CN117693413A

CN117693413A - Wall element for shielding laser radiation

Info

Publication number: CN117693413A
Application number: CN202280048840.8A
Authority: CN
Inventors: F·雅施; K·吕茨; P·马特
Original assignee: Trumpf European Ag
Current assignee: Trumpf European Ag
Priority date: 2021-07-14
Filing date: 2022-06-21
Publication date: 2024-03-12
Also published as: DE102021118251A1; WO2023285086A1

Abstract

A wall element (10) for a shielding device for shielding laser radiation (22, 22R) of a laser beam source (20) located in a working area (30) from an outer area (40) is provided. The wall element (10) has a multi-layer structure and comprises a core layer (14) made of a non-fusible material. Furthermore, a shielding device for shielding laser radiation comprising a wall element and a laser processing apparatus comprising a shielding device are provided.

Description

Wall element for shielding laser radiation

Technical Field

The present invention relates to the field of protective devices for laser processing equipment. The invention relates in particular to a wall element for a shielding device for shielding laser radiation of a laser beam source located in a working area from an outer area, and to a laser machining apparatus comprising such a wall element.

Background

During the processing of materials by means of laser beams, radiation protection plays an important role in ensuring operational safety.

Fig. 1 schematically shows a laser processing apparatus 100 for processing a workpiece 50. Laser radiation 22 is directed to a workpiece 50 by means of processing optics of a laser beam tool (see laser beam source 20) in order to, for example, process the workpiece, for example, weld or cut. In this case, it is generally unavoidable that: a portion of the laser radiation 22 used for machining may be uncontrollably radiated around the working area 30 of the laser machining apparatus 100, for example, due to reflection of the laser radiation 22 on the workpiece surface (see fig. 1, 22R) or due to failure of the laser beam tool (see the dashed laser beam source 20 and the dashed laser beam 22).

In many fields of application (for example metal working), working takes place with laser powers in the kW range. In order to minimize the potential risk due to uncontrolled stray radiation, the laser processing apparatus 100 is surrounded by a protective enclosure 110 (or guard in general) that should prevent stray radiation from entering the working area 30 into the outer area 40 surrounding the laser processing apparatus 100.

To ensure adequate safety, the protective housing 110 must withstand the laser beam for a prescribed time. The specified service life may vary as appropriate. For example, a multiple (e.g., twice) of the time required to safely shut down the device after a problem is detected may be specified as the lifetime. However, the desired useful life of the protective housing 110 of the laser processing apparatus 100 may be determined entirely differently, as the case may be, taking into account various other factors (e.g., reflection on the workpiece) and certain applicable criteria.

Heretofore, protective housings for laser processing equipment have been made in most cases from sheet materials (e.g., steel or aluminum) or fiberglass reinforced plastics. The necessary security against penetration of the laser radiation is achieved here by a sufficiently large material thickness or by active sensing means (see for example EP 2 153931a1 and the documents cited therein). The metal plate (without sensor means) is suitable for use as a radiation protection device only in the low laser power range due to its relatively large weight. Therefore, especially in the movable part of the protective housing (e.g. the movable part of the door), it is disadvantageous to use only the metal plate as radiation protection. Alternative solutions (such as the use of glass fibre reinforced plastics or sensing devices as described above) are often accompanied by high costs.

In DE 10 2014 118 739 A1 a protective wall is described, which has a sandwich-type structure with two metal plates and an absorber layer located between them. The absorption layer is made of carbonizable material and has a large thickness of at least 40mm, more precisely 80 mm. When the laser radiation hits the protective wall, the first metal layer is melted by the laser. As the metal layer is heated, localized carbonization of the absorber layer begins. Since the absorption layer has good absorption properties in the carbonized state, the absorption layer provides good radiation protection.

Disclosure of Invention

The present invention is based on the task of improving the prior art. In particular, a cost-effective solution for radiation protection walls should be provided which have a slim structure and a low weight and which ensure adequate radiation protection even at high laser powers in the kW range.

