EP3180163B1 - Jet cutting device and jet cutting method - Google Patents

Description

The invention relates to a beam cutting device for separating materials by means of a cutting beam according to the features of claim 1 and a corresponding beam cutting method according to claim 9.

In general, the invention relates to the field of separating materials by means of a cutting jet in the form of a liquid jet. For example, water jet cutting is known. To increase the cutting performance, an abrasive can be added to the water, for example garnet or corundum. In many cases, however, the remaining particles of the abrasive are disruptive. This can be counteracted by collecting the abrasives present in the cutting jet, but this again increases the effort. In addition, the residual kinetic energy of the cutting beam and in particular of the abrasive that is still present after the impact on the workpiece must be absorbed in a suitable manner. There are therefore already proposals to use self-dissolving abrasive materials, such as ice particles. So reveals the DD 298 618 A5 a method for cutting with high pressure water ice crystal jet. The DE 197 56 506 A1 discloses a method for abrasive water jet cutting in which dry ice is used as the abrasive. Here, too, the water used as the cutting medium is disruptive in many cases, since it has to be disposed of after the cutting process. From the publications DE 101 60 275 A1 and JP H006 329398 A suggests using liquefied nitrogen to which solidified carbon dioxide particles are added for jet cutting. The EP 2 583 790 A1 describes a jet cutting device with an overpressure chamber that encloses the cutting jet of the device from the nozzle outlet to the workpiece and influences it thermodynamically or fluidically.This jet cutting device has a cutting head that can be set up to discharge the cutting jet onto the material to be cut. The cutting head has a supply connection which is connected to a supply line which guides the cutting medium so that the supply connection can supply the cutting medium to the cutting head. The cutting medium consists of carbon dioxide in partly liquid and partly solid form.

The invention is therefore based on the object of specifying a beam cutting device and a beam cutting method with which residue-free beam cutting can be carried out.

This object is achieved by a beam cutting device according to claim 1. A mixture of the cutting medium and the abrasive is then emitted from the cutting head as a cutting jet. The invention has the advantage that a gas is used both for the liquid cutting medium and for the abrasive, i.e. a substance or mixture of substances which, by definition, is in a gaseous state under standard conditions (temperature 20 ° C., pressure 1 bar). The jet cutting device can therefore be used to cut with high cutting power without leaving any residues of the cutting medium or the abrasive. These evaporate into the gaseous phase after the cutting process and therefore do not have to be disposed of with technical effort. The abrasive can be supplied in the form of particles, i.e. as abrasive particles.

Another advantage of the invention is that the use of gaseous media for both the abrasive and the cutting medium results in a particularly pronounced cooling effect at the cutting point. In this way, undesired heating of the materials to be separated can be counteracted particularly effectively.

An additional increase in cutting performance compared to classic water abrasive jet cutting processes is achieved in the invention in that the substances contained in the cutting jet are at a low temperature level when they exit the cutting head and cause additional cooling by changing to the gaseous state of aggregation. In this way, a temperature difference between the media of the cutting beam and the materials to be cut can cause embrittlement or thermal stress in certain materials, which can also be used to promote removal.

The invention is particularly suitable for mobile applications, for example for cutting CFRP connections and for use in bio-medical technology.

Another advantage is that the solid abrasive particles are thermally stabilized by the gas liquefied by cooling, which is used as the cutting medium.

It is particularly advantageous to use a gas with a so-called triple point. Such gases have the property that, under certain conditions with regard to pressure and temperature, they can be in liquid as well as in solid form and can be mixed with one another accordingly.

It is advantageous here to use such a gas or gases that are harmless to humans and the environment, for example gas components that are already present in the ambient air. According to the invention, the same gas is used for the cutting medium and the abrasive, that is, the cutting medium and the abrasive form the same gas in the gaseous state. The use of non-flammable gases is particularly advantageous. In particular, carbon dioxide is suitable for forming the liquid cutting medium and / or the abrasive. Carbon dioxide has the advantage that it is of relatively little technical nature Effort can be produced in liquid and solid form. The temperatures required for this are still in a range that can be controlled with justifiable technical effort. Another advantage is that the carbon dioxide is non-flammable and also has a flame-retardant effect.

