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Adding limit switches

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  • kbucklitch
    Hi Folks I have a Taig mill,converted to CNC control, driven by Mach 3. I have used this for a couple of years without the benefit of limit or home switches.
    Message 1 of 22 , Oct 1, 2008
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      Hi Folks

      I have a Taig mill,converted to CNC control, driven by Mach 3. I have
      used this for a couple of years without the benefit of limit or home
      switches. I am now considering the installation of these switches and
      would appreciate some input.

      Has anyone on the list added limit and/or home switches to their Taig
      mill? If so, could you give me a quick run-through on how you did it.
      A link to a website with illustrations would be much appreciated.

      Thanks.

      Keith
    • blmartech
      i could take some pictures when i get home this evening, wire all switches in the nc (normally closed) configuration. this setup can use any amount of switches
      Message 2 of 22 , Oct 1, 2008
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        i could take some pictures when i get home this evening, wire all
        switches in the nc (normally closed) configuration.

        this setup can use any amount of switches you need and only uses one
        input. Also if anything goes wrong with the wiring or switches it will
        open the circuit.

        <controller input>------<SW1>-----<SW2>-----<SW3>-----<GND>

        i use soft limits and use the switches for home, this seems to work
        well for me. i have seen others use one switch on the x and then place
        a bumper at each extreme. I used microswitches with the roller arm.

        i will post some pics when i get home if no one else chimes in, there
        are some writeups on the web already but dont remember any off hand,
        you could try carter tools im sure there is some information there
        about it.

        --- In taigtools@yahoogroups.com, "kbucklitch" <keith.bucklitch@...>
        wrote:
        >
        > Hi Folks
        >
        > I have a Taig mill,converted to CNC control, driven by Mach 3. I have
        > used this for a couple of years without the benefit of limit or home
        > switches. I am now considering the installation of these switches and
        > would appreciate some input.
        >
        > Has anyone on the list added limit and/or home switches to their Taig
        > mill? If so, could you give me a quick run-through on how you did it.
        > A link to a website with illustrations would be much appreciated.
        >
        > Thanks.
        >
        > Keith
        >
      • kbucklitch
        Thanks. I look forward to seeing the pictures. In the meantime, I will have a look on Nick s website. Keith
        Message 3 of 22 , Oct 1, 2008
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          Thanks. I look forward to seeing the pictures. In the meantime, I
          will have a look on Nick's website.

          Keith



          --- In taigtools@yahoogroups.com, "blmartech" <blmartech@...> wrote:
          >
          > i could take some pictures when i get home this evening, wire all
          > switches in the nc (normally closed) configuration.
          >
          > this setup can use any amount of switches you need and only uses one
          > input. Also if anything goes wrong with the wiring or switches it will
          > open the circuit.
          >
          > <controller input>------<SW1>-----<SW2>-----<SW3>-----<GND>
          >
          > i use soft limits and use the switches for home, this seems to work
          > well for me. i have seen others use one switch on the x and then place
          > a bumper at each extreme. I used microswitches with the roller arm.
          >
          > i will post some pics when i get home if no one else chimes in, there
          > are some writeups on the web already but dont remember any off hand,
          > you could try carter tools im sure there is some information there
          > about it.
          >
          > --- In taigtools@yahoogroups.com, "kbucklitch" <keith.bucklitch@>
          > wrote:
          > >
          > > Hi Folks
          > >
          > > I have a Taig mill,converted to CNC control, driven by Mach 3. I have
          > > used this for a couple of years without the benefit of limit or home
          > > switches. I am now considering the installation of these switches and
          > > would appreciate some input.
          > >
          > > Has anyone on the list added limit and/or home switches to their Taig
          > > mill? If so, could you give me a quick run-through on how you did it.
          > > A link to a website with illustrations would be much appreciated.
          > >
          > > Thanks.
          > >
          > > Keith
          > >
          >
        • blmartech
          i posted some pictures on my website http://www.cognitiveinnovations.com/news.php scroll down to mid page below the probe. ... I have ... switches and ... Taig
          Message 4 of 22 , Oct 1, 2008
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            i posted some pictures on my website

            http://www.cognitiveinnovations.com/news.php

            scroll down to mid page below the probe.



            --- In taigtools@yahoogroups.com, "kbucklitch" <keith.bucklitch@...>
            wrote:
            >
            > Thanks. I look forward to seeing the pictures. In the meantime, I
            > will have a look on Nick's website.
            >
            > Keith
            >
            >
            >
            > --- In taigtools@yahoogroups.com, "blmartech" <blmartech@> wrote:
            > >
            > > i could take some pictures when i get home this evening, wire all
            > > switches in the nc (normally closed) configuration.
            > >
            > > this setup can use any amount of switches you need and only uses one
            > > input. Also if anything goes wrong with the wiring or switches it will
            > > open the circuit.
            > >
            > > <controller input>------<SW1>-----<SW2>-----<SW3>-----<GND>
            > >
            > > i use soft limits and use the switches for home, this seems to work
            > > well for me. i have seen others use one switch on the x and then place
            > > a bumper at each extreme. I used microswitches with the roller arm.
            > >
            > > i will post some pics when i get home if no one else chimes in, there
            > > are some writeups on the web already but dont remember any off hand,
            > > you could try carter tools im sure there is some information there
            > > about it.
            > >
            > > --- In taigtools@yahoogroups.com, "kbucklitch" <keith.bucklitch@>
            > > wrote:
            > > >
            > > > Hi Folks
            > > >
            > > > I have a Taig mill,converted to CNC control, driven by Mach 3.
            I have
            > > > used this for a couple of years without the benefit of limit or home
            > > > switches. I am now considering the installation of these
            switches and
            > > > would appreciate some input.
            > > >
            > > > Has anyone on the list added limit and/or home switches to their
            Taig
            > > > mill? If so, could you give me a quick run-through on how you
            did it.
            > > > A link to a website with illustrations would be much appreciated.
            > > >
            > > > Thanks.
            > > >
            > > > Keith
            > > >
            > >
            >
          • Keith Bucklitch
            Thanks for the link. Reading the accompanying description, it appears that you have only three switches. Is this correct? I had assumed that one needed two
            Message 5 of 22 , Oct 2, 2008
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              Thanks for the link. Reading the accompanying description, it
              appears that you have only three switches. Is this correct? I had
              assumed that one needed two switches for each axis so as to stop the
              system at the extremes of travel at both ends. For example when the
              X axis has reached its left most, or its right most position would
              take two switches.

