Laser processing heads with a cross-jet nozzle

Abstract

A laser machining head includes a focusing optical unit for focusing a laser beam in a direction of a machining zone of a workpiece and includes a cross-jet nozzle for producing a cross flow that passes through the focused laser beam transversely (e.g., at a right angle to) a beam axis of the focused laser beam. The distance of the cross-jet nozzle from the workpiece is less than 20 mm (e.g., between 8 mm and 12 mm). A nozzle body having a bottom opening that faces downward toward the workpiece is provided laterally adjacent to the focused laser beam. A protective gas flows out of the bottom opening, which is arranged below the cross-jet nozzle in order to entrain the protective gas flowing between the nozzle body and the workpiece due to the cross flow of the cross-jet nozzle so that the protective gas flows over the machining zone.

Claims

1. A laser processing head, comprising: focusing optics for focusing a laser beam in a direction of a processing zone of a workpiece; a cross-jet nozzle having a transverse end opening portion for generating a transverse flow that passes through the focused laser beam perpendicularly to a beam axis of the focused laser beam for protecting the focusing optics from vapors and splatters; and a height-adjustable nozzle body out of which a protective gas flows, wherein the cross-jet nozzle is arranged at a distance (D) of between 8 mm and 12 mm from the workpiece, wherein the height-adjustable nozzle body includes a bottom opening that faces downward toward the workpiece, and wherein the bottom opening is arranged below the cross-jet nozzle such that the protective gas flows out of the height-adjustable nozzle body and between the height-adjustable nozzle body and the workpiece adjacent the transverse flow of the cross-jet nozzle in a transverse direction and such that the protective gas is entrained by the transverse flow to cause the protective gas to flow over the processing zone.

2. The laser processing head of claim 1, wherein a distance (d) from the bottom opening to the cross-jet nozzle is less than 10 mm.

3. The laser processing head of claim 1, further comprising a meshed structure for generating a laminar flow of the protective gas upstream of the bottom opening.

4. The laser processing head of claim 1, wherein the bottom opening is formed by a first tube end of a tube section that is connected at a second tube end to a protective gas feed via a throttle.

5. The laser processing head of claim 4, wherein an axis of the first tube end of the tube section is oriented obliquely and pointed in a downward direction toward the focused laser beam.

6. The laser processing head of claim 1, wherein the bottom opening is a first bottom opening, wherein the height-adjustable nozzle body further includes a second bottom opening that faces downward toward the workpiece and that is located adjacent the first bottom opening along a side that faces away from the focused laser beam, and wherein the protective gas also flows out of the second bottom opening.

7. The laser processing head of claim 6, further comprising a meshed structure for generating a laminar flow of the protective gas upstream of the second bottom opening.

8. The laser processing head of claim 6, wherein the second bottom opening is formed by an outlet end of a line section that is connected at another line end to a protective gas feed via a throttle.

9. The laser processing head of claim 8, wherein an axis of the outlet end of the line section is oriented parallel to the beam axis.

10. The laser processing head of claim 6, wherein, in the transverse direction, a length (L2) of the second bottom opening is at least as great as a length (L1) of the first bottom opening.

11. The laser processing head of claim 1, wherein at least a lower side of the height-adjustable nozzle body that faces toward the workpiece is made of copper.

12. The laser processing head of claim 1, wherein the height-adjustable nozzle body is mounted adjustably in height on a portion of the laser processing head.

13. The laser processing head of claim 12, wherein the height-adjustable nozzle body is fastened magnetically to the portion of the laser processing head.

14. The laser processing head of claim 1, wherein the cross-jet nozzle is arranged on the height-adjustable nozzle body.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a laser processing head including a nozzle body represented in cross section; and

(2) FIG. 2 shows an enlarged, detailed view of a portion of FIG. 1.

