Hyd Press Brake and Thin Aluminum

[mmorton]

OK Guru's.... I really need some help. I can usually find a thread for my issues but this time I came up empty, here goes.

My shop has a 12' 200 ton Hyd Press brake, we use this unit to fabricate a variety of aircraft parts that are never a straight forward bend, we also usually air bend. My problem is we are trying to bend a 12' long thin sheet of aluminum 3" wide to a 90 degree angle (material is 2024T3 .050" thick) ...simple right? well it seems I cant get there from here with the knowledge we have on this machine and tooling. We are using a .200 radius punch and die set up, every time we bend the aluminum. it wants to bow and we can never get a consistant bend from the outboard ends and the middle, Now i know about deflection and this press brake is fairly basic so there is no auto crowning feature but no matter how much we shim the die there is no consistancy, if we get a 90 in the center we are getting about a 76 degree under the rams, when we shim under the ram to get the 90 we lose the center, its a vicious circle! Anyone have any ideas!! we have tried many things but am open for any advise. Thanks

[striker12300]

Do you have one continuous die or sectionals?

[mmorton]

One piece goose neck die.

[striker12300]

We've only had success with shimming. If we couldn't get it exact, which was rare, we'd bend it to 90 and the other areas would be a little over 90. Then take a mallet and round dolly and tap it back to 90. I hope someone has a better way because I'd like to here it.

[mmorton]

We have been trying to shim for several weeks now with various results but none that will give us a usable product. We have removed everything now, re-claibrated the unit, we are using 3 3"x6" test plates (1 under each ram and 1 in the center) we have the rams hitting the same and getting the same dimension on the bend (best was 90 degrees under rams and 85 in the center) we have now tested a full length part and the result was all over the place due to spring back (83 at the r/h end, 79 at the l/h end and now 70 in the center). We are abondoning the die shimming for now and going to try to shim the punch as we think this will give us a more gradual result.

[rjahr]

Might be easier just to give it to someone who has a newer press brake with crowning... Depends on tool wear as well if we need to change our crowning it is a press of a button..

[mmorton]

Tooling is new and was made specifically for this job, however the tooling maker only test small test pieces when they make the die, so they never saw the issues. Press brake is also fairly new (under 3 years) less than 200 hrs on the unit. We really need to make this an in house project, I have a vendor that can bend the parts but they have a minimum quantity buy which causes me to hold inventory on the shelf (a whole seperate issue) so I need to be able to produce the product per job.
We made some progress with having the shims under the die but still not a usable product. After a conversation with the tool maker they say they could grind the die to compensate for crowning if I can give the dimension of what shim thickness it take to make the angle I am trying to achieve, this is a possible solution and the direction we are moving toward. It is old technology but sometimes you have to go with the basics. I am still open for any suggestions. Thanks

[WATERJET71]

make sure your punch is 88 degree also from the inf you are given .050 aluminum bend rad. .200 you should be using .450 bottom die . may be you are using the wrong botoom as well.

[rjahr]

I'll be out right and honest... you have the wrong machine for doing these parts... First off your tools should be precision ground for a job like this to make sure they are accuarate across the brake.. secondly if you have to shim you'll have to do it each time.. and be precise about it.. if your shimming it right now and can't get consistency I don't know how your going to tell your die maker how to grind to height.. If the brake is less then 3 years old and doesn't have some kind of crowning you guys might have gotten the wrong brake..

Tooling is new and was made specifically for this job, however the tooling maker only test small test pieces when they make the die, so they never saw the issues. Press brake is also fairly new (under 3 years) less than 200 hrs on the unit. We really need to make this an in house project, I have a vendor that can bend the parts but they have a minimum quantity buy which causes me to hold inventory on the shelf (a whole seperate issue) so I need to be able to produce the product per job.
We made some progress with having the shims under the die but still not a usable product. After a conversation with the tool maker they say they could grind the die to compensate for crowning if I can give the dimension of what shim thickness it take to make the angle I am trying to achieve, this is a possible solution and the direction we are moving toward. It is old technology but sometimes you have to go with the basics. I am still open for any suggestions. Thanks