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  1. #61
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    Hi Nice right up on b screws, but i have a question,
    How do i calculate what torque i need to lift a given weight over a given distance with a Bscrew ( ground ) 5 tpi.

    Any one help?



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    hello to all



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    Registered thkoutsidthebox's Avatar
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    So speaking about starts......

    If I have a single start screw, we'll say 1 TPI, rotating at 600rpm ..... it will travel 600ipm.

    Now if I have a 4 start, same screw details....1 TPI, same speed, will it travel 2400ipm ?

    and slightly off topic:

    Will I need a stepper with 4 times the torque to turn it?



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    1 TPI = 1 Turn Per Inch meaning that for every whole turn nut will be displaced 1inch so ,a 20start 1TPI screw will displace 1inch per turn

    Sorry but i can't hel with the torque needs so when i have to pikk i just make sure i overkill .

    Last edited by ironDigit; 08-17-2008 at 10:54 AM. Reason: spelling so bad the contents were lost
    Finally CHIPS you can have as much as you can without the doc. complainting about your cholesterol.


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    Quote Originally Posted by jrace2718 View Post
    Ok, I'm going to ask a really dumb question that I haven't seen discussed:

    If I get a ballscrew and ballnut of whatever precision, can I take the nut off (I assume the nuts come assembled on the screw)? Do all the bearings just fall out? Can I get them back in or do I take pains to not let the nut get unscrewed all the way in the first place? Can I set the backlash myself or is it set at the factory by the size balls, etc?

    Thanks. I am starting a build and I am deciding between ACME and ballscrews for wood routing.
    can I take the nut off Yes.

    Do all the bearings just fall out? Yes, they do.

    Can I get them back in or do I take pains to not let the nut get unscrewed all the way in the first place? It's not easy to to put the balls back in. I've made a lot of money over the years by people thinking they can just put the balls back in, and tadaaaa! It's best that you try NOT to take the nut off of the screw. You will save time, money and aggravation.

    Can I set the backlash myself or is it set at the factory by the size balls, etc? Is it a split nut (double nut)? If yes, you can set your own backlash. If it's a single nut, no you cannot.

    If you are experiencing excessive backlash, it's a most likely it's a worn ball screw and needs to be re-balled or repaired.

    What is the diameter & length? Is it a precision ground or rolled thread ball screw? Can you provide photos of the nut? There may be an adjustment on it.



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    Very informative thread. Learned a lot about ballscrews here. My question is related to diameter of the ballscrew. If the ballscrew is turning at high rpm it will have a tendency to whip and not remain straight. The answer seems to be to use a larger diameter ballscrew that is more rigid to prevent this. Could you use the smaller diameter ballscrew if you drove the nut rather than the screw? I ask this because the larger screws get very expensive fast compared to the same length of a smaller screw.



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    Registered thkoutsidthebox's Avatar
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    Quote Originally Posted by jho5820705 View Post
    Very informative thread. Learned a lot about ballscrews here. My question is related to diameter of the ballscrew. If the ballscrew is turning at high rpm it will have a tendency to whip and not remain straight. The answer seems to be to use a larger diameter ballscrew that is more rigid to prevent this. Could you use the smaller diameter ballscrew if you drove the nut rather than the screw? I ask this because the larger screws get very expensive fast compared to the same length of a smaller screw.
    I believe the answer is 'Yes', but I'm about as far from expert as your gonna get! I've looked at this, but found it difficult to get suitable nut's for driving from them.



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    Quote Originally Posted by thkoutsidthebox View Post
    I believe the answer is 'Yes', but I'm about as far from expert as your gonna get! I've looked at this, but found it difficult to get suitable nut's for driving from them.
    Driving the nut is nothing new. However, as you've noted, suitable nuts aren't prevalent. Manufacturers typically recommend that the nut be mounted with the ball return guides facing up or sideways (if there are two opposing return guides).

    There are some nuts designed specifically for fixed screws, but they're not cheap.



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    Need help , I recently read an article on replacing the ball bearings . so I thought I would do it to refresh mine , after a close look found the bearing were out of round , replaced them and now cannot get them to stay in after being replaced , this is a dual barrel ballscrew , am I doing something wrong , I did not loose any parts , any help is appreciated.
    Freeflow



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    Is it normal for preloaded rolled ball screws to feel "gritty" or bumpy as they are turned manually?

    I am running Thompson Ball Nut 7820827 and Ball Screw 5707540 (Reid Supply TBS-412TBS-20) with wave washer preload 50-100lb on a RF-30 conversion. The position of the bumps are repeatable to some degree - if the nut is rotated slightly and then returned to the position of the bump. If I give the nut a bit spin and return to the original position of the bump, the size of the bump changes or disappears. Could this have something to do with balls entering or exiting the return tube? or just lining up differently? This is happening on all three axis. Cleaning and lubing each assembly did not help. I am going to try replacing (eBay) the ball bearings next. Any ideas what causes this or fixes?

