section, wherein a radial shoulder is formed at the transition from the first portion to the second portion, the radial shoulder forming a stop surface for the workpiece when the cleaning attachment is placed on the workpiece.

[0026] In this embodiment, the outlet openings of all cleaning gas supply channels and the inlet openings of all cleaning gas suction channels can be arranged in the radial shoulder. In this way, the outlet and inlet openings are arranged in a space-saving manner, such that when the cleaning attachment is placed on the workpiece, the fluid flow formed between the outlet and inlet openings flows through the workpiece's chamber.

[0027] The method according to the present invention for processing, and particularly structuring, the surface of a workpiece by laser includes the following steps:

[0028] - A cleaning attachment according to one of the above embodiments is placed on the workpiece, wherein the workpiece has a chamber that is open on at least one first side of the workpiece, such that the centering portion of the cleaning attachment interacts with the centering region of the workpiece arranged on the first side of the workpiece, such that the central opening of the cleaning attachment, the outlet opening of the at least one cleaning gas supply channel of the cleaning attachment, and the inlet opening of the at least one cleaning gas suction channel of the cleaning attachment communicate with the chamber;

[0029] - Gas is supplied to the chamber through the outlet opening of the at least one cleaning gas supply channel, and gas is drawn in through the inlet opening of the at least one cleaning gas suction channel; and

[0030] - During the supply of gas into the chamber and during the suction of gas, laser radiation is irradiated onto the surface of the workpiece disposed in the chamber through the central opening of the cleaning attachment, and the surface of the workpiece is processed using the laser radiation.

[0031] The method according to the invention is particularly suitable for use on workpieces (such as...) Figure 1 The workpiece shown is processed to manufacture a sensor for determining process variables (e.g., the filling level or limit level of a medium in a container) or for determining the density or viscosity of a medium.

[0032] Therefore, a method for producing a sensor for determining at least one process variable of a medium in a container may include the following steps:

[0033] - The back side surface of the membrane of the oscillable unit is roughened by the method described above, the oscillable unit having at least the membrane and at least one oscillating element, the at least one oscillating element being arranged on the front side surface of the membrane, the front side surface being opposite to the back side surface of the membrane;

[0034] - A control and receiving unit is attached to the roughened back surface of the membrane, wherein the control and receiving unit is designed to excite the mechanically oscillable unit to oscillate in an oscillation mode corresponding to the excitation frequency by an electrical excitation signal having an excitation frequency, and the control and receiving unit is designed to receive mechanical oscillations from the oscillable unit and convert the mechanical oscillations into an electrical receiving signal; and

[0035] - Connect the control and receiving unit to the electronic device unit such that the electronic device unit and the control and receiving unit interact to generate the excitation signal starting from the received signal and to determine the process variable based on the received signal. Attached Figure Description

[0036] In the following explanation, the invention will be based on exemplary embodiments shown in the figures. The same reference numerals refer to the same parts shown in the figures. In these figures:

[0037] Figure 1 This is a schematic longitudinal section of a workpiece having the following surface, which will be processed by laser radiation and is arranged in a cavity open on one side;

[0038] Figure 2 It is used to treat by laser radiation Figure 1 The diagram shows a schematic longitudinal cross-sectional view of the workpiece surface being machined and the arrangement for simultaneously suctioning particles and contaminants using a cleaning attachment; and

[0039] Figure 3 yes Figure 2 A schematic cross-section of the cleaning attachment shown. Detailed Implementation

[0040] As described in the introduction Figure 1 As shown, based on the processing of the back side of a membrane in a method for producing a component for a sensor, the following describes laser processing for roughening the surface of a cavity located in a workpiece. However, the invention can also be applied to multiple other workpieces having surfaces to be processed arranged in recesses or cavities open to at least one side.

[0041] Figure 2 The diagram illustrates the method for making Figure 1 The laser-structured arrangement of the back side of the film 3 of the workpiece 1 is shown. A cleaning attachment 5 with a central opening 6 is placed on the open side of the workpiece housing 4. The cleaning attachment 5 is substantially annular, that is, it has cylindrical symmetry about an imaginary cylindrical axis of symmetry or cylindrical axis Z. Laser radiation from the laser optics 7 of the laser processing machine (illustrated only) can pass through the central opening 6 to reach the surface 8 of the film 3 to be processed, so as to structure or roughen the surface.

[0042] To clean the chamber 10 surrounded by the workpiece 1 using an inert gas (e.g., argon or nitrogen), the cleaning accessory 5 in each case has two cleaning gas supply channels 11 and two cleaning gas suction channels 12. In principle, a higher number of cleaning gas supply channels and cleaning gas suction channels is also possible, but it has been shown that, in each case, the number of two cleaning gas supply channels and two cleaning gas suction channels is particularly suitable for the specific geometry of the workpiece 1 used in the example described herein.