The liquid cutting medium can for example be provided in a storage container, for example in a so-called riser bottle, or it can be produced on site in the area of the jet cutting device by a gas liquefaction device. Accordingly, the first supply line is connected either to the storage container or to the gas liquefaction device.

The abrasive can also be kept ready in a separate additional storage container provided for this purpose, or it can be produced on site in the area of the jet cutting device by a gas solidifying device. The second supply line is correspondingly connected to the further storage container or the gas solidification device.

It is advantageous here to design the first and the second supply line with good thermal insulation and, if necessary, with temperature control. The same applies to the storage containers for the cutting medium and the abrasive or the gas solidification device and the gas liquefaction device.

According to an advantageous development of the invention, the jet cutting device, in particular its cutting head, has an expansion chamber in which the abrasive is mixed with the liquid cutting medium. According to a further advantageous development, the jet cutting device has at least one first transition point, which is narrowed with regard to the passage cross section, through which the liquid Cutting medium is guided from the first supply connection into the expansion chamber. In this way, the liquid cutting medium can be supplied under high pressure via the first supply connection to the cutting head and expanded to a pressure level at which mixing with the abrasive can be carried out. In this sense, the expansion chamber is also a mixing chamber in which the mixture of liquid cutting medium and abrasive is provided.

By using a liquid cutting medium that transports the abrasive particles, improved cutting conditions and thus a higher cutting performance can be achieved compared to a gaseous transport medium. In particular, larger, sharp-edged abrasive particles can also be transported and optimally accelerated through the liquid cutting medium. In this way, the abrasive particles hit the materials to be cut at a high impact speed. The ability to use larger, sharp-edged abrasive particles can further increase the cutting performance.

As a result of the possible increase in the size of the abrasive particles compared to the prior art, these abrasive particles achieve greater kinetic energy when the cutting beam emerges, whereby the cutting performance can also be increased.

It is possible to use relatively sharp-edged, yet large particles of the abrasive, since any turbulence that may arise is almost evened out by the liquid flow of the cutting medium and the cutting performance can be increased as a result. When using dry ice as an abrasive, a Mohs hardness of 3 can be achieved, which enables a high cutting performance of the jet cutting device. In this way, even for applications in which no fluid or particle disposal can be carried out due to the design, with the Beam cutting device according to the invention, a cutting process can also be carried out on difficult-to-cut materials with high cutting performance.

The abrasive particles can already be provided in the storage container or by the gas solidification device in the desired size and sharp-edged outer shape. It is also possible to initially have the abrasive ready in larger pieces or in one or a few larger blocks and then to convert it into the desired particles of a certain size and sharpness via a comminution device. A crusher, for example, can be used as the comminuting device.

According to an advantageous development of the invention, the expansion chamber has, on an exit side for the abrasive mixed with the cutting medium, a second transition point, narrowed with regard to the passage cross-section, into an exit pipe of the cutting head. This has the advantage that leaving the cooled environment and the positive pressure difference between the expansion chamber and the environment creates an additional nozzle effect so that the flow of liquid and solid cutting material, possibly with a pressurized gas, emerges at an accelerated rate at the end of the outlet pipe. The exit tube also serves to focus the exiting cutting beam and can therefore also be referred to as a focusing tube.

According to an advantageous development of the invention, the cutting head has at least one temperature-controlled chamber. At least the expansion chamber can thus be arranged within the temperature-controlled chamber. This has the advantage that it can be ensured by means of the temperature control that neither the cutting medium nor the abrasive change their physical state prematurely. The cutting medium is thereby kept liquid, the abrasive is kept in solid form.

According to an advantageous development of the invention, the jet cutting device has at least one third supply connection for supplying a pressurized gaseous medium, which is connected to a pressurized gas supply and / or a pressurized gas generator, the expansion chamber and / or the second supply line with the third within the beam cutting device Feed port is connected. Such pressurized gas can be used to set and maintain a desired pressure in the expansion chamber. In particular, the abrasive can be subjected to the same pressure as the compressed gas. Due to the same pressures in the abrasive and in the expansion chamber, the flow caused by the pressure drop in the expansion chamber as a result of the exiting cutting jet and the flowing cutting medium generates a fluid flow that entrains the abrasive particles supplied via the second supply line. Compressed air, in particular, can be used as the compressed gas.

