• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    Method for positioning a hollow part obtained by casting to accurately machine the part thus obtained, wherein said part (1) was obtained by a casting process involving a mold and a sacrificial core introduced into the mold and forming at least one cavity (10) of said workpiece (1), wherein said workpiece (1) comprises surfaces of a first type defined at the casting by the surfaces of the mold, and surfaces of a second type, defined during the foundry by the surfaces of the core, and in which a reference frame is constructed for the part comprising at least three points (P1-P3) belonging to surfaces of the second type of the part (1) .
    公开号:FR3067955A1
    申请号:FR1755774
    申请日:2017-06-23
    公开日:2018-12-28
    发明作者:Matthieu Jean Luc Vollebregt；Coralie Cinthia Guerard；Patrick Emilien Paul Emile Huchin；Joseph Toussaint TAMI LIZUZU
    申请人:Safran Aircraft Engines SAS；
    IPC主号:
    专利说明:

    FIELD OF THE INVENTION The present disclosure relates to a method of positioning a hollow part obtained by foundry making it possible to precisely machine the part thus obtained.
    Such a method can be used to position any type of hollow parts obtained by foundry, and very particularly those having a complex geometry, in particular in the aeronautical field: it can thus be rotor or stator hollow blades, for cite only these examples.
    STATE OF THE PRIOR ART In the aeronautical field, as in other fields, it is usual to position and orient a part using a mark of several points chosen on the walls of the part seen of its machining. Thus, by blocking the position of the reference points, using a tool for example, the whole part is blocked in a predetermined position and orientation, which makes it possible to carry out precision machining, such as drilling or cuts, with very small margins of error.
    Usually, the reference points are defined on the surfaces of the part obtained from the foundry: the knowledge of the dispersions of the dimensions and coasts of the raw foundry parts thus makes it possible to ensure sufficient precision on the positioning and the orientation. of the part and therefore on the machining carried out on the latter.
    However, such traditional positioning marks find their limits for hollow parts with complex geometry. In particular, in the aeronautical field, the geometry of certain hollow parts, and very particularly of the cavities of these hollow parts, is increasingly complex in order to optimize their functions.
    For example, FIG 1 shows a hollow turbine blade 1. The latter comprises a complex network of cavities 10, the geometry of which is provided to optimize the cooling of the blade 1 in service. These vanes 1 can then comprise internal structures of great finesse with, for example, walls 11 whose thickness does not exceed 0.5 mm.
    However, some of these internal structures must be machined, and in particular drilling, to connect for example certain cavities 10 between them. For example, FIG 3 very schematically represents a complicated situation in which an internal wall 11 separating two cavities 10a and 10b must be drilled longitudinally to connect two other cavities 10c and 10d.
    We immediately understand that the part must be extremely precisely positioned and oriented so that the hole 19, of great length, does not deviate from its theoretical layout and does not pierce the wall 11 to open into an undesired cavity 10a or 10b.
    Most often, these hollow parts are obtained by foundry using one or more sacrificial cores arranged in the shell forming a mold before casting the molten metal. Thus the actual position of the internal walls such as the wall 11 of FIG 3 depends on the position of the core in the shell at the time of casting. However, it is rarely possible to be certain that the core is exactly in its theoretical position at the time of casting, the core having been able to be positioned with a slight margin of error or possibly being able to be slightly displaced during casting, all respecting the tolerances of the dimensions. Therefore, even if this margin of error is generally minimal, typically less than a millimeter, it can cause a sufficient gap between the positioning reference of the part and the exact position of the internal structures to generate a risk of defect during the 'machining, for example when drilling a particularly thin internal wall 11.
    There is therefore a real need for a method of positioning a hollow part obtained by foundry which is devoid, at least in part, of the drawbacks inherent in the aforementioned known method.
    PRESENTATION OF THE INVENTION The present disclosure relates to a method of positioning a hollow part obtained by foundry, in which said part was obtained by a foundry process involving a mold and a sacrificial core introduced into the mold and making it possible to form at least one cavity of said part, in which said part comprises surfaces of a first type, defined during the foundry by the mold surfaces, and surfaces of a second type, defined during the foundry by the surfaces of the core, and in which a reference frame for positioning the part is constructed comprising at least three points belonging to surfaces of the second type of the part.
