1. #1
    If I use 2m+ long ballscrew with 15mm Hiwin's 2 carriages supporting the ballnut will I be able to spin the screw faster without whipping? Rotating ballnut seems unfeasable and expensive so need a way to get speed and accuracy am toying R&P but would be better if I could use a ballscrew of course.
    Last edited by Desertboy; 25-01-2018 at 01:12 PM.
    http://www.mycncuk.com/threads/10880...60cm-work-area My first CNC build WIP 120cm*80cm

    If you didn't buy it from China the company you bought it from did ;)

  2. #2
    Quote Originally Posted by Desertboy View Post
    If I use 2m+ long ballscrew with 15mm Hiwin's 2 carriages supporting the ballnut will I be able to spin the screw faster without whipping? Rotating ballnut seems unfeasable and expensive so need a way to get speed and accuracy am toying R&P but would be better if I could use a ballscrew of course.
    You haven't stated size of ballscrew so not easy to say. However supporting the ballscrew with linear rails is going to get expensive quickly and require lot messing about.
    There are ways around this thou. Use ballscrew with higher pitch and put ratio on it. This will lower the screw speed but still give desired speed.

    IE: 20mm pitch with 2:1 ratio will give 10mtr/min @500rpm where 10mm pitch at 1:1 would give same 10mtr/min but screw would be spinning at 1000rpm.
    This approach also gives the advantage that torque is aprox doubled so less chance of stalling motors.

    This machine use the same method with 25mm 25mm pitch screws 3000mm long. As you can see in this video around min 1:50 there's no whip at all and it's doing 15mtr/min at some points.
    https://www.youtube.com/watch?v=4STVbn_EMoc
    Last edited by JAZZCNC; 25-01-2018 at 05:21 PM.

  3. The Following User Says Thank You to JAZZCNC For This Useful Post:


  4. #3
    Unsure how long I want to do go, at least 1.8m travel but I was looking at 2700mm ballscrew and Hiwin's last night.

    Amazing work on that cnc machine, given me a lot to think about.
    http://www.mycncuk.com/threads/10880...60cm-work-area My first CNC build WIP 120cm*80cm

    If you didn't buy it from China the company you bought it from did ;)

  5. #4
    Adding a guide with the mass and damping at the right place to stop whip, if not implemented with the same primary slides as the axis, does not need rails with the same accuracy ;-)
    You think that's too expensive? You're not a Model Engineer are you? :D

  6. #5
    I was thinking these
    https://www.ebay.co.uk/itm/15mm-line...cAAOSwNWxaJP-~

    I could butt 2 together to get lengths I desire so 240 would support 2 3m lengths.

    The choices so far
    1. 2* 2525 ballscrew 2.7m with decent quality BK/BF fittings ~1000
    2. 2* 3232 2.5m with fittings ~1500
    3. 2* 2010 with fittings 2.7m length fully supported with the clone rail and 2 carriages per ballnut leaving me 4 spare carriages in total, I could then use 6 carriages to support the Z axis which has the same rail on it given me 50% more strength without affecting travel. ~600

    I would think the 2 biggest factors in critical speed are how straight is the ballscrew and how good are the bearings in the BK/BF fittings, I might even play with type C mounting method but I believe this needs super precision although doubling your criticial speeds.

    Resolution is not so relevant as I'll use servos, not sure how powerful but was told 400w should be ok I think 2k will buy the servos and the mesa controller so I can use linuxcnc.

    I really want to direct drive with oldham coupling but it can be belt driven I suppose, the most important things are large travel, good accuracy and good speed.
    Last edited by Desertboy; 27-01-2018 at 10:14 AM.
    http://www.mycncuk.com/threads/10880...60cm-work-area My first CNC build WIP 120cm*80cm

    If you didn't buy it from China the company you bought it from did ;)

  7. #6
    I think I need an experiment to test the validatity of supporting the ballscrew. The rail I'll have 1.4m 1605 ballscrew I can use with BK fittings have the carriages need a 1.5m length of rail hmm I might just buy another set of 15mm after all they can used for something interesting (Thinking CO2 laser cutter) and 120 is a bargain.