              Also, have you wired all the switches together in series, or are they
              connected individually to the controller. I have in mind that if
              they were all connected in series, then breaking the circuit at any
              one would stop the system, and only two wires would be needed for the
              control connection.

              Keith


              At 00:24 02/10/2008, you wrote:
              >i posted some pictures on my website
              >
              >http://www.cognitiveinnovations.com/news.php
              >
              >scroll down to mid page below the probe.
              >
              >
              >
              >--- In taigtools@yahoogroups.com, "kbucklitch" <keith.bucklitch@...>
              >wrote:
              > >
              > > Thanks. I look forward to seeing the pictures. In the meantime, I
              > > will have a look on Nick's website.
              > >
              > > Keith
              > >
              > >
              > >
              > > --- In taigtools@yahoogroups.com, "blmartech" <blmartech@> wrote:
              > > >
              > > > i could take some pictures when i get home this evening, wire all
              > > > switches in the nc (normally closed) configuration.
              > > >
              > > > this setup can use any amount of switches you need and only uses one
              > > > input. Also if anything goes wrong with the wiring or switches it will
              > > > open the circuit.
              > > >
              > > > <controller input>------<SW1>-----<SW2>-----<SW3>-----<GND>
              > > >
              > > > i use soft limits and use the switches for home, this seems to work
              > > > well for me. i have seen others use one switch on the x and then place
              > > > a bumper at each extreme. I used microswitches with the roller arm.
              > > >
              > > > i will post some pics when i get home if no one else chimes in, there
              > > > are some writeups on the web already but dont remember any off hand,
              > > > you could try carter tools im sure there is some information there
              > > > about it.
              > > >
              > > > --- In taigtools@yahoogroups.com, "kbucklitch" <keith.bucklitch@>
              > > > wrote:
              > > > >
              > > > > Hi Folks
              > > > >
              > > > > I have a Taig mill,converted to CNC control, driven by Mach 3.
              >I have
              > > > > used this for a couple of years without the benefit of limit or home
              > > > > switches. I am now considering the installation of these
              >switches and
              > > > > would appreciate some input.
              > > > >
              > > > > Has anyone on the list added limit and/or home switches to their
              >Taig
              > > > > mill? If so, could you give me a quick run-through on how you
              >did it.
              > > > > A link to a website with illustrations would be much appreciated.
              > > > >
              > > > > Thanks.
              > > > >
              > > > > Keith
              > > > >
              > > >
              > >
              >
              >
              >
              >------------------------------------
              >
              >To Post a message, send it to:
              >taigtools@yahoogroups.com
              >
              >To Unsubscribe, send a blank message to:
              >taigtools-unsubscribe@yahoogroups.com
              >
              >Let the chips fly!
              >Yahoo! Groups Links
              >
              >
              >
            • blmartech
              I only use 3 for the home switches and have the the other extreme set as a software limit, this way works fine for me and allows me to set my extremes to what
              Message 6 of 22 , Oct 2, 2008
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                I only use 3 for the home switches and have the the other extreme set
                as a software limit, this way works fine for me and allows me to set
                my extremes to what ever i want as long as i know a distance from
                home, some people use one switch in the middle of the x axis and a
                bumper on each end of the table,

                i have each switch ran seperatly but plan on wiring them in series to
                free up 2 more inputs as only one input is needed for all the switches
                because it only homes one axis at a time.





                --- In taigtools@yahoogroups.com, Keith Bucklitch
                <keith.bucklitch@...> wrote:
                >
                > Thanks for the link. Reading the accompanying description, it
                > appears that you have only three switches. Is this correct? I had
                > assumed that one needed two switches for each axis so as to stop the
                > system at the extremes of travel at both ends. For example when the
                > X axis has reached its left most, or its right most position would
                > take two switches.
                >
                > Also, have you wired all the switches together in series, or are they
                > connected individually to the controller. I have in mind that if
                > they were all connected in series, then breaking the circuit at any
                > one would stop the system, and only two wires would be needed for the
                > control connection.
                >
                > Keith
                >
                >
                > At 00:24 02/10/2008, you wrote:
                > >i posted some pictures on my website
                > >
                > >http://www.cognitiveinnovations.com/news.php
                > >
                > >scroll down to mid page below the probe.
                > >
                > >
                > >
                > >--- In taigtools@yahoogroups.com, "kbucklitch" <keith.bucklitch@>
                > >wrote:
                > > >
                > > > Thanks. I look forward to seeing the pictures. In the meantime, I
                > > > will have a look on Nick's website.
                > > >
                > > > Keith
                > > >
                > > >
                > > >
                > > > --- In taigtools@yahoogroups.com, "blmartech" <blmartech@> wrote:
                > > > >
                > > > > i could take some pictures when i get home this evening, wire all
                > > > > switches in the nc (normally closed) configuration.
                > > > >
                > > > > this setup can use any amount of switches you need and only
                uses one
                > > > > input. Also if anything goes wrong with the wiring or switches
                it will
                > > > > open the circuit.
                > > > >
                > > > > <controller input>------<SW1>-----<SW2>-----<SW3>-----<GND>
                > > > >
                > > > > i use soft limits and use the switches for home, this seems to
                work
                > > > > well for me. i have seen others use one switch on the x and
                then place
                > > > > a bumper at each extreme. I used microswitches with the
                roller arm.
                > > > >
                > > > > i will post some pics when i get home if no one else chimes
                in, there
                > > > > are some writeups on the web already but dont remember any off
                hand,
                > > > > you could try carter tools im sure there is some information there
                > > > > about it.
                > > > >
                > > > > --- In taigtools@yahoogroups.com, "kbucklitch" <keith.bucklitch@>
                > > > > wrote:
                > > > > >
                > > > > > Hi Folks
                > > > > >
                > > > > > I have a Taig mill,converted to CNC control, driven by Mach 3.
                > >I have
                > > > > > used this for a couple of years without the benefit of limit
                or home
                > > > > > switches. I am now considering the installation of these
                > >switches and
                > > > > > would appreciate some input.
                > > > > >
                > > > > > Has anyone on the list added limit and/or home switches to their
                > >Taig
                > > > > > mill? If so, could you give me a quick run-through on how you
                > >did it.
                > > > > > A link to a website with illustrations would be much
                appreciated.
                > > > > >
                > > > > > Thanks.
                > > > > >
                > > > > > Keith
                > > > > >
                > > > >
                > > >
                > >
                > >
                > >
                > >------------------------------------
                > >
                > >To Post a message, send it to:
                > >taigtools@yahoogroups.com
                > >
                > >To Unsubscribe, send a blank message to:
                > >taigtools-unsubscribe@yahoogroups.com
                > >
                > >Let the chips fly!
                > >Yahoo! Groups Links
                > >
                > >
                > >
                >
              • Keith Bucklitch
                Many thanks Kristin. I would very much like to see some pictures. Keith
                Message 7 of 22 , Oct 3, 2008
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                  Many thanks Kristin.

