1. For downloading SimTools plugins you need a Download Package. Get it with virtual coins that you receive for forum activity or Buy Download Package - We have a zero Spam tolerance so read our forum rules first.

    Buy Download Package Now!
  2. Do not try to cheat our system and do not post an unnecessary amount of useless posts only to earn credits here. We have a zero spam tolerance policy and this will cause a ban of your user account. Otherwise we wish you a pleasant stay here! Read the forum rules
  3. We have a few rules which you need to read and accept before posting anything here! Following these rules will keep the forum clean and your stay pleasant here. Do not following these rules will lead to permanent exclusion from this website: Read the forum rules.

Which Ballscrew pitch / Dia / Length ?

Discussion in 'Motor actuators and drivers' started by Gadget999, Oct 27, 2018.

  1. Gadget999

    Gadget999 Active Member

    Joined:
    Dec 27, 2015
    Messages:
    628
    Location:
    London
    Balance:
    4,930Coins
    Ratings:
    +117 / 4 / -0
    My Motion Simulator:
    2DOF, Arduino
  2. Dirty

    Dirty Active Member Gold Contributor

    Joined:
    Oct 15, 2017
    Messages:
    198
    Occupation:
    All the way up front.
    Location:
    Germany
    Balance:
    2,225Coins
    Ratings:
    +185 / 1 / -0
    Yes, :)

    SFU1605 indeed means 16mm diameter and 5mm pitch. I am using those and found them to be quite good for the job. Plenty of other people have used them before with no problems.

    SFU1610 (10mm pitch) are OK as well, if you are looking for actuation speeds over ~400mm/s. But keep in mind you will need enough torque to drive them.

    At RPMs over 4000 min^-1 and a length over ~700 mm, vibrations might become too strong, so you might want to consider a bigger diameter in that case, but for what we are doing here, I strongly doubt that to be necessary!

    I made a small excel sheet for quick drafting. Fill out the orange cells, grey are intermediate results, green are results. Feel free to play around with it. In the end you won't come around actually understanding what you are doing in this hobby :) A great way to learn/grow/get better/ get smarter...

    Enjoy it

    Dirty :D
    • Like Like x 3
    Last edited: Nov 22, 2018
  3. Dirty

    Dirty Active Member Gold Contributor

    Joined:
    Oct 15, 2017
    Messages:
    198
    Occupation:
    All the way up front.
    Location:
    Germany
    Balance:
    2,225Coins
    Ratings:
    +185 / 1 / -0
    My (very personal) rules of thumb:

    1. Let each motor have 3Watts of peak motor power for every KG of "MovingWeight". So, for a 50Kg platform and a 100Kg payload --> use 6 motors with ~450W each. 300W would be a little weak, 800W quite strong.
    2. Use a ball screw with a length ~120mm longer than the travel you want to achieve. I use a 500mm ball screw to achieve ~380mm travel. The rest will be unusable. The bearing block, the ball-nut and the "buffer zones" will occupy those 120mm.
    3. You will need each of your actuators to have a push force [N] of about 6 * MovingWeight[Kg]. So, if you want to move 120Kg (40kg platform + 80Kg payload) you will need each actuator to have 6 * 120 = 720N of push force minimum, if you want even the most unfavourable geometric constellations covered. Those are the ones with the platform all the way down.
    4. You can expect your actuators to have a push force [in N] of about 6300 * Motor-Torque [NM] / Lead[mm]. So a 0,5NM motor on an SFU1605 will give you ~6300*0,5/5 = 630N. Note that the force generated does not depend on the diameter nor the motor power!
    5. 3 & 4 combined means, that you should make sure, that your motor has a Torque[NM] of at least Lead[mm] * MovingWeight[kg] / 1050. So if you want to move 120Kg around (40kg platform + 80Kg payload) with an SFU1605 (5mm Lead), you should have 5 * 120 / 1050 = 0,57NM of motor torque to stay well clear of situations in which your motor might become torque saturated.
    6. You can expect your actuator to reach a max actuation speed [mm/s] of RPM * Lead[mm] /60. So, a motor with a speed of 4000RPM on an SFU1605 will max out at 4000 * 5 / 60 = 333 [mm/s]

    All those rules of thumb are based on the premise that at any point on the "geometric envelope" the platform shall need only 50% of its force to hold the simple static load. That means, that no matter where you put the platform (statically, no motion!) your actuators will need at max 50% of their available force to hold the platform and will always have the other 50% available for acceleration. That means you can have your platform accelerate at 2G over the entire geometric envelope - in all directions!

    Disclaimer:
    While I have spend some brains on those formulae, they might be wrong! Hell,.. there might even be a stupid typo in there somewhere... or two. So please (!!!) don't tear me into pieces if there is. And also please don't rip me apart if there is an actual conceptual error in there.
    That being said, I'd be the first to admit and correct my errors if there are clear and valid arguments against my positions here. I strongly encourage anyone with an engineering degree (@My.stAr help me out, will you?!?) on these forums to carefully check those formulae and the underlying premises for correctness or at least plausibility. I have intentionally kept them simple to be used by absolute beginners and I know, the mathematical notation is not according to any standard.

