GB2279026A - Method of producing a pattern - Google Patents

Method of producing a pattern Download PDF

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Publication number
GB2279026A
GB2279026A GB9312450A GB9312450A GB2279026A GB 2279026 A GB2279026 A GB 2279026A GB 9312450 A GB9312450 A GB 9312450A GB 9312450 A GB9312450 A GB 9312450A GB 2279026 A GB2279026 A GB 2279026A
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GB
United Kingdom
Prior art keywords
mould
pattern
reverse
reverse mould
rubbery
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9312450A
Other versions
GB9312450D0 (en
Inventor
Michael John Billingham
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
MICHAEL J BILLINGHAM Ltd
Original Assignee
MICHAEL J BILLINGHAM Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by MICHAEL J BILLINGHAM Ltd filed Critical MICHAEL J BILLINGHAM Ltd
Priority to GB9312450A priority Critical patent/GB2279026A/en
Publication of GB9312450D0 publication Critical patent/GB9312450D0/en
Publication of GB2279026A publication Critical patent/GB2279026A/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
    • B29C33/3842—Manufacturing moulds, e.g. shaping the mould surface by machining
    • B29C33/3857—Manufacturing moulds, e.g. shaping the mould surface by machining by making impressions of one or more parts of models, e.g. shaped articles and including possible subsequent assembly of the parts
    • B29C33/3878—Manufacturing moulds, e.g. shaping the mould surface by machining by making impressions of one or more parts of models, e.g. shaped articles and including possible subsequent assembly of the parts used as masters for making successive impressions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
    • B29C33/40—Plastics, e.g. foam or rubber
    • B29C33/405—Elastomers, e.g. rubber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C39/00—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Casting Or Compression Moulding Of Plastics Or The Like (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)

Abstract

A method of producing a pattern for use in foundry work comprises the steps of placing an original model (10a) of an item to be cast in a mould (20) and casting around the model (10a) in liquid form, rubbery material, permitting the rubbery material to solidify to produce a first reverse mould of the original model in the rubbery material, and removing the model (10a) from the first reverse mould, casting into the first reverse mould in a liquid state, resinous material and permitting the resinous material to solidify in the mould thus to produce a pattern of resinous material, and removing the pattern of resinous material from the first reverse mould, placing the pattern of resinous material in a mould and casting around the pattern liquid resin material, permitting the resin material to solidify in the mould thus to produce a second reverse mould in the resin material, and utilising the second reverse mould in resin material to produce a pattern in a rubbery material. <IMAGE>

