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GB2045669A - Method of microdrilling metal workpiece using a power laser - Google Patents

Method of microdrilling metal workpiece using a power laser Download PDF

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Publication number
GB2045669A
GB2045669A GB8004739A GB8004739A GB2045669A GB 2045669 A GB2045669 A GB 2045669A GB 8004739 A GB8004739 A GB 8004739A GB 8004739 A GB8004739 A GB 8004739A GB 2045669 A GB2045669 A GB 2045669A
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GB
United Kingdom
Prior art keywords
workpiece
hole
liquid
laser
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
GB8004739A
Other versions
GB2045669B (en
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.)
Fiat Auto SpA
Original Assignee
Fiat Auto SpA
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Filing date
Publication date
Application filed by Fiat Auto SpA filed Critical Fiat Auto SpA
Publication of GB2045669A publication Critical patent/GB2045669A/en
Application granted granted Critical
Publication of GB2045669B publication Critical patent/GB2045669B/en
Expired legal-status Critical Current

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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
    • B23K26/14Working 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
    • B23K26/1462Nozzles; Features related to nozzles
    • B23K26/1464Supply to, or discharge from, nozzles of media, e.g. gas, powder, wire
    • B23K26/147Features outside the nozzle for feeding the fluid stream towards the workpiece
    • 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
    • B23K10/00Welding or cutting by means of a plasma
    • B23K10/003Scarfing, desurfacing or deburring
    • 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
    • B23K26/12Working by laser beam, e.g. welding, cutting or boring in a special atmosphere, e.g. in an enclosure
    • B23K26/123Working by laser beam, e.g. welding, cutting or boring in a special atmosphere, e.g. in an enclosure in an atmosphere of particular gases
    • 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
    • B23K26/14Working 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
    • B23K26/142Working 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
    • 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
    • B23K26/14Working 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
    • B23K26/1435Working 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
    • 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
    • B23K26/14Working 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
    • B23K26/1435Working 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
    • B23K26/1438Working 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 directional control
    • 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
    • B23K26/36Removing material
    • B23K26/38Removing material by boring or cutting
    • B23K26/382Removing material by boring or cutting by boring
    • 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
    • B23K26/36Removing material
    • B23K26/38Removing material by boring or cutting
    • B23K26/382Removing material by boring or cutting by boring
    • B23K26/389Removing material by boring or cutting by boring of fluid openings, e.g. nozzles, jets
    • 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
    • B23K26/36Removing material
    • B23K26/40Removing material taking account of the properties of the material involved
    • 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
    • B23K26/60Preliminary treatment
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M61/00Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
    • F02M61/16Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
    • F02M61/168Assembling; Disassembling; Manufacturing; Adjusting
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M61/00Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
    • F02M61/16Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
    • F02M61/18Injection nozzles, e.g. having valve seats; Details of valve member seated ends, not otherwise provided for
    • F02M61/1806Injection nozzles, e.g. having valve seats; Details of valve member seated ends, not otherwise provided for characterised by the arrangement of discharge orifices, e.g. orientation or size
    • 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
    • B23K2103/50Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Engineering (AREA)
  • Plasma & Fusion (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Laser Beam Processing (AREA)

Abstract

A laser microdrilling method uses a power laser beam (3) the action of which causes solid workpiece metal (1) to be transformed into both liquid and vapour phases. In order to improve the surface finish and dimensional accuracy of a hole (4) formed, the workpiece (1) is heated to a temperature sufficient to cause both the liquid phase formed directly by the action of the laser beam (3) and the liquid phase caused by the condensation of the vapour phase on the wall of the hole being formed (4), to be maintained in the liquid state for a period of time long enough to permit the uniform spreading of these liquid phases over the wall of the hole (4). For a plate workpiece, the ends are clamped to conductors from a high frequency source (9). For a fuel injector, the tip is covered by a bell connected to the electrical source. A plasma torch may be used during and after laser drilling to improve the bore quality. <IMAGE>

