GB2437496A

GB2437496A - A laser shaping arrangement

Info

Publication number: GB2437496A
Application number: GB0608415A
Authority: GB
Inventors: Ben Anderson; Paul Williams
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2006-04-28
Filing date: 2006-04-28
Publication date: 2007-10-31
Also published as: GB0608415D0

Abstract

Shaping using laser beams (2) is known and has previously incorporated use of a mask with beam shaping aperture. Such apertures mean that parts of the beam (2) are shaded and therefore there is power loss with respect to shaping function. By use of an optical pathway which generates a projected shaping image the whole of the beam power is utilised for shaping.

Description

A LASER SHAPING ARRANGEMENT

The present invention relates to a laser shaping arrangement and more particularly to laser shaping arrangements utilised with respect to forming components for gas turbine engines.

It will be appreciated it is necessary to shape components in a number of situations. Some techniques such as casting and forging are appropriate to produce approximate shapes but generally in order to achieve necessary engineering precision, final forming and shaping is required. One technique with respect to shaping is to utilise a laser to cut and possibly smooth an article to a desired shape. The laser beam provides a high intensity, highly focused beam of light which is directed towards an object in order to remove and shape material.

Traditionally, this has been achieved with a simple laser beam projected towards the object in order to create desired shaping such as formation of a hole or excavation of mounting apertures or cavities.

More recently, as disclosed in US patent 5739502, it is has been known to provide a laser beam which is projected through a mask and simple optical pathway in order to project a beam having the shape of an aperture in the mask upon an object to be shaped. Such an approach will achieve the desired shaping of the object. However, it will be understood that a significant proportion of the laser beam is lost through shadowing as the beam passes through the aperture in the mask. Such loss of energy in the available beam will reduce the effectiveness of the process for shaping of an object. It will also be understood that the shadowing of the laser beam causes energy loss to the masking material about the aperture which therefore may cause problems with respect to degradation and a necessity for appropriate consideration of cooling. Nevertheless, the advantages of laser forming are still apparent with respect to particularly achieving layered formation where a hole is shaped in an object firstly of an outside shape and subsequent layers provided with additional holes or features as desired.

In accordance with aspects of the present invention there is provided a laser shaping arrangement comprising at least one optic pathway having a respective beam diffraction effect to form a projected shaping image, each projected shaping image additive to iteratively provide shaping by substantially whole beam projection.

Typically, the optical pathways are manipulated in order to generate a projected shaping image.

Typically, the arrangement incorporates a laser to provide a laser beam selectively coupleable to each of the optical pathways. Typically, the laser beam is pulsed.

Generally, the arrangement incorporates a housing to accommodate the optical pathway. Possibly, the housing comprises a wheel or carousel incorporating a number of optically active elements in order to provide each projected shaping image. Possibly, the carousel or wheel is rotatable to allow each optical pathway to be presented in use.

Possibly, the projected shaping image includes a square or polygon or circle or any other desirable shape.

Possibly, the projected shaping image incorporates a number of image elements.

Generally in accordance with the present invention, the laser shaping arrangement is directed to present a laser beam to an object such that the laser beam and/or optical pathways and/or object is maniputable in order to define each projected shaping image upon the object in order to provide shaping.

Typically, the optical pathways are provided by lenses and/or refractive elements and/or refractive elements and/or reflective elements and/or other optically active elements. Possibly, the lens or refractive element or other optically active elements incorporate indentations or other variations in shape or depth of material in order to create the projected shaping image when a laser beam is presented to that element or elements.

Possibly, the arrangement includes a MEM device comprising a grid of micro mirrors individually addressable to selectively reflect and deflect a laser beam to form a shaping image.

Also in accordance with the present invention there is provided a method of a laser shaping comprising presenting a laser beam to an object through a laser shaping arrangement as described above.

Possibly, the method involves presenting the laser beam through a number of optical pathways or repeatedly through the same optical pathway in order to create a desired shaping in an object.

