GB2454187A

GB2454187A - Machining Apparatus

Info

Publication number: GB2454187A
Application number: GB0721231A
Authority: GB
Inventors: Jeffrey Charles Bishop
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2007-10-30
Filing date: 2007-10-30
Publication date: 2009-05-06
Also published as: GB0721231D0

Abstract

Forming components such as blades (3) for gas turbine engines requires use of erosion and cutting techniques. In such circumstances the component (3) must be robustly presented in a clamping arrangement (8, 9; 25A,B, 28) but also cut or eroded appropriately to avoid stressing upon the component which may cause rejection and failure in use. By utilising a water-jet (23) which is fixed and static and manipulating a component in itself in an appropriate clamp arrangement (8, 9; 25A,B, 28) it is possible to achieve accurate forming and shaping of a component (3) using the water-jet whilst avoiding over-stressing of the finally formed component.

Description

MACHINING APPARATUS

The present invention relates to machining apparatus and methods of operating machining apparatus particularly with regard to forming components such as blades for gas turbines.

Manufacture of components for assembly into machines such as gas turbine engines requires precision with respect to dimensions as well as achievement of operational performance. In such circumstances such processes as forging and casting are utilised to generally shape components with subsequent machining processes utilised in order to achieve a final form. Unfortunately, these machining processes can introduce stresses and strains to the component preform which can themselves reduce operational life and increase the number of reject components.

It will be understood that generally components for utilisation in machines such as gas turbine engines are specified with regard to their operational performance within that machine or engine and typically not with respect to potential problems during processing and manufacture.

Particular components which can present problems are blades utilised in gas turbine engines. These components comprise a relatively delicate aerofoil with a root element utilised to locate the blade in an engine. As will be appreciated an initial component preform is produced which is generally near to the final form. The final form is achieved by material, typically metal, removal machining processes. During these removal machining processes generally the blade in accordance with known practice will require clamping through the aerofoil. Such clamping can result in severe stresses as a result of the machining processes utilised for the material removal in the root section of the blade component. Traditionally such machining processes included hard point machining and grinding for a close to size casting or forged component such as a blade. The blade itself is manufactured via a hot extrusion/forging process from a cylindrical glass-coated slug partially extruded to produce a thin axial blade that provides the basis for an aerofoil washed surface. Further forging of the component preform produces a rough root mass but this rough root mass must be further processed.

Typically in excess of 90% of blade machining operations concern forming of the blade root but fixing the component to allow such processes necessitates clamping upon as indicated delicate aerofoji sections. In such circumstances typical prior hard point machining and grinding processes are not advantageous.

More recently water-jet machine processes have been devised in which a water-jet typically augmented with abrasive elements such as grit is utilised to shape and form a component preform into a desired final shape. Such water-jet machining is generally less aggressive with regard to loading but nevertheless the component preform still requires positioning for accurate shaping and forming. Furthermore, manipulation of a traditional water-jet head to the appropriate six dimensions of orientation possibly necessary for accurate machining can be difficult.

In accordance with aspects of the present invention there is provided a machining apparatus for components, the apparatus comprising a water-jet directed towards a component preform to remove and/or define shape, the apparatus characterised in that the water-jet is fixed and static, the apparatus includes a manipulation mechanism for presenting the component preform in use to the water-jet and the manipulation mechanism provides orientation manipulation of the component preform relative to the water-jet to form the component in use.

Typically, the manipulation mechanism includes a clamp arrangement with a clamp feature. Generally, the clamp feature includes a handle. Possibly, the handle is displaced from a portion of the component preform upon which the water-jet is incident in use. Typically, the clamp feature includes a root to present the component preform with an elongate portion of the component preform extending in use from the root and upon which the water-jet is incident. Typically, the clamp feature is removable by the water-jet to provide the component.

Generally, the manipulation mechanism presents the component preform in a booth to contain dispersion of the water-jet. Typically, the manipulation arrangement presents the component preform away from a containment surface to provide for appropriate dissipation of the efflux energy of the water-jet prior to incidence upon the containment surface.

Typically, the manipulation arrangement can manipulate the component preform for displacement in at least three dimensions.

Typically, the water-jet is fixed in an axiostatic direction. Possibly, the water-jet can be varied in terms of its width and/or flow rate and/or composition.

Typically, the water-jet includes abrasive elements.

Typically, the abrasive elements include grit. Possibly, the proportion of abrasive elements in the water can be varied. Possibly, a mix of different types of abrasive elements in the water-jet can be varied.

Possibly, the apparatus includes a sump arranged to receive and absorb effusion energy of the water-jet.

