Method and apparatus for carrying out a laser operation and use of a quick-change filter in such a laser operation

A method and apparatus for carrying out a laser operation, wherein a laser source is provided, wherein lasing gas is supplied from at least one lasing gas source to the laser source for the formation of a laser beam, wherein, with the aid of the laser beam, an operation is carried out, such as for instance a welding, a drilling, a cutting or a lighting operation, wherein the lasing gas which comes from the at least one lasing gas source is fed through at least one lasing gas filter before the gas is supplied to the laser source. The invention further relates to the use of a quick-change filter for cleaning gases consumed in laser processing apparatuses.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to a Dutch application No. NL 1027327 filed Oct. 25, 2004.

BACKGROUND OF THE INVENTION

The invention relates to a method for carrying out a laser operation, wherein a laser source is provided, wherein lasing gas is supplied from at least one lasing gas source to the laser source for the formation of a laser beam, wherein, with the aid of the laser beam, an operation is carried out, such as for instance a welding, a drilling, a cutting or a lighting operation.

The invention further relates to an apparatus for carrying out a laser operation, wherein the apparatus is provided with a laser source, which is connected to a lasing gas source via a lasing gas pipe system.

Lasers are used on a large scale for all kinds of operations. Possibilities are welding operations, drilling operations and cutting operations of metal, plastic, wood, paper and similar materials. However, lighting operations, for instance for lithographic processes, are often carried out with the aid of lasers as well.

A known problem of lasers is that the laser source requires regular maintenance in order to clean the optical system, which is present in the source. Inter alia moisture and hydrocarbons which are introduced into the source via the lasing gas cause pollution of the optical system in the source. Cleaning a laser source is very expensive, involving amounts of several thousands of euros. In order not to let the frequency of cleaning be too high, for various uses, often much stronger laser sources are bought than is strictly necessary for the process. The stronger laser sources can continue to function longer because the power produced by them remains sufficient for carrying out the operation for a longer period, even when the optical system in the source is polluted. It will be clear that laser sources with a higher power also have a higher cost price.

SUMMARY OF THE INVENTION

The invention contemplates providing a method and an apparatus whereby a solution for this problem is provided.

To this end, the method according to the invention is characterized in that the lasing gas which comes from the at least one lasing gas source is fed through at least one easing gas filter before the gas is supplied to the laser source.

The apparatus is characterized in that at least one lasing gas filter is included the lasing gas pipe system.

As a result of the presence of the lasing gas filter, the frequency with which the laser source needs to be cleaned can be reduced drastically. Instead of every six months, the cleaning may, for instance, take place every two years, which yields a saving of several thousands of euros a year. In addition, a laser source with a lower power can be used since the pollution occurring in the course of time need not be factored in. Consequently, the source can have the power needed for the operation to be carried out and not the higher power, as is often done now to compensate for pollution. A further advantage is that gases of a lower purity can be used, which has a considerable cost-reducing effect.

In many laser operations, the laser beam is guided to a laser processing head via an optical system. Also to such laser processing heads, processing gas is often supplied, for instance to screen a cutting area, welding area or drilling area from the atmosphere. The material surface of the material to be processed is thus prevented from oxidizing as a result of the operation when this is not intended or from obtaining an undesired, for instance too rough, surface structure. In practice, it is found that still, despite the use of processing gas, undesired oxidation of the material to be processed occurs. Conversely, with laser cutting operations based on oxidation, an excess of oxygen is desired in the cutting operation and the presence of other gases can result in an undesired surface structure of the material.

According to a further elaboration of the method according to the invention, it is particularly favorable when the processing gas is fed through at least one processing gas filter before it is supplied to the processing head. To this end, according to a further elaboration, the apparatus is characterized in that at least one processing gas filter is included in the processing gas pipe system connecting the laser processing head with the processing gas source.

It is thus effected that the processing gas has a higher purity, which generally results in a better surface quality of the processed material. Undesired oxidation of the processed material is reduced as well when oxygen has been removed from the processing gas by the filter. Further, as a result of a better surface tension and viscosity, the quality of the melting bath will improve when the processing gas does not contain any pollutions. With oxidation-based processing techniques, the efficiency increases when the processing gas is pure oxygen instead of oxygen with pollutions.

According to a further elaboration of the invention, the method is characterized in that the lasing gas contains at least He, N2and/or CO2. It is noted that other gases are also possible when lasers of a different color are used.

According to a further elaboration, the processing gas may comprise, for instance, O2, N2, air, He, Ar and/or H2.

Since the operators of the apparatuses for carrying out a laser operation have had a different type of training than laboratory personnel, it would be particularly favorable if the placement and removal of the filters could be done in a relatively simple manner.

