METHOD FOR THE HYDRO-EROSIVE GRINDING OF COMPONENTS

Abstract

The invention relates to a method for the hydroerosive processing of components, in which a liquid comprising grinding particles flows over surfaces of the component (1), in a device having a channel (3) through which the liquid comprising grinding particles flows under pressure and in which the component (1) to be processed is received, and in which a valve (5), with which the flow of the liquid can be adjusted, is positioned in front of the component (1) in the flow direction, comprising the following steps: (a) closing the valve (5) in front of the component (1) and generating a predetermined pressure in the liquid comprising the grinding particles; (b) opening the valve (5) in front of the component (1) and setting up a first volumetric flow of the liquid comprising the grinding particles, which is from 5 to 80% less than the product of the minimum setpoint cross-sectional area flowed through and the maximum permissible speed at this position, without the predetermined pressure generated in step (a) being changed; (c) measuring the pressure difference which is set up between a position in front of the component (1) to be processed and a position behind the component to be processed in the liquid comprising the grinding particles; (d) increasing the volumetric flow of the liquid comprising the grinding particles until the volumetric flow corresponds to the product of the minimum setpoint cross-sectional area flowed through and the maximum permissible speed at this position, as soon as the pressure difference measured in step (c) has decreased by from 5 to 80%; (e) closing the valve (5) in front of the component (1) and terminating the flow, as soon as the volumetric flow in step (d) corresponds to the product of the minimum setpoint cross-sectional area flowed through and the maximum permissible speed at this position.

Claims

1.-14. (canceled)

15. A method for the hydroerosive processing of components, in which a liquid comprising grinding particles flows over surfaces of the component, in a device having a channel through which the liquid comprising grinding particles flows under pressure and in which the component to be processed is received, and in which a valve, with which the flow of the liquid can be adjusted, is positioned in front of the component in the flow direction, comprising the following steps: (a) closing the valve in front of the component and generating a predetermined pressure in the liquid comprising the grinding particles; (b) opening the valve in front of the component and setting up a first volumetric flow of the liquid comprising the grinding particles, which is from 5 to 80% less than the product of the minimum setpoint cross-sectional area flowed through and the maximum permissible speed at this position, without the predetermined pressure generated in step (a) being changed; (c) measuring the pressure difference which is set up between a position in front of the component to be processed and a position behind the component to be processed in the liquid comprising the grinding particles; (d) increasing the volumetric flow of the liquid comprising the grinding particles until the volumetric flow corresponds to the product of the minimum setpoint cross-sectional area flowed through and the maximum permissible speed at this position, as soon as the pressure difference measured in step (c) has decreased by from 5 to 80%; (e) closing the valve in front of the component and terminating the flow, as soon as the volumetric flow in step (d) corresponds to the product of the minimum setpoint cross-sectional area flowed through and the maximum permissible speed at this position.

16. The method according to claim 15, wherein the volumetric flow is increased continuously, constantly and monotonically increasingly in step (d).

17. The method according to claim 15, wherein the maximum permissible speed at the position of the minimum setpoint cross-sectional area flowed through lies in the range of from 1 m/s to 99% of the speed of sound.

18. The method according to claim 15, wherein the maximum permissible speed is determined by a simulation calculation.

19. The method according to claim 15, wherein the shape of the component is modeled in a simulation calculation before the grinding process.

20. The method according to claim 15, wherein, in the case of outer surfaces to be processed, the component is positioned inside the channel so that the liquid comprising grinding particles can flow over the outer surfaces.

21. The method according to claim 15, wherein, in the case of inner surfaces to be processed, the component is fitted into the channel in such a way that all of the liquid comprising grinding particles flows through the interior of the component to be processed.

22. The method according to claim 15, wherein, in order to detect cavitation, a sound sensor is positioned in the channel behind the component or at the component, and if cavitation occurs the volumetric flow is reduced until cavitation is no longer detected.

23. The method according to claim 15, wherein the liquid comprising grinding particles is provided in a storage container and flows back into the storage container after flowing over the surfaces to be processed of the component.

24. The method according to claim 23, wherein the liquid comprising grinding particles is relaxed before flowing into the storage container.

25. The method according to claim 15, wherein a second valve is positioned behind the component, and the volumetric flow and the pressure in the liquid comprising the grinding particles are adjusted by means of the first valve and the second valve.

