BACKGROUND OF THE INVENTION Field of the Invention

[001] The present invention relates to a fiber laser-based cutting apparatus and method for processing materials with a composite structure. More particularly, the present invention provides a laser-based cutting apparatus and system for combining two or more laser beams operating at different wavelengths to simultaneously process a protective film and an underlying workpiece.

Description of the Related Art

[002] Many industrial applications of lasers including, among others, fiber lasers involve the use of a single wavelength laser to cut metallic materials. These include applications such as cutting metallic compositions including aluminum, brass, copper, titanium, steel, stainless steel and related alloys such as nickel-titanium. Such cutting operations are result in a clean cutting surface based upon a number of factors, mcluding particularly the selection of a wavelength suitable for the specific metallic workpiece desired.

[003] Many metallic workpieces are pre-formed into a manufacturing shape having a final-finish surface which is protected by a thin polymeric film during later processing including during laser cutting. The polymeric film is intended for removal from the final- finish, surface following down- stream assembly or final product installation. Such thin polymeric films are provided by a number of polymers known to those in the polymer arts, and may include thin films of poly(methyl methacrylate)(PMMA), as a non-limited example. Other well known thin polymeric films may be used.

[004] Current laser-based cutting systems utilize C02 lasers at 10.6 micron for cutting composite materials which include metals and plastic films (polymeric materials). The absorption of the C02 output in metals desired to be more effective. Besides the C02 output cannot be delivered by conventional fibers, which thus make certain cutting processes practically impossible.

[005] Accordingly, there is a need for an improved method and laser-based cutting apparatus for processing metals provided with a protective film.

SUMMARY OF THE INVENTION

[006] In response, it is now recognized that, that two fiber laser systems may be used simultaneously, each operating at a different wavelength. It is further recognized a laser beam having a first wavelength suitable for metallic cutting and a second laser beam having a second wavelength suitable for protective film cutting may be separately selected and combined into a single processing beam for cutting a work piece.

[007] It is further proposed that a first wavelength in a about 2um (microns) range generated by a Thulium ("Tm") fiber laser and a second wavelength of between about 1.05μπι to 1.07um, output by an Ytterbium ("Yb") fiber laser may be combined using a suitable cutting laser head in a manner to cut multiple layers of metal and protective films made from polymeric materials resulting in a first-pass clean cut surface for down-stream processing. It is further recognized that such combined wavelengths when combined are processed through a single fiber of a fiber laser cutting machine.

[008] Accordingly to the proposed invention, an operative cutting machine combines a first laser beam having a first wavelength suitable for metallic cuttmg and a second laser beam having a second wavelength suitable for protective film cutting in a single laser fiber. Tm and Yr fiber-based lasers emit respective first and second laser beams along fibers combined together before or in a laser head into a single processing beam. A method selects suitable wavelengths and fiber lasers for selected metal and film layers and operates the cutting apparatus for cutting a work piece. Combining two different wavelengths from two different fiber lasers creates a clean cutting surface finish and improved quality.

[009] An aspect of the present invention provides a cutting machine associated with a combination of Tm and Yr fiber lasers which operate at respective different wavelengths to simultaneously cut respective protective film and workpiece covered by the film.

[0010] It is another alternative aspect of the present invention to provide a method for cutting one or more workpieces covered by a protective fil by the disclosed apparatus.

[0011] It is another alternative aspect of the present invention to provide an operable motion system to enable exposure of large surfaces using a cutting machine combining different wavelengths in a single processing beam.

[0012] The above and other aspects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a schematic representation of the proposed apparatus for processing a sheet provided with a protective film according to the present invention.

[0014] FIG. 2 is a process flow diagram for conducting a method for processing a sheet provided with a protective film according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Reference will now be made in detail to embodiments of the invention. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps. The drawings are in simplified form and are not to precise scale. For purposes of convenience and clarity only, directional (up/down, etc.) or motional (forward/back, etc.) terms may be used with respect to the drawings. These and similar directional terms should not be construed to limit the scope of the invention in any manner.

[0016] Referring now to Fig. 1, a fiber laser-based cutting system or apparatus 1 is provided with fiber laser light sources 2, 3 each generating respective outputs at different wavelengths. Of course, the fiber laser light sources are not limited to just two apparatus, but may include a plurality of thereof as indicated by 3N1, 3N2 and so on. Other laser configurations differing from fiber-based lasers may be adaptively used without departing from the scope and spirit of the present invention.