[0043] exist Figure 2In the longitudinal section, only one cleaning gas supply channel 11 and one cleaning gas suction channel 12 are visible, arranged on opposite sides of the central opening 6. The cleaning gas supply channel 11 has a connector 13 in the form of a compressed air adapter at its first end. The cleaning gas supply channel 11 has an outlet opening 14 at its second end leading to the chamber 10. Furthermore, the cleaning gas supply channel 11 has a chamber 15 communicating with the connector 13 and the outlet opening 14. The shape and function of the chamber 15 and the outlet opening 14 will be discussed below. Figure 3 Further detailed discussion is needed.

[0044] In terms of geometry, the cleaning gas suction channel 12 is designed to be identical to the cleaning gas supply channel 11. The cleaning gas suction channel 12 also has a connector 16 at its first end, which can be designed as a compressed air adapter. The cleaning gas suction channel 12 has an inlet opening 17 at its second end. Furthermore, the cleaning gas suction channel 12 includes a chamber 18 communicating with the connector 16 and the inlet opening 17.

[0045] The central opening 6 of the cleaning attachment 5 has a first portion and an adjacent second portion, wherein the first portion has a first diameter and the adjacent second portion has a second diameter, wherein the second diameter is larger than the first diameter. At the transition from the first portion to the second portion, as a result of the abrupt widening of the central opening 6 from the first diameter to the second diameter, a radial shoulder 9 is formed, which has an annular surface facing the surface 8 to be processed. When the cleaning attachment 5 is placed on the workpiece 1, the annular surface serves as a stop surface on the back side of the housing 4 of the workpiece 1.

[0046] The second diameter of the central opening 6 in its second portion is adapted to the outer diameter of the cylindrical housing 4, such that when the cleaning attachment 5 is placed on the housing 4, the outer wall of the housing 4 abuts against the cylindrical wall of the cleaning attachment 5 surrounding the central opening 6. In this way, the second portion of the central opening 6 forms a centering portion for centering the workpiece 1 relative to the cylindrical axis Z of the cleaning attachment 5, such that the cylindrical axis of symmetry of the tubular housing 4 coincides with the cylindrical axis Z.

[0047] The outlet opening 14 of the cleaning gas supply channel 11 and the inlet opening 17 of the cleaning gas suction channel 12 are arranged in the radial shoulder 9, specifically in the region of the annular surface of the radial shoulder 9, such that when the workpiece 1 is received in the second part of the central opening 6, which serves as the centering portion of the cleaning attachment 5, this region is not covered by the wall of the housing 4, so that the inlet opening 14 and the outlet opening 17 communicate with the chamber 10, which is surrounded by the housing 4 and open toward the cleaning attachment 5. For this purpose, all the inlet openings 14 and the outlet openings 17 are arranged at a distance from the cylindrical inner wall of the second part of the central opening 6, such that the workpiece 1 is received therein, the distance being greater than the wall thickness of the hollow cylindrical housing portion. By centering the workpiece 1 relative to the central opening 6 using the centering portion of the cleaning attachment 5, such that the cylindrical axis of the tubular housing 4 coincides with the cylindrical axis of the central opening 6, the inlet and outlet openings of the cleaning attachment 5 are also arranged such that they inevitably lead into the chamber 10 and are not covered by the housing wall of the housing 4.

[0048] The cleaning gas supply channel 11 is used to inject cleaning gas into the chamber 10. For this purpose, a connector 13 can be connected to a cleaning gas source (e.g., a compressed air line or gas cylinder), and the connector 13 can be pressurized with an inert gas. Figure 2 In the diagram, arrow 18 indicates the direction of gas flow into chamber 10. The corresponding purge gas suction channel 12 is used to extract gas from chamber 10, as shown below. Figure 2 As indicated by arrow 20. For this purpose, a vacuum can be applied to connector 16, for example, by means of a pump. The blowing in and extraction of cleaning gas can be performed alternately and / or simultaneously. Advantageously, the blowing in and extraction of cleaning gas can be performed simultaneously with the processing of surface 8 by laser.

