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

Re: [taigtools] Making a really thin paraboloid?

Expand Messages
  • Tom Benedict
    ... Got a funny on that one, too! If anyone gets the chance to visit McDonald Observatory in the Davis Mountains in West Texas, be sure to go on a tour of the
    Message 1 of 29 , Aug 31, 2003
      On Sun, 31 Aug 2003, Paul Anderson wrote:

      > Tom Benedict wrote:
      >
      > > Apparently some people at ESO pointed a four meter
      > > telescope at Venus and the collected light heated up their CCD enough to
      > > damage it.
      > >
      > Piffle! Makes you wonder what would happen if they pointed it at the sun:)

      Got a funny on that one, too!

      If anyone gets the chance to visit McDonald Observatory in the Davis
      Mountains in West Texas, be sure to go on a tour of the summit, but also
      try to catch the solar observing.

      Frank Cianciolo, who's now director of the Visitor's Center, used to give
      the solar observing tour on a little 5" or 8" telescope. At first he did
      it with a 3" aperture mask, and used the telescope to project the image
      onto a 3x5 card, but without fail someone would ALWAYS try to stick their
      head in front of the card and look through the telescope directly. Frank
      took to starting his speech by using the telescope to burn holes in one of
      the visitor's center pamphlets, and handing it to whoever looked most
      likely to stick their head in the beam. Even with that, people still
      tried it.

      These days I think they've got some dedicated video setup, so the risk is
      a think of the past. Still, one of my fondest memories of the place is of
      Frank burning holes in a pamphlet, handing the still smoking paper to some
      kid, and saying, "Don't."

      Tom
    • Tom Benedict
      I finished the prototype. It s not all THAT thin, but that s for another day. I ve uploaded pictures to my photo gallery. It s cut out of 2 diameter
      Message 2 of 29 , Sep 1, 2003
        I finished the prototype. It's not all THAT thin, but that's for another
        day. I've uploaded pictures to my photo gallery. It's cut out of 2"
        diameter Delrin, and was done with my CNC mill converted to a lathe.

        Unfortunately I still haven't found all my lathe tools since moving, so I
        wound up using a facing tool swung around at an angle. It's got a
        miniscule tip radius, so the cut looks a little ragged. It's pretty
        smooth to the touch, though. I also wasn't 100% careful about setting up
        the tool, so there's a central pip because the tool wasn't completely on
        centerline. When cutting the final part, I'll either find the rest of my
        tools, or grind a new one to spec. I'll also be a lot more careful when
        centering, and use a slower feed to improve surface quality.

        After careful consideration, I'm going to urge the guy doing the optical
        design to either live with the fiber fed pinholes, or spend the time to
        let me learn how to make draw dies. We're in a bit of a rush, so my guess
        is we're going with fiber.

        My only concern with all this is that I was told to hold the figure to
        1/10mm, which I've done, and to make a part about 50mm in diameter, which
        I've done. I get the uncomfortable feeling this "prototype" may wind up
        being part of the production optics. Hopefully I've still got enough
        Delrin to make a better part and slip it in.

        While all this was going on, a hurricane passed not too far from here.
        There was no real damage where I am, but my shop took on a little water.
        Mmmm, gotta love my Shop Vac.

        All in all I'm pretty stoked. I got to try my hand at contour milling,
        and even though I didn't use it the results were great. I also got to try
        cutting a mathematical profile on a lathe. Again, the results were great.
        I'm also learning about draw dies, even though I may not wind up making
        them for this project. Can't complain. Shop life is good.

        Tom
      • Tom Benedict
        I wound up on a web site for a PCB milling machine that got me thinking about toolchangers again. At one point someone (ticutter?) was discussing designing a
        Message 3 of 29 , Sep 4, 2003
          I wound up on a web site for a PCB milling machine that got me thinking
          about toolchangers again. At one point someone (ticutter?) was discussing
          designing a toolchanger for the Taig CNC mill. Any word on this?

          The PCB milling machine I saw had automatic tool changing capability. It
          had a rack on the mill table that held around six to eight tools, each in
          a toolholder. The pictures weren't large enough to see what the
          spindle-end of the toolholders really looked like. To change tools, it
          would move to an empty spot in the rack, magically release the tool, move
          to a new spot, and magically pick up the new one.

