Beauty in The Beast: Webb 5BVK Barn Find/Conversion

[Charlieman22]

It would be possible to electrically ''lock'' an axis by powering up a drive. Enabling only the drive you want to lock would be a matter of sending the enable signal to only that drive. The would require that the balance was set very precisely so that the motor doesn't ''drift'' when no command voltage is present.

Ok - humor me for a moment on this one.
(not that I didn't like your bike brake/ don't put idea past me!)

Asking for a friend:
Let's say that I am using a boring head - so I don't want movement of any kind in either X or Y.
The head has a pretty good lever hanging out the side with a cutting tool mounted.
That 5 hp motor has no plans to be deterred should my work move...

What is the science behind electronically locking my axis servos?
That is - how is it done?
Is the controller sending plus/minus pulses constantly reversing itself?

Oh - BTW - pic of this evening's arrival.
I love new toys.

 

[JimDawson]

What is the science behind electronically locking my axis servos?
That is - how is it done?
Is the controller sending plus/minus pulses constantly reversing itself?

With the drive enabled and no commanded movement the motor should theoretically hard lock in place. In reality this ''lock in place'' is a bit mushy. So yes, the controller will send out movement commands to correct any drift in either direction. Those DC motors actually do lock up pretty well, enough so that you can't really feel much movement, but you might be able to see some movement on your DRO, normally in the +/- 0.0002'' range.

Nice package of toys

 

[Charlieman22]

Ok - last lash of this horse.
So is the servo under no power - the tables sitting basically unlocked - but if the table is forced to move from cutting pressure - the controller would fight it with counter inputs?
I had imagined that the motor was somehow simultaneously getting +/- signals, even with no forces on it trying to shift it out of position - thus being "electronically locked".
(vivid imagination).

 

[JimDawson]

So is the servo under no power - the tables sitting basically unlocked - but if the table is forced to move from cutting pressure - the controller would fight it with counter inputs?

That is essentially correct. Assuming the drive is powered up and enabled, if the controller is happy with the position then the controller would be sending 0 volts. If the commanded position agrees with the current position then the controller applies 0V to the drive. The controller only applies a command voltage when the current position does not agree with the commanded position, this is called position error. The magnitude of instantaneous (updated about every 60 micro seconds) error determines the magnitude of the correction voltage that is applied to the command input.

Since your drives are velocity drives, there is another control loop involved from the tach feedback to the drive. If there is 0 velocity commanded, the drive will also apply a opposing voltage to counter any sensed movement. However, this is not as sensitive as the encoder feedback at very low speeds.

The above is the simple explanation of what is pretty much happening. This could quickly devolve into the deep dark hole of motion control theory, where ω /V = [Ka Kt /Js]/[1+Ka Kt Kg/Js] = 1/[Kg(sT1+1)].

 

[Charlieman22]

That is essentially correct. Assuming the drive is powered up and enabled, if the controller is happy with the position then the controller would be sending 0 volts. If the commanded position agrees with the current position then the controller applies 0V to the drive. The controller only applies a command voltage when the current position does not agree with the commanded position, this is called position error. The magnitude of instantaneous (updated about every 60 micro seconds) error determines the magnitude of the correction voltage that is applied to the command input.

Since your drives are velocity drives, there is another control loop involved from the tach feedback to the drive. If there is 0 velocity commanded, the drive will also apply a opposing voltage to counter any sensed movement. However, this is not as sensitive as the encoder feedback at very low speeds.

The above is the simple explanation of what is pretty much happening. This could quickly devolve into the deep dark hole of motion control theory, where ω /V = [Ka Kt /Js]/[1+Ka Kt Kg/Js] = 1/[Kg(sT1+1)].

Chuckle as you may - that is going on my sheet of mill facts.
You let me creep right up to the edge of the hole.
Got a glimpse of a chamfer most don't know exists.
Thanks for letting me prod a bit.
Excellent explanation.

 

[Charlieman22]

Let the entertainment continue.

