GB2218660A - Method of material processing using a laser beam - Google Patents

Method of material processing using a laser beam Download PDF

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Publication number
GB2218660A
GB2218660A GB8811533A GB8811533A GB2218660A GB 2218660 A GB2218660 A GB 2218660A GB 8811533 A GB8811533 A GB 8811533A GB 8811533 A GB8811533 A GB 8811533A GB 2218660 A GB2218660 A GB 2218660A
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United Kingdom
Prior art keywords
method
pulse
material processing
sub
laser beam
Prior art date
Legal status (The legal status 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 status listed.)
Granted
Application number
GB8811533A
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GB2218660B (en
GB8811533D0 (en
Inventor
Geoffrey Howard Lucas
Peter Glenn Thompson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Lumonics Ltd
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Lumonics Ltd
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 Lumonics Ltd filed Critical Lumonics Ltd
Priority to GB8811533A priority Critical patent/GB2218660B/en
Publication of GB8811533D0 publication Critical patent/GB8811533D0/en
Publication of GB2218660A publication Critical patent/GB2218660A/en
Application granted granted Critical
Publication of GB2218660B publication Critical patent/GB2218660B/en
Anticipated expiration legal-status Critical
Application status is Expired - Lifetime legal-status Critical

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/0604Shaping the laser beam, e.g. by masks or multi-focusing by a combination of beams
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/062Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
    • B23K26/0622Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00Materials to be soldered, welded or cut
    • B23K2103/02Iron or ferrous alloys
    • B23K2103/04Steel or steel alloys
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00Materials to be soldered, welded or cut
    • B23K2103/02Iron or ferrous alloys
    • B23K2103/04Steel or steel alloys
    • B23K2103/05Stainless steel

Abstract

An output beam from a laser, for example an Nd-YAG laser, is directed on to a workpiece, for example steel sheet. In order to perform a material processing operation, eg cutting, drilling, milling or welding one or more laser beam pulses are applied to the workpiece. Each pulse is divided into n sub-pulses having power amplitudes A1, A2, ... An and durations t1, t2, ... tn. The sub-pulses are separated by intervals having amplitudes B1, B2... Bn-1 and duration T1, T2, ... Tn-1. The invention may be achieved when the following conditions are observed: (B1/A1), (B2/A2),...(Bn-1/An-1) </= 0.5 0.1 ms </= ti </= 1.0 ms 0.1 ms </= Ti </= 1.0 ms 3 </= n </= 20 <IMAGE>

Description

METHOD OF ERIAL PROCESSING USING A LASER BEAM This invention relates to a method of performing a material processing operation on a workpiece using a laser beam and particularly, but not exclusively, to performing a drilling or cutting operation using a laser beam.

In one method of performing a material processing operation using a laser beam, one or more laser beam pulses are applied to a workpiece.

Typically, the duration of each of the pulses is several milliseconds. Such operations include drilling, cutting, milling and welding. It is desirable that a particular operation is achieved as quickly as possible while achieving excellent process quality. In the case of drilling, the quality of the resulting hole may be judged by the closeness of the hole to a desired geometry and also by the absence of a recast layer on the wall of the hole and the absence of debris and burrs at the entry and exit faces of the hole.

It is accordingly an object of this invention to provide a new or improved method of performing a material processing operation using a laser beam in which the period for performing the operation is reduced and/or an improved process quality is achieved.

According to this invention, there is provided a method of performing a material processing operation on a workpiece using a laser beam, said method comprising the steps of directing a laser beam onto a workpiece, dividing said laser beam into one or more pulses, and modulating the or each pulse so as to form a plurality of sub-pulses, wherein the duration of each sub-pulse lies in the range O. 4 to 1.0 milliseconds, the duration of the interval between each pair of neighbouring sub-pulses lies in the range 0.1 to 1.0 milliseconds, the number of subpulses in each pulse lies in the range 3 to 20, and the ratio of the average power of the laser beam during each interval between a pair of sub-pulses to its average power during the immediately preceding sub-pulse is equal to, or less than, 0.5.

