Converting an AMAT25LV

[Clive S]

Welcome to the forum Lloyd. My comments would be up the volts on the drives if you can 68V is a good number with AM882 or EM806 drives and it definitely needs to be higher on the nema34.

I take it you are using ball screws.

I have done the conversion on the WM18 and used 23s with belt reduction all round and it runs fine.

Good luck with the build

[Lloyd Barnes]

Thanks Clive

I'm using drivers from CNC4YOU.

5.6A, 50V CWD556 for the 23's
7.2A, 80VDC or 60VAC CWD872 for the 34.

I guess that means my best bet would be to keep the 48v supply for the 23's and add a 68V for the NEMA34 then?

[Clive S]

Thanks Clive

I'm using drivers from CNC4YOU.

5.6A, 50V CWD556 for the 23's
7.2A, 80VDC or 60VAC CWD872 for the 34.

I guess that means my best bet would be to keep the 48v supply for the 23's and add a 68V for the NEMA34 then?

That's the problem that has been highlighted many times on the forum with buying kits.

Personally I would change the drives and built a toroidal transformer type PS.

[Lloyd Barnes]

That's the problem that has been highlighted many times on the forum with buying kits.

Personally I would change the drives and built a toroidal transformer type PS.

No kits here Clive, I prefer to choose parts/screw things up myself

[John S]

Go for 2:1 reduction on the head and you won't need gas struts etc.

[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.

[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.