how to use vfd for old cnc mill

[machinehop5]

...I see looking at the Plug wiring diagram that there were Optional Spindle drives for the Lagun 250 and maybe yours is prewired from factory.... if you look around the (TB's) wires to control a VFD are maybe present already.
Wire numbers 77(speed at zero), 79 and 80(spindle in out), 33(spindle at speed), 35(spin fault), these next two probably are going to the CR's already 61(forward) and 64(reverse)

[jaysihn]

i'm trying to get comms going between my pc and the control. should i move the question to a different forum or keep going within this thread?

[BBMNet]

i'm trying to get comms going between my pc and the control. should i move the question to a different forum or keep going within this thread?

Hello.

There is no harm in asking someone else.

New ideas and points of view can give you more options so that you can take what´s better for you.

Just remember that no answer can´t be absolutely correct for you situation without actually checking your process insite. It´s like asking a doctor to prescribe you over the telefone line just by telling him what you feel.

I myself am suscribed to other forums so that I can get different ideas.

In my case I´m suscribed to some electronic forums, one programming forum, one quilting forum and one Microchip forum. It has always given me different ideas that have helped me to solve different problems.

And then again you can always give your points of view to help others.

Best regards.

[machinehop5]

...start a new thread. can always come back to VFD topic when youre ready too.

[machinehop5]

That particular motor that you have is rated at 6000 RPM max, I have the identical motor on my mill. I would not run it over 4500 RPM. I'm guessing the spindle would take 6K RPM with no problem. If you need higher than that, then time to add an auxiliary spindle.

....@the spindle.sounds about right at 120hz

[Al_The_Man]

Baldor have made Vector/VFD rated motors for some decades now, and that model is listed as Insulated bearings, which I assume are ceramic.
Al.

[jaysihn]

Baldor have made Vector/VFD rated motors for some decades now, and that model is listed as Insulated bearings, which I assume are ceramic.
Al.

do you happen to have a link to where you were looking at the specs for this motor? Or where you see that it says insulated bearings?

[mactec54]

do you happen to have a link to where you were looking at the specs for this motor? Or where you see that it says insulated bearings?

It would be easy for you to check with a meter just do a continuity test, Rotor ( motor shaft ) to the Body of the motor

Normally when they state this they have added a brush which shorts all the rotor voltage to Ground instead of going through the Bearings it would be very rare that they install ceramic bearings on a standard motor like this they did experiment with a plastic bushing that isolated the Bearings also, but the Brush is what they went with and are still using it on selected motors

[jaysihn]

so i did some digging to find the wires that correspond to spindle fwd and spindle rev coming from the cnc controller. i found pins 61 and 64 which seem to be 24V logic pins. they go into some relays which have 120V output that feed the main contactors. I believe the VFD logic for the fwd / rev pins is analog 0-10V..

what would you guys recommend I do to tie those 24V logic pins to the VFD? Can I just make a voltage divider to give a fixed 10v to the VFD and let it turn the spindle on to 60Hz? I noticed in the schematics there is a spot that says jump pin 20 to 21 only if you have a programmable speed motor. how would the motor have been controlled with the variable speed option? the three phase power goes through the contactors and then right to the motor so i dont see where any frequency change would be happening. My controll console has a spindle speed override that goes from 50 to 100% - I dont know if it was actualy hooked up.

[machinehop5]

....quick question. does the "S0000" Display change if, you program a Spindle Speed?

[Jim Dawson]

The forward and reverse are most likely 10V digital. This only controls the On and Off (and Fwd/Rev) of the VFD, not the speed. Your VFD manual should have the wiring diagrams, and programming instructions.

I'm sure there is an 0-10V (and possibly a +/- 10V) analog input to control the speed also. This could be programmed to work with an external input, but for the moment just setting the VFD to 60 HZ from the keypad would be the best.

If you remove all of the original 3 phase wiring from the spindle motor contactors, you can use them to switch the Fwd/Rev digital inputs of the VFD. Leave the 120V contactor coil wiring intact. This will allow you to use the original control as it is.

I expect the variable speed control was an option that your machine did not have, thus would not have the installed hardware.

[jaysihn]

....quick question. does the "S0000" Display change if, you program a Spindle Speed?

ya, it accepts the S command that comes in with my code. I just dont think it does anything with it.

