Plate Bending Rolls and Slip Roll machines are used for forming cylindrical shapes from sheet metal and steel plate. Many commonly used products such as tanks and other curved metal items are formed on new and used bending rollers. Various designs and configurations have been employed to form metal on bending rolls. Over time, metal plate bending machines have evolved from exclusive pyramid and initial type to include various 3-roll and 4-roll designs. Modern metal bending rolls can be both hydraulically and mechanically driven—whereas they were only mechanically driven in the past.
The most common 3 Roll Bending machine and Slip Roll types are:
Also known as single pinch rolling machines. Two of the three rolls are positioned with one of the rolls exactly above the other (referred to as the top and bottom rolls). The top and bottom rolls pinch the material, moving the material as they turn. The material is bent as it comes into contact with a third roll (the rear roll). The position of the rear roll can be adjusted (up or down) to alter the curvature of the material. The bottom roll can also be adjusted to accommodate the thickness of the material. Both bottom and rear rolls can have manual or powered adjustments.
Historically, the description generally refers to mechanical 3-roll bending machines that have become largely obsolete. Pyramid type bending rolls have two powered lower rolls. Centered above the two bottom rolls, the top roll is adjustable up and down. The pyramid roll design is not ideal for thin gauge material or when a leading edge flat spot is problematic. Pyramid rolls, however, do have some advantages. Because of its wide vertical opening between the top roll and the two lower rolls, heavy structural materials such as small i-beams or heavy rod can be bent.
Although also technically pyramid-shaped, the more modern Hydraulic Double Pinch 3-Roll Bending Machine is frequently used today. Double pinch bending rolls have great universality because while the top roll is fixed, both bottom rolls are adjustable. They have the ability to pre-bend both ends of the plate. These features yield less handling and make the Double Pinch 3-Roll bender efficient, desirable, and cost-effective.
4-Roll Bending machines are hydraulically driven. They have all the benefits of Double Pinch 3-Roll benders with the added feature of having a fourth roll. The top and bottom rolls work together to do all the pinching, allowing the third and fourth rolls to do all the bending. Tighter diameters can be achieved as the third and fourth rolls bend materials independently form one another. Greater bending control and flexibility yields more accurate bending and ease of use. 4-Roll Hydraulic Bending Rolls are the most desirable and most expensive plate bending roll options on the market today.
Urethane rolls are 2-roll benders that are ideal when it is necessary to form metal without scratching or marring the surface.
Plate bending rolls are frequently equipped with one of the following:
The drop end feature allows for the end support of the top roll to be dropped away allowing for the removal of tightly formed tanks and cylinders. Frequently, a balance beam mechanism is designed into the machine which slightly lifts the top roll in order for the pinched material to be removed.
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