The mill is creeeeepy

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

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

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.

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

Dan

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.

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.

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

No connection (switch off).

i

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

i

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.

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

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

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...

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.

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

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.

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

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

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

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.

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

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