WO2006003361A1 - Method and apparatus for laser breakthrough detection - Google Patents

Method and apparatus for laser breakthrough detection Download PDF

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Publication number
WO2006003361A1
WO2006003361A1 PCT/GB2005/002173 GB2005002173W WO2006003361A1 WO 2006003361 A1 WO2006003361 A1 WO 2006003361A1 GB 2005002173 W GB2005002173 W GB 2005002173W WO 2006003361 A1 WO2006003361 A1 WO 2006003361A1
Authority
WO
WIPO (PCT)
Prior art keywords
laser
nozzle
pressure
control system
changes
Prior art date
Application number
PCT/GB2005/002173
Other languages
French (fr)
Inventor
Pamela Jean Byrd
Original Assignee
Rolls-Royce Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rolls-Royce Plc filed Critical Rolls-Royce Plc
Publication of WO2006003361A1 publication Critical patent/WO2006003361A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
    • B23K26/1462—Nozzles; Features related to nozzles
    • B23K26/1464—Supply to, or discharge from, nozzles of media, e.g. gas, powder, wire
    • B23K26/1476—Features inside the nozzle for feeding the fluid stream through the nozzle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
    • B23K26/142—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor for the removal of by-products
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
    • B23K26/1435—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor involving specially adapted flow control means
    • B23K26/1436—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor involving specially adapted flow control means for pressure control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
    • B23K26/1462—Nozzles; Features related to nozzles
    • B23K26/1488—Means for protecting nozzles, e.g. the tip surface
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
    • B23K26/1462—Nozzles; Features related to nozzles
    • B23K26/1494—Maintenance of nozzles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • B23K26/382—Removing material by boring or cutting by boring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • B23K26/382—Removing material by boring or cutting by boring
    • B23K26/389—Removing material by boring or cutting by boring of fluid openings, e.g. nozzles, jets

Definitions

  • the present invention relates to laser processing and in particular to determining breakthrough during drilling or cutting using a laser.
  • Laser processing of components is performed by high power laser beams, which are directed onto the component by an optical system appropriate for the application.
  • High power Nd:YAG or CO 2 lasers are often used for industrial drilling or cutting.
  • the laser beam may breakthrough one surface and impact on another, this is known as "far-wall strike' .
  • the apparatus used does not include a breakthrough detector then a penetration time has to be determined for the component. Breakthrough may however fail to occur if for example the material section of the component varies . Extra processing time must then be added to ensure breakthrough.
  • This extra time can be a significant proportion of the processing time for a component that requires many cuts or holes to be drilled.
  • the present invention seeks to provide a more reliable and simplified method and apparatus for detecting laser breakthrough.
  • a method for detecting the breakthrough of a laser beam through a surface comprising the steps of; positioning a pressure detector adjacent the nozzle, measuring the pressure of the gas in the nozzle, monitoring any changes in the pressure of the gas, and detecting when the pressure changes by a predetermined amount .
