Re: Close loop steppers

Charles Hopkins wrote:

> From: Charles Hopkins <chopkins@...>
>
> I have been working with the idea of using the encoders to do a position check at the start of the program. If the position is not correct the system can be halted just the same as a safety door check.
>
> I was planning of just using a second computer for this task. Once it is setup and running I should not need the monitor or the keyboard. I should be able to set the ref point through the parallel port and send a signal back to the machine control through the parallel port also.

2 computers? Come On! Why don't you just have encoders going back to the first computer,
and have it correct the error immediately?

Or, go to servos, and be done with missed steps forever!

Jon

> Not any good for the part where the missed steps occurred, but this will prevent a second part being scraped. It will also give a position to reset the position. I now use indicators, but if the machine is unattended it sometimes will push the indicator until it hits the limit switch.
>
> Most all my missed steps are due to power failures which seem to happen much too often. I live in a rural area and power is not to be taken for granted. A UPS takes care of the computer, but the machine stops and position is not guaranteed.

I had a power blip that was long enough for me to start reaching for a flashlight before the
lights came back on. I was in the middle of a cut, and assumed I'd have a mess, with lost
position, spindle inverter tripped off, etc. I was amazed to see the CNC computer was
still chugging along, the spindle was still running, no problem! The power was off about
1/4 second, I guess.

Jon