With the method of the present invention, it has been found that a material processing operation may be performed in a shorter period and that an improved process quality may be achieved.

The duration of each sub-pulse may lie in the range 0.3 to 0.6 milliseconds.

The ratio of the average power of the laser beam during each interval between a pair of subpulses to the average power during the immediately preceding sub-pulse may be substantially zero.

Each pulse may have an approximately rectangular envelope or an approximately triangular envelope.

The method may comprise a further step of supplying a process assisting gas, for example, oxygen to the position where the material processing operation is performed. The material processing operation may be performed on metal sheet, for example, steel sheet.

The material processing operation may be cutting, drilling, milling or welding.

Preferably, the laser beam is produced in-a laser which uses neodymium doped yttrium aluminium garnet as its active material.

This invention will now be described in more detail, by way of example, with reference to the drawings in which: Figure 1 is a block diagram of a laser apparatus for performing a material processing operation in accordance with the invention; Figure 2a shows the waveform of a pulse used in the method of the invention; Figure 2b shows the waveform of a pulse used in a conventional method of material processing using a laser beam; Figure 3 shows various pulse envelopes that may be used in the method of the invention; Figure 4 shows the waveform of another pulse used in the method of the invention; and Figure 5 indicates the generalised form for the waveform of a pulse used in the method of the invention.

Referring now to Figure 1, the apparatus comprises a Nd-YAG (neodymiun doped yttrium aluminium garnet) laser 10 which generates a laser beam 11.

The beam 11 is deflected by a mirror 12 to a focusing device in the form of a lens 13 which focuses the beam onto a workpiece 14 for performing a drilling operation. In the present example, the workpiece 14 is metal sheet. A process assisting gas is supplied to the inlet of a nozzle 15 and nozzle 15 directs the assisting gas to the position where the operation is performed. the assisting gas aids the removal of metal. In the apparatus presently described, oxygen is used as the assisting gas but other gases, for example compressed air, may be used in place of oxygen. The present invention may also be performed without using an asissting gas.

In the present example, the laser 10 is a type JK704a pulsed Nd-YAG laser produced by tumonics Ltd, Rugby, England. This laser uses a power supply which is described in the United States Patent 4 276 497. This power supply has the capability of supplying current pulses of a desired shape to the laser flashlamps so as to achieve laser beam pulses of a desired shape. The shape of the pulses may be programmed as required by the user. This laser has the facility of programming pulses with up to 20 consecutive time elements. For each time element, the lamp current and the duration of the time element may be specified.

When using the laser apparatus 10 to perform a drilling operation, in accordance with the invention one or more laser beam pulses are applied to the workpiece and each individual pulse is modulated so as to form a plurality of sub-pulses.

In comparison with using unmodulated pulses, holes may be formed in a shorter period and with a higher process quality. This method will now be illustrated by two examples of drilling operations performed using the laser apparatus 10.

In the first example, the drilling operation was performed on type 304 stainless steel having a thickness of 15mm. Oxygen was supplied to the nozzle 15 at a pressure of 60psi (414kPa) and the focal length of the lens 13 was 300mum.

In this example, two tests were performed.

In the first test, each pulse had a waveform as shown in Figure 2a. As may be seen, each pulse was divided into five sub-pulses 18 of equal power amplitude and of duration t. The five sub-pulses were separated by intervals of equal duration T and, during these intervals, the amplitude of the laser beam was negligible. The specific parameters for the first test were as follows: number of sub-pulses 5 t 0.6ms T 0.5ms total on-time (5t) .ohms total pulse duration 5.0ms total pulse energy 55J pulse rate 5.3Hz time to drill hole 4.5 seconds beam energy to drill hole 1312J In the second test, which was performed to make a comparison between using modulated and unmodulated pulses, each pulse had a waveform as shown in Figure 2b. As may be seen, these pulses have a rectangular shape and a duration P.The specific parameters for the second test were as follows: pulse duration (P) 2.6ms pulse energy 58 J pulse rate 5Hz time to drill hole 7.5 seconds beam energy to drill hole 2175J The parametersin the second were optimised to achieve the shortest drilling time.

