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(11) | EP 2 394 786 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Finishing tool for turbomachine components |
| (57) A finishing tool form assembly (58) includes a base (70) and a superabrasive (66)
bonded to a surface of the base (70). The superabrasive (66) is configured to be reciprocated
with the base (70) relative to a longitudinally extending recess (50) of a component
(46) to finish at least one surface (54) of the component (46).
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BACKGROUND
[0001] This disclosure relates generally to a finishing tool. More particularly, but not exclusively, this disclosure relates to a finishing tool having a superabrasive that is used to finish a turbomachine component.
[0002] Turbomachines, such as gas turbine engines, are known. A typical turbomachine includes multiple sections, such as a fan section, a compression section, a combustor section, and a turbine section. During stable operation, the fan section moves air into the turbomachine. Some of the air is compressed. The compressed air is then mixed with fuel and combusted in the combustor section. Products of the combustion are expanded in the turbine section to rotatably drive the turbomachine.
[0003] Many turbomachines include blades mounted within rotor slots. The blades rotate with the rotors in the compression section and the turbine section, for example. Nonconformances and variations in the surfaces of the rotor slots can affect performance of the turbomachine. For example, a surface of a rotor slot that varies from a desired dimension can introduce stress concentrations in the rotor or in a blade mounted within that slot. Nonconformances and variations within the surface of the rotors defining the blade slots are often difficult to identify and eliminate. Nonconformances include geometric and metallurgical.
SUMMARY
[0004] An example finishing tool form assembly includes a base and a superabrasive bonded to a surface of the base. The superabrasive is configured to be reciprocated with the base relative to a longitudinally extending recess of a component to finish at least one surface of the component.
[0005] An example turbomachine component finishing tool assembly includes a fixture and a form mountable to the fixture. The form includes an abrasive bonded to a base. The fixture is configured to reciprocate the form relative to a surface of a turbomachine component.
[0006] An example turbomachine surface finishing method includes reciprocating a base relative to a surface of a turbomachine component. The method finishes the surface with an abrasive bonded to the reciprocating base.
[0007] These and other features of the disclosed examples can be best understood from the following specification and drawings, the following of which is a brief description:
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
Figure 1 shows a cross-section of an example gas turbine engine.
Figure 2 shows an example turbomachine component finishing tool assembly and a rotor of the Figure 1 turbomachine.
Figure 3 shows a close-up view of a portion of a rotor slot of the Figure 2 rotor.
Figure 4 shows a perspective view of an example finishing tool form used in the Figure 2 assembly.
Figure 5 shows another example turbomachine component finishing tool assembly and rotor.
DETAILED DESCRIPTION
[0009] Figure 1 schematically illustrates an example aircraft gas turbine engine 10, which is an example type of turbomachine. The example gas turbine engine 10 includes (in serial flow communication) a fan section 14, a low pressure compressor 18, a high pressure compressor 22, a combustor 26, a high pressure turbine 30, and a low pressure turbine 34. The gas turbine engine 10 is circumferentially disposed about an engine centerline X.
[0010] During operation, air is pulled into the gas turbine engine 10 by the fan section 14. Some of the air moves through a flow path 36 to a core of the gas turbine engine 10. The air moving through the flow path 36 is pressurized by the compressors 18 and 22, mixed with fuel, and burned within the combustor 26. The turbines 30 and 34 extract energy from the hot combustion gases flowing from the combustor 26.
[0011] In a two spool design, the high pressure turbine 30 utilizes the extracted energy from the hot combustion gases to power the high pressure compressor 22 through a high speed shaft 38, and the low pressure turbine 34 utilizes the extracted energy from the hot combustion gases to power the low pressure compressor and the fan section 14 through a low speed shaft 42.
[0012] The examples described in this disclosure are not limited to the two spool engine architecture described, however, and may be used in other architectures, such as single spool axial design, a three spool axial design, and still other architectures. Further, although the examples described herein are described with regard to the gas turbine engine 10, those having skill in this art and the benefit of this disclosure will understand that other examples include other types of turbomachines.
[0013] Referring to Figures 2-4 with continuing reference to Figure 1, a rotor 46 within the low pressure compressor 18 of the engine 10 includes a plurality of slots 50. As can be appreciated, the slots 50 are configured to receive the root section of the blades (not shown). The blades rotate with the rotor 46 within the low pressure compressor 18 of the engine 10. The blades pressurize air moving through the flow path 36 in a known manner.
[0014] During a forming operation, the rotor 46 is milled to establish the slots 50. The slots 50 are finished, in this example, to remove nonconformances from a surface 54 after the milling. The surface 54 of the rotor 46 defines portions of the slots 50.
[0015] A form 58 is received within one of the slots 50a during finishing. After inserting the form 58 in the slot 50a, a fixture 62 reciprocates the form 58 along an axis X1. The slot 50a extends along an axis X2 that is parallel to the axis X1. After finishing the slot 50a, the rotor 46 is rotated relative to the fixture 62, and the form is received within another of the slots 50.
[0016] In this example, portions of the form 58 corresponding to the surface 54 includes an abrasive 66 bonded to a base 70. As the form 58 reciprocates relative to the slot 50a, the abrasive 66 finishes the surface 54 of the slot 50a.
