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Hydraulic Plate Bending Rollers Operation Instructions And User Manual

Hydraulic plate bending rollers are essential equipment in metal sheet forming and processing. They primarily utilize the relative position and rotational movement of the upper, lower, and side rollers to continuously bend metal sheets such as steel, stainless steel, and aluminum, gradually shaping flat sheets into cylindrical, arc-shaped, conical, and other curved workpieces.

Different structures of hydraulic plate rolling machines have different operating methods, especially three-roll, four-roll, symmetrical, asymmetrical, and CNC hydraulic plate bending machines, whose roller movements and control methods are not entirely the same. Therefore, the following content is based on common hydraulic three-roll/four-roll plate rolling machines.

Actual operation must be based on the instruction manual, hydraulic schematic diagram, and electrical drawings provided by the equipment manufacturer. Four-roll machines typically consist of an upper roller, a lower roller, and left and right side rollers. The lower and side rollers are raised and lowered by hydraulic cylinders, and the control system is responsible for the actions of each mechanism.

1. Basic Structure Of Hydraulic Plate Bending Rollers

A typical hydraulic plate rolling machine mainly includes the following systems:

System	Main Components	Main functions
Frame system	Left and right frames, base, connecting beams	Bear the main load during the sheet rolling process
Roller system	Upper roller, lower roller, side rollers	Apply bending pressure to the sheet material
Main drive system	Hydraulic motor/electric motor, reducer, gears, etc.	Drive the rollers to rotate
Hydraulic system	Hydraulic pump, oil tank, valve group, cylinder, pipelines	Achieve roller lifting, clamping, and tilting
Electrical system	Electrical control cabinet, PLC, contactors, sensors	Control equipment operation
Operating system	Button station, touch screen or CNC system	Human-machine interaction and parameter setting
Tilting device	Tilting cylinder, tilting frame	Facilitate removal of the forming cylinder
Balancing/synchronizing device	Synchronization valve, displacement sensor, etc.	Ensure consistent movement at both ends of the rollers
Safety device	Emergency stop, limit switch, guardrail, safety rope, etc.	Prevent personnel from accidentally entering hazardous areas

In a typical structure of a four-roll hydraulic plate bending machine, the upper roll usually undertakes the main driving and bending functions, the lower roll is used to clamp the plate, and the two side rolls are used for end pre-bending and overall forming.

2. Essential Knowledge Operators Must Master

Before commencing operation, operators should be familiar with:

Machine structure
Hydraulic system working principle
Electrical control button functions
Movement direction of each roller
Maximum permissible sheet thickness
Maximum permissible sheet width
Minimum rolling diameter
Maximum rolling capacity
Material strength limitations
Maximum permissible working pressure
All hazardous areas
Emergency stop button location
Correct loading and unloading methods
Workpiece unloading methods
Shutdown procedures in abnormal situations

Personnel who have not been trained or are unfamiliar with the equipment’s operation should not operate the plate rolling machine independently.

One of the greatest safety risks of the plate rolling machine comes from the pinching area between the rotating rollers. Therefore, handles, clothing, tools, etc., must always be kept away from the roller system during operation. Relevant equipment manuals also list the rotating roller area as a critical hazardous area.

3. Standard Operating Procedure for Hydraulic Plate Rolling Machine

When training operators, the following procedure can be followed directly:

① Check the equipment

↓

② Check the hydraulic oil

↓

③ Check the lubrication

↓

④ Check the electrical system

↓

⑤ Check the emergency stop and safety devices

↓

⑥ Start the hydraulic pump

↓

⑦ Check the movement of each roller under no-load conditions

↓

⑧ Confirm the plate specifications

↓

⑨ Load the plate

↓

⑩ Center the plate

↓

⑪ Clamp the lower roller

↓

⑫ Pre-bend the first end

↓

⑬ Change direction

↓

⑭ Pre-bend the second end

↓

⑮ Roll the middle section

↓

⑯ Round the plate after multiple passes

↓

⑰ Dimensional inspection

↓

⑱ Meets requirements

↓

⑲ Release the workpiece

↓

⑳ Tilting/unloading

↓

㉑ Clean the equipment

↓

㉒ Check the equipment

↓

㉓ Stop the machine and disconnect the power

4. Pre-start Inspection

Pre-start inspection is a crucial step in operating a hydraulic plate bending roller machine.

