Servo position errors w/FC

[Swede]

I had the unhappy episode of ruining two pieces of work with the same G-code set. What was happening was a Z-axis position error... the motor simply stopped, while the other two axes kept right on moving! Both cases caused a 1/8" ball mill to plow deep into virgin metal with predictable results.

I can fix it by increasing (within DCN) the allowable position error, but what I'd rather have it do is slam the system to a halt. I thought this latter was the normal mode for FC + servo.

Any advice? I may as well increase the allowable error to very high levels, as at least then it will try to catch up and not simply kill just *one* axis of the 3.

Swede

[Swede]

Well I found the problem with my system. I was using the stock limit switch harness, which is designed, I believe, for stepper systems. The three inputs which correspond to the servo axes were jumpered on the back of the 16-pin plug, creating a NC signal regardless of the state of the servo, which applies its signal through the DB25 cable.

After removing the jumpers, a servo fault now halts the system.

Moral: If you want your servo fault to be sensed by the software, be sure that the jumpers on the back of the input line harness are cut or removed. This was in the documentation, but buried pretty deep and not something that jumps out at you.

[ESjaavik]

Also check your control software to see if there is a max acceleration figure you can set so it doesn't try to ask the motors to ramp faster than they can, thus creating a too large following error.