Full definition
An open rubber processing machine consisting of two parallel, counter-rotating, temperature-controlled steel rolls (typically 150-660 mm diameter, 300-2,100 mm face width) with an adjustable gap (nip) between them. The front roll rotates slower than the back roll (friction ratio 1:1.1-1.4), creating shear that works the rubber and incorporates ingredients. Uses: (1) Finish mixing — adding curatives to a Banbury-mixed batch at controlled temperature (below scorch). (2) Warming up cold rubber for feeding to extruders or calenders. (3) Sheeting — producing uniform-thickness sheets by adjusting the nip. (4) Lab mixing — small-scale compounding per ASTM D3182 using lab mills (150×300 mm or 200×400 mm). (5) Blending — homogenizing compound after internal mixer dump. Operator skill is important: ingredient addition sequence, banding technique, and temperature control determine compound quality. Safety: nip guards (trip bars, body bars) per OSHA 1910.216 are mandatory — the nip point is extremely hazardous. Temperature control: water circulation through hollow rolls. Brands: Farrel, Berstorff, Buzuluk, Comerio Ercole. Per standard rubber processing practice.