JP5301125B2 - Combined electromachining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a rotor blade via an electrolytic discharge for accelerating an efficient manufacture of a small batch with a reduced complexity. <P>SOLUTION: A pre-form 10 includes an airfoil stub 14 and a dovetail hub 16. The hub 16 is subjected to electrolytic discharge machining first to thereby form a rough dovetail 32. The airfoil stub 14 is subjected to electrolytic machining to thereby form an airfoil 18. Subsequently, the rough dovetail 32 is subjected to electrolytic machining to thereby form a rough tongue-like part 34. The rough tongue-like part 34 is subjected to finish-machining, to thereby form a dovetail 20 extending from the airfoil 18 in a single rotor blade 12. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates generally to machining, and more specifically to galvanic machining.

  Modern gas turbine engines include multiple rows of rotor blades mounted around a support rotor disk. The compressor blades are used to pressurize the air in the compressor, and the turbine blades are used to expand the combustion gases that power the support disk.

  The high pressure turbine powers the compressor through a drive shaft that extends between the compressor. In addition, low pressure turbines power upstream fans in turbofan aircraft engine applications. In marine and industrial applications, the low pressure turbine powers an external drive shaft that powers, for example, a marine propeller or generator.

  The gas turbine engine includes a multi-stage compressor and turbine blades. Thus, many such blades are found in gas turbine engines. The blades in each stage and row are identical to each other and usually vary in size from stage to stage.

  Various manufacturing processes are available for efficient production of compressors and turbine blades, but many such blades require considerable resource and time consumption, which can be attributed to production speed and final engine speed. Affects the cost.

  Compressor blades are typically solid superalloys that are initially manufactured from each preform. Preforms are typically made from rods by an upsetting process that plastically deforms the metal to form a relatively large dovetail hub and an integral, relatively thin airfoil stub. Since the preform contains excess material all around it, the final shape of the rotor blade can now be processed appropriately.

  However, these preforms are made of a superalloy, such as a nickel-base superalloy, and have increased strength when used in gas turbine engines, which makes it more difficult to machine metal during the manufacturing process. Become.

  The airfoil portion of the blade extends in a span direction from the root to the tip and has a generally concave pressure side and a generally convex suction side that extends across the chord between opposing leading and trailing edges. Need to be machined precisely.

  The blade dovetail is also precisely machined to provide a pair of opposing lobes or tongues having a typical dovetail shape for mounting individual blades in corresponding dovetail slots around the support rotor disk. Form. The dovetail is axially fitted into the rotor disk rim in an axial slot or is circumferentially fitted and supported in a circumferential dovetail slot extending around the rim of the rotor disk Can do.

  Thus, the airfoil and dovetail are configured differently from each other, but are accurately supported around the rotor disk in efficiently performing the compression function on the air that is induced through the compressor during operation. At the same time, it is necessary to have a precise configuration with respect to each other to withstand the considerable aerodynamic and centrifugal loads experienced during operation.

  In one conventional manufacturing process for compressor rotor blades that have been commercially used in the United States for many years, the compressor blades are formed in a continuous process. First, the above-described preform is secured around the airfoil stub, and then the dovetail hub is precision ground to a rough or nearly H or I dovetail with grooves on both sides forming a reference surface. The

  The preform is then secured around the coarse dovetail in a conventional electrochemical machining (ECM) machine, where a pair of electrode tools or plates are translated together on either side of the airfoil stub to electrochemically process the material. Form a precisely configured airfoil within the required small tolerance range expressed in units of a few mils.

  Electrochemical machining is a conventional technique where the preform and electrode plate are electrically driven as the anode and cathode, respectively, and the liquid electrolyte circulates in the gap between the anode and cathode. The ECM removes material from the airfoil stub so that the opposing plates translate inward relative to each other to reach the final thickness and shape of the airfoil corresponding to the complementary contours of the two electrode plates.

  Here the airfoil is machined to its final shape and surface finish, so it is usually well protected during the next manufacturing process by being encapsulated in a suitable soft metal matrix such as tin and bismuth. Need to be done.

  The encapsulated airfoil is then properly secured again to the precision grinding machine, and the coarse dovetail is precision ground to an intermediate rough tongue shape that closely encloses the required shape of the final dovetail. To be able to. Precision grinding places a considerable load on the preform and therefore this load needs to be properly supported by the corresponding fixture. Since the original airfoil stub is oversized, a relatively simple fixture or clamp can be used to support the stub.

