GB2515773A

GB2515773A - An improved casting system

Info

Publication number: GB2515773A
Application number: GB1311889.8A
Authority: GB
Inventors: Kevin Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-07-03
Filing date: 2013-07-03
Publication date: 2015-01-07
Also published as: GB201311889D0

Abstract

A method of making a conduit and/or a mould suitable for use in a casting process that uses an additive layer manufacturing process (ALM). The conduit and/or mould can be made directly using the ALM process or an ALM process can be used to make a model which is then coated, with the model then being removed. The method can be used to make a conduit or a mould with a flow influencing structure in the form of a baffle, filter, spiral, gate, protrusion, perforated plate or a taper. The conduit can be branched and used as a runner, sprue, ingate or a riser in the casting process. The conduit and/or mould can be made from sand or a plastics material.

Description

An Improved Casting System

Field of the Invention

This invention relates to a casting system, especially for use in casting metals.

Background to the Invention

Current casting methods utilise computational fluid dynamics to calculate the most appropriate flow rates for casting systems. However, the casting is undertaken using runners that have a rectangular, or square, cross-section. Such runners are restricted in that they create a conduit with limited ability to control the flow and turbulence of the casting fluid passing there through. Therefore, even where the flow rates have been calculated to ensure the best possible final product, the use of rectangular sectioned runners limits the result because the flow cannot be reliably controlled.

Additionally, the turbulence created in the runners can lead to further loss of control of the fluid, thereby resulting in the final cast product being of a poor quality.

It is difficult to install any devices or shapedstructurs to modify the flow of the fluid iii casting conduits without introducing further parts. The joins associated with connecting those parts can create further turbulence and weak spots in the conduit.

Furthermore, traditional casting processes use a two-part mould cavity -a cope and a drag -to create cast products. Such a two-part system results in a split line' where the cope and drag are connected, which can be unsightly. Additionally, the connection between the cope and drag is a weak point in the system and may be affected by high-pressure casting liquid entering the cavity. In extreme circumstances, this can separate the two-part mould cavity and ruin the casting process. The split line is normally positioned parallel to the flow line.

Summary of the Invention

Accordingly, the present invention is directed to a method of making a casting conduit or mould intended for use in a casting process, wherein the process comprises the step of creating the conduit or mould using an additive process. The use of an additive process in creating a conduit or mould allows for the integration of shapes and structures that would not be possible using traditional methods.

Advantageously, the shape for the structure is provided by a CAD file, which is used to direct the additive process. The use of a computer aided design file (CAD file), allows one to create the conduit or mould to allow smooth of the casting liquid. The CAD file and be linked to analysis software to produce a conduit that has the flow rates and pressures necessary for a successful casting.

It is preferable that the additive process is selected from a group comprising: Fused deposition modelling (FDM); Fused Filament Fabrication (FFF); Melted and Extrusion Modelling (MEM); Direct metal laser sintering (DMLS); Electron beam melting (EBM); Selective heat sintering (SETS); Selective laser sintering (SLS); Powder bed and inkjet head 3d printing, Plaster-based 3D printing (PP); Laminated object manufacturing (LOM); Stereolithography (SLA); and Digital Light Processing (DLP). Furthermore, it is especially preferably, the conduit is constructed from sand, wax or plastics material. Other additive processes and other materials may be used, which would lead one skilled in the art to the same end result. Metals and metal alloys, such as aluminium and titanium alloys, may be used in th additive manufacturing of the conduit. Alternatively, it may be desirable to use plastics materials, such as PMMA and H1)PE.

It is advantageous that the stnicture is coated with a refractory material. Coating the structure in a refractory material allows for the conduit or mould to be used with hot casting liquids, such as metals, without significant damage being inflicted on the structure.

Preferably, the structure is coated with a secondary material and the original material used in the additive process is substantially removed from the within the conduit or mould structure. By creating a skeleton structure the conduit or mould may be coated and provided with further beneficial properties. This is especially useful where the additive process uses a low-melting point material.

