A multi-station forming electrode synchronous electrical discharge machining device and method for turbine blades

Abstract

This invention relates to a multi-station synchronous EDM device and method for forming electrodes on turbine blades, effectively solving the problems of complex positioning operations and low processing efficiency of forming electrodes in the machining of complex and irregularly shaped parts. A multi-station fixture with XY-axis fine-tuning is used to clamp and position the blades. A vision recognition camera is used to identify the positioning parameters of the turbine blade parts to be machined. Multiple blades are simultaneously machined using a multi-station forming electrode. The multi-station fixture includes one fixed station and multiple fine-tuning stations. During machining, each blade is first clamped. The off-axis vision recognition camera is activated to identify the position of the fixed station in the camera's field of view. Using this as a reference, the positioning points of the other fine-tuning stations are calibrated using the relative coordinates of the multi-station forming electrode machining head. The field of view is moved to the theoretical position of the corresponding fine-tuning station, and the coordinates of each fine-tuning station are adjusted and fixed using XY-axis fine-tuning. Finally, the parts to be machined are machined synchronously.

Description

Technical Field

[0001] This invention relates to an apparatus and method for synchronous electrical discharge machining of multi-station forming electrodes for parts, mainly relating to the field of aero-engine parts processing and repair, and particularly to a multi-station synchronous machining apparatus for precision forming electrodes of turbine blades. Background Technology

[0002] When an aero-engine is working, the turbine blades, as one of the hot-end flow channel components, mainly function to adjust the airflow direction and convert the kinetic and thermal energy of the high-temperature and high-pressure gas into the kinetic energy of the blade rotor. Therefore, the geometric dimensions of the blades are a key product feature that needs to be guaranteed during the manufacturing and repair process. Especially for high-thrust aero-engines, the turbine blade geometry is complex and requires precise machining and inspection to ensure that the manufactured and repaired products can achieve the design performance.

[0003] High-performance aero engines often use thin-walled hollow blades as hot-end components, and the proper flow of their cooling channels is a crucial prerequisite for providing adequate cooling performance. During service, blades often wear down, leading to shortening. The commonly used industrial laser cladding process can easily clog the blade tip film cooling channels, especially the exhaust side airflow channels, due to excessively wide weld beads. When using electrical discharge machining (EDM) to repair blade tip airflow channels, the individual differences between blades prevent the use of uniform positioning parameters for batch processing, requiring significant time for positioning and resulting in low manufacturing efficiency. Tests have shown that using visual positioning and single-piece machining methods, the machining time for a single piece can reach 50 minutes.

[0004] Chinese Patent CN206123248U (published on April 26, 2017) discloses a multi-station rapid pneumatic positioning and clamping device for machining aero-engine parts. The device includes a horizontally positioned base. A first positioning and clamping mechanism is located at the left end of the upper surface of the base, a second positioning and clamping mechanism at the right end of the upper surface, and a third positioning and clamping mechanism in the middle of the upper surface. The first and second positioning and clamping mechanisms are located to the left and right of the third positioning and clamping mechanism, respectively. This patent allows for the simultaneous machining of three identical parts at one different station in a single clamping operation. After three clamping operations, the machining of three faces and holes of the three parts can be completed. It offers accurate positioning and high machining precision, significantly improving machining efficiency in mass production.

[0005] Chinese patent CN212600455U (published on February 26, 2021) discloses a multi-piece positioning and clamping device for thin-sheet aerospace parts, including a clamping body, a rectangular pressure block, a base, a hydraulic device, threaded sleeves, support rods, and pressure plates. The base is snapped into the front side wall of the clamping body, and the hydraulic device is fixedly connected to the middle of the base. The bottom end of the hydraulic device abuts against the inner front wall of the base. A slot is formed on the outer wall of the middle front section of the rectangular pressure block, and the hydraulic rod of the hydraulic device is inserted into the slot on the outer wall of the middle front section of the rectangular pressure block. Multiple sets of threaded sleeves are welded to the outer rear wall of the rectangular pressure block. Each set of threaded sleeves is threadedly connected to a support rod, and a pressure plate is welded to the outer wall of the first end of each set of support rods. Sliding grooves are formed on both side walls of the clamping body. This patented device facilitates the simultaneous clamping of multiple sets of thin-sheet parts and has strong applicability.

[0006] While the aforementioned patents have improved processing efficiency to some extent, they still suffer from problems of complex operation and low efficiency when considering both positioning accuracy and teaching efficiency. Summary of the Invention

[0007] This invention provides a multi-station synchronous EDM device and method for turbine blade forming electrodes, effectively solving the problems of complex positioning operations and low forming electrode processing efficiency in the machining of complex and irregularly shaped parts. A multi-station fixture with XY-axis fine-tuning is used to clamp and position the blades. A vision recognition camera identifies the positioning parameters of the turbine blade's workpiece. Multiple blades are simultaneously machined using the multi-station forming electrode. The multi-station fixture includes one fixed station and multiple fine-tuning stations. During EDM, each blade is first clamped. The off-axis vision recognition camera is activated to identify the position of the fixed station within the camera's field of view. Using this as a reference, the positioning points of the other fine-tuning stations are calibrated using the relative coordinates of the forming electrode multi-station machining head. The blades are moved to their theoretical positions, and the XY-axis fine-tuning is used to adjust and fix the coordinates of each fine-tuning station. Finally, the workpieces are machined synchronously.