[0017] For non-limiting example, fiber laser sources may include ytterbium (Yb) fiber lasers or any other fiber laser, including all those provided by IPG Photonics Corporation of Oxford MA (www.ipgphotonics.com). The Yb fiber light sources 2 are selected and capable of producing different wavelengths of laser light within a broad 975 - 1030 nm range and preferably from about 1.05 um to about 1.07 μηα (microns). The Yb fibers lasers are configured to output a single- or multimode output in a power range between several hundreds watts to several kW. A wavelength of about 1.07 um is suitable for steel cutting steel sheets 8, aluminum, brass, tin, copper, or alloys may require other wave lengths. Moreover, while Yb-doped fiber lasers are most widely used light sources in industrial processes, including cutting, other rare-earth ion doped fiber lasers may enjoy industrial applications.

[0018] Fiber laser light sources 3 adapted to cut plastic films 9 each are configured as a Thulium-doped (Tm) fiber laser operating in a 1.8 um - 2.1 μτα range and within a power range extending between about several tens to several hundreds watts. It has been found that a Tm-generated beam at about 2 μιη is particularly suitable for cleanly cutting plastic films 9 including, among others, poly(methyl methacrylate) (PMMA). Again, the scope of the disclosure is not limited by exclusively Tm based lasers. For example, "green" lasers at about 514 - 515 nm can be used for cutting plastic materials. [0019] The outputs of fiber laser sources, 2, 3, etc. are guided by respective output fibers to a laser head 6 configured to combine the beams, focus and align the resulting output at the cutting region. As known to one of ordinary skills in the laser-based cutting/welding machines, laser head 6 may contain collimating and focusing optical components, such as mirrors and lenses. The latter may be coated with various wavelength-filtering coatings. The outputs of respective fiber lasers are combined in a single output beam 7 A which is guided along a delivery fiber 7 for emission containing both wavelengths of light.

[0020] Alternatively, the delivery fibers may be simply coupled to one another before or in laser head 6. This can be realized by using for example fiber combiners and etc. Thus in this approach, the beams with different wavelengths will be transmitted in a single delivery fiber. Furthermore, a further alternative configuration may have the outputs from respective Yb and Tm fiber lasers trained at a cutting region along different light paths. In other words each fiber laser system may have its focusing optics.

[0021] An exemplary setup of system 1 can further include 2 an interoperative computer control unit (CPU) 10 coupled to laser head 6 and fiber laser systems 2, 3, etc. respectively. CPU 10 contains a processor and memory elements (not shown) to receive and contain operation parameters to control system 1 which is thus used for motion control and laser firings.

[0022] It is recognized that the atmosphere proximate the interaction of processing beam 7A and sheet 8 and protective film 9 may be suitable for cutting and can include nitrogen, helium, argon, carbon dioxide, a vacuum, partial pressures, or any other gas mixtures known to the fields of fiber laser cutting and film processing. Typically, though, high pressure N2 is used for a clean and fast cut. Using the combined wavelength emission ensures a clean cut of the film without, however, interference with cutting workpiece.

[0023] Referring now to Fig. 2, an exemplary method 100 for operating the above disclosed fiber laser-based cutting system according to the present invention includes a step 101 of determining the materials of respective components of a sheet or workpiece to be cut. Thereafter a step 102 is selecting a first wavelength based on cutting a sheet and a step 103 of selecting a second wave length based on cutting a protective film. As one of ordinary skills in the laser arts readily understands, the wavelengths are selected in accordance with highest possible absorption thereof by respective materials.

[0024] Next in a step 104 respective fiber lasers generate designated first and second wavelengths suitable for cutting the workpiece and pass, in a step 105, those beams to a beam combiner system or module. The beam combiner in a step 106 combines beams at respective wavelengths and processes these through a laser head and into a processing beam sufficient to cut, in a step 107, the designated protective film and work piece until reaching an end step 108.

[0025] While not shown, it is understood that following end step 108, method 100 may be repeated as shown by the return arrow to a step 101. If not needed, it will be further understood that the steps 101, 102, and 103 may be passed over if there is no change in the underlying workpiece. Finally, it will be understood that an operational control system, (xmtaining processing units interacts with the fiber laser components, combiner system, and other laser diodes, mirrors, collimators, and operative optic and control components in a manner effective to achieve the desired method without departing from the scope and spirit of the present invention.

[0026] It will also be understood, that as used herein the phrase work piece or sheet material understood as representing the item being cut by the laser and having thereon one or more thin films. It will be further understood that the work piece or sheet material is not restricted to metallic sheets but may also include non-metallic materials, including glasses, plastics, ceramic components or other related or combined materials. It will be further understood that the phrase 'thin film' is not to be restricted to polymeric films but will be interpreted broadly to include pigment layers, oxide coatings, organic polymer films, cellulose-containing or adhesive containing layers having differing densities and componefits, but all different from the underlying sheet material. [0027] Having described at least one of the preferred embodiments of the present invention with reference to the accompanying drawings, it will be apparent to those skills that the invention is not limited to those precise embodiments, and that various modifications and variations can be made in the presently disclosed method and system for preheating of semiconductor material for laser annealing and gas immersion laser doping without departing from the scope or spirit of the invention. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.