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  1. You would need to have the fixed end machining done at both ends and the fixed end machining is were all the money is so it would be more expensive.
    I dont do the machining, this is done at a local engineering company so i would need to get a quote.

    Quote Originally Posted by tribbles View Post
    Yeah, having two fixed ends does improve things - although on my machine it's one fixed (BK), and one floating (BF), and I would guess that's what the standard machining on Gary's ballscrews would provide.

    I suppose you could use BK on both ends, but you'd need to make the ends with a lot of precision (or have a number of different size shims to pad out the end with the screw-thread).

  2. I have customers who uses this method to get faster motion, but normally would use a servo motor and specific gearing that is only for this type of application.
    Unless you get the parts on ebay, it will cost a few hundred just for the gearing.
    Also fixing both ends of the ball screw offer similar results (Within about 25%)
    Quote Originally Posted by Ross77 View Post
    Didnt think of that . Ist the main problem in this case the actual torque needed to spin the screw? Although the extra weight wouldnt be ideal surley it is a lesser evil ? wouldnt it be possilble to also use a smaller screw which would make it cheaper?

    Sorry to hijack your tread :naughty:



    Isnt that all part of the fun.....:heehee:

  3. #43
    Waste of time on something like a router. You fit double thrusts on both ends, adjust to get a preload, and all that happens is the end frames deflect inwards so the screw is still whipping even with double bearings.

    The design has to take this into account.
    Bystronics have realised this on their new range of lasers, they have massive end castings and tension the ball screw to something like 70 tonnes tension [ no typo ] to stop it whipping.

    Mind you they are using twin drives with 15 HP servo motors on each drive :whistling:

    I feel the OP needs to sit down, count his pennies then come up with something that's workable instead of throwing down pie in the sky figures for his first build.

    Why the insane rapids anyway ? The whole idea is to bury the tool and work at feed rate.

    .
    John S -

  4. iim not set on the smaller motors but as i have them now i may as well give them ago the machine does not have to work mega fast! its being made out of aluminium. ill give anything ago (within reason) if it works ok and saves abit of money! if not then ill have to go for some " muchas maracas ". that Z axis you got there gary looks a fair bit of kit what OD and pitch is that ball screw?

  5. This version has a 20mm ball screw with a 5MM lead, but can go up to 25mm diameter with any lead.
    We are also working on a smaller version that uses a 16mm ball screw, so will be a lot smaller, but i wnat to keed the width to keep the ridgidity.
    I only use profiled rail, so no round or supported round rail.
    If you have a more details specification, email it over to me and i can work out what you need.

    Quote Originally Posted by AdCNC View Post
    iim not set on the smaller motors but as i have them now i may as well give them ago the machine does not have to work mega fast! its being made out of aluminium. ill give anything ago (within reason) if it works ok and saves abit of money! if not then ill have to go for some " muchas maracas ". that Z axis you got there gary looks a fair bit of kit what OD and pitch is that ball screw?

  6. Thanks Gary ill have to go over a few things then once ive got all the axis up and running then ill drop you a mail with some photos and details. see what you think!

  7. #47
    If the problem with long ballscrews is whip why not fit traveling intermediate bearings as in travelling steady would only need a bearing in which the ballscrew would slide and then some sliding mechanism to pull the steady back into place when the axis moved to the other end. t least 2 steadies would be needed each side (if double ballscrews) plus space at each end to park the steady.

    Just an idea!

    Peter

  8. You would still have a bit of chatter and vibration and i think the cost of this would also be more than the cost of a larger ball screw.


    Quote Originally Posted by ptjw7uk View Post
    If the problem with long ballscrews is whip why not fit traveling intermediate bearings as in travelling steady would only need a bearing in which the ballscrew would slide and then some sliding mechanism to pull the steady back into place when the axis moved to the other end. t least 2 steadies would be needed each side (if double ballscrews) plus space at each end to park the steady.

    Just an idea!

    Peter

  9. #49
    Quote Originally Posted by ptjw7uk View Post
    If the problem with long ballscrews is whip why not fit traveling intermediate bearings as in travelling steady would only need a bearing in which the ballscrew would slide and then some sliding mechanism to pull the steady back into place when the axis moved to the other end. t least 2 steadies would be needed each side (if double ballscrews) plus space at each end to park the steady.

    Just an idea!

    Peter
    It's only circumventing a bad design.

    .
    John S -

  10. #50
    vre's Avatar
    Lives in Athens, Greece. Last Activity: 03-08-2016 Has been a member for 2-3 years. Has a total post count of 33.
    I want to retrofit a lathe with servo 1.8kw 3000 rpm.
    lathe between center is 1.6m and the leadscrew for z axis is 1.8m diameter 30mm 4TPI
    i will replace the leadscrew with ballscrew.
    What diameter-pitch ballscrew will be optimal for this situation ?
    Also what is better to drive the ballscrew with coupler directly from servo or drive it with pulleys & timing belts ?
    What pulleys & timing twill be strong enough and without backlash ?

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