    I hope I can empower beginners to pick this hobby by robbing them of their reasons of why they think they can't do these sort of things. I was one of them not too long ago!

    Dirty :D
    • Like Like x 4
    • Informative Informative x 4
    • Winner Winner x 2
    Last edited: Nov 26, 2018
  4. Dirty

    Dirty Active Member Gold Contributor

    Joined:
    Oct 15, 2017
    Messages:
    198
    Occupation:
    All the way up front.
    Location:
    Germany
    Balance:
    2,225Coins
    Ratings:
    +185 / 1 / -0
    ups,... and I should probably add that those formulae are meant for a full-on 6DOF Stewart platform. 3DOF or other platforms can get away with a lot less :)
  5. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

    Joined:
    Jul 13, 2014
    Messages:
    12,871
    Occupation:
    Innovative tech specialist for NGOs
    Location:
    St Helens, Tasmania, Australia
    Balance:
    98,260Coins
    Ratings:
    +8,217 / 40 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    Added to FAQs DIY Linear Actuators here: https://www.xsimulator.net/community/faq/diy-linear-actuators.248/
  6. adgun

    adgun Member

    Joined:
    Jan 28, 2008
    Messages:
    358
    Occupation:
    mechanic
    Location:
    Netherlands
    Balance:
    4,491Coins
    Ratings:
    +77 / 3 / -0
    Platform accelerate with 2G must be 1G
  7. apointner

    apointner Siddhartha

    Joined:
    Aug 16, 2014
    Messages:
    64
    Location:
    N 48° 9'0.88" E 12° 5'45.84"
    Balance:
    356Coins
    Ratings:
    +11 / 3 / -0
    My Motion Simulator:
    3DOF, DC motor, Arduino, Motion platform
    Very nice Excel file, indeed!
  8. Gadget999

    Gadget999 Active Member

    Joined:
    Dec 27, 2015
    Messages:
    628
    Location:
    London
    Balance:
    4,930Coins
    Ratings:
    +117 / 4 / -0
    My Motion Simulator:
    2DOF, Arduino
    Some interesting points there

    How would a ballscrew with 1610 and a 1kw dc motor rated at 3500 rpm hold up ?

    Would the mm/s be much faster ?

    Also - is there a way to calc this information for a chain/belt drive actuator ?
  9. iTek

    iTek Tek

    Joined:
    Nov 7, 2018
    Messages:
    6
    Location:
    Sweden
    Balance:
    27Coins
    Ratings:
    +0 / 0 / -0
    Hi
    I am thinking of build a 6DOF motion platform mostly to use with racing sim. I'am going to take much inspiration from Hoddems's liner actuator and of coursers from other to. I'am thinking of to going for sfu2005 600mm ball screw and place the motor on the side using a teeth belt. I belie by doing this I can keep the height down and moderate the speed with the teeth belt pulley to get the right speed. I believe most people use 1605 ball screw but using 2005 i may get some more margins and stability. Is this unnecessary? They cost almost twice as much but compare to the total cost it might be worth it?
  10. Dirty

    Dirty Active Member Gold Contributor

    Joined:
    Oct 15, 2017
    Messages:
    198
    Occupation:
    All the way up front.
    Location:
    Germany
    Balance:
    2,225Coins
    Ratings:
    +185 / 1 / -0
    That looks like a pretty sensible design to me :)

    Your motor will have a torque of 2,7Nm
    Bildschirmfoto 2019-02-21 um 22.15.57.png

    Your ballscrew will give you a transmission ratio of ~5 ( 5N of axial force for every N of tangential force applied at the 8mm radius)
    Bildschirmfoto 2019-02-21 um 22.16.09.png

    Your actuator will reach an axial Speed of 580mm/s and almost 1700N of axial force.
    Bildschirmfoto 2019-02-21 um 22.16.20.png

    Your platform...
    (I estimated the weight and geometry!)
    Bildschirmfoto 2019-02-21 um 22.16.34.png

    ...shall be able to accelerate at 2G.
    Bildschirmfoto 2019-02-21 um 22.16.52.png

    ...which it does! Easily!!!
    Bildschirmfoto 2019-02-21 um 22.17.02.png

    I wouldn't know why not to use those ballscrews & motors.

    Dirty :D

    btw. "WAHR" means "TRUE" in German :)
    • Informative Informative x 1
  11. Dirty

    Dirty Active Member Gold Contributor

    Joined:
    Oct 15, 2017
    Messages:
    198
    Occupation:
    All the way up front.
    Location:
    Germany
    Balance:
    2,225Coins
    Ratings:
    +185 / 1 / -0
    Do you mean, an actuator where the motor is not mounted in line with the ballscrew, but instead sits on top of the actuator in reverse and drives the ballscrew via a belt drive?

