Pneumatic cylinder on a 4th axis questions
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  1. #1
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    Default Pneumatic cylinder on a 4th axis questions

    I need to use a miteebite id expand clamp that's centered om a fixture mounted to a Haas rotary table.

    Ideally I'd like to use a bima thin pneumatic air cylinder to push and pull the bolt.

    Can these cylinders take positional rotation movement or am I going to have to come up with some kind of rotary union or other method?

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    For most typical pneumatic cylinders, you can buy rear pivot mounts.
    Also, you can buy round body cylinders with a hole in the rear mount that you can use as a pivot.
    Do a search in Mcmaster Carr for round body air cylinder and you'll see some options.

    btm

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    I know the cylinder I want to use. Just need to know if it can support turning the shaft on a 4th axis.[

    ATTACH=CONFIG]263423[/ATTACH]

    I want to mount this to the back of the 4th axis device with a threaded rod going up to my fixture that had an Id expand clamp in the center.

    img_20190818_165010.jpgimg_20190818_165010.jpg

    This is the quicky fixture that was made for the sample parts. I'm just trying to automate the miteebite Id clamp/unclamp
    Attached Thumbnails Attached Thumbnails flat1a-metric.jpg  

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    My gut says yes for limited, low speed use, but then my gut says yes to large quantities of pie. Clearly can't be trusted...

    Instead of setting up a rotary air joint, you could go the other way and set up a taper roller bearing at the rod end, with a "over sleeve" that takes you to acting on the miteebite. I've done such things when needed, and while a little more work, is reasonably reliable as long as you account for chip protection.

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    Have any photos?

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    For a run of a few thousand pieces, should be ok. I would have a spare cylinder on hand though as it may develop internal blowby as the seals wear.

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    What do I need to do for say 20,000 pieces. Rig a dual passage rotary union??

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    Can you limit the rotary table Wind up?
    That would solve your problem.

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    I can and had thought about that. I'm on the hunt for an inexpensive 2 passage rotary union

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    Quote Originally Posted by as9100d View Post
    I need to use a miteebite id expand clamp that's centered om a fixture mounted to a Haas rotary table.

    Ideally I'd like to use a bima thin pneumatic air cylinder to push and pull the bolt.

    Can these cylinders take positional rotation movement or am I going to have to come up with some kind of rotary union or other method?
    Find and old Hardinge AHC collet closer( or somethign like that) and modify it. it should work just fine.

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    Quote Originally Posted by as9100d View Post
    Have any photos?
    Last time I did this was a while ago, and unfortunately there's no pics of it.

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    Overthinking it.

    Spin the cylinder, spin the connector, take up the rotation in the air line. A couple feet of 1/4" polyurethane tubing won't even notice one rotation.

    Be careful not to wrap up when programming.

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    Manually actuated screws generate a lot of force even at low torque. For example, a 3/8" screw at 40 ft lbs generates 6400 lbs of axial force.

    Bolt Torque, Axial Clamp Force, Bolt Diameter Calculator | Engineers Edge| www.engineersedge.com

    The calculator is imperfect, because coefficient of friction varies a lot (difficult to estimate), and it doesn't take thread pitch into account, nor the grade of screw, but it's at least within the ballpark.

    Even a big 4" ID, 5.25" OD pancake air cylinder @ 150 psi only generates 1886 lbs of force. I think for your application, you're going to want to go hydraulic:

    Vektek: Products: Hydraulic

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    Expanding bore clamps typically use a shallow taper - as such the clamping force is a multiple of drawbar force . . . If you don’t want to be concerned with wind up or chafing of your lines, we use Deublin Rotary unions in applications like this.

    Idev Listing | Deublin Company

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    Quote Originally Posted by Comatose View Post
    Overthinking it.

    Spin the cylinder, spin the connector, take up the rotation in the air line. A couple feet of 1/4" polyurethane tubing won't even notice one rotation.

    Be careful not to wrap up when programming.
    I had thought to go hydraulic however the parts are hdpe/ACETAL so clamping forces are lower.

    What are your thoughts of I'd clamping with plastics.

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    Quote Originally Posted by as9100d View Post
    I need to use a miteebite id expand clamp that's centered om a fixture mounted to a Haas rotary table.

    Ideally I'd like to use a bima thin pneumatic air cylinder to push and pull the bolt.

    Can these cylinders take positional rotation movement or am I going to have to come up with some kind of rotary union or other method?
    I use these same cylinders as a "tailstock" to hold (push)injection molded parts on a 4th. IME the cylinder can handle indexing without much issue. We've replaced 1 or 2 since 2017, but that has to do with the small plastic chips getting inside and fucking up the seals. That's thousands and thousands of indexes, 2 shifts, 5 days a week. Pop them open and grease them up and they're good to go again!
    capture.jpg

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    Quote Originally Posted by DFrench View Post
    I use these same cylinders as a "tailstock" to hold (push)injection molded parts on a 4th. IME the cylinder can handle indexing without much issue. We've replaced 1 or 2 since 2017, but that has to do with the small plastic chips getting inside and fucking up the seals. That's thousands and thousands of indexes, 2 shifts, 5 days a week. Pop them open and grease them up and they're good to go again!
    capture.jpg
    Perfect. That will work better than an I'd expand clamp anyways!!

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    Alrighty. This is what I've come up with so far.



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    That looks like a clean way to do it- I might try adding a live center to something like that for a tailstock on our little chucker lathe. We had a similar issue when we needed a power chuck in a Kitagawa indexer for gripping on some dovetailed parts in pie jaws. Ended up using a 3-1/4" bore cylinder from McMaster. Tapped 10-32 4x in the back of the indexer to hold the cylinder and let it spin the airlines as others have mentioned. Only needed +/- 180 but the lines could have taken a few wraps no problem. We calc'd ~2600 lb clamping between chuck jaws at 100 psi and it wasn't quite enough for heavy drilling so added a VBA10A-F02 air intensifier from SMC and ran at 150 psi which worked well. See pic.20191004_160139.jpg

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    What kind of chuck is that?


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