    Thus, the surfaces of the first type are those which were in contact with the wall of the mold, most often a shell of refractory material, at the end of the steps of casting the metal and cooling the part: they constitute so in general of the external surfaces of the part. Conversely, the surfaces of the second type are those which were in contact with the sacrificial core, most often a ceramic core, at the end of the steps of casting the metal and cooling the part: they therefore generally constitute internal surfaces of the room.
    Since these points belong to surfaces of the second type, their position completely depends on the position of the core during the foundry so that this reference frame of points is directly linked to the geometry of the cavities and internal walls of the room. In other words, this repository of points makes it possible to locate and orient precisely and directly the internal structures of the part without being subjected to the vagaries of positioning of the core during the foundry.
    Thus, it is possible to use such a positioning reference frame for positioning and orienting the part so as to carry out precise machining operations on internal structures of the part: for example, it becomes possible to drill certain walls longitudinally internal of the part by reducing, or even completely eliminating, the risk that the hole deviates from its theoretical layout and cuts a portion of unwanted material or opens into an undesired cavity.
    In addition, in this type of foundry process using a sacrificial core, it is generally found that the shrinkage of the metal after cooling is much less, if not completely nonexistent, when interface with the core than with the interface with the mold. Thus, the surfaces of the second type undergo much less dispersion than the surfaces of the first type during cooling. Consequently, such a reference frame of points based on surfaces of the second type is more precise since the need to take into account the dispersion of the ribs of the part during cooling is reduced.
    Such a repository also makes it possible to precisely machine the external surfaces of the part, of the first type, while ensuring that the theoretical dimensions with the internal structures of the part are well respected.
    In some embodiments, the positioning reference system comprises at least five points, preferably six points, belonging to surfaces of the second type of the part. Six points are used to block the six degrees of freedom of the part: its three degrees of translation and its three degrees of rotation.
    In certain embodiments, the positioning reference frame does not include any point belonging to surfaces of the first type of the part. This avoids introducing positioning inaccuracies related to the uncertainty of the positioning of the core in the mold on the one hand, and to the dispersion of the ribs of the surfaces of the first type during cooling on the other hand.
    In some embodiments, each point of the positioning reference frame is located on a locally planar surface. By “locally planar surface” is meant a surface on which a setting member for a tool can be wedged in order to position and orient the part. Typically, a flat surface of about 5 mm 2 around said point is sufficient to allow the effective setting of such a tool.
    In some embodiments, all the points of the positioning reference frame are located on the final surfaces of the part. “Final surface” means a surface which will not be machined. Thus, the position of the point in question is not likely to be affected by a possible machining of the part which can locally modify the dimensions of the part and therefore generate a shift between the reference frame of points and the machined part.
    In some embodiments, each point of the positioning reference frame is accessible from outside the room. More specifically, the term "accessible from outside the room" means the fact that a setting device of a tool can be positioned and wedged on the points of the frame of reference. There is therefore a path, forming a passage of at least 10 mm 2 in section, connecting the point in question to the outside of the part. Preferably, the direction normal to the part extending from a point of the reference frame is cleared to the outside of the part: in other words, this normal direction extends to the outside of the part without encountering any obstacle belonging to the room.
    In some embodiments, at least three points of the positioning reference frame have directions normal to the part substantially collinear to a first direction. By "substantially collinear with a given direction" is meant that the direction which one considers forms an angle less than 10 ° with this given direction. This defines a plane against which the part is forced to position itself by pushing it in the first direction.
    In certain embodiments, at least two of these three points of the positioning reference frame, and preferably each of these three points, are separated by a distance at least equal to 20%, preferably at least equal to 40% , from the largest dimension of the part in the directions orthogonal to the first direction. In other words, we are looking for the largest dimension of the part when we run through all the planes orthogonal to the first direction. Indeed, the more these points are distant from each other, the better will be defined the plane against which the part must be pressed and therefore more precise will be the positioning of the part.
    In some embodiments, at least two points of the positioning reference frame have directions normal to the part substantially collinear with a second direction, this second direction forming an angle greater than 45 ° with the first direction. A straight line is thus defined against which the part is wedged by pushing it in the second direction, the part remaining wedged elsewhere against the plane defined by the first three points mentioned above.
    In some embodiments, these two points are separated by a distance at least equal to 20%, preferably at least equal to 40%, of the largest dimension of the part in the directions orthogonal to the second direction.
    In some embodiments, at least one point of the positioning reference frame has a direction normal to the workpiece substantially collinear with a third direction, this third direction forming an angle greater than 45 ° with the plane formed by the first and second directions. It is thus possible to wedge the part against this point by pushing it in the third direction, the part remaining wedged elsewhere against the plane and the line defined respectively by the three points and the two points mentioned above.
