.... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Sat, 10 Jul 2010 00:45:13 -0700, Gunner Asch
wrote:

On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Gunner

There is a tuning method for tuning the amps, but while I can provide
the OmniTurn version for AMC....no idea of what does what with your new
control.

Sounds to me like if the above issues are clear..it needs to be properly
tuned. Something is set too high if the above issues are negative.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Jul 10, 2:45*am, Ignoramus30064 ignoramus30...@NOSPAM.
30064.invalid wrote:
... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Not having seen your controller, but having designed and fixed an
awful lot of electronics, I can imagine bad electrolytic capacitors
being at the root of this. Take a look at the electrolytics on the
control and power supply boards. if the ends of any of them are even
slightly convex or have any discoloration, they MUST be replaced. I've
fixed dozens of monitors, power supplies and motherboards by just
visually picking out the bad caps. I don't know why your mill would be
any different.

Could this be the result of a bad ground somewhere causing extra
pulses to come out of a position sensor? You should be able to
disconnect the input to the servo ampllifier and put a short circuit
on it.If it still moves, then the problem has been isolated at least
that far.

On Jul 10, 2:45*am, Ignoramus30064 ignoramus30...@NOSPAM.
30064.invalid wrote:
... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.


i

When you say no input, is that with no connection or is that with a
short on the input?

Dan

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Gunner

There is a tuning method for tuning the amps, but while I can provide
the OmniTurn version for AMC....no idea of what does what with your new
control.

Sounds to me like if the above issues are clear..it needs to be properly
tuned. Something is set too high if the above issues are negative.

Gunner

No question, just need a little jewelers screwdriver and the instructions
from the AMC site or I'm sure the Omniturn is a copy of this.

Ignoramus30064 wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Dude, *it doesn't matter*, your CNC control takes care of it. You need
to spend some time reviewing servo loops, the drive is little more than
a power amplifier, it is the servo loop with the encoder and CNC control
that controls the position, not the motor drive.

The CNC control's servo loop monitors the encoder and when it shifts a
count it will just adjust the signal to the drive to compensate. This is
why when the servo loop is running you can grab the motor shaft and try
to turn it and the harder you try to turn it the harder it will resist
you. This is also why you use encoders with sufficient resolution that a
few encoder counts doesn't equate to any appreciable axis movement.

On 2010-07-10, Gunner Asch wrote:
On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Maybe it is a gain issue.

There really is no input: I use a reversing Lego switch to send signal
to from a little power supply to the amplifier, and the switch was off

i

On 2010-07-10, wrote:
On Jul 10, 2:45?am, Ignoramus30064 ignoramus30...@NOSPAM.
30064.invalid wrote:
... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.


i

When you say no input, is that with no connection or is that with a
short on the input?

No connection (switch off).

i

On 2010-07-10, Karl Townsend wrote:

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Gunner

There is a tuning method for tuning the amps, but while I can provide
the OmniTurn version for AMC....no idea of what does what with your new
control.

Sounds to me like if the above issues are clear..it needs to be properly
tuned. Something is set too high if the above issues are negative.

Gunner

No question, just need a little jewelers screwdriver and the instructions
from the AMC site or I'm sure the Omniturn is a copy of this.



I tried adjusting one thing so far, which is the test/offset pot, to
no avail.

i

On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

I assume you have no controller attached yet? The offset pot can get
you very close to zero speed, but without the controller you'll always
see a little drift. Remember, the amp has no knowledge of the motor's
position at this point. The controller is needed to close the position
loop and hold an exact position.

There's no problem with the amp.

--
Ned Simmons

On Sat, 10 Jul 2010 09:44:21 -0500, Ignoramus30064
wrote:

On 2010-07-10, Gunner Asch wrote:
On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Maybe it is a gain issue.

There really is no input: I use a reversing Lego switch to send signal
to from a little power supply to the amplifier, and the switch was off

i

Is the Lego a mechanical switch? I used to put a resistor across the
signal input on solid state relays to keep them from switching on for
a cycle once in a while.

Pete Keillor

On 2010-07-10, Pete Keillor wrote:
On Sat, 10 Jul 2010 09:44:21 -0500, Ignoramus30064
wrote:

On 2010-07-10, Gunner Asch wrote:
On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Maybe it is a gain issue.

There really is no input: I use a reversing Lego switch to send signal
to from a little power supply to the amplifier, and the switch was off

i

Is the Lego a mechanical switch? I used to put a resistor across the
signal input on solid state relays to keep them from switching on for
a cycle once in a while.

