Process for checking a laser weld seam

• US 20050163364A1
• Filed: 01/07/2005
• Published: 07/28/2005
• Est. Priority Date: 01/07/2004
• Status: Active Grant

• Current Assignee: Daimler AG (Mercedes-Benz Group AG)
• Original Assignee: Daimler AG (Mercedes-Benz Group AG)
• Inventors: Beck, Markus, Herzinger, Thomas
• Granted Patent: US 7,620,233 B2
• Time in Patent Office: Days
• US Class Current: 382/152
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: G01N 21/4738 Diffuse reflection precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration, e.g. also for testing fluids, fibrous materials
• CPC Class Codes: G06T 2207/30152 Solder
• CPC Class Codes: G06T 7/0004 Industrial image inspection

Abstract

When laser beam welding one or more work pieces faults may occur, which lead to unacceptable losses in quality. For quality assurance, both subjective visual inspections as well as automated checks of the seam are the norm. In the automated processes the work site is conventionally monitored during welding using point or surface detectors (cameras). This type of process can not detect faults which do not occur until after the actual interaction of laser beam and work piece, in particular, solidification phenomena. Beyond this, certain irregularities relevant to quality are not recognized, since relevant process signals are overridden by stronger signals of the process illumination with no information value. It is the task of the present invention to provide a check process, which reliably recognizes seam faults. This task is solved in a process for checking of the seam which is introduced into one or more workpieces by means of laser beam welding, wherein characteristic signals are detected from the region of the seam using a sensor and compared with an index value or set value, and wherein only signals are taken into consideration which are detected in a characteristic time interval following the laser beam welding, which begins, at the earliest, following the solidification of the seam.

Claims

1. A process for checking a laser weld seam, comprising:

detecting characteristic signals from the area of the seam using a sensor and

comparing the detected signals with desired values,

wherein only signals detected within a characteristic time interval are taken into consideration, which characteristic time interval begins, at the earliest, after the solidification of the seam.

2. A process according to claim 1, wherein the characteristic time interval is defined depending upon the material characteristics of the workpiece and the process parameters of the laser beam.

3. A process according to claim 1, wherein detected signals of the optical and/or thermal type are emitted or reflected out from the area of the seam.

4. A process according to claim 1, wherein the signals are detected using a CCD-camera or a CMOS-camera.

5. A process according to claim 1, wherein at least during the characteristic time interval a measurement signal of the optical and/or thermal type is emitted in the direction of and onto the area of the seam.

6. A process according to claim 5, wherein the measurement signal is produced by the welding laser and is directed in the direction of and onto the seam via suitable beam deflection mechanisms, preferably a scanner device.