Converting an AMAT25LV

[Lloyd Barnes]

Thanks for the heads up on this. Have spoken with the motor supplier and done some further research.
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Can I check my understanding. As I understand it (be gentle I'm, still learning this stuff!) running the driver for the NEMA34 at 48v is going to generate a much lower torque. Rather than the 8.7nm its capable of, it's probably going to be running somewhere closer to 4.5-5nm. Speed however shouldn't change? Is that right?
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Assuming I'm getting this right, then my options are to belt drive the motor to the ballscrew 2:1 thereby doubling the torque if halving the speed, or up the voltage to the 34 to something closer to the 80v the driver is capable of handling. Rather than rip apart everything I've done, I could add another PSU running 68V and hook that into the NEMA34 driver. As a bonus it would free up some load on the 48V PSU if I ever wanted to add a 4th axis.
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I added the 34 to cope with the added weight of a future power drawbar, but you guys are running the Z axis on 2:1 geared belt with NEMA23? Are you saying the you need closer to 8nm to happily run the Z even without additional weight on it
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Just trying to understand the problem and my options going forward. Have to say there is a tonne of information out there, some of it conflicting. Reading through various sites I've seen people converting the G0704 with 4nm NEMA23 direct driven to the Z.

[Lloyd Barnes]

Made some progress on the enclosure this weekend. Quite a lot yet to do but with luck I'm hoping to get it in primer and enamelled next weekend.
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Have set it up for flood coolant for the future. There's also box section at the rear to bolt the Z column to. If nothing else should be able to hold everything pretty rigid.
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Mill arrives next Saturday so hoping to make a start taking that apart soon.

[Lloyd Barnes]

I'm using the Oldham style couplings from CNC4YOU on my build. On the NEMA23 they clamp around the shaft with no other locating method (the NEMA34 motor has a woodruff key in the shaft, so I'll cut a corresponding slot in the coupler).
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What's everyone's experience using these? Do they slip at all or is there not a problem. There is a flat on the NEMA23 motor shafts, so I can drill and tap the couplers and add a grub screw locking onto the flat if its worthwhile?
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Appreciate any advise

[John S]

Yes Grubb screw as eell

[John S]

Well, stupid phone

[Lloyd Barnes]

Great, thanks John.

[Lloyd Barnes]

Bit more progress over the weekend. Pretty much finished up my enclosure. A 3rd set of rails for the tops of the doors to be added, and some more polycarb for the windows now that I've measured it right! Some final wiring of lights etc and its about there. I've plastered it in sound deadening and its bolted to both the floor and the wall so very rigid. Will be nice to have a bit less cleaning up to do, the Bridgeport fills the whole shop with chips.
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I've also put a fixing in at the rear direct through the enclosure to the wall to give me a strong point to anchor the column to to beef up its rigidity further. I'm planning to add some adjusting screws to help tramming the mill. How well do the columns line up on these little Chinese mills normally? The mounting faces look nicely ground but I've not done any measurements at this stage.
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The mill arrived so starting stripping that down as well. First time I've bought a brand new machine then proceeded to start throwing half of it away!
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[Lloyd Barnes]

Bit of an update. Have started building machine back up.
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Machined the base out to get a bit more Y travel, and generally clean it up. The ways look OK for a Chinese machine but the casting is the typical Chinese effort, bit wibbly wobbly! Had to do some slightly clearancing to the underside of the table where the casting was very uneven to make room for the ballnut mounting. Both axis are now running nicely under Mach3.
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Column also needing machining to straighten up the slot for the ballnut mount which was a little cocked over. That's back in place. Next job is the Z axis motor mounts and ballnut mount and should be somewhere near ready to try some cuts.
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Was going to upgrade the spindle to 5k rpm but I'll need to make some fresh motor mounts for that so might as well get the machine running and use it to make them as a test.

[JAZZCNC]

Thanks for the heads up on this. Have spoken with the motor supplier and done some further research.
P
Can I check my understanding. As I understand it (be gentle I'm, still learning this stuff!) running the driver for the NEMA34 at 48v is going to generate a much lower torque. Rather than the 8.7nm its capable of, it's probably going to be running somewhere closer to 4.5-5nm. Speed however shouldn't change? Is that right?

Ok seen as nobody answered this here goes.! . . . . However first let me point out that suppliers will always want to sell you what they have in stock or highest profit margin they'll never recommend what's best for you if they don't have it on stock.! . . . So if today they have 48V psu's then "This what you need Sir".!!!

Torque and speed are both proportional to Voltage so both will be affected to some degree. However low voltage affects speed more than torque esp if Motor inductance is high, which is often the case with larger motors hence why 23's are often used.

The higher the Inductance of the motor the more voltage you'll require to get the same speed/torque than motor with lower inductance. Then we have how the motor is connected to factor into the mix.! . . Bi-polar Parallel or Series wired.?
Most large motors are 4 wire motors internally wired in series which means they'll require much more voltage than 8 wire motor which can be parallel wired.

Series wired motor will provide higher torque down low in the speed curve but torque will drop off quickly as the rpm rise. To get higher speeds out of series wired motor will require much much more voltage.
Parallel wired motors will have lower torque down low but carry it much higher up speed curve and in general give more balanced torque/speed curve using less voltage.

So in your case if you'd used nema 23 wired parallel with 48V and 2:1 you'd be better off than using series wired 8Nm 34 running on too low voltage.
Personaly I'd just fit the 34 with 2:1 with what you have got and see how it goes. IF doesn't work out just give it more volts.

[Lloyd Barnes]

Thanks for the explanation Jazz, learning all the time. First off I have to absolve CNC4YOU of any blame. I watched a lot of videos of builds, then dived in and bought stuff myself. Nothing recommended by them. Fools rush in etc!
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All my motors, NEMA34 included, are 8 wire, wired in parallel. At least I got that bit right then! Lol.
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As you suggest I'm going to fit it and see what happens. If it doesn't work then more voltage will be fired at it.

I'm hoping to have it running in a couple of weeks so will be interesting to see what it can do. The columns rigid at least as that's bolted at the top to the enclosure frame.
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Thanks for the advice. Appreciated.