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Robert LaLonde
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I've about decided that when the current high speed spindles on my small mills start acting wonky I'll replace them with some ATC spindles with the ISO20 taper. I probably won't build a proper ATC carousel or even a fixed stand. I just want the fast tool changes and repeatable tool heights using the tool table built into the control software.
In my searching I noticed there are 400Hz and 800Hz spindles rated at the same net power and peak RPM. A little digging shows the 800hz spindles are 4 pole and the 400Hz spindles are 2 pole. That's exactly as I figured. Not accounting for motor slip 60RPM per Hz is normal for 2pole motors and 30 for 4 pole.
Now some folks may say it takes a special VFD for the 4 pole motor, but some research shows many reasonably priced VFDs have the capability to produce higher frequency output. Its just that 400Hz equipment is so common.
Now I think the 4 pole motor will have more torque at lower RPM, but I'm not sure. Its seems like it should even if it has a similar linear horsepower curve to the 2 pole motors. I know my 1.5KW spindles still have some ability to cut down to about 8000RPM. Its fractional horsepower, but its consistent and reliable if I plan my cuts accordingly. Most of the time it makes no difference to me really. I tend to small cutters at or near maximum RPM. By extension do you think I would have similar net power at 4000 RPM with a 4 pole high speed spindle?
There are times when it would be nice to get the surface speed down a bit more. I recently found myself having to finish some steel parts on the little high speed mills. (My big mill lost an axis motor) I was able to do it, but sometimes there was a light show and boy howdy was it hard on tooling. If I could shift the torque curve up with a 4 pole 800hz spindle for those rare occasions when something goes sideways on another machine and I have to get a job done I will go that way. They are expensive spindles, but the difference in cost is negligible.
In my searching I noticed there are 400Hz and 800Hz spindles rated at the same net power and peak RPM. A little digging shows the 800hz spindles are 4 pole and the 400Hz spindles are 2 pole. That's exactly as I figured. Not accounting for motor slip 60RPM per Hz is normal for 2pole motors and 30 for 4 pole.
Now some folks may say it takes a special VFD for the 4 pole motor, but some research shows many reasonably priced VFDs have the capability to produce higher frequency output. Its just that 400Hz equipment is so common.
Now I think the 4 pole motor will have more torque at lower RPM, but I'm not sure. Its seems like it should even if it has a similar linear horsepower curve to the 2 pole motors. I know my 1.5KW spindles still have some ability to cut down to about 8000RPM. Its fractional horsepower, but its consistent and reliable if I plan my cuts accordingly. Most of the time it makes no difference to me really. I tend to small cutters at or near maximum RPM. By extension do you think I would have similar net power at 4000 RPM with a 4 pole high speed spindle?
There are times when it would be nice to get the surface speed down a bit more. I recently found myself having to finish some steel parts on the little high speed mills. (My big mill lost an axis motor) I was able to do it, but sometimes there was a light show and boy howdy was it hard on tooling. If I could shift the torque curve up with a 4 pole 800hz spindle for those rare occasions when something goes sideways on another machine and I have to get a job done I will go that way. They are expensive spindles, but the difference in cost is negligible.