Turning over 40 x D parts
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    Default Turning over 40 x D parts

    Hey guys, has anyone tried turning with both upper and lower turrets starting in the middle with a slight overlap and turning in opposite directions; one toward the main and the other toward the sub? I was also wondering about starting at opposite ends and turning toward the middle. Anyone have experience doing this? What are the outcomes? Thanks guys!

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    Why?

    I haven't tried that, but my guess is that your 40xD is going to Chatter. Why not conventionally pinch Turn from one end with bothe Turrets?

    R

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    Quote Originally Posted by litlerob1 View Post
    Why?

    I haven't tried that, but my guess is that your 40xD is going to Chatter. Why not conventionally pinch Turn from one end with bothe Turrets?

    R
    I tried that (balanced not pinched) and still got chatter. Even tried increasing SFM to move it out of the frequency and increased the feed. Also tried decreasing SfM. Do you find pinch turning yields better results than balanced?

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    One turret - shallow "V" shaped follower pad made from slippy, robust plastic. Other turret - turning tool.

    Turning turret starts cut from whichever end of stock. After ~1" of turned surface, following turret with V pad locates on freshly turned section, and (shock!) follows cutting tool along cut surface.

    We OF's call them following rests. Still works, even for you young whippersnappers and your newfangled CNC machines. Follower should be on the upper turret to minimize chip incursions. Better still, plumb coolant to the pads to constantly flush and lubricate the plastic.

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    Quote Originally Posted by Tupper87 View Post
    I tried that (balanced not pinched) and still got chatter. Even tried increasing SFM to move it out of the frequency and increased the feed. Also tried decreasing SfM. Do you find pinch turning yields better results than balanced?
    I think there is discrepancy in the definition, it's irrelevant except in the interest of getting answers. Pinch Turning; as I understand it is both Turning Tools running the exact same path at the exact same X and Z location, just double the feedrate (theoretically).

    Balanced Turning; as I understand it is Using a Roughing Tool 180º about and a tiny amount ahead in Z from a Finishing Tool.

    Both of these start Turning from the one end though. I have had good luck eliminating Chatter using (as defined above) Pinch turning, but I have not had luck using it for mass Material removal.

    Either way, try Milland's suggestion of a programmable Follow rest. I haven't Done what you are asking, so I'm useless.

    R

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    I saw this a few years ago and they used a heimbuck(sp?) chuck to do this.

    YouTube

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    You say 40X D, what diameters are you working on?

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    Limey x2

    40D at what size and material?
    How much material to come off?

    40D is not 40D is not 40D.

    .125 x 40 is not the same as 1.25 x 40.

    Tool pressure is a more constant, and the 1.25 bar won't notice it nearly as much as the .125 bar.


    Can you use a box tool?


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    Ox

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    Quote Originally Posted by Ox View Post
    Limey x2

    40D at what size and material?
    How much material to come off?

    40D is not 40D is not 40D.

    .125 x 40 is not the same as 1.25 x 40.

    Tool pressure is a more constant, and the 1.25 bar won't notice it nearly as much as the .125 bar.


    Can you use a box tool?


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    Think Snow Eh!
    Ox
    7.8mm x 312mm.
    1.725mm has to come off.
    No box tool cutter. Atm the tooling I have is what I'm stuck with. May either Jerry rig a follow rest or convince my boss to buy me a box tool. Don't know much about them. Do they adjust to multiple OD's typically?

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    Quote Originally Posted by pcasanova View Post
    I saw this a few years ago and they used a heimbuck(sp?) chuck to do this.

    YouTube
    Fuck me that's genius! So going to try this! Just not sure the stroke on the jaws. If the ID on the jaws isnt much bigger I see it working. But i dont know how well this will work if the ID of the jaws has a large size difference in comparison to the OD of the part.

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    Get on ebay and buy a box tool.
    They are adjustable.
    We may need to help you git it set up.


    That vid is machine specific, and that's what they are showing.
    I am guessing that they have what is known in Star language as a "Magic Guide Bushing" on this machine.

    Similar products sold by Walter Dunner SA in Switzerland. But at $20K/each, the box tool is likely your best choice in the short term....


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    Ox

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    Yeah, the "Swiss" process that video shows it pretty sweet. But you have to be aware of critical speed too, which varies with material stiffness and RPM. At some point the L/D can allow the material to "whip", or exceed its critical speed, so even supported at both ends, or with a box tool or follower, you may have to turn at a slower speed than you'd like.

