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IndustryArena Forum > Events, Product Announcements Etc > Polls > Ball screw or Acme lead screws

View Poll Results: Which did you use: Ball screw or Acme screws

Voters
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  • Ball screw

    154 61.35%
  • Acme screws

    97 38.65%
Page 1 of 2 12
Results 1 to 20 of 23
  1. #1
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    Ball screw or Acme lead screws

    Hi

    I`m wondering how many of you have used acme leadscrews instead
    of the usual ballscrew system.

  2. #2
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    Can't afford ball screws. Wish I could
    If you cut it to small you can always nail another piece on the end, but if you cut it to big... then what the hell you gonna do?

    Steven

  3. #3
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    Hello, can someone tell me what is the main difference between ball and acme screw (pro and cons ?).



    Thanks.

  4. #4
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    About Precision Acme Threaded Rods

    For a simple and effective way to convert rotary motion into smooth, precise linear motion, choose precision Acme threaded rods. Although not as mechanically efficient as ball screws (a precision Acme threaded rod system operates at about 30% efficiency, while a ball screw system operates at about 90% or better), it is more economical and ideal for uses involving lower speeds and fewer cycles.

    Precision Acme threads are broader, stronger, and more square than standard V-shaped threads, so they're better suited for load carrying. They have a 2C (self-centering) thread fit and a smooth finish that increases rod life by reducing friction. In addition, the 2C thread fit is tighter and more precise than our general purpose Acme threaded rods (see page 3097), which have a thread fit of 2G (general). Thread fits 2C and 2G are compatible. The lead accuracy (the variation of distance a nut travels in a complete turn) over the length of the rod is 0.009" or better per foot.

    Note: To prevent galling (roughness on the surface of metal caused by friction) in most linear motion applications, we recommend using rods and nuts made of different materials. Both bronze and plastic nuts work well with all of the rod materials we offer.

    Acme Size— The outer diameter of the rod (measured from the crest of one thread to the crest on the other side of the rod) and the number of threads per inch. For example, a rod with an Acme size of 1/2"-8 has a diameter of 1/2" with 8 threads per inch.

    Turns per Inch— For single-start rods, turns per inch equals the number of threads per inch. For multiple-start rods, turns per inch equals the number of threads per inch divided by the number of starts on the rod. To determine threads per inch, place a rule on your rod and count the number of threads in one inch.

    Starts— The number of independent threads on a rod. Single- start rods are most common; multiple-start rods allow the nut to travel faster by moving farther in one turn.

    To determine the number of starts, look at the end of your threaded rod (see diagram). The end of a single-start rod is an offset circle. The end of a two-start rod is shaped like a football. For more than two starts, count the number of corners on the end of the rod.

    About Ball Screws and Ball Nuts

    Ball nuts contain ball bearings that circulate in the groove of the screw, reducing friction between the nut and the screw. The result is precise, stepless positioning control over the full length of the ball screw and the conversion of rotary motion to linear motion more efficiently than Acme precision threaded rods. Load capacities are based on a ball screw and ball nut used together.

    Screw Lead— The distance a load is moved with one revolution of the ball screw. For proper fit, choose ball nuts with the same screw lead and diameter as the ball screw.
    Attached Thumbnails Attached Thumbnails acme1.gif   acme2.gif   ball.gif  
    If you cut it to small you can always nail another piece on the end, but if you cut it to big... then what the hell you gonna do?

    Steven

  5. #5
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    p.s. lets give proper credit where credit it due. Previous post stollen in it's entirity from the mcmaster-carr catalog.
    If you cut it to small you can always nail another piece on the end, but if you cut it to big... then what the hell you gonna do?

    Steven

  6. #6
    I do light production on my machines. Hundreds of parts.

    I won't buy a machine with acme screws again.

    They are too hard to remove the backlash from, and worse, the backlash changes over time. You also get higher speed with the ballscrews.

    -Jeff

  7. #7
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    In my original coversion, I tried to use the acme screws on my mill/drill.
    Wrong move, they quickly wore out the bronze nuts and backlash became unmangeable. Converted to Ballscrews and the backlash went away and had smoother operation.

    Bubba
    Art
    AKA Country Bubba (Older Than Dirt)

  8. #8
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    Back-feeding

    One problem with ballscrews is that due to the very low friction, when using the mill / lathe in manual mode, you have to make sure that the slides are locked. This is because of back-feeding whereby the cutting forces move the slides because the nuts to turn the ballscrews. Because normal i.e. Acme lead screws have much more friction, this is rather less of a problem.

    Almost needless to say, in precision work and especially with heavy cuts, the slides ought probably to be locked.

