How to Calculate Springback

If you are reading this article it is because you are starting to bend and you want to know how to calculate the springback of a bend. Yes, it is one of the first problems a tube bender runs into, but it is not impossible to calculate the springback of a bend. Once we know this data, we can insert it on our tube bending machine and our bends will always be perfect.

How to Calculate Springback?

Let’s start from the beginning with a small premise, each bend has a springback and this is different for each batch of pipe we have purchased, it depends on the thickness, the material, the outside temperature … in short, a thousand factors. That is why it is very important to know how to calculate the springback. 

Wherever we go, if we learn to look around us, we will find bended elements, from the profiles of bus windows, to swimming pool ladders, from children’s playgrounds to gym equipment, in short, the world is full of bends and if we have to make them in series, we absolutely must find out what is the springback of each of them.

But how is the springback of a bend calculated? What is the mathematical operation to be carried out? 

Springback is that force that shows up at the end of each bend, a small geometric variation that occurs on the material due to the release that occurs after the tools of our tube bending machine are opened. All this is normal, every material, every thickness, every radius has a different springback. Of course the springback can be calculated and it is very important to do so in order to make a series of bends that are all the same. To calculate our springback and to be sure of making a 90 degree bend, we have to insert your for the first time on our machine, a scrap tube, a tube that we will use only for calculations, but it must be from the same batch of “good tubes” that we will use for subsequent jobs, because as mentioned before, each batch of tubes has a different springback.

Once the tube has been inserted, we set a 90 degree bend on the control of our tube bending machine, without of course entering the springback data because we don’t know it yet. We start the machine and make our bend without springback. Once the bend is complete, we extract the piece from our tube bending machine, place it on a plane and with the aid of a protractor, measure the actual angle made.

The difference in this angle made on the 90 degrees is our springback. So the shape to be made is 90 degrees, minus the degrees that came out of our first test curve, is our springback.

But let’s take an example. In our first bend, the bending angle that came out is 121.3 degrees, minus the 90 degrees that we should have made, the result is 31.3 degrees. Which we will enter on the control of our bending machine, in the springback space provided.

Once the springback data has been set on the machine, we can insert the same tube again and resume the bend, start the machine again and see if the calculations we made are correct. The machine this time will bend up to 121.3 degrees and the bend that comes out will be 90 degrees exactly.

Now that we know how to calculate the springback of a bend and have set it on the control of our machine, all subsequent bends, even those with different angles, will come out perfect. Be careful, however, that it is always the same batch of tubes, if the batch of tubes changes, we have to calculate our springback again. 

Watch the video we made on how to calculate the springback of a bend.

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