The invention is also directed to a casting conduit or mould comprising an inlet in fluid communication with an outlet and connected by the conduit body, wherein the conduit body is provided with at least one internal structure that affects the flow of fluid therethrough. Providing an internal structure that affects the flow of fluid therethrough allows a conduit to be created that changes the flow rate and/or pressure of the fluid passing through it. By introducing one or more internal structure chosen from.a group comprising: a baffle; a filter; a spiral; a gate; a protrusion; a perforated plate; and a taper, allows one to create obstacles that change the flow rate of the fluid.

This adjustment of the flow rate can allow the speed of the casting liquid entering the moulding cavity to be set to a predetermined and desirable level that creates a more predictable fmal cast product. A baffle can be used to slow the flow, as can a filter, whilst a converging or diverging taper can adjust the pressure of the casting fluid and/or the rate of flow. Because these features can be created in the internal structure during the additive process, a conduit one can create a conduit with a flow rate suited to the product being cast. Traditional processes lack the ability to control the flow rate accurately and repeatedly through the length of the conduit. However, the present invention allows for various adjustments that would be impossible using traditional means by creating a single, integral structure. Vortices and backflow can be reduced by creating a conduit in accordance with the present invention.

Preferably, the conduit or mould has a substantially circular cross-section. The use of a circular cross-section reduces turbulence through the conduit, especially around corners. Other shaped cross-sections may be desirable, for example, hexagonal or elliptical.

It is advantageous that the structure comprises sand, wax or plastics material. The use of an additive process allows one to create a conduit and/or mould from various materials that may be heat-resistant or lost', or destroyed, in the casting process, depending upon the requirement. Such materials can be shaped relatively quicldy using an additive process and are relatively cheap compared to traditional materials.

It is preferable that the conduit is provided with a plurality of branches. The use of a plurality of branches allows one to ifirther control the flow rate through the conduit.

Additionally, the conduit can be used to feed a mould cavity at multiple entry points and to provide different flow characteristics at different entry points in the mould cavity. Furthermore, by creating various branches that subsequently recombine, the temperature of the casting liquid can be cooled, which may be desirable in some casting processes.

Advantageously, the internal passage through the conduit is tapered along at least part of its length. The use of tapering along at least part of the length of the conduit allows for a change of pressure (and speed of flow) within the conduit. The tapering may be convergent or divergent according to the requirements. The temperature of the casting liquid may also be adjusted by the use of tapered sections. Additionally, heat exchange apparatus may be positioned in close proximity to assist with the temperature regulation of the casting liquid.

The branch system also allows one to introduce additives or furthers casting liquids into the conduit downstream by creating partitioned parallel structure that merges with the first.

It is particularly advantageous that the conduit or mould of the present invention is created using the method disclosed herein.

The invention may relate to a casting conduit selected from a group comprising: a runner; feeder; a spite; an ingate; and a riser.

The present invention removes the need to connect various parts together and so reduces the join lines between parts. Additionally, the conduit may be used to cast at least part of the final product itself and, unlike traditional methods, join lines can be avoided as the conduit can be formed as a single structure.

The device may comprise a trap, such as a U-bend, S-bend, J-bend, and other shaped structures that aid in reducing the risk of oxidation of the casting fluid. 4.

The conduit and mould may be incorporated into casting systems.

The use of the additive process in making the conduit and mould allows for substantially identical copies of the conduit to be reproduced. Therefore, where a plurality of substantially identical parts are required to perform the same task, the additive process can be used to create them.

The mould and the conduit may be one-piece, in which case the conduit is both a conduit and a mould. In such a form, the flow rate of the casting liquid can be controlled not only in reaching the mould cavity but also upon entry and within the cavity. Where the cavity comprises an integral one-piece structure, the risk of the casting liquid damaging the cavity due to its pressure is reduced. This is ftirther reduced when the mould and/or conduit comprise integral structures to control the flow rate.