[mactec54]

so i did some digging to find the wires that correspond to spindle fwd and spindle rev coming from the cnc controller. i found pins 61 and 64 which seem to be 24V logic pins. they go into some relays which have 120V output that feed the main contactors. I believe the VFD logic for the fwd / rev pins is analog 0-10V..

what would you guys recommend I do to tie those 24V logic pins to the VFD? Can I just make a voltage divider to give a fixed 10v to the VFD and let it turn the spindle on to 60Hz? I noticed in the schematics there is a spot that says jump pin 20 to 21 only if you have a programmable speed motor. how would the motor have been controlled with the variable speed option? the three phase power goes through the contactors and then right to the motor so i dont see where any frequency change would be happening. My controll console has a spindle speed override that goes from 50 to 100% - I dont know if it was actualy hooked up.

So not much to change for the FWD and REV it the relays are switched by the control then you can use the output of the Relays this is just a switch with no voltage needed so the connection to the VFD FWD and DCM will have no Voltage on those lines

So the control will activate the Relay and then the relay will turn on the VFD Drive No Voltage Needed between the relay output and the VFD Drive if you have any voltage you will fry the VFD Drive connections

You may have to change the Relays as they where for switching the motor contactor so may be way bigger than needed and have nasty switching action

[jaysihn]

Thanks Jim, I think you are right about the 10V digital instead of 0-10 analog. Its odd, but i can't find anywhere in the manual that actually specifies the logic level for those pins. the manual does show that you can select a 0-5 or 0-10V analog for some other pins.

I agree that at this point in my journey, i do not need to try to get speed control through the control. I do want the on/off with the E stop, machine on, and spindle on switches all working though.

I've removed all the 3 phase wiring from the contactors already but i dont see how i can use anything of the signals at the contactors to control the VFD since they are all AC.

I've drawn up how i think the system works toda,how i thought i might be able to wire it using voltage dividers, and finally my prefered method using the 24V logic to trigger relays that use the VFD's 10V output to trigger the fwd/rev pins.

[jaysihn]

So not much to change for the FWD and REV it the relays are switched by the control then you can use the output of the Relays this is just a switch with no voltage needed so the connection to the VFD FWD and DCM will have no Voltage on those lines

So the control will activate the Relay and then the relay will turn on the VFD Drive No Voltage Needed between the relay output and the VFD Drive if you have any voltage you will fry the VFD Drive connections

You may have to change the Relays as they where for switching the motor contactor so may be way bigger than needed and have nasty switching action

You are saying to connect the power input for the vfd to the existing contactors? How would I be able to change directions? This would add a long delay between the m03 command and the spindle coming on.

Or are you saying to take the vfd output and run it through the contactors? I thought it would fry the vfd if I put a switch between the vfd and motor.

[Jim Dawson]

You are saying to connect the power input for the vfd to the existing contactors? How would I be able to change directions? This would add a long delay between the m03 command and the spindle coming on.

Or are you saying to take the vfd output and run it through the contactors? I thought it would fry the vfd if I put a switch between the vfd and motor.

You would not connect to the power side of the VFD, but rather the control side. The contactors are just a big relays, electrically not different than small relays. Not the cleanest switching for the control side, but they work fine.

And under no condition should you use a voltage divider as you show above. The contactors can be used in place of the relays that you show in your drawing #3

[jaysihn]

You would not connect to the power side of the VFD, but rather the control side. The contactors are just a big relays, electrically not different than small relays. Not the cleanest switching for the control side, but they work fine.

And under no condition should you use a voltage divider as you show above. The contactors can be used in place of the relays that you show in your drawing #3

so put 10V output from the VFD to one side of the contactor and then the other side of a contactor back to teh fwd or rev pin of the vfd? I wasn't as comfortable with that just because there are still a variety of other wires going to those contactors that i didn't want to risk screwing up. I figured a couple of DC/DC relays would be safer and cleaner.

Any reason not to use the dc/dc relay option if I want to?

[Jim Dawson]

so put 10V output from the VFD to one side of the contactor and then the other side of a contactor back to teh fwd or rev pin of the vfd? I wasn't as comfortable with that just because there are still a variety of other wires going to those contactors that i didn't want to risk screwing up. I figured a couple of DC/DC relays would be safer and cleaner.

Any reason not to use the dc/dc relay option if I want to?

No problem at all using a couple of relays rather than the contactors. If you are more comfortable doing it that way, then it will work fine.

[jaysihn]

i just looked in the vfd manual again, i think the reason i couldn't find a specific voltage for the fwd rev pins is because they are internally pulled high and all i need to do is ground them to enable.
do you agree?

[Jim Dawson]

Yes. Keep in mind that is not an earth or safety GND. It is a common (or also called Return) for the VFD control circuit and should not be connected to an earth ground. I wish the manufacturers would properly label that common terminal, it should not be labeled GND.