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Shell Mouldingsa New Foundry Technique

Shell Mouldingsa New Foundry Technique CASTINGS Shell Mouldings-a New Foundry Technique A Brief Account of Developments in the Production of Castings Since the Introduction of Synthetic Materials the resulting chill effect on thin sections is much H E process known as Shell Moulding is the most important of a number of less. Tchanges which have been brought about All normal casting alloys can be used with by the introduction of plastics into foundry this process, although the extent of the ad­ technique. These changes result from the use of vantages varies with different materials. The thermo-setting resins in foundry sand to bind Solar Aircraft Company, San Diego 12, it, and depend on the temperature properties of California, is one firm that has adopted the the resin, which enable it to be cured at a process for the production of small com­ moderate temperature so as rigidly to bind the ponents cast from a wide range of stainless mould, while the temperature of the melt is steels. high enough to break down the resin again so A further advantage for repetition casting is that the mould falls away after the casting has the possibility of mechanizing the production been poured. of shell moulds. This has been achieved by The idea of a shell mould is very simple. A Messrs Polygram Casting Co, Ltd., who have metal mould is heated to a temperature high produced a machine for the quantity production of moulds. In this machine the pattern is sprayed enough to cure the resin, and is brought into with a stripping agent, then introduced into a contact with the resin-sand mixture. A layer of bin of the sand-resin mixture, and inverted to the mixture is thus cured to form a thin rigid remove the surplus mixture. The shell is then mould around the pattern, and the pattern is cured in the oven and finally ejected from the removed from the sand with the shell mould pattern. The machine will carry out this cycle adhering to it. The mould can then be more thoroughly cured in an oven and separated from once in two minutes, in which time four half- the pattern. The technique in practice has moulds can be produced. required considerable development, particularly Resin-sand mixtures are used in other ways as to the means of separating mould and in the foundry, notably in core production. The pattern. Much of this work has been done by properties of the resin can be selected to suit the Messrs Polygram Casting Co, Ltd., Power characteristics and the melting point of the Road, Gunnersbury, London W.4, who hold metal to be cast and a variety of resins for these patent rights over some parts of the process. purposes are manufactured by Imperial Chemical Industries Ltd, Plastics Division, The advantages of the process over traditional Welwyn, and by Bakelite Ltd, 12-18 Grosvenor foundry methods, particularly for small repeti­ Gardens, London, S.W.I. tion casting work, are numerous. Shell moulds are light and easily transported and stored. The resin is quickly burnt out after pouring and the sand readily falls away from the casting. The use of a metal pattern and the nature of the mould give a very accurate casting, with a good finish. The simplicity of the equipment and the reduction in the weight of moulds reduce the foundry overheads. Unskilled labour can be used and working conditions improved. The metal comes into contact with a much smaller quantity of sand than in the normal mould and TRADE REVIEWS Normalair 1952 [Normalair Ltd., Yeovil, Somerset] In this brochure a general description of a cabin atmosphere control system is given, followed by a detailed description of each of the components of the system. These descriptions arc illustrated by de­ tailed sectional drawings and schematic diagrams and provide a clear picture of the operation and con­ struction of these now quite complex components. At the end there is a corresponding section on the oxygen system, with particulars of the pressure demand regulator around which it is designed. The publication is well produced and gives a useful account of pressurizing systems, which have had to develop so rapidly in recent years. Plastics The Properties of I.C.I. Plastics [I.C.I. Plastics Division, Gloucester House, 149 Park Lane, London, W.l] These two publications cover much the same ground in different ways. The first is a lavishly illustrated brochure describing the principal plastics produced by the company, giving examples of their use, to­ gether with a full list of their physical, mechanical, electrical and chemical properties and methods of handling and manufacture. The second publication also lists the various materials with a discussion of properties, and the applications for which they render them suitable. May 1953 151 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aircraft Engineering and Aerospace Technology Emerald Publishing

