The following blog will explore the Silicone Engineering manufacturing process, from receiving the elemental ingredients into Goods In, to a silicone rubber product leaving us at Goods Out!
Here at Silicone Engineering, we are very fortunate to have outstanding mixing and compounding facilities. The Mill Room is the hub of the business giving Silicone Engineering the capability to mix and blend our own custom silicone formulations and grades.
In essence, the Mill Room is where our silicone products start their journey, a bit like the mixing bowl when making a cake. It is all about weighing out the silicone and additives, placing them into a mixer and fully blending into one consistent mix.
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 menitioned above, the process is similar to mixing cake or bread ingredients which is why these machines are sometimes affectionately referred to as “dough mixers”.
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.
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 3 types – Calenders, Extruders and Moulding 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 and/or rolls.
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
Moulding is the process where we produce the parts by pressing the silicone compound between two metal platens to expel all the air from the compound, this is done under very high pressure and heat. The metal plates have the shape of the part already etched out so that the silicone will take that form.
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.