The Need
All tyres are prey to wear and tear .Some are to a lesser extent and others are more. In either case tyres can be redeemed. As long as the tyre casing is intact, which is about 75% of the entire tyre, retreading is possible. The tyre regains its original condition and is ready for use as good as new.
Retreading Process
There are several kinds of Retreading processes available today.
The traditional hot process or mould retreading method is one. But technological developments have rendered this method obsolete. Instead, the cold process retreading method or Precured Process, enables tyres to have increased life span and assures more mileage. It is also suitable for all types of tyres.
Precured Retreading Process
This process entails inspection, buffing, building, repairing and curing. The top surface of casing is buffed and a thin coat of vulcanising solution is applied. A fast cure cushion gum is applied on the surface of the tyre. Precured tread, with a readymade design suitable to the tyre is built on it.
The Tyre is then wrapped in a thin rubber envelope. Bonding is carried out in an electric chamber or steam bonder for a specified time.
Retreading Process
There are several kinds of Retreading processes available today.
The traditional hot process or mould retreading method is one. But technological developments have rendered this method obsolete. Instead, the cold process retreading method or Precured Process, enables tyres to have increased life span and assures more mileage. It is also suitable for all types of tyres.
Precured Retreading Process
This process entails inspection, buffing, building, repairing and curing. The top surface of casing is buffed and a thin coat of vulcanising solution is applied. A fast cure cushion gum is applied on the surface of the tyre. Precured tread, with a readymade design suitable to the tyre is built on it.
The Tyre is then wrapped in a thin rubber envelope. Bonding is carried out in an electric chamber or steam bonder for a specified time.
Precured Process Benefits-
- The Rubber used for precured method is of even thickness and density
- The absence of high temperatures and pressures enhances casing life.
- Suitable for different tyres, sizes and applications.
- Multi -retreading of Tyres.
- Lower cost per kilometer of vehicle running.
Choice of various designs to suit different applications.
Retreading Process
Initial Inspection
Each
tyre received in a retread plant is subjected to a rigorous visual
inspection. Inspectors are assisted by the use of non-destructive
sophisticated inspection equipment.
We also purchase a new machine (Inspection Spreader).This
Inspection Spreader designed to detect pinholes, nail holes, cuts,
cracks, porosity,etc,Automatic tyre rotation stop when penetration
detected with sparks.
Buffing
The
tyre’s old tread is mechanically removed on high speed buffers.
Today’s buffers are extremely accurate and will remove the proper
amount of old rubber while turning the tyre to an exact specified
diameter and radius.
Skiving & Repairing
With
advances in state-of-the-art repair materials and repair methods,
many of these tyres can be routinely repaired and in most cases can be
retreaded when the original tread is worn off. The repair station is
where any surface injury is treated using effective material and tools
for grinding and patching.
Cementing & Filling
Even
in small injuries it is critical that the injury is cleaned and
filled. If this is not done, severe rust, separation and steel cable
looseness could take tyre out of service. The injury should be
inspected, and then cleaned out with a carbide cutter. After cementing
the injury, a vulcanizing rubber stem should be applied to “fill” the
injury. This would create a permanent repair that maximizes tyre life.
Building
In
the pre-cure system, the tread rubber has already been vulcanized
with the new tread pattern design. The buffed tyre needs a thin layer
of cushion gum to be wrapped around its crown area. The pre-cured
tread rubber is then applied with the building machine. This is called
the building process.
Enveloping, Rim Mounting & Double Envelope System
a) The built tyres are then mounted with envelops and rims to prepare them for curing.
b)
For enveloping, tyres are first fitted an outer envelope at the
envelope-mounting table before the inner envelope is fitted into them.
The enveloped tyres are then vacuumed out for preparation prior to
curing. Modern plants have their casings hoisted by monorail systems.
Curing by Chamber (Precure)
The
Precure Tread system is a process by which a tread pattern is fully
cured or vulcanized into the tread by using a press. The tread is then
vulcanized onto a tire casing using a bonding layer of uncured
natural rubber. The tyre is vulcanized with heat, time and pressure in
a curing chamber that bonds the tread to the casing. This thin layer
called precure cushion or bonding gum. Cold retreading was then a term
used to describe a process in which the final curing of retread is
done at temperature lower than 115c.
Hot Process (Hotcure)
Hot retreading is the term used to
describe the retreading process in which the curing of retread is done
at a temperature of above 140c. It employs a steel or aluminum mold
with a tread design cast or machined into it.
Final Inspection (Presure Test) & Painting
- Tyre inflation pre-set at 2, 4 & 8 bar (max) for a better QC inspection.
- Enclosed by steel cage as safety protection.
- Testing cycle ended automatically to reduce supervision work.
- Well lighted within the cage for better visual inspection.
All retreaded tyres are encouraged to be returned with the sidewalls painted using a light coat of black tyre paint.
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