    In certain embodiments, the core defines a wall of the part, at least two faces of which are surfaces of the second type. It can be two opposite sides. The present method is particularly useful when such a wall is to be drilled, particularly when this drilling is longitudinal and of great length within the wall.
    In some embodiments, the thickness of said wall is less than 1mm, preferably less than 0.5mm.
    In some embodiments, the core includes several separate core elements.
    In some embodiments, at least three points, preferably five points, more preferably six points, of the positioning reference frame belong to surfaces of the second type defined during the foundry by the same core element.
    In some embodiments, the part is a turbomachine blade. It can be a moving blade, belonging to the rotor, or a fixed blade, flat to the stator. It may in particular be a turbine blade. However, the present description can also apply to any type of hollow part.
    In some embodiments, said blade comprises a leading edge, a trailing edge, a lower surface, an upper wall, a blade head and a blade root.
    In certain embodiments, the blade head comprises a bath comprising a bottom wall and side walls.
    In some embodiments, at least one point of the positioning reference frame, and preferably two points, is located on the internal surface of the upper surface wall at the trailing edge.
    In some embodiments, at least one point of the positioning reference frame is located on the internal surface of the upper wall within the bathtub.
    In some embodiments, at least one point of the positioning reference frame, and preferably two points, is located on the upper end edge of the lower surface wall, preferably at the bottom of a notch.
    In some embodiments, a point of the positioning reference frame is located on the rear end stop of the lower surface wall.
    In some embodiments, the method further comprises a step of positioning the part on a tool, said tool comprising as many setting members as points in the positioning reference frame, a setting member being positioned on each of the points of the part positioning reference system.
    In some embodiments, said tool is a tool for machining, preferably drilling.
    The present disclosure also relates to a method of machining a hollow part obtained by foundry, comprising a positioning step according to any one of the preceding embodiments, and a drilling step in which a hole is drilled in an internal wall of the part, at least two faces of which are surfaces of the second type. This hole can extend over at least 3 cm long, or even at least 5 cm long.
    The aforementioned characteristics and advantages, as well as others, will appear on reading the detailed description which follows, of an exemplary embodiment of the proposed method. This detailed description refers to the accompanying drawings.
    BRIEF DESCRIPTION OF THE DRAWINGS The attached drawings are schematic and aim above all to illustrate the principles of the invention.
    In these drawings, from one figure (FIG) to another, identical elements (or parts of elements) are identified by the same reference signs.
    FIG 1 is a perspective view of a hollow blade.
    FIG 2 is a cross-sectional view of such a hollow blade.
    FIG 3 is a diagram in longitudinal section of such a hollow blade.
    FIG 4 is a perspective view of such a hollow blade provided with a positioning reference frame.
    DETAILED DESCRIPTION OF EMBODIMENT (S) In order to make the invention more concrete, an example of a positioning method is described in detail below, with reference to the accompanying drawings. It is recalled that the invention is not limited to this example.
    In this example, the positioning method relates to a hollow blade 1 of the HP turbine of an aircraft turbojet. This hollow blade 1 is shown in FIG 1. It is here a movable blade comprising in a single piece a blade root 2 in dovetail, allowing its attachment to the rotor disc of the turbine, a blade part 3 and a platform 4 extending transversely between the blade root 2 and the blade part 3.
    As is best visible in FIG 2 which shows the blade portion 3 in cross section, the blade 1 comprises a plurality of cavities 10 for circulating a cooling fluid in the blade 1 in order to cool this last during the operation of the turbojet engine. Conventional, fresh air is injected into the blade 1 via several conduits crossing the blade root 2, then this fresh air circulates within the cavities 10 of the blade part 3 and is evacuated by small orifices made in the outer walls of the blade part 3, especially along its trailing edge.
    These cavities 10 thus define therebetween internal walls 11 separating the different cavities 10.
    Such a hollow blade can be manufactured using a conventional lost wax casting technique using a sacrificial core. As a reminder, the main steps of such a process are as follows: production of a first mold having the external geometry of the blade to be manufactured; establishment of a previously manufactured ceramic core whose geometry corresponds, in negative, to the geometry of the cavities of the blade to be manufactured; injection of a wax into the mold then cooling and obtaining a dawn wax model integrating the ceramic core within it; coating the model in wax using a slip comprising a ceramic powder by making supply chimneys; firing, evacuation of the melted wax and obtaining a ceramic shell, forming a second mold, enclosing the ceramic core in position; pouring a molten metal into the shell then cooling and obtaining a metal vane enclosing the ceramic core; shell destruction; destruction of the ceramic core, using a chemical bath for example, and obtaining the raw foundry dawn.