    -Nick



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    Default ballscrews

    I finally looked real close and found that all the balls are 2 and 1/2 thousanths differant in size , alternate loading untill the canister will not hold any more balls , this took care of the problem for me , I am yet to test for losing steps though , will comment after the test run ,
    Regards
    freeflow



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    Quote Originally Posted by Tony Mitchell View Post
    can I take the nut off Yes.

    Do all the bearings just fall out? Yes, they do.

    Can I get them back in or do I take pains to not let the nut get unscrewed all the way in the first place? It's not easy to to put the balls back in. I've made a lot of money over the years by people thinking they can just put the balls back in, and tadaaaa! It's best that you try NOT to take the nut off of the screw. You will save time, money and aggravation.

    Can I set the backlash myself or is it set at the factory by the size balls, etc? Is it a split nut (double nut)? If yes, you can set your own backlash. If it's a single nut, no you cannot.

    If you are experiencing excessive backlash, it's a most likely it's a worn ball screw and needs to be re-balled or repaired.

    What is the diameter & length? Is it a precision ground or rolled thread ball screw? Can you provide photos of the nut? There may be an adjustment on it.
    Ok, but I relly need to take the nut off in order to machine it. Can someone show me how to take it off correctly?



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    Quote Originally Posted by 15mgtar View Post
    Ok, but I relly need to take the nut off in order to machine it. Can someone show me how to take it off correctly?
    Make a rod or tube that is a bit smaller in diameter than the minor diameter of the ballscrew grooves, and longer than the nut. You can then run the nut off the end and on to the rod.
    If the end of the screw is machined, then you need this to be a tube so the tube can go right up to the end of the threads.

    The rod/tube will keep the balls where they should be and as long as you don't let that come out, you'll be fine. I usually put a zip tie on each end so bumping it doesn't get you in trouble.

    Mike Visit my projects blog at: http://mikeeverman.com/
    http://www.bell-evermannews.com/ http://www.bell-everman.com


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    Default 1x1.5m Machine...what Ballscrews?

    Hi Swede,
    It was nice article..I learned a lot and I have some questions about my machine which I started to build...I already have 3 640 oz-in Keling motors,3 Geckos 203V, 1 KL-6515 power supply and the C11 board...(waiting for the chinese spindle of 2.2kW)

    What I would like to know now is what ballscrew to use?My machine will be 1x1.5m and I 'll mostly cut wood and some cuts of aluminium...I want it to be a bit fast and wonder if 5mm pitch is the right one or should I go to 10mm pitch?If my max motor RPM is 1200, then with the 5mm pitch I'll have 236.22 IPM right? Doubling it to 10mm I ll have 472.44IPM...

    What would you suggest to do?I am quite confused and don't want to waste money..

    Thanks in advance...
    Kostas.



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    Quote Originally Posted by kostas1 View Post
    If my max motor RPM is 1200, then with the 5mm pitch I'll have 236.22 IPM right? Doubling it to 10mm I ll have 472.44IPM...
    It's not that simple. How much torque will you have at 1200rpm? If you want to move at 472ipm, you'll need enough force to accelerate up to that speed. If using Mach3, acceleration is linear, so you'll need the same force at 450ipm as you do at 20ipm, during acceleration. But the torque drops off as rpm's increase.

    My guess would be to go for the 10mm lead.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Get the 10mm, gear down for 5mm resolution if needed.



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    Gerry:thanks for the answer...I don't want to move at 472IPM...I'll be very satisfied with 300IPM also.We talk about rapid speed now and 472IPM is the theoretic speed given the motors' power and ballscrew pitch...

    Phungi:thanks...What do you mean by this?
    Get the 10mm, gear down for 5mm resolution if needed.
    How could I gear down to 5mm if I already bought 10mm?

    Thanks..



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    Quote Originally Posted by kostas1 View Post

    Phungi:thanks...What do you mean by this?


    How could I gear down to 5mm if I already bought 10mm?

    Thanks..
    Use a belt and pulleys to connect it to the motor. If you need more power, put a smaller pulley on the motor. If you need more speed, put a smaller pulley on the screw.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  19. #79
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    Ok, understood...
    So the best way to make it from the beginning is to use this pulley?
    What if I firstly connected the motor directly to ballscrew and some other day decided to also put a pulley?Will it be feasible or I had to change the machine's design?

    Thanks and sorry but I am a beginner...
    Kostas.



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    Adding a belt and pulley or any gearing will reduce the amount of power you will be getting at the load.
    Gearing has losses so if the efficiency of your gearing is 90% then you will loose 10% of the input power to heat.
    While you will increase the torque or speed, the output power will be lower.
    the best way is to directly couple the motor to the ball screw, this reduces the losses and also any backlash or hysteresis that can be associated to gearing.
    You need to make a decision on the actual speeds you need, look at the torque curves of the motor and driver combination and then work out the lead of the screw so to get the optimum amount of power to the load.

    Zapp Automation Ltd
    www.slidesandballscrews.com


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