  However, the machined airfoil has its final dimensions and surface finish, and simple fixation may cause unacceptable damage to the airfoil, thus protecting the airfoil by encapsulation. The encapsulation can then be easily secured to a grinding machine.

  Following grinding of the finished tongue, the final shape of the dovetail can then be obtained in any conventional machining process, such as by additional precision machining of these individual dovetail tongues or lobes.

  Once the dovetail is finally machined, the airfoils can be de-encapsulated by simply melting the soft metal matrix from them. Here, the preform includes a final finished airfoil and dovetail and an integral platform between them, and is then commonly used to trim the airfoil length to the required tip height, for example. Undergoing a finishing process.

  The separate steps normally required when machining a preform to the final configured rotor blade typically require multiple processing machines and multiple operators, further adding to the associated costs. To increase.

  Considering the large number of blades required at each stage of a turbine engine, compressor blades are typically processed in relatively large lots. For example, eight preforms can typically be subjected to precision grinding at the same time to form a rough dovetail. The 40 preforms can be subjected to precision grinding around the support fixture to form these rough tongues.

  The ECM process typically involves an electrode plate with a generally concave pressure side of each airfoil, usually from the root to the tip and between the leading and trailing edges, and a generally convex negative surface of each airfoil. Since it is fitted to complement the compression side, it takes place simultaneously on a single blade.

  Batch processing of preforms allows them to be machined simultaneously to reduce processing time, but still process due to the additional time required to secure individual blades to the grinder Time increases. Additional time is also required to encapsulate each of the plurality of blades and later unencapsulate these blades. Further, large batch processing of preforms makes it uneconomical to process fewer blades where less required production is required.

Accordingly, it would be desirable to provide an improved process for electromachining rotor blades to reduce complexity and facilitate efficient production of small batches.
US Pat. No. 6,562,227 US Pat. No. 6,787,728 U.S. Pat. No. 4,851,090

  The preform includes an airfoil stub and a dovetail hub. The hub is first subjected to electrolytic discharge machining to form a rough dovetail. The airfoil stub is subjected to electrolytic processing to form an airfoil. The rough dovetail is then subjected to electrolytic discharge machining to form a rough tongue. The rough tongue is finished to form a dovetail extending from the airfoil in a single rotor blade.

  In accordance with the preferred exemplary embodiments and further objects and advantages of the present invention, the present invention will be specifically described in the following detailed description with reference to the accompanying drawings.

  FIG. 1 shows a workpiece or preform 10 that requires machining to produce a final product, such as a rotor blade 12 used in a gas turbine engine (not shown). As described above, a typical gas turbine engine includes multi-stage compressor rotor blades, such as rotor blades 12, that are suitably mounted around a support rotor disk (not shown).

  The preform 10 includes a first portion in the form of an airfoil stub 14 integrally formed with a second portion in a differently shaped dovetail hub 16. The preform is formed of a suitable metal such as a nickel superalloy having enhanced strength against the adverse environment of the gas turbine engine. The preform can be formed by any known method such as the upsetting process described above.

  The preform is suitably larger in size than the final required rotor blade 12 and the airfoil stub 14 corresponds to the first part of the final product, like the airfoil 18 of the rotor blade, but initially Is slightly larger so that the material can be removed precisely.

  The preform dovetail hub 16, such as both the final dovetail 20 and the integrated platform 22, in the second and other parts of the final product that define the radially inner boundary of the air pressurized in the compressor. Match.

  The rotor blade 12 may be any conventional one in which the airfoil 18 typically extends longitudinally in span from the platform root to the radially outer tip and axially across the chord between the leading and trailing edges. Can have a shape. The airfoil includes a generally concave pressure side and an opposing generally convex suction side that varies in thickness from the leading and trailing edges and from the root to the tip in a general manner.

  The platform 22 is generally rectangular and flat and coincides with the entire perimeter of the entire blade row when mounted around the support disk. The dovetail 20 is conventional, either in the axial or peripheral fit form as shown.

  FIG. 1 schematically shows an electromachining cell 24 that can be conveniently operated by a single operator 26.

  The cell 24 includes a first processing machine 28 that is specifically configured to perform electrolytic discharge machining (ECDM) of the preform 10. The cell also includes a second processing machine 30 that is specifically configured to perform electrolytic machining (ECM) of the airfoil stub 14 to form the final airfoil. The single first processing machine 28 and the single second processing machine 30 can be arranged close to or in the vicinity of each other in a single cell 24 operated by one operator 26.

