Rubber Compound Molding Machine: Extrusion Machine & Calender Machine 

Function 

Shape or mold the rubber compound to suit the rubber finish product profile. 

Molding Principle 

Processing of rubber compound so it can be shaped easily as per needed. During processing, compound may be solidified, softened, or liquefied first, depends on rubber finish product which will be produced. 

Rubber Compound Molding Machine Type 

1.       Extrusion Machine (Extruder) 

Extrusion machine is used to shape or mold rubber compound become solid or hollow long shape with round, rectangular, triangle profile, etc. Final shape of compound is same with die profile used. Compound is softened inside the hot cylinder (barrel) by using the screw/ram rotation mechanical action so compound will be easily sprayed or discharged through molding. Screw and barrel are the important unit of extruder/extraction machine. Barrel wall and sometimes inside part of screw have the hollow which can be flowed with heating and cooling medium. Others important unit at extruder machine include counter rotor, heating and cooling unit, transmission equipment, rotation controller, and lubrication, front unit (screen, breaker plate, die), compound feeder unit, and powder. 

Screw Extrusion Principle  

Feeding material (rubber compound) is fed into extruder machine through hopper which is usually completed with feed roller. After entering screw through feeder bag, material will move and rotate through screw parts, such as feeding, compression, and soften parts. 

The thread of a screw height is various at screw parts, and it is adjusted with material phase change inside the barrel which load different room volume. The highest screw is available at feeder part and the lowest screw is available at extenuation part. Material get heat energy from barrel heater and also from rotated screw mechanical work and the friction with material inside the barrel. 

Extruder Machine Type: 

1.1. Cold Feed Extruder 

A cold feed extruder machine is an extruder machine that proceed compound at room/ambient temperature, with granular ribbon/tape form feed. The machine screw is quite long, but the screw flight depth is slightly narrow. 

1.2. Hot Feed Extruder 

A hot feed extruder machine is an extruder machine that proceed compound at above room temperature. The screw is quite short, but the screw flight depth is slightly deep. Generally the ratio length and depth of screw (L/D) for low pressure operation is 5:1, and for high pressure operation is 8:1. 

1.3. Ventilated Cold Feed Extruder 

A ventilation is installed at the barrel of this extruder machine, so the trapped gases inside the compound during processing can be taken out. There are two (2) zones at this extruder machine i.e.: 

I.                    Feed, transmission, and metering zone 

II.                  Transition and metering zone 

The screw L/D ratio at first part is 8:1, and at second part L/D is 12:1, or the total L/D, ratio 17:1 and 20:1. 

1.4. Extruder Using A Pen 

A pen is installed at the barrel of this extruder machine to cleave the compound layer area that enlace screw channel.  A pen can avoid slip inside the barrel so the material become more uniform. Installing of pen is arranged in radial way with quantity 8-12 pieces and 6-10 rows, it is calculated starting from the feeding hole. 

2.       Calendar Machine 

Calendar machine is used for: 

·         Produced thick or thin, wide and long compound (compound sheet). 

·         Coat the compound to the fabric. 

·         Put compound into the fabric by giving friction. 

·         Coat the compound on the fabric surface which has been got friction or rubbery fabric (skimming). 

·         Put double line of rubber sheet or rubbery fabric. 

·         Shaping the compound on the roller surface (profiling or embossing). 

Shaping of compound is made by pressing the compound or rubbery fabric between the rollers and arranging the direction, big of rotation and rollers distance. Different roller rotation will cause friction, and same roller rotation will cause sheeting (pressing, lining, and smoothing the compound surface). 

Based on the number of roller and its usage, calendar machine type is classified to: 

1.       Two (2) rollers Calendar 

2.       Three (3) rollers Calendar 

3.       Four (4) rollers Calendar 

4.       Five (5) rollers Calendar 

5.       Six (6) rollers Calendar 

Based on the composition of roller arrangement, calendar machine type is classified to: 

1.       Composition I calendar machine 

2.       Composition I¯ calendar machine 

3.       Composition L calendar machine  

4.       Composition Z calendar machine 

Rollers are made from hard steel or cast iron, around 500-550 BHN, with smooth surface. Hollow is made inside parts along roller fuse, it is function as canal of heating and cooling medium. 

Others important unit at calendar machine include : 

·         Motor counter and its transmission 

·         Controller or roller rotation and distance 

·         Heating, cooling, and lubricant unit 

·         Cutting unit, separator rollers, and safeguard 

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