In order to solve the task underlying the present invention, according to a first aspect, a wall element for a shielding device for shielding laser radiation of a laser beam source located in a working area from an external area is provided. The wall element has a multi-layer structure and comprises a core layer made of a non-fusible material.

The expression "infusible" is to be understood here as meaning that the material concerned does not melt under the application of laser radiation, but rather (in particular due to carbonization) thermally decomposes.

The wall element according to the invention is particularly suitable for laser processing devices for separating and joining workpieces, in particular of metal. The laser radiation used in such devices is optimized to melt the material to be processed. When the laser radiation hits the core layer of the wall element according to the invention, the core layer does not melt, but rather the thermal decomposition process starts. The energy required for thermal decomposition of the core layer is significantly higher than the energy required to penetrate the metal layer of the same thickness. In other words, the laser radiation takes longer to penetrate the core layer than, for example, to shoot through a steel or aluminum plate of the same thickness. The service life of the wall element according to the invention is thus longer than for conventional metal plates.

The core layer may be made of para-aramid. The core layer may also be made of other non-fusible materials or combinations of materials including, for example, para-aramid fibers or other aromatic polyamide fibers. For example, the core layer may include meta-aramid fibers, aromatic polyimide fibers, aromatic polyamideimide fibers, polybenzimidazole fibers, melamine/formaldehyde resin fibers, phenolic/formaldehyde resin fibers, pre-oxidized PAN fibers, or cellulose/silicic acid hybrid fibers. For example, conventional fire protection mats may be used as the core layer. Such a fire protection mat may for example comprise pre-oxidized Polyacrylonitrile (PAN) as a base material. Conventional fire protection mats provide good radiation protection and can be obtained cost-effectively. The pressboard may also be used as a core layer.

The core layer may have a thickness of between 1mm and 5 mm. For example, the core layer may be a para-aramid felt layer having a thickness of 1.4 mm.

The wall element with a core layer according to the invention has a small thickness and a low weight compared to conventional radiation protection walls, while having very good radiation protection properties.

According to a variant, the wall element may have a radiation-impermeable outer layer which is arranged on the side of the core layer facing the outer region. Depending on the materials used, the core may not be completely radio-opaque, and thus some amount of stray or residual radiation penetrates the core. The outer layer serves as an additional radiation protection against laser radiation penetrating the core layer.

The outer layer may preferably be made of a heat resistant material. Furthermore, the outer layer may have as low a thermal conductivity as possible. Thus, heat can be better conducted away from the core layer.

The outer layer may be made of metal, in particular steel or aluminium. Alternatively, the outer layer may be made of other materials or combinations of materials that meet the desired properties.

The outer layer may have a thickness of between 0.5mm and 5mm, preferably between 1mm and 3 mm. The thickness and material combination of the outer layer depend inter alia also on the laser power used. When the outer layer is too thin, radiation protection is affected. When the outer layer is too thick, its weight may be too high.

According to a further variant, the wall element may comprise a radiation-permeable, oxygen-impermeable inner layer which is arranged on the side of the core layer facing the working area. In other words, the inner layer may consist of a material through which the laser radiation used in the working area is transmitted. The inner layer has the task of blocking the oxygen supply on the working side when the core layer burns due to the laser radiation. Another advantageous effect with respect to the light-transmissive inner layer is that partial damage to the core layer by the laser radiation can be easily identified by burning marks or discoloration on the core layer. The core layer can then be replaced as desired.

The inner layer may be made of acrylic glass or polycarbonate, for example. Suitable materials are for example given the trade name(acrylic glass) or->(polycarbonate) is sold in large quantities. Such materials have a relatively low weight and are available in the market at a cost advantage. The inner layer may also be made of any other material that is radiation transparent (e.g. glass) to the laser radiation to be blocked. The coupling of laser radiation into the inner layer should be prevented as much as possible. In principle, it is advantageous if the inner layer has as high a heat resistance as possible.

The inner layer may have a thickness of between 3mm and 10mm, preferably between 5mm and 8 mm.For example, the inner layer may be 6mm thick under the trademarkAcrylic glass plate of (a).

