Originally Posted by Terry Woods
Now... there are other considerations...
- what if the drill bit is broken?
- what if the Table Extender fails?
- what if the Pin Driver somehow ends up mis-aligned? And doesn't complete the function?
The point I was trying to raise was...
How are these conditions handled? It's one thing to have an idiot-light blinking at you. But... what happens when you respond to the idiot-light? Simply pressing an E-Stop, thus turning off all driven devices, might create a worse situation.
A drill-problem is not so bad because the drilling operation occurs while the Table is at Home. But, if the bit gets stuck in the part and then the E-Stop is pressed, the Part Clamp will release at the same time that the Drill retracts - the part will be retracted, with the drill-bit (maybe), away from the clamp. Will this produce a problem?
And by the way, you can count on the bits going dull! In order to prevent a dull-bit issue, you might want to intall a cycle-counter that will let you know (a flashing light?) when it is time to change the bit. The bit-change could be scheduled at an opportune time... before it results in down-time.
Now, what if the Pin Driver fails to complete the stroke, and the E-Stop is pressed while the Driver is in mid-stroke... what happens?
At this point, the Table is extended and the pin, held by the pusher, is partially inserted into the hole. When the E-Stop is pressed, both the Table and the Pin Driver will try to retract at the same time. Is this going to produce a more costly problem? Will the Pin Driver, or Pin Holder, get bent?
You need to consider everything when the E-Stop is pressed. In some cases, you need to develop a "controlled stop routine" as opposed to an absolute "hard crash-stop". As usual... it depends!
It's always those damned "what-ifs" that get you!
Always design your process for the normal, expected activity. But then, always consider and incorporate what is necessary for the "exceptions". That includes E-Stops.
Just a heads-up.