Description

SPECIFICATION Method of microdrilling metal workpieces using a power laser The present invention relates to a method of microdrilling metal workpieces using a power laser beam.
By the term microdrilling is meant the forming of holes with a diameter of less than a millimetre. An example of the type of hole which can be formed by the method of the present invention, is the fuel discharge holes of a fuel injector for an internal combustion engine, such holes having a diameter of between 0.1 and 0.5 mm.
The microdrilling of a metal workpiece using a power laser involves focusing a laser beam on the workpiece at the point where a hole is to be formed and then energising the laser to produce pulses of laser radiation. The laser radiation energy causes melting and vaporization of the metal so that both a vapour phase and a liquid phase are produced. The desired hole is therefore produced by the removal of material in the two aforementioned phases.
While the hole being formed is blind, the removal of the liquid phase is achieved by feeding into the hole a shielding gas, for example, helium, normally used in laser processes to reduce the phenomenon of 'blanketing' of the laser radiation by a zone of plasma formed between the workpiece and the source of laser radiation as a result of the vaporization of the material.
When the power density of the laser beam is very high, the liquid phase can be removed by utilising the phenomenon of 'laser supported detonation' (L.S.D.) which for each pulse of laser radiation gives rise to a pressure wave which moves out of the hole being formed at a high supersonic speed and is very efficient for removing from the hole fluid material and any solid products such as oxides and nitrides; at the same time, this pressure wave serves to form anew and smooth the sides of the hole.
However, with the known methods of drilling using a power laser it has not been possible to form holes with a surface finish and dimensional accuracy which are acceptable in certain applications, such as the fuel discharge holes of fuel injectors of internal combustion engines, where a high grade finish is required to avoid cavitation phenomena occurring during use.
The unsatisfactory finish to holes formed by known laser microdrilling techniques, is due to the fact that the transformation of the material of the workpiece from the solid phase to a liquid phase and to a vapour phase is very rapid so that there is virtually no time for heat to be transmitted into the body of the workpiece. In practice, only a very small thickness of the workpiece material surrounding the hole being formed is thermally affected by the laser microdrilling process, this thickness being of the order of thousandths of a millimetre; as a result, after a pulse of laser radiation very rapid cooling occurs with the cavity constituted by the partly4ormed hole acting like a heat sink.
Due to the cooling effect, the liquid phase immediately solidifies upon contact with the wall of the hole and adheres to this wall with the formation of surface irregularities. At the same time, condensation of the vapour phase produces more liquid which, due to the rapid cooling, does not have time to spread out over the walls of the hole before solidifying.
For the purpose of improving the quality of finish of holes formed by laser microdrilling techniques, it has been proposed to rotate the workpiece or the laser beam about the axis of the beam ("trepanning"); however, even with this arrangement it is not possible to obtain holes having a satisfactory quality for certain particular applications, such as for fuel injector nozzles.
It is therefore an object of the present invention to provide a laser microdrilling method which enables the formation of holes with an improved surface finish and dimensional accuracy previously obtainable only by conventional, non-laser, techniques which are extremely costly.
Accordingly, the present invention provides a method of microdrilling metal workpieces using a power laser, which includes the operation of heating the workpiece to a temperature sufficient to cause both the liquid phase formed directly by the action of laser beam and the liquid phase caused by the condensation of the vapour phase on the wall of the hole being formed, to be maintained in a liquid state for a period of time long enough to permit the uniform spreading of these liquid phases over the wall of the hole.
Preferably, the heating of the workpiece is effected by an electromagnetic induction heating process, by an electrical resistance heating process or by the action of a plasma torch of a neutral gas.
Advantageously, the surface of the workpiece is further heated by a plasma torch the jet of which acts along the axis of the laser beam on the face of the workpiece opposite that on which the laser beam is acting.
A laser microdrilling method according to the invention will now be particularly described by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a perspective view of apparatus arranged to form a hole in a metal plate in accordance with said laser microdrilling method; Figure 2 is a perspective view of further apparatus arranged to form fuel-discharge holes in fuel injectors in accordance with the said laser microdrillng method; and Figure 3 is a part-sectional view to an enlarged scale on line Ill-Ill of Fig. 2.
The apparatus shown in Fig. 1 comprises a laser generator 2 arranged to focus a pulsed beam 3 of laser radiation onto a metal workpiece 1 (in the form of a plate) in order to form a hole 4.
A nozzle 5 serves to direct shielding gas, for example, helium to the microdrilling zone.
The nozzle 5 preferably forms part of an apparatus for the control of the shielding gas, this apparatus being described in Applicants Italian patent application No. 67465-A/79 filed on 5th March 1979.
Two clamps 6 and 7 made of an electrically conducting material are secured to opposite ends of the workpiece 1 and are connected via a conductor 8 to a voltage source 9 for the purpose of effecting electrical resistance heating of the workpiece 1.
This heating is so controlled as to heat the workpiece 1 up to a temperature sufficient to cause the liquid metal phases, formed directly or indirectly in the hole 4 under the action of the laser beams, to remain in a liquid state for a period of time long enough to permit their uniform spreading over the walls of the hole 4 like a film. This spreading of the liquid metal phase occurs due to the action of the pressure impulse generated by each laser radiation pulse and, if necessary, under the action of a flow of shielding gas fed into the zone to be microdrilled.
The resistance heating of the workpiece 1 prevents the wall of the hole 4 from functioning as a "heat sink", and thereby prevents the liquid metal phases from solidifying and adhering to the wall of the hole 4 in an irregular manner due to very rapid cooling following termination of a laser radiation pulse.
The workpiece 1 and the laser beam 3 can be rotated relative to each other about the axis of the beam 3 in order to further increase the uniformity of the surface of the wall of the hole 4. The effect of this rotation is to compensate for any irregularity existing in the laser beam and to facilitate spreading of the liquid phase over the wall of the hole 4 through the action of centrifugal forces.
A neutral-gas plasma torch 10 can be directed along the axis of the laser beam 3 towards the surface of the workpiece 1 which is opposite to that upon which the laser beam 3 is acting.
The torch 10, besides contributing to the heating of the workpiece 1, also fulfils several other functions as is described below.
At the end of the microdrilling operation, the jet of the torch 10 effects a further heating of the walls of the hole 4, performing a final operation of flame polishing or a further spreading of the liquid phase and providing for a further elimination of microcracks which may be generated in conditions of rapid cooling.
The jet of the plasma torch also serves to expel from the hole 4 any solid particles, such as, for example, metal oxides or nitrides generated in the highly reactive environment presented by the combined presence of the laser beam and superheated metal vapours. The plasma torch jet further serves to prevent contamination by ambient air due to imperfect shielding by the flowing shielding gases.
Although Fig. 1 illustrates the use of the plasma torch 10 jointly with the resistance heating equipment, it is possible to use the plasma torch 10 as the sole source of heating of the workpiece 1.
The apparatus shown in Figs. 2 and 3, includes a laser beam generator 22 arranged to form holes at locations 44 in the tip 11 a of a fuel injector 11 of the type used for the injection of fuel in internal combustion engines.
in order to effect heating of the injector tip 11 a a metal bell element 12 is placed over the tip 11 a. This bell element 12 is provided with apertures 1 2a for the passage of the laser beam 3, and externally mounts an electrical winding 13 which is connected, by means of a conductor 14, to a source 15 of alternating current, preferably of high frequency.
Upon energisation of the winding 13 with alternating current, induced currents are caused to flow in the injector tip 11 a due to its positioning within the magnetic pole piece constituted by the bell element 12. These induced currents cause heating of the tip 11 a sufficient to enable the required spreading of the liquid metal phases during the laser microdrilling process.
The bell element 12 is provided with a shank 16 which is secured to a support 17 which also mounts the injector 11. The support 17 is provided with a shaft 18 by means of which it can be rotated about the axis of the laser beam 3.
The described laser microdrilling methods make it possible to form holes having a surface finish and a dimensional accuracy better than those obtainable with conventional laser microdrilling technology. In addition, the described methods enable laser microdrilling to be effected with a wider range of laser-beam power levels and pulse forms, the choice of these parameters for any particular application being less critical. As a result, less powerful lasers with greater controllability can be used.

