WO1991015330A1

WO1991015330A1 - Moulding means and method

Info

Publication number: WO1991015330A1
Application number: PCT/AU1991/000126
Authority: WO
Inventors: Karl Martin De Porteous
Original assignee: Karl Martin De Porteous
Priority date: 1990-04-06
Filing date: 1991-04-05
Publication date: 1991-10-17

Abstract

A means and method for production of moulding dies comprises steps of constructing a plurality of metal dies, by firstly creating a master figure, creating a chiller die from that master figure to have a rigid casing, producing at least one elastomeric pattern from the chiller die to have a shape and size corresponding to the master, and creating the plurality of metal dies from that pattern or those patterns, by a process which includes metal spraying, and, in some instances, electroplating.

Description

MOULDING MEANS AND METHOD

This invention relates to a method for production of dies for moulding, articles under production conditions, and discloses relevant means for that method.

FIELD OF THE INVENTION

This invention is one of a series of related inventions which are the result of research into the methods of producing soft toys, garment display mannequins and other products which incorporate elasto eric and polymeric techniques. Other inventions are disclosed in the following patent specifications: Australian Patent Application PCT/AU90/00388 "Moulding Method";

Australian Patent Application PJ 9390 "Hinge"; Australian Patent Application PI 6282 (29303/89) "Model Construction"; and corresponding applications in other countries.

BACKGROUND OF THE INVENTION

The Australian Patent Application PCT/AU90/00388, referred to a moulding method, and was particularly applicable to the moulding of toys, for example dolls, wherein a skin was first formed of latex or other polymeric material to avoid the difficulty encountered with cleaning of flash or seam distortions on the product, and in that invention a former was produced which comprised a flexible wall capable of expanding or collapsing upon increase or decrease of fluid pressure, the method included coating a former with elastomer, allowing the elastomer to cure or coagulate over the former, collapsing the former by decrease of fluid pressure within it, removing the elastomeric skin thus being formed over the former when in its collapsed state, and subsequently injecting a foamable material within the skin while the skin was held within a die.

A number of difficulties are .encountered in production moulding, particularly when high production is required, in that it is necessary to have a number of "cloned" dies for moulding because of the extended cycle time to have a foam form and cure sufficiently to remove a product from a mould. One of the objects therefore of this invention is to provide a method whereby a number of metal dies can be produced without incurring the very high expense which is presently associated with the production of dies. In particular, the invention is directed to a method whereby faithful reproductions can be assured, and the dies are suitable for the moulding of the shape of production articles, for example dolls, and wherein the shape is faithfully reproduced, even if different dies are used.

BRIEF SUMMARY OF THE INVENTION

In one aspect, this invention comprises steps of constructing a plurality of metal dies, by firstly creating a master figure, creating a chiller die from that master figure to have a rigid casing, producing at least one elastomeric pattern from the chiller die to have a shape and size corresponding to the master, and creating the plurality of metal dies from that pattern or those patterns, by a process which includes metal spraying, and, in some instances, electroplating.

Even though use may be made of a skin by the method described in our aforesaid Application AU90/00388, it is still desirable that the shapes of the metal dies should be faithful reproductions of the master figure and should so match one another so that there is a minimum possibility of "flash" or "pinching" of the skin occurring.

To achieve this, in one embodiment the invention includes the steps of forming metal dies by a metal spraying or electroplating process (or both) over elastomeric patterns, the elastomeric patterns being cradled in die portions which are separated by a part-line in a plane which does not necessarily pass through the widest part of the pattern, the patterns nevertheless being removable because of their elastomeric nature. Having one relatively large and one relatively small portion of the metal coated dies, the relatively small portion can be regarded as a "lid" and expansion of foaming material for example is less likely to enter any space between the dies which might exist, so as to cause flash if for example the dies are used in a step which includes foaming over an articulated model. More importantly, by shifting the part line above the halfway mark eliminates operator error and ensures that the skin on the pre-moulded part does not get pinched between the die face at any point when the two die parts are brought together.

More specifically, the invention consists of creating a master figure, producing a chiller die by forming at least two rigid shells surrounding but spaced from the master figure, interposing mouldable material between the shells and the master figure, separating the shells and removing the master figure, thereby producing the chiller die comprising said at least two rigid shells and mouldable material defining a female mould of shape complementary to the master figure shape, producing a plurality of patterns from the chiller die to each have a shape and size corresponding to the master figure, and producing each of a plurality of metal dies from respective said patterns by partly embedding the master figure in mouldable frangible material but leaving portion of the master figure exposed, forming a female mould part over said exposed portion, breaking and removing the mouldable frangible material from the master figure, replacing the master figure by a said pattern and supporting that pattern by said mould part and metal spraying over an exposed portion of said pattern and said mould part to form a first metal die part, removing said mould part, and metal spraying over the remaining portion of said pattern to form a second metal die ,part, complementary to the first.

