Methods and devices for monitoring a welding process for welding glass workpieces

Patent metadata

Field	Value
Publication number	US-12157183-B2
Application number	US-202117318598-A
Country	US
Kind code	B2
Filing date	May 12, 2021
Priority date	Nov 13, 2018
Publication date	Dec 3, 2024
Grant date	Dec 3, 2024

Abstract

The present disclosure relates to methods and systems for monitoring a welding process for welding at least one glass workpiece to another workpiece, e.g., also made of glass, wherein a weld seam is formed in the workpieces in a process zone that is exposed to a pulsed processing beam, e.g., to a pulsed laser beam, such as an ultra-short-pulse laser beam, wherein the radiation emitted by the process zone is detected in a time-resolved manner.

First claim

What is claimed is:

1. An automated method for monitoring a welding process for welding at least one glass workpiece to a further workpiece, the method comprising
forming a weld seam in the workpieces in a process zone that is exposed to an ultra-short-pulse laser processing beam, wherein the weld seam is formed by a periodic formation of bubble-like regions of a plasma in the workpiece;
detecting radiation emitted by the process zone in a time-resolved manner,
wherein the emitted radiation exhibits intensity fluctuations caused by the periodic expansion and collapse of the bubble-like regions of plasma in the glass workpiece, and
wherein the intensity fluctuations are independent of the pulse frequency of the laser processing beam;

determining a quality of the weld seam based on one or more of a periodicity, a frequency, or a frequency spectrum of the intensity fluctuations of the detected radiation, wherein detection of a change in the periodicity, frequency, or frequency spectrum of the intensity fluctuations is indicative of an error in the weld seam; and
providing an error output or a termination of the welding operation, or both, when the quality of the weld seam fails to meet predefined tolerance limits.

2. The method of claim 1 , wherein the intensity of the radiation emitted by the process zone is detected.

3. The method of claim 1 , wherein the radiation emitted by the process zone is detected and captured by a sensor, and further comprising converting the captured radiation into a signal and preparing the signal for a subsequent evaluation.

4. The method of claim 3 , wherein the sensor comprises a photodiode.

5. The method of claim 3 , wherein the signal is evaluated in terms of one or more of a presence, formation, or a change of one or more of cracks, interruptions of seams, or errors in the weld seam.

6. The method of claim 3 , wherein the signal is prepared by one or more of a filtering, a noise reduction, or a smoothing.

7. The method of claim 3 , further comprising screening the radiation emitted by the process zone for a frequency of intensity fluctuations that is different from the pulse frequency of the processing beam.

8. The method of claim 3 , wherein two glass workpieces are welded together.

9. A device for monitoring a welding process for welding at least one glass workpiece to a further workpiece, the device comprising
a processing objective arranged to expose a process zone within at least one of the workpieces, or between the two workpieces, to an ultra-short-pulse laser processing beam to form a weld seam, wherein the weld seam is formed by a periodic formation of bubble-like regions of a plasma in the workpiece;
a sensor arranged and configured for time-resolved detection of radiation emitted by the process zone, wherein the sensor converts the radiation into a signal that is evaluated for one or more of a periodicity, a frequency, or a frequency spectrum of intensity fluctuations of the emitted radiation,
wherein the emitted radiation exhibits intensity fluctuations caused by the periodic expansion and collapse of the bubble-like regions of plasma in the workpiece, and
wherein the intensity fluctuations are independent of the pulse frequency of the laser processing beam; and

an imaging system arranged to capture radiation emitted by the process zone and to image the radiation onto the sensor,
wherein the device is configured to determine a quality of the weld seam based on one or more of a periodicity, a frequency, or a frequency spectrum of the intensity fluctuations of the detected radiation, wherein detection of a change in the periodicity, frequency, or frequency spectrum of the intensity fluctuations is indicative of an error in the weld seam; and to
provide an error output or a termination of the welding operation, or both, when the quality of the weld seam fails to meet predefined tolerance limits.

10. The device of claim 9 , wherein the sensor comprises a first sensor exposed with the processing objective, and a second sensor exposed with the imaging system.

11. The device of claim 10 , further comprising one or more of a beam splitter, an optical filter, or a focusing lens interposed between the first and second sensors.

12. The device of claim 9 , wherein the processing objective is configured and arranged to focus the processing beam into the process zone located in the glass volume formed by the at least one workpiece.

Assignees

• Trumpf Laser & Systemtechnik Gmbh

Inventors

• Hecker Sebastian
• Hesse Tim
• Scharun Michael
• Schindler Manuel
• Alber Kristian

Classifications

• B23K26/032 Primary

  using optical means · CPC title

• B23K31/12

  relating to investigating the properties, e.g. the weldability, of materials · CPC title

• B23K26/244

  Overlap seam welding · CPC title

• B23K26/0622

  by shaping pulses · CPC title

• B23K26/03

  Observing, e.g. monitoring, the workpiece · CPC title