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  1. #81
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    Quote Originally Posted by Mtndew View Post
    Oh, and for worst website ever? I'd have to give it to Maryland Metrics.
    It will burn your retinas.
    MARYLAND METRICS 'HOME PAGE'

    FFS!!! It's 4am here, the ole lady's passed out on the couch, I'm T-casting to the 70" TV and I clicked that! Now I got a half asleep Asian chick bitching in three different languages because I just lit the neighborhood up.

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    Rolling shutter.. lol

    How is a rotating cylinder going to produce side to side motion due to a camera's rolling shutter effect?

    Did you rolling shutter guys notice the center of the airline prop? (spinner?) Is it wobbling too?

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    Quote Originally Posted by g-coder05 View Post
    FFS!!! It's 4am here, the ole lady's passed out on the couch, I'm T-casting to the 70" TV and I clicked that! Now I got a half asleep Asian chick bitching in three different languages because I just lit the neighborhood up.
    I saw the glow from over here!

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    Quote Originally Posted by gkoenig View Post
    Everyone keeps citing rolling shutter. I won't go into a technical discussion of camera stuff, but just look at the floor of that cut - that shit is full up Machu Picchu. Obviously the end mill was moving in weird ways given how tiered the floor is from what was programmed as a simple slot.
    I mentioned rolling shutter because it looks like spindle/toolholder is bending or swaying like tree in a wind..
    Guessing something like 2-3mm movement and that would be awfully lots of deflection from toolholder alone. Just curious in here like everyone else, feedback going nuts or what?

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    Quote Originally Posted by MattiJ View Post
    I mentioned rolling shutter because it looks like spindle/toolholder is bending or swaying like tree in a wind..
    Guessing something like 2-3mm movement and that would be awfully lots of deflection from toolholder alone. Just curious in here like everyone else, feedback going nuts or what?
    Or it is bending and swaying in the wind since the cut is so abusive? It is 50-60 cubic in/min removal

    not to mention with such a long gage length

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    Quote Originally Posted by thesidetalker View Post
    Or it is bending and swaying in the wind since the cut is so abusive? It is 50-60 cubic in/min removal
    Might be because that WWF...Titan guy

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    For what it's worth, Titan's instagram has a post explaining some of this - in particular he outright admits that the tool holder is "too big" - something about needing it to get "air through".

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    Quote Originally Posted by cameraman View Post
    BUT he's trying to see if he can break that end mill and that machine is the most powerful that he currently has on his shop floor.
    As someone pointed out earlier though, that holder looks janky. Some Kennametal hydraulic dingus? IDK what it is, but it seems stupid to have a long stickout neck, than a big holder section, then the end mill sticking out. They can defend how it works, but it doesn't look very effective. Like the airplane guys say - if it looks right, it flies right.

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    Quote Originally Posted by Mtndew View Post
    You DO know they test extensively, right? They aren't just booksmart, they have their own machines where they test and study over and over. So I'd be willing to wager their results are more reliable than most of us with "real world experiences".
    Besides, their wallet is pretty damn big so they can do things that most people won't even try.


    The only thing I don't like about Sandvik is their website, it's fucking atrocious.
    From Sandvik's website:

    How to a choose spindle

    The diagram below shows the limitations on the respective couplings from theoretical (FEA) calculations for when the face contact is lost (bending stiffness) and fatigue limit is reached (maximum torque).

    Blue: Maximum bending moment (Nm)
    Red: Maximum torque (Nm) within fatigue limit


    I'm not saying Sandvik don't know what they're doing. We buy plenty of Sandvik tooling. But they used FEA simulations, not "extensive" live tests, for this particular data (thanks for rolling your eyes at me btw).

    Big Plus works by spindle deformation. When the face of the toolholder contacts the face of the spindle, the spindle taper elastically expands. Do their FEA simulations account for this? Also, what happens when a Big Plus toolholder loses face contact due to bending moment? The chart suggests that the toolholder outright fails, but that's not the case.