26. The method according to claim 25, wherein, before closing the valve in front of the component in step (e), the second valve behind the component is closed as soon as the volumetric flow corresponds to the product of the minimum setpoint cross-sectional area flowed through and the maximum permissible speed at this position in step (d).

27. The method according to claim 15, wherein the pressure of the liquid comprising grinding particles is measured in step (a) with a first pressure sensor, which is positioned between the valve in front of the component and a pump, with which the pressure and the flow of the liquid comprising grinding particles are generated.

28. The method according to claim 15, wherein, in order to determine the pressure difference, the pressure is measured with a second pressure sensor, which is positioned between the valve in front of the component and the component, and a third pressure sensor, which is positioned behind the component.

Description

[0065] The single FIGURE shows a method flow diagram of the method according to the invention.

[0066] For the processing by a hydroerosive grinding method, a component 1 is introduced into a channel 3 through which a liquid comprising grinding particles flows. The positioning of the component 1 is in this case dependent on the surface to be processed. If outer surfaces on the component are intended to be processed, the component 1 is introduced into the channel 3 so that the liquid comprising grinding particles can flow over the outer surfaces to be processed. To this end, the channel 3 is enclosed by a wall on all sides and the component 1 is located inside the channel. The component 1 is then fixed in the channel 3 with suitable fastening means, for example rods. If inner surfaces, for example of bores or channels in the component 1, are intended to be processed, the channel 3 is connected to the component so that the liquid comprising the grinding particles can flow over the inner surfaces of the component 1. To this end, for example, the channel 3 may be connected with a suitable coupling directly to the opening, for example the bore or the channel in the component 1.

[0067] In order to be able to adjust the flow of the liquid comprising the grinding particles, there is a first valve 5 in the flow direction of the liquid comprising the grinding particles. Initially, the first valve 5 is closed. Then, with a pump 7, preferably a diaphragm pump, the pressure is increased in the liquid comprising the grinding particles in the channel 3 between the pump 7 and the first valve 5. The pressure, which is adjusted using the pump 7 with the first valve 5 closed, is dependent on the material of the component to be processed. If the surface to be processed of the component 1 is made of a metal or a ceramic, a pressure in the range of from 10 to 500 bar(abs), more preferably from 10 to 200 bar(abs), and in particular from 50 to 150 bar(abs) is preferably built up, and in the case of a surface to be processed of the component 1 made of a plastic, a pressure in the range of from 1.1 to 100 bar(abs), more preferably in the range of from 1.5 to 10 bar(abs), and particularly in the range of from 1.5 to 3 bar(abs). The pressure which is built up using the pump 7 with the first valve 5 closed is in this case measured with a first pressure sensor 9.

[0068] After the pressure buildup, the first valve 5 is initially opened partially. Preferably, the first valve 5 is opened to from 5 to 80%, more preferably from 10 to 40%, in particular from 15 to 25%, for example 20%, of the maximum cross-sectional area flowed through in the valve. Subsequently, a second valve 11, which is arranged behind the component 1 to be processed in the flow direction of the liquid comprising the grinding particles, is opened, the second valve 11 being opened only wide enough for the pressure generated by the pump 7 and measured at the first pressure sensor 9 to be maintained, and for a desired volumetric flow of the liquid comprising the grinding particles to be set up. The volumetric flow is in this case measured with a suitable sensor 13, for example a through-flow sensor. The volumetric flow, which is set up with the first valve 5 and the second valve 11, is in this case preferably from 5 to 80%, more preferably from 10 to 40%, and in particular from 15 to 15%, for example 20%, of the product of the minimum setpoint cross-sectional area flowed through and the maximum permissible speed at this position.

[0069] While the liquid comprising the grinding particles is flowing over the surface to be processed, the pressure difference in the liquid comprising the grinding particles is detected. To this end, in the embodiment shown here, a second pressure sensor 15 is arranged in front of the component and a third pressure sensor 17 is arranged behind the component. The second pressure sensor 15 is in this case preferably located, as represented here, between the first valve 5 and the component 1 and the third pressure sensor 17 between the component 1 and the second valve 11. In order to determine the pressure difference, the pressure measured at the third pressure sensor 17 is subtracted from the pressure measured at the second pressure sensor 15.

