Four Roll Plate Rolling Process: A Step-by-Step Guide to High-Precision Plate Forming
Four Roll Plate Rolling Process: A Step-by-Step Guide to High-Precision Plate Forming
Posted by PLSON Engineering Team
Introduction
The four roll plate rolling process is a high-precision and efficient metal plate forming method used in shipbuilding, pressure-vessel manufacturing, petrochemical equipment, bridge construction, mechanical manufacturing, and other industrial applications.
A four roll plate rolling machine uses the coordinated movement of the upper roll, lower roll, left side roll, and right side roll to align, clamp, pre-bend, roll, and close the plate into a cylindrical workpiece. Understanding the correct sequence is important for forming quality, process stability, and operator safety.
This guide explains a representative four-roll rolling sequence using the following reference marks:
- A roll: the first side roll used in the alignment and forming sequence
- B roll: the second side roll used for pre-bending and closing
- D roll: the lower roll reference used during the final forming stages
- T: the plate being processed
Important safety and technical note: The roll names, movement directions, clearances, positions, and numerical settings in this guide are process examples based on the supplied workflow. They may differ according to machine design, control system, plate material, thickness, width, diameter, and manufacturer’s instructions. Operators must use the approved machine manual, setup sheet, guards, emergency-stop procedures, and qualified training. Never place hands or body parts near moving rolls.
1. Plate Alignment and Feeding
First, raise the side roll A to the required setup position. In the representative arrangement, the horizontal centerline of side roll A is positioned within the opening height between the upper and lower rolls.
Feed plate T into the opening between the upper and lower rolls. Align the plate with side roll A and confirm that the plate edge is positioned correctly across the working width.
Raise the lower roll to clamp the plate securely. Check the plate position, alignment, and clamping condition before continuing. Once these checks are complete, the alignment and feeding stage is finished.
2. Initial Pre-Bending
After plate alignment is complete, lower side roll A to its zero or approved reference position. Move plate T backward until it is approximately 2–5 mm from the vertical centerline of the upper and lower rolls, according to the supplied process example.
This small allowance is intended to reduce the risk of plate slippage during setup. The actual clearance must be confirmed from the machine’s approved operating procedure because an incorrect position can affect both forming quality and safety.
Next, raise side roll B to the calculated or programmed position to perform the initial end pre-bending operation. Then move plate T forward by approximately 150–250 mm to complete the initial pre-bending step, if these values are suitable for the specific machine and workpiece.
3. Main Rolling and Arc Correction
After the initial pre-bending operation, lower side roll B and move plate T forward. Raise side roll A according to the calculated setup value.
During this stage, use a template or approved measuring method to check the developing arc. If the arc is too large, raise side roll A further within the permitted adjustment range. If the arc is too small, lower side roll A as required.
Continue the rolling passes while monitoring plate alignment, roll position, surface condition, and machine load. When the trailing end of plate T reaches the centerline of side roll B, stop the main rolling operation and prepare for the final end pre-bending stage.
4. Final End Pre-Bending
Raise side roll A and continue rolling until the trailing end of plate T reaches the vertical centerline of lower roll D. Stop at the approved position to complete the final end pre-bending operation.
The required roll position depends on the plate material, thickness, width, target diameter, machine geometry, and forming method. Use the calculated or programmed value supplied for the specific job rather than relying on a generic setting.
5. Closing the Cylinder and Final Forming
To begin the closing operation, move plate T backward by approximately 80–120 mm, based on the supplied process example. Lower side roll A to its calculated position and raise side roll B to its calculated position.
Reverse the upper and lower roll drive to move plate T backward until it reaches the centerline of side roll A. Stop the movement and raise side roll B slightly to apply the specified closing pressure or head-forming allowance. The exact value should be set by the approved process sheet or operator procedure.
Move plate T backward until it reaches the vertical centerline of lower roll D. Then move the plate forward by approximately 80–120 mm and stop.
Lower side roll B to the calculated position. Move plate T forward through approximately 30%–50% of the plate circumference to complete the cylinder closing operation and finish the rolling process.
6. Process Checks Before Removing the Workpiece
Before releasing the finished workpiece, confirm:
- The target inside diameter or radius
- Cylinder roundness and visible straightness
- Weld-joint or closing alignment, if applicable
- Remaining straight-end length
- Surface condition and absence of abnormal marks
- Machine pressure, roll position, and alarm status
- Safe release and removal procedure
If the workpiece does not meet the drawing or process requirements, do not make unapproved adjustments. Stop the machine when necessary and consult the responsible engineer or equipment supplier.
7. Why the Four-Roll Sequence Matters
A controlled sequence helps coordinate clamping, plate movement, pre-bending, arc formation, end correction, and closing. Skipping a step or using an incorrect roll position can lead to:
- Plate slippage
- Excessive straight-end length
- Inaccurate diameter
- Poor cylinder roundness
- Surface damage
- Uneven forming or edge deformation
- Increased risk during operation
For repeat production, store approved setup values and forming programs only after they have been verified for the actual material and workpiece.
Conclusion
The representative four roll plate rolling process includes five main stages: plate alignment, initial pre-bending, main rolling, final end pre-bending, and cylinder closing. The A, B, and D roll reference positions, as well as the forward and backward movement of plate T, must be coordinated carefully throughout the operation.
The distances and percentages described in this article are process examples from the supplied workflow, not universal settings for every four roll plate rolling machine. Final values should be determined from the machine design, material data, workpiece drawing, forming calculation, and manufacturer’s operating instructions.
With correct setup, controlled roll movement, accurate arc inspection, and proper safety procedures, a four roll plate rolling machine can support stable and efficient cylindrical plate forming.
Need help selecting or setting up a four roll plate rolling machine? Contact PLSON with your material, plate thickness, working width, target diameter, and workpiece requirements.
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📧 Eric@plsonmachine.com
🏭 Haian Industry Park, Jiangsu Province, China