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3 Rollers Plate Bending Machine User Guide

3 rollers plate bending machine is very common equipment in metal sheet forming, mainly used to roll flat plates into cylindrical, arc, and conical shapes. They are widely used in industries such as pressure vessels, wind turbine towers, chimneys, pipelines, ventilation equipment, steel structures, and machinery manufacturing. Their core value lies not merely in “rolling up the plate,” but in efficiently and stably completing the forming process while ensuring roundness, straightness, end-to-end precision, and surface quality.

This guide provides a systematic explanation from several aspects, including equipment recognition, pre-start inspection, actual operation, process control, handling different materials, maintenance, troubleshooting, and safety precautions.

1. Equipment Overview

The 3 rollers plate bending machine is a key piece of equipment used to roll metal sheets into cylindrical, arc-shaped, or conical work pieces.

It is widely used in:

Steel structures (cylinders, pipes)
Pressure vessels
Wind turbine towers
Shipbuilding
Petrochemical equipment

Common types:

Symmetrical (three-roll symmetrical)
Asymmetrical (three-roll asymmetrical)
Upper roll universal type (most common)

2. Working Principle Of 3 Rollers Plate Bending Machine

Core Principle: Three Points Form a Circle
Upper Roller: Driven Roller (Rotating)
Lower Roller/Side Rollers: Adjust position to form the bending radius

The sheet metal undergoes continuous plastic deformation under the force of the three rollers, gradually forming an arc.

The three rollers plate bending machine applies continuous bending force to the sheet metal through the roller shafts, causing the sheet metal to gradually undergo plastic deformation. As the sheet metal repeatedly passes between the roller shafts, the outer fibers are stretched and the inner fibers are compressed, ultimately forming the desired curvature.

Depending on the structure, three-roll plate bending machines commonly come in three forms:

1) Symmetrical Three Roll Plate Bending Machine

The upper roller is in the middle, and the lower rollers are on both sides.
Simple structure, relatively low price.
Suitable for general cylindrical rolling.
Weak end pre-bending capacity, often requiring flanging.

2) Asymmetrical 3 Rollers Plate Bending Machine

The upper and lower roller positions are not completely symmetrical.
Generally has better pre-bending effect.
Suitable for applications requiring higher forming precision.

3) Fully Hydraulic Or CNC Three Roll Plate Bending Machine

More stable operation and more precise control.
It can achieve programmed adjustment, parameter memory, and automatic positioning.
More suitable for batch and precision production.

3. Three-Roll Plate Bending Equipment Structure

1) Mechanical System

Upper Roller: Main Drive
Lower Roller: Support
Side Rollers: Curvature Adjustment
Tilting Frame: Unloading
Frame: Overall Load Bearing

2) Hydraulic System

Hydraulic Cylinder: Drives Side Rollers/Lower Rollers
Hydraulic Pump Station
Pressure Control Valve

3) Electrical Control System

PLC / CNC System
Operation Panel: Manual/Automatic
Encoder: Position Detection

4. Essential Knowledge Before Use

Before formal operation, operators must be clear about at least the following:

1) Sheet Metal Parameters

Must confirm:

Material type: carbon steel, stainless steel, aluminum plate, galvanized sheet, etc.
Sheet thickness
Sheet width
Sheet length
Material yield strength
Whether annealed, whether surface coated
Whether tapered, elliptical, or other special shapes are required

2) Equipment Rated Capacity

Don’t just look at the “maximum thickness,” also consider:

Maximum rolling capacity under what material strength
Maximum rolling capacity for what sheet width
Minimum rollable diameter
Whether cold rolling is allowed
Suitable for pre-bent ends

Many users encounter problems not because the equipment is broken, but because it is used beyond specifications.

For example:
The rolling difficulty of Q235 steel plate and high-strength steel is completely different for the same 10mm steel plate. Stainless steel has a more pronounced spring back than ordinary carbon steel. Although aluminum plate is soft, it is prone to surface scratches.

3) Forming Requirements

The following must be clarified before starting the machine:

What is the diameter of the finished product?
Is it a full circle or a partial arc?
Do the two ends need to be butt-welded?
Is high roundness required?
Is a small amount of elliptical error permissible?
Is taper required?

5. Pre-Power-On Checklist

This step is crucial. Many equipment malfunctions and safety incidents are caused by inadequate pre-power-on checks.

