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Re: Info on Taig Lathe carriage gears

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  • lasernerd@hotmail.com
    I agree with Hoyt. Once you ve seen CNC, it s difficult to go back. Depending on the controller you make/buy, you can have manual jog settings and the MDI
    Message 1 of 26 , Feb 1, 2001
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      I agree with Hoyt. Once you've seen CNC, it's difficult to go back.
      Depending on the controller you make/buy, you can have manual jog
      settings and the MDI interface. Some manual jogs are just in certain
      increments, which isn't really that helpful in this case, but some
      you can just use a dial (or computer keys) to jog the cutter as far
      as you want, as fast as you want, just like a manual mill/lathe with
      a digital readout.

      The MDI, or Manual Data Input (I think that's what it stands for)
      lets you type in G-code one line at a time, and execute it instantly.
      This can be very useful, BUT, it can be _VERY_ dangerous. If you miss
      a decimal place, you can have your cutter ram into your headsctock,
      tailstock, or work piece. Or, if you type G00 (rapid feed) instead of
      G01 (linear interpolation, at reg cutting feed), your cutter could
      smash into your piece. Limit switches are a _must_, and virtual ones
      help lots if your software supports them.

      As for the rack idea, I'm not sure that's such a great thing. In CNC,
      you don't really want to have to mess about with backlash crap -
      there are enough other variables to deal with. I've been using a HAAS
      VF-2 at work and it's worth $120,000 CNC, IIRC. It's got ballscrews,
      710 IPM rapid feed, etc. It still tends to cut screwy, or at least
      not in a *linear* fashion. What I mean is that you're going to have
      to deal with cutter deflection (that's a _big_ one, especially on a
      CNC mill), machine flexing (very important with smaller machines),
      etc. Having to deal with *dynamic* error like the backlash of a rack
      would be really annoying. There are settings to compensate for it,
      but this means the backlash has to remain the same, or you have to
      reset everything. I would definitely consider using a leadscrew with
      an anti-backlash nut.

      This, of course, all depends on the tolerances of your work :)

      Regards,

      Robin


      --- In taigtools@y..., batwings@i... wrote:
      > At 07:21 AM 2/1/01 -0000, you wrote:
      > >The computer system is
      > >magnificient, but I still cling to the idea that for a one-off
      job,
      > >there's nothing quite like the feel of the crank handle in one's
      hand.
      >
      > Actually you get used to it. I cut CNC teeth on a mill that didn't
      have a
      > knob on it anywhere. I do still occasionally take a cut or two on
      manual on
      > my present machines but good software is usually pretty facile and
      you get
      > used to pushing buttons easily and quickly. There is just one thing
      that's
      > vital though: the BRB!! <=Big Red Button. If you don't have your
      kill set
      > up and functional, you will probably be a sad puppy at some time.
      >
      > Regards,
      >
      > Hoyt
      >
      > Belfab CNC - http://www.freeyellow.com/members/belfab/belfab.html
      > Best MC Repair -
      http://www.freeyellow.com/members/batwings/best.html
      > Camping/Caving -
      http://www.freeyellow.com/members/batwings/caving.html
      > 'Has the Oval Office been steam cleaned yet?' <=George W. Bush
    • batwings@i-plus.net
      ... Actually you get used to it. I cut CNC teeth on a mill that didn t have a knob on it anywhere. I do still occasionally take a cut or two on manual on my
      Message 2 of 26 , Feb 1, 2001
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        At 07:21 AM 2/1/01 -0000, you wrote:
        >The computer system is
        >magnificient, but I still cling to the idea that for a one-off job,
        >there's nothing quite like the feel of the crank handle in one's hand.

        Actually you get used to it. I cut CNC teeth on a mill that didn't have a
        knob on it anywhere. I do still occasionally take a cut or two on manual on
        my present machines but good software is usually pretty facile and you get
        used to pushing buttons easily and quickly. There is just one thing that's
        vital though: the BRB!! <=Big Red Button. If you don't have your kill set
        up and functional, you will probably be a sad puppy at some time.

        Regards,

        Hoyt

        Belfab CNC - http://www.freeyellow.com/members/belfab/belfab.html
        Best MC Repair - http://www.freeyellow.com/members/batwings/best.html
        Camping/Caving - http://www.freeyellow.com/members/batwings/caving.html
        'Has the Oval Office been steam cleaned yet?' <=George W. Bush
      • batwings@i-plus.net
        ... Right, jog is invaluable in set-up. It s basis for several functions too: you can jog tools to a common reference position on part or datum and then the
        Message 3 of 26 , Feb 2, 2001
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          At 04:27 PM 2/1/01 -0000, you wrote:
          >Depending on the controller you make/buy, you can have manual jog
          >settings and the MDI interface.

          Right, jog is invaluable in set-up. It's basis for several functions too:
          you can jog tools to a common reference position on part or datum and then
          the CPU records their offsets in a table; next time the tool number is
          called, it auto-homes, prompts user to change, delivers tool to the spec
          position and displays corrected coordinates; hence every tool starts
          working at its own zero values! So data to enter comes right off drawing.
          Tool numbers can go into files or be called manually. Can even change
          non-indexable tools in mid-program and as long as re-qual'd again by
          touch-off at orginal ref, the software is set up to take the difference in
          tip location, apply it, and then go back to the right position on part and
          continue file. Can even re-cut lines previous if specified, to correct
          effect of bad tool. I have my stuff set up so if you name a tool not
          already in table, it calls jog routine and lets you qual it right then in
          middle of program being written, and you la-de-da ahead with a smile. This
          is only part of power of CNC.

          Jogging is also used teaching arcs or feeds in multiple axes, then that
          move is put into file being written just as were MDI lines. Very handy for
          building something w/o actually having dimensions. The machine generates
          the file for next part with whatever dimensions you taught it. Can mix
          teaching of course with straight MDI. It all goes into file. I use teach to
          make files for cutting copper gaskets. Just walk the machine around the
          sample part giving it three points on each arc and two on each line,
          touching off with the same tool to be used if desired. Then bingo, next
          part is a dupe of that path.

          >you can just use a dial (or computer keys) to jog the cutter as far
          >as you want, as fast as you want, just like a manual mill/lathe with
          >a digital readout.

          Mine uses exponent, give it a 2 and you get 100 steps, 5 and get 10,000.
          You can just enter the next exponent smaller amd smaller again to change
          scale on your approach. One keypeck = one jogstep of whatever size. I use
          metric screws, so jog is in metric too.

          >lets you type in G-code one line at a time, and execute it instantly.
          >This can be very useful, BUT, it can be _VERY_ dangerous. If you miss

          That is the big advantage of conversational programming and canned
          routines. You can generate hundreds of lines with a few entries, such as
          multipass turning, peck drilling, digitizing, etc. And the CPU doesn't make
          math or format errors. In fact it hardly matters if you use G-code or not,
          my setup doesn't. The actual code is something you seldom have to address,
          just build it and run it. One of my basic principles was that every
          movement, setting or parameter goes to file whether you named a file for
          that or not. This way if you screw up and make something useful w/o
          intention, you still have the file to run. The idea of course is skilled
          machinist doesn't need to be a programmer. He merely needs to know how to
          run machine. Machine and CPU take care of the rest.

          >As for the rack idea, I'm not sure that's such a great thing. In CNC,
          >you don't really want to have to mess about with backlash crap -

          Lash comp is almost never very effective. Ball screws are the answer. Not
          only are they precise but they're very stiff mechanically. As I mentioned,
          rolled screws are cheap, robust and pretty darned accurate. Certainly most
          jobs can be done with precision of .005"/ft. HAGO
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