Description

Title: Method of producing a pattern Description of Invention This invention relates to a method of producing a pattern for use in foundry work.
An object of the present invention is to provide a method of producing a pattern for use in foundry work to a higher standard than has hithertofore been produced.
According to one aspect of the invention we provide a method of producing a pattern for use in foundry work comprising the steps of placing an original model of an item to be cast in a mould and casting around the model in liquid form, rubbery material (as herein defined), permitting the rubbery material to solidify to produce a first reverse mould of the original model in the rubbery material, and removing the model from the first reverse mould, casting into the first reverse mould in a liquid state, resinous material and permitting the resinous material to solidify in the mould thus to produce a pattern of resinous material, and removing the pattern of resinous material from the first reverse mould, placing the pattern of resinous material in a mould and casting around the pattern liquid resin material, permitting the resin material to solidify in the mould thus to produce a second reverse mould in the resin material, and utilising the second reverse mould in resin material to produce a pattern in a rubbery material.
It has been found that by utilising the method of the first aspect of the invention, patterns of rubbery material can be made from an original model which do not deviate substantially from the original model, at least in part because shrinkage which naturally occurs when a liquid solidifies in a casting process, can carefully be controlled.
By "rubbery material" we mean any natural or synthetic rubber material or any substitute therefor, which, when solid, exhibits rubber like qualities of elasticity and resilience.
By virtue of the resilience of the rubbery material, a model of complex configuration, and a corresponding pattern of resinous material can be separated from the first reverse mould.
Preferably the rubbery material is cast into the mould around the original model in a molten state and is permitted to solidify upon cooling. In one example, the original model is placed into a mould nest made primarily of aluminium or a suitable aluminium alloy, in which the original model is supported, the mould nest being shaped to provide a moulding cavity around the original model into which the rubbery material is cast.
The resinous material which is cast into the first reverse mould of rubbery material, may comprise a mixture of resin with suitable hardener, and a rubbery material such that the resultant pattern of resinous material exhibits some resilience over and above any resilience a pattern made merely of resin could exhibit.
Thus removal of the pattern of resinous material from the first reverse mould of rubbery material is facilitated, and more importantly, removal of the pattern of resinous material from the second reverse mould of resin material, (by which we mean resin and a suitable hardener), is facilitated. Thus the risk of damaging any fragile parts of the second reverse mould is minimised.
If desired, prior to the resinous material being cast into the interior of the first reverse mould of rubbery material, a mandrel may be inserted to add rigidity to the rubber mould. The mandrel may for example be made of aluminium or another metal for example, or any other suitably rigid material.
To facilitate filling of the first reverse mould of rubbery material, the interior of the first reverse mould may be subjected to vacuum during casting of the resinous material therein.
Conveniently, when the original model is removed from the first reverse mould, the first reverse mould is kept in the mould nest, where provided, so as to be supported by the mould nest during casting of the resinous material.
Because of the exothermic nature of resin as it solidifies, to avoid any risk of damage to the pattern of resinous material as it solidifies, the temperature of the first reverse mould during casting of the resinous material therein is preferably controlled to maintain the temperature within predetermined limits.
Thus the rate of solidification of the resinous material in the first reverse mould may be controlled.
In one arrangement, the first reverse mould in the mould nest where appropriate, may be located within a cooled container such as a refrigerator during casting, and maintained therein until the resinous material has at least partially solidified.
The mould into which the pattern of resinous material is placed and into which resin material is cast, may again be the aluminium mould nest into which the original model was placed and around which rubbery material was cast, and which supported the first reverse mould during casting of the resinous material.
During casting of the resin material around the pattern of resinous material, the temperature of the mould may again be controlled to maintain the temperature within predetermined limits, again to obviate any risk of damage due to shrinkage.
The second reverse mould of resin may be utilised to produce a pattern of rubbery material, by for example, casting rubbery material into the second reverse mould of resin material whilst in a liquid e.g. molten state, and permitting the rubbery material to solidify to produce the pattern of the original model, in a rubbery material. Preferably, the second reverse mould is kept in the mould nest when the pattern of resinous material is removed, and the rubber pattern, or rubber patterns, are provided by casting liquid rubbery material into the second reverse mould while the second reverse mould is held and supported by the mould nest.
According to a second aspect of the invention we provide a method of casting an item in metal comprising utilising a rubber pattern produced by a method according to the first aspect of the invention to produce a mould, removing the pattern from the mould, and casting into the mould, molten material.
The invention will now be described with reference to the accompanying drawings in which: FIGURE 1 is a perspective illustrative view of a cold end compressor being an item produced by casting utilising a pattern made by a method in accordance with the invention.
FIGURE 2 is an illustrative side sectional view of a mould nest for use in performing the invention.
Referring to figure 1 of the drawings, there is shown a casting produced in a foundry, comprising a cold end compressor being a component in a turbo charger for use with an internal combustion engine.
It can be seen that the casting 10 is of a complex configuration comprising a disc like base 11, a central shaft 12, and a plurality of fins 13 which are configured such that when the component is in situ, and the component 10 is rotating about an axis A of the shaft 12, the desired compressor air flow characteristic is achieved.
The casting 10 is produced by a casting technique utilising a pattern made of a rubbery material around which moulding material such as plaster, is provided. The pattern is substantially identical to the final casting 10.
By virtue of the pattern being made of a rubbery material, even though this is of a complex shape, the pattern can be removed from the moulding material, once the moulding material has set, due to the elastic and resilient nature of the rubbery material.
The pattern of rubbery material is a replica of an original model of the component 10, which may for example, be made in metal by machining or another technique which is too costly for mass production purposes.
