Loading ...
Sorry, an error occurred while loading the content.

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

Expand Messages
  • 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 1 of 21 , Jul 22 3:25 PM
    • 0 Attachment
      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 2 of 21 , Jul 22 3:41 PM
      • 0 Attachment
        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 3 of 21 , Jul 23 1:53 PM
        • 0 Attachment
          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 4 of 21 , Jul 23 2:15 PM
          • 0 Attachment
            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 5 of 21 , Jul 23 2:32 PM
            • 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 6 of 21 , Jul 24 6:51 AM
              • 0 Attachment
                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 7 of 21 , Jul 24 7:03 AM
                • 0 Attachment
                  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 8 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 9 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 10 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 11 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 12 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
                            > >
                            >
                          Your message has been successfully submitted and would be delivered to recipients shortly.