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Swap the Z drive with the X or Y.? If it follows the drive, you have your answer.

If that does not shed light on the problem, swap the motors.

Does this occur in a rapid move? Does it occur in a feed rate move?

Did anyone mess with any of the other pots such as the gain??

-----Original Message-----
From: Pathwizard <willg@...>
To: [email protected]
Sent: Thu, Feb 9, 2023 4:19 pm
Subject: Re: [BridgeportMill] V2XT help needed

Well, I still have a problem.? The problem is back to the original problem I had that led to me breaking the encoder and the circus that followed.

The problem is that the Z axis control is not stable.? When I command it to a certain position, it overshoots.? When I jog it, it overshoots the target and comes back to the target.? Its an underdamped system.? The Y and X still work correctly as they used to, but this z axis problem is new.

?The machine had been sitting 2 or 3 months unused, and when I fired it up, this appeared.? Then I broke the encoder, and then I send the Z servo to a repair shop in Chicago who examined it and told me the encoder was broken and the armature resistance to chassis was low.? Since then I replaced the encoder and cleaned the servo by flushing it without disassembly.? I don't have a way to measure the resistance.? My ohm meter says the resistance is infinite as it should be, but it said that even when they said it was low, so I think its just because I don't have the right instrument.? I don't think that low resistance is the cause of this problem.

Has anyone seen this type symptom and can suggest?? Video attached.

Thanks

Will Grant

===========================

On 2/8/2023 2:24 PM, Pathwizard wrote:

Thanks George.? Seems like I got it.? I opened the space between the home and limit and it seems to work now.? Haven't cut anything yet, but I'm quite hopeful.

Thanks again.

Will

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On 2/8/2023 1:36 PM, George Wroclawski wrote:

You have to understand how a machines homes.

Switches are inaccurate.

So what happens is the z starts to come up.

It makes the home switch.

The control now is aware to look for a marker pulse. This a very accurate pulse that occurs one per revolution of the motor/encoder.

Once the control sees that it starts counting.

Do not ask why but the BOSS 8 and 9 and the V2XT will count .350 inches and stop.

Thus the over travel limit stich must be set to allow that.

What can go wrong?

Do you have the marker pulse? It will never home without it.

The marker pulse and home switch occur simultaneously. (Murphy's law). Then home will vary .200 inches depending on temperature and snot on the switch. Is the switch is delayed a few degrees of rotation, the marker pulse will be missed and the motor will make an additional revolution.

I hope this helps.

George Wroclawski
Service Manager
McDaniel Machinery Inc.
Mobile : 1-205-937-2066

On Wed, Feb 8, 2023, 11:20 AM Pathwizard <willg@...> wrote:

I have an update and request for more help.

I finally got the encoder installed and wired so that it looks like the old one.? I no longer get overflow or underflow alarm.? When I enable the drives, nothing moves, as it should be.

When I "Home", the z axis slowly moves up, just like it should.? However, it goes right past home and hits the limit switch and throws the alarm for Z limit.

I've carefully checked the home and limit switch and its connections all the way to the AUX board and everything looks fine.? Home switch is Normal Open and closes correctly.? When the switch is open, I get about 24V across it, as expected.? I looked at the AUX schematic and this input is drained down to about 3 V and fed directly into the 8 bit microcontroller on that board.? So it would point to a bad microcontroller or AUF board.? Hopefully not.? Any suggestions?

Thanks

Will Grant

===========================================================

On 2/4/2023 3:19 PM, George Wroclawski wrote:

First: what your machine is doing is unusual.

Without the drives enabled but the machine On, none of the Axis should move.

Turn the drives ON and none of the Axis should move. The control will monitor position and maintain it. The exception would be if the position loop for an Axis is compromised/broken/bad. Then it will drift at a speed relative to how far off your balance pot is. What is unusual here is that you are getting a dac underflow. The control would not display this unless it saw uncommanded movement.

If I was there, I would pull the encoder plug and adjust the balance pot so the z axis will not drift. I usually pull the belt cover off to watch this drift better. I would also check the X and y.

