FI113849B - Method in connection with laser processing equipment - Google Patents

Description

113849

The present invention relates to a method for laser processing equipment, in which nitrogen is produced as a shielding gas in a so-called "laser" process.

using a nitrogen generator, such as a membrane, PSA separator or the like, which separates the nitrogen gas from the gas stream treated with it and whereby 10 recycling operations are known per se in the machining process.

In the context of the above, it is known today to use, firstly, a variety of laser processing equipment, such as either a working laser unit | 15 moves relative to the material to be machined, or else the material to be machined moves relative to the solid laser processor. When machining with this type of technology, it is necessary to use a shielding gas for a variety of materials, for example for material 20 / manufacturing reasons and e.g. to prevent ignition and oxidation of the machining material, as is currently the case, for example, by applying to the laser processor pure nitrogen gas from a protective gas battery formed from individual nitrogen cylinders. This type of solution has the disadvantage that, in order to ensure continuity of production, the nitrogen gas cylinders of the shielding gas battery have to be stored in sufficient numbers and need to be replaced quite frequently, since shielding gas 30 is sometimes very high; The average operating time of one conventional nitrogen gas cylinder is approximately 10 minutes.

As the treatment of individual cylinders of nitrogen gas is quite laborious in the 35 types of processing described above, efforts have been made to develop the production of nitrogen to be used as a shielding gas. using a nitrogen generator. Figures 1a to 113849 2 and 1b show, by way of example, two nitrogen generator solutions available on the market today which, in principle, could be used for the above purpose. Figure 1a illustrates in particular the so-called. PSA (Pressure Swing

Adsorption) separator with a so-called "processing unit". a molecular bed of special activated carbon through which air / compressed air is conducted to separate the nitrogen therefrom. Ko. in practice, the separator operates so that the separator mattress, which is active at any one time in the 10 processing units, lasts as long as sufficient separation capacity is maintained, after which the process automatically switches off the dirty mattress to clean it, e.g. by rinsing, 15 whereby the mattress that had been cleared in the previous step is in turn reused.

I The nitrogen generator of the type described above is capable of producing up to 99.9999% nitrogen gas, which is in practice sufficiently pure even for particularly demanding laser processing.

On the other hand, Fig. Ib shows by way of example a membrane separator available on the market today, in which the resolution is largely based on mechanical filtration. The membrane currently available on the market; : The filters are capable of producing up to about 99.9% of nitrogen gas, which is not possible for the given gas.

use of separators as such, especially for demanding laser processing.

il 30 "" Em. Whereas the problem with the use of nitrogen generators in laser processing is due to current technology firstly; Even though the separation of nitrogen from air / compressed air requires a very large throughput of the nitrogen generator, the total power required by the nitrogen separation process is disproportionately massive in terms of practical capability. Typically, a volume flow rate of about 6 m3 / min of air / compressed air through a nitrogen generator is required to provide the shielding gas required for laser processing. This further results in that the compressor 5 required to process the compressed air / air should have a power of about 40 kW. However, such high compressor power is in practice no longer justified, as it increases the cost of acquisition and operation disproportionately, so utilization of the nitrogen separation process in the aforementioned context is not economically justified in its present form. On the other hand, the use of existing membrane separators, in particular, still has the problem in practice that their resolution as such is not high enough for particularly demanding laser processing.

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Prior art can be found e.g.

; U.S. Patent No. 4,319,120, which discloses helium as a shielding gas; the gas is recycled, not the gas in question.

The solution is in no way related to the subject matter corresponding to the present invention. On the other hand, WO 95/33594, for its part, discloses, in principle, an embodiment according to the preamble to the utilization of nitrogen gas, in which case the actual purpose is, however, to protect mirrors belonging in particular to a laser light source;

u '\. The purpose of the method of the present invention is to provide a decisive improvement on the above problems and thus to substantially improve the state of the art. To accomplish this purpose, the method of the invention is essentially characterized in that i; the gas to be processed by the nitrogen generator is 35 processing gases formed by shielded gas-protected laser processing.

