Radial tyre building process

a) Green Tyre Forming

The first stage of building a radial tyre is to locate the beads onto a cylindrical flat forming drum, followed by a series of components which will form the base structure of the tyre and link the two beads together. The tubular shaped carcass is then transferred to the second stage.

b) Green Tyre Shaping

The second stage of construction begins by loading the tyre carcass onto a second drum, the tyre is the shaped and breaker belts are applied, followed by the sidewall and tread components.

At each stage of the construction great care is taken to apply pressure, with the view to expelling all air between each layer and to consolidate the assembly.

Radial tyre building methods

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1-Stage Assembly

The tyre carcass is built on an assembly drum. Components can be added for example in the following order:

1. sidewalls
2. chafers
3. innerliner
4. ply materials
5. belt materials / tread rubber

The assembly drum used in 1-stage assembly consists of a shaping bladder, turnup bladders and supporting bladders.

• Beads are fitted onto the drum using specific bead applicators.
• By inflating the shaping bladder, the stretching of the tyre carcass begins. Whilst this is being done, the distance between the beads shortens.
• The application of the belt and tread package takes place beforehand, and its is done on a separate drum. With the help of a transfer ring, the package is moved onto the shaping assembly drum.
• The tyre carcass is stretched and attached to the belt package.
• The tread and belt package is stitched carefully onto the tyre carcass.
• Turnup bladders are used for completing the ply turnup phase, when also the chafers and sidewalls are put into their correct places.
• Support bladders are used to ensure that the turnups are properly made all the way.
• Pressure is aspirated from the turnup bladders and support bladders.
• In the stage to follow, the sidewalls and bead area components are stitched.
• After the shaping bladder has been deflated, the tyre carcass can be taken off the drum.

Advantages:

• Suitable for long production batches.
• As far as work stages are concerned, a reasonably fast method of production.

Disadvantages:

• Suitable only for the production of open construction tyres.
• The drum required is complex and expensive.
• Changing the machine settings is a slow procedure.
• The bladders have to be made separately, which results in high operating costs.

2-Stage Assembly

1. Stage

Building the carcass follows the same procedure as used in the manufacture of cross ply tyres.

The components fitted in the assembly stage:

• innerliner
• ply materials
• beads
• insulation rubbers
• chafers
• sidewalls

The tyre is built on a regular assembly drum.

• The process starts with the fitting of the innerliner and is followed by the fitting of the carcass material and bead wires.
• Ply turnups are made either by stitching or using spring method (selection of method depends on the construction of the building machine).
• The components are stitched together.
• The chafers and sidewalls are put into their correct places, after which the materials are stitched together.
• The tyre carcass is offloaded from the drum and transferred on to the next phase.

2. Stage: Shaping

• The tyre carcass is fastened onto the shaping drum, and the bead area and the flanges are brought closer together.
• The stretching of the tyre carcass begins and the distance between the beads shortens.
• The application of the belt and tread package takes place beforehand, and it is done on a separate drum. With the help of a transfer ring, the package is moved onto to the shaping assembly drum.
• The tyre carcass is stretched and attached to the belt and tread package, after which the transfer ring is removed from the drum.
• The tread and belt package is stitched carefully onto the tyre carcass.
• The stretching pressure is released from the tyre carcass, and the green tyre is taken off the drum and moved to intermediate storage.

Advantages:

• Suitable for short production batches.
• Changes between different sizes can be made quickly.
• The drums and any other equipment required are cheaper and less complicated than those used in the 1-stage method
• Possible to apply to the production of a closed construction tyre.

Disadvantages:

• More space required for the equipment.
• Requires more material processing than the 1-stage method.

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