    Thus, it is possible to define in the rough dawn of foundry surfaces of two different types. The surfaces of the first type 21 are those which have been defined, that is to say formed during the casting of the molten metal, by the surfaces of the shell. Conversely, the surfaces of the second type 22 are those which have been defined, that is to say formed during the casting of the molten metal, by the surfaces of the core. Thus, in particular, the surfaces of the internal walls 11 separating the cavities 10 from the blade 1 are surfaces of the second type 22.
    A positioning reference system according to the present description will now be presented with reference to FIG 4 which represents the blade part 3 of the rough foundry blade.
    The blade part 3 comprises a leading edge 31, a trailing edge 32, a suction face wall 33 and a pressure face wall 34. It extends between the platform 4 is a blade head 35 comprising a recess 36 commonly known as a "bathtub". The lower surface wall 34 has a notched rear part 34a in the form of a comb, formed using the core during the foundry, and revealing the internal surface 33i of the upper surface wall 33 near the trailing edge 32.
    In this figure, the surfaces of the first type are shown in white while the surfaces of the second type are shown with a texture with small dots.
    The positioning reference system comprises six points P1-P6 all located on surfaces of the second type.
    The first three points P1-P3 are located on the internal surface 33i of the upper surface wall 33. The first point PI is located within the bath 36, substantially in the middle of the latter in the front-rear direction X, defined by the chord of the blade 1, and near the upper edge of the upper surface 33. A device wedging member can easily access and position it by entering the bath 36 from the top from dawn 1.
    The second point P2 is located in the upper and rear corner of the internal surface 33i of the upper surface wall 33, near the blade head 35 and the trailing edge 32. It is accessible via the bath 36 from the top of the blade 1 or else from its lower surface through the indented part 34a of the lower wall 34.
    The third point P3 is located in the lower and rear corner of the internal surface 33i of the upper surface 33, near the platform 4 and the trailing edge 32. It is accessible from the lower surface through the indented part 34a of the lower surface wall 34.
    The surfaces on which these points PlP3 are positioned are locally planar and are oriented so that their normal directions are substantially collinear with the intradosextrados direction Y of the vane 1, orthogonal to the front-rear direction X. In addition , given their position on the internal face 33i of the upper surface wall 33, no machining of these surfaces is necessary.
    The fourth point P4 is located at the bottom of a notch 34e formed in the upper edge of the lower surface wall 34, near the leading edge 31. Thanks to this notch 34e, formed using a portion of the core during the foundry, the blade head 35 can be machined without this affecting the position of the fourth point P4, the bottom of the notch 34e remaining untouched.
    The fifth point P5 is also located at the bottom of a notch 34f formed in the upper edge of the lower surface wall 34, at the upper and rear angle of the latter. Thanks to this notch 34f, formed using a portion of the core during the foundry, the fifth point P5 is preserved even when the blade head 35 is machined.
    The surfaces on which these points P4 and P5 are positioned are also locally plane and are oriented so that their normal directions are substantially collinear with the low-high direction Z of the blade 1, orthogonal to the front-rear directions X and intrados-extrados Y. These two points P4 and P5 are therefore easily and directly accessible from the top of dawn 1.
    The sixth point P6 is located on the rear edge of the pressure side wall 34, near the upper end of the latter, in a notched portion of the scalloped rear part 34a. Given this position, no machining affects this sixth point P6.
    The surface on which this point P6 is positioned is also locally planar and is oriented so that its normal direction is substantially collinear with the front-rear direction X of the blade 1. This point P6 is therefore easily accessible and directly from the back of dawn 1.
    With such a positioning reference, it is possible to position the blade 1 on a machining tool, for example a drilling tool, by wedging the blade 1 against six setting members of the tool d machining, the ends of which are arranged to each correspond to one of the points P1-P6 of the positioning reference frame.
    Once such a setting, the position of the drilling tool relative to the blade 1 is perfectly known, which allows for very precise drilling. For example, as shown diagrammatically in FIG 3, it is possible to make a hole 19 passing longitudinally through an internal wall 11 of the blade 1 in order to connect two separate cavities 10c and 10d while ensuring a minimum residual thickness between the hole 19 and the edge of the wall 11 preferably equal to 0.3 mm.
