Process for determining the instantaneous penetration depth and a machining laser beam into a workpiece, and device for implementing this process

• US 6,215,094 B1
• Filed: 05/28/1996
• Issued: 04/10/2001
• Est. Priority Date: 10/01/1993
• Status: Expired due to Term

• Current Assignee: Universitaet Stuttgart
• Original Assignee: Universitaet Stuttgart
• Inventors: Hack, Ruediger, Griebsch, Juergen, Dausinger, Friedrich
• Primary Examiner(s): Heinrich, Samuel M.
• Application Number:
  US08/619,599
• Time in Patent Office: 1,778 Days
• Field of Search: 219/121.61, 219/121.62, 219/121.63, 219/121.64, 219/121.7, 219/121.71, 219/121.76, 219/121.83
• US Class Current: 219/121.62
• CPC Class Codes: B23K 2103/16 Composite materials , e.g. fibre reinforced
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/0648 comprising lenses
• CPC Class Codes: B23K 26/0665 by beam condensation on the workpiece, e.g. for focusing
• CPC Class Codes: B23K 26/244 Overlap seam welding
• CPC Class Codes: B23K 26/382 by boring
• CPC Class Codes: B23K 26/389 of fluid openings, e.g. nozzles, jets laser machining of inkjet nozzles B41J2/1634
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved

Abstract

The penetration depth of a machining laser beam into workpiece is continuously monitored in that a measuring laser beam is directed onto the vapor capillary that is generated in the workpiece by the machining laser beam. The portion of the measuring laser beam that re-emerges from the vapor capillary is monitored by a sensor whose output signal is then used to bring about (producing holes) or to adjust (welding or superficial re-melting of a workpiece) the desired penetration depth defined by a pre-selected reference signal

Claims

1. Process for determining instantaneous penetration depth and achieving a desired penetration depth of a machining laser beam (9;

109) into a workpiece, comprising;

(a) determining in a preliminary trial the percentage portion of a measuring laser beam (9;

114) that re-emerges at the workpiece (1, 2;

101, 102) at the desired penetration depth;

(b) directing a laser beam (9;

114) performing the function of a measururing laser beam onto a vapour capillary (4;

104) formed in the workpiece (1, 2;

101, 102) by a laser beam (9;

109) performing the function of a machining laser beam,

(c) determining a portion of the laser beam performing the function of a measuring laser beam that re-emerges from the vapour capillary (4;

104) within said workpiece, following multiple reflections within said workpiece,

(d) in step (c) determining the percentage portion of the laser beam (9;

114) performing the function of a measuring laser beam that actually re-emerges at the workpiece (1, 2;

101, 102) and is not introduced into the workpiece (1, 2;

101, 102), and

(e) determining energy introduced into the workpiece (1, 2;

101, 102) per unit of time and area by the laser beam (9;

109) performing the function of a machining laser beam as a function of said portion of the laser beam (9, 114) performing the function of a measuring laser beam that was determined in step (c).

2. Process according to claim 1, characterized in that the same laser (8) is used to generate the machining laser beam (9) and the measuring laser beam (9).

3. Process according to claim 1, characterized in that two different lasers (108, 113) are used to generate the machining laser beam (109) and the measuring laser beam (114), wherein the wavelength of the measuring laser beam (114) is greater than that of the machining laser beam (109).

4. Process according to claim 1, in which a hole with a certain depth is achieved in a workpiece, further comprising:

a) determining in a preliminary trial the percentage portion of the measuring laser beam (9;

113) that re-emerges at the workpiece (1, 2;

101, 102) at the desired penetration depth of the hole;

monitoring the percentage of the measuring laser beam (9;

114) continuously while the machining laser beam (9;

109) making the hole in the workpiece (1, 2;

101, 102) is stationary, and and interrupting the machining laser beam (9;

109) when the percentage portion of the measuring laser beam (9;

114) that re-emerges has reached a value determined in the preliminary trial.

5. Process according to one of claim 1, in which a workpiece is melted open to a certain depth or a weld introduced in a workpiece to a certain depth, characterized in that

a) a preliminary trial determines the percentage portion of the measuring laser beam (9;

113) that is reflected at the workpiece (1, 2;

101, 102) at the desired depth (S) of the melt (5;

105);

b) the reflected percentage portion of the measuring laser beam (9;

114) is monitored continuously while the melt (5;

105) is being produced by the machining laser beam (9;

109) with a relative movement between machining laser beam (9;

109) and workpiece (1, 2;

101, 102) and deviations between the instantaneous reflected percentage portion of the measuring laser beam (9;

114) and the value determined in the preliminary trial are corrected by adjustment of the energy introduced into the workpiece (1, 2;

101, 102) by the machining laser beam (9;

109) per unit of time and area.

6. Process according to claim 5, characterized in that the adjustment is achieved by changing a power of the machining laser beam (9;

109).

7. Process according to claim 5, characterized in that the adjustment is undertaken by changing a relative speed between machining laser beam (9;

109) and workpiece (1, 2;

101, 102).

8. Process according to claim 5, characterized in that the adjustment takes place by de-focusing the machining laser beam (9, 109).