Shell Mouldingsa New Foundry Technique

Aircraft Engineering and Aerospace Technology , Volume 25 (5): 1 – May 1, 1953

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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0002-2667
DOI
10.1108/eb032293
Publisher site
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Abstract

CASTINGS Shell Mouldings-a New Foundry Technique A Brief Account of Developments in the Production of Castings Since the Introduction of Synthetic Materials the resulting chill effect on thin sections is much H E process known as Shell Moulding is the most important of a number of less. Tchanges which have been brought about All normal casting alloys can be used with by the introduction of plastics into foundry this process, although the extent of the ad­ technique. These changes result from the use of vantages varies with different materials. The thermo-setting resins in foundry sand to bind Solar Aircraft Company, San Diego 12, it, and depend on the temperature properties of California, is one firm that has adopted the the resin, which enable it to be cured at a process for the production of small com­ moderate temperature so as rigidly to bind the ponents cast from a wide range of stainless mould, while the temperature of the melt is steels. high enough to break down the resin again so A further advantage for repetition casting is that the mould falls away after the casting has the possibility of mechanizing the production been poured. of shell moulds. This has been achieved by The idea of a shell mould is very simple. A Messrs Polygram Casting Co, Ltd., who have metal mould is heated to a temperature high produced a machine for the quantity production of moulds. In this machine the pattern is sprayed enough to cure the resin, and is brought into with a stripping agent, then introduced into a contact with the resin-sand mixture. A layer of bin of the sand-resin mixture, and inverted to the mixture is thus cured to form a thin rigid remove the surplus mixture. The shell is then mould around the pattern, and the pattern is cured in the oven and finally ejected from the removed from the sand with the shell mould pattern. The machine will carry out this cycle adhering to it. The mould can then be more thoroughly cured in an oven and separated from once in two minutes, in which time four half- the pattern. The technique in practice has moulds can be produced. required considerable development, particularly Resin-sand mixtures are used in other ways as to the means of separating mould and in the foundry, notably in core production. The pattern. Much of this work has been done by properties of the resin can be selected to suit the Messrs Polygram Casting Co, Ltd., Power characteristics and the melting point of the Road, Gunnersbury, London W.4, who hold metal to be cast and a variety of resins for these patent rights over some parts of the process. purposes are manufactured by Imperial Chemical Industries Ltd, Plastics Division, The advantages of the process over traditional Welwyn, and by Bakelite Ltd, 12-18 Grosvenor foundry methods, particularly for small repeti­ Gardens, London, S.W.I. tion casting work, are numerous. Shell moulds are light and easily transported and stored. The resin is quickly burnt out after pouring and the sand readily falls away from the casting. The use of a metal pattern and the nature of the mould give a very accurate casting, with a good finish. The simplicity of the equipment and the reduction in the weight of moulds reduce the foundry overheads. Unskilled labour can be used and working conditions improved. The metal comes into contact with a much smaller quantity of sand than in the normal mould and TRADE REVIEWS Normalair 1952 [Normalair Ltd., Yeovil, Somerset] In this brochure a general description of a cabin atmosphere control system is given, followed by a detailed description of each of the components of the system. These descriptions arc illustrated by de­ tailed sectional drawings and schematic diagrams and provide a clear picture of the operation and con­ struction of these now quite complex components. At the end there is a corresponding section on the oxygen system, with particulars of the pressure demand regulator around which it is designed. The publication is well produced and gives a useful account of pressurizing systems, which have had to develop so rapidly in recent years. Plastics The Properties of I.C.I. Plastics [I.C.I. Plastics Division, Gloucester House, 149 Park Lane, London, W.l] These two publications cover much the same ground in different ways. The first is a lavishly illustrated brochure describing the principal plastics produced by the company, giving examples of their use, to­ gether with a full list of their physical, mechanical, electrical and chemical properties and methods of handling and manufacture. The second publication also lists the various materials with a discussion of properties, and the applications for which they render them suitable. May 1953 151

Journal

Aircraft Engineering and Aerospace TechnologyEmerald Publishing

Published: May 1, 1953

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