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  1. #21
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    Quote Originally Posted by jz79 View Post
    this is supposedly what it looks like:
    Attachment 267532

    I'm not very experienced with this, but I wouldn't call that a shit design...
    On a machine of this size, and cost, the LAST thing I'd expect to see is an axis "floating" about.
    It's a high torque spindle - but what's the point of that if you can't use it (rigid tapping 2" pipe threads? )
    Cutters of that diameter should snap like a carrot long before the axis should be bouncing around.
    If I was DMG, I'd be putting a video out this morning with a short stubby holder etc to try and clear my name...

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    Quote Originally Posted by jz79 View Post
    this is supposedly what it looks like:
    Attachment 267532

    I'm not very experienced with this, but I wouldn't call that a shit design...
    I'm just an amateur (hack) machine/mechanical designer, but to me that Y/Z casting looks very light, as if designed for HSM and not roughing as was shown in the video. I could easily see that thin wall casting deflecting and allowing a torsion displacement of the cutter, in line with what barbter mentions in #19.

    I couldn't tell if there was movement at the toolholder/spindle interface, my guess is casting twisting and perhaps the spindle and Z axis ways deflecting a bit too. But I'd blame the casting for most of the uncontrolled movement.

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    Quote Originally Posted by barbter View Post
    On a machine of this size, and cost, the LAST thing I'd expect to see is an axis "floating" about.
    It's a high torque spindle - but what's the point of that if you can't use it (rigid tapping 2" pipe threads? )
    It's a 12,000 lb machine.

    Who said anything about high torque? HSK63 and high torque is an oxymoron.

    The cut was clearly outside of the design parameters of the machine.

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    Quote Originally Posted by gregormarwick View Post
    If that was a 40 taper that would have gone south very quick. Dual contact and high retention force is what kept that from detonating.
    HSK is not more rigid than the equivalent 40 or 50 taper. It simply does better at high speed.

    Higher drawbar force doesn't make up for the thin walls and the short taper.

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    Quote Originally Posted by Radar987 View Post
    HSK is not more rigid than the equivalent 40 or 50 taper. It simply does better at high speed.

    Higher drawbar force doesn't make up for the thin walls and the short taper.
    Sandvik published a study years ago where they tested the load deflection rates of various spindle interfaces. The purpose was obviously to show how wonderful capto was, but the difference between HSK and dual contact steep taper was surprising, and the difference between HSK and plain steep taper was massive.

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    At quick glance it looks like tool holder deflection but I've learned modern videos can be very unreliable due to the image stabilization crap. I've taken several videos where at first the spindle appears to be moving in the X and Y axis when it is not. I'm not a video guy but I'm going to assume when the camera senses movement of a large section of the frame it assumes that is because the camera is unsteady and moves a smaller part of the frame instead. This can make for some pretty funky looking videos.

    There is obviously something bad going on and that cut is beyond the capabilities of that setup, but all I am saying is the video can't be used to make an accurate determination of where the flex/distortion is coming from because we don't know what kind of new fangled digital processing stuff was used. If a proper high speed camera with an independent datum in frame was used I would give some credit to video analysis. IMO

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    Interesting. I couldn't figure out what the motion was. Didn't really look like flexing to me but I couldn't come up with another answer. That camera stabilization or frame rate idea didn't occur to me.

    Thanks Hardplates

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    Quote Originally Posted by Chris59 View Post
    Interesting. I couldn't figure out what the motion was. Didn't really look like flexing to me but I couldn't come up with another answer. That camera stabilization or frame rate idea didn't occur to me.

    Thanks Hardplates
    I agree that Hardplates makes a very valid point.
    But if it isn't flexing (or mechanical shock), what's causing the floor finish and why is it better the closer the Y (Ram) goes back into the main casting...
    Attached Thumbnails Attached Thumbnails capture.jpg  

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    Quote Originally Posted by gregormarwick View Post
    Sandvik published a study years ago where they tested the load deflection rates of various spindle interfaces. The purpose was obviously to show how wonderful capto was, but the difference between HSK and dual contact steep taper was surprising, and the difference between HSK and plain steep taper was massive.
    I take anything Sandvik publishes with a grain of salt.

    It's been discussed here on a few occasions that for low speed hogging, it's hard to beat good old 7/24 tapers. Real world experiences from people with both types of spindles, not some dudes running around in yellow lab coats.

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    Quote Originally Posted by Hardplates View Post
    At quick glance it looks like tool holder deflection but I've learned modern videos can be very unreliable due to the image stabilization crap. I've taken several videos where at first the spindle appears to be moving in the X and Y axis when it is not. I'm not a video guy but I'm going to assume when the camera senses movement of a large section of the frame it assumes that is because the camera is unsteady and moves a smaller part of the frame instead. This can make for some pretty funky looking videos.

    There is obviously something bad going on and that cut is beyond the capabilities of that setup, but all I am saying is the video can't be used to make an accurate determination of where the flex/distortion is coming from because we don't know what kind of new fangled digital processing stuff was used. If a proper high speed camera with an independent datum in frame was used I would give some credit to video analysis. IMO
    Image stabilization as you describe it is how youtube did it years ago, it was absolutely horrible - motion sickness inducing, and caused terrible image distortion.

