hi   
does the way exist for regulating the feedrate with the potentiometer? 
a card hardware can be built for this function? 
thanks 
regards 
moreno

Yes you need an analogue input, I use my PLC but another way is the PoKeys and I believe the ModIO.
Hood

ok thanks Hood   
too much difficulty for my abilities.   
regards

It is not difficult but you do need additional hardware.
I am sure you would get plenty help if you needed it.
Hood

is it a hardware difficult to build? 
or are there to sell in commerce? 
I understand enough of electronics. 
I have made some breakboards and driver for my cnc. 
thanks 
regards 
moreno

Afraid I have no idea how easy it would be to build as I have no experience with electronics except for very basic stuff.
The PoKeys can be bought which has 55I/O of which 3 can be used as analogue inputs to Mach. Also as said before I use a PLC on my machines and have analogue input modules, so that is another option but a lot more expensive if all you are wanting is analogue inputs.
Hood

I didn't know what this existed. 
http://www.poscope.com/product.php?pid=2 
very interesting thanks 
regards 
moreno

They also do the one with terminals already fitted is what I bought but I suppose it depends on how you want to intergrate things whcih would be best.
Hood