1) Mechanical System Inspection

Inspect the surface of each roller for obvious indentations, cracks, weld slag, and burrs.
Check if the roller shaft rotates freely and without jamming.
Check if the frame and anchor bolts are loose.
Check if all fastening bolts are secure.
Check if the guide rails, sliders, lead screws, and lifting mechanism are well lubricated.

2) Hydraulic System Inspection

Check if the hydraulic oil level is normal.
Check if the oil color is black, emulsified, or contains impurities.
Check for leaks in hydraulic lines, joints, and cylinders.
Check for abnormal noise from the oil pump.
Check if the pressure is stable.
Check if the oil temperature is within a reasonable range.

3) Electrical System Inspection

Check if the power supply voltage is stable.
Check if the emergency stop button is effective.
Check if the forward/reverse rotation, lifting, and adjustment actions are normal.
Check if there is dust, moisture, or burn marks inside the control cabinet.
Check if all limit switches and sensors are functioning properly.

4) Safety Device Inspection

Check if the emergency stop is sensitive.
Check if the protective cover is intact.
Check if the foot switch is reliable.
Check if the two-hand buttons are usable.
Check for foreign objects near the upper and lower rollers.
Check if the working area is clean.

6. Operating Procedures (Standard Steps)

Below is a generally accepted operating sequence for plate rolling. Different models of equipment may have slight variations in the sequence, but the basic logic remains the same.

Step 1: Start the Equipment

Connect the main power supply.
Check if the control system is powered on normally.

Perform jogging operations under no-load to confirm:

Upper roller lifting and lowering are normal.
Side roller adjustment is normal.
Lower roller rotation is normal.
Forward and reverse rotation are normal.
Emergency stop is effective.

Step 2: Select the Appropriate Roller Positions

Adjust the positions of the upper and lower rollers according to the plate thickness and target diameter.

The principles are:

The thicker the plate, the larger the initial opening usually needs to be.
The smaller the target diameter, the greater the bending amount.
When pre-bending is required, the roller position and plate end position must be properly matched.

The positioning methods differ between symmetrical and asymmetrical equipment. Follow the equipment instructions.

Step 3: Material Placement and Positioning

Place the sheet material smoothly into the equipment.
Ensure the edges of the sheet material are parallel to the rollers.
Align the center line of the sheet material with the center line of the equipment.
If a guide device is used, adjust its position first.
Prevent the sheet material from entering at an angle, avoiding “deviation” or “skewed rolling.”

Step 4: Pre-bending Before Rolling

This is a crucial step. Because when rolling the sheet material, the ends often don’t roll naturally to the correct position, leaving “straight edges.” Therefore, it’s usually necessary to pre-bend the front and rear ends first.

Pre-bending points:

First, press the sheet end with an appropriate bending amount.
Minimize straight edges at the sheet end.
The pre-bending depth should match the target diameter.
The pre-bending at both ends should be as consistent as possible. Otherwise, the finished product will have misaligned edges or an elliptical shape.

Step 5: Formal Rolling

Start the roller rotation.
Slowly press down or adjust the side rollers.
Observe the sheet material’s rolling state.
If necessary, roll back and forth multiple times.
Gradually approach the target radius, rather than pressing it to the correct position in one go.

Step 6: Correction and Rounding

After rolling to near the target size, fine-tuning is required:
Check if the diameter meets requirements
Check if the interface gap is uniform
Check if the roundness is consistent
Check if the plate edges are misaligned
Perform secondary rounding if necessary

Step 7: Unloading

Confirm the rollers have stopped.
Release the pressure.
Remove the workpiece using hoisting or manual assistance.
Large workpieces must be lifted using appropriate lifting equipment or support frames.
It is strictly forbidden to reach into the roller gap to forcibly remove the material.

7. Core Operating Techniques of a Three-Roll Plate Rolling Machine

The key to using the 3 roller plate bending machine effectively lies in process control, not simply “being able to roll it up.”

1) Controlling Pre-Bending

Insufficient pre-bending will leave obvious straight edges.
Excessive pre-bending will lead to localized deformation, difficulty in forming a round shape, and even wavy edges.
Experience-wise, a comprehensive judgment should be made based on material thickness, yield strength, roll diameter, and equipment structure.

