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RE: [SherlineCNC] Re: Connectors for Keling stepper driver - Threading

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  • Andy Wander
    Hi Dan: What you are doing sounds like it will work well, but it is NOT an Index Pulse. An Index Pulse occurs only once per revolution of the encoder or pulse
    Message 1 of 21 , Jul 23, 2013
    • 0 Attachment
      Hi Dan:



      What you are doing sounds like it will work well, but it is NOT an Index
      Pulse.



      An Index Pulse occurs only once per revolution of the encoder or pulse
      generator, and is often used in combination with a multiple-pulse-per-rev
      encoder to achieve better homing accuracy.



      Andy Wander

      _____

      From: SherlineCNC@yahoogroups.com [mailto:SherlineCNC@yahoogroups.com] On
      Behalf Of dtbarber@...
      Sent: Tuesday, July 23, 2013 5:16 PM
      To: SherlineCNC@yahoogroups.com
      Subject: [SherlineCNC] Re: Connectors for Keling stepper driver - Threading





      Bruce,

      The last I read, MACH3 will use up to 4 index pulses per revolution, but the
      author of the software saw very little increase in accuracy when using more
      than 1 pulse per revolution. I think that he is correct, when the spindle is
      driven by a motor with enough torque to keep speeds consistent.

      Like many people I use an optical sensor to generate the index pulse. In my
      case, I use a 20-slot encoder wheel, mounted to the spindle pulley. Using a
      "U" shaped optical sensor a pulse is generated each time a slot passes the
      sensor. Sensor output feeds into a PIC micro-controller, which is switch
      selectable to serve as either a tach, or to output a single square wave as
      an index pulse. The PIC calculates RPM based on the number of pulses
      occurring within a set period of time. The 20 slots makes the calculations
      using integer math fairly straight forward. When used as an index pulse
      generator, the PIC simply outputs a high or a low for 10 pulse counts.

      Regards,

      Dan

      --- In SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com> ,
      "bruce_e_layne" <yahoogroups@...> wrote:
      >
      > Neat project! Thanks for sharing.
      >
      > The last I heard, Mach uses one index pulse per spindle revolution, and as
      you mentioned, that's not really enough when the spindle is under load and
      the RPM varies. LinuxCNC uses a spindle encoder with one index pulse to
      initiate the threading operation and many pulses per revolution for much
      better control of spindle speed by frequently updating the current to the
      spindle motor to maintain a uniform angular velocity.
      >
      > Or, you could use a large stepper motor for the spindle as long as Mach 3
      can be configured to use a stepper for the spindle motor when threading, and
      you don't load it so much that you lose any steps.
      >
      > I'm using LinuxCNC for my mini-lathe project. If I decide to use it for
      threading, I'll add a spindle encoder and see if I can get LinuxCNC to
      control the Sherline DC spindle motor.
      >
      >
      >
      > --- In SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com>
      , dtbarber@ wrote:
      > >
      > > Davide,
      > >
      > > I have created a photo album showing my approach for driving the spindle
      head with a stepper motor. Once approved by the moderator, I will add
      comments and more explanation.
      > >
      > > Regarding your question about how I am threading on the lathe, I use
      MACH3 and a single 60 degree lathe bit for CNC threading. There is a lot of
      information available about CNC threading with MACH3, but fundamentally,
      MACH3 uses a spindle index pulse to determine rotary speed and position of
      the material being threaded and advances the Z-axis the appropriate feed
      rate to generate the thread. The ability to track spindle speed and position
      allows threads to be cut in multiple passes, reducing tool loading.
      > >
      > > The process is simple but torque limitations of the standard Sherline
      motor results in inconsistent spindle speeds during the threading process.
      You probably have noticed that spindle speed can change during normal lathe
      turning processes. MACH3 adjusts to the changes in speed due to tool
      loading, but when speed changes are pronounced, adjustments in Z-axis speed
      can result in an inconsistent thread. I have made various modifications to
      my Sherline lathe to improve threading, including replacing the standard
      20-TPI leadscrew with a 5-TPI leadscrew, which allows threading a higher
      than normal spindle speeds. However, I think driving the spindle head with a
      proper sized stepper motor is all that one really needs to do. With my
      current system, I remove 0.005" per pass in free machining steel and even
      when cutting 20-TPI threads in .5" material, spindle speed remains constant
      through out the threading process.
      > >
      > > More when the pictures are posted.
      > >
      > > Regards,
      > >
      > > Dan
      >





