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Thread: How long does it take to program a thread cutting operation on a CBC ?

  1. #11
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    Along the subject matter of this thead, I should point out that my replies pertain to the Dynapath control my lathe has. Different controls have different features, some more, some less. Some do NOT have a conversational mode. Some are real non user friendly, heidenhein comes to mind.

    With cnc machines, the conrrol has more to do with the machines capabilities than the iron has. This is also the reason it is popular for hobby guys to buy older cnc machines with bad electronics and update them to a new control giving that old machine the same features as the newer stuff. In the cnc world, you can teach a old dog new tricks.

    IF the control on my lathe ever has a failure that is cost prohibitive to repair, I would switch it over to linuxcnc in a heartbeat.

  2. #12
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    These CNC lathes that perform threading by precisely timing the turning speed with X/Z in a closed loop might be difficult to duplicate (without spending a lot of $$$) if you're not able to reuse the same VFD, sensors, servos, etc.
    Work hard play hard

  3. #13
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    Quote Originally Posted by 3 Phase Lightbulb View Post
    These CNC lathes that perform threading by precisely timing the turning speed with X/Z in a closed loop might be difficult to duplicate (without spending a lot of $$$) if you're not able to reuse the same VFD, sensors, servos, etc.
    Its far more simple than you think. There is a encoder driven by the spindle. The carriage feed is calibrated by way of the ballscrew pitch and the encoder on the servo motor for the z axis. The "computer" simply syncronizes the 2 signals. You have enough electronics knowledge that it would be a walk in the park. The mechanics of mounting the servos and encoder is actually the difficult part.

    VFD does not matter, if the speed varies any the computer just adjusts the feed instantaneously to compensate.

  4. #14
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    Here is a video that shows how cnc threading works. It accomplishes the same end result as the spindle being geared to the Z feed but does it electronically. Spindle speed variances have no effect.

    Can't get a worse spindle speed stability than this video ! (by the way, it would track the other way if he turned the spindle backwards once and a while)

    https://www.youtube.com/watch?v=fWFxPgcpgSg

  5. #15
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    Quote Originally Posted by Sparky_NY View Post
    Its far more simple than you think. There is a encoder driven by the spindle. The carriage feed is calibrated by way of the ballscrew pitch and the encoder on the servo motor for the z axis. The "computer" simply syncronizes the 2 signals. You have enough electronics knowledge that it would be a walk in the park. The mechanics of mounting the servos and encoder is actually the difficult part.

    VFD does not matter, if the speed varies any the computer just adjusts the feed instantaneously to compensate.
    I'm sure you right. The speeds are not that high. I was thinking over/undershoot errors+corrections could be greater with LinuxCNC but maybe not depending on the setup+latency+etc.
    Work hard play hard

  6. #16
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    Quote Originally Posted by 3 Phase Lightbulb View Post
    I'm sure you right. The speeds are not that high. I was thinking over/undershoot errors+corrections could be greater with LinuxCNC but maybe not depending on the setup+latency+etc.
    In the electronic realm the speeds are slow. Actual threading in not necessarily slow, its common to thread at 1000/2000 rpms. Its scary to see it thread at those speeds, especially up close to a shoulder !

  7. #17
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    Yes I was talking a male thread, work already to size, 5 /16 x18 an inch long I had said.
    Just curious partly or mostly because to some people it seems to be a task they deem difficult or they prefer to avoid.
    Of course it depends on your lathe and skill a lot.
    That said I find it pretty easy, and I used a laydown threading tool, and my gearbox is very easy to setup for a wide range of metric and standard, without pulling gears.
    So one day I decided to time it, blank was ready, no tool in toolpost. It took 8 minutes.
    So I thought for a onesy on a manual lathe that was not too bad.

    Of course second is quicker, but it would be even quicker on the CNC..
    The good thing is there is hope for those learning, it can be pretty quick.

  8. #18
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    Now threading with a die head on a turret lathe is pretty fast.
    I used to 3/8 nf about 2.5 inches long, about 200 a day or so.

  9. #19
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    Quote Originally Posted by 754 View Post
    Now threading with a die head on a turret lathe is pretty fast.
    I used to 3/8 nf about 2.5 inches long, about 200 a day or so.
    That sounds worse than an Asian sweat shop!
    Work hard play hard

  10. #20
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    Quote Originally Posted by 754 View Post
    Now threading with a die head on a turret lathe is pretty fast.
    I used to 3/8 nf about 2.5 inches long, about 200 a day or so.
    For home shop guys, speed usually isn't a prime factor in getting cnc capability (lathe and mill). Capabilities are more the reasons. I can't help but think of Brians latest engine build thread... he just made the flywheels, long slow process with many difficult operations. Those flywheels could be done with a single endmill easily on a cnc mill, size of that endmill not being critical. The round holes around the center area could also easily have been any shape, not just round. Things like rotary tables with multiple setups become a thing of the past.

    Most of my machining skills were learned on such manual equipment so I have operated in both worlds. I also understand well why people that have only used manual equipment do not relate to why CNC has taken such a leap in the home shop. I still have a manual 13x40 lathe which I use often, no manual mill anymore tho, I DO use the cnc mill in "manual" mode a fair amount.

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