Present practice is to produce a first reverse mould of rubber around an original model of a component and to cast into the first reverse mould, a white metal to produce a white metal pattern. It has been found that particularly with components of a complex configuration such as cold end compressor 10, the effect of the white metal pattern on the first reverse mould can result in a pattern of white metal which is not a good copy of the original model.
The white metal patterns are used for producing a second reverse mould of resin in which rubbery material is cast for producing the pattern of rubbery material.
The resin second reverse mould once cast around the white metal pattern, is subjected to heat and acid in order to remove the white metal pattern.
Hence the white metal pattern is lost and cannot be reused and also, such heat and acid can damage the resin mould surface resulting in poor surface finish on the patterns of rubbery material subsequently produced in the second reverse mould.
Referring now also to figure 2, in accordance with the invention, the original model indicated at 10a is placed in a mould nest 20 made for example of aluminium or an aluminium alloy. The mould nest 20 supports the model 10a and is shaped to provide a moulding cavity 21 around model 10a. Rubbery material, such as a silicon rubber, is cast into the cavity 21 around the original model 10a. For example, the rubbery material may be introduced into the moulding cavity 21 in a molten state and permitted to set. Thus a first reverse mould of rubbery material is produced. By virtue of the resilient and elastic nature of the rubbery material, the original model 10a can subsequently readily be removed from the first reverse mould without any substantial risk of damage to the first reverse mould, the mould nest 20 being separable along a joint line indicated at 22 to facilitate this.
The first reverse mould is then used to produce a pattern of resinous material which corresponds to the original model. Preferably, the first reverse mould of rubbery material is kept in the mould nest 20 during production of the pattern of resinous material.
If necessary, a mandrel, for example of aluminium or another metal in-indeed any other suitably rigid material, may be placed in the mould nest 20, within the interior of the first reverse mould to add rigidity to the pattern of resinous material. This is facilitated by the mould nest 20 having a channel 23 to permit the mandrel to be inserted and supported in the nest 20.
Resinous material is then introduced into the first reverse mould in a liquid state, and permitted to solidify.
The resinous material preferably comprises a mixture of rubbery material e.g. silicon rubber, and resin and hardener such as a urethane resin, although an epoxy resin or another type of resin such as polyester resin could be used.
To produce a pattern of resinous material which exhibits some resilience over and above the resilience which would be exhibited by a pattern made solely of resin material and is suitable for any particular circumstance,a careful selection is made of the proportion of rubbery material relative to the proportions of resin and hardener. The kinds of materials used, are also carefully chosen. This may need to be done empirically for each casting, although with experience an alorithym may be developed.
Due to the exothermic nature of resin/hardener material as it solidifies, the entire first reverse mould (in the mould nest 20) is preferably subjected to cooling during casting and at least up until partial solidification of the resinous material. For example, the entire mould nest 20 may be placed in a cool box such as a refrigerator, or otherwise subjected to cooling.
Because the resinous material may be of a thick constituency and not readily flow into the intricate parts of the first reverse mould, e.g. the parts which produce the fins 13 of the compressor, if desired the interior of the first reverse mould may be subjected to vacuum by any conventionally known technique, to facilitate filling of the mould, and in particular, to ensure that resinous material is drawn into the extremities of the first reverse mould produced by the fins 13 of the original model 10a which are particularly thin.
As mentioned above, the resultant pattern of resinous material will exhibit some resilience. This coupled with the nature of the rubbery material of the first reverse mould, enables the pattern of resinous material to be removed from the first reverse mould without any serious risk of damage either to the first reverse mould or to the pattern of resinous material. Hence the first reverse mould may be re-usable.
The pattern of resinous material is then used to make a second reverse mould of resin material.
Conveniently, the first reverse mould is removed from the nest 20 and the pattern of resinous material is supported in the nest 20, like the original model, with there being a moulding cavity 21 around the pattern. Resin material, which may be epoxy resin or polyester resin and hardener or another suitable kind of resin, is then cast into the cavity 21 around the pattern of resinous material to produce a second reverse mould of resin material. Again, the temperature may be controlled during casting and up until the resin material has at least partially solidified, so as to obviate any risk of damage either to the pattern of resinous material, or to the resultant second reverse mould of resin material, due to shrinkage of the resin material as it is cast.
When the resin material has set, a second reverse mould of resin material is thus produced which may subsequently be used as a mould into which molten rubber e.g. silicon rubber, may be poured and permitted to set, so as to produce a pattern of rubbery material which corresponds very closely indeed to the original model of the component 10.
Preferably, the pattern of resinous material is removed from the mould nest 20, but the second reverse mould is kept in the nest 20, during subsequent production of one or more rubbery patterns.
Although the invention has been described with reference to casting a cold end compressor component 10, the method of the invention could of course be performed to produce a rubber pattern of any other item which it is desired to cast.
The surface finish achieved in the final components 10 by utilising a pattern of a rubbery material is good, and it has been found that the rubber patterns produced by the method described above have a longer life than patterns presently produced for use in casting such components.
Because the quality of the resultant pattern of rubbery material is so good, any machining work necessary on the final casting can be reduced to a minimum.
If desired, the second reverse mould of resin material may be subjected to some finishing/machining process prior to use for producing patterns of rubbery material. The second reverse mould is anticipated to have an extremely long life and be extremely hard wearing. The resinous material of the pattern is highly compatable with the resin material of the second reverse mould.
The exact conditions of cooling of the resinous material in the first reverse mould or of the resin material around the pattern of resinous material, is obtained empirically and through experience, such as to enable consistently high quality patterns of rubbery material to be produced. The proportion of resin and hardener to rubbery material which is cast into the first reverse mould, and the amount of hardener provided, all have to be developed according to the nature of the item finally to be cast.
Although in the example described above, all the various casting steps are carried out utilising the same mould nest 20, of course any or each of the casting steps may be carried out using different moulding apparatus.
The features disclosed in the foregoing description, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (20)