Embodiments of the present invention will now be described by way of example and with reference to the accompanying drawings in which:-Fig 1 is a schematic illustration of a shaping arrangement in accordance with aspects of the present invention; Fig. 2 is a schematic illustration of a carousel or wheel incorporating optical elements in accordance with aspects of the present invention; Fig. 3 is a schematic cross section of an object shaped in accordance with aspects of the present invention; Fig. 4 is a schematic illustration of a first projected shaping image in accordance with aspects of the present invention; Fig. 5 is a schematic plan view of a second projected shaping image in accordance with aspects of the present invention; and, Fig. 6 is a schematic plan view of a third projected shaping image in accordance with aspects of the present invention.

As indicated above, prior approaches to providing laser beam shaping in objects have utilised a mask with an appropriately shaped aperture and simple optical focussing in order to present a laser beam to an object to achieve shaping. The use of a mask essentially shades parts of the laser beam and therefore reduces the available energy for shaping of an object.

Fig. 1 schematically illustrates a shaping arrangement in accordance with aspects of the present invention. Thus, an object 1 has a laser beam 2 incident upon it. This laser beam 2 is projected through a housing in the form of a wheel or a carousel normally incorporating a number of optically active elements in order to create a number of optical pathways for the laser beam 2 incident upon the object 1. The whole of the laser beam 2 is projected upon the object 1 without attenuation or shading as a result of utilising a mask with aperture. As an alternative to a carousel with a number of optically active elements, it will be understood that an arrangement can be provided with a single optical pathway of the desired projected image shape.

Fig. 2 illustrates a front view of the housing 3 in the form of a carousel which is mounted upon an axis 4 to enable rotation in the direction of arrowheads 5. Within the housing 3 a number of optical pathways are created utilising optically active elements 6. Thus, a laser beam 2 projecting through the optically active elements 6 will, as schematically illustrated, generate different shapes of different sizes and distributions. As schematically illustrated, one optically active element 6a may provide a square shape 7, whilst optically active element 6b may create a square of different size with rounded corners whilst optically active element 6c will create four circles in close association. It will be appreciated that these shapes 7, 8, 9 are schematic but in reality created by optical action in the element 6. Thus, the elements 6 will take the form of a lens or lens combination along with refractive elements and other optically active elements such as refractive and/or reflective elements as well as through shaping of the element 6 itself with recesses etc., in order to achieve the desired shape in the projected shaping image in operation. It will also be understood that by relative movement of the laser beam, optical element 6 and target object 1 shaping will also be achieved.

As no aperture mask is normally utilised the whole of the laser beam 2 is projected towards the object with limited, if any, attenuation due to shadowing as the laser beam 2 passes along the optical pathway varied by the element 6 towards the object 1. Normally, the laser beam 2 is pulsed to create shaping in the object 1. Thus, there is repeated application of laser beam pulses through the same optical pathway to shape the object.

The element 6 effectively provide optical pathways which are variously positioned and manipulated in such a way that the laser beam 2 passes through these optical pathways with enough pulses and energy to remove a desired amount of material from the object 1 in order to generate a planned shape.

Fig. 3 illustrates a possible schematic cross section of an object 11 having been shaped in accordance with aspects of the present invention. The object 11 has a cavity 12 formed through appropriate layer-by-layer shaping created by a laser beam incident upon the object 11. These layers are schematically illustrated as a, b, c and correspond to the shapes 7, 8, 9 created by the optical elements 6a, 6b, 6c as pathways for a laser beam incident upon an object. Thus, in layer a it will be noted that a generally square layer of the object 11 has been removed, in layer b a reduced size rounded cornered substantially square section of the object 11 has been removed, and in layer c holes have been created consistent with the pattern of shape 9 depicted in Fig. 2. In terms of the method of forming the cavity 12 as indicated this will be achieved through additive and iterative presentation of laser beams at the layers a, b, c successively through respective optical pathways. Initially, the laser beam is concentrated by the optical pathway (element 6a) in order to generate a square shape with the first few pulses of the laser beam then a smaller square shape with rounded corners may be created by further laser beam pulses presented through a second optical pathway (element 6b) and finally further laser pulses presented through an appropriate optical pathway (element 6c) in order to create the holes as described above. Thus, by the above method, a layer by layer shaping is utilised in order to generate holes with appropriate sizing.

Typically, the shapes generated as indicated will be through optical activity in the optical pathways provided.

