Need to bend stainless plate. This technique look ok?

[Garwood]

20 pics a day is nowhere remotely close to mass production lol.

For real production you need a real purpose built press.

Dicking with hydraulics and a frame without substantial slideways will make repeatability in production impossible.

 

[RC Mech]

With each post I think we’re getting closer to the use-case and the original design is not ideal.

 

[NewGunPlumber]

For 20 pieces a day? You need a press brake to run the rotary, just get one with a cnc back gauge and forget the rotary. That makes it what, a 10 minute job per day? Or go old school and set two fixed stops, one for each end.

This. . . .don't need to make things more complicated than they need to be. Also have the option of using the same machine for many different jobs in the future

 

[David916]

20 pics a day is nowhere remotely close to mass production lol.

For real production you need a real purpose built press.

Dicking with hydraulics and a frame without substantial slideways will make repeatability in production impossible.

Mass production doesn't mean a lot, it means I'll be doing this process for a very long time.

Define a "real purpose built press".

I have no idea what you are trying to say.

 

[David916]

With each post I think we’re getting closer to the use-case and the original design is not ideal.

Not quite. I replied to your message and asked 2 question which went unanswered.

 

[Garwood]

Mass production doesn't mean a lot, it means I'll be doing this process for a very long time.

Define a "real purpose built press".

I have no idea what you are trying to say.

Presses for forming stuff are built to maintain critical alignment while operating at thier rated tonnage and ram/bed distribution.

A "real" press has slideways, long ones. It's made with tons of iron or steel for rigidity.

 

[Scottl]

Another option might be to use your idea to get close to 90° and then put it sideways on a press to overbend so it relaxes at 90°.

I think a lot of shops would just use a press brake with stops and make the bends in 2 steps.

 

[gbent]

What Garwood is getting at is maintaining parallelism of movement with off center loading. Your single point set up is highly succeptable to off center loading. You may even get variations in material that will cause the punch to cock sideways. This sideways movement becomes self actuating, i.e., it gets worse rather than self correcting. A real punch press uses significant slide ways to maintain parallelism in spite of off center loading. A press brake also has mechanisms to ensure parallel movement when the load on the ram is unbalanced.

 

[Ries]

Personally, I would just be doing 20 a day by hand on the hossfeld, but I have been using the hossfeld for so long that setup, stops, and so on are just second nature for me.
But in a real production environment, I would be going with a horizontal press, not a press brake. Something like this spanish machine would be great. Although there are a good dozen different machines like this from Italy, Spain, Germany, and China out there on the market. The big advantage is how many other things you could use a machine like this in the other 23 and 3/4 hours of a day when it wasnt bending your 20 pieces of flat bar. https://www.directindustry.com/prod/prada-nargesa-sl/product-24785-1823278.html
Or this Hebo, which will clearly handle the material thickness you want. I have a different Hebo machine I bought about 20 years ago, built like a brick shithouse.

Or knock off the Edwards, since Edwards are all really simply made, should be pretty easy.

 

[David916]

Personally, I would just be doing 20 a day by hand on the hossfeld, but I have been using the hossfeld for so long that setup, stops, and so on are just second nature for me.
But in a real production environment, I would be going with a horizontal press, not a press brake. Something like this spanish machine would be great. Although there are a good dozen different machines like this from Italy, Spain, Germany, and China out there on the market. The big advantage is how many other things you could use a machine like this in the other 23 and 3/4 hours of a day when it wasnt bending your 20 pieces of flat bar. https://www.directindustry.com/prod/prada-nargesa-sl/product-24785-1823278.html
Or this Hebo, which will clearly handle the material thickness you want. I have a different Hebo machine I bought about 20 years ago, built like a brick shithouse.

Or knock off the Edwards, since Edwards are all really simply made, should be pretty easy.

Hey Ries, a horizontal press is a great idea. Can definitely use this in my shop. Thanks man, I really appreciate it.

 

[David916]

What Garwood is getting at is maintaining parallelism of movement with off center loading. Your single point set up is highly succeptable to off center loading. You may even get variations in material that will cause the punch to cock sideways. This sideways movement becomes self actuating, i.e., it gets worse rather than self correcting. A real punch press uses significant slide ways to maintain parallelism in spite of off center loading. A press brake also has mechanisms to ensure parallel movement when the load on the ram is unbalanced.

Yeah, the off-center design is what worried me.

Maybe I can make the jig slide left and right by attaching tiny pneumatic cylinders to both the left and right sides of the jig so bend #1 and bend #2 are both center with the ram?

I'm building this robot to bend another part (thin sheetmetal) and can maybe incorporate some features into this jig so it's in alignment with the hydraulic cylinder and I don't cause off center loading, which I didn't previously consider.

