My first PCB using UC300ETH and UCCNC

[cncdrive]

But if you look at the specifications I found that all have the same 6000rpm as minimum rpm. I have aalso used mine much slover than that but that's another thing.

Yes, I found out the same in the specs sheets, but the water cooled spindles can run down to about 3000 RPM without much heating up and without loosing too much torque.
They loose torque about completely at about 1500RPM, below around 3000RPM as you lowering the speed more and more the torque starts dropping exponentially.
I think they still don't heat excessively because the recirculating water chills the motor really good.
I remember once we had a pump failure in one machine and it worked without the pump operating for about a full day and the motor still did not overheat, it did heat up, but not excessively, the still water inside the motor and in the hoses still gave enough cooling.

[A_Camera]

But if you look at the specifications I found that all have the same 6000rpm as minimum rpm. I have also used mine much slower than that but that's another thing.

Yes, I found out the same in the specs sheets, but the water cooled spindles can run down to about 3000 RPM without much heating up and without loosing too much torque.

I think they lose torque equally, so in that respect there should be no difference. Of course, if one would excessively overheat that one would lose torque faster, but at 3000rpm the fan works still pretty well so it will take a long time before an air cooled spindle excessively overheat.

They loose torque about completely at about 1500RPM, below around 3000RPM as you lowering the speed more and more the torque starts dropping exponentially.
I think they still don't heat excessively because the recirculating water chills the motor really good.

The fan efficiency degrades below around 5000rpm but still very good even at 3000rpm.

I remember once we had a pump failure in one machine and it worked without the pump operating for about a full day and the motor still did not overheat, it did heat up, but not excessively, the still water inside the motor and in the hoses still gave enough cooling.

...OK, but I don't think it is a good idea to run them without cooling pump. Also, the heat depends on what you were cutting as well, and also on the rotation speed.

Anyway, if I needed a spindle which must run at slow speeds I would either gear it down from high RPM or would get a spindle designed for low RPM. These spindles are designed for high RPM, no matter if they are air or liquid cooled.

[zymurgy42]

My point was that you can program the VFD to supply more low speed torque.

See: http://www.cnczone.com/forums/spindles-vfd/236092-huanyang-vfd-v-f-curve-low-speed.html.

Hence the requirement for cooling. Not sure if the air cooled ones would cope.

Gordon.

[A_Camera]

My point was that you can program the VFD to supply more low speed torque.

See: http://www.cnczone.com/forums/spindles-vfd/236092-huanyang-vfd-v-f-curve-low-speed.html.

Hence the requirement for cooling. Not sure if the air cooled ones would cope.

Gordon.

Did you read the last post in that thread?

I don't know the HY but my VFD is SVC type and in vector control mode the torque is kept but the spindle gets hotter, which is normal at low speed, but it works without any problems. Anyway, like I said, these motors are designed for high speed. Period.

[zymurgy42]

Period.

OK