4140 bending

[tintapper]

We have been bending 3/8 4140 on our press brake to a 45 degree bend.
This particular piece has a cnc cut out of it. We have done this many times in the past without problems. This time we have had a lot of cracking on the cut out section. Any ideas.

 

[metengr]

Did you verify the heat treatment condition of the 4140 material prior to bending? Do you know the heat treatment condition?

 

[MiketheEngineer]

Are you sure it is 4140??

 

[TVP]

Besides the previous questions, do you know what type of CNC process was used for the cut-out, i.e. CNC milling, CNC water jet cutting, CNC laser cutting, EDM, etc.? All of them can make a cut, but the resulting surface condition is considerably different.

 

[btrueblood]

...not to mention HAZ and notch formation due to some of the cutting processes.