For most operating conditions, pre-bending should achieve the following:

Shortest straight edges at both ends
Symmetrical curvature at both ends
Consistent and stable pre-bending amount

2) Controlling the Feed Angle

When the sheet enters the roller conveyor, it should be kept:

Parallel to the roller axis
Aligned with the center line
No warping of the sheet surface
No skewing of the sheet edges

If the feed angle is incorrect, the finished product often exhibits:

Taper deviation
Tight on one side and loose on the other
Twisted cylinder
Uneven joints

3) Form in stages, avoid rapid pressing

Many beginners like to press a lot at once, which easily leads to:

Local over-bending
Wrinkling of the sheet surface
Scratching of the material surface
Increased ovality of the cylinder

The correct method is:

First, press lightly and observe the bending trend
Gradually deepen the bending
Check the results after each adjustment
Using the “multiple small amounts” method is more reliable

4) Pay attention to springback

Different materials have different springbacks
Carbon steel has relatively small springback
Stainless steel has larger springback
High-strength steel has more obvious springback
Aluminum alloys have significantly different springbacks due to different material properties

Therefore, when rolling to the target diameter, one cannot only look at the instantaneous size. The springback after pressure release must also be considered, and over-winding compensation may be necessary.

5) Controlling Surface Quality

If high surface finish is required, pay attention to:

Whether the roller surface is clean?
Whether there is welding slag or iron filings?
Whether there are hard particles trapped between the sheet and the roller surface?
Whether there are traces of material clamping?

For stainless steel or aluminum sheets, it is best to avoid hard contact and scratches from dirt.

Therefore, when rolling to the target diameter, do not only look at the instantaneous size, but also consider the springback after pressure release. Over-rolling compensation may be necessary.

6) Control surface quality

If high surface finish is required, pay attention to:

Whether the roller surface is clean?
Whether there is welding slag or iron filings?
Whether there are hard particles trapped between the sheet and the roller surface?
Whether there are traces of material clamping?
For stainless steel or aluminum sheets, it is best to avoid hard contact and scratches from dirt.

8. Key Points for Rolling Different Materials

1) Carbon Steel Plate

Characteristics:

Good plasticity.
Suitable for most conventional rolling processes.
Low springback, mature technology.

Precautions:

Pay attention to equipment tonnage for thick plates.
Oxide scale on edges can easily affect the surface.
Pay attention to stress release in welded structural plates.

2) Stainless Steel Sheet

Features:

High springback
Surface easily scratched
Requires higher forming precision

Precautions:

Roller surface must be clean.
Avoid hard particles pressing into the surface.
Pre-bending and compensation should be more accurate.
Prevent pinching and scratching of the surface during unloading.

3) Aluminum Sheet

Features:

Softer material.
Prone to surface indentation.
Easily damaged by excessive pressure.
Requires high roller surface quality.

Precautions:

Roller surface must be burr-free.
Clamping force should not be excessive.
Avoid repeated pressing.
Take care to protect with soft packaging during transportation and hoisting.

4) High-Strength Steel

Features:

High yield strength.
Requires greater forming force.
Significant springback.
Easily increases equipment load.

Precautions:

Strictly prohibit exceeding specifications.
Equipment rated capacity must be checked.
The rolling process should be smoother and slower.
The hydraulic and drive systems of the equipment bear a greater load, requiring close monitoring of temperature rise and pressure.

9. Key Points For Conical, Arc And Special Work piece Operations

1) Conical Rolling

Conical rolling is more complex than circular rolling because the circumferences at both ends are different, requiring the sheet metal to form a taper.

Key Points:

The sheet metal feed angle must be offset according to the taper requirements.
The feed amounts on both sides of the sheet metal must be different.
A conical rolling device or special tooling is required.
The dimensions of the large and small ends must be confirmed first.
The longer the cone and the smaller the cone angle, the more critical the control.

2) Arc Rolling

If only a partial arc is needed, rather than a full circle:

Set the target bending radius.
Control the roll-in length.
Form in segments multiple times.
Maintain uniform arc length.