A number of other difficulties which have been encountered, and solutions to overcome those difficulties, are described hereunder with reference to and are illustrated in the accompanying sketches in which:-

Fig. 1 shows a series of seven steps in the formation of a chiller die,

Fig. 2 shows a series of five steps in the formation of an elastomeric male pattern from the chiller die, and

Fig. 3 shows a series of five steps in the formation of metal dies from the elastomeric pattern.

A large number of steps will be seen to lie within the preferred embodiment described hereunder, but many of those steps are simple and quickly achieved. The cost of multiple metal dies having faithfully reproduced surface shapes is very much less than the cost of any other process known to the Applicant.

Referring first to Fig. 1, stage A illustrates diagrammatically the stage of creating a master figure 10 utilising a plastic carving material.

in stage B, the master figure 10 has a release film 11 applied to it, and is then evenly covered with potter's clay 12, and a part-line flange 13 is established to provide a flange surface 14 which lies in a generally central plane P- P. In stage C, release film and fibreglass reinforced plastic is overlaid over the upper portion of the clay 12 and part- line surface 14 on the upper side of the flange 13 and

allowed to cure to form a shell 15. In stage D, the product is inverted, the clay part-line flange 13 is removed, release film is applied over the now upper surfaces of the outstanding flanges 14 of fibreglass reinforced plastics and over flanges 14 and the now upper part of the clay 12, further fibreglass reinforced plastics then overlies the release film to cover the clay at 18 and also form further flanges 19, is allowed to cure to form a shell 17, and subsequently locating holes are drilled in the flanges 14 and 19, for receiving fasteners. At least two shells are required.

In stage E of Fig. 1, before the flanges are fastened together, the upper fibreglass reinforced plastic 17 is lifted away, all the potter's clay is removed, and the bottom half of the resulting void is replaced with modelling clay 21 up to flange 14. The upper plastic shell 17 is replaced, the flanges are bolted together, and a liquid elastomer 22 (for example εilicone rubber) is poured into the top half void. The master figure 10 is supported on the freshly applied modelling clay 21, in the bottom half of the mould, during this operation.

In stage F of Fig. 1, the assembly is again inverted, the upper plastic shell 17 lifted away, modelling clay 21 is removed and discarded, the upper plastic shell 17 replaced, and the other void is similarly filled with a liquid elastomeric mould forming material. Adhesion is prevented in the usual way by application of a release agent, before replacement of the upper plastic shell 17.

Stage G of Fig. 1 illustrates the separation of the two parts of the "chiller die" 23 thus formed, and when so separated the master figure 10 can be removed. Jackets 24a and 24b surround respective parts of the chiller die 23, and are fitted with water inlet and outlet fittings to provide for flow of hot or cold water as required.

SUBSTITUTESHEET Reference is now made to Fig. 2 of the accompanying sketches:-

In stage A of Fig. 2, the chiller die 23 is reassembled, heated by passing warm water through water jackets 24a and 24b, and a small quantity of molten wax 25 is placed in the chiller die which is then cooled with cold water and rotated until the wax freezes. By this means, a soluble wax figure 27 is cast, it being desirable however to utilise a wax which has a relatively small coefficient of expansion upon heating, so that upon cooling very little of the volume is lost. Such a wax is available under the registered Trade Mark SOLUCARV. By using a small amount of wax, the freezing takes a relatively short time, and by utilising the chiller die made as in Fig. 1, the heat capacity of the die is reduced, so that the die expansion and the wax expansion through heating is simultaneously reversed upon cooling, the difference in dimension therefore only being the difference in temperature and coefficient of expansion. With this arrangement, it is possible to get a consistently good quality hollow wax shell 27. It is to be noted that a chiller die having a high mass which cools very slowly will not provide such a faithful reproduction of shape.

As shown in stage B of Fig. 2, the thin wall wax hollow figure is removed from the chiller die, and is subject to a minimum of rework, to improve "Flash" and correct other imperfections. Rework is mostly required on the part-line developed between the two halves of the chiller die.

