Re: [CAD_CAM_EDM_DRO] Servo issue

Jason Cox wrote:

>Hi everyone,
>
>I have a retrofitted rf-45 mill/drill, using ametek servo's with us digital encoders fitted. All is driven by gecko 320's and cncPro.
>
>I havent got around to fitting limit switches yet and the other day somehow the machine was bumped and the x axis driven to the right into its stop, it stayed that way for some time until i noticed smoke from the x axis motor.
>
>I stipped everything down and concluded that the smoke was from the resin in the motors windings, however the motor seems to run perfectly with no issues.
>
>I hooked everything back up an switched on, the g320's resetted and held position. a few minutes later the thing started driving to the right by itself, just like when a g320 breaks its lock range.
>
>Its unpredictable when this will happen, and I can jog the x axis fine but then all of a sudden, bang it starts going to the right, sometimes after 2 seconds sometimes after 10mins.
>
>

I have a client in my area who has the same thing happen last night. I
am going to
see him tonight. He has Gecko 320's and the same Ametek/US Digital motors.

>What could this problem be, maybe the encoder? or have I damaged the g320 through heat? I thought the g320 would fault if there were problem.
>
>

No, don't depend on the 320 to protect itself. It has no overtemp
sensor, just an
overcurrent trip. The high resistance of these motors may prevent the
overcurrent
trip from activating. My guess is that there may be a weak power
transistor in
your gecko, and it is going to the shorted condition after it heats up.
You might
also check your encoder cable carefully for any loose connections. If
it only fails
while moving, that is a much stronger indication of a bad connection on the
encoder wires. You might also swap both the motor and encoder connections
between two axes, and see where the problem goes. If it stays with the
motor/encoder,
then it is there (motor, encoder, wires). If it moves to another axis,
it must be
in the Gecko drive. If you have not put a cover over your encoders, you
might want to do that. A speck of dust in the wrong place could block the
light and disable the encoder. And, that could be intermittent.

I will let you know what I find with my client tonight. His doesn't
wait to go
flying, it does this as soon as you power on. He said it stayed with the
motor/encoder in his case, but I want to verify it.

>Any help would be greatly appreciated, Im off to install some limit switches!
>
>
>

Limit switches may not help you, unless you have them set to cause an
E-stop.

Jon