                  I would very much like to see some pictures.

                  Keith



                  At 19:18 02/10/2008, you wrote:
                  >Keith,
                  >
                  >I think it depends on the software your using, I'm using Mach and it
                  >lets you set the soft limits so as long as you have one switch on
                  >each axis to call "home" you can program the opposite direction limit
                  >then Mach treats the switch as a limit or home switch depending on
                  >what it's doing. I would run individual shielded cable to each switch
                  >and then to a terminal strip where you can wire them in series just
                  >to keep the noise problems at bay. I made some mounts from 5/8 dia
                  >aluminum rod about an inch long, milled a 1/4" slot to fit over the
                  >leadscrew mount plate and used 6-32 setscrews to attach it, the
                  >switches are mounted on another flat milled on the rod this saved me
                  >having to remove everything to drill mounting holes. One of these
                  >days I'll get around to some pictures when I get it all sorted out.
                  >
                  >Kristin
                  >
                  >
                  >--- In taigtools@yahoogroups.com, Keith Bucklitch
                  ><keith.bucklitch@...> wrote:
                  > >
                  > > Thanks for the link. Reading the accompanying description, it
                  > > appears that you have only three switches. Is this correct? I had
                  > > assumed that one needed two switches for each axis so as to stop
                  >the
                  > > system at the extremes of travel at both ends. For example when
                  >the
                  > > X axis has reached its left most, or its right most position would
                  > > take two switches.
                  > >
                  > > Also, have you wired all the switches together in series, or are
                  >they
                  > > connected individually to the controller. I have in mind that if
                  > > they were all connected in series, then breaking the circuit at any
                  > > one would stop the system, and only two wires would be needed for
                  >the
                  > > control connection.
                  > >
                  > > Keith
                  >
                  >
                  >
                  >------------------------------------
                  >
                  >To Post a message, send it to:
                  >taigtools@yahoogroups.com
                  >
                  >To Unsubscribe, send a blank message to:
                  >taigtools-unsubscribe@yahoogroups.com
                  >
                  >Let the chips fly!
                  >Yahoo! Groups Links
                  >
                  >
                  >
                • Bertho Boman
                  I finally added some pictures and info on Taig home switches. See: http://www.vinland.com/Home-Switches.html Bertho From: taigtools kbucklitch Sent:
                  Message 8 of 22 , Oct 4, 2008
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                    I finally added some pictures and info on Taig home switches. See:

                    http://www.vinland.com/Home-Switches.html

                    Bertho



                    From: taigtools kbucklitch Sent: Wednesday, October 01, 2008 05:54
                    Hi Folks

                    I have a Taig mill,converted to CNC control, driven by Mach 3. I have
                    used this for a couple of years without the benefit of limit or home
                    switches. I am now considering the installation of these switches and
                    would appreciate some input.

                    Has anyone on the list added limit and/or home switches to their Taig
                    mill? If so, could you give me a quick run-through on how you did it.
                    A link to a website with illustrations would be much appreciated.

                    Thanks.






                    [Non-text portions of this message have been removed]
                  • Keith Bucklitch
                    Some excellent pictures there Bertho. Many thanks. It appears that you only use one switch per axis. How do you prevent too much travel in the other
                    Message 9 of 22 , Oct 4, 2008
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                      Some excellent pictures there Bertho. Many thanks.

                      It appears that you only use one switch per axis. How do you prevent
                      too much travel in the other direction?

                      Also, if the limit switches cut off the power to the steppers/servos,
                      thereby bringing the system to a halt, how do you reverse it to get
                      back to a safe working position? (I am using Mach 3.)

                      Keith.


                      At 15:14 04/10/2008, you wrote:
                      >I finally added some pictures and info on Taig home switches. See:
                      >
                      >http://www.vinland.com/Home-Switches.html
                      >
                      >Bertho
                      >
                      >
                      >
                      >From: taigtools kbucklitch Sent: Wednesday, October 01, 2008 05:54
                      >Hi Folks
                      >
                      >I have a Taig mill,converted to CNC control, driven by Mach 3. I have
                      >used this for a couple of years without the benefit of limit or home
                      >switches. I am now considering the installation of these switches and
                      >would appreciate some input.
                      >
                      >Has anyone on the list added limit and/or home switches to their Taig
                      >mill? If so, could you give me a quick run-through on how you did it.
                      >A link to a website with illustrations would be much appreciated.
                      >
                      >Thanks.
                      >
                      >
                      >
                      >
                      >
                      >
                      >[Non-text portions of this message have been removed]
                      >
                      >
                      >------------------------------------
                      >
                      >To Post a message, send it to:
                      >taigtools@yahoogroups.com
                      >
                      >To Unsubscribe, send a blank message to:
                      >taigtools-unsubscribe@yahoogroups.com
                      >
                      >Let the chips fly!
                      >Yahoo! Groups Links
                      >
                      >
                      >
                    • Bertho Boman
                      Hi Keith, The switches are strictly home switches. Eventually I will add limit switches on all axis/directions and then the optical precision ones will be used
                      Message 10 of 22 , Oct 4, 2008
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                        Hi Keith,

                        The switches are strictly home switches. Eventually I will add limit
                        switches on all axis/directions and then the optical precision ones will be
                        used for the home function.