1. A method of producing a pattern for use in foundry work comprising the steps of placing an original model of an item to be cast in a mould and casting around the model in liquid form, rubbery material, permitting the rubbery material to solidify to produce a first reverse mould of the original model in the rubbery material, and removing the model from the first reverse mould, casting into the first reverse mould in a liquid state, resinous material and permitting the resinous material to solidify in the mould thus to produce a pattern of resinous material, and removing the pattern of resinous material from the first reverse mould, placing the pattern of resinous material in a mould and casting around the pattern liquid resin material, permitting the resin material to solidify in the mould thus to produce a second reverse mould in the resin material, and utilising the second reverse mould in resin material to produce a pattern in a rubbery material.
2. A method according to claim 1 wherein the rubbery material is cast into the mould around the original model in a molten state and is permitted to solidify upon cooling.
3. A method according to claim 1 or claim 2 wherein the original model is placed into a mould comprising a mould nest in which the original model is supported, the mould nest being shaped to provide a moulding cavity around the original model into whcih the rubbery material is cast.
4. A method according to claim 3 wherein the mould nest is made primarily of aluminium or a suitable aluminium alloy.
5. A method according to any one of claims 1 to 4 wherein the resinous material which is cast into the first reverse mould of rubbery material comprises a mixture of resin with suitable hardener, and a rubbery material such that the resultant pattern of resinous material exhibits some resilience over and above any resilience a pattern made merely of resin could exhibit.
6. A method according to any one of claims 1 to 5 wherein prior to the resinous material being cast into the interior of the first reverse mould of rubbery material, a mandrel made of a suitably rigid material is inserted to add rigidity to the rubber mould.
7. A method according to claim 6 wherein the mandrel is made of metal such as aluminium.
8. A method according to any one of the preceding claims wherein to facilitate filling of the first reverse mould of rubbery material, the interior of the first reverse mould is subjected to vacuum during casting of the resinous material therein.
9. A method according to any one of the preceding claims wherein when the original model is removed from the first reverse mould, the first reverse mould is kept in the mould, so as to be supported by the mould during casting of the resinous material.
10. A method according to any one of the preceding claims wherein the temperature of the first reverse mould during casting of the resinous material therein is controlled to maintain the temperature within predetermined limits so as to control the rate of solidification of the resinous material in the first reverse mould.
11. A method according to any one of claims 1 to 10 wherein the first reverse mould in the mould is located within a cooled container during casting, and maintained therein until the resinous material has at least partially solidified.
12. A method according to claim 11 wherein the cooled container is a refrigerator.
13. A method according to any one of claims 1 to 12 wherein the mould into which the pattern of resinous material is placed and into which liquid resin material is cast, is the mould into which the original model was placed and around which rubbery material was cast.
14. A method according to any one of the preceding claims wherein during casting of the resin material around the pattern of resinous material, the temperature of the mould is controlled to maintain the temperature within predetermined limits.
15. A method according to any one of the preceding claims wherein the second reverse mould of resin is utilised to produce a pattern of rubbery material by casting rubbery material into the second reverse mould of resin material whilst in a liquid state, and the rubbery material is permitted to solidify to produce a pattern of the original model, in the rubbery material.
16. A method according to claim 15 wherein the second reverse mould is kept in the mould when the pattern of resinous material is removed, and the rubber pattern, or rubber patterns, is or are provided by casting liquid rubbery material into the second reverse mould while the second reverse mould is held and supported by the mould.
17. A method of producing a pattern substantially as hereinbefore described with reference to the accompanying drawings.
18. A method of casting an item in metal comprising utilising a rubber pattern produced by a method according to any one of claims 1 to 17 to produce a mould, removing the pattern from the mould, and casting into the mould, molten metal.
19. A method of casting substantially as hereinbefore described with reference to the accompanying drawings.
20. Any novel feature or novel combination of features as herein defined and/or shown in the accompanying drawings.
GB9312450A 1993-06-16 1993-06-16 Method of producing a pattern Withdrawn GB2279026A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9312450A GB2279026A (en) 1993-06-16 1993-06-16 Method of producing a pattern

