3 rolls bending machine is a basic forming equipment used to roll metal sheets into cylinders, arcs, or cones. It is one of the most common rolling machines in sheet metal workshops. So, how do you maintain it? Below is a "3 Rolls Bending Machine Maintenance Manual (Detailed and Complete Version)," suitable for workshop implementation, equipment management systems, after-sales delivery materials, and training manuals.

1. 3 Rolls Bending Machine Maintenance Objectives and Principles

1) Maintenance Objectives

* Ensure rolling accuracy and rounding quality

* Extend the service life of the main roller, bearings, and hydraulic system

* Reduce the failure rate and avoid sudden shutdowns

* Ensure operational safety and equipment stability

2) Basic Maintenance Principles

* Lubrication priority, cleanliness is fundamental

* Preventive maintenance > Fault-based repair

* Small problems resolved overnight, major hidden dangers resolved within the shift

* Whoever operates, inspects; whoever repairs, is responsible

2. Daily Maintenance of Three-Roll Plate Rolling Machine

1) Pre-Shift Maintenance (5–10 minutes before startup)

Electrical and Safety:

* Check if the main power supply and voltage are normal

* Check if the emergency stop button and foot switch are sensitive

* Check if the protective cover and limit switches are intact and effective

* Abnormal: Do not start the 3 rolls bending machine

Hydraulic System:

* Oil level above 2/3 of the oil level indicator

* No leakage in oil pipes, joints, and cylinders

* Normal hydraulic oil color (not white, not emulsified)

Lubrication Check:

* Oil film present in the bearing positions of the upper roller, lower roller, and side rollers

* Good lubrication of the slider and guide rails

* Dry friction → Oil must be added before starting the 3 roller bending machine.

Roller and machine body:

* Roller surface free of iron filings, welding slag, and hard objects.

* Roller surface free of obvious indentations and scratches.

* Frame and bearing seat bolts are not loose.

2) Maintenance During Operation (Observe While Operating)

- Sound and Vibration

Motor and hydraulic pump operate smoothly.

No screeching, knocking, or periodic abnormal noises.

- Rolling Status

Sheet material feed is smooth and does not deviate.

Three rollers rotate synchronously without shaking.

The rounding process is uniform, without sudden "material jumping".

- Parameter Monitoring

Pressure gauge is stable and does not fluctuate drastically.

Oil temperature is normal (the oil tank is not hot to the touch).

If any abnormality is found: Stop the machine immediately for inspection.

3) Post-shift Maintenance (Stop for 5-10 minutes)

- Cleaning

Clean iron filings and scale from the roller surface.

Wipe oil stains from the slider, guide rails, and three rolls bending machine body.

Do not allow metal filings to remain overnight.

- Reset

Return the upper and side rollers to the neutral position.

Unload the hydraulic pressure. Return the operating handle to the zero position.

- Shutdown

Stop the hydraulic pump → Disconnect the main power supply. Lock the electrical cabinet. Keep the environment dry and clean.

4) Key Points of Daily Maintenance (Easily Overlooked)

Check the oil level daily; it's cheaper than repairing the pump.

Clean roller surface = rolling accuracy. No delays due to abnormal noises.

No compromises on oil leaks.

5) Prohibitions of Daily Maintenance (Operators Must Know)

Forced start with insufficient oil level.

Rolling plates directly with weld slag on the roller surface.

Repeatedly operating under load with sudden stops.

Rolling of extra-thick, extra-wide, or extra-strength materials.

Unauthorized adjustment of hydraulic parameters by non-maintenance personnel.

3.  Correct Daily Operating Procedures

1) Pre-Power-On Inspection

2) Observation During Operation

Check for abnormal noises or vibrations from the hydraulic pump.

Check for sheet material deviation during rolling.

Check for synchronized and smooth roller rotation.

Check for stable system pressure (no frequent fluctuations).

3) Post-Shutdown Maintenance

Clean iron filings and oil stains from the roller surface.

Wipe the guide rails and sliders.

Return the upper and side rollers to the center, releasing system pressure.

Disconnect the power supply and lock the electrical cabinet.

4. Regular Maintenance Guidelines for 3-Roll Plate Rolling Machine

1) Weekly Maintenance (15–30 minutes)

- Tightening and Structural Inspection

Check and tighten:

Main roll bearing seat bolts

Frame connecting bolts

Hydraulic cylinder mounting bolts

Standard: 

No loosening, no signs of displacement

- Hydraulic System Initial Inspection

Check oil pipes, joints, and valve blocks

Standard: No oil leakage, no "oil dripping"

Oil pipes: No bulging or cracking

- Roll System Condition

Check roll surfaces: For scratches or indentations

Permissible range: No damage affecting the rolling quality

2) Monthly Maintenance (1–2 hours)

- Lubrication System Maintenance

Clean all lubrication points

Refill: Lithium-based grease #2

Key areas:

Upper roller, lower roller, side roller bearings

Slide block, guide rail

- Hydraulic System Maintenance

Clean or replace: Return oil filter

Check: Oil tank breather for blockage

Observe:

Hydraulic oil color and odor

If emulsification or blackening is found → add to replacement plan

- Synchronization and Stroke Check

Check the synchronization of left and right side rollers

Verify upper and lower stroke limits

Standard: Consistent movement, no jamming

3) Quarterly Maintenance (Half-day)

- Precision and Geometric Inspection

Inspection Items:

Parallelism of upper and lower rollers

Coaxiality of three rollers

Reference Standard: ≤ 0.2 mm / m

- Hydraulic Actuators

Inspect the cylinder:

Piston rod for scoring

Seal for aging

Standard: 

No creeping, no internal leakage

- Power System

Inspect:

Motor mounting and alignment

Coupling wear

Cleaning: Motor cooling ducts

4) Semi-annual Maintenance (1 day)

- Hydraulic Oil Management

Recommendation: Use ISO VG46 anti-wear hydraulic oil.

Operation: Drain oil → Clean oil tank → Replace with new oil.

Requirement: Do not mix different brands of oil.

- Main Bearing Inspection

Inspect: Temperature rise, radial clearance.

Abnormalities: Noise, overheating → Replace.

- Electrical System

Tighten terminal blocks.

Inspect contactor and relay contacts.

Clean the inside of the control cabinet.

5) Annual Maintenance (Overhaul Level)

- Roller System Inspection

Measure roll diameter wear

If necessary: Grind or replace rolls

- Hydraulic System Overhaul

Inspect:

Hydraulic pump

Relief valve, synchronizing valve

Calibrate system pressure

- Electrical Control and Safety

Inspect:

PLC/control system parameters

Safety circuits, limit devices

Backup:

Control parameters, programs

6) Scheduled Maintenance Cycle Overview Of 3 Rolls Bending Machine

5. Specialized Maintenance of Key Components

1) Rolling System (Upper Roller / Lower Roller / Side Roller)

Maintenance Focus:

Roller surface condition

Roller shaft and bearings

Roller parallelism and coaxiality

Maintenance Cycle:

Daily: Cleaning, visual inspection

Quarterly: Precision inspection

Yearly: Wear measurement

Operating Points:

Remove iron filings and oxide scale from the roll surface daily.

Strictly prohibit welding slag and hard objects from contacting the roll surface.

Do not allow excessively thick or high-strength rolling.

Regularly check the wear of the roll diameter.

Judgment Criteria:

No indentations or scratches on the roll surface that affect rolling.

Parallelism error ≤ 0.2 mm/m.

Cornerality is normal, with no localized material chipping.

Common Problems and Countermeasures:

2) Bearing and Transmission System

Maintenance Focus:

Main bearing lubrication

Couplings, gear meshing

Temperature rise and abnormal noise

Maintenance Cycle:

Monthly: Top up

Semi-annually: Condition check

Replace if necessary

Operating Points:

Use lithium-based grease #2

Add grease to 1/2 to 2/3 of the bearing cavity

Avoid overfilling to prevent overheating

Judgment Criteria:

Smooth operation

Bearing temperature rise ≤ 40℃

No dry friction noise

3) Hydraulic System (Core System)

Maintenance Focus:

Hydraulic oil

Hydraulic pump

Valve assembly, cylinder

Maintenance Cycle:

Daily: Oil level

Monthly: Filter element

Semi-annually/Annually: Oil change

Operating Points:

Recommended hydraulic oil: ISO VG46 anti-wear hydraulic oil

Do not mix different brands

If oil temperature consistently > 55℃, the machine must be shut down

Judgment Criteria:

Clear oil without emulsification

Stable system pressure

No cylinder creep or internal leakage

Frequently Asked Questions:

4) Hydraulic Cylinder and Sealing System

Maintenance Focus:

Piston rod surface

Seal condition

Stroke smoothness

Maintenance Cycle:

Quarterly inspection

Immediate handling of any abnormalities

Operating Points:

Keep piston rod clean and free from impacts

Replace seals immediately upon discovering oil leaks

Do not operate with faulty components

Judgment Criteria:

No surface scoring

Smooth stroke without vibration

No internal or external leakage

5) Electrical and Control Systems

Maintenance Focus:

Control cabinet

Sensors, limit switches

Motors and frequency converters

Maintenance Cycle:

Monthly cleaning

Semi-annual inspection

Yearly parameter backup

Operating Points:

Keep cabinet dry and dust-free

Do not plug or unplug components while powered on.

Regularly check grounding

Judgment criteria:

Secure wiring

No alarms or malfunctions

Good heat dissipation

6) Frame and structural components

Maintenance focus:

Frame welds

Connecting bolts

Deformation

Maintenance cycle:

Monthly routine inspection

Annual special inspection

Operating points:

Focus on high-stress areas

Stop machine immediately upon finding cracks

Prohibit prolonged overload operation

7) Special maintenance for safety devices (must be listed separately)

Includes:

Emergency stop button

Travel limit switch

Protective cover

Foot switch

Requirements:

Monthly functional testing

Stop the 3 rolls bending machine immediately upon failure

Do not disable without authorization

8) Red lines for critical component maintenance (must be followed)

❌ Continuing production with damaged rollers

❌ Ignoring oil leaks

❌ Dry running of bearings

❌ Adjusting hydraulic valves by non-professionals

❌ Operating machine despite safety device malfunction