[0008] This invention is achieved through the following technical solution:

[0009] A synchronous electrical discharge machining (EDM) device for multi-station forming electrodes of turbine blades includes an optical positioning module, a complete set of multi-station clamping fixtures, and a set of multi-station forming electrodes.

[0010] The optical positioning module includes an optical camera and a data cable, and an optical camera mounting bracket. The mounting bracket is used to rigidly connect the optical camera to the fixed part of the equipment platform. The connection can be made by welding or bolts. The optical axis of the optical camera lens is parallel to the Z-axis of the equipment electrode processing.

[0011] The multi-station clamping fixture includes a set of mounting base plates, a set of fixed clamping single-station fixtures, and multiple sets of multi-station fixtures with XY two-axis fine adjustment.

[0012] The fixed clamping single-station tooling and the mounting base can be connected by welding or other methods, or they can be machined from a single piece of raw material. The mounting groove of the fixed clamping single-station tooling matches the geometric shape of the blade tenon groove and presses and fixes the blade from the Z-axis direction. The mounting base has structures such as threaded holes and can be fixedly connected to an electrical discharge machining tool. The clamping reference surface of the fixed clamping single-station tooling and the other multiple sets of multi-station tooling with XY two-axis fine adjustment is at the same horizontal height.

[0013] The multi-station tooling with XY two-axis fine adjustment is connected to the mounting base plate by XY two-axis translation guide rails. Each station tooling is equipped with a blade locking device and a station locking device. The blade locking device has the same structure as the blade locking device for fixing and clamping a single station tooling. The station locking device can realize station locking and fixing at any position within the working range of the translation guide rail.

[0014] The multi-station forming electrode has an array of processing structures, and each processing structure can be geometrically arranged using methods such as circular array, matrix array, or equidistant linear arrangement.

[0015] Furthermore, the electrode processing structure spacing design is jointly determined by the blade size, clamping direction, and clamping spacing of the multi-station tooling used for blade clamping.

[0016] Furthermore, the formed electrode can be precision machined from a single piece of electrode material, or it can be a combination electrode with a replaceable structure.

[0017] The beneficial effects of this invention are:

[0018] This invention uses a vision-based machining head positioning method, which can significantly improve machining accuracy; secondly, the use of arrayed multi-station tooling can realize the machining of multiple parts at once, significantly improving machining efficiency; finally, the use of a multi-station clamping tooling design based on a small-range translation guide rail can realize flexible machining of individual differences in the repair blades. Attached Figure Description

[0019] Figure 1 Overall structural diagram of the invention;

[0020] Figure 2 Schematic diagram of a rangefinder camera and its high-rigidity mounting base;

[0021] Figure 3 Schematic diagram of a single-station tooling with XY-axis fine-tuning;

[0022] Figure 4 Schematic diagram of mounting base plate and fixing clamping single-station tooling;

[0023] Figure 5 Schematic diagram of multi-station forming electrode. Detailed Implementation

[0024] The technical solution of the present invention will be further described in detail below with reference to examples of the present invention, but the scope of protection of the present invention is not limited to the products and methods described below.

[0025] See Figure 1-5 As shown, a synchronous EDM device for four-station forming electrodes of turbine blades includes a lateral positioning camera 1 and a high-rigidity mounting base 2, a mounting base 3 and a fixed clamping single-station fixture 4, three sets of single-station fixtures 5 with XY two-axis fine adjustment, and a multi-station forming electrode 6. The mounting base 3 and the base of the fixed clamping single-station fixture 4 are machined from the same piece of steel. The high-rigidity mounting base 2 ensures that after the lateral positioning camera 1 is installed, its optical axis remains parallel to the Z-axis of the machine tool during use and does not experience image drift due to vibration. The three sets of single-station fixtures 5 with XY two-axis fine adjustment are designed with translation guides for two-axis fine adjustment at the bottom and are rigidly connected to the mounting base 3 by bolts. The blade tenon mounting mortise design is the same for the fixed clamping single-station fixture 4 and the two-axis fine adjustment single-station fixture 5, and there is a lifting clamping block at the bottom, with the reference end faces at the same height. The base plate of the two-axis fine-tuning single-station tooling 5 is designed with adjustment and fixing structures 7, which can be adjusted arbitrarily within the working window and locked at any position. The forming electrode 6 is precision machined from the same piece of high-purity copper. There are four processing structures at the bottom. The geometry of the structure in the XY plane is consistent with the geometry of the blade to be processed. The tip uses a wedge design. The horizontal and vertical spacing of the reference points of the four processing structures is consistent with the tooling spacing, and the orientation angle is 90°.