[0049] Figure 3 A cross-section perpendicular to axis Z is shown, passing through the cleaning attachment 5 at the heights of chambers 15 and 18. Two cleaning gas supply channels 11 and two cleaning gas suction channels 12 are visible, with one cleaning gas supply channel 11 and one cleaning gas suction channel 12 opposite to each other. Each cleaning gas supply channel 11 has a connector at its first end for a cleaning gas supply line. Figure 3 (Not shown in the image). Therefore, each cleaning gas suction channel 12 also has a connector for the cleaning gas discharge line (also in the image). Figure 3(Not shown in the image). Each of the cleaning gas supply channel 11 and the cleaning gas suction channel 12 includes annular segmented chambers 15 and 18, respectively. Chambers 15 and 18 are separated from each other by partitions and arranged annularly around the central opening 6 of the cleaning attachment 5. Each chamber 15 and 18 has an elongated hole at the bottom of its second portion facing the central opening 6 (which serves as the centering portion of the workpiece), the elongated hole having an annular segmented cross-section. These elongated holes form the outlet opening 14 of the cleaning gas supply channel 11 and the inlet opening 17 of the cleaning gas suction channel 12. These elongated holes are arranged along an imaginary circular line 21, the center point of which lies on the cylindrical axis Z of the central opening 6 of the cleaning attachment 5. These elongated holes are arranged as shown in the image. Figure 3 In the radial shoulder 9 shown by the dashed line, the radial shoulder 9 is formed by widening the stepped cross section of the central opening 6 between its first and second portions.

[0050] Experiments have shown that the annular segmented shape of chambers 15 and 18, and the construction of the inlet opening 14 and outlet opening 17 in the form of elongated orifices, result in a cleaning airflow that is particularly beneficial to the cleaning effect of chamber 10 (and especially the back surface 8 of membrane 3). In this arrangement, the inflowing gas ( Figure 2 (Arrow 19) flows primarily along the inner wall of the housing 4 and thus reaches the surface 8 to be processed in a directional manner. Consequently, the gas is also drawn out again in a directional manner on the opposite sides of the wall of the housing 4.

[0051] In this exemplary embodiment, the cleaning attachment 5 is formed of metal or a metal alloy, such as aluminum or stainless steel. Alternatively, it may also be formed of another material (e.g., plastic, and particularly polymers). It may consist of two parts (i.e., a base and a cover portion). Figure 3 In the middle, holes can be seen on the wall of the cleaning accessory, into which fastening devices (e.g., screws) can be inserted for such a cover part of the cleaning accessory.

[0052] To structure (e.g., roughen) the surface 8 of the back side of the film 3, pulsed laser radiation can be emitted from the laser optics 7 in a manner known per se, either along or at an acute angle to the cylindrical axis Z. Cleaning gas is supplied via the outlet opening 14 and drawn out via the inlet opening 17, simultaneously removing soot, smoldering particles, or other unwanted particles generated during radiation. This method can be particularly automated by an electronically controlled laser processing machine configured to control the supply and extraction of gas via connectors 13 and 16 of the cleaning accessory 5.

[0053] To produce a sensor for determining process variables such as the filling level, density, or viscosity of a medium in a container, the back side of the membrane of an oscillating unit can be roughened according to the described method. In addition to the membrane, the oscillating unit also has at least one oscillating element (e.g., an oscillating fork or a single oscillating rod) disposed on the front side of the membrane. A control and receiving unit can then be incorporated into the roughened back side of the membrane, wherein the control and receiving unit includes, for example, an electromechanical transducer unit, such as a piezoelectric actuator or an electromagnetic actuator. For the production of the sensor, the control and receiving unit can be further connected to an electronic unit such that the electronic unit and the control and receiving unit can interact to oscillate the oscillating unit or to receive mechanical oscillations from the oscillating unit and convert them into electrical signals.

[0054] Various further modifications of the invention described herein are conceivable. For example, the cleaning gas accessory may have a higher or lower number of cleaning gas supply channels and suction channels. The workpiece, and therefore the cleaning gas accessory, may also differ from the cylindrical symmetry of the embodiments described in detail herein.

Claims

1. A cleaning attachment (5) for a workpiece (1) having a surface (8) to be processed by laser radiation, wherein The workpiece (1) has a cavity (10) open on at least one side of the workpiece (1), and the surface (8) to be processed by laser radiation is a surface arranged within the cavity (10). The cleaning accessories include: Passing through the central opening (6) of the cleaning attachment (5); At least one cleaning gas supply channel (11) extends through the cleaning accessory (5) and has a connector (13) for the cleaning gas supply line at a first end and an outlet opening (14) at a second end; At least one cleaning gas suction channel (12) extends through the cleaning accessory (5) and has a connector (16) for a cleaning gas discharge line at a first end and an inlet opening (17) at a second end, wherein the outlet opening (14) of the at least one cleaning gas supply channel (11) and the inlet opening of the at least one cleaning gas suction channel (12) are arranged on opposite sides of the central opening (6); and At least one centering portion is configured to interact with a centering region of the workpiece (1) disposed on the side of the workpiece (1), such that the central opening (6), the outlet opening (14), and the inlet opening (17) communicate with the chamber (10). The centering portion has a cylindrical surface that extends about the longitudinal axis (Z) of the central opening (6) and is designed to abut against the contact surface of the workpiece (1) so as to center the workpiece (1) relative to the central opening (6) of the cleaning attachment (5). The central opening (6) of the cleaning attachment (5) has a first cylindrical symmetrical portion and a second cylindrical symmetrical portion, wherein the first cylindrical symmetrical portion has a first cross-section, and the second cylindrical symmetrical portion is coaxially arranged behind the first cylindrical symmetrical portion and has a second cross-section, wherein a radial shoulder (9) is formed at the transition from the first cylindrical symmetrical portion to the second cylindrical symmetrical portion, and when the cleaning attachment (5) is placed on the workpiece (1), the radial shoulder forms a stop surface for the workpiece (1). The outlet openings (14) of all cleaning gas supply channels (11) and the inlet openings (17) of all cleaning gas suction channels (12) are arranged in the radial shoulder (9). The contact surface of the workpiece corresponds to the fixed center region of the workpiece.