      [Non-text portions of this message have been removed]
    • danieltbarber
      Andy, Thanks for your comments. Apparently, I was not clear in my explanation regarding my approach. The 20-pulse per revolution output from the optical
      Message 2 of 21 , Jul 24, 2013
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        Andy,

        Thanks for your comments. Apparently, I was not clear in my explanation regarding my approach. The 20-pulse per revolution output from the optical sensor feeds into a PIC micro-controller which is user selectable to either function as a tach or as an index pulse generator. When functioning as a tach, the PIC counts the number of pulses that occur within a set period of time, calculates RPM, and then outputs the RPM to a four-digit, seven-segment LED display. When functioning as an index pulse generator, for each revolution, the PIC outputs a +5V signal when it first detects a pulse and holds that signal for a count of 10 pulses. It then pulls the pin low for the next 10 pulses. This single pulse per revolution square wave output feeds into MACH3 for determining spindle speed and location for threading. I have been using this system for at least 5 years and works perfectly.

        Regards,

        Dan





        --- In SherlineCNC@yahoogroups.com, "Andy Wander" <andywander@...> wrote:
        >
        > Hi Dan:
        >
        >
        >
        > What you are doing sounds like it will work well, but it is NOT an Index
        > Pulse.
        >
        >
        >
        > An Index Pulse occurs only once per revolution of the encoder or pulse
        > generator, and is often used in combination with a multiple-pulse-per-rev
        > encoder to achieve better homing accuracy.
        >
        >
        >
        > Andy Wander
        >
        > _____
        >
        > From: SherlineCNC@yahoogroups.com [mailto:SherlineCNC@yahoogroups.com] On
        > Behalf Of dtbarber@...
        > Sent: Tuesday, July 23, 2013 5:16 PM
        > To: SherlineCNC@yahoogroups.com
        > Subject: [SherlineCNC] Re: Connectors for Keling stepper driver - Threading
        >
        >
        >
        >
        >
        > Bruce,
        >
        > The last I read, MACH3 will use up to 4 index pulses per revolution, but the
        > author of the software saw very little increase in accuracy when using more
        > than 1 pulse per revolution. I think that he is correct, when the spindle is
        > driven by a motor with enough torque to keep speeds consistent.
        >
        > Like many people I use an optical sensor to generate the index pulse. In my
        > case, I use a 20-slot encoder wheel, mounted to the spindle pulley. Using a
        > "U" shaped optical sensor a pulse is generated each time a slot passes the
        > sensor. Sensor output feeds into a PIC micro-controller, which is switch
        > selectable to serve as either a tach, or to output a single square wave as
        > an index pulse. The PIC calculates RPM based on the number of pulses
        > occurring within a set period of time. The 20 slots makes the calculations
        > using integer math fairly straight forward. When used as an index pulse
        > generator, the PIC simply outputs a high or a low for 10 pulse counts.
        >
        > Regards,
        >
        > Dan
        >
        > --- In SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com> ,
        > "bruce_e_layne" <yahoogroups@> wrote:
        > >
        > > Neat project! Thanks for sharing.
        > >
        > > The last I heard, Mach uses one index pulse per spindle revolution, and as
        > you mentioned, that's not really enough when the spindle is under load and
        > the RPM varies. LinuxCNC uses a spindle encoder with one index pulse to
        > initiate the threading operation and many pulses per revolution for much
        > better control of spindle speed by frequently updating the current to the
        > spindle motor to maintain a uniform angular velocity.
        > >
        > > Or, you could use a large stepper motor for the spindle as long as Mach 3
        > can be configured to use a stepper for the spindle motor when threading, and
        > you don't load it so much that you lose any steps.
        > >
        > > I'm using LinuxCNC for my mini-lathe project. If I decide to use it for
        > threading, I'll add a spindle encoder and see if I can get LinuxCNC to
        > control the Sherline DC spindle motor.
        > >
        > >
        > >
        > > --- In SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com>
        > , dtbarber@ wrote:
        > > >
        > > > Davide,
        > > >
        > > > I have created a photo album showing my approach for driving the spindle
        > head with a stepper motor. Once approved by the moderator, I will add
        > comments and more explanation.
        > > >
        > > > Regarding your question about how I am threading on the lathe, I use
        > MACH3 and a single 60 degree lathe bit for CNC threading. There is a lot of
        > information available about CNC threading with MACH3, but fundamentally,
        > MACH3 uses a spindle index pulse to determine rotary speed and position of
        > the material being threaded and advances the Z-axis the appropriate feed
        > rate to generate the thread. The ability to track spindle speed and position
        > allows threads to be cut in multiple passes, reducing tool loading.
        > > >
        > > > The process is simple but torque limitations of the standard Sherline
        > motor results in inconsistent spindle speeds during the threading process.
        > You probably have noticed that spindle speed can change during normal lathe
        > turning processes. MACH3 adjusts to the changes in speed due to tool
        > loading, but when speed changes are pronounced, adjustments in Z-axis speed
        > can result in an inconsistent thread. I have made various modifications to
        > my Sherline lathe to improve threading, including replacing the standard
        > 20-TPI leadscrew with a 5-TPI leadscrew, which allows threading a higher
        > than normal spindle speeds. However, I think driving the spindle head with a
        > proper sized stepper motor is all that one really needs to do. With my
        > current system, I remove 0.005" per pass in free machining steel and even
        > when cutting 20-TPI threads in .5" material, spindle speed remains constant
        > through out the threading process.
        > > >
        > > > More when the pictures are posted.
        > > >
        > > > Regards,
        > > >
        > > > Dan
        > >
        >
        >
        >
        >
        >
        > [Non-text portions of this message have been removed]
        >
      • Andy Wander
        Ah, yes that makes it an Index pulse. I don t believe Mach cares about the relative lengths of the ON and FF portions of the pulse, though. thanks, Andy Wander
        Message 3 of 21 , Jul 24, 2013
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          Ah, yes that makes it an Index pulse.