    Chris

  9. #9
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    totaly,
    That is the EXACT reason you don't need hand wheels on a cnc'd machine.
    I read many threads about the backfeed problem trying to use ballscrews in a manual mode.
    I have found the use of either MDI or continous jog to be the answer and haven't looked back!
    I am in the process of making my lathe cnc and it will NOT have handwheels. There is no need and if I want some quick feed, there is jog in my control software and if I want to be accurate, there is MDI!

    Just my .02

    Bubba
    Art
    AKA Country Bubba (Older Than Dirt)

  10. #10
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    Actually, I find that ball screws are not that expensive unless you go for the super high grade ones. I scores a couple of 84" ones with the nuts for 200 shipped from ebay. Had to grind off some rust, but they're otherwise new. One of them do have a detectable backlash though (if some one have ideas one how to get rid of it, please let me know). In fact, even brand new they are not that expensive. Go to roton.com. I have to get used ones b/c here in colorado springs, no one would mill the ends for me. What does get expensive are the accessories, such as the flange, the block mounts, etc.

  11. #11
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    One thing that was pointed out to me by Gerry, for my application, it would be a real pain in the a to keep the wood dust from fouling the nut. With no coolent and fine dust that gets everywhere (even past the dust collector at times) using a ball screw may be a self defeating thing. A ball screw cover would go a long way in this, but wouldn't be a complete solution.
    If you cut it to small you can always nail another piece on the end, but if you cut it to big... then what the hell you gonna do?

    Steven

  12. #12
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    Any examples pf X2 Mill BallSrew with stepper on left side of bench

    Hi, this newbie is looking for examples of CNC conversions using a ballscrwew on the X-axis and the stepper mounted on the left side of the table. I anticipate one obvious negative from a left-handed motor design. Each time you want to remove the table, you may have to remove the motor. I'm not sure that will be a big nuisance. Just in case, I have not ruled out the what looks like the ubiqutous right-hand mounted stepper approach. I appreciate all the help I can get,
    Wilfred

  13. #13
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    I mounted my servo (not stepper) on the left hand end of the table on my mill/drill because of interference on the right side. Haven't had any problems and as far as the handwheel problem, there hasn't been one as I have no handwheels!

    The left bearing is a plain bearing and sure, there is a little float due to temprature fluctuations, but with a belt drive that is no problem.
    Art
    AKA Country Bubba (Older Than Dirt)

  14. #14
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    Bubba,
    Good to get some positive feedback. I still ahve to do some additional homwork before committing to any one approach. I hope to learn from the initiatives of others, such as you , to get a handle on things. Joining these groups is the smart thing to do and, hopefully will help me, and other's in the same situation, to look before with take a plunge,
    thanks,
    whoafat

  15. #15
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    Wink Video demonstration

    Try to visit this site.There is a video demonstration inside.

    http://www.eurotechelite.com
    http://www.topbarfeed.com

  16. #16
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    acme screw with mach

    Dear All,
    I am little puzzle with acme screw.
    1.)If I buy milling manual machine (acme screw type),I want to change it to be CNC milling machine and I will use DC servo to control of each axis with Mach software,Does it have precision and accuracy same as ball screw method?
    2.) If I use it very a long time,It will have precision and accuracy same as original or not.


    Cheers,
    Mongkol
    Attached Thumbnails Attached Thumbnails CNCanim.gif  

  17. #17
    Community Moderator ger21's Avatar
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    That depends. Acme screws are available in different grades of precision. With a lot of use, yes, it will probably wear eventually.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

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

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

  18. #18
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    A high end acme screw has a greater capacity for accuracy than a high end ballscrew. Ballscrews are limited in accuracy by several factors, but this doesn't matter to all but the most accurate machines. Certainly not to your average milling machine or lathe.

    For any reasonably priced screw, a ballscrew is the way to go for practical accuracy. They can be placed in a sealed bellows to mitigate abrasive wear, and if you've got the money, are backlash free. This is the way to go for a CNC mill or lathe.

  19. #19
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    Quote Originally Posted by Mongkol View Post
    Dear All,
    I am little puzzle with acme screw.
    1.)If I buy milling manual machine (acme screw type),I want to change it to be CNC milling machine and I will use DC servo to control of each axis with Mach software,Does it have precision and accuracy same as ball screw method?
    2.) If I use it very a long time,It will have precision and accuracy same as original or not.


    Cheers,
    Mongkol
    My machine had "good as new" acme leadscrews when I got it....converted to CNC and the nuts wore out in 2 weeks.....gave the leadscrews away to a fellow member here.
    Keith

  20. #20
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    I completely agree with that. I was able to "walk" the acme nut down the screw after a couple of months with out turning the screw.!

    There is a lot more friction in the acme screw and who knows what the specs on the material are?

    Initially the accuracy and precision will be the same, but will quickly deteriorate!

    Do yourself a favor and covert to hardened ball screws as quickly as possible.
    Art
    AKA Country Bubba (Older Than Dirt)

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