4, 113849

One of the main advantages of the process according to the invention is its simplicity, efficiency and reliability, which makes it possible, first of all, to carry out laser-machining in an economically advantageous way, especially with regard to the currently laborious use / storage of shielding gas.

First of all, the method according to the invention makes it possible to significantly improve the treatment of the shielding gas, because the currently required laborious storage of nitrogen-10 bottles and their supplements can be avoided by utilizing so-called nitrogen gas in the production of nitrogen. an autonomous process gas cycle.

The advantage of the process according to the invention is based in particular on the simple fact that, according to current knowledge, the oxygen content of the working gas formed in shielded gas-protected laser processing is typically about 5%, whereas the oxygen or compressed air content is about 20%.

In practice, this means that the volume flow through the nitrogen generator 20 will be reduced to a quarter of what would be needed using h :, 'air / compressed air as a process medium, which will naturally reduce the amount needed for the nitrogen separation process. Thus, the method according to the invention firstly facilitates the preparation of a solution for the above purpose, since it makes it possible to use conventional compressors for pressurization without particularly high yield requirements. In this context, i 1 'also applies to this. of course, the reliability of the process T is improved, since it is possible to use a large amount of stan- dard; V standardized and practically proven components.

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Advantageous embodiments of the method of the invention are set forth in the dependent claims.

5, 113849

In the following description, the invention will be illustrated in detail with reference to the accompanying drawings, in which Figures 1a and Ib show some preferred nitrogen generators suitable for the utilization of the process, i.e. PSA separator (Fig. 1a) and Membrane Difference ink (Fig. Ib). a laser machining apparatus in which the method of the invention can be utilized, and Figure 3 illustrates a preferred operating principle of the method of the invention as an exemplary 20 kinetic process diagram.

The invention relates to a method in connection with laser processing equipment \ :, L, in which laser processing LT is performed.

.L 'uses nitrogen N2 as a shielding gas, which is produced in so-called.

! By using a nitrogen generator 1, such as a membrane, PSA separator:: or the like, which separates the nitrogen gas: from the gas stream treated with it. The gas to be processed by the nitrogen generator 1 is the working gas TK formed in the shielding gas-protected laser machining LT.

'1' In particular, the preferred embodiment shown in Figure 2; With reference to the target, the working gas TK removed from the laser machining LT and prefiltered e.g. with the laser machining device 35 is further filtered LS to neutralize it in particular before being fed to the nitrogen separation process I described e.g.

Further, as a preferred embodiment of the method, with particular reference to the operating diagram of Figure 3, the recycled working gas TK is preferably pre-pressurized with a screw compressor 2 or the like 5, for example to a pressure of 6-12 bar, before being fed to the nitrogen generator 1.

Further, as a preferred embodiment of the method, the nitrogen gas N2 produced by the nitrogen generator 1 is pressurized with an additional pressure, preferably a 2-6 kW piston compressor 5 or the like, for example to a pressure of 30-300 bar, for intermediate storage and / or recovery.

3, the nitrogen gas produced by the nitrogen generator 1 is stored in an intermediate storage arrangement 3, from which the nitrogen gas is further supplied for use in laser processing LT.

In this connection, the storage arrangement 3 consists of e.g.

20 from a shielding gas battery formed from one single gas container or from several separate gas cylinders.

<; A further advantageous application of the process is: v, 25 it is also possible to operate in particular by purifying the nitrogen gas produced by the nitrogen generator 1, in particular _____; to eliminate its residual oxygen by ozonation, such as an ozone generator 4a, activated carbon filtration 4b and drying 4c. In the ozone generator 4a, the residual oxygen contained in the nitrogen-30 gas is converted to ozone, and in the activated carbon filtration after the ozone generator 4b, the ozone is further converted into water, which is removed by e.g.

Alternatively, a so-called N2 purifier is used such that the remaining oxygen molecules are incinerated e.g.

7 113849 using hydrogen gas, eg in a palladium bed, and the resulting water is removed with a suitable dryer.

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As illustrated in the scheme of operation, the nitrogen generator 5 is preferably further provided with a balancing arrangement 6, such as a suction side of the nitrogen generator 1, preferably e.g. 0.3-1 m3 pre-charge tank 6a and a pressure side thereof, preferably e.g. 0.5. - 2 m3 retention tank 6b.