          I don't believe Mach cares about the relative lengths of the ON and FF
          portions of the pulse, though.



          thanks,



          Andy Wander

          _____

          From: SherlineCNC@yahoogroups.com [mailto:SherlineCNC@yahoogroups.com] On
          Behalf Of danieltbarber
          Sent: Wednesday, July 24, 2013 9:51 AM
          To: SherlineCNC@yahoogroups.com
          Subject: [SherlineCNC] Re: Connectors for Keling stepper driver - Threading





          Andy,

          Thanks for your comments. Apparently, I was not clear in my explanation
          regarding my approach. The 20-pulse per revolution output from the optical
          sensor feeds into a PIC micro-controller which is user selectable to either
          function as a tach or as an index pulse generator. When functioning as a
          tach, the PIC counts the number of pulses that occur within a set period of
          time, calculates RPM, and then outputs the RPM to a four-digit,
          seven-segment LED display. When functioning as an index pulse generator, for
          each revolution, the PIC outputs a +5V signal when it first detects a pulse
          and holds that signal for a count of 10 pulses. It then pulls the pin low
          for the next 10 pulses. This single pulse per revolution square wave output
          feeds into MACH3 for determining spindle speed and location for threading. I
          have been using this system for at least 5 years and works perfectly.

          Regards,

          Dan

          --- In SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com> ,
          "Andy Wander" <andywander@...> wrote:
          >
          > Hi Dan:
          >
          >
          >
          > What you are doing sounds like it will work well, but it is NOT an Index
          > Pulse.
          >
          >
          >
          > An Index Pulse occurs only once per revolution of the encoder or pulse
          > generator, and is often used in combination with a multiple-pulse-per-rev
          > encoder to achieve better homing accuracy.
          >
          >
          >
          > Andy Wander
          >
          > _____
          >
          > From: SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com>
          [mailto:SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com> ]
          On
          > Behalf Of dtbarber@...
          > Sent: Tuesday, July 23, 2013 5:16 PM
          > To: SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com>
          > Subject: [SherlineCNC] Re: Connectors for Keling stepper driver -
          Threading
          >
          >
          >
          >
          >
          > Bruce,
          >
          > The last I read, MACH3 will use up to 4 index pulses per revolution, but
          the
          > author of the software saw very little increase in accuracy when using
          more
          > than 1 pulse per revolution. I think that he is correct, when the spindle
          is
          > driven by a motor with enough torque to keep speeds consistent.
          >
          > Like many people I use an optical sensor to generate the index pulse. In
          my
          > case, I use a 20-slot encoder wheel, mounted to the spindle pulley. Using
          a
          > "U" shaped optical sensor a pulse is generated each time a slot passes the
          > sensor. Sensor output feeds into a PIC micro-controller, which is switch
          > selectable to serve as either a tach, or to output a single square wave as
          > an index pulse. The PIC calculates RPM based on the number of pulses
          > occurring within a set period of time. The 20 slots makes the calculations
          > using integer math fairly straight forward. When used as an index pulse
          > generator, the PIC simply outputs a high or a low for 10 pulse counts.
          >
          > Regards,
          >
          > Dan
          >
          > --- In SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com>
          <mailto:SherlineCNC%40yahoogroups.com> ,
          > "bruce_e_layne" <yahoogroups@> wrote:
          > >
          > > Neat project! Thanks for sharing.
          > >
          > > The last I heard, Mach uses one index pulse per spindle revolution, and
          as
          > you mentioned, that's not really enough when the spindle is under load and
          > the RPM varies. LinuxCNC uses a spindle encoder with one index pulse to
          > initiate the threading operation and many pulses per revolution for much
