Thread: Converting 3 phase star to delta

I don't like the e stop on the mill. The reason why is that it stops everything instantly, and if you are using the powerfeed, it will continue to move the table as the flywheel effect of the motor takes over. The spindle will stop almost instantly as it tries to keep cutting with no power, and then the pressure on the cutter either chips it or breaks it. I always knock the powerfeed to neutral and then use the main switch if in a pickle.
I hope handlebar Phil isn't reading this....his head will explode....again

Did anyone else hear a big explosion

Phil

Well, after playing with the motor/VFD combination, setting up the parameters to my satisfaction and connecting an external POT and some other buttons, I was reasonably satisfied that I had a motor that was going to do what I wanted. It is now time to match the shaft of the motor to the female keyed insert in the top of my geared head mill.

I had spoken about this dilemma earlier and I was hesitant to modify the mill shaft in case I stuffed it or the motor didn't work out. Anyway, after much thought I decided to have a half way bet..... I bored out the mill shaft from 19mm to 22mm, this has left 6.5mm of wall thickness. I am about to turn the motor shaft from 28mm to 22mm which, with the M8 hole tapped in the shaft will leave about the same, 6.5mm thickness. This leaves plenty of meat and allows for the keyway as well.

Boring the mill internal shaft to 22mm was pretty straightforward I put it in the 4 jaw and dialled it in until almost no noticeable TIR, I thought that turning the rotor shaft would be even easier. I placed one end in the 4 jaw and dialled it in to pretty close (< 0.01mm TIR) and placed the pther end in the fixed steady. When I measured the TIR at the other end, with the steady just touching/ supporting the shaft, I had a massive TIR of aver 0.1mm! What the!

So then I adjusted the TIR at the machining end from the 4 jaw and got it close but then the TIR at the shaft held by the 4 jaw was out too!

I then noticed that both ends of the motor shaft have holes which look like they could be held between centres. Turns out that it fits nicely, it must be how they had the thing. Turning it between centres gave me a more respectable figure of 0.03mm TIR, still not great I thought but what else could I do? So I decided to do some research on the good ol' internet on industry standards for TIR of electric motor shafts. Allowable TIR is about 0.001" per inch of shaft. That seems to be the standard for a lot of things! So I guess 0.03mm for a 28mm shaft is acceptable.

Wish me luck!

Simon

Well, frustrated with the.0.03mm runout i decided to try something a little different and probably unorthodox. I marked the high spot and then removed the rotor and carefully emeried the high part of the centre hole. I did this several times and got it down to TIR of 0.015mm. Yea i know i have affected the contact area and geometry of the take up of the live centre area but thought it was worth the experiment. Only taking very light cuts and it seems to be ok.Simon

Hi Simon,
Did you try a dead center?

Stuart

Originally Posted by Stustoys

Hi Simon,Did you try a dead center?Stuart

Hi Stuart. Yep i tried both thinking that perhaps the live centre may have some of its own runout but no it was identical. Simon