                        I am also working on the conversion of an oversized "Bridge port" clone and
                        it has servos. The motors are powered through safety relays so when
                        disabled the relays shorts the motors (DC brush type) and I get instant
                        electronic braking function.



                        I am also using Mach 3.

                        Bertho



                        From: Keith Bucklitch Sent: Saturday, October 04, 2008 10:44



                        Some excellent pictures there Bertho. Many thanks.

                        It appears that you only use one switch per axis. How do you prevent
                        too much travel in the other direction?

                        Also, if the limit switches cut off the power to the steppers/servos,
                        thereby bringing the system to a halt, how do you reverse it to get
                        back to a safe working position? (I am using Mach 3.)

                        Keith.





                        [Non-text portions of this message have been removed]
                      • budman6899
                        Keith, Just something else to keep in mind when doing home and/or limit switches. Always try to mount them in such a way that they can t be crushed or crashed
                        Message 11 of 22 , Oct 4, 2008
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                          Keith,

                          Just something else to keep in mind when doing home and/or limit
                          switches. Always try to mount them in such a way that they can't be
                          crushed or crashed into (like I've done at one point) so the lever
                          gets hit sideways and not directly into it.

                          Also, try to keep the switches themselves as stationary as possible,
                          this way you won't get a lot of wire movement so weaken the wires
                          over time. I realize this isn't always possible, like mounting a
                          switch on the Y axis saddle to trigger the X axis, but try to keep it
                          as a minimum.

                          Hope that helps-

                          Dave

                          --- In taigtools@yahoogroups.com, Keith Bucklitch
                          <keith.bucklitch@...> wrote:
                          >
                          > Thanks for the link. Reading the accompanying description, it
                          > appears that you have only three switches. Is this correct? I had
                          > assumed that one needed two switches for each axis so as to stop
                          the
                          > system at the extremes of travel at both ends. For example when
                          the
                          > X axis has reached its left most, or its right most position would
                          > take two switches.
                          >
                          > Also, have you wired all the switches together in series, or are
                          they
                          > connected individually to the controller. I have in mind that if
                          > they were all connected in series, then breaking the circuit at any
                          > one would stop the system, and only two wires would be needed for
                          the
                          > control connection.
                          >
                          > Keith
                          >
                        • Keith Bucklitch
                          Hello Bertho. Now I am confused! Can someone define home switches and limit switches. My understanding was that home switches locate the table (and the head)
                          Message 12 of 22 , Oct 5, 2008
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                            Hello Bertho.

                            Now I am confused! Can someone define home switches and limit
                            switches. My understanding was that home switches locate the table
                            (and the head) at defined positions which become X0, Y0 and
                            Z(whatever). Limit switches are switches that turn off the power to
                            the steppers/servos so as to stop table movement before reaching a
                            dangerous point/extreme end of travel. Bertho's example appeared to
                            me to be limit switches when I saw the pictures, so, does anyone have
                            both limit AND home switches on their machine? If so, how are the
                            two sets of switches fixed/applied and controlled?

                            Keith


                            At 21:03 04/10/2008, you wrote:
                            >Hi Keith,
                            >
                            >The switches are strictly home switches. Eventually I will add limit
                            >switches on all axis/directions and then the optical precision ones will be
                            >used for the home function.
                            >
                            >
                            >
                            >I am also working on the conversion of an oversized "Bridge port" clone and
                            >it has servos. The motors are powered through safety relays so when
                            >disabled the relays shorts the motors (DC brush type) and I get instant
                            >electronic braking function.
                            >
                            >
                            >
                            >I am also using Mach 3.
                            >
                            >Bertho
                            >
                            >
                            >
                            >From: Keith Bucklitch Sent: Saturday, October 04, 2008 10:44
                            >
                            >
                            >
                            >Some excellent pictures there Bertho. Many thanks.
                            >
                            >It appears that you only use one switch per axis. How do you prevent
                            >too much travel in the other direction?
                            >
                            >Also, if the limit switches cut off the power to the steppers/servos,
                            >thereby bringing the system to a halt, how do you reverse it to get
                            >back to a safe working position? (I am using Mach 3.)
                            >
                            >Keith.
                            >
                            >
                            >
                            >
                            >
                            >[Non-text portions of this message have been removed]
                            >
                            >
                            >------------------------------------
                            >
                            >To Post a message, send it to:
                            >taigtools@yahoogroups.com
                            >
                            >To Unsubscribe, send a blank message to:
                            >taigtools-unsubscribe@yahoogroups.com
                            >
                            >Let the chips fly!
                            >Yahoo! Groups Links
                            >
                            >
                            >
                          • Keith Bucklitch
                            Thanks Dave. I had in mind to use the lever type micro switches with a roller on the lever arm. That should keep the actual switch body out of the way of
                            Message 13 of 22 , Oct 5, 2008
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                              Thanks Dave.

                              I had in mind to use the lever type micro switches with a roller on
                              the lever arm. That should keep the actual switch body out of the
                              way of moving tables etc. I note that Maplin have them listed as
                              stock items for a pound or so.