          > better control of spindle speed by frequently updating the current to the
          > spindle motor to maintain a uniform angular velocity.
          > >
          > > Or, you could use a large stepper motor for the spindle as long as Mach
          3
          > can be configured to use a stepper for the spindle motor when threading,
          and
          > you don't load it so much that you lose any steps.
          > >
          > > I'm using LinuxCNC for my mini-lathe project. If I decide to use it for
          > threading, I'll add a spindle encoder and see if I can get LinuxCNC to
          > control the Sherline DC spindle motor.
          > >
          > >
          > >
          > > --- In SherlineCNC@yahoogroups.com
          <mailto:SherlineCNC%40yahoogroups.com>
          <mailto:SherlineCNC%40yahoogroups.com>
          > , dtbarber@ wrote:
          > > >
          > > > Davide,
          > > >
          > > > I have created a photo album showing my approach for driving the
          spindle
          > head with a stepper motor. Once approved by the moderator, I will add
          > comments and more explanation.
          > > >
          > > > Regarding your question about how I am threading on the lathe, I use
          > MACH3 and a single 60 degree lathe bit for CNC threading. There is a lot
          of
          > information available about CNC threading with MACH3, but fundamentally,
          > MACH3 uses a spindle index pulse to determine rotary speed and position of
          > the material being threaded and advances the Z-axis the appropriate feed
          > rate to generate the thread. The ability to track spindle speed and
          position
          > allows threads to be cut in multiple passes, reducing tool loading.
          > > >
          > > > The process is simple but torque limitations of the standard Sherline
          > motor results in inconsistent spindle speeds during the threading process.
          > You probably have noticed that spindle speed can change during normal
          lathe
          > turning processes. MACH3 adjusts to the changes in speed due to tool
          > loading, but when speed changes are pronounced, adjustments in Z-axis
          speed
          > can result in an inconsistent thread. I have made various modifications to
          > my Sherline lathe to improve threading, including replacing the standard
          > 20-TPI leadscrew with a 5-TPI leadscrew, which allows threading a higher
          > than normal spindle speeds. However, I think driving the spindle head with
          a
          > proper sized stepper motor is all that one really needs to do. With my
          > current system, I remove 0.005" per pass in free machining steel and even
          > when cutting 20-TPI threads in .5" material, spindle speed remains
          constant
          > through out the threading process.
          > > >
          > > > More when the pictures are posted.
          > > >
          > > > Regards,
          > > >
          > > > Dan
          > >
          >
          >
          >
          >
          >
          > [Non-text portions of this message have been removed]
          >





          [Non-text portions of this message have been removed]
        • Sullivan, John
          Dan, What you described sounds rather similar to how Sherline s DRO works. It has long left me curious as to how it knows which direction the toothed wheel is
          Message 4 of 21 , Jul 24, 2013
          • 0 Attachment
            Dan,

            What you described sounds rather similar to how Sherline's DRO works.
            It has long left me curious as to how it knows which direction the toothed wheel is going?

            Would any of you be able to explain this small mystery to me?

            Thank you,

            John G. Sullivan
            Austin, Texas
            512-340-6078

            ________________________________________________________________________
            1b. Re: Connectors for Keling stepper driver - Threading
            Posted by: dtbarber@... danieltbarber
            Date: Tue Jul 23, 2013 2:15 pm ((PDT))

            Bruce,

            The last I read, MACH3 will use up to 4 index pulses per revolution, but the author of the software saw very little increase in accuracy when using more than 1 pulse per revolution. I think that he is correct, when the spindle is driven by a motor with enough torque to keep speeds consistent.