    Modern digital stabilization works very differently (moves the whole frame uniformly around temporal datum points, and then crops the edges).

    Even higher end phones have mechanical stabilisation in the lenses anyway these days.

    I doubt that image stabilisation is at play here in any meaningful way.

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    Quote Originally Posted by Radar987 View Post
    I take anything Sandvik publishes with a grain of salt.

    It's been discussed here on a few occasions that for low speed hogging, it's hard to beat good old 7/24 tapers. Real world experiences from people with both types of spindles, not some dudes running around in yellow lab coats.
    I admittedly don't have much experience with HSK.

    I do have a lot of experience with 50 taper, and I do have a lot of experience with capto, and I do have a lot of experience with heavy machining.

    Capto beats steep taper hands down, and not necessarily even in the equivalent size. C8 is closest to 50 taper dimensionally, but even C6 is stiffer.

    Capto and HSK have very similar retention forces, similar taper angle, and are both dual contact. So I have no reason whatsoever to doubt sandvik's study.

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    Quote Originally Posted by barbter View Post
    I agree that Hardplates makes a very valid point.
    But if it isn't flexing (or mechanical shock), what's causing the floor finish and why is it better the closer the Y (Ram) goes back into the main casting...
    Another interesting point. Still unsure. Perhaps the tool was sharp initially and gouged the bottom til it self honed under the insane cut? Usually when I see flexing it's in one direction. Fascinating subject though. Thanks

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    Quote Originally Posted by gregormarwick View Post
    Image stabilization as you describe it is how youtube did it years ago, it was absolutely horrible - motion sickness inducing, and caused terrible image distortion.

    Modern digital stabilization works very differently (moves the whole frame uniformly around temporal datum points, and then crops the edges).

    Even higher end phones have mechanical stabilisation in the lenses anyway these days.

    I doubt that image stabilisation is at play here in any meaningful way.
    I watched a youtube video about frame rate with propellers. You get very odd results. I wonder if this is part of the problem?

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    Quote Originally Posted by barbter View Post
    I agree that Hardplates makes a very valid point.
    But if it isn't flexing (or mechanical shock), what's causing the floor finish and why is it better the closer the Y (Ram) goes back into the main casting...
    Something is definitely moving and not right. All I am saying is I don't think that video is useful for analyzing anything beyond "somethings not right here"

    Quote Originally Posted by gregormarwick View Post
    Modern digital stabilization works very differently (moves the whole frame uniformly around temporal datum points, and then crops the edges).
    That being said the fact it crops the edges would seem to me like it would be more capable of hiding its foolery. As I said I am not a "cameraman" but I do know that best way to analyze something is to begin with removing as many potential variables as possible. I would consider a reality TV video a variable and not reliable scientific evidence. IMO

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    Quote Originally Posted by Chris59 View Post
    I watched a youtube video about frame rate with propellers. You get very odd results. I wonder if this is part of the problem?
    That's due to the "rolling shutter" capture method.

    About the only artifact that might be encountered in this kind of scene from that would be some horizontal shearing, but nothing here is really moving fast enough.

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    "Harvey 3 is six flutes" and he holds up 5 fingers. What a clown

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    Quote Originally Posted by jz79 View Post
    this is supposedly what it looks like:
    Attachment 267532
    Quote Originally Posted by Milland View Post
    I'm just an amateur (hack) machine/mechanical designer, but to me that Y/Z casting looks very light, as if designed for HSM and not roughing as was shown in the video. I could easily see that thin wall casting deflecting and allowing a torsion displacement of the cutter, in line with what barbter mentions in #19.
    I'm in the same amateur category, so it is just speculation on my part

    interesting that in the picture I linked earlier, 3rd gen DMU 50 (which seems to be the one in the video), the Y/Z casting is quite a bit wider than in the 2nd gen machine, indicating that there was a need to beef it up

    and then there is the case of linear guides, which don't transmit vibration as well as box ways, meaning that the X/Z casting may have started to oscillate because it couldn't pass the vibration down to the rest of machine effectively enough

    here is a pic of a bare 2nd gen, note how narrow the Y/Z casting is:
    dmu50_2nd_gen.jpg

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    Quote Originally Posted by jz79 View Post
    about the cutter, app chart says Fz ~0.10mm (0.12-20%) at 1.25xD, and he did 2.50xD at same Fz, it survived, but how long would it last?
    Long enough to make the video, I guess that's all that counts?

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    Quote Originally Posted by Larry Dickman View Post
    "Harvey 3 is six flutes" and he holds up 5 fingers. What a clown
    Does the Harvi6 have 3 flutes? Lol

    Sent from my moto g(6) using Tapatalk

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    I don't watch Titans stuff, not really interesting to me. His stuff is almost like any "reality" based programming, drama must be added to interest viewers. I'm interested in machining, not drama.

    That being said...It looks to me like he was promoting an endmill, not a machine. Regardless of what's going on there, it is impressive that the endmill didn't blow up, and it took some serious cuts/abuse.

    It does say something about the product, and I think that was the message he was trying to convey.

    The video has people talking, mission accomplished.

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