  • the method includes the further step of initiating a control system on detecting a pressure change.
  • the control system may switch off the laser, close the shutter, change the laser parameters or move the laser to prevent damage to other surfaces.
  • the laser beam is emitted from a laser having a nozzle through which a flow of gas passes characterised in that a pressure detector is mounted adjacent the nozzle and means are provided to monitor changes in the pressure detected by the pressure detector.
  • a signal processor is used to monitor the changes in pressure.
  • a control system may be provided which may switch off the laser, close the shutter, change the laser parameters or move the laser when a change in pressure is detected.
  • a laser has a nozzle through which a flow of gas passes characterised in that a pressure detector is provided adjacent the nozzle.
  • a nozzle suitable for use on a laser one end of the nozzle being adapted for engagement with the laser, at least one passageway being provided through the nozzle, whereby in operation a flow of gas passes therethrough and is emitted from the other end of the nozzle, a pressure detector being mounted on the nozzle to measure the pressure of the gas in the nozzle.
  • a laser 10 which is a high powered Nd:YAG or CO 2 laser, directs a laser beam 11 to a surface 16 of a component 17 to be drilled.
  • the laser beam 11 is focussed onto the surface 16 by optical elements 12 and 13.
  • the optical elements 12 and 13 focus the beam 11 through a nozzle 14 to deliver a narrow beam of laser energy to the surface 16.
  • the laser energy causes portions of the surface 16 to melt and vaporize.
  • a gas jet Coaxial to the laser beam 11 is a gas jet, indicated by arrows A in figure 1, which passes through the nozzle 14.
  • the type of gas used will depend on the application.
  • the gas used may be active, for example oxygen, to assist in the drilling process.
  • the gas may be passive, for example nitrogen, which acts as a shield to prevent oxidation.
  • the gas jet also acts to remove spatter from the surface 16 and prevent spatter from reaching the optical elements 12 and 13.
  • the gas is delivered at a pressure in the range 60-100 psi. The delivery pressure depends upon the application and the geometry of the component 17.
  • a pressure detector 18 mounted adjacent the nozzle 14.
  • the pressure detector 18 is connected to a signal monitor 20 and measures the pressure of the gas in the nozzle 14.
  • the pressure of the gas in the nozzle 14 is monitored over time. Natural variations in the supply pressure and the backpressure, from the impingement of the gas on the component 17, leads to fluctuations in the measured pressure.
  • a step change occurs in the pressure measured by the pressure detector. A change in the measured pressure of the order of 1-10% indicates that laser breakthrough has occurred.
  • a control system 22 is activated.
  • the control system 22 operates in a closed loop and initiates the next procedure in the machining process. The may be to switch the laser 10 off, close the shutter, change the laser parameters, or begin axial movement of the laser 10.
  • the operating pressure of the gas is immaterial to the working of the breakthrough device. It is the detection of a step change of the order of 1-10% in the measured pressure that indicates the breakthrough and initiates the control system 22.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Laser Beam Processing (AREA)

