E Stop Question.

[bob_lofthouse]

Hi all,

After all this time I've just noticed something on one of my machines today that suprised me.

One of my guys used the e stop button (very rare) and although everything cut out the spindle continued to spin under its own momentum for over a minute.

I tested my other machines which did the same.

Is something wired wrong as I thought they would slow down a little bit quicker than a minute.

In normal running mode the spindle stops/brakes well within ten seconds.

[srwtlc]

Robert, I did notice that once lately too. The spindle braking circuit must not function when the E-stop is hit.

[richards]

On my machine, the E-stop switch is part of the circuit that cuts all power to the machine, including the contactor that feeds power to the spindle. I haven't timed the spin-down time that the spindle takes to come to a full stop, but without power feeding the spindle, a full minute seems excessive. You might want to check with your electrician to make sure that everything is wired properly.

I don't have a schematic of my Alpha, but if memory serves me properly when you turn on power via the disconnect on the door and then press the Reset switch, the contactor(s) activate and self-latch until either the disconnect is switched off or the E-stop(s) switches are pressed. At that point, power to the contactor(s) coil is interrupted and the contactor(s) is/are deactivated. Since I'm not at my shop, I don't know whether the E-stop is directly connected to the contactor(s) coil or whether the E-stop connects through the controller board to the contactor(s) coil(s). I would prefer that the E-stop be directly connected to the coil(s), but that is just my preference.

[bob_lofthouse]

The operator only noticed the problem because the control software froze during a cutting file.

The cutter was not in contact with the wood being cut so had no resistance.

during tests afterwards pressing the stop button the control box cut out and the vfd powered down showing "ul" or "lu" even the fan on the spindle stopped almost instantly, but the spindle just kept going.

Over the period of the minute you could here the spindle slowing down gradually.

[richards]

Unless commanded otherwise, the spindle will 'coast' to a stop. Under normal operation, and if the VFD is uses the proper parameters, the spindle will 'ramp' to a stop as quickly as possible. It is very possible that with no resistance on the cutter and no power to the spindle that it could 'coast' for awhile until it finally stopped - think of a car traveling on a level road in neutral when the engine shuts off unexpectantly. The car's inertia will keep it moving forward until the laws of physics finally say that 'enough is enough' and the car stops.