Press brake tooling help

[firemaker]

Hi guys

I am in need of your advice.

I need to press a 100mm radius along a 400mm long piece of 5mm steel. I have made a tool with a half rad press tool that pushes into a 150 x 150 90 degree angle.

My part is coming out under bent? I was just after advice on what angle i should make my female tool to achieve this?

I only have a small press (stroke) and we have been pressing these with success for a while but would like to ammend the tool so we can press them perfect.

Any advice would really help us?

 

[pedrobedro]

You probably have to allow a bit of over bend to compensate for spring back, it might be a bit trial and error but once you find the right amount it should work out.

 

[firemaker]

Do i need a v block or can it be a channel for the bottom tool?

How do i allow for springback when i am bottoming out on the bottom v tool? Do i nees to change the angle?

 

[pedrobedro]

You probably need to change the angle to something like 88° for it to come out at 90° for cold bending your plate. If you use channel it would obviously have to be stronger than whatever you are bending or it will splay out under the pressure.

 

[firemaker]

Ok thanks pedrobedro. If i change the angle do i need to open up the v so that there is a flat at the bottom? At present i am bottoming on the bottom tool.

 

[Paul.]

A channel is ideal for biggish rads like that, as said you will be getting a bit of spring back so will need to push it deeper into the tool to over bend it a bit, you need to be air bending not bottoming out (coining) often channel isn't deep enough to get the depth, and 5mm is quite heavy, I would reinforce the edges of the channel with a couple of round bars, as well as adding depth and strength it will be kinder to the face of the material, as the job is quite short you could also plate across the ends of the channel and rounds to add some strength, This is one I drew out for another job, but you'll get the idea

 

[firemaker]

This is just the info I needed. How do you determine the width of the channel? Thanks a lot!!

 

[Paul.]

180 looks about right for this, i would also make the rad of the top tool a tad under size to help with the spring back, just a quick sketch but it is to scale and dimensioned as well.

 

[firemaker]

Paul your a star thankyou!

 

[firemaker]

One last clarification. The tool legth needs to be 420mm. How do you suggest we stop it bending the channel? We can blank the ends but will yhat be enough?

 

[Paul.]

You will be surprised how strong a channel with a round stitched to it will be, I used to use this exact method to form hydraulic oil tank bodies from 4mm plate up to 2mtrs long.
As an alternative, and for interest, if you have some chunky bar kicking around to give the depth, you could build it on a flat plate, a bit of packing under the round bars will make it deeper, various ways to bully metal into shape, imagination is your best tool

 

[Hitch]

I'd agree with Paul on the above, a few mm slightly smaller for the top, channel with some round bar welded on the toes..... make it 450, and cap the ends off.
If its 100mm radius, i'd look at making the top tool from a bit of 193 Diameter chs, bottom from a bit of 200x90PFC, with a bit of 20mm bar welded on....

Ho many of these bends do you need to do? how many degrees is it under bent? If its only a few, a decent copper mallet/hammer will soon put that right +/- a fair bit to be honest.
If its a lot, then getting it right straight from the machine is better obviously. I tend to do a fair few big radius bends, usually one offs, a bit of tweaking back and forth in the press is common to get the bend in exactly the right place/angle.

 

[Spark plug]

I always find it's easier, if you can't get the angle spot on, is to bend it too far then bend it back till it's right

 

[Hitch]

I always find it's easier, if you can't get the angle spot on, is to bend it too far then bend it back till it's right

Quite, much easier to knock it back out than it is to put more in in most cases.