Method of casting

Abstract

A method of casting a product includes the steps of: creating a finished photopolymer mold; introducing liquid into the mold; hardening the liquid; and removing the photopolymer mold. A casting mold and a method of making a casting mold, are also disclosed.

Claims

1. A method of making a photopolymer mould comprising the steps of: processing an image to adjust at least one property of at least part of the image, wherein the at least one adjusted property is selected from a group comprising: brightness, contrast, line width, colour, and opacity; using laser imaging on a photopolymer plate to create a mould from the image, said laser imaging selected to have a resolution of at least 4000 ppi (6 μm per dot); and creating said mould by varying the intensity of light hitting different areas of the photopolymer plate in order to produce varying depths of hardening; wherein the photopolymer mould obtained has a relief depth which varies over at least part of the area of the mould in accordance with the properties of the image, wherein, in the step of processing an image, the image is converted into a pattern of one or both of linework and dots, so as to produce tones and halftones on the processed image, wherein, in the step of processing an image, the variation of depth across the area of the mould is dependent on the level of tones and halftones of the processed image, wherein the depth of said halftones, a screen ruling of said halftones, and a shape of said halftones are varied so that said photopolymer mould provides different shadows within a moulded product, thereby providing changes in a tonal effect, and wherein, in the step of processing an image, the image is converted into a greyscale image and the scale is reduced by cropping one of the extremities of the scale.

2. A method according to claim 1, wherein said laser imaging is selected to have a resolution of up to 8000 ppi (3 μm per dot).

3. A method according claim 1, wherein said laser imaging is selected to have a resolution greater than 8000 ppi (3 μm per dot).

4. A method according to claim 1, wherein said halftones are recesses within said photopolymer, and wherein a resulting material is provided with the effect of tonal variations.

5. A method according to claim 1, wherein in the step of processing the image, the image has line widths, colours and opacities that are varied so that said photopolymer mould further comprises surface effects and textures.

6. A method according to claim 1 wherein in the step of processing the image, the halftone screen resolution is 120 lines per inch (2.54 centimeters).

7. A method according to claim 1, wherein in the step of varying the intensity of light hitting different areas of the photopolymer plate, the method further comprises using one of a mask and a screen comprising a variable filter.

8. A method according to claim 7, wherein in the step of varying the intensity of light hitting different areas of the photopolymer plate, the method further comprises using a second variable filter located on a side of said photopolymer mould opposite said variable filter.

9. A method according to claim 7, wherein said variable filters comprise greyscale filters.

10. A method according to claims 7, wherein said variable filters are configured to vary the level of transmittance of light therethrough to vary the depth to which the hardening occurs.

11. A method according to claim 1, wherein in the step of processing the image, the image is inverted to create a negative of the original image.

12. A method according to claim 1, wherein said photopolymer mould comprises two different designs, whereby one of said designs is located on each side of said photopolymer mould.

13. A method according to claim 1, wherein in the step of creating said mould, the method further comprises the steps of: exposing the photopolymer mould to the laser imaging from a first side; exposing the photopolymer mould to the laser imaging from a second side; washing away the un-hardened polymer; drying the photopolymer; and finishing the photopolymer; and wherein the photopolymer mould is exposed to the laser imaging through a mask on at least one side, the mask comprising a filter to permit a variable intensity to pass through the filter across its surface, thereby varying the amount of light reaching different parts of the photopolymer plate.

Description

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

(1) Once a design has been settled upon, it is processed using known techniques to generate a processed image optimised to produce a high resolution mould. During the processing, the image is converted into a pattern, which can be linework and dots of varying shapes and sizes so as to allow tone and halftones to be produced, thus producing a final image with degrees of ‘shading’ when viewed from a distance.

(2) One particular method of processing the image involves the steps of: Selecting a 2-dimensional colour image to be turned into a 3-dimensional relief pattern; Creating different surface textures and effects by varying the line widths, colours and opacities; Adjusting the input and output levels of the image histogram to alter the contrast and brightness levels of the image; Changing the image to a greyscale image; Inverting the image to produce a negative of the image; and Applying an appropriate halftone screen if the image contains tonework, for example, applying a halftone screen resolution of 120 lines per inch (2.54 centimeters).

