GB2241452A - Tooling for squeeze casting - Google Patents

Abstract

A toolset suitable for use in the production of low volume/prototype squeeze-formed articles comprises co-operating mould elements (10 and 14) formed of concrete. A portion of each said mould element bounds a mould cavity and has a respective external metal liner (22 and 34) and includes respective internal heating and/or cooling passages (24 and 38). <IMAGE>

Description

TOOLING This invention relates to tooling of the type used to provide a mould cavity for the reception of liquid metal in a press used in a squeeze-forming operation.

Such tooling may be utilised for the production of various components of varying degrees of shape complexity by the squeeze-forming of for example an aluminium or magnesium alloy.

The term "squeeze-forming" as used throughout this specification and claims will be understood to refer to a forming operation wherein liquid metal is introduced to a first part of a mould, the mould is closed under pressure so that the liquid metal is displaced by the mould closure to fill a cavity within the mould without entrapping air, the metal is maintained under pressure whilst solidification takes place so as to ensure that any shrinkage cavities which may form are closed and filled, and the mould is subsequently opened and the formed article removed.

Conventional tooling used in a squeeze-forming process has been formed of die steel machined to define the shape of the required mould cavity and also to provide a plurality of heating and/or cooling passages within the steel adjacent the surface of the cavity. The provision of passages adjacent the mould cavity surface for cooling purposes is essential to the rapid heat extraction required from the molten metal during its squeeze-forming. However, the production of such tooling is expensive; for example, a toolset for a vehicle wheel could cost of the order of 60,000 and, even for extremely low volume prototype requirements, it has nevertheless been necessary to utilise such expensive toolsets.

It is an object of ;the present invention to provide a new or improved form of toolset for use in a squeeze-forming process which toolset will offer substantial cost advantages in comparison with convention die steel tool sets but which will nevertheless be satisfactory in use for low volume applications.

In accordance with the invention there is provided a tool set for use in a forming press for the production of articles by squeeze-forming comprising at least two co-operating mould elements closable together to provide a mould cavity therebetween, at least one of said mould elements comprising a concrete body having a mould cavity forming portion thereof externally covered with a metal liner, and a plurality of heating and/or cooling passages embedded in the concrete body adjacent said liner.

Such a toolset conveniently comprises a female mould element within which a male mould element is receivable to provide a said mould cavity therebetween wherein each of said male and female mould elements comprises a concrete body having a mould cavity forming portion thereof externally covered with a metal liner and a plurality of heating and/or cooling passages embedded in the concrete body of each mould element adjacent each respective said liner.

Said plurality of heating and/or cooling passages conveniently comprises a hollow coil embedded in said concrete body and having inlet and outlet ends extending externally of said body for connection to respective heating or cooling fluids.

Other features of the invention will become apparent from the following description given herein solely by way of example with reference to the accompanying drawing which shows a vertical crosssectional view through a tool set constructed in accordance with the invention.

Referring to the drawing, there is shown a toolset for use in a press for the production of articles by squeeze-forming. In this embodiment the toolset comprises a lower female mould element 10 mounted on a lower stationary part 12 of the press and an upper male mould element 14 mounted on an upper vertically reciprocable part 16 of the press.

Each of said male and female mould elements 14 and 10 is constructed in accordance with the invention and comprises a concrete body having a mould cavity forming portion thereof externally covered with a metal e.g.

steel liner; a plurality of heating and/or cooling passages being embedded in the concrete body adjacent said liner.

In the embodiment illustrated, the lower female mould element 10 may be of circular or rectilinear plan form and is mounted on the lower stationary part 12 of the press. Such female mould element 10 comprises a metal exterior frame 18 and a central mould cavity 20, the interior surface of which is provided by a metal liner 22. The heating and/or cooling passages comprise a hollow coil 24 surrounding and being located closely adjacent the inner surface of the metal liner 22 with respective inlet and outlet ends 26-28 for connection to heating or cooling fluids extending out of the metal frame 18.The mould element has a concrete body 30 filling substantially the whole of the volume between the metal frame 18 and the cavity liner 22, the concrete being poured in situ into a pre-assembly of frame, liner and coil whereby the coil. 24 becomes embedded in the concrete adjacent the liner 22.

Prior to the forming of the concrete body 30, appropriate guides are located within the void to be filled with concrete to provide, in the solidified concrete body, passageways for ejector rods 32 extending upwardly from the stationary part 12 of the press. In known manner, movement of an ejector support plate 33 upwards by activation of the press hydraulic ejection system causes the ejector rods 32 to enter the mould cavity 20 through corresponding apertures in the metal liner 22 and eject the formed article from the cavity.

The upper male mould element 14 is formed in a similar manner to that of the female element 10. As illustrated, the upper mould element comprises a punch having a central downwardly projecting spigot and a cylindrical body which, when the two mould elements are closed together engages within the upper part of the cavity 20 provided in the female mould element 10. The exterior surface of the punch is covered with a metal liner 34 containing a concrete body 36 having a hollow coil 38 for heating and/or cooling fluids embedded therein. Respective inlet and outlet ends 40-42 for connection to heating or cooling fluids extend out of the concrete body 36 from the coil 38.

A tool set produced in accordance with the invention is extremely cost beneficial in comparison with a conventional die steel tool set although it will not have the life of a conventional die steel tool set and is not intended for large volume production use. It is however quite satisfactory for use for example in low volume prototype applications where its low cost, being of the order of one twelfth of that of a conventional die steel toolset, is of considerable significance. It is found that the metal liners defining the mould cavity configuration retain their shape and integrity for a limited low volume utilisation.

The tool set constructed in accordance with the invention can offer a squeeze-forming process advantage over the use of a conventional die steel tool set in that the cooling passages can be located in the concrete body extremely closely adjacent the metal liner to the mould cavity thereby resulting in extremely efficient and rapid heat extraction from the molten metal. Conversely, the cooling passages in a conventional die steel tool set have to be drilled through the mould body at a distance spaced from the mould cavity surface to provide a thickness of metal between the cavity surface and the cooling passages of sufficient strength to withstand the process conditions. Such spacing of the cooling passages from the cavity surface is of course contrary to the requirement to maximise the rate of heat extraction from the molten metal in the cavity.

Claims (4)

1. A toolset for use in a forming press for the production of articles by squeeze-forming comprising at least two co-operating mould elements closable together to provide a mould cavity therebetween, at least one of said mould elements comprising a concrete body having a mould cavity forming portion thereof externally covered with a metal liner, and a plurality of heating and/or cooling passages embedded in the concrete body adjacent said liner.

2. A toolset as claimed in Claim 1 comprising a female mould element within which a male mould element is receivable to provide a said mould cavity therebetween wherein each of said male and female mould elements comprises a concrete body having a mould cavity forming portion thereof externally covered with a metal liner and a plurality of heating and/or cooling passages embedded in the concrete body of each mould element adjacent each respective said liner.

3. A toolset as claimed in either one of Claims 1 or 2 wherein said plurality of heating and/or cooling passages comprises a hollow coil embedded in said concrete body and having inlet and outlet ends extending externally of said body for connection to respective heating or cooling fluids.

4. A toolset constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.