Hydraulic Drive for Plate Bending Machine

Required output (in watt) of hydraulic motor should be

=(2*Π*N*T*factor of safety)/Efficiency of gear system

N= RPM

T =Torque

=(2*3.14*6*496881*factor of safety)efficiency of gear system

hence Output of hydraulic motor /efficiency of of hydraulic motor is =Input required for hydraulic motor

Again Input required for hydraulic motor/ Hydraulic system efficiency= Output of hydraulic pump.

Again Out put of hydraulic pump/ Efficiency of pump = Input required for pump = Output of Electric motor.

Out put of electric motor/Efficiency of electric motor = Input power required for motor.

I am sorry to mention again, as I many times wrote, when one of us gives a counsel he has to be at least 101% sure that what he writes is CORRECT since we take a responsibility.

The problem with your counsel is the basic equation which is WRONG: Power is the product of Torque (in Nm for instance) with Angular Velocity (in Radians/s) and the result is in Nm/s=Watt!

Unfortunately N was given in RPM and is NOT equal to the angular velocity in rad/s!!!!!

The relationship between N (RPM) and ω (rad/s) can be deducted as follows 1 rotation = 2*PI radian and 1second=1/60 minutes.

I let you correct the equation and give the right answer.

nick name Sorry I do accept the basic mistake in formula, and should have been taken as RPS not RPM.

Here is corrected Equation

Required output (in watt) of hydraulic motor should be

=(2*Π*N*T*factor of safety)/60*efficiency of gear system

N= RPM

T =Torque

=(2*3.14*6*496881*factor of safety)60*efficiency of gear system

Thanks

DEAR SIR,

I HAVE MANUFACTURE COMPLETE HYDRAULIC CIRCUIT TO OPERATE 2 CYLINDER AT A TIME. BUT WHEN I OPERATE THE HYDRAULIC CYLINDERS PISTON ROD COME OUT EXACTLY BUT WHEN IT GO IN BACK IN CYLINDER THERE IS NOISE SOME THING LIKE VIBRATION AND THAT SOUND IS COME OUT FROM CYLINDERS. WHAT SHOULD I DO TO SOLVE THAT PROBLEM.

PUMP 16 LIT AND 80 BARS

DIRECTIONAL VALVE 50 LITERS

HYDRAULIC TANK 80 LITERS

HYDRAULIC CYLINDERS (100 MM ID AND ROD DIA IS 70 MM AND STROKE IS 750 MM) X 2 NO. OF CYLINDERS

PLEASE SEEK YOUR KIND HELP

THANKS

A late comment since your question was not related to the thread.

The vibrations could come from the load you move since the depending on the hydraulic connections design the system compliance can depend on the direction.

Describe the whole system with details concerning the load you move. If compliance is too low then stick slip could occur. An other reason can be the hydraulic design and how valves are used (type a.s.o.)

About 27 gpm

Dear Guest,

Your result is correct. I think that the error is in the magnitude of the moment you consider. In a 3 roll plate bending machine the driving moment is not the bending moment of the plate but the result of the friction of the two other rolls under the forces used for bending. I do not know the Sy of the plates you intend to bend but we can estimate the bending moment assuming that the whole section is plasticised in which case the Moment is:

M= L*Sy*h^2/4 with L= length of plate and h its thickness.

To take an example L= 3 m, Sy= 340 N/mm² and h=16mm

M=6.53 E 7 Nam = 65300 Nm. Your moment is 7.61x bigger. This means that the product L*Sy is also 7.61 x bigger.

Let us assume that L=8m and Sy= 940 N/mm² so that the bending moment is as big as your computation gives as result. the moment required to turn the active roll will be around 35000Nm which is about 14x less the one you take into consideration.

The problem is not your hydraulic computation which is correct but your assumptions concerning the moment requirements. The starting value should be checked and corrected.

I made only some estimations since it is your project but I believe not to be very far from the true values.

I hope it helps and I would like to have a return comment.

If you need I can make a sketch how I see the problem.

Guru, you have hit the bulls eye, your explanation was what i was expecting, i feel you have identified the right point where i was wrong, thank you for the timely insight .....

The plate roll has an electric drive on it now. Emulate that or emulate one from a plate roll of recent manufacture that does what you want. Use a Rineer hydraulic motor as it is most likely to put up with the abuse. Mount the motor as bidiectional and use a Brake/Clutch to send power to the Gear box for operator safety and control. Designing your own for power and stress will be a nightmare copy one that works.

I guess-timate 27 gpm and about 500-800 psi

though I would make enquiry: "Parker - Motion Control Systems"

I do not your guess-timate since if you accept the data from the question the power required is 312,2 kW.

The pressures and flow you estimate lead to powers of 5.88 to 9.4 kW.It is at least a slight difference.

If you do not accept the data in the question then which data have you considered for the estimation? Where do you start from?

Simple curiosity, I do not contest your values but I would like to understand how you did come to them.

Thanks for an explanation,

Nick

Experience

I can't give it away...but what are you considering the gearbox doing?

A hydraulic designer will require you to provide the data on the input torque to the gear box which is almost equal to the hydraulic motor(efficiency and safety factor included) and the pressure to which you like your system to operate.

If you have the torque and pressure parameters, you can calculate the possible displacement of a correct hydraulic motor size, then look for catalogue and choose your hydraulic motor(LSHT=low speed high torque) and my estimate will end up to a radial piston motor. The formula is:

D= 2pi*T/P

Where D= displacement

T= motor output torque= gearbox input torque (and efficiencies)

P= operating pressure

then you can calculate the flow needed for particular speed:

GPM= D*RPM/231

I suggest you buy a variable displacement pump and choose a little bit higher flow capacity to make room for possible higher speed adjustment.

You can also calculate the HP= GPMx PSIx .000583(mine is .0007 safety factors included)

I hope this helps...