METHOD AND AN ASSEMBLY

Abstract

A method of: (i) providing a mould, comprising a mould body and a mould cavity; (ii) positioning the workpiece within the mould cavity; (iii) providing a plurality of part locator rods, each rod being located in the mould body and protruding into the mould cavity, a distal end of each rod abutting against an outer surface of the workpiece; (iv) providing a fluid, the fluid filling a void defined between an outer surface of the workpiece and an internal surface of the mould cavity; (v) cooling the mould, workpiece and fluid to below a freezing point of the fluid; (vi) removing the workpiece encapsulated in frozen fluid, from the cavity, with the rods protruding from outer surface of frozen fluid; (vii) securing the encapsulated workpiece on a machine tool; and (viii) using the protruding part locator rods to position the workpiece on the machine tool in readiness for machining operation.

Claims

1. A method of securing a workpiece for a machining operation, the method comprising the steps of: (i) providing a mould, the mould comprising a mould body and a mould cavity; (ii) positioning the workpiece within the mould cavity; (iii) providing a plurality of part locator rods, each of the part locator rods being located in the mould body and protruding into the mould cavity, a distal end of each part locator rod abutting against an outer surface of the workpiece; (iv) providing a fluid, the fluid filling a void defined between an outer surface of the workpiece and an internal surface of the mould cavity; (v) cooling the mould, workpiece and fluid to a temperature below a freezing point of the fluid; (vi) removing the workpiece encapsulated in the frozen fluid, from the cavity, with the part locator rods protruding from an outer surface of the frozen fluid; (vii) securing the encapsulated workpiece on a machine tool; and (viii) using the protruding part locator rods to position the workpiece on the machine tool in readiness for the machining operation.

2. The method as claimed in claim 1, wherein the mould cavity is sized to accommodate the workpiece with a predetermined clearance between the outer surface of the workpiece and the internal surface of the mould cavity.

3. The method as claimed in claim 1, wherein step (iii) comprises the additional subsequent step of: (iii) positioning a part locator rod in each of the orthogonal x and y directions, each part locator rod being positioned to abut the workpiece so as to locate the workpiece in the x-y plane.

4. The method as claimed in claim 1, wherein step (iii) comprises the additional subsequent step of: (iii) positioning pairs of part locator rods in each of the three orthogonal x, y, and z directions, each pair of part locator rods being positioned in an opposing arrangement to abut the workpiece so as to locate the workpiece in each of the three x, y, and z planes.

5. The method as claimed in claim 1, wherein the fluid is water.

6. The method as claimed in claim 5, wherein the fluid further comprises a mineral oil in combination with an emulsifying agent.

7. The method as claimed in claim 6, wherein the emulsifying agent is a detergent.

8. The method as claimed in claim 1, wherein step (vi) comprises the additional subsequent step of: (vi) positioning the encapsulated workpiece on a cooling fixture.

9. The method as claimed in claim 8, wherein the cooling fixture is selected from the group consisting of thermoelectric cooling devices, and induction cooling plates.

10. The method as claimed in claim 1, wherein step (vii) comprises the additional subsequent step of: (vii) cooling the machine tool.

11. The method as claimed in claim 1, wherein the mould body is formed in two or more mould body portions.

12. A mould assembly for a workpiece, the mould assembly comprising: a mould body; and a mould cavity, the mould body enclosing the mould cavity, wherein the mould body comprises a plurality of part locator rods, each of the part locator rods being located in the mould body and protruding into the mould cavity.

13. The mould assembly as claimed in claim 12, wherein the mould body is formed in two or more mould body portions.

14. The mould assembly as claimed in claim 12, wherein the mould body comprises at least two part locator rods, with a part locator rod being aligned in each of the orthogonal x and y directions to locate a workpiece positioned in the mould cavity in the x-y plane.

15. The mould assembly as claimed in claim 12, wherein the mould body comprises at least six part locator rods, with corresponding pairs of part locator rods being aligned, in an opposing arrangement, in each of the three orthogonal x, y, and z directions to locate a workpiece positioned in the mould cavity in corresponding ones of each of the three x, y, and z planes.

16. A kit of parts for securing a workpiece for a machining operation, the kit of parts comprising: a mould assembly as claimed in claim 12; and a plurality of part locator rods.

