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Mach3 Lathe Thread pitch issue

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  • tooci_toucan
    Hello Group, I ve been having a lot of trouble threading with my new CNC lathe. I ve searched high and low for a solution on this group, machsupport forum,
    Message 1 of 6 , Sep 17, 2013
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      Hello Group,
      I've been having a lot of trouble threading with my new CNC lathe. I've searched high and low for a solution on this group, machsupport forum, and just google searches with no results. The problem is in the pitch. If I call out .05"/rev pitch in the G73 the planner slows the feed down to .034 or such even though the RPM is pretty stable at 500 RPM. So I screwed around with the settings, active high index, active low index, spindle motor calibration, and debounce. I was thinking that the timing was messed up, and that somewhere the signal was getting coming on and off too fast for me to see. I ran across the diagnostic(which I know doesn't work) and tried it to see what might be going on. Nothing changes in the threading cycle when I disable the plugin and restart mach. So I used the simple thread wizard to make a simple 20tpi test and ran the plugin just to see. So the rotation speed realtime is like 50000000..., it's too big for the DRO to show all the digits. The application end rpm shows ~503 and the locked RPM is ~753, which would account for the change in units per rev. All wires are shielded and grounded and even if I preset the frequency on the drive for 500rpm I still get this problem. Anybody ever deal with this? Any help would be immensely appreciated. Thanks in advance.
      Jake
    • danmauch
      In Config, General settings what value is in your Index box? Debounce is used for the home limit switch inputs. Dan Mauch camtronics-cnc.com --- In
      Message 2 of 6 , Sep 18, 2013
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         In Config, General settings what value is in your Index box? Debounce is used for the home limit switch inputs.

        Dan Mauch

        camtronics-cnc.com



        --- In mach1mach2cnc@yahoogroups.com, <mach1mach2cnc@yahoogroups.com> wrote:

        Hello Group,
        I've been having a lot of trouble threading with my new CNC lathe. I've searched high and low for a solution on this group, machsupport forum, and just google searches with no results. The problem is in the pitch. If I call out .05"/rev pitch in the G73 the planner slows the feed down to .034 or such even though the RPM is pretty stable at 500 RPM. So I screwed around with the settings, active high index, active low index, spindle motor calibration, and debounce. I was thinking that the timing was messed up, and that somewhere the signal was getting coming on and off too fast for me to see. I ran across the diagnostic(which I know doesn't work) and tried it to see what might be going on. Nothing changes in the threading cycle when I disable the plugin and restart mach. So I used the simple thread wizard to make a simple 20tpi test and ran the plugin just to see. So the rotation speed realtime is like 50000000..., it's too big for the DRO to show all the digits. The application end rpm shows ~503 and the locked RPM is ~753, which would account for the change in units per rev. All wires are shielded and grounded and even if I preset the frequency on the drive for 500rpm I still get this problem. Anybody ever deal with this? Any help would be immensely appreciated. Thanks in advance.
        Jake
      • tooci_toucan
        The index is set to 10 at the moment, though I ve played around with it from 0-100 with no change. I guess I should include that I m using the latest version
        Message 3 of 6 , Sep 18, 2013
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          The index is set to 10 at the moment, though I've played around with it from 0-100 with no change. I guess I should include that I'm using the latest version of Mach3, a CNC4PC C11g main board, 203V gecko drives and an optimized computer to run mach. The motor is a 3hp driven by a Lenze ACtech. I tried to run a USB SmoothStepper, but it created more problems than it solved. The motion of the axis was much smoother though.
        • tooci_toucan
          Debounce index is currently set to 10. I ve played around with it from 0-100 with no change in the thread. I should mention that I m using the latest
          Message 4 of 6 , Sep 19, 2013
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            Debounce index is currently set to 10. I've played around with it from 0-100 with no change in the thread. I should mention that I'm using the latest lockdown of mach3, CNC4PC spindle index board, C11G main board, Gecko 203V drives, and an XP computer that's optimized for mach. I tried using a USB smoothstepper but it caused more problems than it was worth, and wouldn't recognize the spindle speed at all. The motion of the axis were smoother though.
            I measured the spindle speed with a hand held tach and it reads 100rpm higher in mach from 100-800rpm then it steadily increases to 200-300RMP over from 800-2700. It's almost like the spindle index is being scaled or something weird.
          • campgems
            I ve seen, but not used a program that turns your PC into an O scope. IT was a free program if I remember correct and was referenced on this group. It would be
            Message 5 of 6 , Sep 20, 2013
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              I've seen, but not used a program that turns your PC into an O scope.  IT was a free program if I remember  correct and was referenced on this group.  It would be interesting to see what the signal off your index looked like.  Also what noise is on that line. 