By comparing these two tests, it may be seen that by using modulated pulses the time required to drill a hole is reduced by 40# and the total pulse energy is also reduced.

In the example described with reference to Figure 2a, each pulse has a rectangular envelope.

However, the present invention is not limited to this particular envelope and, for a particular drilling operation, the optimum envelope shape will depend upon desired characteristics such as hole quality or drilling speed. In Figures 3a to 3e, there are shown five possible envelope shapes. In Figure 3a, there is shown the rectangular shape which has already been discussed. In Figures 3b and 3c, there are shown two saw-tooth shapes and a triangular shape is shown in Figure 3d. In Figure 3e, there is shown a rectangular shape modified by transition periods following the leading edge and preceding the trailing edge.

In the second example, the laser apparatus 10 was used to form holes in C263 NimonicXalioy having a thickness of 4mm. Oxygen was supplied to nozzle 15 at a pressure of 75 psi (517kPa) and the focal length of the lens 13 was 120mm. The energy of each pulse was 13.5J and the pulse repetition rate was 9fez.

In this second example, four pulse envelopes were assessed, these four envelopes being those shown in Figures 3a to 3d. It was found that the triangular envelope shown in Figure 3d produced holes which were nearest to being cylindrical. Each hole required five pulses.

The waveform that was used is shown in Figure 4. As may be seen, each pulse was divided into 5 sub-pulses 21 to 25 having power amplitudes A1 to A5. These 5 sub-pulses 21 to 25 define an approximately triangular envelope 26. Each sub-pulse had an interval t and the intervals between the subpulses had a duration T. In these intervals, the amplitude of the laser beam was negligible. The specific parameters of the waveform were as follows: A1 = A5 = 55% A2 = A4 = 80 A3 = 100% t = 0.3ms T = 0.5ms Amplitudes A1 to A5 are given relative to an absolute level.

As mentioned above, for each pulse the optimum envelope shape depends upon the desired characteristics of the drilling operation. The generalised form for the pulse envelope is shown in Figure 5. Each pulse is divided into a plurality of sub-pulses 28 having power amplitudes A1, A2,...An and durations t1, t2,...tn. The sub-pulses 28 are separated by intervals having power amplitudes B1, B2, ...Bn-1 and intervals T1, T2,...Tn-1 In general, the invention may be achieved with the waveform shown in Figure 5 providing the following conditions are observed:: (B1/A1), (B2/A2),... (3n-1/An 0.5 0.lms < ti L 1.Oms O.lms o Ti 1.Oms D L n C 20 Thus, the present invention may be achieved providing each pulse is divided into a plurality of sub-pulses, the duration of each sub-pulse lying in the range 0.1 to 1.0 milliseconds, the duration of the interval between each pair of neighbouring subpulses lying in the range between 0.1 to 1.0 milliseconds, the number of sub-pulses lying in the range 3 to 20, and the ratio of the average power of the laser beam during each interval between the pair of sub-pulses to its average power during the immediately preceding sub-pulse being equal to, or less than, 0.5.

Also, although in the examples described above, the invention is used to drill holes, the present invention may be used for other material processing operations. For example, the present invention may be used for a cutting operation or for a milling operation or a welding operation.

In the laser apparatus 10, the individual pulses are modulated by modulating the lamp current.

This method of modulation may be achieved without loss of energy and so represents the best method for performing the present invention. However, the present invention may also be performed by using an intracavity or an extra cavity optical shutter, such as a Pockels cell, to provide modulated pulses.