[0070] Edges and corners in the component are rounded by the hydroerosive grinding. Furthermore, the cross-sectional area flowed through is increased. These modifications on the component lead to a reduction in the pressure difference for a constant volumetric flow.

[0071] As soon as the pressure difference detected between the second pressure sensor 15 and the third pressure sensor 17 is decreased by from 5 to 80%, preferably from 10 to 30%, in particular from 15 to 25%, for example 20%, the volumetric flow of the liquid comprising the grinding particles is increased. The increase in the volumetric flow is in this case preferably carried out continuously, constantly and monotonically increasingly until the volumetric flow corresponds to the product of the minimum setpoint cross-sectional area flowed through in the component and the maximum permissible speed. As soon as this value is reached, the flow of the liquid comprising the grinding particles is terminated, the pump is turned off, and first the second valve 11 and then the first valve 5 are closed.

[0072] In order to prevent cavitation during the grinding process, which may lead to undesired material erosion and therefore damage to the component, a sound sensor 19 is preferably provided.

[0073] With the sound sensor, undesired sounds in the flowing liquid comprising the grinding particles, in particular noise or rattling produced as a result of implosion of the vapor bubbles formed by cavitation may be detected. As soon as sounds detected with the sound sensor indicate cavitation setting in, the volumetric flow is reduced so that the susceptibility to cavitation is also reduced. In this way, the hydroerosive grinding method can be operated in such a way that no cavitation, and therefore no undesired material erosion, occurs.

[0074] The liquid comprising the grinding particles is preferably taken from a storage container 21 during the hydroerosive grinding process. The storage container 21 may in this case be equipped with a stirrer in order to prevent agglomeration and sedimentation of the grinding particles.

[0075] After flowing through the component, the liquid comprising the grinding particles is preferably fed back through a return line 23 into the storage container 21. Before entering the storage container, the liquid comprising the grinding particles is relaxed in a relaxation member 25. For example, a throttle or a valve is suitable as the relaxation member 25. As an alternative, in order to relax the liquid comprising the grinding particles and reduce the speed, it is possible to increase the flow cross section of the return line 23. If a controllable or regulatable relaxation member 25 is used, it is advantageous to measure the pressure in the liquid comprising the grinding particles with a fourth pressure sensor 27, and to control and/or regulate the relaxation member 25 with the at the fourth pressure sensor 27, so as to introduce the liquid comprising grinding particles with a flow rate and/or with a pressure which varies within the limits specified for the control and/or regulation into the storage container 21.

[0076] Since the liquid comprising the grinding particles flushes and entrains the material, eroded during the hydroerosive processing, of the component 1, the liquid comprising the grinding particles is contaminated by the eroded material. In order to be able to use the liquid comprising the grinding particles over a longer period of time, it is then possible to remove the eroded material by a suitable separating method from the liquid comprising the grinding particles. To this end, either a suitable separating device may be provided in the return line 23, or a part of the liquid comprising the grinding particles is removed either from the storage container 21 or from the return line 23 and sent to treatment in which the eroded material is removed from the liquid comprising the grinding particles. The liquid comprising the grinding particles which has been treated in this way can then be returned to the storage container.

[0077] As an alternative, continuously or at regular intervals which are either dependent on the proportion of the eroded material in the liquid comprising the grinding particles or selected to be constant, it is also possible to remove a part of the liquid from the method and replace it with fresh liquid comprising grinding particles. Furthermore, it is also possible to determine the proportion of the eroded material by continuous tests or tests at regular predetermined intervals, and when reaching a predetermined maximum proportion of eroded material, to replace all of the liquid comprising grinding particles with fresh liquid comprising grinding particles.

[0078] Besides the embodiment presented here, with recycled liquid comprising grinding particles, it is as an alternative of course also possible always to carry out the hydroerosive grinding with fresh liquid comprising grinding particles, and to remove from the process, dispose of or treat, the liquid comprising grinding particles after flowing over the surfaces to be processed.

LIST OF REFERENCES

[0079] 1 component [0080] 3 channel [0081] 5 first valve [0082] 7 pump [0083] 9 first pressure sensor [0084] 11 second valve [0085] 13 sensor for measuring the volumetric flow [0086] 15 second pressure sensor [0087] 17 third pressure sensor [0088] 19 sound sensor [0089] 21 storage container [0090] 23 return line [0091] 25 relaxation member [0092] 27 fourth pressure sensor