1) Mechanical Component Inspection

Inspect:

Check for cracks in the frame.
Check for loose connecting bolts.
Check for obvious damage to the roller surfaces.
Check for foreign objects on the upper, lower, and side rollers.
Check for normal gear operation.
Check for loose couplings.
Check for abnormal bearings.
Check for proper functioning of the tilting device.
Check the reliability of all limit devices.
Pay special attention to the roller surfaces.

Severe pitting, scratches, or localized deformation on the roller surfaces can cause indentations on the plate surface and affect the roundness of the rolled material.

2) Hydraulic System Inspection

The hydraulic system is the primary power source for the hydraulic plate rolling machine.

Key pre-start checks:

① Hydraulic Oil Level

Check the oil level gauge in the tank.

A low oil level may cause:

Hydraulic pump cavitation
Unstable system pressure
Increased hydraulic oil temperature
Abnormal actuator operation
Damage to the hydraulic pump

A high oil level is also unreasonable; the oil level should be checked according to the manufacturer’s specifications.

② Hydraulic Oil Condition

Observation:

Is it emulsified?
Is it noticeably darkened?
Does it contain a large amount of impurities?
Does it have abnormal bubbles?
Does it have a noticeable odor?

Hydraulic oil contamination directly affects the reliability of hydraulic valves, pumps, and cylinders.

③ Piping Inspection

Inspect:

High-pressure oil pipes
Connectors
Valve blocks
Cylinders
Sealing parts

Confirm there are no obvious oil leaks.

④ Pressure Gauge

Inspect the pressure gauge:

Is it at zero normally?
Is the pointer stuck?
Is the surface damaged?
Is the pressure display abnormal?

Do not arbitrarily increase the system pressure to improve rolling capacity.

The maximum allowable pressure of the equipment is determined by the hydraulic system, cylinders, frame, bearings, and rollers.

3) Lubrication System Inspection

The bearings, gears, guide rails, and sliding parts of the plate rolling machine need to be lubricated according to equipment requirements.

Common lubication locations include:

Roller bearings
Tilting device
Guide rails
Gears
Reducer
Sliding bearings
Related moving parts of hydraulic mechanisms

Proper lubrication can reduce friction and wear, and improve equipment lifespan. Some plate rolling machine manuals recommend establishing a periodic lubrication schedule based on equipment load and operating conditions.

Note:

Grease and lubricating oil should not be mixed arbitrarily; selection should be based on the equipment manufacturer’s requirements.

4) Electrical System Inspection

Pre-start checks:

Power supply voltage
Grounding
Electrical control cabinet
PLC
Operating buttons
Emergency stop button
Limit switches
Travel switches
Sensors
Motor
Hydraulic pump motor
Control circuit

Especially important to confirm:

The emergency stop button can normally cut off equipment operation.

Some plate rolling machines are equipped with phase sequence protection to prevent motor reverse rotation from causing hydraulic pump malfunction.

5. Start-up Operation Procedures

Step 1: Clear the Work Area

Ensure there are no:

Sheet metal, tools, bolts, welding rods, lifting equipment, personnel, or other obstacles around the plate rolling machine.

Step 2: Connect the Main Power

Turn on the main power supply.

Observe:

Power indicator light, PLC, touch screen, and all alarm messages.

If a fault alarm occurs, first determine the cause; do not force a restart.

Step 3: Start-up hydraulic plate bending roller

Start the hydraulic pump station.

Do not immediately perform full-load plate rolling upon startup.

For some four-roll hydraulic bending rollers, the manufacturer’s operation manual requires that after a long period of shutdown, the oil pump should be run for a period of time before restarting to allow the hydraulic system to fully establish normal operating conditions. The specific time should be followed according to the machine’s instruction manual.