  The cell 24 enables erosion of the preform 10 in a new and improved sequence for making the final rotor blade 12. The process begins by preparing a platform 10 that has been pre-manufactured in any known manner.

  The preform is initially machined by electrolytic machining of the dovetail hub 16 to form a first or intermediate rough shape or shape, such as the rough dovetail 32, which is the airfoil stub. 14 has a substantially H-contour that crosses 14 or a substantially I-contour that is longitudinally aligned with the stub.

  Next, the preform 10 is removed from the first processing machine 28 by one operator and mounted on the second processing machine 30 where the airfoil stub 14 is subjected to electrolytic processing, leading and trailing edges. A final first part or final airfoil 18 precisely configured with dimensions in the tolerance range of less than a few mils between the edges and from the root to the tip, and along these pressure and suction sides. It is formed.

  Next, the preform is removed from the second processing machine 30 by the operator 26, re-installed on the same first processing machine 28, subjected to the second electrolytic discharge machining of the rough dovetail 32, and the dovetail 20 Form an intermediate second form or shape, such as a rough tongue 34, which is a small rectangular block that closely matches its final envelope surface.

  The second processing machine 30 can have any known configuration for electrolytically processing the airfoil portion of the rotor blade. Moreover, the outer surface of the platform 22 can receive ECM with the same processing machine if necessary. The bottom surface of the platform 22 can also receive ECM on the same processing machine if necessary. The underside of the platform 22 can be formed by a common second ECDM process of the rough tongue 34.

  The particular advantage of combining both the first processing machine 28 and the second processing machine 30 in the common cell 24 is both required when manufacturing the rotor blades 12 sequentially from the corresponding preform 10. This means that a common operator can operate the processing machine. The ECDM process itself is conventional and uses electrical energy to rapidly remove or erode metal from the preform, but the resulting rough surface finish is required by the finished rotor blade 12. It is clearly not acceptable by itself for fine surface finishes and precise dimensions.

  Nonetheless, the two machines are operated to compound electromechanical processing of the preform 10 in multiple stages to quickly remove bulk material from the preform, while precisely finishing the airfoil 18 itself. It takes advantage of the different advantages of two different types of machines 28, 30 to do both processing.

  One or more conventional finishers 36 are then used to finish the rough tongue 34 to provide a final extension that extends below the final airfoil of a single rotor blade having an integral final platform 22. Of the dovetail 20. The finisher 36 can also be used to cut the airfoil to an appropriate length by grinding a portion of the distal tip of the airfoil 18.

  For example, the finisher 36 can be any conventionally configured precision grinding machine and is particularly used to form the final contour of the dovetail 20 having two opposing lobes or tongues, such as precision grinding. Is also effective in removing both the cast layer and the heat affected zone (HAZ) that occur during the ECDM process. ECDM uses high current power that generates a high temperature when the material is eroded from the preform, and a portion of the eroded material is redeposited as a recast layer, which causes the thin tongue 34 to surround the thin tongue. The metallurgical properties of the preform in the heat affected zone are reduced.

  Accordingly, a single electromachining cell 24 shown schematically in FIG. 1 begins with a first processing machine 28 in a preferred embodiment, followed by a second processing machine 30 with a first processing machine 28. Returning, then providing multi-stage or composite electromachining of a single preform 10 in a cyclic process path where the second processor 30 is bypassed and final processing is performed by the finisher 36.

  In FIG. 1, the steps in the different processes for processing the preform 10 sequentially are shown independently. In FIG. 2, the preform 10 is shown in side and cross-sectional views of the final rotor blade 12 that has been machined by removing excess material from the preform. 3-5 illustrate a first ECDM of the hub 16 for forming the rough dovetail 32, followed by a second ECDM of the rough dovetail 32 for forming the rough tongue 34. FIG. 1 schematically shows a first ECDM processing machine 28 specifically configured with suitable means to perform both.

  In order to efficiently perform ECDM with much faster material removal, the first machine 28 shown in FIGS. 4 and 5 has a common rotating spindle or mandrel 38 that is suitably driven by a corresponding electric motor. Including. The mandrel is configured to commonly support both the first electrode tool cutting disc 40 and another axially spaced second electrode tool cutting disc 42. The first disk 40 is specifically configured to perform the first ECDM of the dovetail hub 16 and the second disk 42 is second to the coarse dovetail 32 that is pre-formed by the first ECDM. It is specifically configured to perform ECDM.

  The first processing machine 28 also includes a translation table 44 that can suitably secure and mount one or more of the preforms 10 to engage the spinning or rotating disk during operation.