    Although the present invention has been described with reference to specific embodiments, it is obvious that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the revendications. In particular, individual features of the various illustrated / mentioned embodiments can be combined in additional embodiments. Therefore, the description and the drawings should be considered in an illustrative rather than restrictive sense.
    It is also obvious that all the characteristics described with reference to a method can be transposed, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a method.
    权利要求:
    Claims (10)
    [1" id="c-fr-0001]
    1. A method of positioning a hollow part obtained by foundry, in which said part (1) was obtained by a foundry process involving a mold and a sacrificial core introduced into the mold and making it possible to form at least one cavity ( 10) of said part (1), in which said part (1) comprises surfaces of a first type (21), defined during the foundry by the surfaces of the mold, and surfaces of a second type (22) , defined during the foundry by the surfaces of the core, and in which a work positioning reference frame is constructed comprising at least three points (P1-P3) belonging to surfaces of the second type (22) of the workpiece (1) .
    [2" id="c-fr-0002]
    2. Positioning method according to claim 1, wherein the positioning reference system comprises at least five points, preferably six points (P1-P5), belonging to surfaces of the second type (22) of the part (1).
    [3" id="c-fr-0003]
    3. Positioning method according to claim 1 or 2, wherein the positioning reference system does not include any point belonging to surfaces of the first type (21) of the part (1).
    [4" id="c-fr-0004]
    4. Positioning method according to any one of claims 1 to 3, wherein each point of the positioning reference frame (P1-P6) is located on a locally planar surface.
    [5" id="c-fr-0005]
    5. Positioning method according to any one of claims 1 to 4, in which all the points of the positioning reference frame (P1-P6) are located on final surfaces of the part.
    [6" id="c-fr-0006]
    6. Positioning method according to any one of claims 1 to 5, wherein the core defines a wall (11) of the part (1) of which at least two faces are surfaces of the second type (22).
    [7" id="c-fr-0007]
    7. Positioning method according to claim 6, wherein the thickness of said wall (11) is less than 1 mm, preferably less than 0.5 mm.
    [8" id="c-fr-0008]
    8. Positioning method according to any one of claims 1 to 7, in which the part is a turbomachine blade d).
    [9" id="c-fr-0009]
    9. Positioning method according to any one of claims 1 to 8, further comprising a step of placing the part (1) on a tool, said tool comprising as many wedging members as points (P1- P6) in the positioning reference frame, a setting member being positioned on each of the points (P1-P6) of the positioning reference frame for the part (1).
    [10" id="c-fr-0010]
    10. A method of machining a hollow part obtained by foundry, comprising a positioning step according to claim 9, in which said tool is a drilling tool, and a drilling step in which a hole (19) is drilled in an internal wall (11) of the part (1), at least two faces of which are surfaces of the second type (22).
    类似技术:
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    同族专利:
    公开号 | 公开日
    FR3067955B1|2019-09-06|
    US20180369969A1|2018-12-27|
    US11135686B2|2021-10-05|
    引用文献:
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    FR3060650B1|2016-12-20|2019-05-31|Airbus Operations|AIR INTAKE STRUCTURE FOR AN AIRCRAFT NACELLE|US10815800B2|2016-12-05|2020-10-27|Raytheon Technologies Corporation|Radially diffused tip flag|
    US10989056B2|2016-12-05|2021-04-27|Raytheon Technologies Corporation|Integrated squealer pocket tip and tip shelf with hybrid and tip flag core|
    CN110695631B|2019-12-08|2021-08-10|湖南凯斯机械股份有限公司|Processing technology of sewing machine head|
    法律状态:
    2018-12-28| PLSC| Search report ready|Effective date: 20181228 |
    2019-05-22| PLFP| Fee payment|Year of fee payment: 3 |
    2020-05-20| PLFP| Fee payment|Year of fee payment: 4 |
    2021-05-19| PLFP| Fee payment|Year of fee payment: 5 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1755774|2017-06-23|
    FR1755774A|FR3067955B1|2017-06-23|2017-06-23|METHOD FOR POSITIONING A HOLLOW PIECE|FR1755774A| FR3067955B1|2017-06-23|2017-06-23|METHOD FOR POSITIONING A HOLLOW PIECE|
    US16/015,916| US11135686B2|2017-06-23|2018-06-22|Method of positioning a hollow workpiece|
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