Typically, the sump incorporates a depth of water to -absorb the water-jet.

Possibly, the apparatus includes means to recover and collect a detached portion of the component preform.

Generally, the apparatus includes a sensor to determine angular and/or axial position of the component preform to determine appropriate manipulation of the component preform via the manipulation mechanism relative to the water-jet.

Also in accordance to aspects of the present invention there is provided a method of machining a component from a component preform using a water-jet, the component preform presented in a clamp arrangement, the method characterised in that the clamp arrangement is associated with a manipulation mechanism and the water-jet is fixed and static whereby the component in the clamp arrangement is manipulated in the water-jet to shape and/or form the component.

Typically, the component is a blade having an aerofoil. Possibly, the clamp arrangement clamps the component away from the aerofoil.

An embodiment of aspects of the present invention will now be described by way of example and with reference to the accompanying drawings in which: -Figure 1 is a schematic depiction of the stages of component formation; and, Figure 2 is a schematic illustration of a machining apparatus in accordance with aspects of the present invention.

As indicated above components such as blades for utilisation in gas turbine engines can be produced by a number of processes. These processes may introduce their own problems with respect to stressing of a component which can lead to post production failure. Figure 1 provides a schematic illustration of one production process which initially is consistent with existing methods of production but with regard to latter forming and shaping processes uses a machining apparatus and method which is consistent with aspects to the present invention.

Initially, a raw material such as a glass-coated cylindrical slug 1 (Figure la) is heated and presented to extrusion dies (not shown) . Figure lb illustrates an extruded "H" section in the initial hot extrusion formation of a component in accordance with aspects of the present invention. As illustrated in Figure lc whilst preserving the initial "H" section a remaining slug portion is further forged to produce a rudimentary blade platform 3 and root mass 4. In such circumstances a basic component structure is defined by the forging processes and as outlined above.

In accordance with aspects of the present invention and as depicted in Figure ld an initial "H" section is further hot forged to redistribute material and create a finished aerofoil surface 5 which is bound at leaning and trailing edges by clamp features in the form of handles 6, 7. The handles 6, 7 are forged so as to be integral with the blade 5 and platform 3. Typically the volume of material displaced for the aerofoil shape and size and position enables provision of a standardised handle configuration. Furthermore, the volume of material displaced is accommodated via a free dispersal of excess flashing through and along outer edges of the handles 6, 7.

The handles 6, 7 are utilised to enable clamping using clamp members 8, 9 to appropriately robustly present the aerofoil 5, platform 3 and root 4 in a component preform.

In accordance with aspects to the present invention such a clamping arrangement allows either through mechanical or electrical processes use of an appropriate manipulation mechanism for manipulation of the component preform defined by the earlier extrusion and forging processes. In such circumstances a final finish surface can be define in and to the aerofoil 5 and platform 3/root 4 sections. Forming and shaping is performed utilising initially a water-jet machine in order to roughen out the shape prior to application of a chip machining or grinding process for a final finish to the root and platform surfaces.

After finishing machining of the root 4 and platform surface 3 as depicted in Figure if the component preform can be clamped through a clamp member 10 associated with the root as finally formed. With such robust clamping a final finishing can be applied to the aerofoil again through a water-jet process. Figure ig illustrates such a process with clamping provided by the clamp 10 and with an aerofoil 11 cut such that a waste portion 12 is removed. It will be noted that waste portion 12 incorporates the handles 6, 7 such that the aerofoil 11 is effectively an elongate section which extends away from the platform 3. It will be understood in accordance with aspects of the present invention that the clamp 10 allows orientation and presentation in a manipulation mechanism relative a fixed and static water-jet as described later. In such circumstances the leading and trailing edges as well as the tip of the blade aerofoil 11 can be cut and shaped to a desired form.As indicated the handles 6, 7 previously used for clamping of the component whilst the root portions are shaped can be removed.

The water-jet erosion process can create elliptical leading edges for the aerofoil 11 by suitable simultaneous axial rotational and transverse manipulation of the aerofoil 11 in a fixed and static water- jet stream with absolute control of machining loads and thus deflections of the delicate aerofoil 11 now formed. In such circumstances stresses and in particular the stresses at the root connection between the aerofoil 11 and the platform 3 can be reduced. Once the aerofoil 11 and platform 3 structures are substantially formed by the water-jet processing in accordance with aspects of the present invention typically the whole blade will then be dried and polished to give an appropriate aerofoil washed surfaced for operational performance.