6. No-load Test Run

A no-load test should be conducted before formal processing.

Check in sequence:

1) Lower Roller Lifting

Observe:

Is the lifting smooth?

Is the descent smooth?

Are the left and right ends synchronized?

Are there any abnormal sounds?

2) Side Roller Lifting

Check the left and right side rollers respectively.

Confirm:

Correct direction of movement
Smooth lifting
Synchronized at both ends
Limit switches functioning normally.

3) Main Roller Forward and Reverse Rotation

Test:

Forward Rotation
Reverse Rotation
Stop

Confirm that the rotation direction is consistent with the operation button.

4) Tilting Device

Check:

Tilting
Reset
Lock

The tilting device must be operated under specified conditions.

It is forbidden to operate the tilting device while the main roller is rotating at high speed.

7. Sheet Metal Preparation

Before formally rolling the sheet metal, the sheet metal parameters should be confirmed.

At least the following should be known:

Material
Material Yield Strength
Thickness
Width
Length
Target Diameter
Rolling Direction
Whether Pre-bending is Required
Whether Tapering is Required

Common Materials:

For example:

Carbon Steel

Q235, Q355, etc.

Stainless Steel

304, 316L, etc.

Aluminum Plate

5052, 6061, etc.

Different materials have different strengths, elongations, and springbacks.

Therefore: For Q235 and 304 stainless steel of the same thickness and width, the rolling parameters cannot be simply copied.

8. Sheet Metal Inspection

Before formally rolling the sheet metal, the following should be checked:

Whether the thickness is uniform
Whether the width meets the requirements
Whether there is severe deformation
Whether there are cracks
Whether there are burrs
Whether there are foreign objects on the surface

The sheet metal should be as flat as possible.

Sending severely uneven sheet metal directly into the plate rolling machine will cause:

Sheet metal misalignment
Oval roll shape
Inconsistent end shapes
Abnormal localized stress

9. Sheet Alignment

Sheet alignment is crucial.

Theoretically:

The centerline of the sheet should correspond correctly with the centerline of the rollers on the rolling machine.

If the sheet is off-center, the following may occur:

Different rolling radii on the left and right ends
The cylinder will be conical
Sheet misalignment
Uneven roller stress
Product dimensions will be out of tolerance

Therefore, after loading, do not rush to roll the sheet. First, complete the positioning and alignment.

10. Standard Rolling Operation Procedure For 4-Roll Hydraulic Plate Rolling Machine

For a common four-roll hydraulic plate bending roller machine, a complete rolling process can be understood as:

Feeding → Centering → Clamping → End Pre-bending → Reversal → Other End Pre-bending → Middle Rolling → Multiple Rounding → Forming → Unloading

1) First End Pre-bending

After the plate is positioned, it is clamped between the upper and lower rollers by the lower roller.

Then:

Start the upper roller
Slowly rotate the plate
Adjust the side roller position
Pre-bend the end of the plate

Stop after meeting the process requirements

The main purpose of pre-bending is to reduce straight edges. If the pre-bending is insufficient, obvious straight sections may appear at both ends of the final cylinder.

2) Second End Pre-bending

After completing the first end pre-bending:

Maintain proper clamping with the lower roller
Reverse rotation of the upper roller
Return the plate
Adjust the other side roller
Pre-bend the other end

The four-roll machine can easily perform double-end pre-bending, which is one of its important advantages over some traditional three-roll structures.

3) Intermediate Rolling

After pre-bending at both ends, begin rolling the middle section of the sheet.

Basic Process:

Adjust side rollers → Start main roller → Sheet advances → Adjust side rollers → Continue rolling → Repeat cycle

In actual production, the sheet cannot usually be rolled to the final diameter in one go.

Instead, it should be:

Gradually apply pressure, gradually shape, and roll back and forth multiple times.