Claims (6)

1. A method of microdrilling a hole in a metal workpiece using a power laser beam the action of which causes solid workpiece metal to be transformed into both liquid and vapour phases, said method including the operation of heating the workpiece to a temperature sufficient to cause both the liquid phase formed directly by the action of the laser beam and the liquid phase caused by the condensation of the vapour phase on the wall of the hole being formed, to be maintained in the liquid state for a period of time long enough to permit the uniform spreading of these liquid phases over the wall of the hole.
2. A method according to Claim 1, in which the workpiece is heated by an electromagnetic induction heating process.
3. A method according to Claim 1, characterised in which the workpiece is heated by an electrical resistance heating process.
4. A method according to Claim 1, in which the workpiece is heated by means of plasma torch of a neutral gas.
5. A method according to Claims 2 or 3, in which a jet of plasma of a neutral gas is directed along the axis of the laser beam onto the face of the workpiece opposite that on which the laser beam acts whereby upon a through hole being formed in the workpiece by the action of the laser. beam, the plasma jet serves to effect further spreading of the liquid phases over the wall of the hole.
6. A method of microdrilling a hole in a metal workpiece, substantially as hereinbefore described with reference to Fig. 1 or Figs. 2 and 3 of the accompanying drawing.
GB8004739A 1979-03-05 1980-02-13 Method of microdrilling metal workpiece using a power laser Expired GB2045669B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT67466/79A IT1119678B (en) 1979-03-05 1979-03-05 METHOD FOR MICRO-PERFORATING METAL PIECES USING A POWER LASER