    I've done many, many FEA simulations and on anything as complex as a machine spindle, simulations paint an incomplete picture.

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    That chart makes it clear that I must reconfigure my Rong Fu desktop CNC conversion mill to include a HSK A125 coupling. That'll cut the cubes!

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    Quote Originally Posted by Radar987 View Post
    ....
    I'm not saying Sandvik don't know what they're doing. We buy plenty of Sandvik tooling. But they used FEA simulations, not "extensive" live tests, for this particular data (thanks for rolling your eyes at me btw).
    While the catalog talks about FEA I think they do a fair amount of real world "live" testing, probably more than any other company out there now.
    Many, many years back I would have said Carboloy as the leader but those test labs are gone.
    Most certainly one can screw up a FEA by a lot and when predicting tool life it can and often is off by miles.
    But it does give you some sort of an idea for comparisons as to better or worse.
    Bob

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    Quote Originally Posted by Radar987 View Post
    From Sandvik's website:

    How to a choose spindle





    I'm not saying Sandvik don't know what they're doing. We buy plenty of Sandvik tooling. But they used FEA simulations, not "extensive" live tests, for this particular data (thanks for rolling your eyes at me btw).

    Big Plus works by spindle deformation. When the face of the toolholder contacts the face of the spindle, the spindle taper elastically expands. Do their FEA simulations account for this? Also, what happens when a Big Plus toolholder loses face contact due to bending moment? The chart suggests that the toolholder outright fails, but that's not the case.

    I've done many, many FEA simulations and on anything as complex as a machine spindle, simulations paint an incomplete picture.
    That's a pretty handy graph... IME using FEA to even model the behavior of something like a single low profile high precision ring bearing is super tricky / unreliable to simulate accurately, went through this years ago where we found it easier to just build and test the actual assemblies.

    I'm pretty sure that Sandvik test things pretty extensively as they have to …

    From your graph seems things start going "Pear shaped" for HSK A- 63 at about 250 Nm (lateral forces / bending moment.) ~ 184 foot pounds (ftlbs).

    Interesting on the DMU 50 3rd gen maximum thrust per axis individually (X,Y, Z) is 4800 N (maximum of 1079 lbs)

    With a 6" stick out (tool holder and tool) from the front bearing requires nearly a 370 lb thrust in feed (in Titan's case in the Y direction) to reach that bending moment limit.

    Kinda interesting the machine is having to correct the pull of the cutter (left) by pulling right to stay on track. Those servos are probably run at around 25% or less but still means a roughly 250 to 375 lb thrust to the right (in the X direction) had to be applied (periodically) by the machine in an attempt to keep it in a straight line.

    Kinda underscores how powerful that Kennametal cutter really is.

    Normally Titan stresses that full axial engagement along most of the flank of the tool's cutting edge provides greater stability in cut so that higher loads can be used versus using the "End" of the tool.

    Titan is not stupid so I'm wondering what's up with the DMG Mori relationship. IME the Germans get a little freaked out when you use something in ways that was never intended. I.e. beyond design intent... 'But it works great !" "No, it was never designed for that ! " " But it works great, it's awesome..." " But IT WAS NOT DESIGNED FOR THAT ! " ad infinitum.

    __________________________________________________ ______________________________

    * Caveat : brain totally not working today/ properly.
    Last edited by cameraman; 10-21-2019 at 02:59 PM. Reason: changed a thrust unit

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    Something someone once told me outside the machining world comes to mind.
    "If you don't crash once in a while you are not really trying, you will never know the edge until you cross it"
    Now that I'm getting old I don't like breaking things so I get slow and safe and the younger crowd now passes me and this does also apply in spades on a machine tool.
    Much to be said for pushing a machine to and past it's limits.
    This guy has the fire in his belly, I'd haved like to seen it pushed until it blew up.
    More passes or more speed. Where is that edge and how much do you back off for long and safe runs?
    Bob

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    Quote Originally Posted by cameraman View Post
    From your graph seems things start going "Pear shaped" for HSK A- 63 at about 250 Nm (lateral forces / bending moment.) ~ 184 foot pounds (ftlbs).
    I would have said that's when thing start going sideways.