2. The cleaning accessory (5) according to claim 1, wherein The at least one cleaning gas supply channel (11) includes a chamber formed within the cleaning accessory and communicating with the connector (13) for the cleaning gas supply line and with the inlet opening, and wherein the at least one cleaning gas suction channel (12) includes a cleaning accessory chamber (18) formed within the cleaning accessory (5) and communicating with the connector (16) for the cleaning gas discharge line and with the outlet opening.

3. The cleaning accessory (5) according to claim 1 or 2, wherein The cleaning accessory (5) has two cleaning gas supply channels (11) extending through the cleaning accessory (5) and two cleaning gas suction channels (12) extending through the cleaning accessory (5), wherein each of the cleaning gas supply channels (11) has a connector (13) for a cleaning gas supply line at a first end and an outlet opening (14) at a second end, wherein each of the cleaning gas suction channels (12) has a connector (16) for a cleaning gas discharge line at a first end and an inlet opening (17) at a second end, and wherein in each case, the cleaning gas suction channels and the cleaning gas supply channels are arranged on opposite sides of the central opening (6).

4. A method for processing the surface (8) of a workpiece (1) by laser, Includes a cleaning attachment (5) for a workpiece (1) having a surface (8) to be processed by laser radiation. wherein The workpiece (1) has a cavity (10) open on at least one side of the workpiece (1), and the surface (8) to be processed by laser radiation is a surface arranged within the cavity (10). The cleaning accessories include: Passing through the central opening (6) of the cleaning attachment (5); At least one cleaning gas supply channel (11) extends through the cleaning accessory (5) and has a connector (13) for the cleaning gas supply line at a first end and an outlet opening (14) at a second end; At least one cleaning gas suction channel (12) extends through the cleaning accessory (5) and has a connector (16) for a cleaning gas discharge line at a first end and an inlet opening (17) at a second end, wherein the outlet opening (14) of the at least one cleaning gas supply channel (11) and the inlet opening of the at least one cleaning gas suction channel (12) are arranged on opposite sides of the central opening (6); and At least one centering portion is configured to interact with a centering region of the workpiece (1) disposed on the side of the workpiece (1), such that the central opening (6), the outlet opening (14), and the inlet opening (17) communicate with the chamber (10). The cleaning accessory is used for gas cleaning during laser processing. The method includes: - Place the cleaning attachment (5) on the workpiece (1); - Gas is supplied to the chamber (10) through the outlet opening (14) of the at least one cleaning gas supply channel (11), and gas is drawn through the inlet opening (17) of the at least one cleaning gas suction channel (12); and - During the supply of gas into the chamber (10) and during the suction of gas, laser radiation is irradiated onto the surface (8) of the workpiece (1) arranged in the chamber (10) through the central opening (6) of the cleaning attachment (5), and the surface (8) of the workpiece (1) is processed by the laser radiation.

5. The method according to claim 4, wherein, The method is a method of structuring the surface (8) of the workpiece (1).

6. The method of claim 4, wherein, The surface (8) of the workpiece (1) is roughened by the laser radiation.

7. A method for producing a sensor for determining at least one process variable of a medium in a container, the method comprising: - The back side of the membrane (3) of the mechanically oscillable unit is roughened by the method according to claim 4, the mechanically oscillable unit having at least the membrane (3) and at least one oscillating element (4), the at least one oscillating element (4) being arranged on the front side of the membrane (3), the front side being opposite to the back side of the membrane (3); - Attach a control and receiving unit to the roughened back side of the membrane (3), wherein the control and receiving unit is designed to excite the mechanically oscillable unit to oscillate in an oscillation mode corresponding to the excitation frequency by an electrical excitation signal having an excitation frequency, and the control and receiving unit is designed to receive mechanical oscillations from the oscillable unit and convert the mechanical oscillations into an electrical receiving signal. as well as - Connect the control and receiving unit to the electronic device unit such that the electronic device unit and the control and receiving unit interact to generate the excitation signal starting from the received signal and to determine the process variable based on the received signal.

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