Take a look at how Silicone Engineering’s silicone materials are manufactured, from receiving the raw base material via Goods In, to the finished silicone product leaving via Goods Out!

Food processing silicone line

Here at Silicone Engineering, we are very fortunate to have outstanding mixing and compounding facilities and process in excess of 2000 tonnes of HTV silicone per annum. It all starts in The Mill Room which acts as the hub of the business giving Silicone Engineering the capability to kit, mix and blend our own custom silicone formulations and grades.

Silicone compound

In essence, the Mill Room is where our silicone products start their journey, a bit like the mixing bowl when making a cake. Specific formulations are used to weigh out the ingredients which then get placed into a mixer to be fully blended into one consistent mix.

Mixing machines

Once the raw materials have been assembled by the Mill Room, a mixing machine is then used to integrate the material more comprehensively creating a silicone rubber compound. As mentioned above, the process is similar to mixing cake or bread ingredients which is why these machines are sometimes affectionately referred to as “dough mixers”.

Silicone Mixing Machine

The fundamental purpose of our mixing machines is to ensure the silicone base, colour pigments, additives and any other ingredients are blended and mixed together as efficiently as possible. If you get it wrong at this stage, then the rest of the processing stages are most likely to have issues.

Conversion machinery

Once mixed, the new silicone compound is now ready to undergo its transformation from a simple silicone compound to a fixed silicone rubber product – enter the conversion machines! These are the machines that convert the compound into many different formats such as sheets, rolls, strips, tubes, profiles and sections.

At Silicone Engineering, we have categorised our conversion machines into 2 types – Calenders and Extruding machines.


Calendering is Silicone Engineering’s specialty and we have been experts in this field for over 40 years. In its simplest form, it is the process of making silicone compound into sheets and rolls by using a calender(s). The calender is a series of large rollers (bowls) which can be set close together to pre-form sheeting products. Once set to the correct width and thickness the sheeting then comes off the bowls and onto a curing belt which transports it to a pre-cure oven set at high temperature. As the sheeting travels down the curing line and into the heat of the oven, a process of chemical cross linking occurs activated by heat which sets the sheet in a fixed shape, in this case a silicone sheet or roll.

You can watch the full process here:


Silicone compound is fed into the extruder which is essentially an Archimedes screw inside the fitting barrel. The extruder is designed to place the silicone under great pressure which expels all air from the compound before being forced through a shaped die according to the required shape needed. The same process as sheeting is used to set the extrusion to a fixed product by the introduction of heat, firstly by a pre-cure then a post cure once it is set.

Silicone Solid Extrusion at Silicone Engineering

suraSil™ Solid Silicone Extrusions for Food and Beverage Applications

Sponge Extrusion at Silicone Engineering

expanSil™ Silicone Sponge Extrusion

The Journey continues

The journey is not over for the newly converted silicone product, from its conversion from silicone base to a silicone rubber product such as sheeting or tubing. Secondary actions like jointing or adhesive backing now come into play to further continue the manufacturing process. Jointing is when an extruded part is joined at each end to form a complete gasket or seal. By vulcanising each end together gives an extremely strong join which forms complex seals for a number of different applications such as seals for food machinery. Our adhesive backing department take the sheets and/or rolls and apply a pressure sensitive adhesive backing system to one side, making it easier to apply the finished product once in application, whilst giving the sheet added strength.

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