[0026] Follow these steps to use it:

[0027] Step 1: Part Pre-treatment

[0028] For turbine blades that require electrode forming, pre-processing is performed on the parts to be processed to ensure that the blade height is consistent. The height difference between different blades should be within 0.01mm. If this is not met, the blades should be measured, selected and sorted from the same batch of products to be processed.

[0029] Step 2:

[0030] Install four blades onto the fixed clamping single-station fixture 4 and three sets of single-station fixtures 5 with XY two-axis fine adjustment, and clamp them securely.

[0031] Step 3:

[0032] Turn on the off-axis positioning camera 1, move the machine tool to the blade tip reference point position of the blade held by the fixed clamping single-station tooling 4, obtain the processing position of the blade, and calculate the geometric coordinates of the other three blades to be processed based on the relative position difference of the four processing structure reference points of the forming electrode 6.

[0033] Step 4:

[0034] The three single-station fixtures with XY two-axis fine adjustment are moved sequentially to the reference coordinates calculated in step 3, and the blades are adjusted using the XY fine adjustment structure so that the image of the blade reference point coincides with the calculated reference point. The fixtures are then locked using the fixing structure 7 of the single-station fixture 5 with XY two-axis fine adjustment.

[0035] Step 5:

[0036] Move all the tooling that is fixed in place to the processing position. The translation distance is determined by the difference between the reference coordinates of the forming electrode 6 and the optical axis center position of the off-axis positioning camera 1. Then, process according to the designed process parameters.

[0037] The above description is merely a typical embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A synchronous electrical discharge machining (EDM) device for multi-station forming electrodes of turbine blades, characterized in that: The system includes a rangefinder positioning camera (1) and a high-rigidity mounting base (2), a set of mounting base plates (3) and a set of fixed clamping single-station fixtures (4), three sets of single-station fixtures with XY two-axis fine adjustment (5), and a multi-station forming electrode (6). The base of the mounting base plate (3) and the fixed clamping single-station fixture (4) are machined from the same piece of steel. The high-rigidity mounting base (2) can ensure that the optical axis of the rangefinder positioning camera (1) is always parallel to the Z-axis of the machine tool and does not cause image drift due to vibration during use after the rangefinder positioning camera (1) is installed. The three sets of single-station fixtures with XY two-axis fine adjustment (5) are designed with two-axis fine adjustment translation guides at the bottom and are rigidly connected to the mounting base plate (3) with bolts. The blade tenon mounting groove design is the same for the fixed clamping single-station tooling (4) and the single-station tooling with XY two-axis fine adjustment (5). There is a lifting and clamping block at the bottom, and the reference end face is at the same height. The base plate of the single-station tooling with XY two-axis fine adjustment (5) is designed with adjustment and fixing structure (7), which can be adjusted arbitrarily within the working window and locked at any position. The forming electrode (6) is precision machined from the same piece of high-purity copper. There are four processing structures at the bottom. The geometry of the processing structure in the XY plane is consistent with the geometry of the blade to be processed. The tip uses a wedge design. The horizontal and vertical spacing of the reference points of the four processing structures is consistent with the tooling spacing, and the orientation angle is 90° respectively.

2. A method for simultaneous electrical discharge machining of multi-station forming electrodes for turbine blades, characterized in that: The turbine blade multi-station forming electrode synchronous electrical discharge machining apparatus according to claim 1 is characterized by comprising the following steps: Step (1): Part pretreatment. The turbine blades that need to be shaped and processed are pretreated to ensure that the blade height is consistent. The height difference between different blades should be within 0.01mm. If not, the parts are measured, selected and sorted from the same batch of products to be processed. Step (2): Install 4 blades to the fixed clamping single-station fixture (4) and three sets of single-station fixtures with XY two-axis fine adjustment (5) respectively, and clamp them in place; Step (3): Turn on the off-axis positioning camera (1), move the machine tool to the blade tip reference point position of the blade held by the fixed clamping single-station tooling (4), obtain the processing position of the blade, and calculate the geometric coordinates of the other three blades to be processed based on the relative position difference of the four processing structure reference points of the forming electrode (6). Step (4): Move the three sets of single-station tooling with XY two-axis fine adjustment to the reference coordinates calculated in step (3) in sequence, and use the XY fine adjustment structure to adjust the blade so that the image of the blade reference point coincides with the calculated reference point, and use the adjustment and fixing structure (7) of the single-station tooling with XY two-axis fine adjustment (5) to lock it. Step (5): Move all the tooling that is fixed in place to the processing position. The translation distance is determined by the difference between the reference coordinates of the forming electrode (6) and the optical axis center position of the off-axis positioning camera (1). Then process according to the designed process parameters.

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