  As shown in FIGS. 3 to 5, the mandrel 38 is fixedly mounted on the first processing machine 28 at a certain position, and is appropriately driven by an electric motor to rotate the mandrel around the rotation direction or axis A. Both disks 40 and 42 fixedly mounted on the disk 40 are rotated. Correspondingly, the support table 44 is preferably mounted on the first processing machine, preferably for translation of the two axes X and Z, to precisely position the preform and to adjust the ECDM of the preform. The two disks 40 and 42 are engaged separately for execution.

  As will be described further below, the mandrel 38 can be further mounted on the processing machine to periodically oscillate translational movement along the longitudinal or centerline axis Y.

  A suitable electric motor and mechanical drive system 46 is provided for performing and cooperating quaternary motions X, Y, Z, A under the control of a suitable controller 48. The controller 48 is a preferred form of digital computer that performs conventional computer numerical control (CNC) of all operating components of the first machine.

  As shown in FIG. 3, the first processing machine 28 also includes one or more plugs suitably connected to the disks 40, 42 as the cathode (-) and mounted on the table 44 as the anode (+). A conventional DC power supply 50 having a wire suitably connected to the reform 10 is included. The first processing machine 28 is also provided with a suitable coolant supply source 52, which is a small gap maintained between the rotating tool and the preform as the preform undergoes ECDM. Including suitable conduits and nozzles for inducing the appropriate coolant 54 and associated housing.

  The first ECDM machine 28 schematically shown in FIGS. 3 to 5 can be modified from a conventional 3-axis X, Y, Z precision CNC grinder, in which two electrodes The discs 40, 42 are mounted on the mandrel 38 instead of the grinding wheel. The basic grinding machine will then be further modified to include a power supply 50 and a coolant supply source 52 and a periodic vibration axis Y for an optional mandrel.

  The same first processing machine 28 shown in FIG. 3 to FIG. 5 is a 2 for performing the first and second ECDM operations on the same preform 10 in the composite electromachining using the second ECM processing machine 30. Used in two different actions. The first and second ECDM operations are such that differently configured first and second electrode disks 40, 42 rotate at an appropriate speed to electroerode superalloys that exceed the preform at a relatively high material removal rate. First forming a first shaped rough dovetail 32 from the dovetail hub 16 and then forming a different second shaped rough tongue 34, including the ECM of the airfoil Operation takes place between them.

  During ECDM, the coolant source 52 provides a means for circulating the coolant 54 as an electrolyte with the hub 16 as the hub 16 translates with the table 44 across the different spinning disks 40 and 42 in turn. . The power supply 50 powers the hub 16 and the disks 40, 42 to generate or cause electrical sparks and arcing in a small gap maintained between the hub and the spinning disk to electrically erode material from the hub 16. Provide a means to

  Electro-discharge machining (ECDM) is a conventional process that is fundamentally different from conventional electro-chemical machining (ECM) and conventional electro-discharge machining (EDM), and is used to quickly remove material from a work piece. The surface finish, the recast layer of redeposited material and the shallow heat affected zone (HAZ) remain correspondingly.

  Two examples of ECDM are found in US Pat. Nos. 6,562,227 and 6,787,728, both assigned to the assignee of the present invention and incorporated herein by reference. Examples of ECM are found in US Pat. No. 4,851,090, which is also assigned to the assignee of the present invention and incorporated herein by reference. Various functions of these exemplary patents can be incorporated into the first and second processing machines 28, 30 to perform respective ECDM and ECM processes specifically configured for combined electromachining.

  In an effective ECDM, the two electrode discs 40 and 42 are preferably conductive materials with appropriate thermal resistance provided by copper materials or copper and tungsten materials, etc., to improve tool life and usually lower unit prices. Formed with.

  The coolant 54 removes significant heat generated during operation and provides a cutting agent through which an electrical circuit is completed between the preform and the cutting disk. The cooling liquid 54 can extend from the electrolyte to the vicinity of the dielectric, and is preferably a weak electrolyte containing a rust preventive additive. A suitable coolant is an aqueous sodium bicarbonate solution.

  Cooling liquid is injected under pressure into the gap formed between the preform and the spinning disk to complete the electrical circuit and flush away material eroded from the preform during operation. The spinning disk distributes the temperature load around it and helps remove significant heat generated during operation.

  The first processing machine 28 is particularly constructed of a DC power source having a fairly high current capacity of 1,000 to 5,000 amperes, for example about 250 to 900 amperes per square inch, and having an operating voltage range of 5 VDC to 35 VDC. ing.