(3) It may be preferable to adjust the output levels from the full scale to a reduced scale by cropping one or both of the extremities of the scale and recalibrating the scale thereafter. For example, the output levels may be cropped from 0-255 to 20-255, with the latter then constituting 100% of the scale. This can assist with improving the quality of the mould created from the photopolymer.

(4) Processing will depend upon the photopolymer used for a particular product. The major factors to be considered during the processing step are the wavelength of light to be used for the back and main exposures, the time for which the photopolymer is exposed to the wavelength, the shoulder angle, relief depth, line type, halftone cell shape, cell gain, halftone screen ruling (number of line and dots, or cells, per cm/inch) and screen angle. The image depth is 6.3 mm in one particular example.

(5) Once the mould has been manufactured, it is then attached to a formwork using double sided adhesive tape. A concrete mix is then prepared containing the appropriate additives in order to obtain the desired flow characteristics and properties. The mould is sprayed with a release agent to assist with the later removal of the mould from the cured and hardened product. The concrete mix is poured into the mould, ensuring that the concrete flows into all of the areas of the mould, especially the halftone cells, and that air pockets are eliminated as far as possible and practicable. The concrete is then allowed to cure over time and, when sufficiently set, it is removed from the mould.

(6) In a situation where a refractory material is used, the process is the same as outlined above substituting the refractory material for the concrete. When the product made from the refractory material has been cured and finished, it can then be used to cast glass, metal, ceramics and other ‘hot’ liquids or molten solids.

(7) The introduction of a liquid into the mould is intended to incorporate a process of filling the mould with a solid and subsequently liquefying the solid, thereby allowing it to flow in the mould; the liquid is still ‘introduced’ into the mould.

(8) Items may be placed in the photopolymer mould prior to the liquid being introduced so that the item becomes part of the finished product. It may be desirable to incorporate highly-visible or reflective portions, for example retroreflectors, or ‘cats eyes’®, in a concrete wall for use in a car park. This allows a driver to more clearly identify an exit or other directions. Alternatively, precious, or semi-precious, stones may be incorporated into the material, for example in floors, walls, cladding panels or coving, possibly for use in homes or offices.

(9) The products, especially concrete products may incorporate additives for self-cleaning, for example titanium dioxide. Alternatively, or in addition, anti-bacterial additives and/or anti-fungal additives, including mould resistance, may be incorporated into the material. Additionally, the product, especially concrete, may incorporate pigment to provide an end product having colour, or an aroma, or perfume, to provide the concrete with a scent.

(10) As examples, the cast product may be for use in architectural designs, especially for use in bars, restaurants, exhibitions, retail spaces and advertising space. For example, a company logo and/or name may be cast into the concrete that forms the walls of a building. Alternatively, concrete cladding may be produced comprising a logo and/or name.

(11) The photopolymer mould may be a negative image of the required design. Where the product is to be used to subsequently cast a further product, the photopolymer mould may be a positive of the further product and the direct product form the photopolymer mould will be a negative.

(12) Other applications of the method disclosed herein include, but are not limited to: concrete surfaces in underpasses, car-parks, bridges and ceilings; concrete products for use in architectural services, building services, graphic design, interior and exterior design, advertising and landscaping.

(13) The invention extends to the use of the method to create cast products which are subsequently printed upon in selected regions using flexography or pad printing to print specific areas with specific colours, wherein registration marks cast into the product are used to establish a datum and ensure registration of the printed image with the cast image.

(14) Numerous other variations and modifications to the illustrated construction may occur to the reader familiar with the art without taking them outside the scope of the present invention. As an example, it may be desirable to destroy the mould from the finished material rather than mechanically removing it, for example by burning or dissolving the photopolymer.

(15) Rather than being cast in the photopolymer mould, the refractory material may be applied to the mould, for example by applying a layer of the refractory material to the photopolymer mould, such that the mould can be used for casting liquids with a melting point higher than that of the photopolymer. By way of an example, the photopolymer mould may be coated with a layer of heat resistant material and subsequently used to cast liquids such as glass and metals.