Getting a 1440GT (Which VFD, and other small questions)

I don’t remember seeing this brought up before, with the foot brake on there I’d want to turn the VFD off when it is pushed if you leave it like a stop then the VDF will fight the brake. I know people used these on the 1236t and 1340gt that do not have the mechanical brake, but I’d be scared to. E-stopping with the drive stops the mass through the gear train, I’ve seen what can happen to equipment when doing it just one time. Slow stops are one thing an E-stop is another.

Read the manual carefully there will be different ways to stop it know the difference between them, there may be a normal stop that may ramp down, a stop that might be called an Estop that electrically stops the motor and then an off that disconnects the output from the drive.

On a lathe with a foot brake you want Off (disconnected) and the carriage switches to a slow ramp.

I have seen E-Stops on a drive that disconnect the drive and something else that will do a hard stop of the motor.

Hopefully you get the idea.

Phil
 
Todd727 said:
I have a question about the braking resistor. I don't understand why it is listed as a must add. The VFD has a built in braking resistor, which will slow the lathe faster than the single phase cutoff does. For emergency stops, the foot lever has a friction brake. I can understand if someone WANTS the lathe to stop faster, but I don't see that it is required.
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A braking resistor is only required if you need to stop a high inertia load from a high speed fast. The VFD has the ability to absorb some of the rotational energy. My normal mode of operation is coast to stop, and when threading I have the deceleration set to 1 second. I have tested my 1236T up to 900 rpm with my 8” 4 jaw chuck and don’t need a braking resistor on my Teco CV7300 VFD at 0.5 deceleration time.

The advantage of coast to stop is if something is preventing rotation of the spindle, coast to stop will stop immediately, possibly preventing damage. Using deceleration, the VFD will want to continue to drive the spindle for the duration of the deceleration cycle, or until it trips out.
 
Phil_C said:
I don’t remember seeing this brought up before, with the foot brake on there I’d want to turn the VFD off when it is pushed if you leave it like a stop then the VDF will fight the brake. I know people used these on the 1236t and 1340gt that do not have the mechanical brake, but I’d be scared to. E-stopping with the drive stops the mass through the gear train, I’ve seen what can happen to equipment when doing it just one time. Slow stops are one thing an E-stop is another.

Read the manual carefully there will be different ways to stop it know the difference between them, there may be a normal stop that may ramp down, a stop that might be called an Estop that electrically stops the motor and then an off that disconnects the output from the drive.

On a lathe with a foot brake you want Off (disconnected) and the carriage switches to a slow ramp.

I have seen E-Stops on a drive that disconnect the drive and something else that will do a hard stop of the motor.

Hopefully you get the idea.

Phil
Click to expand...
You are 100% correct on that. If you have it set up for a timed deceleration, you would want it to switch to coast to stop so the brake could stop it without fighting the drive.

There are three emergency stop strategies. If you do a controlled stop, you are then supposed to de-energize the drive once it reaches zero speed since you don’t know if the reason for the e-stop is mechanical or electrical. Most of the industrial equipment I worked on had so much rotational energy that decelerating the equipment was not practical, so the e-stop strategy was to de-energize everything since you didn’t know why the e-stop was pressed. If it was for an electrical reason, you would not want the drives trying to slow the machine down, and if it was mechanical, you couldn’t slow it down fast enough to make a difference.
 
The use of a free run command also known as a base block command is indicated in the 1440GT basic VFD install document, this command needs to be issued when the foot brake is engaged and requires replacement of the stock brake switch with a 2 pole model. One side is left as the default wiring which disengages the run command and the other pole is used to send the VFD free run command.

On E-Stop there are different approaches, but typically you want to kill the run commands to the VFD and also stop the machine as quickly as possible. Disengaging input power to the VFD defeats the rapid braking. I do recommend an external braking resistor in this application, it helps to decrease the braking time when needed and also will decrease the risk of getting an over voltage buss error with too rapid a stopping and butting the VFD into a free run shut down.
 
Ischgl99 said:
A braking resistor is only required if you need to stop a high inertia load from a high speed fast. The VFD has the ability to absorb some of the rotational energy. My normal mode of operation is coast to stop, and when threading I have the deceleration set to 1 second. I have tested my 1236T up to 900 rpm with my 8” 4 jaw chuck and don’t need a braking resistor on my Teco CV7300 VFD at 0.5 deceleration time.

The advantage of coast to stop is if something is preventing rotation of the spindle, coast to stop will stop immediately, possibly preventing damage. Using deceleration, the VFD will want to continue to drive the spindle for the duration of the deceleration cycle, or until it trips out.
Click to expand...
Agree and understand that the foot lever has to put the VFD into "coast" or "free-run". That makes sense. In fact the factory foot brake can be pressed lightly to do just that, so the switching is already there. Pressing further will apply the friction brake.

My SB is setup that way with the normal off switch and the emergency stop.
 
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mksj said:
The use of a free run command also known as a base block command is indicated in the 1440GT basic VFD install document, this command needs to be issued when the foot brake is engaged and requires replacement of the stock brake switch with a 2 pole model. One side is left as the default wiring which disengages the run command and the other pole is used to send the VFD free run command.

On E-Stop there are different approaches, but typically you want to kill the run commands to the VFD and also stop the machine as quickly as possible. Disengaging input power to the VFD defeats the rapid braking. I do recommend an external braking resistor in this application, it helps to decrease the braking time when needed and also will decrease the risk of getting an over voltage buss error with too rapid a stopping and butting the VFD into a free run shut down.
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Thanks, I did see a video where someone was dialing in the stop time on a Grizzly and using too short of a time spiked the DC voltage to the point that it went into free run.

I'm still not sure I'm going to convert my 1440E to 3PH, but I will have to set up a VFD for my mill that is coming in as a 3PH machine. One problem I'm going to have is the 240V outlets don't have a neutral, which is going to be a problem for the DRO. I do have 120V outlets right next to the 240V, so I may just plug the 120V equipment into the separate outlets vs. running new wires.
 
Todd727 said:
I can understand if someone WANTS the lathe to stop faster, but I don't see that it is required.
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This guy might disagree with you.

industri5.jpg
 
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