Abstract

A laser (10) directs a laser beam (11) onto a surface (16) of a component (17) to be drilled. Optical elements (12, 13) focus the beam (11) through a nozzle (14) Coaxial to the beam is a gas jet, which also passes through the nozzle (14). A pressure detector (18) is mounted adjacent the nozzle (14) and the gas pressure within the nozzle (14) is monitored. When a step change occurs in the gas pressure in the nozzle the laser beam (11) has broken through the surface (16) of the component (17) A control system (22) then initiates one of a number of changes to minimise damage to other surfaces.

Description

METHOD AND APPARATUS FOR LASER BREAKTHROUGH DETECTION
The present invention relates to laser processing and in particular to determining breakthrough during drilling or cutting using a laser.
Laser processing of components is performed by high power laser beams, which are directed onto the component by an optical system appropriate for the application. High power Nd:YAG or CO2 lasers are often used for industrial drilling or cutting.
It is desirable to know when the laser beam has broken through the component to prevent damage to the supporting surface below. For some components, the laser may breakthrough one surface and impact on another, this is known as "far-wall strike' .
If the apparatus used does not include a breakthrough detector then a penetration time has to be determined for the component. Breakthrough may however fail to occur if for example the material section of the component varies . Extra processing time must then be added to ensure breakthrough.
This extra time can be a significant proportion of the processing time for a component that requires many cuts or holes to be drilled.
Different methods of detecting laser breakthrough in a component have been tried and developed. These include the detection of laser light that has been reflected back after breakthrough. This technique however involves the accurate positioning of an optical detector to monitor the reflected light. Accurate positioning of the optical detector is a problem and spurious reflections can occur from other surfaces of the component if it has a complex geometry. The amount of light reflected is therefore not always a reliable indication that breakthrough has occurred.
The present invention seeks to provide a more reliable and simplified method and apparatus for detecting laser breakthrough.
According to one aspect of the present invention a method for detecting the breakthrough of a laser beam through a surface, the laser beam being emitted from a laser having a nozzle through which a flow of gas passes therethrough, the method comprising the steps of; positioning a pressure detector adjacent the nozzle, measuring the pressure of the gas in the nozzle, monitoring any changes in the pressure of the gas, and detecting when the pressure changes by a predetermined amount .
When a step change in the pressure is detected breakthrough has occurred. If the pressure changes by the order of 1-10% then breakthrough has occurred.
Preferably the method includes the further step of initiating a control system on detecting a pressure change.
The control system may switch off the laser, close the shutter, change the laser parameters or move the laser to prevent damage to other surfaces.
In a second aspect of the present invention apparatus for detecting the breakthrough of a laser beam through a surface, the laser beam is emitted from a laser having a nozzle through which a flow of gas passes characterised in that a pressure detector is mounted adjacent the nozzle and means are provided to monitor changes in the pressure detected by the pressure detector.
In the preferred embodiment of the present invention a signal processor is used to monitor the changes in pressure. A control system may be provided which may switch off the laser, close the shutter, change the laser parameters or move the laser when a change in pressure is detected.
In a third aspect of present invention a laser has a nozzle through which a flow of gas passes characterised in that a pressure detector is provided adjacent the nozzle.
In a fourth aspect of the present invention a nozzle suitable for use on a laser, one end of the nozzle being adapted for engagement with the laser, at least one passageway being provided through the nozzle, whereby in operation a flow of gas passes therethrough and is emitted from the other end of the nozzle, a pressure detector being mounted on the nozzle to measure the pressure of the gas in the nozzle. The present invention will now be described with reference to figure 1 which shows apparatus for detecting the breakthrough of a laser beam through a surface of a component in accordance with the present invention. Referring to the drawing a laser 10, which is a high powered Nd:YAG or CO2 laser, directs a laser beam 11 to a surface 16 of a component 17 to be drilled. The laser beam 11 is focussed onto the surface 16 by optical elements 12 and 13. The optical elements 12 and 13 focus the beam 11 through a nozzle 14 to deliver a narrow beam of laser energy to the surface 16. The laser energy causes portions of the surface 16 to melt and vaporize.
Coaxial to the laser beam 11 is a gas jet, indicated by arrows A in figure 1, which passes through the nozzle 14. The type of gas used will depend on the application. The gas used may be active, for example oxygen, to assist in the drilling process. Alternatively the gas may be passive, for example nitrogen, which acts as a shield to prevent oxidation. The gas jet also acts to remove spatter from the surface 16 and prevent spatter from reaching the optical elements 12 and 13. The gas is delivered at a pressure in the range 60-100 psi. The delivery pressure depends upon the application and the geometry of the component 17.
To prevent damage to other surfaces (not shown) of the component 17 it is necessary to detect the moment the laser beam 11 breaks through. This is achieved by the use of a pressure detector 18 mounted adjacent the nozzle 14. The pressure detector 18 is connected to a signal monitor 20 and measures the pressure of the gas in the nozzle 14. The pressure of the gas in the nozzle 14 is monitored over time. Natural variations in the supply pressure and the backpressure, from the impingement of the gas on the component 17, leads to fluctuations in the measured pressure. However when the laser beam 11 breaks through the component 17 a step change occurs in the pressure measured by the pressure detector. A change in the measured pressure of the order of 1-10% indicates that laser breakthrough has occurred. When a step change in the pressure is detected a control system 22 is activated. The control system 22 operates in a closed loop and initiates the next procedure in the machining process. The may be to switch the laser 10 off, close the shutter, change the laser parameters, or begin axial movement of the laser 10.
The operating pressure of the gas is immaterial to the working of the breakthrough device. It is the detection of a step change of the order of 1-10% in the measured pressure that indicates the breakthrough and initiates the control system 22.