Although in the apparatus described above a Nd:YAG laser is used, the present invention may be achieved with other types of lasers.

Claims (15)

1. A method of performing a material processing operation on a workpiece using a laser beam, said method comprising the steps of directing a laser beam on to a workpiece, dividing said laser beam into one or more pulses, and modulating the or each pulse so as to form a plurality of sub-pulses, wherein the duration of each sub-pulse lies in the range 0.1 to 1.0 milliseconds, the duration of the interval between each pair of neighbouring sub-pulses lies in the range 0.1 to 1.0 milliseconds, the number of sub-pulses in each pulse lies in the range 3 to 20, and the ratio of the average power of the laser beam during each interval between a pair of subpulses to its average power during the immediately preceding sub-pulse is equal to, or less than, 0.5.
2. A method as claimed in Claim 1, in which the duration of each sub-pulse lies in the range 0.3 to 0.6 milliseconds.
3. A method as claimed in Claim 1 or Claim 2, in which the ratio of the average power of the laser beam during each interval between a pair of subpulses to the average power during the immediately preceding sub-pulse is substantially zero.
4. A method as claimed in any one of the preceding claims in which each pulse has an approximately rectangular envelope.
5. A method as claimed in any one of Claims 1 to 3, in which each pulse has an approximately triangular envelope.
6. A method as claimed in any one of the preceding claims, comprising the further step of supplying a process assisting gas to the position where the material processing operation is performed.
7. A method as claimed in Claim 6, in which the process assisting gas is oxygen.
8. A method as claimed in any one of the preceding claims, in which the material processing operation is performed on metal sheet.
9. A method as claimed in Claim 8, in which the material processing operation is performed on steel sheet.
10. A method as claimed in any one of the preceding claims, in which the material processing operation is cutting.
11. A method as claimed in any one of Claims 1 to 9, in which the material processing operation is drilling.
12. A method as claimed in any one of Claims 1 to 9, in which the material processing operation is milling.
13. A method as claimed in any one of Claims 1 to 9, in which the material processing operation is welding.
14. A method as claimed in any one of the preceding claims, in which the laser beam is produced in a laser which uses neodymium doped yttrium aluminium garnet as its active material.
15. A method of performing a material processing operation on a workpiece using a laser beam substantially as hereinbefore described with reference to Figures 1 and 5, or Figures 1, 2a and 3a, or Figures 1, 3d and 4, or Figures 1 and 3b, or Figures 1 and 3c, or Figures 1 and 3e of the accompanying drawings.
GB8811533A 1988-05-16 1988-05-16 Method of material processing using a laser beam Expired - Lifetime GB2218660B (en)

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GB8811533D0 GB8811533D0 (en) 1988-06-22
GB2218660A true GB2218660A (en) 1989-11-22
GB2218660B GB2218660B (en) 1991-09-25

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0563406A1 (en) * 1991-10-19 1993-10-06 Fanuc Ltd. Method of laser piercing
EP0564995A1 (en) * 1992-04-03 1993-10-13 Mitsui Petrochemical Industries, Ltd. Pulse laser irradiation apparatus for coated metal material
EP0937534A2 (en) * 1998-02-24 1999-08-25 Miyachi Technos Corporation Laser processing apparatus
US6130900A (en) * 1999-03-05 2000-10-10 Coherent, Inc. Pulsed intracavity frequency-converted solid-state laser with long-pulse simulation
DE19920813A1 (en) * 1999-05-06 2001-06-28 Bosch Gmbh Robert An apparatus for removing material on workpieces by means of laser beam
EP1132168A2 (en) * 2000-03-10 2001-09-12 Ishikawajima- Harima Heavy Industries Co., Ltd. Laser welding method
WO2002051580A1 (en) * 2000-12-22 2002-07-04 Koninklijke Philips Electronics N.V. Method of laser welding
WO2007022948A3 (en) * 2005-08-22 2007-05-10 Rowiak Gmbh Device and method for material separation using laser pulses, the energy of one of which is less than the energy of a laser pulse used for separating material
EP2209583A1 (en) * 2007-11-06 2010-07-28 Yura Tech CO., LTD. Method for welding tip of electrode in spark plug
US8221400B2 (en) 2005-08-22 2012-07-17 Sie Surgical Instruments Engineering Ag Apparatus for and method of refractive surgery with laser pulses
CN104227235A (en) * 2013-06-14 2014-12-24 日立汽车系统株式会社 Laser welding method, welding component, fuel injection valve

