CZ307993B6 - Device and method for on-line control of remote transmission laser welding of materials - Google Patents

Abstract

Remote transmission laser welding of materials is carried out by inputting a thermal imaging camera (3) thermal imaging system (15), into which the output of the member (13) is brought to define the process is the temperature field of the measured surface of the top material (5) divided into thermal imaging sections (7) corresponding to the laser sections (8). Each laser section (8) corresponds to a thermovision section (7), which may be of a different size than the laser section (8) and may have a different spatial location. The output of the thermal imaging camera (3) of the thermal imaging system (15) is fed to an evaluation element (11), the output of which is fed via the control element (10) to the scanning optics (1) and to the laser source (12).

Description

Technical field

BACKGROUND OF THE INVENTION The present invention relates to an apparatus and method for the on-line control of remote transmission laser welding of materials, particularly for industrial laser welding of plastics.

BACKGROUND OF THE INVENTION

Laser welding is based on the transmission principle. The base material to be welded is contact-coated with a top layer of a material that is permeable to the laser wavelength. The laser beam passes through the top layer. The base material, which is impermeable to the laser wavelength, is in contact with the topsheet. The laser radiation is therefore effectively absorbed at the interface between the two layers, where a weld is generated by the heat supplied.

Until now, remote transmission laser welding has been used without feedback of surface temperature control, or feedback control from a temperature sensor placed in the optical path created by the scanning optics of the laser system has been used.

The disadvantage of the first case is the inability to regulate the technological parameters of laser welding in dependence on the temperature course in the place or surroundings of the weld.

In the second case, although local surface temperature information is available to the material at the site of application of the laser beam, which is an advantage over the first case, it is not possible to use the temperature from another location to control the welding and thus perform the most efficient welding.

In some cases, this deficiency has been partially eliminated by the use of a thermal imaging camera system, but only as a means of process monitoring, without any response to the control of the technological process itself.

Not all of the above mentioned methods of remote transmission laser welding of materials do not ensure optimal welding method and quality of welds.

SUMMARY OF THE INVENTION

The above-mentioned drawbacks are largely eliminated by the apparatus and method for on-line control of the remote transmission laser welding of materials according to the invention, wherein the principle of the apparatus consists of a thermal imaging system and a laser system, the thermal imaging system being a thermal imaging camera connected to the defining a process and an evaluation member for evaluating the temperature field of the sensed surface of the material, and that the laser system is comprised of a control member coupled to the scanning optics and to the laser source. The thermal imaging system is connected to the control system of the laser system via an evaluation element.

The principle of the method performed by the aforementioned device is that the welding trajectory is divided into multiple sections for laser beam control, and the thermal imaging camera that follows the laser beam trajectory senses the temperature field of the top layer, which is divided into the same number of sections as the weld trajectory . Each laser section corresponds to a thermovision section, which may be of a different size than the size of the laser section and may have a different spatial location. The output of the thermal imaging camera is fed to the evaluation element to evaluate the minimum, maximum and average temperatures of the individual thermal imaging sections, the values of which

To the control member of the scanning optics for controlling the laser technology on the corresponding laser section.

The advantage of the apparatus and method for the on-line control of the remote transmission laser welding of the materials according to the invention is the optimization of the welding conditions according to the particular conditions and the perfectly performed welds.

Clarification of drawings

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail by means of two drawings, in which: FIG. 1 is a schematic front view of an apparatus and method for the on-line remote laser transmission welding of materials according to the invention. FIG. 2 is a schematic plan view of the laser beam trajectories and laser and thermal imaging sections.

DETAILED DESCRIPTION OF THE INVENTION

A practical example of the apparatus and method for the on-line control of the remote transmission laser welding according to the invention is apparent from the attached figures.

In Fig. 1, a base backsheet 4 with a topsheet-topsheet 5 is indicated. The backsheet 4 is acted upon by a laser beam 2 emitted from the scanning optics 1 of the device itself, consisting of a thermal imaging system 15 and a laser system 14 wherein the thermal imaging system 15 is comprised of a thermal imaging camera 3 coupled to the process definition member 13 and an evaluation member 11 for evaluating the temperature field of the sensed surface of the material and the laser system 14 comprises a control member 10 coupled to the scanning optics 1 and laser source 12; wherein the thermal imaging system 15 is connected to the control member 10 of the laser system 14 via the evaluation member 11.

