Retread manufacturing process

The very first step before the start of production is the collection of worn out tyres (the so-called casings) from the customer, which we transport to our warehouse. If the customer does not have casings, we also offer stock retreads including casings directly for sale.

Before production begins, experienced personnel will carry out a visual inspection on the stretching machine to determine the condition of the casing.

During the initial inspection, the casing is also subjected to a pressure test corresponding to the tyre's operating pressure. If no defects are detected, in particular cord separation, production starts.

The remnants of the old tread have to go away. The automatic buffing machine not only removes the rubber layers right up to the first tire bumper, but roughens the casing surface so that the bonding rubber then adheres as well as possible.

In the place of exposed wires of the casing, it is necessary to carry out the repairs by thorough grinding using a special disc, including subsequent treatment with a grinding stone.

For perfect vulcanisation, the casing must be free of dirt, water and grease. As a precautionary measure, a so-called cement (vulcanising compound dissolved in petrol) is applied to the buffed casing in the spray booth to form a protective film on the casing.

Casings that are diagnosed with a repairable puncture or hole during the initial inspection or pressure test are professionally repaired using modern repair materials.

At the latest 3-4 hours after the buffing, the exposed and ground wires of the casing must be repaired with a repair bindegum by means of an extruder, which heat-treats the bindegum into a ductile form and extrudes it into the exposed area by means of a screw device.

Rolling the new tread must be done under a uniform pull around the circumference of the tyre, which is ensured by an automatic rolling machine that also uses a laser to precisely roll the tread in the casing shoulder.

Three factors are important for thorough curing: time, temperature and pressure. To achieve maximum pressure, an envelope is used, from which air is sucked out by a vacuum machine when the tread is mounted on the casing, thus maximising the pressure of the tread on the casing.

The wrapped casings, including the tread, are placed in envelopes in an autoclave where they are connected to a suction system so that a vacuum can be maintained throughout the vulcanisation process. The autoclave is pressurised to 6 bar, which further pressurises the pressure between the tread and the casing and heats it to the prescribed temperature. The vulcanisation process is carried out according to a precisely defined optimum time, depending on the type of fasteners used.

After vulcanisation, a visual check is made to ensure that everything is in order, followed by a final pressure test to ensure that the carcass has not been disturbed during vulcanisation.

The final step in the finished product is the surface treatment in the form of a new coating of the sidewall with black tyre varnish and then stacking. At this point, the tread is ready for dispatch to our customers.