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0563406A4 (en) * 1991-10-19 1994-05-04 Fanuc Ltd.
US5434383A (en) * 1991-10-19 1995-07-18 Fanuc Ltd. Piercing method for laser processing
EP0563406A1 (en) * 1991-10-19 1993-10-06 Fanuc Ltd. Method of laser piercing
EP0564995A1 (en) * 1992-04-03 1993-10-13 Mitsui Petrochemical Industries, Ltd. Pulse laser irradiation apparatus for coated metal material
US5347528A (en) * 1992-04-03 1994-09-13 Mitsui Petrochemical Industries, Ltd. Pulse laser irradiation apparatus for coated metal material
EP0937534A3 (en) * 1998-02-24 2001-07-11 Miyachi Technos Corporation Laser processing apparatus
EP0937534A2 (en) * 1998-02-24 1999-08-25 Miyachi Technos Corporation Laser processing apparatus
US6130900A (en) * 1999-03-05 2000-10-10 Coherent, Inc. Pulsed intracavity frequency-converted solid-state laser with long-pulse simulation
DE19920813A1 (en) * 1999-05-06 2001-06-28 Bosch Gmbh Robert An apparatus for removing material on workpieces by means of laser beam
EP1132168A2 (en) * 2000-03-10 2001-09-12 Ishikawajima- Harima Heavy Industries Co., Ltd. Laser welding method
EP1132168A3 (en) * 2000-03-10 2002-05-29 Ishikawajima- Harima Heavy Industries Co., Ltd. Laser welding method
US6576864B2 (en) 2000-12-22 2003-06-10 Koninklijke Philips Electronics N.V. Method of laser welding
WO2002051580A1 (en) * 2000-12-22 2002-07-04 Koninklijke Philips Electronics N.V. Method of laser welding
WO2007022948A3 (en) * 2005-08-22 2007-05-10 Rowiak Gmbh Device and method for material separation using laser pulses, the energy of one of which is less than the energy of a laser pulse used for separating material
US9162319B2 (en) 2005-08-22 2015-10-20 Rowiak Gmbh Method and device for the removal of material by means of laser pulses
US8221400B2 (en) 2005-08-22 2012-07-17 Sie Surgical Instruments Engineering Ag Apparatus for and method of refractive surgery with laser pulses
US8758331B2 (en) 2005-08-22 2014-06-24 Sie Surgical Instruments Engineering Ag Apparatus for and method of refractive surgery with laser pulses
EP2209583A4 (en) * 2007-11-06 2010-11-17 Yura Tech Co Ltd Method for welding tip of electrode in spark plug
US8471174B2 (en) 2007-11-06 2013-06-25 Yura Tech Co., Ltd. Method for welding tip of electrode in spark plug
EP2209583A1 (en) * 2007-11-06 2010-07-28 Yura Tech CO., LTD. Method for welding tip of electrode in spark plug
CN104227235A (en) * 2013-06-14 2014-12-24 日立汽车系统株式会社 Laser welding method, welding component, fuel injection valve
CN104227235B (en) * 2013-06-14 2016-05-11 日立汽车系统株式会社 Method for laser welding, welded unit and Fuelinjection nozzle

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Publication number Publication date
GB2218660B (en) 1991-09-25
GB8811533D0 (en) 1988-06-22

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PE20 Patent expired after termination of 20 years

Expiry date: 20080515