Limit SW to activate pause, not e-stop
14 Feb 2015 00:33 #55958
by andypugh
This is one of the subjects where there are two opinions, both valid.
A controlled stop is safer than an unpowered coast-to-stop.
If the reason for the stop is that the motors have run away then the controlled stop won't be controlled.
On a machine with motor brakes, cutting power is right. On a stepper system motor runaway is very unlikely, so controlled stop makes sense.
With other systems a harder decision needs to be made.
Luckily the LinuxCNC system allows you to arrange things any way you want. Possibly with different inputs causing different behaviours.
One think thought of this morning, yu could have a limit switch on a lathe to feed-hold (or pause the program) if the saddle is about to hit the tailstock. In that case you don't want an e-stop, you probably want to re-position the tailstock and carry on.
Replied by andypugh on topic Limit SW to activate pause, not e-stop
You must work with different motors then I do. NO brakes here. So, as I stated, a controlled stop is safer.
This is one of the subjects where there are two opinions, both valid.
A controlled stop is safer than an unpowered coast-to-stop.
If the reason for the stop is that the motors have run away then the controlled stop won't be controlled.
On a machine with motor brakes, cutting power is right. On a stepper system motor runaway is very unlikely, so controlled stop makes sense.
With other systems a harder decision needs to be made.
Luckily the LinuxCNC system allows you to arrange things any way you want. Possibly with different inputs causing different behaviours.
One think thought of this morning, yu could have a limit switch on a lathe to feed-hold (or pause the program) if the saddle is about to hit the tailstock. In that case you don't want an e-stop, you probably want to re-position the tailstock and carry on.
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14 Feb 2015 00:51 #55959
by andypugh
This is one of the subjects where there are two opinions, both valid.
A controlled stop is safer than an unpowered coast-to-stop.
If the reason for the stop is that the motors have run away then the controlled stop won't be controlled.
On a machine with motor brakes, cutting power is right. On a stepper system motor runaway is very unlikely, so controlled stop makes sense.
With other systems a harder decision needs to be made.
Luckily the LinuxCNC system allows you to arrange things any way you want. Possibly with different inputs causing different behaviours.
One think thought of this morning, yu could have a limit switch on a lathe to feed-hold (or pause the program) if the saddle is about to hit the tailstock. In that case you don't want an e-stop, you probably want to re-position the tailstock and carry on.
Replied by andypugh on topic Limit SW to activate pause, not e-stop
You must work with different motors then I do. NO brakes here. So, as I stated, a controlled stop is safer.
This is one of the subjects where there are two opinions, both valid.
A controlled stop is safer than an unpowered coast-to-stop.
If the reason for the stop is that the motors have run away then the controlled stop won't be controlled.
On a machine with motor brakes, cutting power is right. On a stepper system motor runaway is very unlikely, so controlled stop makes sense.
With other systems a harder decision needs to be made.
Luckily the LinuxCNC system allows you to arrange things any way you want. Possibly with different inputs causing different behaviours.
One think thought of this morning, yu could have a limit switch on a lathe to feed-hold (or pause the program) if the saddle is about to hit the tailstock. In that case you don't want an e-stop, you probably want to re-position the tailstock and carry on.
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- scubasteve1
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14 Feb 2015 04:34 #55964
by scubasteve1
Replied by scubasteve1 on topic Limit SW to activate pause, not e-stop
Also of machine have two limit switched mounted next to each other. There are separate dogs for each switch, one switch is in the e-stop chain and the other is used for homing and for a hardware soft-overtravel input, and another switch located elsewhere. this was if the machine did not home properly (stuck switch) the soft over travels would trigger before the estop. this was on a mill and when the e-stop is engaged the head drops about a 1/4" before the brake stops the head. I think the idea was to keep from crashing the head when smacking into the e-stop switch.
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