  The controller 43 of the first processing machine precisely feeds the individual preforms along a linear feed path aligned with the spinning periphery of the electrode disk and generates an electric spark or arc to heat the material from the preform. The translational movement of the support disk table 44 is coordinated so as to maintain a small working gap in between.

  As described above, the ECDM is basically different from the ECM used in the second processing machine 30. The second processing machine 30 shown schematically in FIG. 1 also has a pair of conventional power and liquid electrolyte sources and a pair of airfoil stubs 14 for electrolytic processing material from the airfoil stubs. Corresponding carriages for precisely moving the different electrode tool plates 56 and 58 are included.

  The first plate 56 has a generally convex cutting surface that coincides with or is complementary to the required generally concave pressure side of the resulting airfoil 18. The second plate 58 includes a generally concave cutting surface that complements the generally concave suction side of the airfoil 18.

  The liquid electrolyte 60 is properly circulated between the airfoil stub 14 and the two electrode plates 56, 58 during operation. When power is supplied to the stub 14 as the anode and to the two cutting plates 56, 58 as the cathode, the two plates 56, 58 translate together on both sides of the stub to maintain a small gap through which the liquid electrolyte is circulated. The material is removed electrochemically from 14.

  The second processing machine 30 also co-operates the movement of the electrode plates 56, 58 relative to the stub 14 and intentionally detects any electrical spark or arcing between the plate and the hub during the electrochemical machining operation. And a suitable control device that controls the power supply to avoid it.

  ECM is a precision machining process that precisely removes material from a workpiece while at the same time forming a very smooth surface finish to obtain the required precise final dimensions with tolerances well below a few mils. .

  Accordingly, the first ECDM machine 28 is configured to use rotating cutting discs 40, 42 and further uses high thermal energy found in electrical sparks or arcing between the preform and electrode discs. Particularly configured to rapidly erode material from the reform. In contrast, the second ECM machine 30 utilizes the precise translation of the two electrode plates 56, 58 and uses electrolytic machining without creating a spark between the preform and the electrode plate. Remove material precisely at a corresponding lower speed.

  As shown in FIGS. 3 and 4, the initial preform 10 is appropriately fixed horizontally or laterally from the airfoil stub 14 on the table 44, and one or both sides of the hub are attached to the first rotating disk 40. And the groove 62 is cut there.

  Correspondingly, the first disk 40 shown in FIG. 5 has a smaller diameter side plate (side lands) that is specifically configured to form the required contours or grooves 62 across the sides of the hub 16. It has a peripheral contour with a central flat or ridge 64 bounded on both sides by 66. The maximum depth of the groove 62 can be formed with one pass of the first disk across the dovetail hub.

  This first ECDM operation is available with an oversized airfoil stub 14, so the preform is relatively easy to provide a mechanical clamp on the stub 14 itself to securely attach the preform to the table 44. The first fixing tool 68 can be attached to the table 44.

  The first fixture 68 shown schematically in FIGS. 3 and 4 is adapted to mount a single preform or three small lots of three preforms aligned in a common horizontal plane as required. Can be configured. In this way, the support table 44 translates along the X-axis and first engages one side of the hub 14 around the rotating first disk 40 to provide the first groove 62 therein. Cutting and then passing the same first disk 40 along the opposing second surface of the same hub 14 to cut the same second groove therein.

  FIG. 4 shows that the preform extends laterally outward and protrudes to one side of the table 44, which passes under the first disk 40 that rotates first in one pass, and then Z A groove that is pulled up in the height direction along the axis and passes over the first disk 40 again to face the hub can be formed.

  In this manner, opposing grooves can be formed in the original dovetail hub 16 and a coarse dovetail 32 having opposing grooves 62 on both sides thereof can be formed on the airfoil stub 14. On the other hand, a substantially H-shaped contour is formed in the lateral direction or a substantially I-shaped contour aligned with the stub 14 in the longitudinal direction. Each groove 62 can be formed over the respective surface in a single pass or multiple passes of the first disk.

  The coarse dovetail 32 formed of the first ECDM shown in FIG. 1 then includes opposing first and second grooves 62 on the sides of the hub, which are later referred to as airfoil stubs. 14 can be conveniently used to provide a reference surface for machining. The preform is removed from the first processing machine 28 by the operator and is preferably secured to the second processing machine 30, and the two grooves 32 provide a reference surface against which the airfoil stubs are provided. Machining accurately.

