Method and apparatus for laser cutting materials

• US 6,163,010 A
• Filed: 04/24/1998
• Issued: 12/19/2000
• Est. Priority Date: 10/25/1996
• Status: Expired due to Fees

• Current Assignee: Invista North America Sarl (Invista)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Kobsa, Henry
• Primary Examiner(s): Heinrich, Samuel M.
• Application Number:
  US09/269,494
• Time in Patent Office: 970 Days
• Field of Search: 219/121.6, 219/121.61, 219/121.62, 219/121.67, 219/121.82, 219/121.84
• US Class Current: 219/121.61
• CPC Class Codes: B23K 2103/05 Stainless steel
• CPC Class Codes: B23K 2103/10 Aluminium or alloys thereof
• CPC Class Codes: B23K 2103/12 Copper or alloys thereof
• CPC Class Codes: B23K 2103/172 wherein at least one of the layers is non-metallic
• CPC Class Codes: B23K 2103/38 Fabrics, fibrous materials
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 2103/52 Ceramics
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/06 Shaping the laser beam, e.g. by masks or multi-focusing
• CPC Class Codes: B23K 26/0626 Energy control of the laser beam B23K26/0622 takes precedence
• CPC Class Codes: B23K 26/064 by means of optical elements, e.g. lenses, mirrors or prisms
• CPC Class Codes: B23K 26/0643 comprising mirrors
• 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 26/123 in an atmosphere of particular gases
• CPC Class Codes: B23K 26/14 using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor B23K26/12 takes precedence
• CPC Class Codes: B23K 26/1435 involving specially adapted flow control means
• CPC Class Codes: B23K 26/1436 for pressure control
• CPC Class Codes: B23K 26/1462 Nozzles; Features related to nozzles
• CPC Class Codes: B23K 26/1476 Features inside the nozzle for feeding the fluid stream through the nozzle
• CPC Class Codes: B23K 26/40 : taking account of the properties of the material involved

Abstract

Laser cutting of workpieces according to prior art results in heat affected zones (HAZ) of signiftcant thickness at the cut surface, which show seriously disturbed texture and/or microcracks. The HAZ is diminished by using a laser system with high beam quality and high brightness.

Claims

1. A laser based system for precision processing and machining of materials, comprising

(a) a pulsed solid state laser, comprising,

(i) a laser cavity defined by two end mirrors,

(ii) a laser medium;

(iii) a cylindrical laser rod directly side-pumped by a plurality of arrays of laser diode, and

(iv) at least one optical element for improving the beam quality,

(b) a laser beam delivery system for expanding, collimating, and focusing the laser beam;

(c) a workstation for holding and moving a workpiece with respect to the laser beam;

(d) a cutting nozzle for directing a jet of a pressurized fluid to the surface of said workpiece;

wherein the laser beam has an average power from about 2 to about 100 watts and the focused laser beam has an average brightness of more than 10¹² W/m² *sr and a peak brightness of more than 10¹³ W/m² *sr.

2. The system of claim 1, wherein the solid state laser medium is neodymium-doped yttrium aluminum garnet (Nd:

YAG).

3. The system of claim 1, further comprising a continuously variable beam splitter external to the laser cavity.

4. The system of claim 1, further comprising a beam sampler in the optical path, and a laser beam quality monitor, said beam sampler directing a minor fraction of the beam to a laser beam quality monitor.

5. The system of claim 4, wherein the laser beam quality monitor comprises a CCD camera assembly having a planar CCD array, a focus control unit and an image processor/control unit wherein the portion of the laser beam energy passing through the beam sampler passes through the focus control unit and is focused onto the planar CCD array to generate an image of the laser beam for monitoring laser beam quality.

6. The system of claim 1, further comprising a distance sensor fixed to the laser beam delivery system, which generates an input to the workstation, which controls the distance between the focusing lens and the surface of the material.