2 key points for choosing the right 3-roll plate rolling machine

  • Jack Lu 

With the advent of 4-high bending machines, beginners may wonder if there is any reason to consider purchasing a classic 3-high machine that costs significantly less than a 4-high bending machine of similar capacity many.

In the world of previously owned rolling machines, an added benefit for the frugal shopper immediately became apparent – there are far more three-roll plate rolling machines than four-roll machines on the market, some dating back a few days. Ten years ago. Refurbishing a used 3-roll coil is also easier because there are fewer moving parts.

When it comes to light-duty manufacturing jobs, a 4-roll plate bender will also be overkill in most cases. The four-roll bending machine was developed with high production runs on thick materials in mind. The three-roll bending machine will become the standard for sheet metal processing for a long time.

5 Types of Three Roll Plate Rolling Machines

When purchasing a three-roll rolling machine, manufacturers must understand that they have different roll configurations:

Pyramid plate bending machine

Take the name “pyramid” from the shape the rolls form, with one roll on top and two lower rolls on either side. This is considered a symmetrical roll because the front and rear of the roll appear to be the same when viewed from the end of the roll. While the top roll can move up and down, both bottom rolls are held in place, so a true pyramid plate rolling machine cannot pre-bend the workpiece, leaving long flat areas on both ends of the board. In recent decades, more modern pyramid rolling machines with movable bottom rolls have been developed, which is why these originals are called “true pyramid rolling machines”. Few of these machines are made today, but they can be found on the used market.

Initial Pinch Plate Rolling Machine

This form of three-roll rolling mill is generally used for rolling lighter gauge materials. When manufacturers talk about “slip rollers,” they usually think of this type of machine. Often referred to simply as an “IP roll”, this machine is a classic example of an asymmetrical plate rolling machine, as the front of the machine has two rolls, one on top of the other, while the back of the machine has only one roll. The “Initial Clamp” name comes from the front rollers that clamp or clamp the material when it is initially loaded into the machine. The subsequent offset forming rolls adjust their position relative to the other two rolls to form the desired radius, although the metal usually needs to pass through the rolls multiple times to create the shape. The material can be loaded horizontally—instead of tilted, which is awkward to do—the initial pinch rolls are able to pre-bend the workpiece to eliminate most of the flat spots, although it does require removing and reloading the sheet to pre-bend the ends. While a large number of initial pinch roll benders on the market are driven by electromechanical motors, hydraulic drive models can be used for thicker boards, and hand crank models can be used for thinner materials. This type of rolling machine is also referred to as a single initial pinch roll to distinguish it from a double pinch roll. Hydraulic-powered models are available for thicker boards and hand cranked models are available for thin gauge materials. This type of roll is also referred to as a single initial pinch roll to distinguish it from a double pinch roll. Hydraulic-powered models are available for thicker boards and hand cranked models are available for thin gauge materials. This type of roll is also referred to as a single initial pinch roll to distinguish it from a double pinch roll.

Double pinch plate rolling machine

This type of three-roll flat roll is also referred to by the seemingly contradictory terms as a double-clamp cone roll (because of the configuration of one upper and two lower rolls) and a dual initial clamp roll (because the material can be rolled from either side load and “squeeze”). However, unlike a true Pyramid Roller, the upper roll of the Double Pinch Roller remains stationary while the two lower rolls move up and down. Depending on the model, the movement of the lower roller is either a linear motion towards the upper roller (straight plate roller) or a curved curve (planetary plate roller). The double clamp design allows both ends of the workpiece to be pre-bent without removing it from the machine, which is a huge advantage.

All three configurations can also be used as a vertical format plate rolling machine, extending upwards, allowing the production of large diameters, such as tanks.

Variable Geometry Plate Rolling Machines

4 roll bending machine
4 roll bending machine

There is one more important three-roll configuration to consider, namely the variable geometry plate rolling machine.

Often purchased for heavier jobs involving thick plates, these unique coils have two lower rolls that move horizontally relative to a vertically moving upper roll, varying their offset distance. This adjustable roll geometry gives these machines distinct advantages over conventional three-roll plate rolling machines:

  • Just like using a wider V-die with a press brake, the smaller the tonnage required to roll the material, the greater the distance between the bottom rolls. This allows heavier materials to be rolled on these machines, giving users 50% more rolling capacity than comparable three-roll or even 4-roll plate rolling machines.
  • If the side rolls are close to the top rolls, smaller diameters can be rolled with thinner material.
  • Material can be loaded parallel to the ground – rather than inclined, as required by the double clamp – making material handling safer and easier.
  • All rolls are driven on standard variable geometry sheet rolls, providing better control of the bending process compared to sheet rolls using unpowered idle rolls.
  • Deformation is better handled with one of these machines because changing the geometry of the lower roll changes the pressure on the upper roll, eliminating the need for the operator to shim or perform other crown compensation.
  • Standard variable geometry machines allow their rolls to move at an angle, creating an ideal configuration for conical rolling.
  • Due to the enormous pressure the rollers can exert, some customers have actually purchased variable geometry plate rolling machines, mainly used as pressure rollers for straightening plates.
  • Variable geometry plate rolling machines, while not cheap, are very versatile and can perform a variety of functions on a variety of metal thicknesses.

Top roll variable geometry plate rolls prt

High rolling power combined with maximum pre-bending precision: PBRT is the series of top roll horizontally and vertically movement variable geometry 3-roll bending machines at the highest level of its category by performance and versatility.

PRT 3-roll bending machines designed, manufactured and marketed by BIT deliver performance equivalent to that obtained with the more expensive 4-roll plate bending rolls and are therefore ideal for medium-heavy duty machining.

  • Bending Thickness: 50-200mm
  • Pre-bending Thickness: 40-160mm
  • Bending Width: 1000-10000mm

Works cited: “PLATE ROLLING MACHINE”, Angle roller, 20 Aug, https://www.angleroller.com/plate-bending-machine.html

Precautions for purchasing a three-roll plate rolling machine

In addition to the roll configuration, there are other factors to consider when purchasing a three-roll rolling machine, namely:

  • What is your longest workpiece length?
  • What is the thickest workpiece you need to roll? (what material?)
  • What is the thickest material you need to pre-bend due to the need for more pressure?
  • What is the thinnest material you need to roll?
  • What is the tightest diameter you need in a finished part?
  • What facilities are there for extracting artifacts? (drop yoke, etc.)
  • Do you want hardened rolls for greater durability? (A very good idea.)
  • Do you need to grind rollers to avoid damage to the workpiece?
  • Do you need reel equipment to assist with the process?
  • Do you need side or overhead support to handle larger diameters?
  • Does your production need to be automated?
  • Does the machine have a portable control panel that the operator can reposition?
  • Do you want NC or CNC control? (If so, you really need a four-roller machine.)
  • What safety devices does the machine have?
  • Are your operators trained and proficient with the relevant machines?

Another factor to consider when equipping your workshop with a metal plate bending machine: Unlike a press brake, which can bend anything down from maximum capacity, the tool on a bending machine is the roll itself, depending on the tool used, usually cannot be changed to accommodate smaller diameters. This is why many shops will have more than one roll on the floor to use different thicknesses and diameters. Depending on your situation, you may want to weigh the option of buying two rolling machines rather than looking for a one-size-fits-all machine.