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IndustryArena Forum > MetalWorking Machines > Novakon > TTS - Spring Pressure ?
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  1. #1
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    TTS - Spring Pressure ?

    For those of you who have setup your own quick change system around the TTS style tool holder... How much spring pressure do you need to be able to push a 1/2" or larger end mill with decent loads without slipping?
    Bob La Londe
    http://www.YumaBassMan.com

  2. #2
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    Re: TTS - Spring Pressure ?

    Quote Originally Posted by Bob La Londe View Post
    For those of you who have setup your own quick change system around the TTS style tool holder... How much spring pressure do you need to be able to push a 1/2" or larger end mill with decent loads without slipping?
    To avoid slipping entirely, even under worst-case conditions, something over 3000# for a machine with a 1.5HP spindle. If your spindle power is less, less tension is required.

    Regards,
    Ray L.

  3. #3
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    Re: TTS - Spring Pressure ?

    I have the lever drawbar on mine. I have to make sure that it is as tight as I can get it with a ratchet and an adjustable wrench. Not using all my strength, but pretty tight. Then I reinstall the LDB and it works fine for a 1/2" 4 flute in aluminum.
    Lee

  4. #4
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    Re: TTS - Spring Pressure ?

    So with a 7/16 draw bar a stack of only 3 front to back of these would have enough force to hold? McMaster-Carr Would they have enough travel? How much travel do you need to get the tool to fall out cleanly?

    How long of a lever do you need to compress it easily?
    Bob La Londe
    http://www.YumaBassMan.com

  5. #5
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    Re: TTS - Spring Pressure ?

    Three of those stacked would likely give enough tension, but not enough travel. You need on the order of 0.075" travel to release the TTS holder. So, you'dd need several stacks of 3. Then you get into the problem of keeping them all concentric, so they don't throw spindle balance off.

    Personally, I don't think a manually-operated drawbar with that much tension is practical, unless you have a hydraulic intensifier on it.

    Regards,
    Ray L.

  6. #6
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    Re: TTS - Spring Pressure ?

    Well, a 6 ton arbor press is manually lever activated, albeit with a rack and pinion setup. I use a cheater bar on mine, but only for the hardest pressing jobs. Most jobs I just use the stock handle. Pneumatic actuation is no big deal either. Takes about 33-1/3 Square inches at 90 PSI. Either 6.5 inch piston or two stage or use more air pressure if you have it available.

    If concentricity is so critical how are all the other DIY TTS type systems done? Its not like there aren't more than a few of them out there.
    Bob La Londe
    http://www.YumaBassMan.com

  7. #7
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    Re: TTS - Spring Pressure ?

    Bob,

    Very few DIY PDBs get anywhere near 3000#. The very few I've seen that do, and do it reliably, use hydraulics. The Tormach PDB uses a huge air cylinder, but only gets about 2500#, and many who have that one consider it for "light duty" only, lest they get pull-out. Also, I would not want to put all that force on the spindle bearings. It might not hurt them, but why take the chance? A really huge lever can put really huge forces on the column and ways - not good. Do what you want, but, other than the God-awful impact wrench kind, I've only ever seen a few PDBs get up into the right range of tension to completely eliminate TTS pull-out, and they've all been either hydraulic, or, like mine, electric. Most are in the 1000-2000# range, which is simply not enough, unless you're machine is under 1HP. The Belleville spring ones are mostly using a short stack of springs - 3-6 or so. They get away with this due to the low force they require.

    Regards,
    Ray L.

  8. #8
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    Re: TTS - Spring Pressure ?

    By SCzEngrgGroup's recommendation I tried to get the one I made up to about 3000 pounds. It IS one of the hydraulically multiplied variety though.
    Here's one of my first tests (note the face shield)...
    https://www.youtube.com/watch?v=4zXj7LT5Q6g

    I'm pretty sure these are what I used most recently...
    McMaster-Carr

    0.075" sounds like a good number to shoot for. I shot for 0.050", but sometimes it was inadequate.

    The thing about a 6-1/2" piston for Torus Pro owners is that there is not enough room to fit a 6-1/2" piston above the spindle. I'm not sure for what machine you have though.

    I did get pullout on occasion, only when there was significant chatter and then only sometimes.

  9. #9
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    Re: TTS - Spring Pressure ?

    Bob,

    Something else to keep in mind - if you target 3000# drawbar tension, you'll probably need upwards of 4000# to compress the springs enough to release it, as you'll have to compress the springs considerably further, and they are highly non-linear in that range. That's why it's not unusual ffor VMCs to have a stack of as many as 150 Belleville springs in their drawbars, so they can get a long throw, and linear response.

