LOST WAX MOULDING MANUFACTURING PROCESS

Abstract

A method for making a wax model for the manufacture of a part, the part including at least one cavity, the method including: arranging at least two core elements made of a ceramic material into a wax mold, the core elements having at least partially a shape complementary to the cavity of the part to be manufactured, and injecting wax into the wax mold, around the core elements, so as to form the wax model, the two core elements being assembled prior to the injection of wax by at least one staple, the staple including a central portion from which two branches extend, each branch being fitted into an orifice formed in one of the core elements.

Claims

1-7. (canceled)

8. A method for making a wax model for manufacturing a part, said part comprising a cavity, the method comprising the steps of: arranging at least two core elements made of a ceramic material in a wax mold, said two core elements having, at least partially, a shape complementary to the cavity of the part to be manufactured; assembling the two core elements together by a staple, wherein the staple includes a central portion from which two branches extend, each branch of the two branches being fitted into a respective orifice formed in a respective one of the two core elements, and wherein the orifice of at least one of the two core elements is an open-through orifice, the branch of the two branches of the staple passing through said open-through orifice having a free end folded over the core element that has the open-through orifice so as to maintain the staple in position; and injecting wax into the wax mold, around the assembled two core elements, so as to form the wax model.

9. The method according to claim 8, wherein at least one of the two branches of the staple is held in the respective orifice by glue.

10. The method according to claim 8, wherein the central portion and the two branches of the staple have a circular cross-section.

11. The method according to claim 8, wherein the two core elements have a respective first lateral surface, both first lateral surfaces facing a same side, and wherein the staple is placed so that the central branch is against said first lateral surfaces of the two core elements.

12. The method according to claim 11, wherein the two branches have respective distal portions that are folded over second lateral surfaces of the core elements opposite to the first lateral surfaces, the two branches of the staple being folded over said second lateral surfaces along two opposite directions.

13. The method according to claim 8, wherein the part is a turbine vane.

14. A method for manufacturing a part having at least one cavity, the method comprising the steps of: making a wax model by: arranging at least two core elements made of a ceramic material in a wax mold, said two core elements having, at least partially, a shape complementary to the cavity of the part to be manufactured; assembling the two core elements together by a staple, wherein the staple includes a central portion from which two branches extend, each branch of the two branches being fitted into a respective orifice formed in a respective one of the two core elements, and wherein the orifice of at least one of the two core elements is an open-through orifice, the branch of the two branches of the staple passing through said open-through orifice having a free end folded over the core element that has the open-through orifice so as to maintain the staple in position; and injecting wax into the wax mold, around the assembled two core elements, so as to form the wax model, forming a shell mold made of a ceramic material from the wax model; eliminating the wax model; and casting a molten metallic material into the shell mold.

15. The method according to claim 14, wherein the part is a vane of a rotating turbine.

16. The method according to claim 14, wherein the part is a turbine stator vane.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0034] FIG. 1, described above, shows a schematic view of a wax mould for making a wax model.

[0035] FIGS. 2a and 2b are schematic perspective views of two core elements each intended to form a corresponding cavity in a vane to be manufactured.

[0036] FIG. 3 shows a first step of assembling the core elements of FIG. 2.

[0037] FIG. 4 shows a second step of assembling the core elements of FIG. 2.

[0038] FIG. 5 shows a schematic perspective view of a staple connecting the core elements of FIG. 2.

[0039] FIG. 6 shows a schematic sectional view of a staple connecting the core elements of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0040] Referring to FIGS. 2 to 6, a wax model for manufacturing a vane is obtained by injecting wax into the wax mould 10. Prior to the wax injection, core elements 102 and 104 are arranged in the wax mould 10 in lieu of the core elements 13. The core elements 102 and 104 are made of a ceramic material. An outer face 106 of the core 102 defines the leading edge of the vane to be made. A portion 108 of the core 104 defines the trailing edge of the vane to be made.

[0041] FIGS. 3 and 4 show steps of assembling the core elements 102 and 104 before positioning them in the wax mould 10.

[0042] First, the core elements 102 and 104 are positioned with respect to each other using an axial or longitudinal stop 110 and two first spacers 112. The stop 110 allows aligning the core elements 102 and 104 in an axial or longitudinal direction. The first spacers 112 allow keeping a distance between the core 102 and the core 104 in a direction perpendicular to the longitudinal direction. This distance between the core elements 102 and 104 allows forming a wall between two cavities in the vane, after making the wax model and casting a molten metallic material into a shell mould made from the wax model.

[0043] It is essential to prevent the core elements from moving relative to one another during the injection of wax into the wax mould or during casting of the molten metallic material into the shell mould, so that the manufactured vane meets the dimensional specifications.

[0044] For this purpose, one or more staple(s) 114 is/are configured to hold the core elements 102 and 104 relative to each other. Each staple 114 comprises a central portion 116, two branches 118 extending perpendicular to the central portion 116, from each of the ends of said central portion 116. The branches 118 of the staples 114 are fitted into the orifices 120 of the core 102 and into the orifices 122 of the core 104.

[0045] The staple 114 may be held in the orifices 120 and 122 by a bonding step, for example by means of a suitable glue or wax.

[0046] The staple is made of platinum or of any other material adapted to be melted during casting of the metallic material.

[0047] Once the core elements 102 and 104 are held together using the staples, the spacers 112 are removed and the core elements 102 and 104 are positioned in the wax mould 10.

[0048] In another embodiment, the core members 102 and 104 are positioned with respect to each other without the use of spacers 112. In this case, the core elements 102 and 104 held together are arranged directly in the wax mould 10.

[0049] The orifices 120 or 122 may be blind orifices.

[0050] The orifices 120 or 122 may consist of open-through orifices as shown in FIG. 6. In this case, the ends of the branches 118 may be folded over a surface 103 of the core 102, respectively a surface 105 of the core 104, opposite to the central portion 116. In this manner, bonding the staple 114 is no longer necessary to hold the staple 114 in position.