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  1. #21
    Along with this thread and my own I can see there is never going to be a consensus of opinion with regard to limits and emergency stop circuits. All anyone can do is see what others have done and choose the bits that suit them best.
    Here's how mine is going to be, I just changed a few things this weekend and will upload my 'as build' drawings later.
    My emergency stop circuit consists of a big red button on the control panel and another in series on the machine, the limits are also in series with these buttons and a relay in the VFD indicating a fault condition is also in the circuit. Everywhere I have worked the limits, which I'm going to call 'ultimate limits' because that is what they are, always form part of the emergency stop circuit. These limits should never be activated, Mach3 has 'soft limits' for example that should operate first (don't know about Linux system).
    I'm also using a PILZ emergency stop relay (@birchy it only cost £25 on ebay) so when the emergency stop circuit is activated the relay de-energizes removing power to the stepper drivers, sending Mach3 an E/stop signal, stopping the VFD by using a special emergency stop function and a Safe Torque Off (STO) feature.
    The system can only be reset when all the relays and buttons are in the correct position and the VFD has been reset.
    I also have a ‘stop’ button on the control panel that sends a STOP signal to the VFD and also stops Mach3 running. There is a ‘pause’ pushbutton that sends a ‘FeedHold’ signal to Mach3, it also stops the VFD.
    To recover from a stop or pause condition a ‘reset’ button is pressed which also sends Mach3 an OEM signal to activate its RESET button and the VFD powers up again. Any time Mach3 is stopped it activates an Enable signal to stop the stepper drivers. Also in series with my pause button is a spindle over temperature switch and in series with my stop button is a relay that indicates if any of the AM882's have gone into alarm.
    Last edited by EddyCurrent; 01-12-2013 at 10:06 PM.

  2. #22
    Quote Originally Posted by EddyCurrent View Post
    There is a ‘pause’ pushbutton that sends a ‘FeedHold’ signal to Mach3, it also stops the VFD.
    To recover from a stop or pause condition a ‘reset’ button is pressed which also sends Mach3 an OEM signal to activate its RESET button and the VFD powers up again.
    Eddy don't do that has when you "Feedhold" you won't want the spindle to stop spinning. It could still be in the material which would cause tool damage.
    Also When you release "Feedhold" Mach won't start the Spindle without an M3 command or OEM code to turn it back on and if you "Feedhold" chances are your in the middle of a job and just want to pause for something like clearing chips etc. . . That's the point of "Feedhold" it's not to be used for Emergency or any Safety feature.

    Now has to the rest of the Limits and E-stop best way debate then it's Simply down to preference.
    I prefer to have E-stop Buttons Kill power to everything. Limits I have separate and just have kill Signals to drives and Send Signals to Control to stop the code.
    If drives have Fault signals like AM882 then they are wired in series with Limits and just Kill signals and inform control.

    Feedhold is not for this purpose and shouldn't be used has such IMO. In Mach's case it also doesn't stop instantly either has it has to clear the Look-ahead buffer first so can't be relied upon to stop quickly.

  3. #23
    Quote Originally Posted by JAZZCNC View Post
    Eddy don't do that has when you "Feedhold" you won't want the spindle to stop spinning. It could still be in the material which would cause tool damage.
    Also When you release "Feedhold" Mach won't start the Spindle without an M3 command or OEM code to turn it back on and if you "Feedhold" chances are your in the middle of a job and just want to pause for something like clearing chips etc. . . That's the point of "Feedhold" it's not to be used for Emergency or any Safety feature.
    I never suggested using it for Emergency or safety use. Regarding leaving spindle turning, I can make it do that, thanks.

    Quote Originally Posted by JAZZCNC View Post
    Feedhold is not for this purpose and shouldn't be used has such IMO. In Mach's case it also doesn't stop instantly either has it has to clear the Look-ahead buffer first so can't be relied upon to stop quickly.
    I'm only using FeedHold from a pause pushbutton and the spindle overtemp so that I can carry on again after assessing the situation, I saw it carries on a while depending on the look-ahead setting. All of these features are easily 'shorted out' in the panel if they become a problem later on.
    Last edited by EddyCurrent; 02-12-2013 at 10:18 AM.

  4. #24
    Quote Originally Posted by EddyCurrent View Post
    I'm only using FeedHold from a pause pushbutton and the spindle overtemp so that I can carry on again after assessing the situation, I saw it carries on a while depending on the look-ahead setting. All of these features are easily 'shorted out' in the panel if they become a problem later on.
    Can tell you 100% It will be a problem from day one if your relying on "feed hold" to stop Instantly because it doesn't. Even with Motion control Card that can process the Code much faster so use lower Lookahead than Mach's PP driver you can't get "feed hold" to stop instantly without losing Steps and that's the whole point of "feed hold" Otherwise you may has well just E-stop and presume lost position.!!

  5. #25
    Quote Originally Posted by JAZZCNC View Post
    Can tell you 100% It will be a problem from day one if your relying on "feed hold" to stop Instantly because it doesn't. Even with Motion control Card that can process the Code much faster so use lower Lookahead than Mach's PP driver you can't get "feed hold" to stop instantly without losing Steps and that's the whole point of "feed hold" Otherwise you may has well just E-stop and presume lost position.!!
    I don't understand why you think I'm wanting it to stop instantly, I know that is doesn't and that's fine because it's not part of any emergency or safety requirement.

  6. #26
    Quote Originally Posted by EddyCurrent View Post
    I don't understand why you think I'm wanting it to stop instantly, I know that is doesn't and that's fine because it's not part of any emergency or safety requirement.
    Don't know myself if being honest. . Lol . . . . Just thought you did from some of the other posts.!! . . . Anyway Crack on and I'll keep Stum in future.!!

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