The next stage illustrated as stage C in Fig. 3 is to first spray the outer surface of the hollow wax figure with a plastic skin 28 (for example, as sold under the trade mark "SOLMASK"), and then with a high quality gypsum plaster or plaster of Paris 29 (slurry of hemihydrate of calcium sulphate) . The plaster 29 slightly expands upon setting, thus

SUBSTITUTESHEET offsetting the differential contraction between the wax and the chiller die when the wax freez.es.

The hollow figure 27 is then filled with hot water as shown diagrammatically in stage D of Fig. 2, the water dissolving the wax, leaving behind the film 28 and a plaster mould 30.

Warm water is added to soften the plastic film 28 which had been previously sprayed over the wax figure in stage C so that the release film can be removed from the female plaster mould 30, leaving a cavity with the female shape. It should be noted that with this process, the reproduction of shape on the female plaster mould is very faithful and only minor error if any will be found to exist. Further, there is no seam within the plaster mould.

Finally in stage E of Fig. 2, the plaster mould 30 is filled with a settable elastomer which will set to form an elastomeric male pattern 31 which takes the shape of the interior surface of the plaster mould 30, and after it has set the plaster mould 30 is merely broken away from it and discarded.

At this stage of the specification it should be noted that the process referred to heretofore is suitable for applications other than the manufacture of soft toys, mannequins or the like.

The process can for example be used for investment casting of metal in the plaster mould, which is free of any contamination such as wax which can otherwise melt and permeate the casting. It can also, for example, be used for prosthesis. Furthermore, the costs involved are very low and the process of Fig. 2 is very simple so that many elastomeric male patterns can be produced by this process. This is of considerable importance when large numbers of metal dies are required for production moulding purposes.

SU The production of metal dies then follows from the foregoing, and is illustrated in Fig. 3. Initially the master figure 10 created, in Fig. 1A of the drawings is again used and in Fig. 3A is partially embedded in such mouldable frangible material as modelling clay 33 to a depth which exceeds the maximum width so that there is an "undercut" in the modelling clay. The outer surface of the modelling clay provided with a part-line surface 34 which need not be planar but can follow for example the contour of the body of a doll, and release agent 35 is applied over the part-line surface of the modelling clay and the relatively small exposed surface of the master figure 10. Fibreglass reinforced plastic 36 is then overlaid over the release agent on the part-line surface 34 and the exposed surface of the master figure 10, and the plastic is formed with upstanding flanges 37, and back-filled at 38 for example with epoxy resin and aluminium powder and granules to form a female mould 39. The modelling clay 33 is then broken away from the master figure 10 and discarded.

In stage B of Fig. 3 there is illustrated the inversion of the fibreglass reinforced plastics female mould 39, and the recess in that female mould in being rigid will constrain the flexible elastomeric male pattern 31 to be retained in both shape and position, that elastomeric male pattern 31 replacing the rigid master figure 10. In order to achieve a sharp edge between the contoured surface and the part-line, a small amount of flexible but hard-setting putty 40 is applied around the edge. Upon setting of the putty, the male pattern 31 is removed, the part-line trimmed and the male pattern 31 is then replaced (Stage C) . At this stage it is possible to achieve almost zero clearance between the male pattern 31 and the FRP female mould 39, and release agent, then metal 42, is then sprayed in stage C of Fig. 3 over the upper surface of the FRP female mould 39 and the exposed surface of the elastomeric male pattern 31. When a very smooth finish is required, graphite can first be applied to the surfaces to be sprayed, and electroplated to form a film. The metal utilised

SUBSTITUTE SHEET can vary considerably but in this embodiment can be initially nickel over the face of the elastomeric pattern 31 and FRP of mould 39, or alternatively, over an electroplated film. Nickel bond wire can then be sprayed, followed by a zinc alloy and finally by zinc. This creates a larger mould part 43.

In stage D, the larger metal mould part 43 created in stage C is inverted, has release agent applied thereto, is boxed up and back-filled at 46 with a suitable material such as epoxy resin and aluminium powder and granules, and in many instances water galleries are included, and a smaller metal mould part 47 is produced in the same way.

In stage E of Fig. 3, the smaller mould part 47 created by metal spraying as illustrated in stage D is boxed up as previously, the two die parts are separated and, in being elastomeric, the male pattern is readily removed from the larger mould part 43.

Many advantages are achieved with this invention. Die flash or pinching of skin is reduced to a minimum because of the "lid effect" of the smaller die part. Operator error is almost eliminated.

Because the flexible models are placed into a cavity formed from the original die pattern, they are constrained to their proper shape for formation of the metal dies (stages B and C of Fig. 3), and the production of metal dies is simplified and expedited. No machining is necessary.

