VFD on Step Pulley Mill

[ChandlerJPerry]

Hey all, just a quick question. I have an Enco branded RF-30 with step pulleys for speed control. Nothing wrong with the setup, but I find the method for tensioning the middle pulley to be a bit of a chore, and generally feel the same about belt changes. This led to my thought of using a VFD to control speed to the motor, however I did realize that this could come with a few problems:

1. The motor will not be moving at it's rated speed if I am slowing down the spindle, which means the fan in the motor will not draw as much air and could lead to an overheat scenario
2. Pulleys also help provide torque multiplication that I could be missing out on by leaving the motor engaged on one position at all times, plus I believe I had read that VFDs lead to torque loss?

Would I be correct in both of these assumptions, and would they be severe enough concerns to make my idea a wash? I can deal with the belts fine, I'm just lazy .

 

[DavidR8]

I changed my mill over to a 3-phase mot and VFD earlier this year.
I went from a 1hp single phase to a 1.5 hp 3-phase with a Teco VFD.

I bought an inverter rated motor that is designed to deal with reduced cooling air from lower speeds.

There is less torque at reduced motor speeds. I run my motor from 35 hz to 90 hz and have no issues with power or motor cooling.

Sent from my iPhone using Tapatalk

 

[Nutfarmer]

Would you still have a back gear on a RF-30 for slower speeds and higher torque?

 

[DavidR8]

Would you still have a back gear on a RF-30 for slower speeds and higher torque?

I still have all the belt/pulley combinations available if I need them.


Sent from my iPhone using Tapatalk

 

[Lo-Fi]

I run a VFD on my step pulley Bridgeport. I still use the pulleys and back gear, but only when I really need some low speed grunt. Otherwise it pretty much stays on the second highest pulley range.

 

[ChandlerJPerry]

Would you still have a back gear on a RF-30 for slower speeds and higher torque?

The RF-30 has no backgear so it's strictly belt changes for speed control. I could still switch belt positions with a VFD if it were necessary, maybe for more torque or similar reasons.

 

[ChandlerJPerry]

I changed my mill over to a 3-phase mot and VFD earlier this year.
I went from a 1hp single phase to a 1.5 hp 3-phase with a Teco VFD.

I bought an inverter rated motor that is designed to deal with reduced cooling air from lower speeds.

There is less torque at reduced motor speeds. I run my motor from 35 hz to 90 hz and have no issues with power or motor cooling.

Sent from my iPhone using Tapatalk

Curious, are you running that 1.5 hp off 110 or 220v single phase? I've been having some trouble determining what the amp draw would be on the single phase side of the VFD when powering a three phase motor. I have a 20A 110v circuit so I can't imagine it would take more than that, but I want to make sure. I think a 1 hp 3 phase motor would be nice on the RF-30. Right now it has a mystery "2 hp" motor that I would assume is original to the machine, but there's no way it actually outputs that much on 110v, which is what it's connected to. I would guess it's actually 1 hp.

 

[cathead]

I too am running a VFD on single phase 240 volts to an Enco 9x42 step pulley mill. I leave the pulley on 850rpm
and use the back gear function for heavy drilling. I'm careful not to run heavy loads at low motor speeds which
would overheat the motor.

 

[machPete99]

If you don't have a back geer setup try to find a 6 pole motor which turns slower (around 1200 RPM) and produces more torque at lower RPMs. You can generally double the the nominal speed of a 4 pole (1800 RPM nominal) or 6 pole motor safely with the VFD. Keep the step pulleys in play as you might need them for extreme situations. Most of the time I run on 2nd step up.

 

[DavidR8]

Curious, are you running that 1.5 hp off 110 or 220v single phase? I've been having some trouble determining what the amp draw would be on the single phase side of the VFD when powering a three phase motor. I have a 20A 110v circuit so I can't imagine it would take more than that, but I want to make sure. I think a 1 hp 3 phase motor would be nice on the RF-30. Right now it has a mystery "2 hp" motor that I would assume is original to the machine, but there's no way it actually outputs that much on 110v, which is what it's connected to. I would guess it's actually 1 hp.

It’s running on a 20A 220V circuit. It doesn’t draw anything close to the circuit capacity though. If I recall correctly the motor draws 5A.

I’ll check the exact specs later today.
Edit: the max motor draw is 4.7A.

If you have any way to pull a 220V circuit I would do it.

Sent from my iPhone using Tapatalk