Welcome to Our Community

Some features disabled for guests. Register Today.

C Beam Expanded

Discussion in 'CNC Mills/Routers' started by Steve Welsh, Jun 1, 2016.

  1. Steve Welsh

    Builder

    Joined:
    May 30, 2016
    Messages:
    7
    Likes Received:
    0
    Could I ask if the C beam 1000mm exhibits any significant whip on the lead screw?? If so would the OB store carry a larger size lead screw?

    Thinking of making a C beam expanded in size.

    Thanks,
     
  2. alex_b

    alex_b Veteran
    Staff Member Resident Builder Project Maker Builder

    Joined:
    Jan 31, 2015
    Messages:
    40
    Likes Received:
    83
    I run a 1000mm lead screw on our C-Beam Y-axis build and there is some slight whip but it is manageable. The two things I did to minimize it is to ensure straight alignment of the nut block and the endplates as well as to make sure I did not tighten the locknut against the acme bearings too tightly. 0.5mm makes a difference, so it took a while to get the perfect tension on the lead screw against the endplate.

    I run 2000mm/min rapids currently and the slight whip hasn't caused any noticeable inaccuracy.

    Hope that helps! (Our C-Beam is also expanded in size in the X, more info on our build page)
     
  3. Steve Welsh

    Builder

    Joined:
    May 30, 2016
    Messages:
    7
    Likes Received:
    0
    Thanks Alex
     
  4. boskap

    boskap Journeyman
    Builder

    Joined:
    Jun 23, 2015
    Messages:
    49
    Likes Received:
    3
    Hi
    I have the problem of whiping lead srews
    but my rapid travel speed is 3000mm/min
    but i want to go faster but then the lead screw stucks
    what can i do ? 12mm ACME ?

    did not tighten the locknut against the acme bearings too tightly ?
    when its not thight is then backslash be possible

    thx Peter
     
  5. Moag

    Moag Master
    Staff Member Resident Builder Builder

    Joined:
    Mar 16, 2016
    Messages:
    183
    Likes Received:
    260
    The problem of whipping lead screws over longer lengths doesn't have lead to thicker lead screws. Think of it like a piece of rope, taking it to the extreme. Put it under tension and it is going to be straight, put it in compression and it's going to flop around. A solution that some builders are coming up with is to put the acme lead screw under tension instead of compression. Have a look at this video at around 11.30 mark to see the concept in practice. ;)



    And to make it tight look at this one at about 13.30

     
    #5 Moag, Jun 24, 2016
    Last edited: Jun 24, 2016
    GrayUK likes this.
  6. boskap

    boskap Journeyman
    Builder

    Joined:
    Jun 23, 2015
    Messages:
    49
    Likes Received:
    3
    first and second video:
    OK there ist the lock collar on the other side of the lead srew
    so you can make tension
    but on the orignal c-beam there is it on the inner side
    how i get there tension ?


    second question
    how fast did do you think i go with tensions lead srew
    6000mm/min ?
     
  7. boskap

    boskap Journeyman
    Builder

    Joined:
    Jun 23, 2015
    Messages:
    49
    Likes Received:
    3
    end in the videos are no bearings at the end of the c-beam
    are the not needed ?
     
  8. Moag

    Moag Master
    Staff Member Resident Builder Builder

    Joined:
    Mar 16, 2016
    Messages:
    183
    Likes Received:
    260
    Haven't given it a go @boskap but might do in the future. Is to use the standard C-Beam End Plates with the normal 688Z 8x16x5 bearing in the pocket, but stuck in place with some Loctite. Order of assembly is: Flex Coupling > Thrust Bearing 1 8 X 21 X 2mm AXK0821 Thrust Needle Roller Bearing With TWO Washers Each | eBay > C-Beam End Plate > Glued in 688Z 8x16x5 Bearing > to other end and another Glued in 688Z 8x16x5 Bearing > C-Beam End Plate > Thrust Bearing > Lock Collar. Hope that makes sense, I will try to make a picture when I have more time.
     
  9. Moag

    Moag Master
    Staff Member Resident Builder Builder

    Joined:
    Mar 16, 2016
    Messages:
    183
    Likes Received:
    260
    Have no idea!
     