            Like many people I use an optical sensor to generate the index pulse. In my case, I use a 20-slot encoder wheel, mounted to the spindle pulley. Using a "U" shaped optical sensor a pulse is generated each time a slot passes the sensor. Sensor output feeds into a PIC micro-controller, which is switch selectable to serve as either a tach, or to output a single square wave as an index pulse. The PIC calculates RPM based on the number of pulses occurring within a set period of time. The 20 slots makes the calculations using integer math fairly straight forward. When used as an index pulse generator, the PIC simply outputs a high or a low for 10 pulse counts.

            Regards,

            Dan

            --- In SherlineCNC@yahoogroups.com, "bruce_e_layne" <yahoogroups@...> wrote:
            >
            > Neat project! Thanks for sharing.
            >
            > The last I heard, Mach uses one index pulse per spindle revolution, and as you mentioned, that's not really enough when the spindle is under load and the RPM varies. LinuxCNC uses a spindle encoder with one index pulse to initiate the threading operation and many pulses per revolution for much better control of spindle speed by frequently updating the current to the spindle motor to maintain a uniform angular velocity.
            >
            > Or, you could use a large stepper motor for the spindle as long as Mach 3 can be configured to use a stepper for the spindle motor when threading, and you don't load it so much that you lose any steps.
            >
            > I'm using LinuxCNC for my mini-lathe project. If I decide to use it for threading, I'll add a spindle encoder and see if I can get LinuxCNC to control the Sherline DC spindle motor.
            >
            >
            >
            > --- In SherlineCNC@yahoogroups.com, dtbarber@ wrote:
            > >
            > > Davide,
            > >
            > > I have created a photo album showing my approach for driving the spindle head with a stepper motor. Once approved by the moderator, I will add comments and more explanation.
            > >
            > > Regarding your question about how I am threading on the lathe, I use MACH3 and a single 60 degree lathe bit for CNC threading. There is a lot of information available about CNC threading with MACH3, but fundamentally, MACH3 uses a spindle index pulse to determine rotary speed and position of the material being threaded and advances the Z-axis the appropriate feed rate to generate the thread. The ability to track spindle speed and position allows threads to be cut in multiple passes, reducing tool loading.
            > >
            > > The process is simple but torque limitations of the standard Sherline motor results in inconsistent spindle speeds during the threading process. You probably have noticed that spindle speed can change during normal lathe turning processes. MACH3 adjusts to the changes in speed due to tool loading, but when speed changes are pronounced, adjustments in Z-axis speed can result in an inconsistent thread. I have made various modifications to my Sherline lathe to improve threading, including replacing the standard 20-TPI leadscrew with a 5-TPI leadscrew, which allows threading a higher than normal spindle speeds. However, I think driving the spindle head with a proper sized stepper motor is all that one really needs to do. With my current system, I remove 0.005" per pass in free machining steel and even when cutting 20-TPI threads in .5" material, spindle speed remains constant through out the threading process.
            > >
            > > More when the pictures are posted.
            > >
            > > Regards,
            > >
            > > Dan
          • Andy Wander
            John: Most directional devices of this sort use what is called a Quadrature Encoder. Look it up and you will see how the use of 2 sensors can indicate
            Message 5 of 21 , Jul 24, 2013
            • 0 Attachment
              John:



              Most directional devices of this sort use what is called a Quadrature
              Encoder. Look it up and you will see how the use of 2 sensors can indicate
              direction.



              Andy Wander

              _____

              From: SherlineCNC@yahoogroups.com [mailto:SherlineCNC@yahoogroups.com] On
              Behalf Of Sullivan, John
              Sent: Wednesday, July 24, 2013 12:18 PM
              To: SherlineCNC@yahoogroups.com
              Subject: [SherlineCNC] Re: Connectors for Keling stepper driver - Threading





              Dan,

              What you described sounds rather similar to how Sherline's DRO works.
              It has long left me curious as to how it knows which direction the toothed
              wheel is going?

              Would any of you be able to explain this small mystery to me?

              Thank you,

              John G. Sullivan
              Austin, Texas
              512-340-6078

              __________________________________________________________
              1b. Re: Connectors for Keling stepper driver - Threading
              Posted by: dtbarber@... <mailto:dtbarber%40sti.net> danieltbarber
              Date: Tue Jul 23, 2013 2:15 pm ((PDT))

              Bruce,

              The last I read, MACH3 will use up to 4 index pulses per revolution, but the
              author of the software saw very little increase in accuracy when using more
              than 1 pulse per revolution. I think that he is correct, when the spindle is
              driven by a motor with enough torque to keep speeds consistent.

