Schaublin 125-CNC retrofit.

RotarySMP wrote:

Could you please send me the link to your lathe spindle speed control comp again, so I can have a look? 

Here is the fancy one that does gear shifts at non-zero speed when the shaft speeds are equal:

 

anfänger wrote:

You also could change the variator motor to a closed loop stepper (Just to prevent step loss) or servo in position mode. 

Oh, yeah, why has it taken so long to come up with that obvious idea

RotarySMP wrote:

Replacing that beautifully integrated little 3Ph variator motor and it's angle gearbox is something I am rather loathe to do. 

I have been thinking about this off-and-on there is a fairly simple scheme that I think might work. 

1) Use a PID to control the VFD, in the normal way. 
2) Use "wcomp" to trigger the variator if the VFD frequency is <40 or >60 Hz. 

There will need to be some interlocking on the second point, ensuring that the spindle is turning at a minimum speed for variator operation, and also possibly blocking during a G1 to prevent unusual behaviour on facing cuts. 

What I see happening is that the fixed speed of the variator shift will either stay in the window (which is fine), accelerate through the window (which provides some automatic hysteresis (though measures might need to be taken to prevent the variator motor reversing at that point, perhaps a function to lock-out the variator for a second once it has operated?) or "chase" the window up or down to the required speed (which is also fine) 

And, writing this, I am now wondering whether enabling the variator based only on vfd-at-speed is an option. So the VFD does the speed control, then once up to speed the variator optimises the torque.