The next two processes are sidewall and tread preparation. Both the sidewall and the tread of a tyre are produced by a process called extrusion. A machine, referred to as an extruder, is used for this process. An extruder can be thought of as screw pump that heats the rubber compound and forces it out through a die. The one that Apollo uses in its manufacturing plant is capable of extruding 3 different compounds at a time- meaning 3 compounds can be mixed into one single compound for a desired spec-tyre. Post extruding, the compound is cooled off and then the tread or the sidewall is cut depending on the exact size of the tyre. Similarly, the bead in a tyre, which is made up of steel, is also rubber coated by extrusion process.
3. Tyre assembly (Green Tyre):
Once the tread, inner-liner, ply, sidewall, bead and belt are prepared, they are all sent in for the ‘assembly’. The assembly of tyre is done using a Tyre Building Machine (TBM) where all the components are sequentially assembled so as to form a raw tyre, also known as ‘green tyre’.
To give you a clearer view, a TBM is a giant horizontal roller drum. The raw or green tyre is assembled on it inside out, i.e., starting off with the inner-liner first and so on. So how does it work? The inner liner is wrapped over the roller, and then the body plies are applied. Both the components are then joined by bead on either side. The sidewall and tread are also added during the same phase. Once all the components are assembled, the TBM presses all of the components together, imparting the ‘assembled part’ a circular shape or tyre-like shape (see in the picture above for reference). The final product from this process, the green tyre, is then sent to the next process- Tyre Moulding.
4. Tyre Moulding:
Technically, moulding is the final step in the making of a tyre. During this process, the green tyre is cured, or vulcanized, by compression moulding process. This gives a tyre a road-worthy and functional shape. However, there’s more to it than just that. Moulding or curing of rubber also brings a number of chemical changes in the tyre that are crucial for its functioning.