BP 2J 1 1/2 Speed Control Question

[CJC38]

Hello,
As the Title says I have a BP 2J 1 1/2 head and I am installing a 3 HP VFD. My question is - Which would be better for the machine, to adjust the speed with the VFD or the Vari-Speed head? Thanks

 

[rons]

Set the VFD to 60Hz and use the Vari-speed. This what I would do.

Set the VFD to some intermediate frequency and set the Vari-speed in the middle range. Adjust VFD up/down. You would need a RPM readout. Or a calculator.

 

[CJC38]

Sorry for the late reply - I didn't get notified that you made a response. So is it easier on the mill to just use the vari speed and leave the vfd set to 60hz then? Your answer said both -
Thanks

 

[mksj]

You are best setting the spindle speed with the Vari-speed for several reasons, a mechanical speed reduction system gives you a better mechanical advantage (torque) vs. reducing the motor speed, the other thing is that using the Vari-speed in one position will wear it unevenly more quickly if you just were to use the motor speed control. So general recommendation is use the vari-speed for most of your speed changes but the VFD can be used for smaller speed changes. The Vari-Speed drives wear out and can be expensive to repair, it is not uncommon to put a larger motor on the head 3 or 5 Hp, convert it to a single belt speed with a 1:1 drive and use that with the back gear for low speed. I prefer to use in inverter/vector type motor because they can easily run from 20-200 Hz, so very wide operating range. A larger Hp makes up the power loss when you are running it below the base speed of 60 Hz. I have done and also helped a number of individuals with the conversion.

 

[CJC38]

Great! Thanks for the explanation - much appreciated

 

[eKretz]

I generally run my 3 HP Wells Index at about 45-50 Hz, it's a little quieter there. Then I use the machine's original variable speed control for adjusting RPM, unless I need to go slower than the low end of the range (uncommon). I don't worry about the original speed indications being off as I added a digital tach

 

[CJC38]

Great, thanks for the reply! I didn't think about a separate tach - good call