 

[Scruffy887]

What is your goal? To build a single use bending machine or make $? Accuracy on any press brake starts with the material, nuther subject. But any CNC press brake will do each bend is seconds. Many older brakes can be fitted with a CNC back gauge as well. The back gauge moves after each bend. The accuracy of the final part is determined by the blank size too. I bend a lot of assemblies and all parts need to be accurate or the assembly just does not happen. Accurate blanks, accurate back gauge, accurate bends. Bob's your uncle.
And the press brake can be used for loads of other things after you did your 10 minutes a day job.

 

[David916]

What is your goal? To build a single use bending machine or make $? Accuracy on any press brake starts with the material, nuther subject. But any CNC press brake will do each bend is seconds. Many older brakes can be fitted with a CNC back gauge as well. The back gauge moves after each bend. The accuracy of the final part is determined by the blank size too. I bend a lot of assemblies and all parts need to be accurate or the assembly just does not happen. Accurate blanks, accurate back gauge, accurate bends. Bob's your uncle.
And the press brake can be used for loads of other things after you did your 10 minutes a day job.

The goal is to make precise parts and remove all potential for error. Speed is not as important but consistency is. I figured if I had a jig that can do both bends at once, all of the parts will be identical.

I spoke to a few cnc bending services and they said the +/- will be 1.5 degrees. That is far too much and I need to do the bending in-house to ensure accurate parts.

A back gauge is not a bad idea. I can probably use a twin rod pneumatic cylinder as a back stop to do both bends. The difference between the 2 bends is 75mm and I found a cylinder that has a 75mm stroke which would be perfect as a back stop.

After I do my 10 minute a day job, then I need to weld the frame onto it and assemble all the parts. I manufacture a product and am building the process for that purpose alone.

I think I'm getting closer to finalizign the design. As I previously mentioned, I have significant brain injury which makes solving new problems very difficult and I usually need to go through a lot of trial and error to solve a problem but I eventually get there. The people on this board shared a tun of useful insight and even though it may not seem like it, it helps a lot. A cnc press brake is not something I can afford but a regular brake with a pneumatic back gauge might be the answer. Took a while to get to that idea and wouldn't have done it without talking about it, so thanks to everyone who took time out of their day to share their insights.

 

[gbent]

You are doing two bends. Skip the moveable back gauge. Build two nests. If the consistency between the two bends is important, you must gauge each bend from the same end. In this situation you can't gauge each bend from the close end, as any variation in length will change the distance between bends. The thickness of the material will effect the angle of the bend in an air bend situation. You may be better off with a bottoming die.

 

[Scruffy887]

Press brake will need about 13 tons to bend that part with a 1" die opening, air bend. More tonnage for bottom bending, even more for coining. The driving factor for consistency will be the material thickness, AND grain direction, AND bend method.
Look for a used 42 ton x 24" Atek Bantam press brake. They do make a 24 ton x 24" brake but you may ruin it bending a 6" wide piece using 13 tons.
Bending sheet metal is 95%exact science and 5% Voodoo. When you run into a sheet that varies in thickness across its width you will respect this.

I was making a storage drawer cabinet from 10 gauge. The side panel was about 26" deep x 36" tall finished. Front and back edges required 4 bends each. First bend was 90 on the money. But only at one end of the part. less than 90 other end. MATERIAL THICKNESS! So I compensated the punch depth at each end of the bend. But I had to flip the part over once on each side. First part was scrap. I went with zero compensation and used a work around to get a good part. 10 gauge may sound heavy but this cabinet had 8 drawers 54" wide inside with 500# cap slides. It was my first project with my new CNC brake and was needed to store the tooling.

 

[BT Fabrication]

The original designs won't work. and a 1mm tolerance is just screaming cnc back gauge. this is childs play in the manufacturing world. spend the $ buy a real press and not the junk hydraulic press idea as you will end up with other parts bent that you don't want bent.

 

[Garwood]

If this is for your own product forget this custom press stupidity and buy a larger size OBI.

Simple obi tool you can build from laminated laser cut plate will form that part in one hit perfectly.

Press brakes are great, but cheap shitty ones are just that. Obi's are cheap. Making a product? You should have obi's.

 

[David916]

If this is for your own product forget this custom press stupidity and buy a larger size OBI.

Simple obi tool you can build from laminated laser cut plate will form that part in one hit perfectly.

Press brakes are great, but cheap shitty ones are just that. Obi's are cheap. Making a product? You should have obi's.

I have two 5 ton OBI presses. What tonnage do you think might be the least I would need to bend 3/16" 6" wide stainless steel plate?

 

[David916]

Ok, would this idea work?

My 5ton OBI press with a 3" wide die opening (material thickness is .1875" so the die opening would be 16x the thickness) and according to the tonnage calculator on Accurpress.com, 4 tons would be required to make the bend.

 

[Garwood]

I was thinking more like 60-75 ton OBI. Preferably back geared.

If you're making a punch press tool, make it to do the job in one hit. Make it idiot proof so you can practically throw the part in the tool and it comes out perfect.