Hi Craig
re book: fascinating, and THANK YOU.
For metals that strain harden like copper, nickel and especially austentitc stainless (300 series) that is a mistake.
I will add titanium to that list. It's 'aggressive' or nothing. Rub it, it heats and work hardens, and you are out the window.
With this heavy copper board I can have a trace only 2.3mm wide having a conductive area of 1mm square. I assure you it is very seductive to be able to make traces that can handle high currents in such narrow widths.
Oh yes!
I had a commercial servo drive PCB like that. It failed: the mfr did not allow for the special needs of the heavy copper layer, and managed to 'dry joint' some of the heavy current connectors. Photo attached.
Cheers
Roger
Hi,
yes your right that slipped through and it should not have.
I do have some sympathy trying to solder heavy copper is tough. If you are trying to solder direct to a ground plane its very hard indeed,
you have to use such a powerful and hot iron that you risk thermal destruction of any component you are attempting to solder. Not only
does the heavy copper conduct the heat away from the joint you are trying to solder but even when you make the joint it stays hot seeming
ages after putting at risk components.
Most of my boards are surface mount and so usually you can arrange that a SMT pad is such that heat does not get sucked away too rapidly.
If you want to solder to a ground plane you have to use a thermal pad, its just about impossible otherwise.
Craig
I think they failed to tin the underside of the 'pins' with fresh solder. All they had was a very thin perimeter around the pin.
In the event, the product line was killed and the company died.
My replacement: Gecko 320 servo amps.
Cheers
Roger
Are these numbers still accepted to be accurate? From what I've heard recently, the aluminum number is near worst case and the steel numbers are near (or past?) best case. I thought 3 CIM/hp was fairly easy to attain in Al. AB tools claims 6 CIM/hp for their Shearhog!
On the other end, I'd always heard about 1 for mild steel.
Is it that modern Aluminum tooling is 'cheating'? Basically violating old assumptions of how milling cutters work. After all, I can remove a lot more than 2.5 CIM/HP with a chop saw (not as chips..)
Hi,
the source I quoted was published in 1979. Paul DeGarmo the author is/was Professor of Mechanical Engineering at the University of California
at Berkeley. I take his work to be authoritive. Whether you choose to believe is your choice.
Craig
If it works, it is not cheating.
Yes, modern tooling for Al is different from older tooling for steel, in design and operation.
Cheers
Roger