STEEL CORD CONVEYOR BELT PRODUCTION LINE
Extrusion ("Roller Head") offers two decisive advantages:
1) High uniformity of the material thickness over the entire sheet width, which ensures that there will be no air inclusions, even at higher thicknesses.
2) An outstanding homogeneity of the material produced.
This is possible because the "Roller Head" unit can (in comparison to a classic calender line) produce sheets of up to approx. 20 mm thickness without trapped air.
The rubber compound is plasticized in the extruder and then fed into the preform head. It enters the calender directly in the roll gap, and is distributed over the entire working width of the calender. This direct feeding prevents the build-up in front of the nip, that would otherwise be expected as well as air inclusions, so that the sheet preformed in the head can have a thickness of 10 mm to 30 mm, which the calender then calibrates to the desired end thickness. The extruder has the same principle as a meat-grinder, with a screw that feeds the compound through a die. The compound is heated by friction and the extruder is cooled with water.
The drawing shows a calender with 3 rolls which revolve in opposite directions. Rubber is being pressed in and onto the conveyor belt fabric.
A 4-ball unit offers the advantage of working air out of the rubber more thoroughly.
Continuous Belt Curing Machine (Rotocure/Auma)