              Like many people I use an optical sensor to generate the index pulse. In my
              case, I use a 20-slot encoder wheel, mounted to the spindle pulley. Using a
              "U" shaped optical sensor a pulse is generated each time a slot passes the
              sensor. Sensor output feeds into a PIC micro-controller, which is switch
              selectable to serve as either a tach, or to output a single square wave as
              an index pulse. The PIC calculates RPM based on the number of pulses
              occurring within a set period of time. The 20 slots makes the calculations
              using integer math fairly straight forward. When used as an index pulse
              generator, the PIC simply outputs a high or a low for 10 pulse counts.

              Regards,

              Dan

              --- In SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com> ,
              "bruce_e_layne" <yahoogroups@...> wrote:
              >
              > Neat project! Thanks for sharing.
              >
              > The last I heard, Mach uses one index pulse per spindle revolution, and as
              you mentioned, that's not really enough when the spindle is under load and
              the RPM varies. LinuxCNC uses a spindle encoder with one index pulse to
              initiate the threading operation and many pulses per revolution for much
              better control of spindle speed by frequently updating the current to the
              spindle motor to maintain a uniform angular velocity.
              >
              > Or, you could use a large stepper motor for the spindle as long as Mach 3
              can be configured to use a stepper for the spindle motor when threading, and
              you don't load it so much that you lose any steps.
              >
              > I'm using LinuxCNC for my mini-lathe project. If I decide to use it for
              threading, I'll add a spindle encoder and see if I can get LinuxCNC to
              control the Sherline DC spindle motor.
              >
              >
              >
              > --- In SherlineCNC@yahoogroups.com <mailto:SherlineCNC%40yahoogroups.com>
              , dtbarber@ wrote:
              > >
              > > Davide,
              > >
              > > I have created a photo album showing my approach for driving the spindle
              head with a stepper motor. Once approved by the moderator, I will add
              comments and more explanation.
              > >
              > > Regarding your question about how I am threading on the lathe, I use
              MACH3 and a single 60 degree lathe bit for CNC threading. There is a lot of
              information available about CNC threading with MACH3, but fundamentally,
              MACH3 uses a spindle index pulse to determine rotary speed and position of
              the material being threaded and advances the Z-axis the appropriate feed
              rate to generate the thread. The ability to track spindle speed and position
              allows threads to be cut in multiple passes, reducing tool loading.
              > >
              > > The process is simple but torque limitations of the standard Sherline
              motor results in inconsistent spindle speeds during the threading process.
              You probably have noticed that spindle speed can change during normal lathe
              turning processes. MACH3 adjusts to the changes in speed due to tool
              loading, but when speed changes are pronounced, adjustments in Z-axis speed
              can result in an inconsistent thread. I have made various modifications to
              my Sherline lathe to improve threading, including replacing the standard
              20-TPI leadscrew with a 5-TPI leadscrew, which allows threading a higher
              than normal spindle speeds. However, I think driving the spindle head with a
              proper sized stepper motor is all that one really needs to do. With my
              current system, I remove 0.005" per pass in free machining steel and even
              when cutting 20-TPI threads in .5" material, spindle speed remains constant
              through out the threading process.
              > >
              > > More when the pictures are posted.
              > >
              > > Regards,
              > >
              > > Dan





              [Non-text portions of this message have been removed]
            • KM6VV
              Sounds like a nice system Dan. Did you buy/build it? Alan KM6VV ... The 20-pulse per revolution output from the optical sensor feeds into a PIC
              Message 6 of 21 , Jul 24, 2013
              • 0 Attachment
                Sounds like a nice system Dan. Did you buy/build it?

                Alan KM6VV

                On 7/24/2013 6:51 AM, danieltbarber wrote:
                > Andy,
                >
                > Thanks for your comments. Apparently, I was not clear in my explanation regarding my approach.

