I have a question about the function of E-Stop.


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    Default I have a question about the function of E-Stop.

    I was looking at the wiring diagram for the DYN4 1.8kw servo that I am using for a spindle motor and it shows the E-Stop cutting power to the coil of the contactor that switches power to the DYN4 drive and motor. OK, that sounds great for an emergency. But, since I am new to CNC, CAM and LinuxCNC I run my jobs with pendant in hand and finger on the E-Stop button. I will stop the job if I realize that I forgot something like loading the correct program for the current operation or something just doesn’t look right. All I want to do is stop everything and start over. Powering down the drive and motor seems a bit extreme for the situation at hand. While there is a way to pause the program on the pendant using two buttons simultaneously it’s not as easy as pressing the big red button. I have read that the E-Stop should stop all motion and remove power to the machine. It’s removing the power part that seems extreme for what I have used the E-Stop for so far. Should I have an E-Stop that stops and kills power to everything to be used for a real emergency and also a separate button that just stops all motion?

    Thanks
    John

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    Gold Member Jim Dawson's Avatar
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    Default Re: I have a question about the function of E-Stop.

    The E stop should kill all machine motion. What you want is a pause or feed hold button. Not sure how to implement that in your system, but I'm guessing that LinuxCNC has a provision for that.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: I have a question about the function of E-Stop.

    Thanks Jim,

    That is the route I wanted to take for the E stop is to just stop motion and leave DYN powered but disabled. I'm sure I can create an external button to pause motion.



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    Default Re: I have a question about the function of E-Stop.

    Here are the pause/Resume Run/Stop buttons and warning lights on my linuxCNC plasma machine. The config or the buttons is on the Linuxcnc forum, I've also got a mast with a stacklight on it that does the same as these lights at eye level.



    Whilst the main estop button shown here is hardwired to drop mains power to the 48v power supply, as the build progressed, I found I needed more estops (for pendant and torch breakaway). I then configured the steppers to be disabled on estop via the stepper drive enable signals so all power to the table is still disabled. Also be aware that in Linuxcnc you can build an estop chain in software using estop-latch. This is not well documented anywhere but I finally worked it out.

    Rod Webster
    www.vehiclemods.net.au


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    Default Re: I have a question about the function of E-Stop.

    Right now I have two E-Stop buttons. The original E-Stop button on the Sieg X3 and one on the iMach III P4-SE Pendant. In addition if I stall the spindle it will cause an E-Stop. Right now, in an E-Stop condition the spindle motor is stopped via a relay and all motion is stopped via software in LinuxCNC. When I release the E-Stop and click on the power button in Axis I am ready to run the program again. No loss of home or touch-offs. Because I am new to this I easily make my share of mistakes and therefore pressing E-Stop more than I probably should. I have found, and learned how to use the pause/resume button on the pendent but it's not as convenient as the big red button.

    My current spindle motor is just a 600w brushed motor and the relay is replacing the original spindle On/Off switch. With the new DYN4 1.8K servo that I am going to replace the old spindle motor with, I think I would rather not be powering it up and down for each E-Stop. Would it be crazy to have a master E-Stop that quickly kills all power to everything for a real Oh Crap! situation and have the E-Stops I currently have now just stop all motion but leave the power on and just disable the spindle and steppers?

    I really like your physical Run/Step Pause/Resume buttons and the lights. I was originally going to get a touch screen but now I am not sure. I really like the physical buttons. I'm using a Mesa 7i76 so I have plenty of I/O.

    Thanks
    John



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    Gold Member Jim Dawson's Avatar
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    Default Re: I have a question about the function of E-Stop.

    The DYN4 does have an Enable input, pin 6, if I recall correctly. Grounding this pin disables the drive output to the servo without shutting down the drive. The other option would be to set the speed to zero in software on pause. Not a safe condition for changing tools or something like that, but useful for doing other stuff as long as your hands are kept clear of the spinny things.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: I have a question about the function of E-Stop.