According to an advantageous development of the invention, it is provided that the cutting head or an outlet pipe of the cutting head has a fourth supply connection, arranged downstream of the first and / or the second supply connection, for supplying a pressurized gaseous medium, which is directly or via a first pressure reducer with a pressurized gas supply and / or a compressed gas generator is connected. Such a fourth supply connection can be used to set a defined, preferably low pressure gradient in the cutting head or the outlet pipe in the area in which the liquid cutting medium with the abrasive is to be accelerated in a movement that is as homogeneous as possible. In particular, a relatively small pressure difference between the first or second supply connection and the fourth supply connection can ensure that the liquid cutting medium still remains in the liquid phase, so that the liquid cutting medium can be accelerated together with the abrasive in a defined manner without turbulence caused by gas bubbles.

According to an advantageous development of the invention, it is provided that the cutting head or an outlet pipe of the cutting head has a fifth supply connection, which is arranged downstream of the fourth supply connection, for supplying a gaseous medium under excess pressure, which is directly or via a second pressure reducer with a pressurized gas supply and / or a pressurized gas generator connected is. This has the advantage that the cutting medium, which is kept in the liquid state up to the fourth supply connection, can be converted into the gaseous phase in a defined manner at a point between the fourth and the fifth supply connection by selecting a suitable pressure difference between the fourth and the fifth supply connection.

The object mentioned at the beginning is also achieved by a beam cutting method according to claim 9. The aforementioned advantages of the invention can also be realized by such a method.

The method is carried out by means of a beam cutting device of the type described above.

According to an advantageous development of the invention, the liquid cutting medium is guided under high pressure through a feed pipe to a nozzle of a cutting head, in particular the cutting head of the Jet cutting device of the type described above. Here, a liquid cutting jet is generated which, in order to lower the pressure, is guided into an expansion chamber in which the abrasive is mixed with the liquid cutting medium. Here, the expansion chamber can be exposed to a gaseous medium under excess pressure, for example compressed air.

According to an advantageous development of the invention, at least the expansion chamber is temperature-regulated in such a way that the liquid cutting medium and the solid abrasive do not change their physical state directly, at least in the expansion chamber.

According to an advantageous development of the invention, it is provided that in the cutting head or in an outlet pipe of the cutting head downstream of the expansion chamber a relative negative pressure is generated compared to the pressure in the expansion chamber, by which the liquid cutting medium with the added abrasive is accelerated without changing the phase state. This has the advantage that the liquid cutting medium can initially be accelerated homogeneously with the abrasive without the occurrence of disruptive influences due to a phase transition of the liquid cutting medium into the gaseous phase.

The invention is explained in more detail below on the basis of an exemplary embodiment using drawings.

Show it:

Figure 1

- a schematic representation of a beam cutting device

and Figure 2

- Details of the beam cutting device according to Figure 1 in the area of the cutting head and

Figure 3

- a phase transition diagram for carbon dioxide.

Figure 4

- Another embodiment of the beam cutting device in detail.

In the figures, the same reference symbols are used for elements that correspond to one another.

The Figure 1 shows a beam cutting device 1 with a cutting head 3, from which a cutting beam 2 is emitted onto a workpiece 4 to be cut. The cutting beam 2 emerges from a focusing tube 9 of the cutting head 3 at an exit point 10. The focusing tube 9 is used to guide and focus the emitted cutting beam 2.

The cutting head 3 has a first supply connection 31 for supplying a liquid cutting medium to the cutting head 3, furthermore a second supply connection 32 for supplying an abrasive to be added to the cutting medium and a third supply connection 33 for supplying a gaseous medium under overpressure, which is hereinafter referred to as pressurized gas . The first supply connection 31 is connected to a device 21 via a supply line 11. The second supply connection 32 is connected to a device 22 via a second supply line 12. The third supply connection 33 is connected to a device 23 via a third supply line 13. The device 21 can be designed as a storage container, for example as a riser bottle, for the liquid cutting medium, or as a gas liquefaction device for the gas to be liquefied to form the liquid cutting medium. If the device 21 is designed as a gas liquefaction device, it can additionally have a storage container, for example for the intermediate storage of liquefied gas. Via the first supply line 11, the liquefied gas is as Cutting medium fed to the cutting head 3. To generate the required high pressure of the liquefied gas, the device 21 can have a high pressure pump, for example a high pressure pump of conventional design, with which the liquid cutting medium is compressed to the operating pressure.