The thermal field on the surface of the topsheet 5 emits thermal radiation 9, which is sensed by the thermal imaging camera 3 connected to the evaluating member 11. The output of the evaluating member H in the form of minimum, maximum and average temperature is fed to the control member 10 controlling the movement and intensity of the laser beam 2. The laser beam 2 passes through the top material 5 and forms a weld 6 in the base material 4.

In Fig. 2, the direction of movement of the laser beam 2 indicated by the arrow and the trajectory of the laser beam 2 movement over the laser sections 8 are visible on the upper material 5. Dotted thermal lines 7 are shown in dashed lines. as large as laser sections 8.

The laser beam 2 passes through the topsheet 5, which is permeable to the wavelength of the laser radiation. The base material 4, which is impermeable to the wavelength of radiation, is a phenomenon of contact with the top material 5. The radiation of the laser beam 2 is therefore effectively absorbed at the interface between these materials, where the weld heat is subsequently created. The welding trajectory of the weld 6 is divided into a plurality of sections. Different technological parameters can be defined for each section, such as the process speed of the laser beam 2 movement through the material, the power of the laser source, etc. Scanning optics 1 of the laser system ensures the repetitive movement of the laser beam 2 over the selected trajectory resulting in quasi-simultaneous heating of the material all over the trajectory. and forming a weld 6.

The thermal imaging camera 3 senses contactlessly the thermal radiation 9 of the surface of the upper material 5 and evaluates the time course of the temperature field of the sensed surface of the material in the evaluation element 11 using the input parameters of the radiation process. Temperature field of measured surface,

As an output of the use of the thermal imaging camera 3, it is divided as in the definition of the laser process into a corresponding number of thermal imaging sections 7, copying the trajectory of the movement of the laser beam 2 over the material. Each laser section 8 corresponds to a certain thermal imaging section 7. However, it does not have to be the same size and does not have the same spatial location.

During the welding process, their temperatures (minimum, maximum and average) are evaluated in connection with the thermovision sections 7, the values of which are used in the control member 10 to control the laser technology on the corresponding laser section 8. This can be used to

- termination of the welding process on the relevant section when the temperature reaches the desired temperature

- controlling the power of the laser source so that the temperature develops according to the desired time course

- controlling the speed of movement of the laser beam 2 (process speed) so that the temperature develops according to the desired time course

- identification of an incorrectly executed weld if the heating rate is lower than the specified value or the end temperature is lower than the specified value

The above applies:

in the case of parallel operation of multiple laser systems with multiple scanning optics, in the case of parallel deployment of multiple thermal imaging camera systems to capture a single process in case the scanning optics 1, thermal imaging camera 3 or material assembly are positioned by an industrial robot or other handling system wherein the thermovision section 7 is defined in the form of a point, line or area analysis in a thermogram in case the temperature of the thermovision section 7 is evaluated for control other than the minimum, maximum or average temperature of the individual pixels of the thermogram assigned to the defined thermovision section 7.

An advantage of the solution according to the invention is also the fact that the temperature can be used at any point of the surface of the welded materials for control, not only from the location where the laser beam 2 acts directly.

Industrial applicability

The apparatus and method for the on-line control of the remote transmission laser welding of materials according to the invention can be successfully used wherever a precise definition of the laser process with respect to the welding temperature is required for a quality weld, particularly in industrial laser welding plastics.

PATENT CLAIMS

Claims (2)

An apparatus for on-line remote laser beam welding of materials, comprising a laser source and an optical unit, characterized in that it consists of a thermal imaging system (15) and a laser system (14), the thermal imaging system being a thermal imaging camera ( 3) associated with the process definition member (13) and the evaluation member (11) For evaluating the temperature field of the sensed surface of the material, and that the laser system (14) is comprised of a control member (10) connected both to the scanning optics (1) and to the laser source (12), the thermal imaging system (15) is connected to the control member (10) of the laser system (14) via an evaluation member (11). Method of on-line remote laser transmission welding of materials performed by a device according to claim 1, characterized in that the weld trajectory (6) is divided into several sections for the purpose of controlling the laser beam (2), and a thermal imaging camera (3) copying the trajectory of movement of the laser beam (2) is sensed by the temperature field of the topsheet (5), which is divided into the same number of sections as the trajectory of the weld (6), each laser section (8) corresponding to a thermovision section (7). the output of the thermal imaging camera (3) is fed to the evaluation member (11) to evaluate the minimum, maximum and average temperatures of the individual thermal imaging sections, the values of which are fed to the control a scanning optics (1) 15 (10) for controlling laser technology on a corresponding laser (8).