The Perfect 90 and Roll Forming

[nornrich]

All,

We are looking to mount two items on each of the legs of a Steel "L" Angle. We need the two surfaces to be as close to 90 deg. as possible. The problem with angle is you can't always count on this. We are thinking of going to roll forming. We can live with the radius on the roll forming, but we are unsure how tight a tolerance on the angle we can get. Anyone have any thoughts?

Regards,

Rich....

Richard Nornhold, PE

 

[MintJulep]

How big a chunck of angle?

Should be easy enough to get 90 degrees on a stock angle by grinding or milling, depending on your surface finish needs.

Could you use aluminum angle? It generally seems to be "truer" than steel.

Is shimming an option?

Doubtful that you would be able to get roll forming to be any better or more consistent than stock angle. Hefty tooling and set-up charges too.

 

[CorBlimeyLimey]

Variations in the flat steel thickness & temper could also affect the resulting angle.

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[nornrich]

MintJulep,

We thought about milling and grinding, but want to keep this as cost effective as possible. We thought if we can get spot on with roll forming, then we avoid machining time.

Regards,

Rich....

Richard Nornhold, PE

 

[unclesyd]

You didn't mention the material you are concerned with but my experience with CS has been you have to machine one leg to get close to 90 degrees and this in itself requires a little preselection of the angle.

It will take some setup to roll at 90 and keep the straightness under control. I would imagine that you would have to under or over roll and on the second pass correct the angle.

We purchased some precision aluminum equal leg angle at one time. The material was used for optical benches.

A little food for though if you are using CS in the lighter gages you might give these people a call.

http://jssteel.com/index.asp

 

[GregLocock]

Check out getting your own aluminium extrusion made. We had some small semicircular shells about 2 inches across, with some fancy features, the tool was $2000, the quality was exceptional. All we had to was cut them to length and the part was complete.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IFRs]

Using a press brake and a bottoming die might get you a good 90 since you can mash the metal pretty hard. Aluminum extrusions have mill tolerances as well. They are pretty well described in the Aluminum Association Design Manual. Steel and stainless steel extrusions are also available. Material variability will always be an issue with roll forming or air bending. Less an issue with bottoming dies. You might also want to check out "Ready Bender" at

http://www.readytechnology.com.

 

[bladeblaster]

I would agree with using precision aluminium extrusion if this has teh required strength. You will get a much more consistent angle.

Bladey.

 

[bear9298]

Roll Forming is not for heavy steel forms, usually lighter gauges of steel/aluminum as in sheet metal. You would not get a perfect 90. There would have to be over bending, no way to assure 90. From the sounds of it you are not looking at high volume therefore roll forming would not be cost effective. Stay with exturded as mentioned above.
Good luck

 

[dimjim]

If you are trying to do it in one pass, I doubt
you can control it. Do you have the options
of multiple stages where you can tweak the
process after several test runs?

 

[deanc]

For roll or die forming a lot of it depends on your size and if it is "leg in" or "leg out". There are also different shapes of ange iron.

If you just have a few pieces call around to your local Job Shops. Lots of time they are listed under welding or boiler repair.

You may be surprised.