However, it will also be understood that by appropriate relative manipulation between the object and the beam and the housing for the optical pathways, it will be understood that further flexibility with respect to shape generation can be achieved.

As a layer by layer approach is taken with respect to shaping it will be understood that the projected shaping images from the optical pathways created by the laser beams will be iteratively placed one upon the other sequentially in order to shape in terms of hole depth profile an object.

As the whole or substantially all of the laser beam energy is utilised without shadow losses it will be understood that the effectiveness of such shaping will be improved.

As indicated above, aspects of the present invention are normally based upon use of a succession of optical pathways to produce a succession of projected shaping images to act iteratively and in series in order to shape an object. In such circumstances the most convenient approach is to provide a housing as illustrated above in the form of a carousel with a number of elements 6 located in that carousel such that through simple rotation in the direction of arrowheads 5 the laser beam 2 can be appropriately presented to the optical pathways to generate the desired different projected shaping images. Typically, the desired succession of optical pathways will be arranged through elements 6 in the housing carousel such that there is a simple rotation step change between the optical pathways in order to create the different projected shaping images through the laser beam 2. However, it will be understood alternatively each of the elements 6 may be individually addressable and the laser switched off between displacements of the housing 3 to bring the desired optical element 6 into alignment with the beam to generate the desired projected shaping image as required. In such circumstances it will not be necessary to assemble the elements 6 in the correct stepped sequence order for each individual shaping operation upon an object prior to commencing the shaping method but rather provision of an appropriate control to enable accurate addressing to the desired optical element 6 position to create the desired optical pathway to form the projected shaping image on the object 1.

The element 6 may comprise a single optically active element appropriately configured to achieve image shaping in a beam passing through it. Alternatively, the element 6 may be representative of a series or cascade of optically active elements as required. The optically active elements may include shaped mirrors, optical fibres and a galvanometer head and deflection of the mirror to change beam shape. It will also be understood that an aperture mask may also be used in addition to the optical pathway effects in accordance with the present invention such that the aperture in the mask provides a final shaping form omitting any energy losses through shading. In such circumstances the optical pathway in accordance with aspects of the present invention will achieve an approximation to the desired projected shaping image which ideally will exactly match the aperture in the mask but practically will generally be slightly distorted such that the aperture in the mask finally "clips" an already approximately shaped image to the accurately desired image format for shaping. Clearly, the clipping of the optical pathway formed image will involve some shading but will be of a relatively minor nature.

Figs. 4 to 6 illustrate the collective and iterative effects of sequential presentation of projected shaping images in accordance with aspects of the present invention.

Thus, in Fig. 4 a plan view of an optical element 16 is provided which schematically provides a rounded corner square projected shaping image 17. In use the projected shaping image 17 will be incident upon an object and through laser beam shaping consistent with that image 17 shaping of the object is achieved. Once a sufficient layer depth has been achieved by the laser presented in the image 17, the laser beam will be switched off, that is to say pulsing stopped. In such circumstances a second optical element 26 will be presented which has, as schematically illustrated by projected shaping image 27, an octagon or truncated cornered shape.

Fig. 6 illustrates the images 17, 27 superimposed one upon the other by successive iterative actions of a laser beam in accordance with aspects of the present invention.

In such circumstances it will be noted that a top layer has the rounded cornered square aperture profile of image 17, whilst internal within that aperture layer the second image 27 has created a truncated cornered aperture layer consistent with image 27. Thus, the shaping layers are in series and iteratively combined in order to create the shaping profile of an aperture into an object in accordance with aspects of the present invention.

It will be understood that generally shaping processes and arrangements in accordance with the present invention are limited by a keyhole effect with the outermost layer broader than the inner most layers in a tapering open cascade. However, it may be possible to put the laser beam through a keyhole entry and then machine out behind the defocused beam to generate expansive shapes for internal layers of the shaping processes in accordance with aspects of the present invention. Nevertheless, as illustrated in Fig. 3 with regard to the aperture 12, and with regard to the superimposed series images 17, 27 and therefore aperture layers in Fig. 6, generally the present shaping apparatus and method allows creation of features with tapering open apertures into an object but other shapes are possible.