Might as well. Next because of the conflicting observations, I would do a scan disk just to see if there is corrupted data, and I would probably reload the software.

The wild card here is your encoder. Not sure the control is happy with it. I do not have a V2XT to play with near me but I would turn the z and y ballscrew to see if the display updates position.

Then try the Z axis.?

You have 2 more tricks to try. Swap motors. X and Z or Y and Z. See if it follows the motor/encoder assembly. Same for the Z drive board. Swap that with X or Y.

The command signal is typically a +/- 10 volt DC signal to tell a drive to move in a specific direction and a velocity relative to that voltage. That command signal is generated by the control using the G codes and distances to go that you input. The drive has no position loop. It does have a velocity loop. Commonly called the tach. It is in the same connector as the motor armature. The drive is totally dependent on the control to monitor position and expectations and convert them to a velocity command.

Thus this command can be a fraction of a volt to maintain position or 10vdc for a rapid move.

George Wroclawski
Service Manager
McDaniel Machinery Inc.

On Sat, Feb 4, 2023, 2:39 PM Pathwizard <willg@...> wrote:

Thanks George,

I have the maintenance manual and have attached the relevant chapter here I believe.

I just found and read this chapter after I got your email.? It does help me understand what you mean by "command".

Based on this and your previous email, it seems I need to adjust the balance while monitoring voltage on TP3 (which is also JP1-6 which is not connected on my machine).? Should I assume the VG and CG should be left alone?? Can this be done before drives are enabled?? I'm thinking I should temporarily disconnect the wire from J1-1 and short that pin to pin 2 while making the balance adjustment to be sure its voltage is zero during adjustment?

Is it common for this type thing to just go out of balance by itself after not being operated for a while?

I notice dust collected on portions of my drivers.? Do you recommend blowing this off?? Any other recommended? preventative maintenance?

I'm not sure how I can monitor and record the command voltage over time.? Maybe my scope if it doesn't change very fast.

On 2/4/2023 11:09 AM, George Wroclawski via wrote:

MSI drives.

Let's see what I can send.

JP4 is the encoder for Z?

JP9 is the command

There is a trouble shooting section in the maintenance manual which i cannot access right now.

I will keep looking.

-----Original Message-----
From: Pathwizard <willg@...>
To: [email protected]
Sent: Tue, Jan 31, 2023 5:38 pm
Subject: Re: [BridgeportMill] V2XT help needed

Thanks again.

Here is a picture of the drive.? Not sure which type it is.? You can see the pots in the upper left.

On 1/31/2023 5:16 PM, George Wroclawski wrote:

I am not at home right now. In TN installing 2 Kitamura horizontal pallet changers.

When i get home, i will see what i have in my?computer in pdf. My boss sold his building so all my books are in boxes in my barn. This is all done from memory. I am assuming you have the MSI drives. Not the gold chassis Bridgeport drives. Expect a email on Saturday.

George Wroclawski
Service Manager
McDaniel Machinery Inc.

On Tue, Jan 31, 2023, 6:06 PM Pathwizard <willg@...> wrote:

Thanks so much for your help George.? Without it (and some more to go I'm afraid) I'm going to have to scrap this old control and upgrade.? I'd really like to get it running as is though.? I've had it over a year and until this, has worked quite nicely.? Im new to CNC, but I've been using computers before DOS existed, so the age doesn't really scare me.? I program this machine in raw G-code with good results.

It did not accelerate to max velocity.? It moved medium speed down but only about 1 or 1.5 inches and then stopped with the alarm.
1) How do I monitor the command going to the drive?
2) To make sure the count is correct, somehow I need to count the pulses while rotating the motor by hand and I should get 250 rising signals on A with one turn.? Is this what you're suggesting?? I can probably rig up a counter of some kind to do this.
3) In principle, I understand your instructions for balancing the drive.? Sounds a bit scary though.? Each drive has what appears to be 3 pot adjustments on the front.? All have a dot of red paint to act as a security? lock I suppose.? Are these what is used for this balancing?? Is there any documentation available to help me know which and how to adjust?
Thanks again for the help.