    Thanks Jim, I hadn't gotten past thinking about E-Stop to think about the other situations where the spindle would need to be stopped. There is an Enable that must be high for the spindle to run. That is what I was thinking of using during an E-Stop. Right now my E-Stop button on the Pendant relies on LinuxCNC but I just got it upgraded to the "E" version that provides a physical set of contacts that are activated when the E-Stop is pressed so that E-Stop will still work if LinuxCNC goes off to LaLa land. So at this point I think my plan is to disable the spindle and stepper drives using the Enable pin when in an E-Stop condition. I also have a spindle lock that will disable the spindle using the Enable pin while changing tools.

    Since I am a programmer (Not CNC) by trade I am not familiar with how things usually/should work other than from what I have read here and on the LinuxCNC forum.

    Thanks for all of the help.
    John



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    Default Re: I have a question about the function of E-Stop.

    Quote Originally Posted by rcheli View Post
    Thanks Jim, I hadn't gotten past thinking about E-Stop to think about the other situations where the spindle would need to be stopped. There is an Enable that must be high for the spindle to run. That is what I was thinking of using during an E-Stop. Right now my E-Stop button on the Pendant relies on LinuxCNC but I just got it upgraded to the "E" version that provides a physical set of contacts that are activated when the E-Stop is pressed so that E-Stop will still work if LinuxCNC goes off to LaLa land. So at this point I think my plan is to disable the spindle and stepper drives using the Enable pin when in an E-Stop condition. I also have a spindle lock that will disable the spindle using the Enable pin while changing tools.

    Since I am a programmer (Not CNC) by trade I am not familiar with how things usually/should work other than from what I have read here and on the LinuxCNC forum.

    Thanks for all of the help.
    John
    You're at risk of diminishing your safety just so you can use the ESTOP button as a runhold instead of its intended purpose - an actual emergency.

    The question is whether you can totally trust that enable pin to remove motion, and by extension, the circuitry feeding it. If the enable pin is fed via an estop relay then maybe that's the risk you can accept. It wouldn't fly in the modern industrial world, but that's pretty much how the spindle is handled in my '99 Benchman XT. Standards evolve.

    A better solution might be to use a specific purpose safety controller with an additional delayed output. Use the immediate output to cut the enable pin, and the delay to cut the motor leads. Or use the immediate output to trigger a commanded fast brake, followed by a motor lead cut. The idea is to avoid cutting the motor leads whilst the motor is turning as it can damage components, but to be sure that the motor cannot start again.



    Sent from my SAMSUNG-SM-G900A using Tapatalk



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    Community Moderator Al_The_Man's Avatar
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    Default Re: I have a question about the function of E-Stop.

    Quote Originally Posted by rcheli View Post
    Since I am a programmer (Not CNC) by trade I am not familiar with how things usually/should work other than from what I have read here and on the LinuxCNC forum.

    Thanks for all of the help.
    John
    The E-Stop should always function as per the NEC/CEC etc, and cut all motive power, as Jim has said you should be able to implement the Pause or temporary stop if you just want to halt a program etc, I would have thought that there would be a precedent in Linux that someone has come up with already.
    The function I found the most useful is the feedrate overide control, this turns all axis feedrate down in increments from 100% to 0% this together with a distance to go display you can see exactly if a 'Crash' is likely to occur !.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Default Re: I have a question about the function of E-Stop.

    So you have a small machine and a 7i76e ethernet controller. I have a large machine and a 7i76e.
    On this thread on the LinuxCNC forum, I document how to use estop-latch to add multiple e-stop conditions.
    https://forum.linuxcnc.org/10-advanc...s?limitstart=0
    I've since extended this estop-latch chain to include another estop switch mounted on the touch screen monitor (running Gmocappy GUI)

    I would be very nervous about depending on a USB connected pendant for e-stop. In my view estopping a machine across a serial connection to a USB input is fraught with danger. While I also have a remote pendant, it is a professional device which has 433 Mhz wireless pendant that talks to a hard wired receiver and uses one of the 7i76e MPG inputs for the pendant jog wheel. The receiver is bristling with I/O signals that are hardwired into the 7i76e input and output pins.

    From my thread above, I think my config is ideal for you. I would retain the machine estop as a Category 0 estop, retain my stepper drive disable
    Code:
    # --- E-STOP STEPPER DRIVE DISABLE ---
    net estop-out hm2_7i76e.0.7i76.0.0.output-05
    and use one of your 16 outputs on the 7i76e to disable your spindle
    Code:
    # --- E-STOP SPINDLE DRIVE DISABLE ---
    net estop-out hm2_7i76e.0.7i76.0.0.output-06
    Any questions about getting this going, ask on the Linuxcnc thread I've linked you to.