                              Keith


                              At 21:50 04/10/2008, you wrote:
                              >Keith,
                              >
                              >Just something else to keep in mind when doing home and/or limit
                              >switches. Always try to mount them in such a way that they can't be
                              >crushed or crashed into (like I've done at one point) so the lever
                              >gets hit sideways and not directly into it.
                              >
                              >Also, try to keep the switches themselves as stationary as possible,
                              >this way you won't get a lot of wire movement so weaken the wires
                              >over time. I realize this isn't always possible, like mounting a
                              >switch on the Y axis saddle to trigger the X axis, but try to keep it
                              >as a minimum.
                              >
                              >Hope that helps-
                              >
                              >Dave
                              >
                              >--- In taigtools@yahoogroups.com, Keith Bucklitch
                              ><keith.bucklitch@...> wrote:
                              > >
                              > > Thanks for the link. Reading the accompanying description, it
                              > > appears that you have only three switches. Is this correct? I had
                              > > assumed that one needed two switches for each axis so as to stop
                              >the
                              > > system at the extremes of travel at both ends. For example when
                              >the
                              > > X axis has reached its left most, or its right most position would
                              > > take two switches.
                              > >
                              > > Also, have you wired all the switches together in series, or are
                              >they
                              > > connected individually to the controller. I have in mind that if
                              > > they were all connected in series, then breaking the circuit at any
                              > > one would stop the system, and only two wires would be needed for
                              >the
                              > > control connection.
                              > >
                              > > Keith
                              > >
                              >
                              >
                              >
                              >------------------------------------
                              >
                              >To Post a message, send it to:
                              >taigtools@yahoogroups.com
                              >
                              >To Unsubscribe, send a blank message to:
                              >taigtools-unsubscribe@yahoogroups.com
                              >
                              >Let the chips fly!
                              >Yahoo! Groups Links
                              >
                              >
                              >
                            • wildhorsesoftware
                              Keith, Much of the description of the PHYSICAL implementation of home and limit switches has to do with personal decisions as to how to set up your machine.
                              Message 14 of 22 , Oct 5, 2008
                              • 0 Attachment
                                Keith,

                                Much of the description of the PHYSICAL implementation of home and
                                limit switches has to do with personal decisions as to how to set up
                                your machine. Let me explain:

                                I will define how I have my machine configured. I use Mach3 so some
                                of what I say will be specific to that program. For simplicity I
                                will describe only the X axis.

                                I have my machine set so that the movement of the table causes the
                                work piece movement to mimic the typical drawing of a part. That
                                is, the lower left corner of the work piece is the origin for
                                measurements with measurements on the X axis increasing from left to
                                right.

                                Disregarding the Z axis for purposes of this discussion, the fact
                                that, on a mill, the tool remains stationary and the work piece
                                moves, in order for the coordinates of the (X axis) table to mimic
                                the drawing of the work piece, the coordinate values must increase
                                as the table moves from right to left.

                                I have my machine set up with a switch that is activated when the
                                table is at the extreme right position. This switch servers the
                                dual purpose being a home AND a limit switch. This is accomplished
                                in Mach3 by assigning the same port/pin numbers to both the Home
                                and "X axis negative limit" signals.

                                This results in the following actions:

                                When I "Home" my X axis, the table moves from left to right at the
                                speed set for homing (usually fairly slow). When the switch is
                                activated the table reverses direction and moves from right to left
                                just enough to move off the switch. This is the "Zero" or "Home"
                                position for my X axis. If the physical zero position of the work
                                piece is at another position, I must set the offsets for this piece
                                so that the "working" zero position corresponds to the zero point on
                                the work piece.

                                As the machine operates, the software monitors the condition of the
                                Home/Limit switch. If the table moves far enough to the right to
                                activate this switch, the software recognizes this as the Limit for
                                the X axis and shuts down the machine movement.

                                At the opposite end of the table is a second switch. The port/pin
                                for this switch is assigned as the limit for the extreme leftward
                                movement of the table. During table movement, if this switch is
                                activated, the software recognizes that the table has reached it's
                                extreme leftward movement and shuts down movement.

                                There are numerous methods to mount and configure Home/Limit
                                switches. It is possible to use a third switch as the Home switch if
                                you want the Home position of your table to be at a place other than
                                the extreme limit of travel. IMHO this is unnecessary since most
                                software allows you to set offsets for the work piece.

                                In my configuration, the switches are mounted on the moving table,
                                thus requiring a switch at each end of the table. It is possible to
                                have a single stationary switch activated by multiple activation
                                mechanisms (usually some sort of ramp mounted on the moving table).

                                To further complicate matters, it is actually possible (in Mach3) to
                                use a single Port/Pin for the Home and Limit switches on all 3
                                axis. To do this the switches must be wired properly. The primary
                                disadvantage of this configuration is that when a limit signal is
                                activated, the software does not know which axis triggered the limit
                                signal. But it is generally unnecessary for the software to know
                                this since it shuts down ALL movement when ANY limit is activated.

                                It is also possible to set "soft" limits at the extreme movement of
                                one direction of movement instead of using a second switch. The
                                problem with this is that it depends upon the software "knowing"
                                where the table is PHYSICALLY located. If the software loses track
                                of the physical position of the table, it is possible for it to over
                                run the physical limits of the machine. Switches do not require
                                that the software have a knowledge of the physical location of the
                                table. If a limit switch is activated, the machine stops no matter
                                what the software thinks the current table position is.

                                Hope I haven't confused you more than I've helped. Once you grasp
                                the concepts of the interaction of the software, switch state (open
                                or closed), Port/Pin assignments and table position, the subject of
                                Home/Limit switches is a lot easier to implement than it is to
                                explain.

                                Regards,
                                Gary
                                www.mypage.net

                                --- In taigtools@yahoogroups.com, Keith Bucklitch
                                <keith.bucklitch@...> wrote:
                                >
                                > Hello Bertho.
                                >
                                > Now I am confused! Can someone define home switches and limit
                                > switches. My understanding was that home switches locate the
                                table
                                > (and the head) at defined positions which become X0, Y0 and
                                > Z(whatever). Limit switches are switches that turn off the power
                                to
                                > the steppers/servos so as to stop table movement before reaching a
                                > dangerous point/extreme end of travel. Bertho's example appeared
                                to
                                > me to be limit switches when I saw the pictures, so, does anyone
                                have
                                > both limit AND home switches on their machine? If so, how are the
                                > two sets of switches fixed/applied and controlled?
                                >
                                > Keith
                                >
                              • Will Schmit
                                I think it is important to realize that 0,0,0 (origin) and home are different concepts. The wild idea that a switch could reliably tell the machine that it
                                Message 15 of 22 , Oct 5, 2008
                                • 0 Attachment
                                  I think it is important to realize that 0,0,0 (origin) and "home" are different concepts.
                                  The wild idea that a switch could reliably tell the machine that it has arrived at any specific location is folly.
                                  The idea that it is telling the software that the tool is "out of the way" is more realistic. The best switch will never be repeatable.