The device 22 can be designed as a storage container for the abrasive or as a gas solidification device for converting the gas from which the abrasive is formed into solid form. If the device 22 is designed as a gas solidification device, it can additionally have a storage container for the abrasive produced, for example as an intermediate store. The solidified gas is fed as an abrasive to the cutting head 3 via the second supply line 12.

The device 23 can be designed as a storage container for the compressed gas or as a compressed gas generator, for example as a compressor. The compressed gas can in particular be compressed air. If the device 23 is designed as a compressed gas generator, it can additionally have a storage container, for example for the intermediate storage of the compressed gas generated.

The one in the Figure 1 Feed lines 11, 12, 13 shown in the form of individual lines can be shorter or longer depending on the configuration of the beam cutting device. In particular, they can be so short that one or more of the devices 21, 22, 23 are wholly or partially integrated into the cutting head 3 or flanged to it. In particular in the case of longer execution of the supply lines 11, 12, it is advantageous to insulate them well thermally and / or to provide them with a cooling device, in particular a temperature-regulated cooling device.

For better handling, the cutting head 3 can have a handle 34 have on which it is held during beam cutting.

The Figure 2 shows the cutting head 3 with the first, the second and the third supply line 11, 12, 13 and the device 22 in an enlarged, more detailed sectional illustration. It can be seen that the jet cutting device can be operated _{with three different temperature levels T 1} , T ₂ and T ₃ and two different pressure levels P ₁ , P _2. The cutting head 3 has an expansion chamber 7 to which the liquid cutting medium is supplied via the first supply line 11 and the first supply connection 31. The supply to the expansion chamber 7 takes place via a first transition point 6 which is narrowed with regard to the passage cross section, for example in the form of a nozzle. The first transition point 6 reduces the pressure from the value P ₁ to the value P ₂ . In the expansion chamber 7, particles of the abrasive are supplied to the cutting medium via the second supply line 12 and the second supply connection 32. Furthermore, the expansion chamber 7 is supplied with the compressed gas from the device 23 via the third supply line 13 and the third supply connection 33. The expansion chamber 7 is located at the same pressure level P ₂ as the areas which carry the abrasive, that is to say the device 22 and the second supply line 12.

The abrasive mixed with the cutting medium passes through a nozzle 8 into the focusing tube 9 and emerges therefrom as a cutting jet 2 at the exit point 10.

The operation of the jet cutting device is explained below on the basis of the gas carbon dioxide, both for the abrasive and for the cutting medium.

The Figure 3 shows a phase transition diagram for carbon dioxide. There, the temperature in degrees Celsius is plotted along the linearly scaled abscissa, and the pressure is plotted along the logarithmically scaled ordinate in cash. Line 40 is the sublimation line, line 41 is the melting line and line 42 is the saturation line. The carbon dioxide is in the area above the melting line and the sublimation line in the solid state of aggregation, between the melting line and the saturation line in the liquid state of aggregation, and below the saturation line and the sublimation line in the gaseous state of aggregation. Reference number 43 denotes the triple point of the diagram, reference number 44 the critical point.

The jet cutting device 1, as explained above, can be operated as a cutting _{medium with a high pressure, liquid, temperature-controlled CO 2} medium. This can be provided, for example, at 0 ° C with 3000 bar (corresponding to point 37 in Figure 3 ), or at 20 ° C with 4000 bar (corresponding to point 38 in Figure 3 ). _{The CO 2} medium provided in this way is fed through the first supply line 11 into the first supply connection 31 through the first transition point 6, in which a liquid jet of the cutting medium is generated at a lower pressure level. The state of the cutting medium after exiting the first transition point 6 is shown in FIG Figure 3 represented by point 39. There is thus a transition from point 37 to 39 or from point 38 to point 39. In the expansion chamber 7, the solid CO ₂ particles are fed to this liquid cutting medium as an abrasive. These already have an output size that is suitable for beam cutting. The effect can occur that the abrasive particles enlarge on the way through the focusing tube 9 as a result of the accumulation of freezing liquid cutting medium.