              A problem I had with my Taig home conversion was random steps on the Z axis with higherr spindle speeds.  I fought the noise issue and could not really isolate a cause.  It was pointed out on this group that older PC's had Parallel Ports with 5V signals while most of the P4 and later mother boards had signals in the 3/5V range.  I dug out an old Win 2000 vintage PC and found it was in fact a 5V signal.  That cured the signal to noise issue.  My stepper Controllers, Parker OEM 650's require a minimum signal of 3.5V.  Any noise, and there is always going to be some was causing false step pulses.  The higher signal to noise ratio with the 5V signal solved it. 


              Last, on your shielded and grounded cables.  Make sure that they are grounded only on the PC end.  Look at your grounding like a tree.  The roots as the ground and and each branch, Ie your index, limits, motors, and machine frame should have only one path to ground, that being at the wall outlet.  Ground loops will drive you batty trying to solve the problems. 


              Don



              --- In mach1mach2cnc@yahoogroups.com, <jakemestre@...> wrote:

              Debounce index is currently set to 10. I've played around with it from 0-100 with no change in the thread. I should mention that I'm using the latest lockdown of mach3, CNC4PC spindle index board, C11G main board, Gecko 203V drives, and an XP computer that's optimized for mach. I tried using a USB smoothstepper but it caused more problems than it was worth, and wouldn't recognize the spindle speed at all. The motion of the axis were smoother though.
              I measured the spindle speed with a hand held tach and it reads 100rpm higher in mach from 100-800rpm then it steadily increases to 200-300RMP over from 800-2700. It's almost like the spindle index is being scaled or something weird.
            • tooci_toucan
              So this problem turned out to be a combination of several weird things. I started off with the sensor. It s a photogate C3 board from CNC4PC. There was
              Message 6 of 6 , Sep 30, 2013
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                So this problem turned out to be a combination of several weird things. I started off with the sensor. It's a photogate C3 board from CNC4PC. There was almost no noise in the index, it's shielded and grounded on one end and produced a very clean signal. I'm building another lathe at the moment so I have all the spare (new boards). The old boards have been through a few rebuilds and I thought with all the wiring, jostling, and powerchecks something might have been fried. I replaced all the chips on the C11G with no change, then I replaced the C11G all together. I tried a different sensor, different C3 index board and pretty much everything I could think of mechanically to fix the problem. After all that the DRO was still displaying 600RPM when I was physically measuring 500.
                So then I moved onto the programming to troubleshoot. I tried reinstalling mach. I saved the XML but dumped everything hoping there was maybe a bug in the install. Nope. Then it occurred to me to try a completely new profile. I copied all the pins, and motor tuning to a new profile and instantly the spindle speed was working correctly.
                The problem was in two things. First the pulleys and secondly the motor tuning steps/rev and velocity settings. I forgot to set the pulley ratio, so the default 1 sent the DRO directly to 500RPM.
                I'm using the PID spindle control, so I think I need to still play around with the steps/rev and speed settings to get it to thread perfectly without PID.
                This was such a weird problem to troubleshoot. Any ideas why the pulleys would mess with the DRO? I thought the index was supposed to be measuring the spindle not the motor. Thanks
                Jake
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