                                  I am not familiar with Mach.
                                  It is entirely possible (and probable) that is will add or subtract from its "known position" to traverse to the origin (0,0,0).



                                  ----- Original Message ----
                                  From: kd006 <kd006@...>
                                  To: taigtools@yahoogroups.com
                                  Sent: Sunday, October 5, 2008 2:21:44 PM
                                  Subject: [taigtools] Re: Home switches, was Adding limit switches


                                  Keith,

                                  Not sure if this will help but with Mach at least clicking the "Ref
                                  All Home" on the screen runs the Z,X and Y one at a time to contact
                                  the switches, this sets "machine coordinates" at 0,0,0. After that
                                  Mach treats the same switches as limit switches and there are "soft
                                  (ware)" limits you can specify to limit motion in the other
                                  direction. I know the feeling I am still confused by all this! But
                                  there are Machine coordinates and then Work coordinates that are used
                                  to cut a part.

                                  Kristin

                                  --- In taigtools@yahoogrou ps.com, Keith Bucklitch
                                  <keith.bucklitch@ ...> wrote:
                                  >
                                  > Hello Bertho.
                                  >
                                  > Now I am confused! Can someone define home switches and limit
                                  > switches. My understanding was that home switches locate the table
                                  > (and the head) at defined positions which become X0, Y0 and
                                  > Z(whatever). Limit switches are switches that turn off the power
                                  to
                                  > the steppers/servos so as to stop table movement before reaching a
                                  > dangerous point/extreme end of travel. Bertho's example appeared
                                  to
                                  > me to be limit switches when I saw the pictures, so, does anyone
                                  have
                                  > both limit AND home switches on their machine? If so, how are the
                                  > two sets of switches fixed/applied and controlled?
                                  >
                                  > Keith
                                  >
                                  >
                                  > At 21:03 04/10/2008, you wrote:
                                  > >Hi Keith,
                                  > >
                                  > >The switches are strictly home switches. Eventually I will add
                                  limit
                                  > >switches on all axis/directions and then the optical precision
                                  ones will be
                                  > >used for the home function.
                                  > >
                                  > >
                                  > >
                                  > >I am also working on the conversion of an oversized "Bridge port"
                                  clone and
                                  > >it has servos. The motors are powered through safety relays so
                                  when
                                  > >disabled the relays shorts the motors (DC brush type) and I get
                                  instant
                                  > >electronic braking function.
                                  > >
                                  > >
                                  > >
                                  > >I am also using Mach 3.
                                  > >
                                  > >Bertho
                                  > >
                                  > >
                                  > >
                                  > >From: Keith Bucklitch Sent: Saturday, October 04, 2008 10:44
                                  > >
                                  > >
                                  > >
                                  > >Some excellent pictures there Bertho. Many thanks.
                                  > >
                                  > >It appears that you only use one switch per axis. How do you
                                  prevent
                                  > >too much travel in the other direction?
                                  > >
                                  > >Also, if the limit switches cut off the power to the
                                  steppers/servos,
                                  > >thereby bringing the system to a halt, how do you reverse it to get
                                  > >back to a safe working position? (I am using Mach 3.)
                                  > >
                                  > >Keith.
                                  > >
                                  > >
                                  > >
                                  > >
                                  > >
                                  > >[Non-text portions of this message have been removed]
                                  > >
                                  > >
                                  > >----------- --------- --------- -------
                                  > >
                                  > >To Post a message, send it to:
                                  > >taigtools@yahoogrou ps.com
                                  > >
                                  > >To Unsubscribe, send a blank message to:
                                  > >taigtools-unsubscri be@yahoogroups. com
                                  > >
                                  > >Let the chips fly!
                                  > >Yahoo! Groups Links
                                  > >
                                  > >
                                  > >
                                  >



                                  [Non-text portions of this message have been removed]
                                • Bertho Boman
                                  Kristin pretty much answered the question but let me add a couple of things: If optical switches or micro switches are used with a long ramp, for example half
                                  Message 16 of 22 , Oct 5, 2008
                                  • 0 Attachment
                                    Kristin pretty much answered the question but let me add a couple of things:

                                    If optical switches or micro switches are used with a long ramp, for example
                                    half the table length, a "Reference" position can be had in the center or
                                    anywhere. Having it near the center will make the find "Reference" faster.
                                    The problem with just a single cam or flag is that the sensor might be on
                                    the wrong side of the cam and it keeps searching in the wrong direction. If
                                    manually moved to the other side of the cam and then the "Find Reference"
                                    command is issued it is OK.



                                    If the home switches are mounted near the end of travel it can automatically
                                    be given a "Find home" command. In that case the reference position would be
                                    identical to the home position.



                                    A further thing to think about is "Home" normally implies the limit
                                    positions and from there a work position is calculated, for example, the
                                    wise corner.



                                    As I mentioned, for a high power unit I will have independent limit switches
                                    that are not tied into any electronic drivers or anything; they cut the
                                    motor power and short the motor for instant motor braking.



                                    The temporary micro switches on my mill are crush proof, the Z & Y will
                                    hit the mechanical limits before touching the switch bodies. The steppers
                                    are not strong enough to do any damage when hitting the end which they
                                    normally do not do anyhow

                                    Bertho



                                    From: taigtools@yahoogroups.com [mailto:taigtools@yahoogroups.com] On Behalf
                                    Of Keith Bucklitch
                                    Sent: Sunday, October 05, 2008 14:50
                                    To: taigtools@yahoogroups.com
                                    Subject: RE: [taigtools] Home switches, was Adding limit switches



                                    Hello Bertho.

