Extrusion Process

Let us now see the extrusion of a typical cap-base tread using a opposing duplex hot
feed extruder. The various steps involved in the actual production process are
detailed below.

PROCESS

1. Start the temperature control unit at least half an hour in advance so as to get the
required
head temperature as per running code specification.
2. Follow the extrusion specification for the respective product code.
. 3.Heat the required preforms and dies for at least half an hour in advance of start of
extrusion.
4.Clean the mill guides and mill pan.
5. Arrange the specified compounds from the storage area. Follow up of FIFO is
desirable.
6. Set the break down mill nip as per running code specification.
7. Start break down mills and load the specified OK compounds in to the respective
mills.
8. Open, mill-cooling water lines.

9 .Start the feed mills and transfer the warmed up stocks from the break down mills to
feed mills as and when instructed by the operator.

10. Make use of water cooled blender rolls in feed mills to get homogeneous
mix of the compound.
11. Set the nip and feed width of both feed mills as per the respective
specification using feed knives and templates respectively.
12. Arrange / set the line marking unit and printing unit for running code color
line identification as per running code specification and for date and shift
identification
13. Arrange empty leaf trucks/side wall books.
14.Set the cushion calendar temperature as per running code
specification.
15. Start cushion feed mill and load the compound as per running code
specification.
16. Feed, cushion compound strips of specified dimensions to the cushion
calendar as and when instructed by the operator.
17.Cut out the strips from the cap and base feed mills and convey to the
extruders using overhead conveyors.
18 As the strips from the feed mills enter the feed hopper, start the screw at a
slow speed and increase the speed gradually.

19. When the stock runs smoothly from the head opening, stop the extruder,
cut the extrudate, insert the specified preform and die and lock the same
properly using die clamps. Apply soap solution on preform and die before
insertion.
1.
20. Start the extruder and set the screw R.P.M of extruders and line speed as
per guidelines given in running code specification. Lead the extrudate
through take away conveyor, check the dimensions and make necessary
adjustments.
21.Set the width and gauge of cushion as per running code spec
22.Apply the cushion to the bottom side of tread.
23.Engage the disc rolls to avoid air traps if any. (Applicable for tread cushion
assembly)

24. Polythene may be applied on bottom side of tread as indicated in the
respective specification.
25. Set the linear weight in order to maintain the specified dimensions and
weight for the extrudate by adjusting the speed of the shrinkage
conveyor.
26. Engage line marking and printing units.
27.Lead treads to cooling conveyor through inclined conveyor. Sidewalls can
be by-passed after first cooling conveyor.
28.Set the skiver for the running code.
29.Start the skiver when the extrudate reaches the skiver and then start the
blower for removing water drops.
30. Set the specified weight on the weighing scale as per running code
Specification

31.M onitor the weight for every extrudate tread/side wall.
.
32. Checks dimensions of the extrudate periodically and enter at
least one set of readings for each code, in the process control register
33.In case of any variation, necessary adjustment to be made in the operations.
34.Book the treads, which are within the specified tolerances
in the leaf trucks with the cushion side up with out touching each other.
Identify the truck by a tag and transfer to the storage area
35.Book sidewalls that are within the specifications with a tag in the leaf book
and transfer to storage area.
36.Non-conforming treads to be slitted. After slitting each compounds to be
kept separate on skids with work away tag.

37. Whenever extrudate is going out of specification continuously (say beyond
the control of the operator) to be held for disposition with hold tag after
intimating the concerned supervisor. The details to be entered in the held
up register.
38. If lumps/F.M are observed in the mill, sheet out the compound, identify
each sheet with a crayon and allow the sheets to cool. After cooling, stack
the sheets on a skid/rail and hold for disposition using a hold tag.
39. Operator should record all process parameters as listed in the process
register.
40 In case of any abnormalities in the process, the operator should inform the
matter to the concerned section in charge.

Following are the general guidelines for unit stoppage..


1.Cut the feed strip and run the screw at low speeds(3 –5) rpms
2.Remove the preform and dies.
3.Follow push out/clean out procedure.
4.Sheet out all the compounds from mills and allow to cool
5.Stop the mill and close cooling water lines.
6. Identify each sheet with crayon for date, shift and code
7.Stop all accessory units, chilled water spray etc after clearing the extrudate
from the cooling line.
8.Keep the preform and dies in the Hot chamber.