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  1. #1
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    Jul 2018
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    5

    Hydraulic PDB?

    Hey folks. Ive been doing more and more research as I keep having issues with this 1100M of mine, regarding tool pull out

    I dont think I'm running it too hard..

    .52 LOC
    .035 WOC/stepover
    35IPM
    4700RPM

    Using a 3/8 dia 4 flute Carbide roughing endmill (from lakeshore carbide), roughly .0017 chip/tooth.

    In 1018 material

    I've changed the R8 collet, I've got the bellvilles as tight as they can go while using the OEM PDB, I dykem'd the TTS shank (and it came out almost with nearly no blue on it after the tool started pulling), I took everything apart, cleaned and re-antisiezed it. I tried torquing the washers, but the PDB wouldnt release the tool when set to 25lbs.

    Using an 8 stack of bellvilles, in ()()()() configuration, low side air pressure is 125 (and thats what the regualtor is set to - so there is always consistent air pressure).

    I'm at wits-end with this, I cant leave the machine alone in fear of it pulling out, I feel like everyone else is getting good MRR with their machines (I saw a post with a user saying he was running .6DOC, .1WOC @80IPM and 3800RPM), and mine is just a dud as nothing seems to work right without some type of modification (my atc wouldnt line up until I dremel'd holes and sheetmetal for example).

    For Reference, the machine is an 1100M, with an ATC and PDB. Machine has been making chips for 6 months.

    So now with all that said, I was thinking of increasing clamping pressure by using a better PDB setup. My searching brought me to a few sites, one being blocked unless you have an account and the other is here, and the poster wouldnt post the setup because he wanted to sell it. Unfortunately, that thread was from 2011 and has been dead since lol.

    Has anyone done this? My air/hydraulic experience is limited to porta-powers, where would I go to look for a setup like this? Or even parts? When I start googling air over hydraulic pumps, all i'm getting are porta-powers/enerpacs.

    Thank in advanced!

  2. #2
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    Nov 2012
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    313

    Re: Hydraulic PDB?

    How much chatter do you have in the setup? .035 DOC seems thin enough, and 35 IPM doesn't seem overly aggressive for a 4flute with chip thinning.
    I wonder if a higher IPM would actually make it better? More aggressive feeds tend to improve chatter, right up until you load the tool and break it :-D

  3. #3
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    Aug 2016
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    87

    Re: Hydraulic PDB?

    Before looking at hydraulics, why not add a pressure intensifier to the PDB? SMC makes one that boosts 4x that is around $250.

  4. #4

    Re: Hydraulic PDB?

    The drawbar is tensioned by the spring washers, not air pressure. The air cylinder is used to release the tool not grab it.

    It sounds like you have weak spring washers or incorrect adjustment. I'm assuming you did not get any anti seize inside the collet, that could cause pullout problems also.
    Jim Dawson
    Sandy, Oregon, USA

  5. #5
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    Jul 2018
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    5

    Re: Hydraulic PDB?

    I've had some serious pullout as well, I'm down to .03 stepover, 30IPM, and .52 DOC, so far these settings havent pulled on me. Whether or not this will last, we will see. I wanted to add another stack of bellvilles and increase PDB pressure, but I'm giving up on this. I need something more reliable, this down time has costed me thousands in lost work and broken end mills.

    If anyone wants a fully loaded 1100M, mine will be for sale as soon as the Haas is on order lol


    Quote Originally Posted by Jim Dawson View Post
    The drawbar is tensioned by the spring washers, not air pressure. The air cylinder is used to release the tool not grab it.

    It sounds like you have weak spring washers or incorrect adjustment. I'm assuming you did not get any anti seize inside the collet, that could cause pullout problems also.
    I had anti seized the taper portion, on the surface that rides on the taper. It pulled out, so after a call with Tormach they recommended to not run any anti seize at all, citing hydraulic vibrations. Worked for a little bit, but then I had pull out on a finishing tool after watching the end mill "bounce" off the side of the part... on a .02 sidemill finishing pass.

    Quote Originally Posted by footpetaljones View Post
    Before looking at hydraulics, why not add a pressure intensifier to the PDB? SMC makes one that boosts 4x that is around $250.
    I did not know this existed, thanks!

    Quote Originally Posted by jwatte View Post
    How much chatter do you have in the setup? .035 DOC seems thin enough, and 35 IPM doesn't seem overly aggressive for a 4flute with chip thinning.
    I wonder if a higher IPM would actually make it better? More aggressive feeds tend to improve chatter, right up until you load the tool and break it :-D
    No chatter, the end mill hums right along

  6. #6
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    Re: Hydraulic PDB?

    That sounds almost like the "loose Z gibs chatter" thing that someone else suffered from, and was hard to diagnose, because it seems like X/Y chatter, but it's caused by the Z gibs.
    If you push/pull the spindle head, can you move it at all in any direction sideways? If so, try tightening the gibs and try again ...