The present invention relates to utilising a fixed water-jet in order to provide shaping of a component preform. In order to shape and form in such circumstances it will be understood that the component itself must be manipulated relative to the fixed water-jet. Such manipulation therefore requires robust and accurate clamping of the component preform during forming and shaping processes by the water-jet. Aspects to the present invention ensure that through the shaping procedures the component preform is adequately supported to avoid stressing of the component preform through water-jet impingement and the necessary forces exerted for manipulation in three dimensions.

Although it is possible to provide most functions by water-jet shaping and forming it will be understood that generally it is advantageous to combine both water-jet forming and hard point machining of components. In such circumstances it is again important that an appropriate clamping arrangement is provided to robustly present a component preform to avoid stressing as a result of manipulation as well as machining processes.

A typical machining apparatus in accordance with aspects of the present invention will incorporate a high pressure water-jet generator supplying a cutting liquid medium as an axiostatic downward vertically orientated jet stream. This jet-stream will be fixed and have a static position relative to a multi-axis manipulation system to effectively handle the component preform in the fixed water-jet. Normally machining of the component preform will be provided at a height above a floor or other impingement surface in order to ensure there is adequate dissipation of water-jet efflux energy prior to contact with the impingement surface or floor. In such circumstances jet bounce-back to the component is avoided. Typically, the machining apparatus will be located within a vessel or booth to contain the water-jet as well as machining dust, powder and nuggets from the shaping and forming processes.

Normally the portions 12 and other dust, powder and nuggets removed from the component preform will be collected within an appropriate receptacle for recycling.

Below the water-jet it is possible to provide a sump or well filled with water in order to absorb the water-jet and in particular the efflux energy of the water-jet to stop splash back.

As indicated above aspects to the present invention have particularly utilisation with regard to relatively delicate aerofoils as part of blades in accordance with aspects of the present invention. An objective as with all manufacturing processes is to improve component harvest in terms of the number of acceptable components as a result of the manufacturing process. By introducing clamping features which allow robust and repeatable presentation of the component preform within a machining apparatus it will be understood that the remaining problems then principally relate to control of the magnitude of external machining loads and energy dissipated through the component as a result of the machining processes. For delicate components such as compressor or turbine blades the load/energy characteristics can be crucial for successful blade production. Furthermore, by removing waste sections 12 and sizeable nuggets it will be understood that recycling of recovered material can be more easily achieved. Robust clamping allows more confidence with regard to removing larger waste sections in comparison with slower marginal and iterative removed of small amounts as dust.

By aspects to the present invention it is not necessary to remove all the material in order to provide the final component form through hard point abrasive processes leading to dust, powder and chips. By reducing the amount of abrasive machining necessary in terms of creation of dust, powder and chips it will also be understood that the machining energy dissipated through the component as well as local machining loads as a result that dust, powder or chip and in relation to the speed of shaping and forming can be controlled. It will be understood that previous continuous removal processes generally created hard point vibrational excitement in the component which can stress and distort that component beyond acceptable levels.

Water-jets provide a continuous removal process which is non-deteriorating and provides a time consistent procedure with self replenishing particle-inclusion water-jet composition. By fixing the water-jet axiostatically it will be understood that there is conservation and consistency with regard to the jet stream avoiding any problems with respect to rapid latent displacement and inertial effects with regard to a moving water-jet head.

Provision of sacrificial clamp fixtures in the form of handles 6, 7 allows manipulation of a component in multiple directions for a total machining process. It will be understood that by presenting a vertically downwardly directed static water-jet stream there is maximisation of gravitational confinement of the water-jet efflux which keeps processing areas tidy in terms of losses. With reduced stressing of the final component it will be understood that a high proportion of such components will meet stringent quality testing.

Aspects of the present invention combine appropriately robust presentation of a component preform with manipulation of that component relative to a fixed and static water-jet for shaping and forming processes. As indicated generally aspects of the present invention relate to relatively fragile structures which can be difficult to machine and process. For example aerofoils will be fragile and susceptible to damage if misused whilst attempting to shape the aerofoil portions of blade. It has been found that particular problems are found at a root radius where cracking can lead to failure both in service and as a result of quality controls in respect to blade manufacture.

Figure 2 provides a schematic illustration of a machining apparatus in accordance with aspects of the present invention. A vessel or booth 20 generally surrounds the apparatus 21 to enclose and inhibit dissipation of water spray as a result of the processes in accordance with aspects of the present invention. A water-jet source 22 directs a water-jet 23 towards a component 24. The component 24 is held in a clamp arrangement 25 formed by respective jaws 25a and 25b engaging clamp features in the form of handles 26 in the component 24. In such circumstances a component 24 can be manipulated in directions A to F or vectorially between them in order to present the water-jet 23 towards as illustrated a root portion 24a of the component 24. The root portion 24a can be shaped by moving the clamp arrangement 25 using the manipulation mechanism 27 in the directions A to F. This manipulation mechanism may comprise an arm gripping the clamp 25 to move the component 24 relative to the water-jet 23.