Claims

Claims ;
1. A method of detecting the breakthrough of a laser beam (11) through a surface (16) , the laser beam (11) being emitted from a laser having a nozzle (14) through which a flow of gas passes therethrough, the method comprising the steps of; positioning a pressure detector (18) adjacent the nozzle (14) , measuring the pressure of the gas in the nozzle, monitoring any changes in the pressure of the gas, and detecting when the pressure changes by a predetermined amount .
2. A method as claimed in claim 1 characterised in that the method further includes the step of initiating a control system (22) on detecting a pressure change.
3. A method as claimed in claim 2 characterised in that a change in the measured pressure of the order of 1-10% initiates the control system (22) .
4. A method as claimed in claim 2 or claim 3 characterised in that the control system (22) switches off the laser (10) .
5. A method as claimed in claim 2 or claim 3 characterised in that the control system (22) closes a shutter on the laser (10) .
6. A method as claimed in claim 2 or claim 3 characterised in that the control system (22) changes the lasers parameters (10) .
7. A method as claimed in claim 2 or claim 3 characterised in that the control system (22) moves the laser (10) .
8. Apparatus for detecting the breakthrough of a laser beam
(11) through a surface (16) , the laser beam (11) being emitted from a laser (10) having a nozzle (14) through which a flow of gas passes characterised in that a pressure detector (18) is mounted adjacent the nozzle (14) and means (20) are provided to monitor changes in the pressure detected by the pressure detector (18) .
9. Apparatus as claimed in claim 8 characterised in that a signal processor (20) is used to monitor the changes in pressure.
10. Apparatus as claimed in claim 8 or claim 9 characterised in that a control system (22) is provided to initiate changes when a change in pressure is detected.
11. Apparatus as claimed in claim 10 characterised in that the control system (22) switches off the laser (10) .
12. Apparatus as claimed in claim 10 characterised in that the control system (22) closes a shutter on the laser (10) .
13. Apparatus as claimed in claim 10 characterised in that the control system (22) changes the lasers (10) parameters.
14. Apparatus as claimed in claim 10 characterised in that the control system (22) moves the laser (10) .
15. A laser (10) having a nozzle (14) through which a flow of gas passes characterised in that a pressure detector (18) is provided adjacent the nozzle (14) .
16. A nozzle (14) suitable for use on a laser (10) , one end of the nozzle (14) being adapted for engagement with the laser (10) , at least one passageway being provided through the nozzle (14) , whereby in operation a flow of gas passes therethrough and is emitted from the other end of the nozzle (14) , a pressure detector (18) being mounted on the nozzle (14) to measure the pressure of the gas in the nozzle (14) .
PCT/GB2005/002173 2004-07-06 2005-06-03 Method and apparatus for laser breakthrough detection WO2006003361A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB0415096.7A GB0415096D0 (en) 2004-07-06 2004-07-06 Method and apparatus for laser breakthrough detection
GB0415096.7 2004-07-06

Publications (1)

Publication Number Publication Date
WO2006003361A1 true WO2006003361A1 (en) 2006-01-12

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GB (1) GB0415096D0 (en)
WO (1) WO2006003361A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013037825A1 (en) * 2011-09-14 2013-03-21 Trumpf Werkzeugmaschinen Gmbh + Co. Kg Universal nozzle for a laser cutting machine and method for adjusting the universal nozzle in a laser cutting machine

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5089685A (en) * 1989-12-21 1992-02-18 Robert Bosch Gmbh Method of and arrangement for measuring the size of throughgoing openings
EP0713745A1 (en) * 1994-11-15 1996-05-29 ROLLS-ROYCE plc A method and apparatus for producing apertured components
EP1118419A2 (en) * 2000-01-19 2001-07-25 General Electric Company Method of forming cooling holes

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5089685A (en) * 1989-12-21 1992-02-18 Robert Bosch Gmbh Method of and arrangement for measuring the size of throughgoing openings
EP0713745A1 (en) * 1994-11-15 1996-05-29 ROLLS-ROYCE plc A method and apparatus for producing apertured components
EP1118419A2 (en) * 2000-01-19 2001-07-25 General Electric Company Method of forming cooling holes

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013037825A1 (en) * 2011-09-14 2013-03-21 Trumpf Werkzeugmaschinen Gmbh + Co. Kg Universal nozzle for a laser cutting machine and method for adjusting the universal nozzle in a laser cutting machine
CN103826792A (en) * 2011-09-14 2014-05-28 通快机床两合公司 Universal nozzle for laser cutting machine and method for adjusting universal nozzle in laser cutting machine

Also Published As

Publication number Publication date
GB0415096D0 (en) 2004-08-04

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