Shaping of RubberShaping processes for rubber products can be divided into 4 basic categories: 1.Extrusion 2.Calendering 3.Coating 4.Molding and Casting
Extrusiono Unvulcanized rubber compound is fed into the screw extruder.o Flutes of the revolving screw carry the rubber into the die.o Pressure forces the material through the opening where it swells.o Swelling occurs because the polymer is in highly plastic condition and exhibits the ‘memory’ property.
Extrusion Dieo Tool made by cutting an opening shaped in the form of the finished rubber cross-section.o Rubber compounds tend to swell passing through this die.o Hence each die is made according to each part to ensure all tolerances are made.
Calenderingo Calender is a machine to form rubber sheets into various thickness, widths and lengths.o It consists of rolls which are run at various speeds and temperatures.o It is applied when a smooth and flat surface is desirable.o It is used in manufacturing of tires.
Roller Die Processo Combination of extrusion and calendaring resulting in better quality product than either extrusion or calendaring. Rubber extrusion followed by rolling
Coating Fabrics with rubbero An important industrial process for producing automobile tires, conveyer belts, inflatable rafts, and waterproof cloth tents and rain coats. Coating of fabric with rubber using calendaring process
Moldingo Principal rubber processes are : 1. Injection Molding 2. Compression Molding 3. Transfer Moldingo Molded rubber products include: 1. Shoe soles and heals 2. Gaskets and seals 3. Suction cups 4. Bottle stops
Injection MoldingoRubber is heated and placed under high pressure per square inch of cavity surface in molding.oMaterial is mixed in bulk and then stripped immediately.oStrips are fed into a screw, which fills the barrel with the rubber material.
Compression MoldingoRubber compound is taken and ‘pre-form’ is created in the shape of the end product.oMold is closed applying heat and pressure to the pre- form, allowing it to fill the cavity.
Transfer MoldingoIt also requires preparation of preforms.oHowever pre-forms are placed between top plate and plunger.oMold is closed, material is compressed by the plunger and transferred through sprue’s into the cavity.
NOW A VIDEO COMPRISING ALL THE METHOD IN MAKING OF TYRE