EN

BENDING SPRINGBACK


Bending springback
Springback is the factor for every industrial deformation of metal which take effect and should be considered during the daily work. Why? Because ignoring it will effects the final tolerance and precision of bending. In general springback is the elastic return of material after the controlled deformation with the condition of material to be return into the initial condition. Springback is the parameter which is known for every operator of press brake and should be noticed during the performing of the production program according to the conditions and sizes in the drawing of part. Normally, the drawing of part contains only required parameters so the springback is the headache of the operator how with the elastic return of material to obtain the necessary parameters. Moreover, important to know - elastic return of the material and necessity to take this parameter into consideration and compensation - is the main story for all, exactly all technological process of metal bending and deformation - press forming operations, tube bending, bar and wire bending, coil deformation etc.

Springback is getting highly important when the application has the precision tolerances and normally less actual if we are talking about, for example, metal furniture boxes where values are not very strict. Moreover springback has the other attribute as accumulation of deviations. It means that missing of compensation and the part with several bends will have on the last bend completely bigger deviation or tolerance lack as on the first one. This could be the story of bending of profiles with the consistent bending steps from one to other side.

Important point to say - there is no any possibility to guarantee real springback values. Yes, springback in theory could be calculated but the value will be theoretical and everybody should know that even other batch of sheet metal with the same material can change the springback values. So, the precision way to calculate the springback is to get and measure real values according to real part bending with different angles. And everybody needs to know that for springback there are no non-important parameters and everything values: thickness, material type, material batch, material coating, even the length of bending can show different values.

For us, as suppliers of press brake tools springback is important to notice for the customer the main limits. For example, customer wants to buy R25 tool to get internal radius after bending as R25. This means that he will has zero radius springback which mainly not a true. Moreover springback is the factor why it is impossible to guarantee precision radius on the special bending application, for example rib forming.

For operator springback is the factor to add to the bend to get finally the angle he need after the springback. Otherwise he need to bend one more time the same part. With the help of CNC or special bending software springback could be added but as we told, to calculate the value precisely you should measure it in reality without the calculation theories. The opening of the die could also play the role - the more sharp angle helps to prevent the material springback during the return stroke of the punch itself.

As you can imagine springback value also based on the material and thickness. Moreover, ignoring of springback even in small value with the part of several bends will finally make total error with summary of bends which could be much more critical than single bend deviation.

Normally springback also the main factor why manufacturer of press brakes offer as standard or optional digital measurement systems for angle measurement with the data transfer to CNC control. This is and only because of springback, otherwise what is the reason if you entered the angle already. Moreover this is the easiest way for automatic measurement of first part to proceed with next parts without the mistakes.

Springback compensation is the term which is used as bending including the calculated springback value i.e. overbending which at the final makes the elastic return of the part to condition you exactly need. Usually it is written also that against air bending the coining which means the material touches together the punch and die and mainly this process also reduce the springback value. But this technology is not used too much because require more force than air bending and reduction not means the total elimination so less value of springback will be presented.