The use of the plaster shells to produce the elastomeric male pattern in Fig. 2 provides a blemish-free female shape which faithfully follows the original master figure, and the process is so quick and simple that it can be used to produce many male patterns in a day by a single operator. The use of

SUBSTITUTE SHEET the chiller die, associated with small quantities only of wax, enables very rapid production of the hollow wax figures.

By utilising a part-line between the die halves, which is located not centrally but away from the area of maximum width (stages A, B and C of Fig. 3), the smaller die part functions more as a "lid" when moulding takes place and the possibility of development of flash between the die parts is substantially reduced.

There are however alternative methods of producing metal dies, which vary from the method of Fig. 3. The second method described hereunder is related to the aforementioned PCT Patent Application AU90/00388. The first stage is to produce a chiller die as shown in Fig. 1, and the hollow wax figure is reproduced from a chiller die as in stages A and B of Fig. 2. As described in the said Patent Application, the wax is graphite coated excepting for a saw cut which is transverse to the length of the hollow wax figure and which divides the wax figure into two parts. For example in the case of doll production, the saw cut would be across the torso of the doll.

To compensate for the thickness of the saw cut, a rigid clear plastic disc is located between the two halves and forms a skirt. The two halves are then electroplated in accordance with prior art, the skirt has location holes drilled therein to locate the two halves together, and formers are produced as described in the aforesaid specification.

Other variations of the invention described in our former specification, or obvious equivalents to those described herein, will be seen to be within this invention.

SUBSTITUTESHEET

Claims

The claims defining the invention are as follows:

1. A method for the production of moulding dies comprising:

(a) creating a master figure,

(b) producing a chiller die by: forming at least two rigid shells surrounding but spaced from the master figure, interposing mouldable material between the shells and the master figure, separating the shells and removing the master figure, thereby producing the chiller die comprising said at least two rigid shells and mouldable material defining a female mould of shape complementary to the master figure shape,

(c) producing a plurality of patterns from the chiller die to each have a shape and size corresponding to the master figure; and

(d) producing each of a plurality of metal dies from respective said patterns by: partly embedding the master figure in mouldable frangible material but leaving portion of the master figure exposed, forming a female mould part over said exposed portion, breaking and removing the mouldable frangible material from the master figure, replacing the master figure by a said pattern and supporting that pattern by said mould part, and metal spraying over an exposed portion of said pattern and said mould part to form a first metal die part, removing said mould part, and metal spraying over the remaining portion of said pattern to form a second metal die part, complementary to the first.

2. A method for the production of moulding dies according to claim 1 wherein each said pattern comprises elastomeric material.

3. A method according to claim 1 wherein said forming of at least two rigid shells comprises applying a release film over said master figure, surrounding said master figure with mouldable material, establishing an outstanding part- line flange of that said mouldable material, applying a release film and then fibre reinforced resin over one face of said flange and part of said surrounding mouldable material to form a first of said shells, removing said flange after setting of said resin and applying further release film and fibre reinforced plastics material over one face of the set resin at the locality of the flange to form a second of said shells, removing said surrounding mouldable material from between said shells, and replacing with fluent settable elastomer.

4. A method according to claim 3 further comprising separating flanges of said shells, and removing said mouldable material from between one only of said shells and said master figure, reassembling said flanges, inserting said fluent settable elastomer into the void vacated by said mouldable material, allowing said elastomer to set, and repeating said separation of flanges, removal of remaining said mouldable material, reassembly of said flanges, and insertion of fluent settable elastomer.

5. A method according to claim 1 further comprising creating water jackets around respective said shells.

6. A method according to claim 3 wherein said production of each of said patterns comprises forming a wax figure within said shells when assembled, removing said wax figure from said shells applying a release film over said wax figure, a layer of frangible mouldable material over said release film, removing said wax from the frangible material when set, filling the void of the frangible material when wax-free with fluent settable elastomer, and breaking and discarding the frangible material from the elastomer when set.

7. A method according to claim 1 wherein said formation of a female mould part in the production of metal dies comprises applying a release agent and fibre reinforced plastic over said exposed portion of the master figure, and back-filling the fibre reinforced plastic.

8. A method according to claim 1 wherein said metal spraying comprises spraying firstly with nickel and subsequently with a metal which comprises mostly zinc.

9. A method according to claim 8 further comprising electroplating surfaces of the die parts before metal spraying.

10. A method according to claim 2 wherein said female mould part extends over a minor portion of said master figure and said first metal die part extends over a major portion of said elastomeric pattern.

11. A method substantially as hereinbefore described with reference to and as illustrated in the accompanying representations.