DETAILED DESCRIPTION

(3) FIG. 1 shows a laser processing head 1 including focusing optics 2 that focus a laser beam 3 in the direction of a processing zone 4 of a workpiece 5. The laser processing head 1 also includes a cross-jet nozzle 6 with a Venturi effect that generates a transverse air flow 7 (e.g., a cross-jet 7) that passes through the focused laser beam 3 transversely to the beam axis 8 and protects the focusing optics 2 against vapors and splatters. The laser processing head 1 is moved over the workpiece 5 in a welding direction 9, and the working distance D (as shown in FIG. 2) of the cross-jet nozzle 6 from the workpiece 5 is about 10 mm. In some embodiments, the cross-jet nozzle 6 has an outlet cross-sectional area of 0.257 mm.sup.2 and is operated with an air flow of about 35-40 l/min. Tests have shown that, as a result of the transverse flow 7 being located close to the workpiece, a metal vapor flame occurring during laser welding is limited to a minimal height, resulting in formation of an optimal weld bead.

(4) The laser processing head 1 also includes a nozzle body 10 located on the same side of the focused laser beam 3 as the cross-jet nozzle 6. The nozzle body 10 has a first bottom opening 11 that faces downward toward the workpiece 5, out of which a protective gas 12 flows downwardly. The first bottom opening 11 is arranged close to and below the cross-jet nozzle 6 fastened on the nozzle body 10, such that the protective gas 12 flowing between the nozzle body 10 and the workpiece 5 is sucked by the transverse flow 7 of the cross-jet nozzle 6 in a transverse direction 13 and is entrained at least to such an extent that it flows over the processing zone 4. The first bottom opening 11 extends perpendicularly to the beam axis 8, extends parallel to an upper side of the workpiece 5, has a rectangular cross section of 10-100 mm.sup.2, and is arranged at a distance d of about 5 mm below the cross-jet nozzle 6.

(5) The first bottom opening 11 is formed by one tube end of a tube section 14 that is connected at its other tube end via a throttle 15 to a protective gas feed 16. Immediately downstream of the throttle 15, a device 17 (e.g., a fine-meshed metal wire fabric) is provided in order to generate a laminar flow of the protective gas 12 in the tube section 14. An axis of the tube section 14 (e.g., or of the tube end on the outlet side) is oriented obliquely and pointed in a downward direction toward the focused laser beam 3 so that the protective gas 12 flows laminarly out of the first bottom opening 11 obliquely and downwardly with a flow component in the direction of the transverse flow 7.

(6) The nozzle body 10 optionally has a second bottom opening 21 that faces downward toward the workpiece 5, out of which the protective gas 12 also flows laminarly. The second bottom opening 10 is located adjacent to the first bottom opening 11 on the side facing away from the focused laser beam 3. The second bottom opening 21 is formed by an outlet end of a line section 24 that is connected at its other line end via a throttle 25 to the protective gas feed 16. A device 27 (e.g., a fine-meshed metal wire fabric) is provided in the outlet end of the line section 24 in order to cause the protective gas 12 to flow laminarly out of the second bottom opening 21. An axis of the outlet end is oriented parallel to the beam axis 8 so that the protective gas 12 flows out downwardly, laminarly, and parallel to the beam axis 8 from the second bottom opening 21. A length L2 of the second bottom opening 21 in the welding direction 9 is about two times as great as a length L1 of the first bottom opening 11.

(7) For a simple gas supply to the weld bead, a nozzle body 10 having a single bottom opening 11 is used. If a longer linear gas supply to the weld bead is needed counter to the welding direction 9, a nozzle body 10 having both bottom openings 11, 21 is used. The fine-meshed metal wire fabrics are prefabricated inserts, which can be replaced easily and simply when they are clogged by weld splatters.

(8) The nozzle body 10 is fastened on a holder 18 that is mounted adjustably in height (refer to the double arrow 19 in FIG. 1) in the direction of the beam axis 8 on the laser processing head 1. The nozzle body 10 is fastened on the laser processing head 1 along a magnetic interface 20. According to a height adjustment (a Z adjustment), the distances from the cross-jet nozzle 6 and the nozzle body 10 to the workpiece 5 can be adjusted individually. The magnetic interface 20 is also used at the same time as collision protection, since the magnetic fastening of the nozzle body 10 is released from the laser processing head 1 in the event of a collision of the nozzle body 10 with the workpiece 5.

(9) The protective gas feed 16 extends inside the holder 18, and a compressed air feed 21 for the cross-jet nozzle 6 is fastened externally on the holder 18. The nozzle body 10 is advantageously made of copper, since copper exhibits low splatter adhesion and can be cleaned well.

(10) A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the present disclosure. Accordingly, other embodiments are within the scope of the following claims.