                                    Now I am confused! Can someone define home switches and limit
                                    switches. My understanding was that home switches locate the table
                                    (and the head) at defined positions which become X0, Y0 and
                                    Z(whatever). Limit switches are switches that turn off the power to
                                    the steppers/servos so as to stop table movement before reaching a
                                    dangerous point/extreme end of travel. Bertho's example appeared to
                                    me to be limit switches when I saw the pictures, so, does anyone have
                                    both limit AND home switches on their machine? If so, how are the
                                    two sets of switches fixed/applied and controlled?

                                    Keith

                                    At 21:03 04/10/2008, you wrote:
                                    >Hi Keith,
                                    >
                                    >The switches are strictly home switches. Eventually I will add limit
                                    >switches on all axis/directions and then the optical precision ones will be
                                    >used for the home function.
                                    >
                                    >
                                    >
                                    >I am also working on the conversion of an oversized "Bridge port" clone and
                                    >it has servos. The motors are powered through safety relays so when
                                    >disabled the relays shorts the motors (DC brush type) and I get instant
                                    >electronic braking function.
                                    >
                                    >
                                    >
                                    >I am also using Mach 3.
                                    >
                                    >Bertho
                                    >
                                    >
                                    >
                                    >From: Keith Bucklitch Sent: Saturday, October 04, 2008 10:44
                                    >
                                    >
                                    >
                                    >Some excellent pictures there Bertho. Many thanks.
                                    >
                                    >It appears that you only use one switch per axis. How do you prevent
                                    >too much travel in the other direction?
                                    >
                                    >Also, if the limit switches cut off the power to the steppers/servos,
                                    >thereby bringing the system to a halt, how do you reverse it to get
                                    >back to a safe working position? (I am using Mach 3.)
                                    >
                                    >Keith.





                                    [Non-text portions of this message have been removed]
                                  • Bertho Boman
                                    Oops, I mislabeled the subject! Thanks Gary s for very good description. To avoid confusion, maybe we should add another definition: Hardwired limit switches
                                    Message 17 of 22 , Oct 5, 2008
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                                      Oops, I mislabeled the subject!

                                      Thanks Gary's for very good description.



                                      To avoid confusion, maybe we should add another definition: Hardwired limit
                                      switches vs. electronic I-O limit switches.



                                      In both cases the physical switches and mounting would be identical but the
                                      basic function is drastically different. With the switches tied into Mach 3
                                      or any other controller, we must trust that the software and the PC itself
                                      never will fail. If the software gets confused and goes full speed in one
                                      direction, how can we trust that it will obey and check the limit switches?



                                      Hardwired limit switches typically are connected to control a power relay
                                      after the driver (which also could fail).



                                      These issues are not serious on a little Taig but on big machines there can
                                      be serious injuries. For example, look a high power cutting laser that
                                      moves 10 x 20 feet and cuts inch thick steel. If the software fails someone
                                      could get killed so the limit switches better work.

                                      Bertho



                                      [Non-text portions of this message have been removed]
                                    • Bertho Boman
                                      Home, or reference, or 0,0,0 can be just different names with or without a calculated offset. I completely fail to understand why you state that a switch
                                      Message 18 of 22 , Oct 5, 2008
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                                        Home, or reference, or 0,0,0 can be just different names with or without a
                                        calculated offset.



                                        I completely fail to understand why you state that a switch cannot be
                                        accurate. Various home sensors are normally used. Here is an example of a
                                        very accurate switch, much better than the mill itself:

                                        http://www.vinland.com/Opto-Interrupter.html



                                        Even a regular micro switch is surprisingly accurate.

                                        Bertho



                                        From: Will Schmit Sent: Sunday, October 05, 2008 17:47
                                        I think it is important to realize that 0,0,0 (origin) and "home" are
                                        different concepts.


                                        The wild idea that a switch could reliably tell the machine that it has
                                        arrived at any specific location is folly.
                                        The idea that it is telling the software that the tool is "out of the way"
                                        is more realistic. The best switch will never be repeatable.





                                        [Non-text portions of this message have been removed]
                                      • Will Schmit
                                        Thanks Bertho. I have used them in the past, as encoder counters for focusing tapes in a huge camera I was working on. As you noted, they failed with the least
                                        Message 19 of 22 , Oct 6, 2008
                                        • 0 Attachment
                                          Thanks Bertho.
                                          I have used them in the past, as encoder counters for focusing tapes in a huge camera I was working on.
                                          As you noted, they failed with the least dust they go south.
                                          I stand corrected.



                                          ----- Original Message ----
                                          From: Bertho Boman <boman01@...>
                                          To: taigtools@yahoogroups.com
                                          Sent: Sunday, October 5, 2008 4:39:43 PM
                                          Subject: RE: [taigtools] Re: Home switches, was Adding limit switches


                                          Home, or reference, or 0,0,0 can be just different names with or without a
                                          calculated offset.

                                          I completely fail to understand why you state that a switch cannot be
                                          accurate. Various home sensors are normally used. Here is an example of a
                                          very accurate switch, much better than the mill itself:

                                          http://www.vinland com/Opto- Interrupter. html

                                          Even a regular micro switch is surprisingly accurate.

                                          Bertho

                                          From: Will Schmit Sent: Sunday, October 05, 2008 17:47
                                          I think it is important to realize that 0,0,0 (origin) and "home" are
                                          different concepts.

                                          The wild idea that a switch could reliably tell the machine that it has
                                          arrived at any specific location is folly.
                                          The idea that it is telling the software that the tool is "out of the way"
                                          is more realistic. The best switch will never be repeatable.

                                          [Non-text portions of this message have been removed]



                                          [Non-text portions of this message have been removed]
                                        • Keith Bucklitch
                                          Thanks Guys for the informative comments recently posted. I need to sit down and read through them to determine the best way to proceed from here. Just one
                                          Message 20 of 22 , Oct 6, 2008
                                          • 0 Attachment
                                            Thanks Guys for the informative comments recently posted. I need to
                                            sit down and read through them to determine the best way to proceed
                                            from here.

