Rectilinear Guides (Bertsch Design)

Built for rolling heavy plate

Concept

The Rectilinear Guide concept consists of forming rolls that are guided in place by a machined surface, and bearing blocks mounted directly above the hydraulic cylinder. The position of the rolls is controlled by the hydraulic cylinder with no additional moving parts.

Advantages

Bertsch’s Rectilinear Guide system transmits the forming roll forces directly to the hydraulic cylinder, into the machine frame, and into the foundation. There are no load-bearing wear points or torsional stresses affecting roll parallelism and accuracy. This leads to a long service life, consistent parts, and low maintenance. The centerline of the forming roll is close to that of the pinch roll. This allows the flat areas associated with pre-bending to be small and consistent. In addition, Bertsch sizes the direct-acting hydraulic cylinders to pre-bend to the maximum rolling capacity of each machine.

Each side of every forming roll is individually controlled, allowing fine roll adjustments, making cone rolling easy to set up. There are no torque tube stresses to account for.

Disadvantages

Rectilinear Guides are more expensive to produce because they require additional machining, and the hydraulic cylinders have a larger diameter.

Planetary Swing Guides (Competitor’s Design)

Inexpensive, but less robust solution

Concept

The Planetary Swing Guide concept consists of the forming rolls mounted to a lever arm. The hydraulic cylinders are mounted so that a mechanical advantage is formed allowing use of a smaller diameter, and less expensive cylinder. The rolls move along an arc, and are cam guided. A torque tube is mounted between the hinge end and gear end of the machine, and attached to the levers in order to maintain parallelism of the rolls.

Advantages

This concept requires smaller cylinders and less machining than the rectilinear guides, and therefore costs less.

Disadvantages

  1. Each side of every forming roll requires a minimum of four pivot points (see diagram). These pivot points consist of a pin and a bearing. The entire bending load of the machine is translated through these pins and bearings resulting in faster wear. This wear creates loss of parallelism and therefore difficulty in maintaining consistency from part to part.

  2. The centerline of the pinch and forming rolls are larger than on rectilinear machines. As a result, the flat associated with pre-bending is larger, creating more part inconsistencies.

  3. The amount of mechanical advantage becomes limited as the forming cylinder rises for pre-bending. The cylinders are typically not sized to handle this additional force, therefore the machines are not capable of pre-bending the material to its nominal rolling capacity.

  4. The torque tube is sized in order to allow some twist for the purpose of cone rolling. The torque tube is not capable of keeping the rolls parallel.

  5. The torque tube creates twisting stresses in the lever and machine frame.

Variable Geometry Rolls (Competitor’s Design)

Low cost, but limited capability

Concept

The Variable Geometry Roll concept uses only three rolls, and allows the bottom rolls to be adjusted from side to side.

Advantages

Less expensive solution by offering three rolls instead of four.

Disadvantages

  1. Pre-bend capacities are typically limited—to as much as 50 percent of rolling capacity.

  2. The rated rolling capacity can only be achieved by spreading out the lower two rolls, creating excessive flats—7 to 10 inches depending on the size of the machine.

  3. Machines are typically only driven by the top roll. Thin material can slip when rolled to large diameters.

Key Advantages | Features | Options | Control Options | Specifications

Process Comparison | Rectilinear Guides | Custom Rolls | Applications