3) Large Diameter Thin Sheets

Thin sheets with large diameters are prone to:

Wrinkling
Wavy edges
Instability
Uneven forming

Solutions:

Reduce the single bending amount
Increase material support
Control the flatness of the sheet surface
Use a gentler, multi-stage rolling method

10. Common Problems and Solutions

1) Excessively Large Straight Edges at Both Ends

Cause:

Insufficient Pre-bending

Solution:

Increase Pre-bending Amount
Use “Secondary Pre-bending”

2) Uneven Circumference, Large Ovality

Cause:

Uneven Roller Position Adjustment
Improper Sheet Feed
Uneven Stress on Both Sides
Insufficient Rolling Times
Large Difference in Material Springback

Solution:

Correct Left-Right Balance of Equipment
Adjust Centerline
Add Rounding Process
Compensate for Over-Rolling of Material

3) Sheet Material Deviation

Cause:

Sheet Material Not Aligned
Roller Parallelism Error
Guide Device Not Adjusted
Sheet Edge Not Straight

Solution:

Realign
Check Guide
Correct Roller Parallelism
Trim Sheet Edge

4) Conical Shape

Cause:

Sheet Material Not Aligned

Solution :

Realign
Adjust side roller pressure difference

5) Surface scratches

Causes:

Foreign objects on the roller surface
Roller surface wear or scratches
Particles embedded in the sheet surface
Excessive clamping

Solutions:

Clean the roller surface
Grind or repair the roller surface
Strengthen protection for materials with high surface requirements
Reduce unnecessary contact pressure

6) Sheet slippage

Causes:

Insufficient pressure
Surface oil contamination

Solutions:

Increase clamping force
Clean the sheet

7) Slow or weak hydraulic action

Causes:

Insufficient hydraulic oil
Pump wear
Abnormal system pressure
Oil circuit blockage
Oil temperature too high

Solutions:

Check oil level
Replace filter element
Check pump and valve
Clean oil circuit
Control continuous high load operation time

11. Maintenance Guide (Key Points)

1) Daily Maintenance

Clean roller surface
Inspect oil circuit
Inspect fasteners
Lubricate guide rails

2) Hydraulic System

Change hydraulic oil every 2000 hours
Clean filter element regularly
Check for oil leaks

3) Mechanical Components

Inspect roller wear
Inspect bearing temperature
Correct roller parallelism

4) Electrical System

Inspect wiring
Back up PLC parameters
Calibrate encoder

12. Daily Maintenance

Maintenance is crucial for the long-term stable operation of a 3-rollers plate bending machine.

1) Daily Maintenance

Clean the equipment surface, roller surfaces, and working area.
Check for oil leaks, electrical leaks, and loose parts.
Remove plate chips, iron filings, and welding slag.
Check the lubrication points for proper functioning.
Run the 3 rollers plate bending machine under no-load to confirm smooth operation.

2) Weekly Maintenance

Check fasteners.
Check the lubrication of rollers, guide rails, chains, or gears.
Check hydraulic lines and joints.
Observe oil temperature and noise changes.
Verify the smoothness of major movements.

3) Monthly Maintenance

Check the hydraulic oil contamination level.
Check the filter element condition.
Check electrical wiring terminals.
Check limit switches and sensors.
Check the equipment level and foundation condition.

4) Regular Major Maintenance

Change the hydraulic oil.
Change the filter element.
Check bearing wear.
Check roller surface accuracy.
Check reducer oil.
Perform accuracy calibration if necessary.

13. Lubrication Requirements

Lubrication is one of the key factors for the long-term stable operation of the 3 rollers plate bending machine.

Lubrication Points:

Roller Bearings
Guide Rails
Lead Screws
Gears
Chains
Lifting Mechanism
Other Mechanical Connections

Lubrication Principles:

Use the oil and lubrication cycle specified in the instruction manual.
Do not mix unsuitable greases for different parts.
Appropriate lubrication amount; excessive lubrication can attract dust.
Increase the frequency of inspections under high temperature and high load environments.

14. Safe Operating Procedures

The three-roll plate rolling machine is a heavy-duty forming equipment; safety must be the top priority.

Principles to be followed:

Operators must be trained.
Do not wear loose clothing, scarves, or gloves near rotating parts.
Do not put hands into the roller gaps.
Ensure the equipment is completely stopped before unloading.
Large workpieces must be hoisted.
Immediately stop the 3rollers plate bending machine if abnormal noise, vibration, oil leakage, or odor is detected.
Power must be disconnected, pressure released, and a warning sign posted before any maintenance.

Special Note:

When the equipment is running, no one must stand on the side where the workpiece might tip over.
When rolling large-diameter workpieces, prevent the workpiece from rolling and causing injury.
Sufficient support must be provided when rolling conical shapes and extra-long plates.
Any overloading may cause damage to the rollers, cylinders, and reducers.