To this end, the method for a further elaboration is characterized in that the empty gas filter is a quick-change filter which can manually be fastened on a base. Such quick-change filters are, for instance, described in EP-A-0 606 960, a European patent application 04076518.2 which is published as EP 1 479 428 A2, and are also put into circulation by Varian® Inc. under the designation Gas Clean Filter and are to date used for cleaning carrier gases for the purpose of detection processes such as gas chromatography and mass spectrometry.

It will be clear that it is likewise advantageous for the processing gas filter when a quick-change filter is used for it which can manually be fastened on a base.

Such quick-change filters can only be mounted on the base in one manner and are fastened by a fastening ring to be loosened and tightened manually. Consequently, the apparatus operator can simply change such filters by himself.

Preferably, the method according to a further elaboration is characterized in that, when the quick-change filter is charged, the quick-change filter is removed from the base, while, by the removal of the quick-change filter from the base, a gas supply and a gas discharge in the base to the quick-change filter are closed off automatically and a bypass pipe in the base is opened automatically, in such a manner that an uninterrupted gas supply to the laser source and/or the processing head takes place, while, by placing a new gas filter on the base, the bypass pipe is automatically closed off, the gas supply and gas discharge to the quick-change filter are automatically opened and the gas is fed through the filter.

It is true that the laser source is then temporarily fed with polluted gas, but the extent of pollution which occurs is very small, since this only takes a very short period. In any case, it is thus effected that the laser operation can simply continue, which is in many cases very important.

According to a further elaboration of the method according to the invention, the lasing gas can be led through a moisture filter, an oxygen filter and/or a hydrocarbon filter. Optionally, a combination of these filters can be included in one single filter housing. Here, it is preferred when the at least one filter is provided with an indicator which indicates whether and optionally to what degree the filter material is saturated, while the filter is replaced by a new filter when the indicator indicates a particular degree of saturation.

It is thus effected that the users replace the filters in time, so that it is guaranteed that, always, pure gas is led to the laser source and/or the laser processing head.

The invention further relates to the use of a quick-change filter for cleaning lasing gas which is led to a laser source of a laser processing apparatus, while, by a simple operation, the quick-change filter is placeable on and removable from abase which is included in a lasing gas pipe system connecting a lasing gas source with the laser source.

The invention further relates to the use of a quick-change filter for cleaning a processing gas which is led to a laser processing head of a laser processing apparatus, while, by a simple operation, the quick-change filter is placeable on an removable from a base which is included in a processing gas pipe system connecting a processing gas source with the laser source.

Above-mentioned uses result in the advantages described in connection with the method and the apparatus.

DETAILED DESCRIPTION OF THE INVENTION

By way of example,FIG. 1shows a laser cutting apparatus provided with a cutting table1, a laser source2, three lasing gas sources3,4and5, a laser processing head6, which is connected with a portal7. The portal7is movable along a guide8with respect to the table1. The processing head6is movable along the portal7via guide9. The laser beam10, which comes from the laser source2, is guided to the processing head6with two mirrors11,12. All this is schematically shown inFIG. 2. In the workpiece W, any contour C can be cut with the aid of the laser processing head6. Under the table1, there is an exhaust chamber13which is connected to an exhaust14.FIG. 1further shows two processing gas sources15,16. From the lasing gas sources3,4,5, lasing gas pipe systems17,18,19extend which are in fluid connection with the laser source2. From the processing gas sources, a processing gas pipe system20extends to the laser processing head6. In the present exemplary embodiment, in each lasing gas pipe system17,18,19, a filter in the form of quick-change filter21,22,23,24is included. In the processing gas pipe system20, two quick-change filters25,26are included; this incidentally also holds true for the lasing gas pipe system designated by the reference numeral17. It will be clear that, also in the other lasing gas pipe systems18,19, more than one filter can be included, for instance a filter for moisture, a filter for hydrocarbons and a filter for oxygen. Also, one single filter may be included in each lasing gas pipe system, which filter is arranged for removing different undesired substances from the lasing gas. In the processing gas pipe system20, two filters are shown. It will be clear that, here, likewise more than two filters or one filter can be used, while the final result of the filter operation of course needs to be that the gas led to the laser processing head6has the desired purity. In the present exemplary embodiment, the lasing gas source3contains He, the lasing gas source4contains N2and the lasing gas source5contains CO2. The processing gas source15contains O2and the processing gas source16contains N2in the present exemplary embodiment. Of course, other gases are also possible depending on the type of operation to be carried out and the type of laser source2which is used.