Pete Keillor

Purely mechanical.

i

On Sat, 10 Jul 2010 09:44:21 -0500, Ignoramus30064
wrote:

On 2010-07-10, Gunner Asch wrote:
On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Maybe it is a gain issue.

There really is no input: I use a reversing Lego switch to send signal
to from a little power supply to the amplifier, and the switch was off

i

The quick and dirty adjustment for Omniturns that use the AMC amp..is to
turn the loop gain up until the servo starts to whine and then back it
off 2 turns

http://omniturnfactorydirect.com/Omn..._G3_100128.pdf
page 172 for the newer Glentek amps.

Ill have to hunt around a bit for docs on the old AMC amps. Its in my
books..but...

http://omniturnfactorydirect.com/Omn..._G4_100611.pdf
Check page 176....its close.

Looks like they have upgraded the control once again..havent seen this
one yet in the field.

The software built into the main program has internal assists..so this
may not be of much help to you.

http://www.omni-turn.com/Pages/Techn...djustment.html

Btw...when the servo moves without input from softward or operator..its
called a "runaway" in the biz.

Might help when doing google search

Gunner


One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

Ignoramus30064 wrote:

On 2010-07-10, Gunner Asch wrote:
On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Maybe it is a gain issue.

There really is no input: I use a reversing Lego switch to send signal
to from a little power supply to the amplifier, and the switch was off

i

Adjust your test / offset to get the minimum creep when the control
input is grounded to ensure it is not "floating". The little bit of
creep you may have left *may* go away once you adjust the gain when
tuning the servo loop, but it isn't important. You can not tune the
drive in any meaningful way unless it is operating under control of the
servo loop with the encoder and control PC.

On Sat, 10 Jul 2010 09:44:21 -0500, Ignoramus30064
wrote:


I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Maybe it is a gain issue.

There really is no input: I use a reversing Lego switch to send signal
to from a little power supply to the amplifier, and the switch was off

i


Oh..I forgot to include AMCs website/support section

http://www.a-m-c.com/content/support...es/analog.html

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Sat, 10 Jul 2010 11:00:04 -0400, Ned Simmons wrote:

On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

I assume you have no controller attached yet? The offset pot can get
you very close to zero speed, but without the controller you'll always
see a little drift. Remember, the amp has no knowledge of the motor's
position at this point. The controller is needed to close the position
loop and hold an exact position.

There's no problem with the amp.


He is not hooked to the controller yet?

Yes..it will drift

Sometimes if you are off in tuning....it will freaking Bolt at high
speeds if not hooked to the controller.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

Ned Simmons wrote:

On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

I assume you have no controller attached yet? The offset pot can get
you very close to zero speed, but without the controller you'll always
see a little drift. Remember, the amp has no knowledge of the motor's
position at this point. The controller is needed to close the position
loop and hold an exact position.

There's no problem with the amp.

Exactly. Iggy need to read up a bit more on servo loops, and understand
that the drive is little more than a power amplifier. The fact that the
drives have some features for non CNC applications i.e. simple closed
loop speed control based on tach feedback is confusing him.

Iggy, CNC servo control is not about speed, it is about position. The
CNC control manages the speed through it's control of position and how
quickly it changes that position. Acceleration and deceleration rates
and travel speeds are all controlled by the CNC control, not by the
servo drive. This is different from something like a VFD where those
parameters are controlled by the VFD.

Gunner Asch wrote:

On Sat, 10 Jul 2010 09:44:21 -0500, Ignoramus30064
wrote:

On 2010-07-10, Gunner Asch wrote:
On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Maybe it is a gain issue.

There really is no input: I use a reversing Lego switch to send signal
to from a little power supply to the amplifier, and the switch was off

i

The quick and dirty adjustment for Omniturns that use the AMC amp..is to
turn the loop gain up until the servo starts to whine and then back it
off 2 turns

http://omniturnfactorydirect.com/Omn..._G3_100128.pdf
page 172 for the newer Glentek amps.

Ill have to hunt around a bit for docs on the old AMC amps. Its in my
books..but...

http://omniturnfactorydirect.com/Omn..._G4_100611.pdf
Check page 176....its close.

Looks like they have upgraded the control once again..havent seen this
one yet in the field.

The software built into the main program has internal assists..so this
may not be of much help to you.

http://www.omni-turn.com/Pages/Techn...djustment.html

Btw...when the servo moves without input from softward or operator..its
called a "runaway" in the biz.

Might help when doing google search

Iggy does not yet have a servo loop operating, therefore he can not tune
the loop or the drive at this time.

