Is there life after E-Stop?

[lgalla]

What happens after E-Stop is engaged?I picture E-Stop was used because a serious fault was happening,such as a crash into the table over travel etc.Now that you are locked in the fault position how do you restart?
Larry

[Geof]

Are you talking commercial machines or hobby machines?

For commercial machines this is my experience.

E-stop is not really applicable to overtravel because that is either detected by software limits or in the absence of these by limit switches. Most likely it will be software limits which means that when running a program the machine knows it will overtravel so it doesn't even attempt the move. In handle jog it will brake to a halt as it is jogged to the limit.

In the case of crashes generally E-stop is probably irrelevant because the machine has probably crashed, overloaded the servos and/or spindle and alarmed out long before you can hit E-stop.

However, the alarm condition resulting from a crash is similar to E-stop and recovery can often be as simple as clearing all the alarms and then backing the spindle/table away in handle jog. In some cases it can be a bit more difficult such as when you have friction welded the tool or tool holder to the workpiece or vise. Then you have to get creative.

[lgalla]

Geof,thanks for the reply.I like the friction welded tool creativity.Sawsall?If the drives current overload and software limits protect the machine faster than you could E-Stop,when is E-Stop useful?
Larry

[Geof]

Originally Posted by lgalla .....,when is E-Stop useful? Larry

In a few cases it is useful.

When you want to immobilize the machine without turning the main power off. Such as on a big machine when you actually have to climb into it to load a work piece, or something like that.

I have also used it when tapping something that was near the limit for my machine. I would have my hand over the E-stop button and if the spindle stalled I could cut the power immediately. The machine would have alarmed out but there is a 200 millisecond delay; I can react faster than this when I am ready and expecting it.

The presence of a big red E-stop button also keeps the health and safety bureaucrats happy.

[Al_The_Man]

If you want the official description see the zipped file in Post #6
http://www.cnczone.com/forums/safety...19-e-stop.html
I can see the implementation of a safety relay being mandatory soon in N.A. as it has been in Europe for some time.
PNOZ safety relays
Just a simple software E-Stops often used by Hobbyists would not be allowed in commercial systems and as a retrofitter I could not get away without all emergency stop conditions being hard wired.
The simple criteria is that: "ALL POWER will be removed from all devices that will create damage or hazard to machinery or personnel in the event of a system failure".
Using a commercial system, I will remove power from all outputs and leave inputs powered as well as the controller in order to read input status for trouble shooting.
In cases where a E-Stop string consists of several conditions in series, the offending function is usually found by systematic trouble shooting, or can be monitored and a operator message can be displayed to speed up the process.
Al.

[lgalla]

So Al and Geof are you saying hobbyist E-stop is generaly at the software level?The machine just stops movement but is still powered.I assumed E-stop would kill all power.
Thanks for the links

[ger21]

Larry, at the hobbiest level, it does whatever you want it to do. You're the one that needs to design and implement the E-Stop.

On the big routers I use at my day job, in cases where you hit the red button, you just twist to release, power back up, and restart the job. High end routers for the cabinet industry have all kinds of safeties built in, so usually worst case means re-home the machine, and start over. Now, if you bury the bit in the table, you might have to clean aluminum off the collet nut, and maybe replace some parts, but there's little to nothing involved in getting the machine running again.

[Al_The_Man]

Originally Posted by lgalla So Al and Geof are you saying hobbyist E-stop is generaly at the software level?The machine just stops movement but is still powered.I assumed E-stop would kill all power. Thanks for the links

Larry, As Gerry indicated, hobiest machines are often wired by many that are either not aware of the code requirements or control wiring practices, which they naturally do not have to follow as they are not selling in the commercial market.
Or are following advice from manufacturers of each piece of equipment or software, whose only interest is instructing the user on how he can disable their particular piece of equipment.
Unfortunately due to the lack of really informative advice the result is that many hobiest can end up with some conditions that can be potentially dangerous.
There was a post a while ago regarding a component part that was sold by a commercial seller aimed at the hobiest market here, which I can only assume originated in the R.O.C.. that featured 120v power sockets with exposed pins, this constituted an extremely dangerous condition, buyers did not appear to be aware of it until it was pointed out in one of the forums here.
Al.

[lgalla]

Hopefully the forum can help to prevent a dangerous situation for the hobbyist.Have been reading up on the zone on the subject.Many do not have E-stop,soft or hard limits.I assumed systems or machines had their own power drop and starter or magnetic contactor where all power would be disconnected.Will have to do more reading on the forums.
Just finnished some LaScalas.A CNC machine would have been nice.Gotta go to Can Post
Larry

[Al_The_Man]

Just over the past week or so there have been a couple of examples, or variations of such where someone had used the E-stop input to Mach and relied on Mach issuing an output to switch off a VFD, the other a Router using the PID controller, neither used a contactor or relay in the power circuit.
The output from the PC was active low, so Mach issued a high for turn off.
Everything apparently was OK until the PC went down or the power supply failed, this resulted in a low, switching the spindles on, in the case of the router the user was in the process of changing a tool bit!!.
Al.