It will also be understood that Figs. 4 to 6 illustrate the ability to combine use of diffractive optics in order to create optical pathways in accordance with aspects of the present invention with a mask aperture.

Thus, for example, the optical element 16 may be designed to create a schematically depicted projected shaping image 17 whilst the optical element 26 may instead comprise a mask having an aperture 27 of a desired shaping beam shape.

In such circumstances, most of the laser beam is formed into the image 17 and therefore there is limited attenuation in beam power whilst final shaping, that is to say towards the chamfered cornered shape depicted in Fig. 5 with regard to image 27 can be provided through an aperture so that only beam power at the truncated corners will be lost.

Alterations and modifications will be appreciated by those skilled in the art. Thus, the laser beam in accordance with aspects of the present invention may be manipulated by mirror electronic memory (MEM) devices in the form of a grid of micro mirrors each addressable such that by selective reflection and deflection incoming laser light can be utilised to form a shaping image. In such circumstances the rays of the lower bean incident upon such a grid of micro mirrors will be able to create an image projected upon an object for shaping that can be dynamically altered as the shaping process progresses. In such circumstances with rapid laser pulsing the dynamic images created by the selective use of each of the micro mirrors builds a thin cascade of combined layers to achieve the desired shaping. This active laser beam shaping method will therefore create smoother shaping in comparison with the thicker stepped layers typical in the embodiments of the invention described above.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

Claims 1. A laser shaping arrangement comprising at least one optic

pathway having a respective beam diffraction effect to form a projected shaping image (7, 8, 9) each projected shaping image additive to iteratively provide shaping by substantially whole beam projection.

2. An arrangement as claimed in claim 1 wherein the optical pathways are manipulated in order to generate a projected shaping image (7, 8, 9) 3. An arrangement as claimed in claim 1 or claim 2 wherein the arrangement incorporates a laser to provide a laser beam (2) selectively coupleable to each of the optical pathways.

4. An arrangement as claimed in claim 3 wherein the laser beam (2) is pulsed.

5. An arrangement as claimed in any preceding claim wherein the arrangement incorporates a housing (3) to accommodate the optical pathway.

6. An arrangement as claimed in claim 5 wherein the housing (3) comprises a wheel or carousel incorporating a number of optically active elements (6) in order to provide each projected shaping image (7, 8, 9).

7. An arrangement as claimed in claim 6 wherein the carousel or wheel is rotatable to allow each optical pathway to be presented in use.

8. An arrangement as claimed in any preceding claim wherein the projected shaping image (7, 8, 9) includes a square or polygon or circle or any other desirable shape.

9. An arrangement as claimed in any preceding claim wherein the projected shaping image incorporates a number of image elements.

10. An arrangement as claimed in any preceding claim wherein the laser shaping arrangement is directed to present a laser beam (2) to an object (1) such that the laser beam (2) and/or optical pathways and/or object (1) is maniputable in order to define each projected shaping image (7, 8, 9) upon the object (1) in order to provide shaping.

11. An arrangement as claimed in claim 10 wherein each optical pathway is provided by lenses (6) and/or refractive element7/ and/or refractive elements and/or reflective elements and/or other optically active elements.

12. An arrangement as claimed in claim 11 wherein the lenses (6) or refractive element or refractive elements or reflective elements or other optically active elements incorporate indentations or other variations in shape or depth of material in order to create the projected shaping image when a laser beam is presented to that element or elements.

13. An arrangement as claimed in claim 11 or claim 12 wherein the arrangement incorporates a mirror electronic memory device comprising a grid of micro mirrors each electronically addressable to provide the shaping image through selective reflection and deflection of a laser beam to appropriately shape an object.

14. A laser shaping arrangement substantially hereinbefore described with reference to the accompanying drawings.

15. A method of laser shaping comprising presenting a laser beam to an object through a laser shaping arrangement as claimed in any preceding claim.

16. A method of laser shaping substantially as hereinbefore described with reference to the accompanying drawings.

18. A method as claimed of claim 15 or claim 16 wherein the method uses a number of optical pathways or acts repeatedly through the same optical pathway in order to create a desired shaping in an object.

19. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.