The mill blender, an accessorythat mounts on top of a mixing mill, has a threefold purpose:
- Blending, by pulling rubber off the front face of a mill roll and diverting it back into the rolling blank before the bite or gap between the two mill rolls.
- Guiding, to assist the mill operator in manipulating the rubber to a particular position as it is removed from the mill.
- Circulating, achieved by moving rubber off and then back on the mill. Circulation reduces time and temperature exposure that contribute to scorching and scrap product.
While mill blender purpose has remained somewhat static, over the last twenty years a steady evolution has taken place in mill blender design, driven by demands of the rubber industry that focus on the “four Cs”: Clean, Consistent, Controllable, Compact.
Akron Steel Fabricators (ASF), a Poling Group company, has positioned itself as a leader throughout this evolution with innovation that focuses on the same goals.
The potential for batch contamination remains a major problem for many legacy mill blenders with a Yankee screw, traditionally chosen because of its consistent and controllable traversing speeds. However, because the Yankee screw requires constant lubrication and traverses across the face of the mill, the inherent design results in a high potential for grease to drip into the batch. Also, its open exposure increases the probability of lubricant mixing with airborne particulates, further contaminating the rubber.
ASF solved the batch contamination problem by reinventing the mill blender with a contained ball screw that also provides consistent speed control. By housing the ball screw shaft and nut within an enclosed tube, ASF isolated it from any contamination from the mill, and at the same time eliminated the potential for the mill blender to introduce lubrication and other contaminates into the milled product. The metal tube enclosing the ball screw also functions as a bearing surface for the reciprocating carriage.