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    Quote Originally Posted by Tupper87 View Post
    Fuck me that's genius! So going to try this! Just not sure the stroke on the jaws. If the ID on the jaws isnt much bigger I see it working. But i dont know how well this will work if the ID of the jaws has a large size difference in comparison to the OD of the part.
    I would try it too. Just don't get your hopes up, usually you need a certain software and hardware handshake. As the old guy pointed out. But there may be a way to get around it, if you are bound and determined to make it work. We have no idea what control you are using, that might clue us in on what will work and what won't.

    But a Follow rest will be usable, and a Box Tool will too, regardless of the control and interface. Can't say if a Follow rest will solve your problem.

    R

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    the machine isn't anything special, it's all in the chuck. hainbuch is the company who does the workholding.
    its a dual channel 840d siemens. And timing on the siemens is dead simple, trailon command. specify leading axis,slave axis and ratio of movement and command x1 to move and slaves to x2 goes right along with it.
    Not sure if fanuc has the same axis coupling command.

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    Quote Originally Posted by Ox View Post
    Get on ebay and buy a box tool.
    They are adjustable.
    We may need to help you git it set up.


    That vid is machine specific, and that's what they are showing.
    I am guessing that they have what is known in Star language as a "Magic Guide Bushing" on this machine.

    Similar products sold by Walter Dunner SA in Switzerland. But at $20K/each, the box tool is likely your best choice in the short term....


    ------------------------

    Think Snow Eh!
    Ox
    X 2 on Ox, save yourself the grief and unnecessary complications and get yourself a box tool.

    And for those who don't know what we're on about YouTube & YouTube & YouTube

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    I'd seen in the flesh but never used a box tool. I just looked at the vids you linked.
    Awesome piece of kit.

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    Quote Originally Posted by barbter View Post
    I'd seen in the flesh but never used a box tool. I just looked at the vids you linked.
    Awesome piece of kit.
    How about 1 5/8'' nickel aluminium bronze (and a special hard and tough brew for the Admiralty to boot ) down to 3/4'' dia +/- 0.0015 finished!! for up to 12+'' long, in 1 cut, running a brazed carbide tool in the box, at (if memory serves) about 300 RPM and about 0.008'' / rev (it was very abrasive, so the speed was kept low to get the tool life - essential when the orders were several 00's)

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    And no return mark.

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    Quote Originally Posted by pcasanova View Post
    specify leading axis,slave axis and ratio of movement and command x1 to move and slaves to x2 goes right along with it.
    Not sure if fanuc has the same axis coupling command.
    I don't believe that I have a command like that on my 2000 Fanuc, but I'm not seeing anything done there that I couldn't doo. Short of _ of course the Swiss part.
    Obviously the chuck just keeps slight tension on the part during the pull. Actually, I don't see why someone couldn't doo that with about any other chuck if they wanted to. All you need is a low pressure feed line to the chuck and switch between the two. That's more involved than you want to get for one job, but really wouldn't be all that hard. And an M code of course.


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    Quote Originally Posted by pcasanova View Post
    the machine isn't anything special, it's all in the chuck. hainbuch is the company who does the workholding.
    its a dual channel 840d siemens. And timing on the siemens is dead simple, trailon command. specify leading axis,slave axis and ratio of movement and command x1 to move and slaves to x2 goes right along with it.
    Not sure if fanuc has the same axis coupling command.
    That's so when only tapers and plain turning is involved, but not so when all aspects of turning is involved, such as Circular Interpolation. In this regard, the whole package must be capable of Trajectory Interpolation across mixed axes, that is X for one spindle and Z for the other spindle.

    There are many MTB that offer such machines. Mazak have a Twin Spindle (in various sizes) with at least two linear axes per spindle (basically a Left and Right Hand lathe joined together) with a function labeled Swiss Mode. In this Mode one spindle provides the Z axis and the other the X, with true interpolation across the two axes. This is not possible with simple electronic gearing that you're referring to.

    Quote Originally Posted by Ox
    Actually, I don't see why someone couldn't doo that with about any other chuck if they wanted to.
    Hello Ox,
    Its not all that simple. A lot of twin spindle, multi axes machines don't precisely know what each axis of one spindle is doing in relationship with each axis of the other spindle. Accordingly, without electronic gearing, or the capability of Trajectory Interpolation across typically unrelated axes, the best you could do is rely on timing between the two spindle axes to produce a result. Plain parallel turning would be possible, but anything past that is a fudge.

    Regards,

    Bill

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