                                            Just one point I am still unclear about. No one has answered my
                                            query as to how one starts up the system once it has been brought to
                                            a halt by the activation of a limit switch. Does one simply issue a
                                            MDI command to move away from the limit position? Obviously the
                                            software is still working, but is power still on tap to the
                                            motors? Perhaps I have got the wrong end of the stick here. I had
                                            in mind that when a limit switch was activated, it stopped EVERYTHING
                                            on the machine - spindle, steppers, coolant etc. Does it simply stop
                                            the stepper motors from moving any further in a particular direction?

                                            Keith


                                            At 23:39 05/10/2008, you wrote:
                                            >Home, or reference, or 0,0,0 can be just different names with or without a
                                            >calculated offset.
                                            >
                                            >
                                            >
                                            >I completely fail to understand why you state that a switch cannot be
                                            >accurate. Various home sensors are normally used. Here is an example of a
                                            >very accurate switch, much better than the mill itself:
                                            >
                                            >http://www.vinland.com/Opto-Interrupter.html
                                            >
                                            >
                                            >
                                            >Even a regular micro switch is surprisingly accurate.
                                            >
                                            >Bertho
                                            >
                                            >
                                            >
                                            >From: Will Schmit Sent: Sunday, October 05, 2008 17:47
                                            >I think it is important to realize that 0,0,0 (origin) and "home" are
                                            >different concepts.
                                            >
                                            >
                                            >The wild idea that a switch could reliably tell the machine that it has
                                            >arrived at any specific location is folly.
                                            >The idea that it is telling the software that the tool is "out of the way"
                                            >is more realistic. The best switch will never be repeatable.
                                            >
                                            >
                                            >
                                            >
                                            >
                                            >[Non-text portions of this message have been removed]
                                            >
                                            >
                                            >------------------------------------
                                            >
                                            >To Post a message, send it to:
                                            >taigtools@yahoogroups.com
                                            >
                                            >To Unsubscribe, send a blank message to:
                                            >taigtools-unsubscribe@yahoogroups.com
                                            >
                                            >Let the chips fly!
                                            >Yahoo! Groups Links
                                            >
                                            >
                                            >
                                          • Bertho Boman
                                            Hi Will, Yes, dust and dirt is a problem. That is why I have not put them on my mill yet. I am working on a protective enclosure for the switch where it
                                            Message 21 of 22 , Oct 6, 2008
                                            • 0 Attachment
                                              Hi Will,

                                              Yes, dust and dirt is a problem. That is why I have not put them on my mill
                                              yet. I am working on a protective enclosure for the switch where it
                                              basically will be in a sealed environment.

                                              Have a great day,

                                              Bertho



                                              From: Will Schmit Sent: Monday, October 06, 2008 07:27
                                              Thanks Bertho.
                                              I have used them in the past, as encoder counters for focusing tapes in a
                                              huge camera I was working on.
                                              As you noted, they failed with the least dust they go south.
                                              I stand corrected.

                                              ----- Original Message ----
                                              From: Bertho Boman Sent: Sunday, October 5, 2008 4:39:43 PM

                                              Home, or reference, or 0,0,0 can be just different names with or without a
                                              calculated offset.

                                              I completely fail to understand why you state that a switch cannot be
                                              accurate. Various home sensors are normally used. Here is an example of a
                                              very accurate switch, much better than the mill itself:

                                              http://www.vinland com/Opto- Interrupter. html

                                              Even a regular micro switch is surprisingly accurate.

                                              Bertho

                                              From: Will Schmit Sent: Sunday, October 05, 2008 17:47
                                              I think it is important to realize that 0,0,0 (origin) and "home" are
                                              different concepts.

                                              The wild idea that a switch could reliably tell the machine that it has
                                              arrived at any specific location is folly.
                                              The idea that it is telling the software that the tool is "out of the way"
                                              is more realistic. The best switch will never be repeatable.





                                              [Non-text portions of this message have been removed]
                                            • wildhorsesoftware
                                              Keith, This depends upon your Limit switch configuration. Many of us just feed the Limit switch to a given Port/Pin number and let the software shut down
                                              Message 22 of 22 , Oct 6, 2008
                                              • 0 Attachment
                                                Keith,

                                                This depends upon your Limit switch configuration. Many of us just
                                                feed the Limit switch to a given Port/Pin number and let the
                                                software shut down everything. In that case, the software will have
                                                an over-ride condition that allows you to jog off of the Limit
                                                switch. The danger in this is that if the software itself goes
                                                wacko, it may not recognize the limit switch in the first place and
                                                just keep driving your tool into who-knows-what.

                                                Others use an "intelligent" independent circuit to respond to the
                                                Limit switches. These usually shut off power to the controller and
                                                usually the spindle also, independent of the software. They usually
                                                also pass the Limit switch activation signal through to the software
                                                also so that the software knows what has happened.

                                                These independent circuits will have some sort of "reset" switch to
                                                return power to everything, allowing you to jog off of the switch
                                                and correct any errors.

                                                If you do some searching on the Internet using terms like "limit
                                                switch" or "cnc limit switch" you will most likely come up with
                                                numerous links to this subject. You will see wiring examples,
                                                commercially made limit switch "controllers" and DIY controllers.

                                                Regards,
                                                Gary

                                                --- In taigtools@yahoogroups.com, Keith Bucklitch
                                                <keith.bucklitch@...> wrote:
                                                >
                                                > Thanks Guys for the informative comments recently posted. I need
                                                to
                                                > sit down and read through them to determine the best way to
                                                proceed
                                                > from here.
                                                >
                                                > Just one point I am still unclear about. No one has answered my
                                                > query as to how one starts up the system once it has been brought
                                                to
                                                > a halt by the activation of a limit switch. Does one simply issue
                                                a
                                                > MDI command to move away from the limit position? Obviously the
                                                > software is still working, but is power still on tap to the
                                                > motors? Perhaps I have got the wrong end of the stick here. I
                                                had
                                                > in mind that when a limit switch was activated, it stopped
                                                EVERYTHING
                                                > on the machine - spindle, steppers, coolant etc. Does it simply
                                                stop
                                                > the stepper motors from moving any further in a particular
                                                direction?
                                                >
                                                > Keith
                                                >
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