Quote Originally Posted by zmajmr View Post
I have Emco 220 P, in manual say that max RPM is 6300 , so I went to see what will happen when I try to reach it and vibrations start to increase so I concluded it is better to limit it to 4100. Originaly motor was DC and 4.4 Kw and I use 1.5 KW AC 3 phase, so my motor is little weak but I can use it. Guy that was selling machine had 5 meter bar loader so for that kind of things you realy need big motor, I manage to use 1.5 kw but I saw some situations where more poewr would be good , at leas 3 KW.

Theoretically for use of VFD you should use motor which is constructed for use with VFD which have better insulation on wingdings for higher voltage but other then that if you are not gona use more then 6000 RPM there should be not problems , I rarely go under 1000 RPM so cooling is present all the time, I thought that maybe that will be problematic but it is not, from my experience there is no problems other then to have perfectly balance spindle for such high RPM.
On my 220 P bore is 25.5 mm, for 120 I do not know.

Also google for "vfd shaft current problems", you need to install some kind of protection otherwise your bearings will be damaged in motor.
This is my thread, you will find there my DIY shaft current protection https://www.cnczone.com/forums/verti...86042-cnc.html
Thanks for the heads up, I will read through your thread this evening.

The 220 is the same iron I believe? What's the hardest material you think these things can turn? I've only used it on stainless so far, which it handles easily. I need to run some stuff in en19t (4140 or 4340 I think).

It's a great little lathe anyway, I love it. As said mine was already retrofit when I bought it, it has a no frills Chinese SZGH controller which seems to work well. The X, Z and spindle motors are all encoded, I use it for rigid tapping which it does very neatly. I have some changes I want to make, including a through coolant manifold and possibly automating the tailstock. I will share more info on it when I have chance.


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