In the expansion chamber, for example, an operating point at -57 ° C and 7 bar pressure can be set, corresponding to point 39 in Figure 3 .

Since the pressures P ₁ and P ₂ differ from each other, it is necessary to Provide a temperature-controlled cooling chamber 5 in the immediate vicinity of the expansion chamber 7 so that, on the one hand, the liquid CO ₂ flow does not pass into the gaseous phase and, on the other hand, the solid CO ₂ particles (dry ice) also do not change their physical state directly. The cooling chamber can, for example, have a cooling coil through which a liquid cooling medium, for example glycol or R134a, is conveyed.

After passing through the expansion chamber 7, the flow of liquid and solid CO _{2 is passed} through a second transition point 8 into the focusing tube 9, in which a nozzle effect also occurs due to the exit from the cooled environment and the positive pressure difference between the expansion chamber 7 and the environment so that at the end of the focusing _{tube 9 the flow of liquid and solid CO 2} and the compressed air exits in an accelerated manner. In addition, the solid CO ₂ particles are thermally stabilized by the liquid CO ₂ cutting medium.

Here, the effect is used that the carbon dioxide has a triple point depending on pressure and temperature, i.e. the carbon dioxide can be present next to one another in a solid and in a liquid state at the same temperature and the same pressure. The phase transition (liquid to gaseous or solid to gaseous) takes place after the end of the cutting process after the cutting area of the workpiece 4 has been separated and cooled. Ultimately, only gaseous carbon dioxide remains from the cutting beam 2. Thus, residue-free jet cutting is possible.

The Figure 4 FIG. 4 shows a further embodiment of the beam cutting device, with a detailed illustration similar to that of FIG Figure 2 is used. In contrast to the Figure 2 In the illustrated embodiment, the cutting head 3 has a fourth supply connection in the area of the outlet pipe 9 56 and, as a further option, a fifth supply port 57. The fourth supply port 56 is connected via a first pressure reducer 54 via lines 51, 52 to a pressurized gas supply, for example with the pressurized device 22 or the pressurized gas supply 23. The fifth supply port 57 is connected to a second pressure reducer 55 via lines 51, 53 The pressurized gas supply is connected, for example to the device 22 which is under excess pressure or the pressurized gas supply 23.

By supplying pressurized gas via the fourth and possibly the fifth supply port 56, 57, a pressure gradient is to be created with respect to the second supply port 32 or the expansion chamber 7. In particular, the pressure present at the fourth supply connection 34 should be slightly lower than the pressure present at the second transition point 8. To do this, a pressure reduction is necessary if both points are fed from the same pressure supply as in the Figure 4 shown. The first pressure reducer 54 with respect to the fourth supply connection 56 and the second pressure reducer 55 with respect to the second supply connection 57 are used for this purpose. The pressure reducers 54, 55 can be designed as throttles or diaphragms with a fixed or adjustable cross section.

Only a minimally lower pressure than at the transition point 8 is generated via the fourth supply connection 56. Due to this slight pressure difference, for example in the range of 0.1 bar, the liquid cutting medium mixed with the abrasive can be accelerated up to the fourth supply connection 56 without a phase transition taking place, ie the liquid cutting medium remains in the liquid phase. A transition of the liquid cutting medium into the gaseous phase can only take place after the fourth supply connection 56. If the fifth supply connection 57 is not provided, this can be done simply by the pressure increase taking place downstream of the fourth supply connection 56 to the atmospheric level in the region of the outlet point 10. If the fifth supply port 57 is present, there can be by feeding one further, in this case considerably lower pressure value than at the fourth supply connection 56, the transition into the gaseous phase can be controlled even more precisely. For example, if a pressure of 15 bar is present at the transition point 8, a pressure of 5 bar can be fed in via the fifth supply connection 57.

The fourth supply connection 56 is advantageously arranged in the lower half of the longitudinal extension L, for example at the transition into the lower third, based on the longitudinal extension L of the outlet pipe 9 between the transition point 8 and the outlet point 10. In this way, a relatively long acceleration path is provided for the liquid cutting medium in combination with the abrasive, in which the latter can be accelerated in a defined manner without gaseous turbulence.