    Regards,
    Ray L.

  10. #10
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    Re: TTS - Spring Pressure ?

    I wasn't all that concerned with getting the force needed. I've been doing some work recently with HPA stuff (3000-4500 PSI) and I am pretty confident in my ability to manufacture a multi stage air piston that will hold up and produce large gross power with low PSI (shop air) source. I'm not sure why I would put any of that major force on the head. Anything I designed would compress the stack, not push down on the stack. There might be a couple hundred pounds on the head momentarily, but a machine crash will cause more than that. I was looking at a lever mech to do something similar. With a 4' cheater bar a 200lb guy just hanging on it will generate adequate force I think. Still, those are all valid considerations.

    I was more concerned with the balance issues one poster mentioned from using a stack of belleville washers. Since using a large stack of bellevilles was mentioned on VMCs how does a VMC deal with that? My first thought was a dynamic balancer of some kind, but somehow that seems like overkill to me. A liquid filled torus might work, but there has to be an easier way. Obviously if you are turning 10K or more its much more important than if you are turning 3K or 0.5K.

    I posted here because I knew a few guys in this group were using TTS style tool holders. My application is a converted ZX-45 with a 2HP spindle motor. Most of the milling I do with it is light, and I could take the "good enough" approach, but I wanted to do better.

    I appreciate all of your criticisms.
    Bob La Londe
    http://www.YumaBassMan.com

  11. #11
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    Re: TTS - Spring Pressure ?

    On VMCs, the Belleville stack is inside the spindle itself, so they are well constrained. That's very hard to do as an add-on to the spindle with a stack of any length, at least if personal safety is a concern.

    Hmmmm.... A 4-foot "cheater" bar, attached out near the spindle, pulling against the column, with the head all the way up.... You'd got some serious leverage going right there, albeit much of it being applied at all the wrong places. Much better to use a shorter arm, and cam, to get the necessary force with more targeted application.

    I went through all these options when I designed my first PDBs years ago. Went through the whole spectrum of impact wrench style (hated it so much, I ripped it off and threw it away after about a month), Belleville style, with levers, cams, big cylinders, hydraulics, you name it, I did it. That's how I ended up with my first electric PDB, using a NEMA gearbox and stepper motor. Basically a software-controlled electric torque wrench. It was downright trivial to build, compared to the others, and worked flawlessly from first power-on. That, and the serious space constraints above the spindle on the Torus Pro, led me to develop the current DC motor design, which is better still, and far more compact, and flexible, than any other solution I've ever seen. And, whether stepper or DC motor, they handle R8 tools just as easily as TTS tools, and have none of the headaches of Belleville springs. The only, insignificant, disadvantage is it takes about 1-2 seconds to grab or release the tool. With the stepper design, it can all be easily controlled by a simple Mach3 macro - about a page of very simple code. You should really consider the stepper/gearbox approach - it's dead-simple, dead-reliable, and let's you control the drawbar tension without making any changes to the hardware, with enough torque on-tap to even strip the drawbar if you get carried away (my stepper PDB was capable of about 70-75 ft-lbs, my DC motor PDBs at least 30-35 ft-lbs). Since I built my first stepper PDB years ago, I have never, not even once, experienced TTS pullout, even when running my 1.5HP spindle at full load for hours on end.

    Regards,
    Ray L.

  12. #12
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    Re: TTS - Spring Pressure ?

    Adding a stepper or servo is no big deal either. I've got lots of fractional horsepower DC brush motors laying around and a few spare steppers. I am certainly curios about what you did there. Controlling the motor is of course no big deal, but I don't have a mental picture of how you are using it to secure/release your tool holders.
    Bob La Londe
    http://www.YumaBassMan.com

  13. #13
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    Re: TTS - Spring Pressure ?

    It's a threaded draw bar. You know....like the old Brigeports.

  14. #14
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    Re: TTS - Spring Pressure ?

    Quote Originally Posted by Bob La Londe View Post
    Adding a stepper or servo is no big deal either. I've got lots of fractional horsepower DC brush motors laying around and a few spare steppers. I am certainly curios about what you did there. Controlling the motor is of course no big deal, but I don't have a mental picture of how you are using it to secure/release your tool holders.
    Bob,

    Like I said, it's effectively an electric torque wrench, turning the stock drawbar. Control current to control torque.

