I watched the video on the bender and half way through the video there is s section where the bending segments are clamped by a magnet this is what I am trying to build , this creates versatility of the bender and allowes multiple bends.
Right, now I'm 100% with you. I have to confess that I only watched the first minute or two yesterday, since the video is 10 minutes long..
It'a a nice machine, isn't it?
So, it doesn't use solenoids at all. It's a full-length, very powerful, electromagnet. I didn't realise it was open-ended, either.
In the middle of the video, those aren't magnets. Just small blocks of ferrous metal that the main electromagnet attracts.
It would be nice to see inside it.
It's probably one or maybe a couple of electromagnets, attached to the inside of the clamping table, similar to my drawing below:-
(You could use a row of them if needed.)
I can't actually help with designing the electromagnets, (never tried it), but maybe someone else can.
Or you could experiment, with very thick winding wire, an iron core and heaps of windings. Not sure about power supply size though. Big.
Edit: Just thinking about it, the top of the clamping table would need to be carefully chosen for low remanence, so that it didn't remain magnetic after the power was switched off. Maybe even a special iron alloy. I'm not sure about that bit.