Description

DESCRIPTION OF THE DRAWINGS

[0075] There now follows a description of an embodiment of the disclosure, by way of non-limiting example, with reference being made to the accompanying drawings in which:

[0076] FIG. 1 shows a schematic sectional view of a mould assembly according to a first embodiment of the disclosure;

[0077] FIG. 2 shows a schematic sectional view of the mould assembly of FIG. 1 with the workpiece and part locator rods in position;

[0078] FIG. 3 shows a schematic sectional view of the assemblage of FIG. 2 with the further addition of the fluid;

[0079] FIG. 4 shows a schematic sectional view of a mould assembly according to a second embodiment of the disclosure;

[0080] FIG. 5 shows a schematic plan view of the encapsulated workpiece and part locator rods, as arranged by the mould assembly of FIG. 4, positioned on a cooling plate; and

[0081] FIG. 6 shows a schematic elevational view of the assemblage of FIG. 5 mounted on a machine tool.

[0082] It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

[0083] CMC materials often require machining processes such as grinding, drilling, milling or other processes in order to achieve the final shape of the workpiece. However mechanical clamping fixtures may damage the brittle ceramic matrix material. It can be difficult to precisely locate a fixture against -CMC surfaces. There can also be dimensional variability, within defined tolerance limits, between successive CMC components in their as-moulded form, which further complicates their location in a fixture. In addition conventional mechanical fixtures often restrict access to parts of the workpiece, which in turn requires the use of multiple fixtures and machining operations and so further increase cost and cycle time for the finished workpiece.

[0084] The heterogeneous and anisotropic nature of CMC materials together with their high hardness makes them susceptible to inter alia delamination, edge chipping, fibre damage, and fibre pull-out. Conventional mechanical clamping fixtures have difficulty in providing full support to all areas of CMC components to oppose the machining forces and prevent the above-mentioned defects, which is critical when the orientation of the fibre laminates and/or plies changes direction relative to the cutting direction (the feed direction).

[0085] Referring to FIGS. 1 to 3, a mould assembly according to an embodiment of the disclosure is designated generally by the reference numeral 100.

[0086] The mould assembly 100 comprises a mould body 120 and a mould cavity 130, with the mould body 120 enclosing the mould cavity 130. In this arrangement, the mould body 120 comprises a first mould body portion 127 and a second mould body portion 128, which when assembled together form the enclosed mould cavity 130. The first and second mould body portions 127,128 may be formed from metal, plastic, ceramic, or another formable material.

[0087] In another arrangement, the mould body 120 may be formed as a single piece and encloses the mould cavity 130.

[0088] The mould cavity 130 has an internal surface 122, and a filling port 126. The filling port 126 allows for fluid communication between the exterior of the mould body 120 and the mould cavity 130. The filling port 126 enables a fluid to be introduced to the mould cavity 130.

[0089] A workpiece 110 is positioned within the mould cavity 130 inside the mould body 120, as illustrated in FIG. 2. The mould cavity 130 is shaped to accommodate the workpiece 110. A predetermined clearance 132 is defined between the internal surface 122 of the mould cavity and an outer surface 112 of the workpiece 110. The predetermined clearance 132 is provided over the entire outer surface 112 of the workpiece 110. In other words, the mould cavity 130 has a similar geometrical shape to the outer surface 112 of the workpiece 110, but is larger than the workpiece by at least the predetermined clearance 132. The predetermined clearance 132 may be uniform over the entire outer surface 112 of the workpiece 110.

[0090] In an alternative arrangement, the mould cavity 130 may have a different geometrical shape to that of the outer surface 112 of the workpiece 110 in order to provide a varying predetermined clearance 132 over the outer surface outer surface 112 of the workpiece 110. As previously described, this varying predetermined clearance 132 may be provided to suit different cutting conditionsor to provide additional support for a slender workpiece 110.

[0091] In the embodiment of the disclosure, the workpiece 110 is a laminated CMC component 110. In other arrangements, the workpiece 110 may be formed from a different composite material, or may be formed from a monolithic material.

[0092] The mould body 120 further comprises a plurality of part locator rod holes 124 with each part locator rod hole 124 extending through the mould body 120 to provide a passage into the mould cavity 130. In the present arrangement, the mould body 120 comprises three part rod locator holes 124.

[0093] A part locator rod 140 is accommodated in each corresponding part locator rod hole 124. Each part locator rod 140 has a distal end 142 and a proximal end 144. Each distal end 142 is positioned within the mould cavity 130 and abuts the outer surface 112 of the workpiece 110, while each corresponding proximal end 144 protrudes from the mould body 120.

