Re: [CAD_CAM_EDM_DRO] Dead encoder???

Marcus wrote:

>Hi All:
> I have a brand new problem with my Defiance 3 axis CNC mill that I'm
>hoping one of you can help me out with.
>It's a servo machine, with a DX32 (Bridgeport) PC based controller.
>Today, it started faulting out part way through a program...it gave me a
>following error message.
>The control thinks there's an obstruction that's making the table lag behind
>the commanded position.
>The machine boots up and homes normally when it's cold; it will also run
>part way through a program, and then it quits.
>It always quits at a different place in the program, so it's not the code.
>As the machine warms up, the fault will occur sooner and sooner, and
>eventually the machine won't even home anymore.
>Nothing is mechanically wrong so far as I can tell, and I can jog all three
>axes from limit to limit using the manual pulse generator.
>I can't tell from the error message which axis is tripping the shutdown, but
>when the machine is warm enough to fault during the homing sequence, it's
>the X axis that trips it.
>How would I begin to narrow down the problem?
>The machine is an orphan; Defiance Corporation no longer exists, so I'm on
>my own with this one.
>Could this be an axis encoder?
>
>

It definitely does NOT sound like an encoder problem. The fact that you
can jog
all over without problems indicates the encoder is probably working
fine. If the
encoder was failing, it would cause sudden jumps of the table or servo
faults.
The encoder usually doesn't suffer much heat, and this sounds like a classic
(over)heating problem.

I suspect there is a bad transistor in a servo amp, or possibly a bad
solder joint.
It also sounds like the problem is in the X axis. Find the X servo amp and
look for things that appear to have suffered overheating. If you can
identify the
make and model of servo amp, you might be able to get a replacement on eBay.
Even if something proprietary, it may be possible to replace with a
Copley or
Servo Dynamics servo amp.

One other possibility is a bad cable to the motor, especially a solder
joint at the
connector.

Jon