On Sat, 10 Jul 2010 10:37:00 -0500, "Pete C."
wrote:


Ignoramus30064 wrote:

On 2010-07-10, Gunner Asch wrote:
On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Maybe it is a gain issue.

There really is no input: I use a reversing Lego switch to send signal
to from a little power supply to the amplifier, and the switch was off

i

Adjust your test / offset to get the minimum creep when the control
input is grounded to ensure it is not "floating". The little bit of
creep you may have left *may* go away once you adjust the gain when
tuning the servo loop, but it isn't important. You can not tune the
drive in any meaningful way unless it is operating under control of the
servo loop with the encoder and control PC.

Indeed. I wasnt aware he was free running the amp, without the control.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Sat, 10 Jul 2010 10:50:15 -0500, "Pete C."
wrote:


Gunner Asch wrote:

On Sat, 10 Jul 2010 09:44:21 -0500, Ignoramus30064
wrote:

On 2010-07-10, Gunner Asch wrote:
On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Maybe it is a gain issue.

There really is no input: I use a reversing Lego switch to send signal
to from a little power supply to the amplifier, and the switch was off

i

The quick and dirty adjustment for Omniturns that use the AMC amp..is to
turn the loop gain up until the servo starts to whine and then back it
off 2 turns

http://omniturnfactorydirect.com/Omn..._G3_100128.pdf
page 172 for the newer Glentek amps.

Ill have to hunt around a bit for docs on the old AMC amps. Its in my
books..but...

http://omniturnfactorydirect.com/Omn..._G4_100611.pdf
Check page 176....its close.

Looks like they have upgraded the control once again..havent seen this
one yet in the field.

The software built into the main program has internal assists..so this
may not be of much help to you.

http://www.omni-turn.com/Pages/Techn...djustment.html

Btw...when the servo moves without input from softward or operator..its
called a "runaway" in the biz.

Might help when doing google search

Iggy does not yet have a servo loop operating, therefore he can not tune
the loop or the drive at this time.

True indeed. I wasnt aware he was not "there" yet.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Sat, 10 Jul 2010 08:56:48 -0700, Gunner Asch
wrote:

On Sat, 10 Jul 2010 10:37:00 -0500, "Pete C."
wrote:


Ignoramus30064 wrote:

On 2010-07-10, Gunner Asch wrote:
On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Maybe it is a gain issue.

There really is no input: I use a reversing Lego switch to send signal
to from a little power supply to the amplifier, and the switch was off

i

Adjust your test / offset to get the minimum creep when the control
input is grounded to ensure it is not "floating". The little bit of
creep you may have left *may* go away once you adjust the gain when
tuning the servo loop, but it isn't important. You can not tune the
drive in any meaningful way unless it is operating under control of the
servo loop with the encoder and control PC.

Indeed. I wasnt aware he was free running the amp, without the control.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch


Oh..Im only familiar with AMC drive models NC-4/NC-5/NC-7 and NC-9

They went to other drives later in production.

Ive got a stack of unknown condition drives, AMC, Copely and Glentek
sitting out on the shelf..if anyone wants to putter around with SMD
circuit boards....G



Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

In article ,
Ignoramus30064 wrote:

On 2010-07-10, Karl Townsend wrote:

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Gunner

There is a tuning method for tuning the amps, but while I can provide
the OmniTurn version for AMC....no idea of what does what with your new
control.

Sounds to me like if the above issues are clear..it needs to be properly
tuned. Something is set too high if the above issues are negative.

Gunner

No question, just need a little jewelers screwdriver and the instructions
from the AMC site or I'm sure the Omniturn is a copy of this.



I tried adjusting one thing so far, which is the test/offset pot, to
no avail.

"Off" is a slippery concept. It sounds like you have a very slight leakage
current somewhere. It could be anything; one never eliminates them all. I
would short the input out and see what the creep rate becomes. It won't be zero
unless you are under closed-loop control. Nor is 8"/hour all that bad for open
loop.

Joe Gwinn

"Ignoramus30064" wrote in message
...
... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Normally I have my controller controlling before powering the servo drives.
Sounds like your amps are normal but you probably need the control on before
the amps and the amps off before turning the control off.

Rogern

this behavior would be typical of a servo system with rate feedback only and
no position feedback

"Ignoramus30064" wrote in message
...
... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Ignoramus30064 wrote:
... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i


Creeps are sometimes hard to get rid of. I filter them out but they
creep back in.

The creeping of your drive is normal. You could fine tune the offset
control with the input ref. signal shorted out but I would not bother
until you get the whole control set up.