    I have this clone rail on my gantry at moment and original Hiwin's on my Y axis I honestly cannot tell the difference between them except for the Hiwin's being like 4 times the price lol.

    How fast can a nema spin? I suppose theirs no easy answer to that and going to depend a lot on inductance. Since 2 of the motors I use was recovered from other machines I have no idea of what their inductance or even nm is. I can only guess based on weight and chassis dimensions.

    I'm going to budget 7k for the build I hope I can do it cheaper but I think 7k is realistic if I buy new.
    Last edited by Desertboy; 27-01-2018 at 10:37 AM.
    http://www.mycncuk.com/threads/10880...60cm-work-area My first CNC build WIP 120cm*80cm

    If you didn't buy it from China the company you bought it from did ;)

  8. #7
    Quote Originally Posted by Desertboy View Post
    Resolution is not so relevant as I'll use servos, not sure how powerful but was told 400w should be ok I think 2k will buy the servos and the mesa controller so I can use linuxcnc.

    I really want to direct drive with oldham coupling but it can be belt driven I suppose, the most important things are large travel, good accuracy and good speed.
    You're in Cuckoo land if think direct drive 400w servos are going to spin 2.5mtr long 25mm or 32mm ball screws at high speeds.

    On the rail idea why spend 250 plus on rail system which will be a pain to implement when there are much easier ways to avoid or deal with the whip.
    The best way to deal with the whip is not to have it in the first place. So choose the method and size the components correctly and you won't have the whip.

    Would be better spending 250 on building rotating nut system and take whip out the equation.!

  9. #8
    Quote Originally Posted by JAZZCNC View Post
    You're in Cuckoo land if think direct drive 400w servos are going to spin 2.5mtr long 25mm or 32mm ball screws at high speeds.

    On the rail idea why spend 250 plus on rail system which will be a pain to implement when there are much easier ways to avoid or deal with the whip.
    The best way to deal with the whip is not to have it in the first place. So choose the method and size the components correctly and you won't have the whip.

    Would be better spending 250 on building rotating nut system and take whip out the equation.!
    What size do I need? 1.2kw?

    Rotating nut is considered as well ;) It's just I only vaguely understand how to make it work.
    http://www.mycncuk.com/threads/10880...60cm-work-area My first CNC build WIP 120cm*80cm

    If you didn't buy it from China the company you bought it from did ;)

  10. #9
    Quote Originally Posted by Desertboy View Post
    What size do I need? 1.2kw?
    Impossible to answer without knowing more about the machine and Masses you are trying to move plus what speeds your looking for.

  11. The Following User Says Thank You to JAZZCNC For This Useful Post:


  12. #10
    Quote Originally Posted by JAZZCNC View Post
    Would be better spending 250 on building rotating nut system and take whip out the equation.!
    On that note, I do have 6 partially made rotating nut assemblies left over. I never seem to get round to finishing them, so if DesertBoy is keen then it's a cheapish way forward. I've made the motor mounts and partially made the bearing mounts (bored both bearings and center). Shafts need making. I've got the pulleys in stock. I notice we're both in Leicester...
    Last edited by Jonathan; 04-02-2018 at 06:51 PM.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

Similar Threads

  1. Replies: 0
    Last Post: 29-11-2016, 02:16 PM
  2. NEW MEMBER: Hi,Friend,I'm a B2C seller from China for ballscrew,linear guide,linear shaft etc.
    By yvesleeok in forum New Member Introductions
    Replies: 11
    Last Post: 10-08-2013, 11:15 AM
  3. ballnut housing and floating end ballscrew assembly
    By dsc in forum Lead Screws, Nuts & Supports
    Replies: 12
    Last Post: 12-07-2013, 08:22 AM
  4. Linear rail and ballscrew dimensioning for R/C router
    By CarlNicholasCarlsson in forum Linear & Rotary Motion
    Replies: 0
    Last Post: 24-03-2013, 06:52 PM
  5. Using SBR12 as ballscrew end support
    By Lovre in forum Lead Screws, Nuts & Supports
    Replies: 12
    Last Post: 13-12-2012, 08:52 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •