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PRD Plate Bending Machine Operation Manual

About PRD double pinch 3-roll bending machine

Pyramid Plate Roll Machine
Pyramid Plate Roll Machine

PRD series double pinch 3-roll plate bending machine has a good function for the end bending of flat, it’s used to bend the mild carbon steel(the yield limit up to 245Mpa) in normal temperature (cold bending) to circle, cylinder, and cone. PRD Bending Rolls are widely used for petroleum, chemical, boiler, shipbuilding, hydro-power, metal structure, and machinery manufacture.

The two lower rolls of the PRD Bending Rolls are the main drive. The top roll position is fixed, and the lower roll does the tilting movement along with the arc. The hydraulic engine drives the reducer to realize the rotation of the lower roll. The output shaft of the reducer through a group of gear to transmit the two lower rolls. The transmit direction of the rolls depends on the main engine’s direction.

The lower roll elevation movement used hydraulic transmission. The elevation data can be read out from the display. It’s easy to take off the workpiece. The independent and movable console makes the operation very convenient. The safety device makes the operation more safety.

The PRD Plate Bending Machines are easy operation and maintenance, have high precision, small unbend flat edge. It’s advanced and practical plate/sheet bending equipment.

The use environment of the PRD Bending Rolls: temperature: 5-40℃, humidity below: 80%, electricity: 380V,50HZ (Can be customized).

Technical data

  1. Max. bending thickness             3-30mm(σS≤245Mpa)
  2. Max. pre-bending thickness       (3-30)*0.8mm(σS≤245Mpa)
  3. Max.bending width                      2000-40000mm
  4. Working roller length                 (2000-40000)+50mm
  5. Yield limit                            ≤245Mpa(N/mm2
  6. Top roll diameter                       ***mm
  7. Lower roll diameter                    ***mm
  8. Rolling speed                         about 4m/min   
  9. Main power                           **KW               
  10. Hydraulic power                   **KW
  11. Reducer                                ZSY-***
  12. Working pressure           19.5Mpa
  13. CNC/PLC                                  ***


The main structure of the PRD Plate Rolling Machines is consist of the top roll part, lower roll part, main transmit part, right and left frame, drop end part, electric hydraulic part, and base.

Top roll

The top roller part consists of a top roll, bear, bearing seat, and end cover.
To compensate for deflection in a roll bending process, the top roll is “crowned.”. (Why “crowned” the plate roller?)Normally utilize 75 percent of nominal capacity, with all things—yield, width, diameter, pinch pressure, and speed—being equal.
There are two steps for the roll hardness. The first step is heat treatment quenching and tempering HB235-255 and the second step is Rockwell HRC38-42.
The self-aligning roller bearing is installed in the bearing seat on the two sides ends of the up roller.

Lower rolls

The lower roll part consists of the two lower rolls, the lower roll oil tank, and the right and left bearing.
The lower roll is made by No.45 steel, the oil piston pole belongs to No.45 forged parts, inter surface of box polished, the surface of piston pole painted by Cr. The seal parts used the UN seal ring which is imported from Japan. The pressure of material shape is from cavity work without the pole. The piston pole of the lower roll oil tank connects with the right and left bearing.
The main oil piston work under a pressure of 19.5 Mpa.
The right and left bearing is made of No.45 steel, it’s very light and wearable.

Transmit device

The main transmit device consists of the gear, shaft, shaft pin, and retaining cover. They are the heart of the machine, it’s the most important part, we should protect it carefully.
The gear, chain, and shaft are all used No.45 steel, the strength is very high and wearable, and it can improve the working performance of the machine greatly.

The right and left frame

The right and left frame is welded by the steel plate, the structure is very impacted with high strength. There are several times grinding and polish for the surface, the feature is very beautiful and smooth.

Drop end part

The drop end part is consist of the overturn oil tank, shaft pin, frame, and other accessories. When roll bending is finished, put down the overturn device then take off the workpiece.
Drop end device driven by a hydraulic piston which power has come from the hydraulic station. The connected pole drives the up roller bearing base to make the bearing base reverse and piece on.

The oil piston pole belongs to No.45 forged parts, inter surface of box polished, the surface of piston pole painted by Cr. The seal parts used the UN seal ring which is imported from Japan. The pressure of material shape is from cavity work without the pole. The piston pole of the overturned oil tank connects with the frame.

The main oil tank’s working pressure is 19.5Mpa.

The base of the machine

The base of the PRD Bending Rolls used frame structure, the whole body with strong rigidity.

Balance beam

The balance beam installs at the end of the top roll. After finishing the bending process, it must fall down the screw pole in the balance beam at the end of the top roll before separating the overturn device and the side of the top roll overturn. Reset the overturned device after finishing unloading. Make cap of screw pole to the original position and in a freedom state then begin to start the CNC plate bending machine.
During running the bending rolls, when the lower roll does the movement of elevation, be sure to confirm the two sides of each lower roll elevate at the same time, or it will damage the gear of the lower roll and the shaft gear.

Electric principle

The electric control system consists of an electric control cabinet and console. The electric power is 380V/50HZ. Main switch with short circuit protection and the main motor overload protection functions. Counter-rotating motor contactor by exchange control, the control circuit used to control 220 V control and reliability, and long life. The elevation of the lower roll used mobile sensors and digital display table shows.

  • Main power:380V 50HZ Can be customized
  • Control power:220V Can be customized
  • Oil pump motor: *KW

The contactor is the core of the electric control part. Couple with the electrical control system and hydraulic operation system to realize the running of the machine. The display device showed the volume of mobile action, and visual operation, a button control desk through a number of digital settings to achieve the lower rolls lift and moving around control.

Hydraulic system

There are five hydraulic oil tanks in this system they are two elevation oil tanks of left lower roll, two elevation oil tanks of right lower roll, and overturn oil tank. The system uses a high-pressure quantitative gear pump as the power source, the superposition type hydraulic valve as a control element, a pressure regulating circuit, a synchronous loop, speed loop composed of the whole hydraulic system. The system has a pipe layout simple, less leakage, maintenance convenient debugging.


After finishing, the installation of the bending rolls, put the hydraulic station in the fixed position appointed in the ground foundation drawing. Connect the hose between the hydraulic station and the plate rolling machine. When connecting the hose, please confirm the “O” seal ring in the right installation. Through the air filter of the hydraulic station to put the appointed No. Hydraulic oil. Connect the power then begin the test running.

Hydraulic elements

Pressure gauge

The pressure gauge is used to display the oil pressure. If there’s damage when running, please cut off the power, stop the oil pump and change the pressure gauge.

Air filter

There are two functions of the air filter. One is pouring into the flash air when the oil pump working. The second is to filter the hydraulic oil when refueling. The air filter should be cleaned timely according to the actual usage situation. (Note: It must be filtered through the air filter when refueling)

level indicator of plate roller
level indicator

Oil level indicator and oil thermometer

The oil level indicator and oil thermometer install on the side of the oil tank in order to observe the oil mass and temperature. When the oil mass is lower than the down limit, please refuel. And when the temperature of the system is higher than 65℃, the cooling step should be implemented.

Filter actuator

The filter actuator is installed at the entrance of the oil pump in the oil tank to prevent solid impurities damage the oil pump. It should be cleaned every month.

Maintenance and inspection

Daily inspection items

  1. Inspection of the surface of the hydraulic station
  2. Inspection for oil mass in hydraulic station
  3. Percolation of the hose system
  4. Percolation of the pump, valves, and oil tank

Regular inspection item

  1. 500-600 hours(60-75days)
  2. Detail inspection for daily inspection items
  3. Action check for the hydraulic system.
  4. The hydraulic system should be run at maximum pressure.

Change the working oil

According to the up items to confirm the oil level of the hydraulic station and refuel it when the oil is not enough. The oil should be changed every year. Before changing, the oil, pull down the cover of the hydraulic station and wash the oil filter of the pump and the inner tank of the hydraulic station.

5 common faults and solutions

The pump is not out or the oil

Oil pressure is too lowPlease don’t make the oil surface lower to the down limit or should refuel.
Range sluggish blocked pipeCleaning oil absorption pipes and filters
The oil absorption of inhaled airSeal joints put some good
Pump to the anti –Changed to make it with the request to pump in line
Oil viscosity is too highUse appropriate viscosity of the oil
The lack of speed pumpsShould reach the minimum speed above
Oil mixed with airStraightening occasions mixed with the air and repair

Can’t catch the pressure of the loop

Because of the above reasons not pumping oilImplementation of the above measures
System low-pressure settingsManometer with the pressure to re-adjust settings
The safety valve does not workDisassembling repair
Valve, internal fuel tank leakageHydraulic circuit smooth zoning and inspections are relatively independent components
The hydraulic valve does not workInspect the hydraulic valves, electrical circuit investigation
Pump failurePut pumps removed for repair
Hydraulic system leaksInspection and repair
Cylinder piston seal material damage occurredReplacement of the fuel tank repairs Seals
Reversing bad valveRepair valve

Can’t keep the pressure of the oil tank

No dust control system?Cleaned up
Inhalation pipe, filters blockedCleaned up
Side air inhaled into theCanada Oil Ministry portfolio, as the voices of small tightening, may
Enter from the side of the air pumpAxle grease seal around Canada, the small voices of change, the replacement of components sealed
The pump motor and loosening boltsTighten bolts

There’s an abnormal sound of the oil pump

Pump and motor shaft connected to the heart with differentInspected and repaired
Relief Valve VibrationInvestigate whether there is air access
Too thick oil viscositySuitable oil
Pump the rotation direction of the anti –Correct direction of rotation
Oil bubbleInvestigating whether to return water pipe
Oil surface below the baselineOil added to the baseline above
Exceeds the number of the rotary pressureRotating a few adjustments and pressure
Tank, pipeline sealing material injurySo single pieces of commissioning and the replacement of components sealed
The fuel tank had no outflow of oilNot seeing the light of the oil pump failures, this time to be maintenance base
Speed control valve improper adjustmentRe-regulation
To the fuel tanks recoiling large pipelineIncreased tube models or increase the system pressure

The inefficiency of the oil tank

Range sluggish blocked pipeCleaning oil absorption pipes and filters
The oil absorption of inhaled airSeal joints put some good
Pump to the anti –Changed to make it with the request to pump in line
Oil viscosity is too highUse appropriate viscosity of the oil

Installation of the PRD Plate Bending Machine

 Ground foundation diagram of  PRD Plate Roller
Ground foundation diagram of PRD 12*3200 Plate Roller

According to the requirement of the ground foundation drawing, install the PRD Bending Rolls in a solid ground foundation, adjust the level, fix the foot bolt, and connect the electric control parts with the hydraulic hoses.


For the slide position, PRD Bending Rolls all used the bearing which is made from the new material including the oil. The times of lubrication are less and little lubricating oil.
For the new machine, the lubrication oil sump should be changed oil every three months. Later, every half a year to change it. The lubrication grease should be changed every day.