[ronderkis]

I have a Bridgeport R2E3 I will be controlling with a ajax controller. I have just put a VFD on the mill (runs great!). Can I just set the gearbox to hi speed and the variable speed pulley to the highest speed and use just the VFD to control both speed and direction, without harming the mill?

[polaraligned]

Yes you can, but you will want to use the low speed range (mill gearing) for the slower cutting speeds. Even though many good VFD's provide the motor with a steady torque output into the lower speed ranges of the motor, you need the gearing (using the head's internal back gear) to multiply torque and provide enough power to the spindle. The low speed gear range is invaluable for cutting hard materials at a slow spindle speed. Keep in mind that you will have to reverse the VFD motor direction when switching to the back gear.

[ronderkis]

I understand all but the "Keep in mind that you will have to reverse the VFD motor direction when switching to the back gear."

What is back gear? I thought I have two gear settings on the top right lever (Low and High)
And why do I reverse directions?

[polaraligned]

When you switch to low speed on the head, the back gear is engaged and the spindle will spin in the reverse direction, hence you need to reverse the direction that the VFD drives the motor. Try switching to the low speed...you will see that the spindle direction is reversed.

[ronderkis]

Ok, you have a way of explaining that makes it easy to understand :-)
What is the procedure for switching to low gear? Should spindle be stopped?
I am using a vfd so I can slow, stop, or reverse direction easily.

[polaraligned]

Stop spindle, switch lever on head to opposite speed, reverse direction of vfd and your are off.....
Sometimes you need to wiggle the spindle a little to help with the gear shift.

[ronderkis]

Do you think this could be done using a solenoid and perhaps setting vfd rotation to about 1 rpm till full engagement, under program control?

[mactec54]

Ronderkis

You must Stop the spindle motor to change from low to high or high to low, you will damage the Drive dogs, if you try & do it with the motor running/moving

[polaraligned]

The lever has to move 180 degrees and it is the type of change that is not easy to automate. I would not want to give up the "feel" of moving the lever and knowing it is engaged properly. You could mount a microswitch to detect what position the high/low lever is in and tell the VFD to set the direction of rotation accordingly. I know it is a pain in the butt to have to stop when going from say a 1/2" endmill in steel to a small drill, but these machines are a big compromise to begin with. $18k can get you a fairly decent VMC....

[ronderkis]

Why a micro switch?
When I asked this question about a micro switch, I forgot not everyone has a encoder on their spindle.

[meatwad]

Doesn't Ajax use some other method of changing the spindle speed by using the original pulley system?

Seems the original spindle motor was designed to always run at full speed to keep cool. Have you had any issues with overheating the motor?

[polaraligned]

Doesn't Ajax use some other method of changing the spindle speed by using the original pulley system?

Not that I am aware of or have ever seen on their website. Only speed control is the original mechanical design or a VFD.

Seems the original spindle motor was designed to always run at full speed to keep cool. Have you had any issues with overheating the motor?

The original motors are not inverter duty, but I have not heard of people blowing them out on a regular basis when using a VFD. The original gearing is there and I use it for slow speeds and larger cutters. You loose power at the spindle using a VFD to slow the motor down. There is no replacement for gears...

[mactec54]

meatwad

I remove the standard motor fan when using a VFD, the fan on the motor is of no use at low or high RPM, a 4" fan on top is all that is needed, this is turned on when the VFD turns the motor on

[ronderkis]

Great idea and easily implemented!
Thank You.