Roll forming question

[Ryoko]

I want to make a small roll forming machine for my garage. I need to bend a strip of .040 5052 alum into a u-channel that's about 3/8" thick and 1/2" tall. It's too small to use a brake and much too long. (It needs to be 80" long.) I have the flat strips on hand ready to be bent. But I'm still working on the machine to do the bending. My question is how many degrees should each roller bend the strip before moving on to the next stage? Each roller stage is 5" apart. The rollers are typically 2" in diameter. (I'd go larger, but the lathe will only do so much.) Hints and tips are welcome.

 

[jrmichler]

Everything I know about roll forming is in the following quote from Manufacturing Processes for Engineering Materials, by Kalpakjian. Proper design and sequencing of the rolls (which are generally mechanically driven) requires much experience and includes consideration of tolerances, springback, tearing, and buckling.

And the following diagram:

Looks like you need to do some experimenting. Have fun.

 

[Ryoko]

I would really like to get it right or at least near right the first try. This project is getting expensive.

 

[Lnewqban]

Could you please provide a scale drawing with the exact shape of the finished cross-section?

 

[Ryoko]

Quick and dirty drawing. Dimensions are for the outside. The aluminum is 0.040" thick.

 

[Lnewqban]

I would try achieving that radius of turn in a few short pieces of the same material first, just to verify that no cracks develop.

 

[Ryoko]

I have bent samples that tight using a die in a press brake without issue. But it's an easy change. IIRC, the recommended minimum bend radius for 0.040" 5052-H32 is 1t, so it should be good.

 

[Lnewqban]

I have found these:
https://www.internationaljournalssrg.org/IJME/2021/Volume8-Issue4/IJME-V8I4P101.pdf

https://www.rollerdie.com/roll-forming/

https://www.researchgate.net/figure...ons-A-Spring-beck-B-Bowing-and_fig1_309312243

 

[Ryoko]

I have found these:
https://www.internationaljournalssrg.org/IJME/2021/Volume8-Issue4/IJME-V8I4P101.pdf

https://www.rollerdie.com/roll-forming/

https://www.researchgate.net/figure...ons-A-Spring-beck-B-Bowing-and_fig1_309312243

The first link was very helpful. It looks like I'm on the right track. It appears I can increase the bend amount to reduce the numbers of rollers needed ... maybe.

 

[Ryoko]

I believe I have the rollers worked out. But finding a CNC service to make them is proving to be difficult. Services in the US are extremely expensive. And the Chinese shops are getting priced out because of the steep tariffs. Is there a solution here? The rollers are 2" diameter and about 2" long. Pic shows a typical female roller.

 

[Baluncore]

But finding a CNC service to make them is proving to be difficult.

You can make the rollers in an ordinary manual lathe. You can modify or replace them when and as you wish, without the expense and delay of an outside contract.

 

[Ryoko]

You can make the rollers in an ordinary manual lathe. You can modify or replace them when and as you wish, without the expense and delay of an outside contract.

In theory, that's true. But it's a Chinese mini lathe which is not known for precision. Plus the rollers need to be carefully dimensioned so the male and female dies fit together well, otherwise bad things happen. If it had a DRO, it would be more feasible. I've made a some test rollers in the past and they are fussy. If they are mismatched, the part won't track correctly thru the machine or you end up with warped pieces.

 

[Baluncore]

But it's a Chinese mini lathe which is not known for precision.

You are playing a game that requires some up-front investment. You might buy a second hand lathe capable of doing the job. It will pay for itself on the first project.

Precision comes from the operator and their measurements. A DRO is nice, but not essential if you have dial callipers. A good Chinese DRO with a couple of scales, is now very low cost.

 

[Baluncore]

If you use steel rollers without mineral oil lubrication, it will probably scuff the aluminium alloy surface. The sapphire coat on the alloy will also wear the steel rollers.

 

[Ryoko]

If you use steel rollers without mineral oil lubrication, it will probably scuff the aluminium alloy surface. The sapphire coat on the alloy will also wear the steel rollers.

Not an issue. This is for a very small run (less than 100 feet). Scuffs are not a problem as long as the aluminum isn't gouged. There's a bunch of additional forming to be done after the u-channel is made.