As described above once the root portion 24a is appropriately shaped there will be a further clamp 28 which can be associated with that root portion 24a to allow manipulation through that association again in the directions of arrowheads A to F for shaping and formed the aerofoil. In such circumstances as described above with regard to Figure if the clamping features can be cut away to reveal an aerofoil. This aerofoil can be further shaped by the water-let 23 appropriately.

Whilst the clamping features are cut away by the water-jet 23 it will be appreciated that the component may still be supported through the clamp features in the form of handles such that the component while the aerofoil is cut is supported both by the clamp 25 and the clamp 26 both manipulated appropriately by manipulation mechanisms to manoeuvre the component in the water-jet 23. Once the water-jet 23 has cut the aerofoil to leave it extending longitudinally away from a platform section 29 it will be understood that the clamp 25 can be used to collect and appropriately deposit the waste portion 12 (Figure ig) for recycling.

With the cut-out aerofoil it will now be understood that edges of that aerofoil can be further shaped and rounded by appropriate manipulation through the root 24a and clamp 28 of the component 24 to a desired final shape.

Typically, in order to achieve an appropriately smooth final surface further polishing processes may be provided.

In normal circumstances it will be understood that manipulation mechanisms are utilised with regard to the clamps 25, 28. These manipulation mechanisms may incorporate multi-active spindles which act as indicated to manipulate the component relative to the fixed and static water-jet 23.

As indicated above it is generally the aerofoil surfaces which are delicate and subject to possible stressing and damage. By provision of a clamping arrangement which incorporates clamp features extending along the prospective edges of the aerofoil in addition to showing robust presentation these clamp features provide stiffening elements to improve the structural integrity of the relatively thin aerofoil profile. Furthermore, it will be understood that clamping is to the clamping features comprising handles or rails along the edge of the component perform rather than to the delicate features. In such circumstances there is no direct clamping force applied to the aerofoil surface and therefore potential damage.

Essentially the aerofoil extends as a web between the clamping features such that there is a lower stress demand upon the aerofoil web or profile.

Water-jets in accordance with aspects of the present invention erode the component preform. The rate of erosion can be very slow and in the order of 1mm per hour so limiting energy input, and at least the severity of such input, to the component preform and so potential damage.

Generally the rate of erosion or cut is more important than the rate of cutting. In such circumstances when forming components such as blades for a gas turbine engine, slower rates of erosion in cutting and other forming processes will be used. With respect to water-jet cutting arrangements in which the water-jet is manipulated about the component it will be appreciated that there are inertia effects which change when turning about a corner in a structure cut or eroded by the water jet. These inertia effects are as a result of the fluid and any abraded materials within the fluid utilised in the water-jet. In such circumstances conventional water-jet cutting apparatus utilises 5-axis manipulation heads to obviate the problems of inertia engagement. Such 5-axis adjustment heads are relatively complex. By aspects of the present invention the water-jet is kept static and fixed whilst the component itself is manipulated. In such circumstances when forming an elliptical leading edge in the aerofoil it will be appreciated that the component about that edge will be turned relative to the edge to be shaped. Such an approach reduces problems with inertia in the water-jet to enable the leading edge to be eroded very gently.

By initially shaping the root portion 24a and then clamping that shaped root portion 24a to allow manipulation initially for cutting a base aerofoil and subsequent edge profiling it will be understood that there is less swarf created. In particular the waste portion 12 (Figure lg) can be removed as a relatively substantial element which facilitates easier recycling. The amount of dust, powder and other particles which may be more difficult to process and recycle is therefore reduced.

As the jet 23 is fixed and static it will be appreciated that the jet 23 will therefore be permanently aimed and so a smaller flow arrester for the jet can be used. It will be understood that these flow arresters are utilised to dissipate the jet energy but are generally contaminated with powder and debris from the erosion/cutting process of the component and therefore are dirty and full of grit. Having a small arrester well or sump in such circumstances will have advantages with respect to reducing the amount of waste water and cleanliness with respect machining apparatus.

Modifications and alterations to aspects of the present invention will be appreciated by those skilled in the art. Thus for example as indicated a clamp arrangement will be utilised for appropriate robust presentation of a component in accordance with aspects of the present invention and in particular delicate or easily damaged component profiles. This clamp arrangement itself may be secured to a robotic arm or otherwise in order to provide the desired manipulation in the fixed and static water-jet.