A servo system is just like your own body which is a bunch of servo
systems. For instance when you drive a car down the road you
automatically steer the car in the right direction. You have in fact a
closed servo system consisting of your eyes,your brain, your arms, the
steering system of the car and the wheels. Your eyes are the position
sensor just like an encoder. IF you shut your eyes the loop now become
open you could go down the road for a while without getting too far off
track (if your wife is in the car and starts screaming that is
equivalent to an out of position error which shuts down everything with
an e stop) but eventually you would drift or creep off the road either
left or right. Closing your eyes is like having only the servo
operating without having the control connected. When I was young and
foolish I would drive for miles with my eyes shut and have my buddy tell
me which way to turn, still a closed loop system but with two peoples
brains.

John

On Jul 10, 10:45*am, Ignoramus30064
No connection (switch off).

i

As other have said, don't sweat it. It sounds as if you have a PID
servo loop. P stand for Proportional, I is for Integrating, and D is
for Differential. You have a very small error likely caused by a
little leakage. The integrating part of the look is integrating the
very error small signal and causing the creep. With the servo loop
closed, you could see some offset, but I expect it will be too small
to measure.

Dan

On 2010-07-10, Ignoramus30064 wrote:
... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

You need the controller to feed correction signals as the
encoder indicates the need. This means the "no input signal" situation
should not in use exist.

What happens when you enable the "motion inhibit" inputs?

I may call AMC on Monday to find out.

The will probably tell you that until you are connected to the
controller, you can't get truly stationary behavior.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Sat, 10 Jul 2010 12:15:28 -0500, "RogerN" wrote:


"Ignoramus30064" wrote in message
m...
... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

i

Normally I have my controller controlling before powering the servo drives.
Sounds like your amps are normal but you probably need the control on before
the amps and the amps off before turning the control off.

Rogern


Ayup.

Gunner


One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On 2010-07-10, Ignoramus30064 wrote:
On 2010-07-10, Gunner Asch wrote:
On Sat, 10 Jul 2010 01:45:39 -0500, Ignoramus30064
wrote:

... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

[ ... ]

Either you have voltage on the input (1-10vt) or you have rate
gain/test offset set too high. Test your input on a millivolt scale and
see if there is a trickle of power getting to the servo. Sounds like
there is. Might want to put in a 100 ohm resistor or something to get it
down to nada. If you have a scope..check it for trace AC as well. it
should be clean DC coming in...or nothing at all. If you have a leaky
diode..you might be getting a trace of AC or flutters.

I use a lot of AMCs on OmniTurn cnc lathes..but dont want to compare
them with mill uses.

Maybe it is a gain issue.

I don't think so. The gain (and tach feedback gain) is used to
set the max speed for 10V DC input to the amp'd control terminals. And
some is used to control overshoot when getting step motion controls.

There really is no input: I use a reversing Lego switch to send signal
to from a little power supply to the amplifier, and the switch was off

The input pins being open (switch off) can allow a bit of
leakage in other parts of the amplifier circuit. Try setting the input
shorted -- but I suspect that you won't be able to find a truly no creep
position of the offset pot even with the input shorted. At least, not
one which will remain so through changes in room temperature.

It really *needs* the computer monitoring the motion via the
encoder, and outputting signals to move back to where it belongs at need.
So once you have a complete system, this should not be a problem.

And when the computer is turned off -- you want the inhibit to
be true, which *should* keep it from moving at all.

And of course, normally, when the computer is turned off for any
length of time -- the power to the rest of the lathe should be turned
off too.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Ignoramus30064 wrote:
... Because it "creeps".

I have only one axis (x) wired right now. When the drive is powered on,
but with no input signal, the table imperceptibly slowly creeps. I
only noticed it because some tools fell off the table as it moved by
perhaps 8 inches in an hour.

There is a "test/offset" pot on the board that, if turned properly,
shifts input signal and makes the table move. I could easily set it so
that the mill does not _visibly_ move. I have not, however, been able
to get rid of the slow creep.

I may call AMC on Monday to find out.

Don't bother, this is normal. It is an analog circuit, there are always
slight offsets, and
they change over time/temperature. If I cared, I'd have to retune my
system when the seasons
change, but it is of no consequence. Once the positioning loop is
closed by the encoder/PPMC/
EMC2, it will not drift like this. (In EMC2, you can hit F1, but if you
don't hit F2 to turn on
the positioning loop, you get in this same mode. You can use it to set
the velocity offset pot,
but don't worry about getting it "just perfect".

Jon