The wall element according to the invention may, for example, have a two-layer structure with a pressboard as a core layer and an inner layer according to one of the variants described above. Since the pressboard is substantially radio-opaque and has a low oxygen permeability, no additional outer layer is required.

According to a preferred variant, the wall element may have a three-layer structure with a core layer, an outer layer and an inner layer. In this variant, it is advantageous if the outer layer is also impermeable to oxygen. In this way, the oxygen supply from the working area (through the inner layer) and from the outer area (through the outer layer) of the oxygen-permeable core (made of para-aramid fibers, for example) is blocked upon thermal decomposition. In this way, the combustion process of the core layer is significantly slowed down. Oxygen that still builds up from layer to layer due to, for example, flow at the edges of the layer structure is displaced by gases generated during thermal decomposition of the core layer. Thereby, the decomposition process is additionally slowed down.

In order to more effectively block the oxygen supply to the core layer, a seal may be provided which together with the inner and outer layers forms a closed airtight enclosure for the core layer.

According to a further variant, the core layer and the inner layer may be spaced apart from each other, thus constituting an intermediate space between the core layer and the inner layer, wherein the wall element comprises means designed for creating a low-or oxygen-free environment in the intermediate space. The intermediate space makes it difficult for heat to transfer from the core layer to the inner layer. In this way, the inner layer is intended to be prevented from melting due to local heating of the core layer and thus in turn to establish an oxygen supply from the working area. In order to create a low or oxygen free environment in the intermediate space, a vacuum pump may be provided. Alternatively, a gas supply device filling the intermediate space with a shielding gas may be provided.

Overall, the layered structure of the wall element according to the invention enables a significantly longer service life under bombardment of the laser radiation than can be achieved by using individual monolayers alone.

In order to solve the task underlying the present invention, according to a second aspect a shielding device is provided for shielding laser radiation of a laser beam source located in a working area of a laser processing apparatus from an external area, wherein the shielding device comprises at least one wall element according to one of the above variants.

The terms "guard" and "guard housing" are synonymously used within the scope of the present disclosure.

It can preferably be provided that the wall element according to the invention is arranged only in those areas of the protective housing (or of the protective device) which are exposed to the reflected laser radiation particularly when the laser processing device is in operation or in which the operator is in the vicinity of these areas particularly frequently. Such areas may include, inter alia, a top area and/or a door area of the protective housing.

In order to solve the task on which the present invention is based, a laser processing apparatus is provided according to a third aspect. The laser processing apparatus includes: a working area having a laser beam source; and a guard according to one of the above variants.

Drawings

The following description of the preferred embodiments is provided in more detail with reference to the accompanying drawings. In the drawings:

fig. 1 schematically shows the structure of a laser machining apparatus with a protective housing/guard;

fig. 2 schematically shows the structure of a wall element according to the invention according to a variant; and

fig. 3 schematically shows the structure of a wall element according to the invention according to another variant.

Detailed Description

Fig. 1 has been described in more detail in connection with the prior art. Reference is made to the embodiments herein.

The structure of the wall element according to the invention is described below with the aid of fig. 2 and 3.

Fig. 2 shows an exemplary three-layer structure of a wall element 10 according to the invention. The wall element 10 comprises a core layer 14 surrounded by an outer layer 12 and an inner layer 16. The inner layer 16 is arranged on the side of the core layer 14 facing the working area 30 and is made of a light-transmitting but oxygen-impermeable material. The outer layer 12 is arranged on the side of the core layer 14 facing the outer region 40 and is made of a light-and oxygen-impermeable material. When the laser radiation 22, 22R emitted from the laser beam source 20 in the working area 30 reaches the wall element 10, for example due to reflection or due to a fault, it passes through the inner layer 16 and hits the core layer 14 without damaging the inner layer. The core layer 14 is made of a non-fusible material (e.g., para-aramid) and is slowly thermally decomposed or burned by laser irradiation. Oxygen is prevented from flowing through the inner layer 16 and the outer layer 12 to the sites of the core layer 14 where the laser radiation 22 is loaded. Thereby significantly slowing down the decomposition process of the core layer 14.