  7. #7
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    Re: Hydraulic PDB?

    I agree with the comments regarding adjustment of Z gibs, etc.

    I use the All-Power 3 flute standard length 3/8" carbide end mill generally at .095 WOC, .500 DOC, 4000 RPM and 65-90 IPM depending on what I'm doing. This is with the PDB set somewhat loose as that's what the ATC requires.

    It's worth noting that at shallower DOC's I sometimes experience pullout. I believe this has to do with harmonics/chatter introduced by the helix of the flutes on the selected end mill.

    I have always had poor results with 4 flute cutters in aluminum.

    WW

  8. #8
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    Re: Hydraulic PDB?

    Quote Originally Posted by footpetaljones View Post
    Before looking at hydraulics, why not add a pressure intensifier to the PDB? SMC makes one that boosts 4x that is around $250.
    I haven't seen those before, they look pretty neat! I would be really careful doing this though. Most of the pneumatic actuators I've seen are only rated to 150 or 200 PSI.

  9. #9
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    7087

    Re: Hydraulic PDB?

    Quote Originally Posted by burbingus View Post
    I haven't seen those before, they look pretty neat! I would be really careful doing this though. Most of the pneumatic actuators I've seen are only rated to 150 or 200 PSI.
    NONE of the penumatic components in the Tormach PDB are rated for more than 125PSI. Boosting pressure beyond that level is DANGEROUS! If you want to eliminate pull-out, design either a hydraulic PDB using MUCH stiffer Belleville springs, or a motor-driven PDB that eliminates the Belleville springs entirely. In either case, make sure the effective drawbar tension ends up at least >=3500 pounds, and you will NEVER experience pull-out.

    Regards,
    Ray L.

  10. #10
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    May 2016
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    176

    Re: Hydraulic PDB?

    Do a search on Aliexpress for "CNC air cylinder BT30". Looks like somebody is selling an air over hydraulic PDB for not much money.

    Since it's for a BT30 spindle it'll have more throw than you need for the TTS, and they offer models up to 6 tons (!).

    I believe the Tormach spring pack is made up of single opposing springs like ()()(). You'll want to up the pressure without changing stroke by adding springs like this - ((()))((()))((())). Go to Key Bellevilles and download their spring calculator and work up a stack package that gets you up to the 3500lbs Ray suggested. Be prepared to make a new drawbar as the spring pack will certainly be longer and you'll need to preload the springs of course. Final drawbar length isn't crucial as long as you're engaging most of the collet threads.

    No clue how fast these things are, so might want to research how the Tormach senses (if at all) the tool is released. Maybe need to add some delay to the tool change sequence if the air over oil is significantly slower than the OEM 3-stage cylinder.

    Don't forget to lube the springs, and polishing the spring contact points will also help get closer to advertised drawbar tension. You'd be amazed at how much spring pressure is eaten up by spring to spring friction.

    Or just buy a BT30 spindle and shoehorn it in there...


  11. #11
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    Mar 2009
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    1872

    Re: Hydraulic PDB?

    I have all but eliminated cutter pull out on my 1100 Series II machine.

    When Matt Deopers worked at Tormach he suggested I tighten the collet to when I step on the pedal for the power draw bar, it allows just barely enough collet movement to allow my TTS holder to be released.

    I did that and the only time I get cutter pull out now is when I get a little too aggressive with my cutting.

    After 7 1/2 years I have a pretty good idea what this machine can and can’t do.
    You can buy GOOD PARTS or you can buy CHEAP PARTS, but you can't buy GOOD CHEAP PARTS.

  12. #12
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    Re: Hydraulic PDB?

    Quote Originally Posted by Steve Seebold View Post
    I have all but eliminated cutter pull out on my 1100 Series II machine.

    When Matt Deopers worked at Tormach he suggested I tighten the collet to when I step on the pedal for the power draw bar, it allows just barely enough collet movement to allow my TTS holder to be released.

    I did that and the only time I get cutter pull out now is when I get a little too aggressive with my cutting.

    After 7 1/2 years I have a pretty good idea what this machine can and can’t do.
    Soooo.... Basically, "I have eliminated pull-out by never making any cuts that would result in pull-out". That's really not much of a solution. The only time ANYONE gets pull-out is when they "get a little too aggressive". You COULD make more aggressive cuts, if the PDB provided drawbar tension commensurate with the maximum capability of the rest of the machine.

    The real problem is that, with the Tormach PDB, the "pull-out threshold" of the PDB is well below the maximum capability of the rest of the machine. Contrary to popular belief, this is NOT a limitation of TTS. It is a limitation of the Tormach PDB, NOT TTS, and NOT the rest of the machine.

    Regards,
    Ray L.

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