Rotating Ball nut

[drumsticksplinter]

I'd be wary of compromising rigidity for weight at all. It's much more important to have a strong machine than a fast machine.

I don't think I have compromised the rigidity really, the machine will be fairly heavy duty, but I've tried to use aluminium components where I can to help keep the weight down. I agree that the speed isn't as critical as a strong structure.

Well, I had one ballscrew that was very bent, of course when I bought them they were all packaged up, so it was hard to see that they could have been bent. I've managed to straighten the worse one almost completely, but am awaiting loan of a friends press to enable me to straighten it further. I'm wondering if I could get the ballscrews under tension whilst on the machine by tightening both ends, and hopefully pulling it straight?

[Swarfing]

You will have a problem pulling it straight. the only reliable method is to press it out. small amounts at a time, mark and check against a flat surface.

[paulus.v]

To Paulus, That indeed is very interesting and also worrying for my 12Nm motors. I was looking at the 150v drives to start with, but I got a guy in china to spec the drives and power supplies to my motors, like he did on a plasma table I recently built and he recommended a 68v 400w system. He also sold the 150v drives btw... However, I do think myself these would work best and would save having to buy power supplies for every drive.

You need to find your motor specs in order to choose the right drive. My 150V was only a guess! If you have the 68V 8A drives is better to get better steppers for them, up to 5.7 amps per phase and the inductance lower than 4.4mH. Probably will be at half the length of the 12Nm therefore near to half the holding torque and inertia.

I was searching the last two days for Nema34 stepper for my machine and found some weird things. I will post tomorrow on my build log.