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    Quote Originally Posted by mhajicek View Post
    I would have said that's when thing start going sideways.
    That's what we say in "Blighty" when things start going wrong or in this case literally sideways lol. "pear shaped" I think that comes from pottery / throwing a pot on a potters wheel when it all goes lovely and then starts going 'pear shaped" and then goes splat (instantly).

    I'm trying to untangle if the cutter wants to pull itself left, then that would create a thrust on the work piece in the opposite direction (right) so the X axis servo picks up this counter thrust and tries to push back on the table in the opposite direction (or in this case the whole X axis saddle and travelling ram assembly + spindle ? ) .

    Some of the older DMU's and DMU monoblocks had indirectly coupled servo drives i.e. belt driven not direct drive. Wonder if those industrial rubber bands give a machine further protection ?

    Interesting what Eric from OrangeVice was saying about all the spindle self protection on the DMG Mori 'Speedmaster" spindles … They really pride themselves on that and also the proposition of how easy it is to trash 20K rpm spindle... ( spindle with extra "spidey senses" to help it have a longer working life makes it a more successful product. )

    Wondering if there were overrides that Titan had to implement (on the control) to make that cut ?

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  22. #96
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    The Danger Zone :


    MoldMaking Technology


    Does that machine have magnetic spindle protection?

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    Quote Originally Posted by cameraman View Post

    Wondering if there were overrides that Titan had to implement (on the control) to make that cut ?
    11/10 for thinking....but I think you're over thinking
    I know some don't want to think the Y is flexing but...
    Have a look at the original pic I posted - where the holder but also the spindle nose was flapping around.
    It settled down when the cutter got to the point in the attached photo.
    Also note, this point is (co-incidence?) the Y position for the X axis slot which doesn't move around.
    10 bucks says if the X axis slot was nearer the start point of the Y slot (ie the Ram was extended out in the Y), then the X slot would also be all over the place.
    I'm 99.99% sure it's ram flex.
    Attached Thumbnails Attached Thumbnails capture.jpg  

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  25. #98
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    Quote Originally Posted by barbter View Post
    I put a posting on his FB page (like others did) that he wiped off...
    If you look at the machine design, it's a Y axis overhung on rails.

    At 1.48, the cutter engages and the holder is "wobbling" but if you look at the screw hole in the spindle cartridge, you can see that is moving too.
    But near the middle of the cut (1.52) it "settles" and isn't moving.
    It is not a trocoidal path - it is a straight slot.

    I think the "toolholder wobble" is a bit of toolholder flexing and a bit of drawbar pressure being overcome.
    Look at the attacked pic of the floor of the slot. The bad movement is clearly shown (1).

    BUT I think the real problem is the machine design - where it's a cantilever Y, my money is on the fact that the whole head/casting is moving in the rails where the head is so far out (being unsupported) and as the head moves back (beyond the photo "1") the engagement of the axis into the rails is now more supported and thus does not flex.

    Shit machine design.

    But kudos to the cutter - that's one strong mofo
    I bought a machine from a dealer that used to service DMG/Mori, the tech was in setting things up and we got talking. They loved Mori lathes, but several of the machines with the floating Y axis on the column were referred to as "the diving board machines", I guess after a while it became tough to keep things flat and square. That video kinda demonstrates the issues with that design.

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    So if you're going to do heavy roughing on that machine do it on the Y+ side of the platter, then spin the platter 180° to get the other half!

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    Quote Originally Posted by mhajicek View Post
    So if you're going to do heavy roughing on that machine do it on the Y+ side of the platter, then spin the platter 180° to get the other half!
    Or you could:

    1- Use a way better holder with less gauge length.
    2- Use the modern HSM techniques that machine was designed for.
    3- Not run abusive speeds/feeds.


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