Extropic put in some extra time with me - to help me untangle some tooling basics.
Starting to understand how you guys spend so much!
We managed to actually stay on topic for most the time - and it translated to some good base building.
Plenty more needed - but big help.
Thanks!

Speaking of chip making.
Got some time in this afternoon between calls.
Outcome is not so bad.
Quill is jogging up and down when told.

Next up when time permits:
1. Control panel has switches that are not connected (only the quill feed speed dial and the joystick for up down motion are). I would like to wire the VFD to the other three switches. Speed control, Forward/off/Reverse nob, and Emergency stop. Below I show the face of the controls, and the backs of the knobs/buttons. Jim - if you aren't worn to the bone yet...
2. DRO install. Considering taking out the angle grinder and just lopping off the big ass display that is there now. I am no fan of the box either - but for the time being - it is functional. It's not like I couldn't just weld the big display box back on if I was to get rid of both boxes. Anyone want to protest before the angle grinder comes out?

Pics below of the front of the machine.
parts slowly being cleaned and re-installed.
Little before and after no the limit switch box - as morale booster.
Long way to go.

Before:

After:


Front of control panel. Only the joy stick and the knob to its right are wired.


Other three knobs/buttons. All 220V







Below is the wiring for the emergency stop.

 

[JimDawson]

I think this will work.

On the VFD, jump +24V to PW

Connect COM to 2 on the E-stop switch
Connect 1 on the E-stop switch to 3 and 4 on the bottom of the For/Rev switch
Connect 3 from the top of the For/Rev switch to S1 on the VFD
Connect 4 from the top of the For/Rev switch to S2 on the VFD

Connect one side of the speed control pot to +10V on the VFD
Connect the other side of the speed control pot to GND on the VFD, this the analog GND, not earth ground (PE)
Connect the center terminal on the speed control pot to AI1 on the VFD
Make sure to set jumper J16 to V
If the speed control is backwards, then swap the +10V and GND wires.

Set P5.01 = 1, S1 = Run Forward
Set P5.02 = 2, S2 = Run Reverse

See P5.10, Terminal Control Mode
Set P5.10 = 0

Run Command Source
Set P0.01 = 1, Terminal

Frequency Command Source
Set P0.07 = 1, AI1

 

[Charlieman22]

Ok - good news - I understood most.
Questions here:

On the VFD, jump +24V to PW Clear

Connect COM to 2 on the E-stop switch Clear
Connect 1 on the E-stop switch to 3 and 4 on the bottom of the For/Rev switch Estop has three colors. Which are you referring to as "1 on the Estop"?
Connect 3 from the top of the For/Rev switch to S1 on the VFD Clear
Connect 4 from the top of the For/Rev switch to S2 on the VFD Clear

Connect one side of the speed control pot to +10V on the VFD Clear
Connect the other side of the speed control pot to GND on the VFD, this the analog GND, not earth ground (PE) I have two GND marked A & B below (and one E). Can this go to either A or B?
Connect the center terminal on the speed control pot to AI1 on the VFD Clear
Make sure to set jumper J16 to V. Didn't understand this. Are there dip switches somewhere? Not sure where Jumper J16 is?
If the speed control is backwards, then swap the +10V and GND wires. Clear

All below clear.

Set P5.01 = 1, S1 = Run Forward
Set P5.02 = 2, S2 = Run Reverse

See P5.10, Terminal Control Mode
Set P5.10 = 0

Run Command Source
Set P0.01 = 1, Terminal

Frequency Command Source
Set P0.07 = 1, AI1

 

[JimDawson]

OK, sorry.

Green to COM on the VFD
Blue to the For/Rev switch

I would use A for the GND for the pot

Not sure where J16 is, maybe that jumper just to the left of the control terminals? I may have an older manual, so maybe they did something different on the newer units. Maybe check your manual.

 

[Charlieman22]

Ok - here it is - hiding in plane site like Waldo.
Manual gives some cryptic advice - I've circled.
Perhaps you can decipher?
Red arrow spots the jumper.


Instructions for how to get to V are a little vague to me