  The coarse dovetail 32 is attached to a suitable fixture 70 with a corresponding groove 62, as shown schematically in FIG. 1, and then the two electrode plates 56, 58 are airfoiled to receive the ECM. The final airfoil 18 can be machined relative to the reference plane defined by the two grooves 62, translating together on both sides of the stub.

  As indicated above, ECM is a conventional process used so far following conventional precision grinding of rough dovetails in conventional practice. However, while the previous rough dovetail was formed by precision grinding, the rough dovetail of the present invention can be formed more quickly and efficiently by ECDM as described above.

  After processing the airfoil 18 in the second processing machine 30, the operator 26 removes the preform from the second processing machine and sends it to the first processing machine 28 for processing the next rough tongue 34. Reinstall the preform. FIGS. 3-5 show a first embodiment in which the preform 10 is now secured vertically from the airfoil 18 previously processed on the table 44 to form the rough tongue 34. The bottom of the rough dovetail 32 is exposed to the second cutting disk 40.

  3-5 also schematically show a second fixture 72, which extends upright from a machine-opened airfoil 18 and table extending downward into the fixture. It can have any suitable shape for clamping individual preforms vertically or upright on the table 44 with the coarse dovetail 32. The second fixture 72 can include suitable mechanical clamps that grip both sides of the airfoil 18, and one or more of the preforms can be mounted in the second fixture 72, Three preforms are mounted there in small lots.

  As described above, the rough dovetail 32 includes a side groove 62 that forms a reference surface used in the second processing machine 30, and the final airfoil 18 is precisely machined with respect to the reference surface. . Correspondingly, the machined airfoil 18 is mounted on the second fixture 72, where the corresponding reference for precisely forming the rough tongue 34 on the airfoil. Provide a plane. Here, since the rough tongue is formed in the second ECDM operation, the conventional encapsulation of the airfoil 18 is no longer required, and therefore the airfoil is second secured without encapsulation. It can be mounted in the tool 72.

  As mentioned above, the airfoil machined in the previous manufacturing process is a soft metal matrix for firm support in the precision grinding machine previously used to form the rough tongue Encapsulation using was required. Grinding places a considerable load on the preform and the encapsulation of the airfoil can easily withstand these applied loads without damaging the pre-machined airfoil.

  The ECDM processor 28 is not only effective for rapid removal of material from the preform, but also a relatively small reaction load that is retained throughout the preform against the mounting fixture due to electroerosion of the preform. Get.

  The second cutting disk 42 is shown in FIGS. 4 and 5 and is specifically configured to conform to the required contour of the rough tongue 34. For example, the second disk 42 has a peripheral profile that includes a central groove 74 bounded on both sides by a larger diameter side disc (side land) 76 best shown in FIG.

  As shown in FIGS. 3 and 5, the second cutting disk 42 is formed of the original rough dovetail 32 that is vertically mounted to the second fixture 72 as the table 44 translates along the X axis. Passing along the exposed bottom, the grooves 62 on both sides and the surrounding material are simultaneously cut from the rough dovetail 32 to form a rough tongue. The central groove 74 and the side lands 76 may be formed in a single pass or as required over the required shape of the rough tongue 34 and the bottom surface of the platform 22, preferably the second disk 43, as shown in FIGS. Depending on the process, it is configured to process in multiple passes.

  The resulting rough tongue 34 is a small rectangular block centered on the underside of the platform 22 that more closely surrounds the desired shape of the final dovetail 20 hidden therein.

  FIGS. 3 to 5 show that several preforms can be simultaneously mounted on the common table 44 using fixtures 68 and 72, respectively. In this manner, the same ECDM machine 28 can operate with two different cutting tools 40, 42 to machine the preform at various stages to maximize efficiency.

  For example, FIG. 4 shows machining during some steps of the preform, first forming one of the grooves on the side of the hub 16 and then forming opposing grooves on both sides of the hub. After the rough dovetail 32 has been processed in this way, the dovetail is sent to the second processing machine 30 shown in FIG. 1, where the airfoil 18 is precisely processed. These preforms are then returned to the same first processing machine 28 shown in FIG. 4, where a second fixture 72 specifically configured to mount the machined airfoil 18 is applied. Will be mounted again.

  However, it is also possible to mount a plurality of preforms 10 to the first fixture 68 so that both fixtures contain all of the preforms at various processing stages. Next, the first processing machine 28 shown in FIG. 5 can be operated to process the rough dovetail 32 using the second cutting disk 42 to form the rough tongue 34.