In the test a wall element according to the invention was used, which wall element has the product of the trade markA 6mm thick inner layer 16 made of acrylic glass, a 2.1mm thick core layer 14 made of para-aramid fabric (in the form of a felt), and a 2mm thick aluminum plate as the outer layer 12. The wall element was bombarded with a laser of 5.33kW from a distance of 460mm for 100 seconds, wherein the outer layer 12 remained intact throughout the test.

Fig. 3 shows a variant of the wall element 10 according to fig. 2. The variant shown in fig. 3 also has an intermediate space 15 between the core layer 14 and the inner layer 16. The intermediate layer 15 makes heat transfer from the core layer 14 to the inner layer 16 difficult. By coupling the laser radiation 22 into the core 12, the core is heated substantially. The heat of the core layer 14 is transferred to the adjacent inner layer 16. In order to prevent the inner layer 16 from melting and possibly to supply oxygen from the working space 30, the intermediate space 15 may be provided as an insulating layer. In the variant according to fig. 3, it must be ensured that no oxygen is supplied from the edges of the wall element 10 (see upper and lower edges of the wall element 10 in fig. 3) to the site of the loading of the laser radiation 22 through the intermediate space 15. In order to prevent this, oxygen can be sucked from the intermediate space 15, for example, by means of a vacuum pump, and the wall element 10 is hermetically closed at its edges by a seal. Alternatively, the intermediate space can be supplied with a protective gas (for example nitrogen) by means of corresponding devices, which protective gas displaces oxygen in the intermediate space.

List of reference numerals

10. Wall element

12. An outer layer

14. Core layer

15. Intermediate space

16. Inner layer

20. Laser beam source

22. Laser radiation

22R reflected laser radiation

30. Work area

40. Outer region

50. Workpiece

100. Laser processing apparatus

110. A protective device.

Claims

1. A wall element (10) for a shielding device for shielding laser radiation (22, 22R) of a laser beam source (20) located in a working area (30) from an outer area (40),

wherein the wall element (10) has a multi-layer structure and

characterized in that the wall element (10) comprises a core layer (14) made of a non-fusible material.

2. The wall element (10) according to claim 1, wherein the core layer (14) is made of para-aramid.

3. Wall element (10) according to claim 1 or 2, wherein the core layer (14) has a thickness of between 1mm and 5 mm.

4. Wall element (10) according to one of the preceding claims, comprising:

-a radiation-impermeable outer layer (12) arranged on the side of the core layer (14) facing the outer region (40).

5. The wall element (10) according to claim 4, wherein the outer layer (12) is made of a heat resistant material.

6. Wall element (10) according to claim 4 or 5, wherein the outer layer (12) is made of metal, in particular steel or aluminum.

7. Wall element (10) according to one of claims 4 to 6, wherein the outer layer (12) has a thickness of between 0.5mm and 5mm, preferably between 1mm and 3 mm.

8. Wall element (10) according to one of the preceding claims, comprising:

a radiation-permeable, oxygen-impermeable inner layer (16) which is arranged on the side of the core layer (14) facing the working area (30).

9. The wall element (10) according to claim 8, wherein the inner layer (16) is made of acrylic glass or polycarbonate.

10. Wall element (10) according to claim 8 or 9, wherein the inner layer (16) has a thickness of between 3mm and 10mm, preferably between 5mm and 8 mm.

11. Wall element (10) according to one of claims 8 to 10, wherein the core layer (14) and the inner layer (16) are spaced apart from each other by an intermediate space (15), wherein the wall element (10) comprises means designed for creating a low-or oxygen-free environment in the intermediate space (15).

12. A shielding device (110) for shielding laser radiation (22, 22R) of a laser beam source (20) located in a working area (30) of a laser machining apparatus (100) from an outer area (40), the shielding device (110) comprising:

wall element (10) according to at least one of claims 1 to 11.

13. A laser processing apparatus (100), comprising:

a working area (30) having a laser beam source (20); and

the shielding device (110) according to claim 12, for shielding laser radiation (22, 22R) of a laser beam source (20) located in a working area (30) with respect to an outer area (40) outside the laser processing apparatus (100).