FIG. 3schematically shows a laser processing head6for carrying out a cutting operation. Processing heads for welding and processing heads for drilling have a similar construction. Clearly visible is the laser beam10which is focused with the aid of a lens27, such that the focus is aimed at the workpiece W. Via processing gas pipe system20, processing gas is led into the laser processing head6and fed to the processing point P, with the purpose of screening the processing point P, so that oxygen and other components of the ambient air have no access to the processing point P during the operation. Thus, a very good surface quality of the processed zone is obtained, particularly because the processing gas has a very high purity as a result of the filter operation it has been subjected to. In a cutting operation not based on oxidation, the workpiece material is prevented from oxidizing. In a cutting method based on oxidation, pure oxygen is supply to the processing point, which results in a greater efficiency during cutting.

FIG. 4shows an example of a quick-change filter28and a base29on which the quick-change filter can be placed with the aid of a fastening ring30to be tightened manually. Such a quick-change filter is described in the above-mentioned European patent publications, whose contents are considered to be incorporated herein by reference. The base contains an inlet31and an outlet32, which are connected by the lasing gas pipe system17,18,19and/or the processing gas system20. The base further comprises a gas supply33leading to the quick-change filter28and a gas discharge34through which the gas coming from the quick-change filter28is discharged again to the outlet32of the base29. The gas supply33and the gas discharge34are preferably provided with stop valves which are automatically opened upon placement of the filter28on the base. Upon removal of the filter28from the base29, the valves will close automatically. Optionally, in the base, a bypass pipe may be provided which is closed off when the filter is placed on the base29and which is opened when the filter is removed from the base29. Thus, an uninterrupted feed-through of gas to the laser source and the laser processing head6, respectively, is guaranteed.

FIG. 5shows a cross-sectional view of an embodiment of a base101with a filter201placed thereon.FIG. 6shows the base101without a filter201placed thereon. The base101is provided with a by-pass pipe151and with means for creating a fluid connection between the inlet connecting element103and the outlet connecting element104via the by-pass pipe151when a quick-change filter102is decoupled from the base101and for closing off this fluid connection when a quick-change filter102is placed on the base101. In the present exemplary embodiment, the means are formed by incorporating in the gas inlet stub106a pin152which is longitudinally adjustable in relation to the base101, which pin is provided with a first and second sealing face153,146. The base101, more in particular the gas inlet stub106thereof, contains a first and second valve seat147,148. In a first position, the pin152lies with the first sealing face153against the first valve seat147and thus forms a block in a fluid connection between the gas inlet stub106and the inlet connecting element103while a fluid connection is present between the inlet connecting element103and the by-pass pipe151(seeFIG. 6). In a second position, the pin lies with the second sealing face146against the second valve seat148and thus forms a block in a fluid connection between the by-pass pipe151and the inlet connecting element103while a fluid connection is present between gas inlet stub106and the inlet connecting element103(seeFIG. 5). The pin152is pressed into the position shown inFIG. 6by a spring149. Due to the presence of the by-pass pipe151, the pipe system as well as the base101remain filled with carrier gas and thus the underlying process, such as for example gas chromatography, mass spectrography or LCMS can continue. Admittedly, unfiltered gas is briefly used, but this generally presents no problem to the underlying process. In any case, the duration of the flushing after changing the filter can be considerably reduced or omitted completely.

Since the gases in the gas sources sometimes also contain solid particles, it is further advantageous when at least one particle filter is disposed in the lasing gas pipe system and/or the processing gas pipe system. Preferably, such a particle filter is located downstream of the filter or the filters for moisture, oxygen and hydrocarbons because such filters can also still release particles. Here, it is further preferred that the particle filters are quickly changeable. To this end, the particle gas filters can be designed as quick-change filters, preferably in the form of a cartridge which is regenerable or disposable. The particle filters may, for instance, remove particles larger than 3 microns from the gas. The particle filter may be designed as a housing with sintered stainless steel or bronze balls therein. Optionally, the particle filter may be placed on a base which is provided with a bypass pipe which is opened automatically when the particle filter is removed from the base and which is closed automatically when the particle filter is placed on the base. A particle filter in the lasing gas pipe system prevents a fast pollution of the optical system via which the laser beam is guided to the processing head. A particle filter in the processing gas pipe system prevents particles from adversely affecting the correct or optimal performance of the operation.

It will be clear that the invention is not limited to the exemplary embodiment described, but that various modifications are possible within the framework of the invention as defined by the claims.

Thus, instead of the laser cutting apparatus, a laser welding apparatus, a laser drilling apparatus or a lighting apparatus may be provided with filters as indicated, in order to improve the efficiency of the apparatus and to considerably reduce the necessity of cleaning the laser source regularly. Further, other gases may be used than those mentioned in the present exemplary embodiment. Although, for reasons concerning operation, it is by far preferable to use quick-change filters, use of so-called inline filters could also be considered. Particularly inline filters which can be changed simply and quickly, for instance such as described in the not prior published international patent application PCT/NL2004/000564, whose contents are considered to be inserted herein by reference, are suitable for this.