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Re: [turbocnc] Re: home on a single axis - verificatoin switch

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  • David Goadby
    Thanks for the extra info. Jerry. My limit switches are industrial micro-switches (I always have a few around for my real work) and they are a little coarse in
    Message 1 of 21 , Apr 1, 2003
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      Thanks for the extra info. Jerry.

      My limit switches are industrial micro-switches (I always have a few around
      for my real work) and they are a little coarse in operation which is why I
      use an opto slot for the more accurate position (datum-1 I call it). I don't
      like hardstops - stalled stepper motors remind me of expensive failed
      experiments.... ;-O

      I will look at the G92 source code to check what really happens.

      Thanks again.

      David

      ----- Original Message -----
      From: "Carol & Jerry Jankura" <jerry.jankura@...>
      To: <turbocnc@yahoogroups.com>
      Sent: Tuesday, April 01, 2003 4:52 AM
      Subject: RE: [turbocnc] Re: home on a single axis - verificatoin switch


      > Hi, Dave:
      >
      > > Once the switch changed state, the software would stop pulsing.
      > > Since the software could not see that as zero, I would need to keep
      > > driving the motor. so that both the software went to zero and the
      > > hardware was at a known spot(zero).
      >
      > This is why you'd use the G92 to set Z to zero. Let's assume that, Z =
      1.354
      > units when the limit switch or hard stop causes motion to finish up. In
      the
      > case of the limit switch, I believe (I haven't looked at the code and I
      > don't have limit switches on my mill right now) that the motor would stop
      > and control would return to the next block. At that point, the instruction
      > G92 Z0 would make the computer assume that Z was at location zero and base
      > any other motions in the Z axis from that zero point (you could also issue
      > the instruction G92 Z2.5 and have the computer work such that the locatin
      > that Z was currently at is 2.5)
      >
      > It shouldn't matter if it's a hard or soft stop. The ony caviat is that,
      > with a soft stop from a limit switch, you'd be allowed to move only in the
      > direction opposite to the motion that caused the limit switch to toggle.
      >
      >
      > > This leads me to the idea of putting in a verification switch.
      > > retract the axis and if the endswitch hits, lost down steps occurred
      > > from a dull drill or chips in the hole that spun and did not allow
      > > the drill to cut.
      >
      > > if the verification switch did not make, then the axis may have
      > > gotten stuck and did not retract fully.
      >
      > You could probably use the 'wait for PLC response' code to check for this
      > switch. I'm not sure of the number right now.
      >
      > -- Jerry
      >
      >
      >
      >
      >
      >
      >
      >
      > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
      >
      >
    • Carol & Jerry Jankura
      Hi, David: I would look at the limit switch code, not the G92 code. The G92 code sets your current location to whatever coordinate you specify... i.e. G92 X3
      Message 2 of 21 , Apr 1, 2003
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        Hi, David:

        I would look at the limit switch code, not the G92 code. The G92 code sets
        your current location to whatever coordinate you specify... i.e. G92 X3 sets
        the current location of X to be at 3. You can specify an argument for any or
        all of the axes you've defined, so you can have a total of 8 parameters to
        the G92.

        The real question is what TurboCNC does after it encounters alimit switch. I
        believe that it allows you to back away from the limit, but not move towards
        it until you've backed away. this is exactly the motion that you need.

        BTW, I agree fully with your concerns about running into hard stops as a
        matter of course - and this also means making sure that your limit switches
        aren't placed so they become the hard stops. :)

        -- Jerry


        > My limit switches are industrial micro-switches (I always have a few
        around
        > for my real work) and they are a little coarse in operation which is why I
        > use an opto slot for the more accurate position (datum-1 I call it). I
        don't
        > like hardstops - stalled stepper motors remind me of expensive failed
        > experiments.... ;-O
        >
        > I will look at the G92 source code to check what really happens.
      • Dave Mucha
        Hi Jerry, Seems like this is the David thread. If I understand, it sounds like I could raise my Z till it hit a switch. set that axis with a G92 to be 0.0
        Message 3 of 21 , Apr 1, 2003
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          Hi Jerry,

          Seems like this is the David thread.

          If I understand, it sounds like I could raise my Z till it hit a
          switch. set that axis with a G92 to be 0.0 and them back away.

          This is what I was after when I started this thread. I missed the
          the G92 feature.

          Anybody else amazed at the capabilities of this program ?

          Dave



          --- In turbocnc@yahoogroups.com, "Carol & Jerry Jankura"
          <jerry.jankura@s...> wrote:
          > Hi, David:
          >
          > I would look at the limit switch code, not the G92 code. The G92
          code sets
          > your current location to whatever coordinate you specify... i.e.
          G92 X3 sets
          > the current location of X to be at 3. You can specify an argument
          for any or
          > all of the axes you've defined, so you can have a total of 8
          parameters to
          > the G92.
          >
          > The real question is what TurboCNC does after it encounters alimit
          switch. I
          > believe that it allows you to back away from the limit, but not
          move towards
          > it until you've backed away. this is exactly the motion that you
          need.
          >
          > BTW, I agree fully with your concerns about running into hard stops
          as a
          > matter of course - and this also means making sure that your limit
          switches
          > aren't placed so they become the hard stops. :)
          >
          > -- Jerry
          >
          >
          > > My limit switches are industrial micro-switches (I always have a
          few
          > around
          > > for my real work) and they are a little coarse in operation which
          is why I
          > > use an opto slot for the more accurate position (datum-1 I call
          it). I
          > don't
          > > like hardstops - stalled stepper motors remind me of expensive
          failed
          > > experiments.... ;-O
          > >
          > > I will look at the G92 source code to check what really happens.
        • David Goadby
          Hi Jerry, Aah, the penny drops! In my case I require an override switch as the Geckos are disabled by the over-limit switches. Being pedantic, my first limit
          Message 4 of 21 , Apr 1, 2003
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            Hi Jerry,

