noob question; G540 and high speed Nema34

[WalkerYYJ]

Hi all, sorry for this rather low level question here but I am still trying to get my head around how one calculates ideal motor/controller pairings...
I have built a gantry style router table 9'x5' out of steel. Both the X and Y are driven by 3/4" ready-rod. The system is set up to be driven by 4 steppers (2x, 1y, 1z)

I had originally bought a cheep controller and 4x Nema34 motors (878oz) off of ebay (china) to drive it. However after about 20 minutes I ended up buying a G540 as the controller from China was total garbage. I have managed to get the motors to "kinda" run but ran into some very strange issues where i could only get 3 of the motors to run at any one time without the G540 going into safe mode. I could get any combination of the 4 motors to run so long as I didn't have more than 3 plugged in at once. It would on VERY rare occasion go to lock up with 4 and even rarer would move but as soon as a load was applied to one of the axis the 540 would shutdown. it "shouldn't" have been a problem of power as all 4 drives were resistord down to 3.5amps. Anyway after much swearing and trouble shooting with the folks at Gecko I am hoping that new drives of higher quality will fix the problem.

I have a 20amp 50V power supply from Keling KL-5020 and have already drilled mounts for Nema 34 steppers.

Now onto the question: What would make a good mate for the G540 in regards to a Nema34 mount? I would like something relatively fast as at the moment it takes a good 3-4 minutes to jog the full length of the table, but I am thinking that a high torque 34 wired in parallel is going to be a little outside of the 540s amperage range...

I was looking at the following as some options from Keling:
KL34H295-43-8A
KL34H280-45-4A
KL34H280-45-8A

But to be totally honest I have no idea how big of a motor I need and I have no clue as to how one is meant to determine speed from these specs as most of the motors don't have speed graphs....


So I was hoping that someone here who knows more than I (which is probably everyone) could suggest the best motor match for my situation OR is this job simply too much for a 540?

Thanks a ton!

[ger21]

Imo, the G540 isn't really suitable for Nema 34's, if you want any kind of speed. And, the only fast Nema 34's are the high current ones, usually rated at 6 or 7 amps. And with those, the less torque they have, the faster they are. As motors get larger, their usable top speed decreases.

What is ready rod?? All thread? Is it 3/4-16? If so, you're not going to get any speed no matter what you do. All thread is only about 30% efficient, so you're wasting 70% of your power in friction. And the rpm required to get high speeds isn't available from steppers. What you really need, are screws with 2 turns per inch, rather than 16.

What you need to do, is determine what kind of performance your looking for, and then determine what components you need to achieve those goals. Screws, motors, and drives all need to work together as a matched system to get good results.
Realistically, you should probably be using rack and pinion rather than screws for a machine that size.