    Regards,
    Ray L.

  15. #15
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    Re: TTS - Spring Pressure ?

    Quote Originally Posted by SCzEngrgGroup View Post
    Bob,

    Like I said, it's effectively an electric torque wrench, turning the stock drawbar. Control current to control torque.

    Regards,
    Ray L.
    That's what I was afraid you were saying. So, how do you go about engaging and disengaging it then? The same way as the butterfly impact? By sliding it up and down to the nut? Yuck. Also, if you are effectively just running an electric wrench how are you locking the spindle? I must be missing something there.
    Bob La Londe
    http://www.YumaBassMan.com

  16. #16
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    Re: TTS - Spring Pressure ?

    Quote Originally Posted by G59 View Post
    It's a threaded draw bar. You know....like the old Brigeports.
    Um, Ok. I got that. LOL. I'm running a master holder right now, but I'ld like something that is faster and doesn't stick down as far. I had to turn that draw bar to put the master holder in. LOL. Actually I had to "fix the draw bar" because the pinned head twisted off the first time I used it. Previously it had a different type of quick change tool draw bar in it I didn't like. Since I hope to be ripping out all the gears and installing one of David's belt drives soon I figured I'ld start planning for a better quick change setup at the same time.

    Anyway, an electric wrench doesn't sound all that convenient to me. Still have to engage and disengage, and it seems you would need to operate a spindle lock as well. The master holder I am using now isn't much less convenient than that sounds.
    Bob La Londe
    http://www.YumaBassMan.com

  17. #17
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    Re: TTS - Spring Pressure ?

    Seems to me that there must be at least a few videos on YouTube demonstrating Ray's PDB. It's a product he sells, at least through Novakon, so it doesn't seem fair to ask for design details though that's his call, not mine.

    Mike

  18. #18
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    Re: TTS - Spring Pressure ?

    I'll look on YouTube. Didn't know he sold it. It does explain some things though. Woulda been nice to know so I could evaluate it. So far I have not found a quick change setup I like that fits this particular mill.
    Bob La Londe
    http://www.YumaBassMan.com

  19. #19
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    Re: TTS - Spring Pressure ?

    Stepper Motor Power Drawbar - YouTube

    LOL. I gotta admit I didn't expect that exactly. I got it. In general though that's what I thought he was doing. I just couldn't believe it until I actually saw it. The pneumatic engage was what I didn't expect. Seems overly complex. Seems there is puh-lenty of room for a big air piston though on the top of that mill. Just make it two stage and go straight up. Anyway, if the stepper draw bar works then it works. I don't think I'll go that way now that I have seen it. It does give me an idea for a way to actuate a spindle lock on my Hurco mill without sacrificing travel though.

    This one on a Bridgeport really shows the principal.

    SAM_0071 - YouTube
    Bob La Londe
    http://www.YumaBassMan.com

  20. #20
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    Re: TTS - Spring Pressure ?

    "The pneumatic engage was what I didn't expect. Seems overly complex." - You have a simpler, more reliable way of engaging a socket with the drawbar? If so, do tell.

    It's really not at all complex, and it works extremely well. It takes up FAR less room, and costs less, than a big multi-stage air cylinder. There's nothing to adjust, ever. It gives full use of TTS or R8 tools, both using the PDB, no wrenches. The whole thing is relatively low-stress, since it doesn't have to deal with pushing around over 4000# of springs, so no weaar, no hardened components (other than the off-the-shelf socket). And it never, never, EVER experiences "pull-out". Small price for the "complexity", IMHO. The only advantage the big air cylinder has is it's a bit faster - 1/2 second vs. 1-1/2 seconds.

    Those two videos are ancient history. The first was the very first, and only, stepper PDB I built for my knee mill, using parts from my junk box. It was built in an afternoon, and worked perfectly until I retired the machine. It used the stock spindle brake to lock the spindle, operated by a 9/16" pneumatic cylinder, when the PDB was operating. The second is the very first prototype of the Novakon PDB, from almost two years ago. It uses a DC motor, and the spindle lock is integrated into the PDB itself. The "production" version is about as compact, and simple, as it can be, and works flawlessly. Only a 2" x 4" "footprint". It also integrates extensive safety interlocks, so it is virtually impossible for the PDB to engage when the spindle is turning, powered or not. And it provides true spindle RPM readout, and spindle power readout, through its head-mounted control panel.

    Attachment 267236 Attachment 267238

    Regards,
    Ray L.

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