Publications (2)

Publication Number Publication Date
GB2045669A true GB2045669A (en) 1980-11-05
GB2045669B GB2045669B (en) 1984-06-27

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ID=11302627

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8004739A Expired GB2045669B (en) 1979-03-05 1980-02-13 Method of microdrilling metal workpiece using a power laser

Country Status (4)

Country Link
DE (1) DE3007169C2 (en)
FR (1) FR2450663A1 (en)
GB (1) GB2045669B (en)
IT (1) IT1119678B (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4390774A (en) 1980-03-25 1983-06-28 National Research Development Corporation Method and apparatus for treating electrically non-conductive workpieces
US4857699A (en) * 1987-01-30 1989-08-15 Duley Walter W Means of enhancing laser processing efficiency of metals
US4877939A (en) * 1987-01-30 1989-10-31 Duley Walter W Means of enhancing laser processing efficiency of metals
US4879449A (en) * 1987-01-30 1989-11-07 Duley Walter W Means of enhancing laser processing efficiency of metals
US4891491A (en) * 1987-01-30 1990-01-02 Duley Walter W Means of enhancing laser processing efficiency of metals
US4933205A (en) * 1987-10-09 1990-06-12 Duley Walter W Laser etching of foam substrate
US4972061A (en) * 1987-12-17 1990-11-20 Duley Walter W Laser surface treatment

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4689467A (en) * 1982-12-17 1987-08-25 Inoue-Japax Research Incorporated Laser machining apparatus
EP0299143A1 (en) * 1987-06-12 1989-01-18 Raycon Textron Inc. Laser/EDM drilling manufacturing cell
DE102007051408A1 (en) 2007-10-25 2009-05-28 Prelatec Gmbh Method for drilling holes of defined geometries by means of laser radiation
CN112975147B (en) * 2021-02-07 2021-09-14 深圳市海特联科科技有限公司 Process for cutting piezoelectric silicon dioxide by laser

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3383491A (en) * 1964-05-05 1968-05-14 Hrand M. Muncheryan Laser welding machine
US3527198A (en) * 1966-03-26 1970-09-08 Tokyo Shibaura Electric Co Method and apparatus for working diamonds by means of laser light beam
CH1335667A4 (en) * 1967-09-25 1969-01-31 Laser Tech Sa Method for drilling watch stones using laser radiation
US4167662A (en) * 1978-03-27 1979-09-11 National Research Development Corporation Methods and apparatus for cutting and welding

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4390774A (en) 1980-03-25 1983-06-28 National Research Development Corporation Method and apparatus for treating electrically non-conductive workpieces
US4857699A (en) * 1987-01-30 1989-08-15 Duley Walter W Means of enhancing laser processing efficiency of metals
US4877939A (en) * 1987-01-30 1989-10-31 Duley Walter W Means of enhancing laser processing efficiency of metals
US4879449A (en) * 1987-01-30 1989-11-07 Duley Walter W Means of enhancing laser processing efficiency of metals
US4891491A (en) * 1987-01-30 1990-01-02 Duley Walter W Means of enhancing laser processing efficiency of metals
US4933205A (en) * 1987-10-09 1990-06-12 Duley Walter W Laser etching of foam substrate
US4972061A (en) * 1987-12-17 1990-11-20 Duley Walter W Laser surface treatment

Also Published As

Publication number Publication date
IT7967466A0 (en) 1979-03-05
DE3007169A1 (en) 1980-09-11
FR2450663A1 (en) 1980-10-03
GB2045669B (en) 1984-06-27
IT1119678B (en) 1986-03-10
DE3007169C2 (en) 1982-04-01
FR2450663B1 (en) 1984-02-03

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 19940213