CASTING
casting
Mould Making

MOULD MAKING : CENTRIFUGAL CASTING : HAND CASTING : JEWELLERY : BROOCHES : PENDANTS : THONGS : EAR RINGS : CUFF LINKS : TIE PINS : TRANSPORT MODELS : TRAINS : CARS : FARM VEHICLES : FIGURES : DETAILING PARTS : MILITARY MODELS : TOY SOLDIERS : MODEL SOLDIERS : MILITARY VEHICLES : TANKS : AIRCARFT : SCI-FI FIGURES : FANTASY FIGURES : WAR GAMING FIGURES : BADGES : SPORTS TROPHIES : MEDALS : REPLICA COINS : SMALL ENGINEERING PARTS : THIMBLES : CANDLE STICKS : MINIATURES

Mould Making

It comes as quite a surprise to most people to learn that pewter and other tin alloys can be cast successfully into rubber moulds (without the mould melting or catching on fire!). Two sorts of rubber can be used RTV silicone rubbers are cold curing, they come in a liquid form and are hardened by addition of a catalyst. Vulcanised rubber moulds (both organic and silicon based varieties are available) are cured by heat and pressure and are the first choice of the industry. They have been commonly used for casting pewter and other tin alloys for more than 50 years.

RTV silicone rubber moulds
Advantages
Disadvantages
  • No special equipment required
  • Can be used for items that may be fragile
  • You can choose exactly where the mould parts will divide
  • Higher Cost
  • Take longer to make
  • Reduced life with molten metals
  • Generally soft easily distorted (most effect on centrifugal casting and larger objects)

Vulcanised rubber moulds
Advantages
Disadvantages

  • Reasonable Cost
  • Usually quick and easy to make
  • Very good mould life
  • Rubbers are stiff enough to resist too much distortion while soft enough to remove items with undercuts
  • Expensive special equipment needed for mould making.
  • Risk of damage to fragile masters.
  • More difficult to control where the mould parts will divide
Siilcone or Organic vulcanised rubber?

Vulcanised rubber is available in organic and silicon the finished product can be essentially the same but there are some distinct differences in use.

Silicone
Advantages
Disadvantages

  • putty like consistency easy to work with, however can be difficult to do certain tasks.
  • Usually quick and easy to make
  • Very good mould life, tolerance to temperatures well above organic rubbers making these suitable for lead and higher melting alloys
  • low temperature and pressure varieties enable moulds to be made from low melting or fragile materials.
  • silver and copper alloy masters don't interfere with vulcanising process
  • Higher cost
  • ingenuity can be required to create complex moulds.
  • generally poorer heat absorption for a given flexibilty, can be a problem for bulkier pewter items
  • sensitive to organic contamintaion, masters and your hands need to be thoroughly clean
Organic

  • laminated sheets can aid control of parting lines and making complex moulds
  • Low cost
  • good mould life, good heat absorption for a given flexibilty
  • working with laminations can be slow and requires skil for complex mouldsl
  • not suitable to cast higher temperature metals like lead
  • silver and copper alloys need to be sprayed with a suitable barrier to avoid problems with the sulfur present in the raw rubber

 

We make moulds for customers who also take advantage of our Contract Casting Service

We only make vulcanised moulds usually organic or low temperature silicon. To make a mould we need a master, this could be made from pewter or many other metals or epoxy putty (such as Milliput) or a combination of these. We can offer advice on the suitability of a particular material. Normally for machine casting a master mould is made containing numerous different ietms, this is used to make multiples of each from which a production moulds can be made containing numerous examples of the same design. In this way the casting conditions can be matched to suit the particular object. Sometimes making a separate mould for each can't be justified and so items which have similar bulk etc. are placed in the same mould.


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