Generally the water-jet itself will be static but it will be appreciated that in terms of its width/diameter as well as the composition of the water-jet itself may be varied.

In such circumstances the water-jet generally incorporates abrasive elements such as grit. The dimension/grade of the grit as well as the type of grit or other abrasive material may be varied in the water- jet dependent on the incident part of the component at a particular time. In such circumstances initially a sensor or probe may be utilised in order to accurately determine the position of the component in the clamping arrangement. The water-jet again would remain static and fixed whilst through the accurate determination of the position of the component in the clamping arrangement specific movements of the component can be achieved relative to the fixed water-jet for cutting and abrasive purposes. The water-jet may then be varied in terms of its width, flow rate, composition and possibly even with respect to pulsing subject to any vibrational loading in order to achieve the best erosion and cutting for a particular aspect or part of the component. Thus the component can be more readily shaped and formed to the desired final profile required.

Whilst endeavoring 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

1. A machining apparatus (21) for components, the apparatus comprising a water-jet (23) directed towards a component perform (3, 4; 24) to remove and/or define shape, the apparatus characterised in that the water-jet is fixed and static, the apparatus includes a manipulation mechanism (27) for presenting the component preform in use to the water-jet and the manipulation mechanism provides orientation manipulation of the component preform relative to the water-jet to form the component in use.

2. An apparatus as claimed in claim 1 wherein the manipulation mechanism includes a clamp arrangement (8, 9; 25, 28) with a clamp feature (6, 7)

3. An apparatus as claimed in claim 2 wherein the clamp feature includes a handle (6, 7)

4. An apparatus as claimed in claim 3 wherein the handle is displaced from a portion (5, 11) of the component preform upon which the water-jet is incident in use.

5. An apparatus as claimed in any of claims 2 to 4 wherein the clamp feature includes a root (4) to present the component preform with an elongate portion of the component preform extending in use from the root and upon which the water-jet is incident.

6. An apparatus as claimed in any of claims 2 to 5 wherein the clamp feature is removeable by the water-jet to provide the component.

7. An apparatus as claimed in any preceding claim where the manipulation mechanism presents the component preform in a booth (20) to contain dispersion of the water-jet.

8. An apparatus as claimed in any preceding claim wherein the manipulation arrangement presents the component preform away from a containment surface to provide for appropriate dissipation of the efflux energy of the water-jet prior to incidence upon the containment surface.

9. An apparatus as claimed in any preceding claim wherein the manipulation arrangement can manipulate the component preform for displacement in at least three dimensions.

10. An apparatus as claimed in any preceding claim wherein the water-jet is fixed in an axiostatic direction.

11. An apparatus as claimed in any preceding claim wherein the water-jet can be varied in terms of its width and/or flow rate and/or composition.

12. An apparatus as claimed in any preceding claim wherein the water-jet includes abrasive elements.

13. An apparatus as claimed in claim 12 wherein the abrasive elements include grit.

14. An apparatus as claimed in claim 12 or claim 13 wherein the proportion of abrasive elements in the water can be varied.

15. An apparatus as claimed in any of claims 12 to 14 wherein a mix of different types of abrasive elements in the water-jet can be varied.

16. An apparatus as claimed in any preceding claim wherein the apparatus includes a flow arrester arranged to receive and absorb effusion energy of the water-jet.

17. An apparatus as claimed in claim 16 wherein the flow arrester incorporates a depth of water to absorb the water-jet.

18. An apparatus as claimed in any preceding claim wherein the apparatus includes means to recover and collect a detached portion (12) of the component preform.

19. An apparatus as claimed in any preceding claim wherein the apparatus includes a sensor to determine angular and/or axial position of the component preform to determine appropriate manipulation of the component preform by the manipulation mechanism.

20. A machining apparatus for a component substantially as hereinbefore described with reference to the accompanying drawings.

21. A method of machining a component (3, 4; 24) from a component preform using a water-jet (23), the component preform presented in a clamp arrangement (8, 9; 25, 28), the method characterised in that the clamp arrangement is associated with a manipulation mechanism (27) and the water-jet is fixed and static whereby the component in the clamp arrangement is manipulated in the water-jet to shape and/or form the component.

22. A method as claimed in claim 21 wherein the component is a blade having an aerofoil (5, 11)

23. A method as claimed in claim 22 wherein the clamp arrangement clamps the component away from the aerofoil.

24. A method of machining a component from a component preform using a water-jet substantially as hereinbefore described with reference to the accompanying drawings.

25. 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.