This is more conducive to controlling:

Roundness
Diameter
Residual stress
Sheet deviation
Roller stress

11. Basic Control Methods For Rolling Cylinder

If the goal is to roll a cylinder:

Stage 1: Lightly press the sheet material to create an initial curvature.
Stage 2: Gradually increase the pressure from the side rollers.
Stage 3: Continue rotating and adjusting the roller positions.
Stage 4: Perform multiple reciprocating rolls.
Stage 5: Reduce the adjustment amount as you approach the target diameter.
Stage 6: Perform final rounding.

Avoid excessive roller position adjustments in the final stage.

12. How to determine if the diameter is close to the target diameter during the rolling process?

It can be determined using:

Sample
Outer diameter measurement
Inner diameter measurement
CNC position display on the rolling machine
Laser measurement
Calipers
Measurement tape
Dedicated arc template

For high-precision production, visual inspection alone is insufficient.

13. Why are multiple rolling processes necessary?

Because sheet metal has elasticity and plasticity.

When the external force is removed:

Elastic deformation recovers
The material springs back
The actual radius may increase.

Therefore:

Reaching a certain position on the roller does not mean the sheet metal will ultimately maintain that radius. This springback issue is particularly pronounced with materials like high-strength steel and stainless steel.

Therefore, production typically requires:

Rough rolling → Medium rolling → Fine rolling → Rounding

14. Important Safety Regulations During Plate Rolling

The following situations must be given high priority.

1) Never put your hands between the rollers

This is one of the most important safety regulations.

Do not use your hands to:

Hold the plate
Push the plate
Pull the plate
Clean the plate
Adjust the plate edges

Especially during roller rotation.

2) Never stand in the direction of plate movement

The plate may suddenly:

Slip
Roll up
Pop up
Shift
Obstruction

Operators should stand in the designated safe area.

3) Never roll plates beyond their specifications

For example, if the equipment’s rated capacity is 16 × 2000 mm, this does not mean that all materials can be directly rolled to 16 mm × 2000 mm.

The following also need to be considered:

Material strength
Yield strength
Minimum roll diameter
Effective roll width
Plate condition
Rolling method

15. Prohibited: Correcting Severely Uneven Sheet Metal

Do not use a plate rolling machine as a regular press.

If the plate is severely deformed, appropriate leveling equipment should be used.

Forced correction may result in:

Excessive stress on the rollers
Frame deformation
Bearing damage
Hydraulic system overpressure
Local deformation of the plate

16. Conical Operation

If the equipment supports conical operation, the left and right rollers need to have an appropriate height or position difference.

Special attention should be paid to the following during conical operation:

Plate centering
Right and left roller positions
Side direction of the small and large ends of the cone
Plate width
Cone angle
Minimum rolling diameter
Allowable roller offset

The stress state during conical operation differs from that of ordinary cylindrical rolling.

Therefore:

Conical operation cannot be performed simply according to the parameters of ordinary cylindrical rolling.

For CNC plate rolling machines, the conical calculation program or process parameters provided by the manufacturer should be used preferentially.

17. Unloading after Forming

After rolling is completed, do not immediately forcibly lift the workpiece away.

The correct procedure typically includes:

Stop the main roller rotation
Adjust the roller to the unloading position
Loosen the clamps
Operate the tilting device according to the equipment structure
Open the upper roller end
Use a lifting device to lift the cylinder out
Reset the tilting device
Reset the upper roller
Check the equipment status

Four-roll plate bending machines are usually equipped with a tilting device to allow the formed cylinder to be removed from the roller end.

18. Precautions for Lifting Workpieces

The rolled cylinder is often quite heavy.

The following must be used:

Overhead crane
Crane
Qualified lifting slings
Hook
Special lifting equipment

Pre-lift inspection:

Sling rated load
Lifting points
Workpiece stability
Center of gravity
Wear condition of lifting equipment

Personnel are prohibited from standing on:

Under the workpiece
Within the workpiece’s rotation range
Under the lifting path

19. Shutdown Procedure

After production is completed, the machine should be shut down according to specifications.