  In this way, the same ECDM machine 28 first processes the rough dovetail 32 from the original airfoil stub 14 and then from the pre-processed rough dovetail 32 to the rough tongue 34. And subsequently used in successive stages to pre-electrolyze the airfoil 18 from the corresponding airfoil stub 14.

  The coarse dovetail 32 can be formed with one pass of the corresponding first cutting tool 40, and the rough tongue 34 can also be formed with one pass of the second cutting disk 42. Alternatively, multiple passes of these cutting tools 40, 42 can be used to form rough dovetails and tongues as required with continuous skim cuts.

  For example, the first cutting disc 40 shown schematically in FIG. 4 cuts the grooves 52 in a continuous pass on both sides of the hub, and more precisely the resulting grooves 62 with lateral vibration along the Y axis. Can be configured and operated during the ECDM process. The first disk 40 can be operated to initially cut the grooves 62 slightly shorter than the depth required for them. The second pass of the first disk 40 is then used to cause the first disk to oscillate appropriately and quickly across the sides to machine a relatively thin skim cut on each opposing surface of the groove 62. It can be removed by machining to improve the finish of its reference surface.

  The grooves 62 and their reference surfaces are required for subsequent processing of the airfoil 18 in the second processing machine 30 and are no longer required thereafter. Accordingly, the second cutting disk 42 is configured to simultaneously cut both grooves 62 of the rough dovetail 32 to form a simple rectangular block of rough tongue 34.

  Next, as shown above with respect to FIG. 1, the preform 10 with the finished airfoil 18 and the rough tongue 34 is removed from the first processing machine 28, and subsequently as needed. Mounted on one or more of the finishing machines 36, the rough tongue 34 is machined to the final shape of the dovetail 20, and the machine is simultaneously recast as found in the rough tongue. And HAZ is removed. The pre-machined airfoil 18 can be used on a finishing machine 36 to provide a reference surface for finishing the dovetail 20 in a conventional manner.

  The composite electromachining cell 24 shown schematically in FIG. 1 is a first ECDM processing machine 28 for one operator to process one or more of the preforms in a continuous and efficient manner. And the second ECM processing machine 30 can be efficiently managed. Using the first processing machine 28, the airfoil stubs are formed in multiple stages, first forming the coarse dovetail 32 and then forming the rough tongue 34 following the intermediate electrolytic machining of the airfoil 18. Facilitates the rapid removal of material from 14.

  These sequences are performed using relatively simple fixtures on both machines to eliminate the need for encapsulation of the machined airfoil 18 to form the rough tongue 34. Can do.

  The two cutting discs 40, 42 can be configured separately to machine the required shape of the side grooves of the rough dovetail 32 and the required shape of the rough tongue 34. The two disks 40, 42 can operate in multiple passes to machine the dovetail hub at each stage with a final skim cut of less than about 20 mils.

  The vibration of the first disk 40 can be used in a single pass in roughing each of the opposing grooves 62 to improve the surface finish of these grooves. In this way, skim cut can be eliminated.

  However, a slightly improved surface finish of the two grooves 62 can be obtained if the vibration of the first tool 40 is performed during a skim cut to finish these grooves. Further, the wear of the disk side wall can be compensated by utilizing the vibration of the tool.

  If necessary, an abrasive wheel pack (not shown) is additionally mounted on the mandrel using the same mandrel 38 shown in FIGS. 4 and 5 and the required dovetail from the rough tongue 34. 20 can be finish ground. This eliminates downstream operations in the manufacturing process.

  However, the mandrel 38 will then be configured to rotate at a speed that greatly exceeds the speed required to rotate the two disks 40, 42 during ECDM. It should be about 3,000 RPM or more required for grinding.

  Thus, the composite electromachining cell disclosed above provides many significant advantages in the in-process manufacture of compressor rotor blades from corresponding preforms. The attendant advantages include reduced processing time, reduced associated costs, and increased flexibility in processing individual or small lot rotor blades that do not require large inventory of preforms and resulting processing blades.

  While preferred and illustrative embodiments of the invention have been described herein, other modifications of the invention will be apparent to those skilled in the art from the teachings herein and as such, All such modifications within the true spirit and scope should be protected in the appended claims.

  Accordingly, what is desired to be protected by Letters Patent is the invention as defined and identified in the accompanying claims.

