Hey U007D,
thank you very much for sharing all the data and the experience! I’m sure many appreciate this.
However I find it a little disappointing that despite the fact you got a 4-pole spindle which runs with 12,000 rpm at 400 Hz (and still 24,000 rpm at 800 Hz), it gives not more lower speed torque than a 2-pole spindle – it even gives less low speed range at the nominal torque of 0.9 Nm. It is a little surprising that according to the curve you show, the nominal torque only begins at 12,000 rpm:
Even with a standard 2-pole, 24,000 rpm at 400 Hz spindle, you could get 0.9 Nm at (substantly lower) 6,000 rpm:
Mechatron HFS-8022-24-ER20 (2 magnetic poles, 6,000 rpm – 24,000 rpm)
So at the moment I see no benefit to buy the spindle you show, especially for milling steel with high torque at low speed.
And of course as you stated, the 4-pole spindles you considered earlier in the thread, while being surely more expensive, give high torque at much lower speed, as shown here e.g. 1.6 Nm at 3,000 rpm:
HFPM-8022-24-ER20 (4 magnetic poles, 3,000 – 24,000 rpm)
or even 1.9 Nm at 1,500 rpm:
HFPD-8015-12-ER20 (4 magnetic poles, 1,500 – 12,000 rpm)
This shows me one thing very clearly: It is not only the number of magnetic poles that makes the difference here, it also depends very much on the manufacturer’s skills and experience in designing the windings and the rotor cage.
Yes, this was often discussed here. That is why I think of replacing the entire Z assembly by a universal Z assembly. I am not surprised that when milling steel, you encounter chatter, which I would see caused by this.
But I think for milling steel, the Onefinity is also not the right machine for another reason: Because its linear bearings are ball bearings. The cnc-step High-Z (discussed here, here, and here) is a universal machine explicitly made for milling steel. Its main difference is that it has plain bearings (instead of ball bearings) which run on its steel rails.