General procedure:

Stop rolling → Rollers stop → Rollers return to safe position → Clean equipment → Check hydraulic system → Turn off hydraulic pump → Turn off control power → Turn off main power

After the equipment stops, the following should also be checked:

Oil leaks
Abnormal overheating
Abnormal noises
Loose parts
Sheet metal debris
Metal oxide buildup

20. Daily Maintenance

Per-shift Maintenance

Recommended Inspections:

Hydraulic oil level
Hydraulic lines
Hydraulic cylinders
Pressure gauges
Rollers
Bearings
Gears
Motors
Limit switches
Emergency stops
Lubrication points

Weekly Maintenance

Inspections:

Electrical control cabinet
Terminal blocks
Cables
Hydraulic valves
Hole fittings
Gear meshing
Guide rails
Tilting device
Mechanical connections

Monthly Maintenance

Recommended Inspections:

Hydraulic system pressure
Hydraulic oil contamination level
Oil tank
Filter
Bearings
Roller parallelism
Roller wear
Frame connecting bolts

21. Common Operational Errors of Hydraulic Plate Rolling Machines

Error 1: Rolling directly without centering

Consequences:

Conical shape
Oval shape
Uneven roller load

Error 2: Pressing too deeply in one go

Consequences:

Sudden increase in roller stress
Local plastic deformation of the plate
Excessive equipment load

Error 3: Rolling without pre-bending

Consequences:

Significant straight edges at both ends
Reduced finished product utilization
Difficulty in subsequent welding

Error 4: Ignoring material strength

The rolling difficulty of Q235 and high-strength steel may be completely different for the same 10 mm plate.

Error 5: Ignoring springback

Directly forming according to the theoretical dimensions in one go easily results in a final diameter that is too large.

Error 6: Overloading the equipment

Overloading may cause:

Permanent deformation of the roller
Frame deformation
Damage to the hydraulic system
Bearing damage

22. Operating Techniques to Improve Plate Rolling Accuracy

1) Ensure Plate Centering

This is the most basic and crucial condition.

2) Perform Proper End Pre-bending

Insufficient pre-bending will result in excessively large straight edges.

3) Use Multi-Pass Rolling

Don’t aim for “one-pass accuracy.”

4) Gradually Approach the Final Dimension

After rough rolling, perform fine rolling.

5) Control the Consistency of Left and Right Roller Positions

Especially for cylindrical rolling.

6) Consider Material Springback

High-strength materials and stainless steel require particular attention.

7) Final Rounding

If necessary, perform rounding through multiple back-and-forth rotations.

23. Core Operating Rules for Plate Rolling Machines

Daily operations can be condensed into the following set of rules:

Check before starting, confirm hydraulics first.
Plate must be centered, rollers must be parallel.
Clamping should not be excessive, pre-bending is mandatory.
Rough rolling in multiple passes, fine rolling with slow adjustments.
Overload is unacceptable, stop immediately if abnormality occurs.
Keep hands away from the rotating area and avoid hazards during hoisting.
Clean up before finishing work, and disconnect power only after stopping the machine.

24. Summary

The core of correctly operating a hydraulic plate bending roller machine is not simply “making the rollers rotate,” but rather simultaneously controlling plate positioning, clamping force, side roller position, rolling speed, pre-bending amount, material springback, and final rounding.

For four-roll hydraulic plate rolling machines, the correct operating sequence is especially important. Its structure allows for relatively convenient double-end pre-bending and continuous forming, but the specific roller positions and pressures must be determined based on the equipment model, plate thickness, material, and target diameter.

Before starting: Check electrical systems → Check hydraulic systems → Check lubrication → Check rollers → Check safety devices
Starting: Main power supply → Hydraulic pump → No-load operation → Confirm normal operation
Loading: Confirm sheet material → Center → Position → Clamp
Rolling: First end pre-bend → Second end pre-bend → Intermediate rolling → Multiple rounding adjustments
Inspection: Measure diameter → Measure roundness → Check straight edges → Inspect surface
Unloading: Stop rollers → Release clamps → Tilting → Lifting
Shutting down: Clean → Inspect → Stop hydraulic pump → Turn off power