  10. boskap

    boskap Journeyman
    Builder

    Joined:
    Jun 23, 2015
    Messages:
    49
    Likes Received:
    3
    Hello
    Thx for your Answer
    But my englisch is Not so good
    So ist try to follow you
    Please send me a pic so i can See What you mean
     
  11. boskap

    boskap Journeyman
    Builder

    Joined:
    Jun 23, 2015
    Messages:
    49
    Likes Received:
    3
    And why loctite the bearings in the end plate
     
  12. Moag

    Moag Master
    Staff Member Resident Builder Builder

    Joined:
    Mar 16, 2016
    Messages:
    183
    Likes Received:
    260
    The Loctite is just to stop the bearing from falling out of the pocket in the end plate. So do these pictures help @boskap ?
    Image 24-06-2016 at 8.06 pm.jpg Image 24-06-2016 at 8.05 pm.jpg
     
  13. Moag

    Moag Master
    Staff Member Resident Builder Builder

    Joined:
    Mar 16, 2016
    Messages:
    183
    Likes Received:
    260
    Metalguru and GrayUK like this.
  14. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Builder

    Joined:
    Dec 20, 2013
    Messages:
    1,465
    Likes Received:
    603
    Applying axial tension across regular bearings is not a good idea as it cross-loads the balls and quickly locks them up. Best solution would be to reverse the end plates and install F8-16M axial bearings in the bearing pockets. You may however need to shave a small amount off the length of the C-Beam to have enough room on the screw to attach lock nuts (or collars) and the stepper coupling.

    And note, the budget example bearings provided in the link above may not prove to be a durable solution. Be sure and grease them heavily prior to installation. In the long run you may need to spring for better quality F8-16M bearings.
     
    Moag likes this.
  15. Moag

    Moag Master
    Staff Member Resident Builder Builder

    Joined:
    Mar 16, 2016
    Messages:
    183
    Likes Received:
    260
    Nice bearing Rick, your wealth of knowledge is a great asset mate:thumbsup:
     
    Rick 2.0 likes this.
  16. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Builder

    Joined:
    Dec 20, 2013
    Messages:
    1,465
    Likes Received:
    603
    Thanks, but I've used a lot of these bearings to the point that they have almost become second nature. The current project I'm working on will have 20 sets in it by the time it comes to fruition.
     
    Moag likes this.
  17. Moag

    Moag Master
    Staff Member Resident Builder Builder

    Joined:
    Mar 16, 2016
    Messages:
    183
    Likes Received:
    260
    Can't wait to see it Rick, sounds interesting..)
     
  18. boskap

    boskap Journeyman
    Builder

    Joined:
    Jun 23, 2015
    Messages:
    49
    Likes Received:
    3
    thx rick
    but one question
    is too much tension good because thermal expansion
    all other lead scre have two mounting blocks
    one fix and one (sorry i didnt know the exact word)loosely
     
  19. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Builder

    Joined:
    Dec 20, 2013
    Messages:
    1,465
    Likes Received:
    603
    You're getting a little beyond my experience level with that one. But I think you are overestimating the amount of tension being applied. I think the goal here is to revise the screw anchorages from where they function in compression only to ones that function in tension only as by eliminating compression you have eliminated the main force causing the screw to bow. Snug tight on the tension is really all you need.

    (Note: What is being suggested is just help minimize simple whipping. An understanding of the full extent of whipping caused by imbalances, harmonics, rotational inertia, centrifugal force, etc., etc., etc., is well beyond most forum members including myself. If you really want to get into it, I'm sure there are several Doctoral Theses out there on the subject.)
     
    anigeek65 likes this.
  20. boskap

    boskap Journeyman
    Builder

    Joined:
    Jun 23, 2015
    Messages:
    49
    Likes Received:
    3
    thx
    i have no experience with it
    i only see what you became when you buy a lead screw
    thats why i ask

    i try it and orderd the F8-16M axial bearings

    thx
     

Share This Page

  • About Us

    The OpenBuilds Team is dedicated helping you to Dream it - Build it - Share it! Collaborate on our forums and be sure to visit the Part Store for all your Maker needs.


    [email protected]

  • Like us on Facebook

  • Support Open Source FairShare Program!

    OpenBuilds FairShare Give Back Program provides resources to Open Source projects, developers and schools around the world. Invest in your future by helping others develop their future.

    Donate to Open Source