                The 20-pulse per revolution output from the optical sensor feeds into a
                PIC micro-controller which is user

                selectable to either function as a tach or as an index pulse generator.
                When functioning as a tach, the

                PIC counts the number of pulses that occur within a set period of time,
                calculates RPM, and then outputs

                the RPM to a four-digit, seven-segment LED display. When functioning as
                an index pulse generator, for

                each revolution, the PIC outputs a +5V signal when it first detects a
                pulse and holds that signal for a

                count of 10 pulses. It then pulls the pin low for the next 10 pulses.
                This single pulse per revolution

                square wave output feeds into MACH3 for determining spindle speed and
                location for threading. I have

                been using this system for at least 5 years and works perfectly.
                >
                > Regards,
                >
                > Dan
                >
              • danieltbarber
                Alan, Thanks, the system is all shop built and the design works well enough that I have stopped working on it. The only unresolved issue is that when mounted
                Message 7 of 21 , Jul 24, 2013
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                  Alan,

                  Thanks, the system is all shop built and the design works well enough that I have stopped working on it. The only unresolved issue is that when mounted in the same enclosure as a Gecko G540 controller and powered by the same power supply, the electrical noise can cause the RPMs to be erratic. Interestingly, I have two controllers, which are for practical purposes the same, however, only one has the problem. This could likely be corrected by adding a few strategic filtering caps, but it was easier to just power the tach from a wall-wart

                  Regards,

                  Dan





                  --- In SherlineCNC@yahoogroups.com, KM6VV <KM6VV@...> wrote:
                  >
                  > Sounds like a nice system Dan. Did you buy/build it?
                  >
                  > Alan KM6VV
                • tuscanland
                  Hi to all, I m done assembling the lathe, the only thing I m missing is the correct preload nut for the crosslide lead screw, it should be coming in next
                  Message 8 of 21 , Aug 24, 2013
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                    Hi to all, I'm done assembling the lathe, the only thing I'm missing is the correct preload nut for the crosslide lead screw, it should be coming in next week. I was able to test the electronics and everything seems to work ok, I posted a photo of what the lathe looks like at this point, but I'm confident that it will be completed by the end of the month, and at that point I'll post a few more.

                    --- In SherlineCNC@yahoogroups.com, dtbarber@... wrote:
                    >
                    > Davide,
                    >
                    > I have created a photo album showing my approach for driving the spindle head with a stepper motor. Once approved by the moderator, I will add comments and more explanation.
                    >
                    > Regarding your question about how I am threading on the lathe, I use MACH3 and a single 60 degree lathe bit for CNC threading. There is a lot of information available about CNC threading with MACH3, but fundamentally, MACH3 uses a spindle index pulse to determine rotary speed and position of the material being threaded and advances the Z-axis the appropriate feed rate to generate the thread. The ability to track spindle speed and position allows threads to be cut in multiple passes, reducing tool loading.
                    >
                    > The process is simple but torque limitations of the standard Sherline motor results in inconsistent spindle speeds during the threading process. You probably have noticed that spindle speed can change during normal lathe turning processes. MACH3 adjusts to the changes in speed due to tool loading, but when speed changes are pronounced, adjustments in Z-axis speed can result in an inconsistent thread. I have made various modifications to my Sherline lathe to improve threading, including replacing the standard 20-TPI leadscrew with a 5-TPI leadscrew, which allows threading a higher than normal spindle speeds. However, I think driving the spindle head with a proper sized stepper motor is all that one really needs to do. With my current system, I remove 0.005" per pass in free machining steel and even when cutting 20-TPI threads in .5" material, spindle speed remains constant through out the threading process.
                    >
                    > More when the pictures are posted.
                    >
                    > Regards,
                    >
                    > Dan
                    >
                    > --- In SherlineCNC@yahoogroups.com, Davide Ghelarducci <tuscanland@> wrote:
                    > >
                    > > Hi Dan,
                    > >  
                    > > nice to hear back from you, I've wired everything correctely so far, just need to wait for the connectors to arrive and I'm all good to go.
                    > > For now I'll go ahead with my plan about modifying the lathe, meaning I'll just use the threading attachment made by Sherline, driving the gears using the nema 34 stepper.
                    > > I was under the impression that the 425 oz/in would have worked as well, but just to be on the safe side I've opted for the more powerful nema 34.
                    > > I'm not sure how you are threading on the lathe, do you use the threading attachment in the same fashion that I plan to do, or do you thread using a mathematical formula combining spindle speed in conjunction with the appropriate feed rate on the z axis?
                    > > I sure would be interested to see your pictures when you have time to upload them.
                    > > Thanks for uploading the dxf files, I'll go look for them now.
                    > > Best regards
                    > > Davide
                    > >
                    >
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