Claims (13)

1. A jet cutting device (1) for cutting materials (4) by means of a cutting jet (2), the jet cutting device (1) comprising at least one cutting head (3) which is arranged to discharge the cutting jet (2) onto the material (4) to be cut, the cutting head (3) having at least one first supply connection (31) for supplying a cutting medium in liquid form and at least one second supply connection (32) for supplying an abrasive agent to be added to the cutting medium in solid form, the first supply connection (31) being coupled to a first supply line (11) carrying a liquefied gas, and the second supply connection being coupled to a second supply line (12) carrying, as abrasive agent, a gas solidified in solid form, so that the first supply connection (31) supplies the liquefied gas to the cutting head (3) and the second supply connection (32) supplies the gas solidified in solid form to the cutting head (3), and wherein the cutting medium and the abrasive agent form the same gas in the gaseous state.
2. Jet cutting device according to the preceding claim, characterized in that the jet cutting device (1), in particular its cutting head (3), has an expansion chamber (7) in which the abrasive agent is mixed with the liquid cutting medium.
3. Jet cutting device according to the preceding claim, characterized in that the jet cutting device (1) has at least one first transition point (6) which is narrowed with respect to the passage cross section and through which the liquid cutting medium is guided from the first supply line (11) into the expansion chamber (7).
4. Jet cutting device according to one of claims 2 to 3, characterized in that the expansion chamber (7) has, on an outlet side for the abrasive agent mixed with the cutting medium, a second transition point (8), narrowed with respect to the passage cross section, into an outlet tube (9) of the cutting head (3).
5. A jet cutting apparatus according to any one of the preceding claims, characterized in that the cutting head (3) comprises at least one temperature-controlled chamber (5).
6. Jet cutting device according to one of the preceding claims, characterized in that the jet cutting device (1) has at least one third supply connection (33) for supplying a gaseous medium under overpressure, which is connected to a pressurized gas supply (23) and/or a pressurized gas generator, wherein within the jet cutting device (1) the expansion chamber (7) and/or the second supply line (12) is connected to the third supply connection (33).
7. Jet cutting device according to one of the preceding claims, characterized in that the cutting head (3) or an outlet tube (9) of the cutting head (3) has a fourth supply connection (56) arranged downstream of the first and/or the second supply connection (31, 32) for supplying a gaseous medium under overpressure, which is connected directly or via a first pressure reducer (54) to a compressed gas supply (23) and/or a compressed gas generator.
8. A jet cutting apparatus according to the preceding claim, characterized in that the cutting head (3) or an outlet pipe (9) of the cutting head (3) comprises a fifth supply connection (57) arranged downstream of the fourth supply connection (56) for supplying a gaseous medium under overpressure, which is connected directly or via a second pressure reducer (55) to a compressed gas supply (23) and/or a compressed gas generator.
9. A jet cutting method for cutting materials (4) by means of a cutting jet (2), wherein an abrasive agent in solid form is supplied to a liquid cutting medium, wherein the cutting medium is a liquefied gas and the abrasive agent consists of a gas solidified in solid form, wherein the cutting medium and the abrasive agent form the same gas in the gaseous state, characterized by carrying out the method by means of a jet cutting device (1) according to one of claims 1 to 8.
10. Method according to claim 9, characterized in that the liquid cutting medium is fed under high pressure through a feed pipe (11) to a nozzle (6) of a cutting head (3), in which a liquid cutting jet is generated which, for pressure reduction, is fed into an expansion chamber (7), in which the abrasive agent is mixed with the liquid cutting medium.
11. The method according to claim 10, characterized in that the expansion chamber (7) is pressurized with a gaseous medium under overpressure.
12. Method according to one of claims 10 to 11, characterized in that at least the expansion chamber (7) is temperature-controlled in such a way that the liquid cutting medium and the solid abrasive agent do not immediately change the state of aggregation at least in the expansion chamber (7).
13. Method according to any one of claims 9 to 12, characterized in that in the cutting head (3) or in an outlet tube (9) of the cutting head (3) downstream of the expansion chamber (7) a relative negative pressure is generated with respect to the pressure in the expansion chamber, by means of which the liquid cutting medium with the admixed abrasive agent is accelerated without changing the phase state.

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