    I think possibly it would be worth adding a feed hold button on the machine.
    Code:
    # --- FEED HOLD ---
    net feed-hold <= halui.program.pause
    net feed-hold => hm2_7i76e.0.7i76.0.0.input-06
    or implement what I've done with the run/step, pause/resume which is published as an example on the Linuxcnc Forum
    https://forum.linuxcnc.org/47-hal-ex...resume-buttons

    Last edited by rodw; 05-11-2018 at 05:40 PM.
    Rod Webster
    www.vehiclemods.net.au


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    Default Re: I have a question about the function of E-Stop.

    Thank you all for your advice and guidance.

    I certainly don't want to create an unsafe machine just for convenience sake. Although my pendant does talk to LinuxCNC via USB it does have a physical contact that is opened when the E-Stop is pushed so that makes it the same as the factory E-Stop on the mill. The DYN4 docs show the E-Stop opening the contactor that feeds power to the drive and motor so that is what I will do. What about doing tool changes? The statement below form the DYN4 manual had me that I should not be killing power to the drive and motor each time I do a tool change. I sent and email to DMM Technologies for clarification. It cutting power to the drive and controller every time I stop the spindle then that is what I will do and I will feel safer with it that way.

    ? Supply Power Cycle Do not cycle the main power supply quickly as internal circuit may be permanently damaged. Power to servo drive should be turned on once during each operation cycle.

    After going back an looking at one of the links Rod provided I realized I had read that thread before when I was just starting this adventure and my head was spinning with all of the new information. This is one of the statements that was in t he back of my mind. So as you can see being just a dumb new CNC hobbyist comparing what I think I am hearing here (kill all motive power) and what I read before (see below) why I'm confused.

    All of the large commercial CNC routers I use at work (Big machines with Fanuc and one other industrial control) built by big companies like Komo, Northwood, Heian, Anderson, SCM. The E-stop systems do not remove power from any control systems. They only disable all servo drives (not power down), stop the spindle VFDs (using DC injection braking.) and set an E-stop alarm in the control. All using a simple NC logic circuit of series wired switches and relays that trigger all of the actions independently of any control software or PLC. However the control and or PLC do monitor the state of the E-stop.
    A central power disconnect is a completely different affair unrelated to E-stop..


    Rod, I will definitely be reading your thread and consider implementing those buttons. I also want to try GMOCCAPY.

    Writing this reply has taken a fair amount of time an effort as did all of everyone else's replies and thoughtful input. I thank you all. I am looking forward to the day when I know enough and am confident enough in my knowledge can help the next person who travels this path.

    John



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    Community Moderator Al_The_Man's Avatar
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    Default Re: I have a question about the function of E-Stop.

    Quote Originally Posted by rcheli View Post
    All of the large commercial CNC routers I use at work (Big machines with Fanuc and one other industrial control) built by big companies like Komo, Northwood, Heian, Anderson, SCM. The E-stop systems do not remove power from any control systems. They only disable all servo drives (not power down), stop the spindle VFDs (using DC injection braking.) and set an E-stop alarm in the control. All using a simple NC logic circuit of series wired switches and relays that trigger all of the actions independently of any control software or PLC. However the control and or PLC do monitor the state of the E-stop.
    A central power disconnect is a completely different affair unrelated to E-stop..
    I have worked in the CNC retro-fit business for a number of years using Fanuc and Mitsubishi and other controls and yes an E-stop does not have to remove power from the controller or even the PLC/PMC except the power to the actual PLC Outputs supply and motor driven functions.
    Also local jurisdiction regulations such as NEC/CEC etc have to be followed, similar ones are in effect in the IEC etc, and the main gist is that all power that can cause danger to man or machine in an emergency must be removed in E-Stop, there is a stipulation where some power removal can be done in a controlled fashion where an abrupt removal will cause of danger to man or machine.
    Just a software stop in itself is not permitted.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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I have a question about the function of E-Stop.

I have a question about the function of E-Stop.