[0094] The part locator rods 140 enable the spatial position of the outer surface 112 of the workpiece 110 to be precisely determined without requiring access to the outer surface 112.

[0095] Referring to FIG. 4, a mould assembly according to a second embodiment of the disclosure is designated generally by the reference numeral 200. Features of the mould assembly 200 which correspond to those of mould assembly 100 have been given corresponding reference numerals for ease of reference.

[0096] The mould assembly 200 comprises a mould body 220 and a mould cavity 230, with the mould body 220 enclosing the mould cavity 230. In this arrangement, the mould body 220 is formed as a single part. As outlined above, the mould body 220 may be formed from metal, plastic, ceramic, or another formable material.

[0097] The mould cavity 230 has an internal surface 222, and a filling port 226. The filling port 226 allows for fluid communication between the exterior of the mould body 220 and the mould cavity 230. The filling port 226 enables a fluid to be introduced to the mould cavity 230.

[0098] A workpiece 110 is positioned within the mould cavity 230 inside the mould body 220, with the mould cavity 230 being shaped to accommodate the workpiece 110.

[0099] In the embodiment shown in the figures, the mould body 120 comprises seven part locator rod holes 224, with part locator rod holes being aligned in each of the three orthogonal x, y, and z planes, so as to locate the workpiece 110 in each of the three x, y, and z planes.

[0100] Returning to the first embodiment of the mould assembly as shown in FIGS. 1 to 3, in use the workpiece 110 is positioned within the mould cavity 230 with the part locator rods 140 inserted into corresponding ones of the part locator rod holes 224 and abutting the outer surface 112 of the workpiece 110. At this point, a void 160 is defined between the outer surface 112 of the workpiece 110 and the internal surface 222 of the mould body 220.

[0101] A volume of fluid 150 is then poured into the inlet port 126 to fill the void 160. In the present embodiment the fluid 150 is a mixture of water, and a mineral oil and emulsifier additive 154. The mineral oil provides a cooling and lubricating effect for a subsequent machining operation, while the emulsifier ensures that the mineral oil remains in suspension in the water.

[0102] In an alternative arrangement, a water based additive may be mixed with the water 150 to provide cooling and lubrication for the cutting process.

[0103] The mould assembly 100 with the enclosed workpiece 110 and fluid 150 is then frozen. The increase in volume caused by the freezing of the fluid 150 (i.e. during the change from a liquid to a frozen solid) results in compressive forces acting on the workpiece 110.

[0104] The workpiece 110 is removed from the mould body 120 with the part locator rods 140 held in the frozen fluid 150 and still abutting the outer surface 112 of the workpiece 110. The encapsulated workpiece is then placed on a cooling fixture to reduce the melting of the frozen fluid 150.

[0105] FIG. 5 illustrates an encapsulated workpiece 280 according to the second embodiment that has been positioned on a cooling fixture 152 to reduce the melting of the frozen fluid 150. In the embodiment of the disclosure the cooling fixture 152 is a Peltier plate 152.

[0106] FIG. 6 shows the encapsulated workpiece 280 and the cooling fixture 152 positioned on a machine tool 190 with each of the part locator rods 140 being located against a corresponding machine tool datum surface 192. In other words, the proximal end 144 of each part locator rod 140 is located against a corresponding machine tool datum surface 192. This ensures that with the encapsulated workpiece 280 positioned on the machine tool 190, the spatial position of the workpiece 110 can be precisely determined from the spatial position of the proximal ends 144 of the part locator rods 140.

[0107] One or more machining operations may then be carried out on the encapsulated workpiece 280 using the machine tool 190. The machining operation(s) will remove the frozen fluid 150 before cutting into the workpiece 110.

[0108] The disclosure includes methods that may be performed using the subject devices. The methods may comprise the act of providing such a suitable device. Such provision may be performed by the end user. In other words, the providing act merely requires the end user obtain, access, approach, position, set-up, activate, power-up or otherwise act to provide the requisite device in the subject method. Methods recited herein may be carried out in any order of the recited events which is logically possible, as well as in the recited order of events.

[0109] Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

[0110] The foregoing description of various aspects of the disclosure has been presented for purposes of illustration and description. Such modifications and variations that may be apparent to a person of skill in the art are included within the scope of the disclosure as defined by the accompanying claims.