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Re: Connectors for Keling stepper driver - Threading

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  • bruce_e_layne
    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
    Message 1 of 21 , Jul 22 3:00 PM
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      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
    • Douglas Vogt
      Good information here for those that are considering adding a stepper to the spindle for threading. Would it be possible for you to insert a bit of text in
      Message 2 of 21 , Jul 22 3:25 PM
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        Good information here for those that are considering adding a stepper to the spindle for threading. Would it be possible for you to insert a bit of text in your comments on setting up Mach to do this? There are several YouTube videos on running a spindle via stepper but not too much detail. Specifically, what has to be entered in the Ports & Pins for the spindle and what for the A axis?




        ________________________________
        From: "dtbarber@..." <dtbarber@...>
        To: SherlineCNC@yahoogroups.com
        Sent: Monday, July 22, 2013 5:17 PM
        Subject: [SherlineCNC] Re: Connectors for Keling stepper driver - Threading



         
        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
        >




        [Non-text portions of this message have been removed]
      • jowhowho
        I ve been using the standard Sherline lathe stepper spindle kit with LinuxCNC for single point threading. I program it like it is a fast rotary table. Since
        Message 3 of 21 , Jul 22 3:41 PM
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          I've been using the standard Sherline lathe stepper spindle kit with LinuxCNC for single point threading. I program it like it is a fast rotary table. Since there is no feedback, if the spindle stepper motor stalls, the Z axis keeps going and can trash things. In free cutting brass and steel, I've been able to cut 3" 16tpi thread (with many passes). One of the things I like about this approach is that you can exactly control the lead-ins and lead-outs. I've also done some very nice knurling. I've gotten a bigger stepper motor than the standard little Sherline I've been using, but I haven't cut with it yet. There is also a three to one timing belt kit to replace the standard two to one kit.

          -- Justin
        • danieltbarber
          Comments have been added to the photos. Regards, Dan
          Message 4 of 21 , Jul 23 1:53 PM
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            Comments have been added to the photos.

            Regards,

            Dan

            --- In SherlineCNC@yahoogroups.com, Douglas Vogt <dbvogt@...> wrote:
            >
            > Good information here for those that are considering adding a stepper to the spindle for threading. Would it be possible for you to insert a bit of text in your comments on setting up Mach to do this? There are several YouTube videos on running a spindle via stepper but not too much detail. Specifically, what has to be entered in the Ports & Pins for the spindle and what for the A axis?
            >
            >
            >
          • danieltbarber
            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
            Message 5 of 21 , Jul 23 2:15 PM
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              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
              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 6 of 21 , Jul 23 2:32 PM
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                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 7 of 21 , Jul 24 6:51 AM
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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 8 of 21 , Jul 24 7:03 AM
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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 9 of 21 , Jul 24 9:17 AM
                    • 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 10 of 21 , Jul 24 9:41 AM
                      • 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 11 of 21 , Jul 24 11:36 AM
                        • 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 12 of 21 , Jul 24 1:04 PM
                          • 0 Attachment
                            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 13 of 21 , Aug 24, 2013
                            • 0 Attachment
                              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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