The rolling forces require main bearings with very high load carrying capacity. The high rolling forces are securely supported by double row cylindrical roller bearings. The bearings run true as a result of high bearing precision. The operating temperature of 200 ˚C requires a special manufacturing process.

• The bearing inner rings and roll bodies are finish ground in a single clamping step at a roll surface temperature of 220 ˚C. This process allows a runout accuracy of ≤ 5 μm.

The high rolling forces cause flexing of the rolls, leading to tilting in the bearings. Hydraulic cylinders at both ends of the rolls generate appropriate counterbending of rolls 2 and 4 by means of a roll bending force.

• The hydraulic cylinder forces are transmitted to the roll journals by means of spherical roller bearings, compensating for the tilting and allowing low-friction running.

Roll 3 supports forces, generated by rolls 2 and 4, in a positive and negative direction. The reversal of the forces allows a zero-load condition to repeatedly occur. Additional preload bearings prevent uncontrolled radial movement in the zero-load condition.