Denford Triac - Power Drawbar Ideas


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Thread: Denford Triac - Power Drawbar Ideas

  1. #1
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    Default Denford Triac - Power Drawbar Ideas

    Hi Everyone

    I've got an early Denford Triac CNC mill and I'm lusting after a power drawbar for it - but there are some challenges! Later machines were re-designed and had a different head, spindle motor and BT30 spindle. Mine is R8 (I will use TTS tooling)

    The key challenges I've got are -

    The drawbar is extremely close to the spindle motor, so whatever I do cannot be mounted directly above. I am thinking of using some lever/cam arrangement as per Hoss's PBD 3 design.
    I am not a fan of compressed air - I've been looking at 6000N (1348lbs) linear actuators. If I aim for 2000-2500lbs with Belleville washers at the drawbar, then a 2:1 ratio lever should be about right.
    What sort of travel is typically required to remove a tts holder? The actuators I've seen quoted are 5mm/s under full load (20mm/s unloaded) - I am guessing I should be able to release a tool in under 5s with this sort of setup.

    Finally, and possibly my biggest challenge at the moment is how to make a floating design. The drawing below shows the head of my machine. There are two bearings, with a lock nut to preload them, immediately above this is a parallel section of shaft, with a keyway in it and the drive pulley for the spindle, there is then a short stub to the top of the spindle. As I understand to minimise load on the spindle bearings, I need to make a collar to attach to the spindle, which the PBD can pull against. Anybody have any bright ideas? I am struggling to see a way of making a positive fixing and getting past the pulley and keyway setup.

    Denford Triac - Power Drawbar Ideas-triac-head-jpg

    Any thoughts/advice greatly appreciated.

    Thanks

    Dave

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  2. #2
    Registered MikeC8's Avatar
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    Default Re: Denford Triac - Power Drawbar Ideas

    Maybe I am looking at it wrong, but I do not even see room for a stack of bellville washers with that setup.

    Work: Hurco VMX42/VMX50 - Shopsabre 4896 - HSMworks with Solidworks
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    Default Re: Denford Triac - Power Drawbar Ideas

    Quote Originally Posted by MikeC8 View Post
    Maybe I am looking at it wrong, but I do not even see room for a stack of bellville washers with that setup.
    It's very tight!

    The drawing isn't quite representative as the motor is rotated to miss the drawbar bolt, so there is a bit more clearance than shown and you can drop a bar through the top cover to knock the drawbar bolt out. Incidentally, the spindle is so short that the drawbar is just a normal bolt!

    Will try and get a picture on my machine tonight.



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    Default Re: Denford Triac - Power Drawbar Ideas

    Some photos of the space available -

    Denford Triac - Power Drawbar Ideas-wp_20170906_18_26_51_pro-jpg

    Denford Triac - Power Drawbar Ideas-wp_20170906_18_26_56_pro-jpg

    Denford Triac - Power Drawbar Ideas-wp_20170906_18_27_09_pro-jpg



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    Default Re: Denford Triac - Power Drawbar Ideas

    Maybe use an automotive hydraulic throw out bearing assembly?

    A lazy man does it twice.


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Denford Triac - Power Drawbar Ideas
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