[Claude Boudreau]

I'm always worry that my home made cnc router will end up destroying itself if the router fail when its left working by itself.
I'm using Mach 3, steppers (easy cnc card if I recall correctly)

I do have a router relay on the card but have never use it.

Any ideas on buildind an e-stop for router failure?

I do have e-stop buttons with end of travel limits switch on all axis that turn off my power supply relay.

[Al_The_Man]

Typically CNC spindles have a controller that can relay to the system the status of the spindle.
In this case its not too easy on a universal motor spindle, you could either use a current detector of some kind and/or monitor the 120v at the spindle.
These are limited in the nature of the detection, but that might be the very least you could do, apart from having a rotary pulse device .
Al.

[vger]

Al,

I think Claude has voiced a fear that many of us may have. I had a failure of my previous spindle (roto-zip) that ruined the piece being made.

Monitoring the spindle current might be problematic. There would need to be some sort of bypass so it would not be in E-Stop when you manually have the router turned off. Failure mode would get into play here too. If the router bearings locked up or windings shorted, the current would go up. Brush failure could cause the current to decrease or drop completely.

Shaft rotation monitoring enabled by power application to the router (spindle) might be easier overall to implement. When power is applied to the router (either manually or from the controller), the shaft rotation monitor could be enabled (perhaps after a short delay) so that pulses missing from the shaft pickoff would cause an E-Stop.

Steve

[bill south]

Wouldn't this be as simple as a photoeye on the spindle (rpm may be an issue). I'm thinking similar to the spindle monitors in the lathe conversions.
Just a thought!
Bill

[Claude Boudreau]

Wouldn't this be as simple as a photoeye on the spindle (rpm may be an issue). I'm thinking similar to the spindle monitors in the lathe conversions.
Just a thought!
Bill

If my router had dual shaft , I could recycle an old centrifugal switch , but they are N.C.

[Claude Boudreau]

Al,

I think Claude has voiced a fear that many of us may have. I had a failure of my previous spindle (roto-zip) that ruined the piece being made.

Monitoring the spindle current might be problematic. There would need to be some sort of bypass so it would not be in E-Stop when you manually have the router turned off. Failure mode would get into play here too. If the router bearings locked up or windings shorted, the current would go up. Brush failure could cause the current to decrease or drop completely.

Shaft rotation monitoring enabled by power application to the router (spindle) might be easier overall to implement. When power is applied to the router (either manually or from the controller), the shaft rotation monitor could be enabled (perhaps after a short delay) so that pulses missing from the shaft pickoff would cause an E-Stop.

Steve

Shaft rotation detection that would pause the program might be the way to go.
Be nice when you forget to turn the router on too.

[vger]

Claude,

Yeah, that would work too...

On some equipment I was scrounging motors out of, they had drilled and tapped into the back end of the shaft and inserted a screw that had a deep slot in it with an opto-interupter seeing through the slot every half revolution.

I suppose you could take the pulse from the opto to a 555 timer dircuit like the first example of this page....
Pulse Train 555 Voltage Detection - DATASHEET and Circuit Diagram

Check out the bottom of page 11 here....
http://focus.ti.com/lit/ds/symlink/ne555.pdf

It may be that the input would have to be coupled by a capacitor so that if the router stopped with the opto enabled it would still work.

Steve