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9312450A GB2279026A (en) 1993-06-16 1993-06-16 Method of producing a pattern

Publications (2)

Publication Number Publication Date
GB9312450D0 GB9312450D0 (en) 1993-07-28
GB2279026A true GB2279026A (en) 1994-12-21

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GB9312450A Withdrawn GB2279026A (en) 1993-06-16 1993-06-16 Method of producing a pattern

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8702394B2 (en) 2001-06-06 2014-04-22 Borgwarner, Inc. Turbocharger including cast titanium compressor wheel
CN105834357A (en) * 2016-04-07 2016-08-10 山东理工大学 Rapid manufacturing method for resin casting die

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0060731A2 (en) * 1981-03-17 1982-09-22 Kabushiki Kaisha Komatsu Seisakusho Pattern for producing a mould and method for manufacture of such a pattern

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0060731A2 (en) * 1981-03-17 1982-09-22 Kabushiki Kaisha Komatsu Seisakusho Pattern for producing a mould and method for manufacture of such a pattern

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8702394B2 (en) 2001-06-06 2014-04-22 Borgwarner, Inc. Turbocharger including cast titanium compressor wheel
CN105834357A (en) * 2016-04-07 2016-08-10 山东理工大学 Rapid manufacturing method for resin casting die

Also Published As

Publication number Publication date
GB9312450D0 (en) 1993-07-28

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