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Vacuum Casting

The silicone mould is one of the prototype casting methods. It has advantages of short time, little cost, small probability of processing failure and so on. It is able to manufacture more than 20 same products with just one silicone mould. Materials of this product include: ABS, PP, PC, PMMA, high-temperature resistant material, flexible glue and silicone rubber.

Used for prototypes, one-offs and low volumes, vacuum casting can replicate almost all the properties of injection molding. It is primarily used to mold two-part polyurethane(PUR), which is available in a vast range of grades, colours, transparencies and densities.






What is Vacuum Casting?
In stage one, the liquid PUR is drawn into the mold which is held under vacuum. This ensures that the material 

has no porosity, will flow through the mold cavity and will not be restricted by air pressure. The PUR is held 

high above the mold,so as it is poured into the mold and runs underneath gravity forces it to rise upwards. 

The runner is designed to supply a curtain of liquid PUR. It flows through the mold and up the risers in part A. 

There are lots of risers to ensure that the mold is evenly filled.


After a few minutes, the mold cavity is filled and the vacuum equalized. The mold is left closed for the complete 

curing time, which is typically 45 minutes to four hours. In stage two, the part is ejected and the flash, risers 

and excess material are removed.


QUALITY

Surface finish is excellent and will be an exact replica of the surface of the pattern used in the production for 

the mold.


TYPICAL APPLICATIONS

Prototyping applications include automotive parts, live hinges, keyboards and housings for mobile phones, 

televisions, cameras, sound systems and computers.

COST AND SPEED

Tooling costs are generally low, but they largely depend on the size and complexity of the pattern. 

A mold will usually take between half a day to one day to make in silicone and will last 20-30 cycles, 

Cycle time is good.


MATERIALS

PUR is available in water-clear grades and the full colour range. It can be very soft and flexible(shore A 

range 25-90) or rigid(shore D  range).


ENVIRONMENTAL IMPACTS
Accurately measuring the material reduces scrap, which cannot be recycled because it is a thermosetting 

plastic. The process is carried out in a vacuum chamber, so any fumes and gases can be extracted and 

filtered.


Three steps of processing prototype casting:

Before manufacturing silicone mould, it needs to manufacture the prototype first. The prototype can adopt 

more common ABS material, for example CNC processing is ok.


Silicone mould

After preparing the prototype, it’s time to start manufacturing silicone mould.

After drying for eight hours, cut up the silicone mould and take out the prototype. At this point, the silicone 

mould is ready.

The above are processing steps of casting. You can quickly make batch of prototypes through the three steps.

Definition: The vacuum injection, that is vacuum casting, is to make use of the original sample to manufacture 

the de-aeration, stirring, preheating and injection for cast ables under the vacuum state, in order to clone the 

copies the same as the original samples. This technology has a high speed and a low-cost, and it can also 

greatly reduce cost, cycle and risk of developing product.


The materials firstly need to be made prototype before manufacturing a silicone mould. After preparing the 

prototype, it can start manufacturing the silicone mould. After drying for several hours, cut up the silicone 

mould and take out the prototype. At this point, the silicone mould is ready. Inject the liquid gum material 

into the silicone mould, and it will be ok just after drying. Both the poured liquid material and the silicone 

material of silicone mould are called by a joint name as vacuum injection material, also called casting material!




 
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