[0017] The fixture 62 reciprocates the form 58 for a controlled stroke and for an established length of time. Increasing the length of time increases the amount of material removed from the rotor 46, for example.
[0018] Finishing, in this example, removes or reduces nonconformances in the surfaces 54 of the slot 50 by removing about .001 inches (0.0254 mm) of material from the surface 54 of the rotor 46. In other examples, finishing removes nonconformances in other areas of the slot 50a, such as a surface 56, a surface 57, or removes a different amount of material
[0019] Example nonconformances include geometric nonconformances or variations in the position of the surface 54 of the slot 50a from a desired position of the surface 54. Other example nonconformances are the result of the interfaces between portions of the slot 50a machined by different milling cutters.
[0020] The example slots 50 have an enlarged portion 74 and a narrower neck portion 78. During operation of the engine 10, the root portions of the blades having a similar shape are received within the slots 50. As can be appreciated, the shape of the slots 50 limits movement of the blades radially away from the rotor 46.
[0021] In this example, the form 58 has a cross-sectional profile similar to the cross-sectional profile of the base of the blade. That is, the form 58 includes an enlarged portion 82 and a narrowed portion 86.
[0022] In this example, the base 70 of the form 58 is a cast iron material, and the abrasive 66, which is mounted to the enlarged portion 74 of the finishing form, is a superabrasive. More specifically, the example abrasive 66 is a cubic boron nitride abrasive that is 400 grit ASTM. Superabrasives, as is known in this art, are typically harder than conventional abrasives. As an example, conventional abrasives include pumice, sand, and silicon carbides. Superabrasives, by contrast, include diamond and the aforementioned cubic boron nitride.
[0023] A plating process, such as a nickel plating process, is used to bond a layer of the example abrasive 66 to the base 70. The base 70 is about 0.0015 inches (0.0381 mm). undersized relative to the slots 50. The abrasive 66 has a thickness of about 0.0015 inches (0.381 mm) when bonded to the base 70. Adding the abrasive 66 makes the thickness of the enlarged portion 82 of the form 58 to be about the same as the enlarged portion 74 of the slots 50.
[0024] In this example, a spring 90 housed within the fixture is used to bias the form 58 toward a radial center of the rotor 46. This facilitates the form 58 maintaining contact with the surface 54. Material removal rates can be controlled via variations in spring compression and spring stiffness.
[0025] Referring to Figure 5, in another example, a spring 90a is biased toward a roller 44, which biases a form 58a toward a radial center of a rotor.
[0026] Features of the disclosed examples include a low cost, high precision process that can rework slots and other turbomachine components rather than rebroaching an entire rotor slot, for example. Another feature of the disclosed examples is reducing the scrap rate of turbomachine components due to nonconformances in their surfaces.
1. A turbomachine component finishing tool assembly comprising:
a fixture (62); and
a form (58) mountable to the fixture (62), the form (58) including an abrasive (66) bonded to a base (70), wherein the fixture is configured to reciprocate the form (58) relative to a surface of a turbomachine component.
2. The turbomachine component finishing tool assembly of claim 1, comprising means to
spring bias the form (58) toward the surface.
3. The turbomachine component finishing tool assembly of claim 1 or 2, wherein the form
(58) has an enlarged head.
4. The turbomachine component finishing tool assembly of claim 1, 2 or 3, wherein said
abrasive (66) is a superabrasive.
5. A finishing tool form (58) comprising:
a base (70); and
a superabrasive (66) bonded to a surface of the base (70), wherein the superabrasive (66) is configured to be reciprocated with the base (70) relative to a longitudinally extending recess (50) of a component (46) to finish at least one surface (54) of the component (46).
6. The finishing tool assembly or finishing tool form (58) of any preceding claim wherein
the base (70) comprises cast iron.
7. The finishing tool assembly or finishing tool form (58) of claim 4, 5 or 6 wherein
the superabrasive (66) is plated to the base, for example nickel-plated to the base
(70).
8. The finishing tool assembly or finishing tool form (58) of any of claims 4 to 7, wherein
the superabrasive (66) comprises cubic boron nitride.
9. The finishing tool assembly or finishing tool form (58) of any of claims 4 to 8, wherein
the superabrasive (66) bonded to a surface of the base is .0015 inches thick.
10. The finishing tool assembly or finishing tool form (58) of any of claims 4 to 9, wherein
the superabrasive (66) comprises an ASTM 400 grit.
11. A turbomachine surface finishing method comprising:
reciprocating a base (70) relative to a surface (54) of a turbomachine component (46), for example a gas turbine engine component; and
finishing the surface with an abrasive (66), for example a superabrasive, bonded to the reciprocating base (70).
12. The turbomachine surface finishing method of claim 11, wherein the base (70) is spring
biased toward a rotational axis of the component (46).
13. The turbomachine surface finishing method of claim 11 or 12, wherein the base (70)
moves back and forth along a single axis during the reciprocating.
14. The turbomachine surface finishing method of any of claims 10 to 13, wherein the surface
of the turbomachine component is a surface (54) of a blade slot (50) within a gas
turbine engine component, such as a rotor (46).
15. The turbomachine surface finishing method of claim 14, wherein cross-sectional dimensions
of the base (70) with the abrasive (66) are the same as desired cross-sectional dimensions
of the blade receiving slot (50).