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In particular, as shown in the flow chart of Fig. 3, a preferred embodiment in this connection is a dryer 7a and a filter i 15 7b in connection with the pre-pressurized screw compressor 2. The former is intended to dehumidify the humidity generated when using a screw compressor, and the latter is intended to eliminate, in particular, oil transported to the fluid being processed from the screw compressor drive. The above design and operating values preferably have a power of the dryer 7a of about 2 kW. Correspondingly, the power of the nitrogen generator 1 is about 0.2 kW, especially when using a PSA separator of the type shown in Fig. 1a.

t l i; It is to be understood that the invention is not limited to the above or described embodiments, but that it can be modified within the scope of the basic idea of the invention according to the requirements of the particular operating conditions and processes. Thus, for certain types of processes it is naturally possible to ϊ ;. use e.g. membrane-T separators of the type shown in Fig. Ib, however, the purity of nitrogen is improved, e.g. by utilizing post-zoning 35 of the type illustrated in Scheme 3, or by connecting several separators in series. It is, of course, also obvious that it is possible to vary quite a lot of the scheme of the type described above by using pressure boosting devices other than those described above or other conventional process engineering devices / circuits per se. In addition, it is of course clear that in the same nitrogen separation process there is a potential! The list uses more to increase the flow rate; parallel nitrogen separators or nitrogen gas; to increase the purity of several nitrogen separators connected in series. In practice, it may still be possible to carry out a nitrogen separation process without a high-pressure intermediate storage arrangement of the type described above by directing nitrogen gas produced by a nitrogen generator directly to the laser feeding apparatus.

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Claims (8)

A method of a laser processing device, wherein during the laser operation (LT) performed with the same, nitrogen (N2) is used as a protective gas produced by using a so-called nitrogen generator (1), such as a membrane, PSA separator or correspondingly, which separates nitrogen gas from the gas stream being treated, and wherein in connection with the working process is utilized in a manner known as conventional recovery, characterized in that as gas to be processed with the nitrogen generator (1), the working gas (TK) is used, which is formed during the shielded gas-protected laser operation (LT). ; 15 2. A method according to claim 1, characterized in that the pre-filtered working gas (TK) removed from the laser work (LT) is filtered (LS) especially for its O 3 purification before being fed into the nitrogen separation process (I). Method according to claim 1 or 2, characterized in that the pressure of the input gas (TK) to be recovered is increased by a screw compressor (2) or the equivalent, preferably of 5-20 kW power, to a pressure of 6-12 bar, before being fed to the nitrogen generator (1). Method according to any of the above claims 1-3, characterized in that the pressure of the nitrogen gas produced by the nitrogen generator (1) is increased by a piston compressor (5) or the equivalent, preferably of 2 - 6 kW power, a pressure of 30 to 300 bar prior to its intermediate storage and / or utilization. 113849 Process according to any of the above claims 1 to 4, characterized in that the nitrogen gas (N2) produced with the nitrogen generator (1) is stored in an intermediate storage device (3), from which the nitrogen gas is further supplied for use in the laser operation. (LT). Process according to any of the above claims 1-5, characterized in that the produced nitrogen gas is stored in the storage device (3) comprising a uniform gas container or a protective gas battery formed of several separate gas cylinders. Process according to any of the above claims 1-6, characterized in that the nitrogen gas produced by the nitrogen generator (1) is cleaned in particular to eliminate its residual oxygen by j! ozonation, such as with an ozone generator (4a), by activated carbon filtration (4b) and drying (4c), by a so-called N2 purifier and / or in a corresponding manner. Method according to any of the above: claims 1-7, characterized in that the function; of the nitrogen separation process (1) is balanced with a balancing device (6) arranged in conjunction with the nitrogen generator (1), as well as with a preload container (6a) located at the suction side of the nitrogen generator (1), preferably with 0. 3-1 m3 volume, and / or with a post-loading container (6b), preferably with 0.5-2 m3 volume, located at ·· - its pressure side.