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  1. #11
    Stand the machine vertical

  2. #12
    Quote Originally Posted by EddyCurrent View Post
    Stand the machine vertical
    Nah couldn't handle that either. . Lol. . . . . . But on it's side at 15deg angle would maybe work.? . . . . And I'm being serious.!!

  3. #13
    I'll try it tomorrow :) Will nip wickes see if they have any springs.

  4. #14
    Springs will change their 'pull' depending upon how far they are stretched whereas a counter weight over a pulley would be constant at any Z position. If the weight was dangled inside a tube, that would prevent it flapping about.
    Last edited by EddyCurrent; 12-01-2014 at 07:53 PM.

  5. #15
    Whichever way you tilt the machine, you're just going to transfer a component of the gravitational force on the Z-axis to one or more axes. If either X or Y uses a ballscrew, then you could re-orientate the machine to place the force on that axis, however that could cause problems if the stiffness of the machine frame in general is low, which seems likely.

    Quote Originally Posted by JAZZCNC View Post
    Nah couldn't handle that either. . Lol. . . . . . But on it's side at 15deg angle would maybe work.? . . . . And I'm being serious.!!
    If an axis is placed 15 degrees to vertical, the gravitational force will only be cos(15) times less (i.e. 3%) than if the axis was vertical. However I think by 'on it's side' you mean have Z 15 to horizontal and Y 15 from vertical? In which case you've just transferred almost 97% of the Z-axis weight to the Y-axis nut...

    Quote Originally Posted by GEOFFREY View Post
    As a very quick cheap short term fix you could try rigging a "bungee". G.
    Yes, a bungee cord attached to the ceiling would be nice and easy - assuming the machine is fixed to the bench!

    Quote Originally Posted by EddyCurrent View Post
    Springs will change their 'pull' depending upon how far they are stretched whereas a counter weight over a pulley would be constant at any Z position. If the weight was dangled inside a tube, that would prevent it flapping about.
    Whilst it does give an even force, the annoying thing with that approach is you're adding even more mass (about 5kg to cancel the new spindle) to the gantry [Edit: Not thinking.. this doesn't apply as you can attach the pulley to a stationary point, i.e. bench the machine is upon], so the X and Y axes are going to wear out even faster. You could start cascading pulleys to reduce the mass, but that introduces other problems...
    Last edited by Jonathan; 12-01-2014 at 08:38 PM.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  6. #16
    Delete please..
    Last edited by Jonathan; 12-01-2014 at 08:27 PM.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  7. #17
    Quote Originally Posted by EddyCurrent View Post
    Springs will change their 'pull' depending upon how far they are stretched whereas a counter weight over a pulley would be constant at any Z position. If the weight was dangled inside a tube, that would prevent it flapping about.
    One of the snags with counter weights is their mass, OK when static but any accelerating movements increase the forces required to move the spindle which may be counter productive.

    I use gas struts which are more or less constant force with low mass. Can be a bit tricky finding the correct one, but there are adjustable ones which you can use, you start out with too high a force and let fluid out to get what is required.

  8. #18
    I would have thought gas struts would introduce too much damping to rapid movement ? unless there are different types.

  9. #19
    Yes there are different types, damped ones are used on things like doors or boot/bonnet lids, fast moving ones are available, depends on the design of the piston and the oil charge. As an example very fast ones are used to drive the piston in an air gun.

  10. #20
    Just thought I would update you. I put on a couple of springs and its seems much, much happier now, hopefully it will survive a little longer :) Thanks for the help!

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