An advantage of the present invention is that the split line is removed from the mould, thereby allowing any orientation of the mould. The material entering the mould is controlled and with the reduced need for multiple moulds to make a single structure and the reduced need for a split line, there pressures within the mould are reduced. As a result of allowing for variations on the orientation of the cast product, multiple castings can be undertaken iii a single process by using more than one mould cavity in single process. This can be achieved by adjusting the orientation of the moulds to fit more into the same space than traditional processes allow for. The runner system and ingates do not need to remain in the parting plane, nor does the cavity need to remain parallel to the part line, which means that the cavity can be at any angle to aid filling with casting liquid.

The conduit and/or mould may be part of a system rather than the whole system.

It may be desirable to create a two-part mould using the method of the present invention. Parts created by the additive process may be used as the pattern (male part) and the mould (female part), or the cope and drag.

S As an example, when casting a cube structure, using the present invention, the cube can be cast with a corner at the lower-most position rather than a flat face being in the lower-most position. This results in the ability to potentially cast three cubes using the present invention in the height taken up by two cubes under traditional techniques because they can be tessellated together.

Claims

Claims I. A method of making a casting conduit or mould intended for use in a casting process, wherein the process comprises the step of creating the conduit using an additive process.
2. A method according to claim 1, wherein the shape for the structure is provided by a CAD file, which is used to direct the additive process.
3. A method of making a casting conduit or mould according to claim I or claim 2, wherein the additive process is selected from a group comprising: Fused deposition modelling (FDM); Fused Filament Fabrication (FFF); Melted and Extrusion Modelling (MEM); Direct metal laser sintering (DMLS); Electron beam melting (EBM); Selective heat sintering (SHS); Selective laser sintering (SLS); Powder bed and inkjet head 3d printing, Plaster-based 3D printing (PP); Laminated object manufacturing (LOM); Stereolithography (SLA); and Digital Light Processing (DLP).
4. A method of making a casting conduit or mould according to any preceding claim, wherein the conduit is constructed from sand or plastics material.
5. A method of making a casting conduit or mould according to claim 5, wherein the structure is coated with a refractory material.
6. A method of making a casting or mould conduit according to claim 4, wherein the structure is coated with a secondary material aria the original material used in the additive process is substantially removed from the within the conduit structure.
7. A casting conduit comprising an inlet in fluid communication with an outlet and connected by the conduit body, wherein the conduit body is provided with at least one internal structure that affects the flow of fluid therethrough.
8. A casting conduit according to claim 7, wherein the internal structure is a structure chosen from a group comprising: a baffle; a filter; a spiral; a gate; a protrusion; a perforated plate; and a taper.
9. A casting conduit according to claim 7 or claim 8, wherein the conduit has a substantially circular cross-section.
10. A casting conduit according to any one of claims 7 to 9, wherein the conduit comprises sand or plastics material.
11. A casting conduit according to any one of claims 7 to 10, wherein the conduit is provided with a plurality of branches.
12. A casting conduit according to any one of claims 7 to 11, wherein the internal passage through the conduit is tapered along at least part of its length.
13. A casting conduit according to any one of claims 7 to 12 made by the method of claims ito 6.
14. A casting conduit according to any preceding claim, wherein the conduit is selected from a group comprising: a runner; a sprue; an ingate; and a riser.
15. A casting mould made using an additive process and comprising an inlet and a mould cavity, wherein a flow-control structure is incorporated into the mould, wherein the flow-control structure is a structure chosen from a group comprising: a baffle; a filter; a spiral; a gate; a protrusion; a perforated plate; and a taper.
16. A casting mould according to claim 15, wherein the mould comprises sand or plastics material.
17. A casting mould according to claim 15 or claim 16 made by the method of claims ito 6.
18. An integral casting conduit and casting mould made by the method of claim 1.
19. A casting conduit and/or mould or a method of making a casting conduit and/or mould substantially as described herein with any appropriate combination of the text and/or drawings.