Bias cutting process

· Plies, Breaker, Flipper and Chafer are cut at required
green angle and width using bias cutters.
· Normally the angle of cutting ranges from 54°to 66°to
get a cured angle of 32°to 40°.
· Calendered fabric, wound in PP liners (60”), loaded at
let off is cut and cut fabric (plies) are joined (spliced) into
continuous length and wound in PP liners (20” to 64”).
· These cut plies are identified with tags and send for
further processing.


SQUEEGEE CALENDERING

· Squeegee calendering is the process of making thin sheet
of rubber compound using 2 roll, 3 roll or 4 roll calender.
· Squeegees are used at the inner most layer of the tire
(Drum squeegee) and also in between the different plies (ply
squeegees).
· Inner ply and outer ply squeegee are applied using 2 roll/
3 roll calendar

Why squeegee is applied:
· The increase in diameter from green tire to cured tires
(cylindrical green tire to torroidal cured tire) results in high
stretch at the center and the shoulder. This necessitates higher
rubber gauge at the center and shoulder.
· lso in heavy loading tires, the turned up plies shall end on
squeegee.
So squeegee is applied on the plies.

Types of Squeegees

· Inner liner (for TL tires)
· Drum squeegee
· Inner ply squeegee
· Outer ply squeegee

Inner liner

· Used in tubeless tires
· This acts as an impermeable membrane inside the tire
preventing the air loss.
· It is usually made of higher green strength compounds.
· The innerliner is made of halo-butyl compound (Normal
tube compound is based on butyl rubber, which is not
compatible with natural and synthetic rubbers).

Drum squeegee

· rum squeegee is applied as the inner most layer, below
the 1st ply, above the drum.


· It protects the tube from ply cords (against puncture) and
also protects the carcass from the moisture.
· In the case of tubeless tires, drum squeegee is applied
above the inner liner basically to prevent the penetration
of liner compound into the ply.

Ply squeegee

The coating of rubber on the plies is to absorb the shear
strain between the layers and to prevent cutting between
the cords.
The lift taking place from the cylindrical green tire to the
torroidal cured tire necessitates the usage of higher
gauges of rubber between the plies in the center portion of
green tire.
A cost effective way of achieving this higher green gauge
is by using squeegees.

Why different gauge squeegees:

The lift taking place from the cylindrical green tire to the
torroidal cured tire increases towards the crown, arises the
need for higher gauges of rubber between the outer plies
and the breaker.
Thus the higher gauge of outer ply squeegee and the
breaker is to compensate for the higher lift at the center
portion of the tire and to absorb the higher shear strain
on the outer layers.

The process

Broken down and properly blended compound with
specified dimension is fed to the nip of the calender rolls
through the conveyor, where both the rolls are at the specified
temperature
The nip gap and the knife assembly at the back of the
calender rolls are to be adjusted to get the required squeegee
dimension.
This squeegee will then pass through the cooling drums to
reduce the squeegee temperature and then applied over cut
ply.

Drum squeegee is prepared at the 3roll/2roll calender. It
is wound in polypropylene liners or applied below first ply.
Ply squeegee preparation and its application on to the
plies are accomplished simultaneously at 2roll / 3roll
calender.
The squeegee should be applied centered on ply and to be
wound in polypropylene liners in the wind up unit and tagged
properly.
These rolls are stored at storage areas or sent to tire
building for assembling.

Good Quality Squeegee

1. Homogenize the compound by milling of the
compound using break down mill and feed mill.
2. Ensure correct gauge and width of feed strips.
3. Ensure specified TCU set temperature.
4. Specified usage of work away, if any.
5. Correct nip gap setting to get the specified squeegee
gauge.

6. Correct width setting by the knife assembly provided
on the calender roll.
7. Maintain the speed of squeegee line and calender
within specification.
8. Ensure water circulation in the cooling drum.
9. Use wrinkle free and rewound liners.
10.Use shells of specified dimensions and undamaged
one.