4 is a schematic flowchart of a method for manufacturing a rotor blade from an initial preform. FIG. 2 is a partial cross-sectional view of the preform shown in FIG. 1 and a finally constructed roller blade machined therefrom and resulting. FIG. 2 is a schematic front view of the ECDM processing machine shown in FIG. 1 for removing material from a preform. FIG. 4 is a schematic front view of the ECDM processing machine shown in FIG. 3 and taken along line 4-4. FIG. 5 is a side view of the ECDM processing machine shown in FIG. 3 and similar to FIG. 4 showing another use of the processing machine in removing material from the preform.

Explanation of symbols

10 Preform 12 Rotor Blade Product 14 Airfoil Stub 16 Dovetail Hub 18 First Part-Airfoil 20 Second Part-Dovetail 22 Platform 24 Electromechanical Cell 26 One Operator 28 First Machine 30 Second processing machine 32 First shape-rough dovetail 34 Second shape-rough tongue 36 Finishing machine 38 Mandrel 40 First cutting disk 42 Second cutting disk 44 Translation table 46 Drive system 48 Control Device 50 Power Supply 52 Coolant Supply Source 54 Liquid Coolant 56 First ECM Plate 58 Second ECM Plate 60 Liquid Electrolyte 62 Groove 64 Raised Portion 66 Side Land 68 First Fixture 70 ECM Fixture 72 Second 2 fixtures 74 center groove 76 side land

Claims (10)

A method for producing a rotor blade (12), comprising:
Providing a preform (10) comprising an airfoil stub (14) and a dovetail hub (16);
Performing a first electrolytic discharge machining (ECDM) of the hub (16) using a first rotating electrode disk (40) to form a rough dovetail (32);
Electrolytically machining (ECM) the stub (14) to form an airfoil (18);
Performing a second electrolytic discharge machining (ECDM) of the rough dovetail (32) using a second rotating electrode disk (42) to form a rough tongue (34);
Finishing the rough tongue (34) to form a dovetail (20) extending from the airfoil (18) with a single rotor airfoil (12);
Including methods.
Said first disc (40) comprises a peripheral profile having a central ridge (64) bounded on both sides by a disc (66) of smaller diameter;
The second disk (42) includes a peripheral profile having a central groove (74) bounded on both sides by a larger diameter disk (76);
The method according to claim 1. Passing the first disk (40) along a first side of the hub (16) to cut a first groove (62) in the hub;
Cutting the second groove (62) by passing the first disk (40) along the opposing second side of the hub (16);
The second disc (42) is passed along the bottom of the rough dovetail (32) to cut both the first and second grooves (62), and the rough tongue (34). )
The method of claim 2 further comprising: Circulating an electrolyte coolant (54) between the hub (16) and the disk (40, 42);
Powering the hub (16) and the disk (40, 42) to create an electrical spark between them and electroeroding material from the hub (16);
Translating a pair of electrode plates (56, 58) together on both sides of the stub (14);
Circulating an electrolyte (60) between the stub (14) and the plate (56, 58);
Powering the stub (14) and the plates (56, 58) to electrochemically remove material from the stub (14) to form the airfoil (18) while avoiding sparks; ,
The method of claim 3 further comprising: Fixing the stub (14) on a support table (44) adjacent to a mandrel (38) supporting the disc (40, 42) in an ECDM machine (28);
The shaft (38) and the discs (40, 42) are rotated, the table (44) and the preform (10) are translated, and the groove (62) is cut in the hub (16). Forming a coarse dovetail (32);
The method of claim 4 further comprising: The preform (10) is fixed laterally from the stub (14) on the table (44), and one side of the hub (14) is exposed to the first disk (40). The groove (62) is cut into
The preform (10) is fixed vertically on the table (44) from the airfoil, with the bottom of the coarse dovetail (32) exposed to the second disk (42). From there, forming the rough tongue (34),
6. The method of claim 5, wherein: The rough dovetail (32) includes the first and second grooves (62) forming reference surfaces on both sides thereof;
The coarse dovetail (32) is secured to the groove (62) during the ECDM to form the airfoil (18) relative to the reference plane;
The method according to claim 6.   The method of claim 7, wherein the airfoil (18) is secured between the second ECDMs to form the rough tongue (34) thereto.   9. The step of finishing the rough tongue (34) includes the step of precision grinding the rough tongue to remove a recast zone and a heat affected zone due to the ECDM. the method of. The first and second ECDMs are performed using a single ECDM machine (28) for both operations;
The ECM is performed using an ECM machine (30) located near the ECDM machine (28) in a common cell (24) controlled by a single operator (26).
The method of claim 9.

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