Rubber is an indispensable material in modern life and while it can be obtained from both synthetic and natural sources, do not come in the shape of usable things. Rubber is obtained from elastomers which is actually untreated and uncured and is a blob of rubber which has to be moulded in the shape of the object that one is trying to get. Rubber is great for manufacturing materials which are required to expand or contract according to the pressure forced on it. Elastomers can be derived from both natural and synthetic sources but it is mostly treated in factories and chemicals are mixed with it to make objects more durable and strong. Rubber moulding is the process by which this material is moulded to form objects and there are three main processes associated with it – compression moulding, rubber injection moulding and transfer moulding. All of the three processes mentioned include the same techniques as that of rubber moulding.
Steps of rubber moulding:
Different types of procedures for moulding of rubber:
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Steps of rubber moulding:
- At first the blocks of elastomers are pressed together and put into a rubber moulding cavity. This cavity is made of metal which helps to keep the shape of the object intact.
- This rubber is then heated and when the elastomers boil, they expand and contract accordingly to mould into the perfect shape of the object. These two steps are included in all the processes of rubber moulding.
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| Rubber Moulding |
- Rubber injection moulding: In this process the rubber mould is heated and closed at first. Then the uncured elastomer is injected into this mould. In this process, the injection unit and the press unit have separate operating units or controls. It is advantageous if the opening of the feed for the rubber strip is placed at a height which is amenable to the whole process. The rubber mould is obtained by having a short injection time and high pressure while injecting the liquid rubber into the mould. The advantages of rubber injection moulding can be checked out below:
- Blanks are completely eliminated so the process is relatively easy to handle.
- The mould is completely closed which means that flash cannot be formed and thus the process becomes easier.
- Flow channels and complex cavities are easier to fill.
- The process is pretty amenable to automation.
- Compression moulding process: This process requires the rubber or elastomer compound to be formed into a blank and this blank is then placed in the moulding cavity. The advantages of this process can be checked out below:
- It is the most primitive method for rubber moulding and has been there for centuries. This procedure is getting modernised now but it is still relatively simple compared to other processes.
- Other products can also be manufactured which does not contain rubber.
- It is the most suitable process to manufacture objects with large surfaces or large spreading surfaces.
- It can also be used effectively for rubber which has high viscosity and thus flow poorly.
- Transfer moulding: The blanks are preheated and loaded into heat chambers and distributed into several cavities. The advantages of transfer moulding are as follows:
- As manufacturers prepare blanks and handle them, it becomes difficult to keep control over the whole process. Transfer moulding makes it easier.
- The curing time is much reduced as the rubber is manufactured from before.
- Molten rubber flows into the cavities easily and fills them more efficiently.
- This process is especially good for bonding of rubber and metal and a fresh surface is necessary for this to take place which is generated here.
