How to size a high torque gearbox for a CNC Tube Bender?

When I started out, I took advantage of the application engineers at the distributors of high torque gearbox. They are the specialists on this matters.

May have to do a little investigating on your own to decide which ones gives the better service, but you pick up very valuable information, that will help your experience.

good luck,

phoenix911

You talk to someone at one of the companies that make high torque gearboxes.I been doing my research on here just have found the right one yet but I will keep trying.Sounds like you have design such a machine.

I have looked at tube benders to purchase. But I have I looked at gearboxes and drives for process equipment I've designed. Have to be careful with the suppliers though, They may be able to talk the talk, but not walk the walk.

Do not know the requirements on the tube benders, otherwise I'd help more.

You are right.I am rethinking the problem and looking it at this way.If I figure out how much force that is required to bend the tubing,I might be able to figure out bending arm torque of the gear box.I have to look up the yield strength of steel,section modulus and all those other equations.Now tell me if I am on the right track far as finding the moment of piece of 2"X4" tubing?I believe the Yield Strength is like 60,000 psi.Not sure on that.

nice shareware program called beamboy, can help you with this. I recommend this often.

Also, what type of tube bender, does it have a mandrel insert?

Thanks.Yes it has a mandrel insert and I will check out the software.

I have 2 comments:

- how did you come to the used figure of 59033.1 Nm ? do you realy need the 0.1 Nm ?

- there are several methods for gear computation either a DIN/VDI standard if you are in Europe or the AGMA norm if you are in the USA. You may use also different design softwares, some of them are available "on line" for a quite reasonable cost. GOOGLE will allow you to find the address the best for you.

Those norms give as well the equations as the different coefficients based on a lot of research to achieve a good result. I presume that in your case the rotational speed of the last gear will be very small so that the problem could be the stability of the lubrication since sliding speed will be very low, I would suggest a strong overdimensioning for reduction of the specific load (in N/mm).

The value was given to me from a guy who works for a tube bending company.I am trying design a machine that is capable of bending 2"x4" rectangular tubing.The bending torque is for bending the tubing the hard way.So I figure if I could design a machine based on that value.I am learning along the way just need to be point in the right direction on the gearbox and you are given me alot of help here.

I would be careful with soft packs for beam design since those programmes are often limited to small deformations as in structural design. Bending requires many times rather big deformations so that the material goes out of the elastic range for which structures are generally designed. If it would be not so the tube will come back to its initial form!

You have to take care of the minimal possible radius imposed by the wall thickness, if the radius is too small there is a buckling of the wall since its deformation in the elastoplastic domain goes too far. Never the less it is possible to accept the plane deformation theory which allows the estimation of strain and based on it the computation of stress and bending torque.

The stress distribution on the cross tube section is not any more linear as in the elastic domain : part of section around the neutral axis stays elastic and from the limit of elasticity to the outside limit the stress does not any more increase with same proportionality to strain (slope being the young modulus). The simplest approximation is a 2 slopes one : till elastic limit young modulus after about 3 to 10% of it.

A detail from own experience the temperature has a not neglectable influence since the material mechanical properties do change with it.

I was many years ago in touch with people making such machines and i remember that for big torques they came to the conclusion that a hydraulic system was more able to lead to a reliable machine.

that is true, I am getting sloppy and I should elaborate more, Use it to establish a preliminary base line, and verify it with experience and double check.

thanks,

I will take in consideration what you have said and you are right about the hydraulics.

How many such do you want. i can get you Planetary Reducers with reduction ratio ~5000

You can round off the torque--you know--to say " ~ 60,000 N-m"

In practice ,this a fabulously high torque. The machine will be like a giant Hydraulic Press.

Could you tell us the Max pipe size you want to bend--ODXwall thickness.