How are Rubber Moulds Made?

Rubber moulding is the process of taking the rubber mixture and placing it into a metal mould frame to create a mould made of rubber. There are three ways in which to create moulded rubber, being compressing, transferring, or injecting rubber into the metal frame. The polymer chains in the rubber then interlink through the process of vulcanisation, or curing, as a result of the pressure applied in the moulding process. A fourth method, extrusion, may also be used but it is done without using a mould.


Compression Moulding


In compression, a two-part shell mould is used. Once the vulcanised rubber is placed into the mould, it is then closed and put through a process of pressure and heat. Once the rubber reaches the desired temperature, it begins to harden and cure to form the shape of the mould, after which the moulded rubber is removed. The pressure that is applied forces the rubber to fill all the cavities within the mould. The end product then has good dimensional stability and a good surface finish.


Injection Moulding


Injection moulding is used to make products that require precision and accuracy in their production. The rubber is first heated to a temperature where it is the consistency of a liquid so that it can be easily inserted into the mould and better able to flow. The mould itself is tightly closed and the rubber is inserted through a nozzle situated on the mould into a cavity. The liquid rubber then fills the mould and goes tightly into all the intricate parts. Injection moulding has a wide range of design capabilities to create moulded rubber and is relatively low cost.


Transfer Moulding


Transfer moulding is a combination of both compression and injection moulding. The liquid rubber is inserted into the section of the mould called the pot, where after it is forced into the various cavities by a heated plunger through a section called the sprue. The rubber is then allowed to cure and once cured, the mould is opened and the moulded rubber is removed. Transfer moulding enjoys both the high automation of injection moulding and the low cost of compression moulding.


For all your rubber mould needs, contact Delta Rubber today, your moulded rubber engineering company of choice, to find the perfect rubber mould for your particular application.



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