          Near as I can tell, at the very least you need:

          1 - A way to start and stop the spindle

          2 - Some way to know where all the tools are

          3 - A way to grab a toolholder

          4 - A way to release a toolholder


          #1 can be handled with a relay. I'm in the process of adding this to my
          mill at the moment. Still waiting on parts.

          #2 can be handled with home switches and some way to refer to an absolute
          coordinate frame. (I hope.) So long as the tool rack lives in the same
          place all the time, this would be a one-time setup.

          #3 and #4 are the kickers. I'm sure there are lots of ways to do this,
          but the one that keeps coming up in my mind is some sort of power drawbar.
          I'd like to think there are better ways to do this. The paper sketch I
          have at the moment involves a power drawbar, and a collet/toolholder setup
          with a taper and splines. I'm fairly certain it would work, but it's not
          pretty and I'd rather not build it.

          For PCB milling, you may be able to get away with something as
          straightforward as a nice strong magnet to keep the collet seated, and a
          coil to force tool release. I don't know. (This might explain the way
          the toolholders appeared, small though the pictures were.) I've had
          enough tool dig-ins not to want to go this route on my mill. Firm
          mechanical attachment is a good thing.

          I don't know if I'm ready to take this on as a project yet, but I'm
          certainly interested in looking at design ideas. Has anyone tried to
          build such a beast for their Taig? I know someone built a full-blown
          turret tool changer for a Sherline. I wouldn't be against setting up
          something like that, either.

          Always looking for new reasons to go, "WHAT?! HIT ESTOP!" in my shop...

          Tom
        • mark allen
          i got home from work tonite to find a package on my doorstep, got all happy and thought about dancing a jig... then i decided to stop in here at the forum to
          Message 4 of 29 , Sep 8, 2003
            i got home from work tonite to find a package on my doorstep, got all
            happy and thought about dancing a jig... then i decided to stop in
            here at the forum to say: "my lathe bed is longer than your lathe
            bed. neener."

            ;-P
            mark
          • Tom Benedict
            ... Pictures! I want pictures! Don t worry, I trust you. But if you re going to make me lust after your lathe bed, do right by me and let me know exactly
            Message 5 of 29 , Sep 8, 2003
              On Tue, 9 Sep 2003, mark allen wrote:

              > i got home from work tonite to find a package on my doorstep, got all
              > happy and thought about dancing a jig... then i decided to stop in here
              > at the forum to say: "my lathe bed is longer than your lathe bed.
              > neener."

              Pictures! I want pictures! Don't worry, I trust you. But if you're
              going to make me lust after your lathe bed, do right by me and let me know
              exactly what I'm missing.

              Tom
            • Tony Jeffree
              ... Mark - Is this an extruded aluminium lathe bed, or is it steel like the normal-length Taig? Regards, Tony
              Message 6 of 29 , Sep 9, 2003
                At 02:13 09/09/2003 +0000, you wrote:

                >i got home from work tonite to find a package on my doorstep, got all
                >happy and thought about dancing a jig... then i decided to stop in
                >here at the forum to say: "my lathe bed is longer than your lathe
                >bed. neener."

                Mark -

                Is this an extruded aluminium lathe bed, or is it steel like the
                normal-length Taig?


                Regards,
                Tony
              • mark allen
                the bed in question is a cuesmith bed. four feet long. $250. i m not entirely sure of it s composition... i m pretty new at this. it s rather light.... lighter
                Message 7 of 29 , Sep 9, 2003
                  the bed in question is a cuesmith bed. four feet long. $250. i'm not
                  entirely sure of it's composition... i'm pretty new at this. it's
                  rather light.... lighter than i was expecting. but then i don't have
                  a little bed to compare to. nevertheless... if it'll work for cue
                  turning, it'll work for my needs. . . 4" diameter stainless... about
                  30" long.

                  just kidding. i just want to spin slightly longer chunks of wood than
                  the little bed'd handle.

                  have a day :-|

                  mark
                Your message has been successfully submitted and would be delivered to recipients shortly.