            Aah, the penny drops! In my case I require an override switch as the Geckos
            are disabled by the "over-limit" switches. Being pedantic, my first limit
            switches are really datums which is what I want/need. The over-limits are in
            the "should never occur" bracket. A state diagram is called for I think. ;-o

            David

            ----- Original Message -----
            From: "Carol & Jerry Jankura" <jerry.jankura@...>
            To: <turbocnc@yahoogroups.com>
            Sent: Tuesday, April 01, 2003 2:21 PM
            Subject: RE: [turbocnc] Re: home on a single axis - verificatoin switch


            > Hi, David:
            >
            > I would look at the limit switch code, not the G92 code. The G92 code sets
            > your current location to whatever coordinate you specify... i.e. G92 X3
            sets
            > the current location of X to be at 3. You can specify an argument for any
            or
            > all of the axes you've defined, so you can have a total of 8 parameters to
            > the G92.
            >
            > The real question is what TurboCNC does after it encounters alimit switch.
            I
            > believe that it allows you to back away from the limit, but not move
            towards
            > it until you've backed away. this is exactly the motion that you need.
            >
            > BTW, I agree fully with your concerns about running into hard stops as a
            > matter of course - and this also means making sure that your limit
            switches
            > aren't placed so they become the hard stops. :)
            >
            > -- Jerry
            >
            >
            > > My limit switches are industrial micro-switches (I always have a few
            > around
            > > for my real work) and they are a little coarse in operation which is why
            I
            > > use an opto slot for the more accurate position (datum-1 I call it). I
            > don't
            > > like hardstops - stalled stepper motors remind me of expensive failed
            > > experiments.... ;-O
            > >
            > > I will look at the G92 source code to check what really happens.
            >
            >
            >
            >
            >
            >
            >
            >
            > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
            >
            >
          • Carol & Jerry Jankura
            Hi, David: And why would you have to connect the limit to the Gecko drive? Why not connect it to one of the printer port pins and let TurboCNC handle it? --
            Message 5 of 21 , Apr 1, 2003
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              Hi, David:

              And why would you have to connect the limit to the Gecko drive? Why not
              connect it to one of the printer port pins and let TurboCNC handle it?

              -- Jerry


              > Hi Jerry,
              >
              > Aah, the penny drops! In my case I require an override switch as
              > the Geckos
              > are disabled by the "over-limit" switches. Being pedantic, my first limit
              > switches are really datums which is what I want/need. The over-limits are
              in
              > the "should never occur" bracket. A state diagram is called for I
              > think. ;-o
              >
              > David
            • cybermace5
              ... That s a secondary limit switch. If something happens and the first interrupter isn t caught, turning off Gecko power is a LOT better than coming back to a
              Message 6 of 21 , Apr 1, 2003
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                --- In turbocnc@yahoogroups.com, "Carol & Jerry Jankura"
                <jerry.jankura@s...> wrote:
                > Hi, David:
                >
                > And why would you have to connect the limit to the Gecko drive? Why not
                > connect it to one of the printer port pins and let TurboCNC handle it?
                >
                > -- Jerry

                That's a secondary limit switch. If something happens and the first
                interrupter isn't caught, turning off Gecko power is a LOT better than
                coming back to a piece of twisted smoking metal that used to be your
                CNC machine....
              • David Goadby
                Spot on! got the teeshirt for this one. David ... From: cybermace5 To: Sent: Wednesday, April 02, 2003
                Message 7 of 21 , Apr 1, 2003
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                  Spot on! 'got the teeshirt for this one.

                  David

                  ----- Original Message -----
                  From: "cybermace5" <cybermace5@...>
                  To: <turbocnc@yahoogroups.com>
                  Sent: Wednesday, April 02, 2003 4:29 AM
                  Subject: [turbocnc] Re: home on a single axis - verificatoin switch


                  > --- In turbocnc@yahoogroups.com, "Carol & Jerry Jankura"
                  > <jerry.jankura@s...> wrote:
                  > > Hi, David:
                  > >
                  > > And why would you have to connect the limit to the Gecko drive? Why not
                  > > connect it to one of the printer port pins and let TurboCNC handle it?
                  > >
                  > > -- Jerry
                  >
                  > That's a secondary limit switch. If something happens and the first
                  > interrupter isn't caught, turning off Gecko power is a LOT better than
                  > coming back to a piece of twisted smoking metal that used to be your
                  > CNC machine....
                  >
                  >
                  >
                  >
                  >
                  >
                  >
                  > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
                  >
                  >
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