    If the driving wheel and the driven wheel of the belt drive has the same number of teeth: No change! (maybe a small loss due to reduced transmission efficiency)
    1. Count the teeth of the driving wheel.
    2. Count the teeth of the driven wheel.
    3. Divide 1. by 2.
    4. Multiply the actuator speed with that quotient.
    5. Divide the actuator axial force, G-load, by that quotient.

    Remember, there is no such thing as a free lunch: If axial force goes up, speed must go down and vice versa.

    Dirty :D
  12. Gadget999

    Gadget999 Active Member

    Joined:
    Dec 27, 2015
    Messages:
    628
    Location:
    London
    Balance:
    4,930Coins
    Ratings:
    +117 / 4 / -0
    My Motion Simulator:
    2DOF, Arduino
    Hi dirty,

    thank you for replying - do you think many people use the 5mm pitch ballscrew because everyone else uses it and its proven

    the 10mm pitch makes a better sim from what i can see

    ---------------------------------------------------------------

    the chain drive question was looking at using a motor like this to drive a chain up and down

    https://www.motiondynamics.com.au/united-450w-24v-dc-brushed-gear-motor-440-rpm.html
  13. Dirty

    Dirty Active Member Gold Contributor

    Joined:
    Oct 15, 2017
    Messages:
    198
    Occupation:
    All the way up front.
    Location:
    Germany
    Balance:
    2,225Coins
    Ratings:
    +185 / 1 / -0
    Ahhh,... you mean something like Roland van Roy's design?

    The specs of your motor say: 8Nm on the output sprocket @440 RPM.

    To get force:
    1. Measure the radius (not diameter!) of the sprocket (where the chain joints are). I use millimeters.
    2. Then divide 1000 by that radius.
    3. Multiply the torque (8Nm) with the quotient from 2 to get the pull force on the chain :)

    To get speed:
    1. Measure the radius (not diameter!) of the sprocket (where the chain joints are). I use millimeters.
    2. Multiply that by 2π (~6.28) to get the effective circumference of the sprocket in mm.
    3. Multiply that by 440 (RPM) to get the speed in mm/minute.
    4. Divide that by 60 to get the speed in mm/second.

    1018_sfaft_d9xn-3u.jpg
    @30mm you can expect...
    ~266N of pull force
    ~1382mm/s speed

    I'd say that's way too fast, and not enough force. At least for a linear actuator used on a Stewart platform.
    • Useful Useful x 1
    Last edited: Mar 8, 2019
  14. Dirty

    Dirty Active Member Gold Contributor

    Joined:
    Oct 15, 2017
    Messages:
    198
    Occupation:
    All the way up front.
    Location:
    Germany
    Balance:
    2,225Coins
    Ratings:
    +185 / 1 / -0
    Now that I look at the numbers, I can only say: I agree!:thumbs
    If your motors torque is high enough, then you can take advantage of the higher speeds of an SFU1610. Especially those racing addicts among you might want those high actuation speeds. With myself being a flightsim nerd, I was more interested in the smooth motion.

    But the longer I think about it, be more appealing the SFU1610 appear to me...

    Well, I can still replace the ballscrews if the 1605 are too slow. That is one advantage of having powerful motors: you still have the flexibility to adapt your system down the road.

    Dirty:D
    • Informative Informative x 1
  15. adgun

    adgun Member

    Joined:
    Jan 28, 2008
    Messages:
    358
    Occupation:
    mechanic
    Location:
    Netherlands
    Balance:
    4,491Coins
    Ratings:
    +77 / 3 / -0
    You can get the same speed from a 1610 ballscrew than a 1605 screw if you make a 2 to 1 belt reduction.
    Youre making half te rpm from a 1605 screw with the same speed and force (there is a little loss from te belt)
    But this got a lot off thechnical avantages( critical speed longer life time) and saves noice
    Sorry for the bad english
    Ad
    • Like Like x 1
    • Agree Agree x 1
  16. Dirty

    Dirty Active Member Gold Contributor

    Joined:
    Oct 15, 2017
    Messages:
    198
    Occupation:
    All the way up front.
    Location:
    Germany
    Balance:
    2,225Coins
    Ratings:
    +185 / 1 / -0
    That is a pretty good argument!

    I have to admit, when I read the first two lines of your post I was already scratching my head over the question of "...why in the world would anyone wanna do this...?!?!?" ...but, yeah, a reduction of noise, vibration & increased longevity could most probably be achieved by such a setup, I guess.
  17. SeatTime

    SeatTime Well-Known Member

    Joined:
    Dec 27, 2013
    Messages:
    2,148
    Location:
    Newcastle Australia
    Balance:
    26,249Coins
    Ratings:
    +2,440 / 23 / -0
    My Motion Simulator:
    DC motor, Motion platform, 6DOF
    There are a few reason not to do it as well :). I did of course try a belt drive in my actuators design/test phase many years ago.
    [​IMG]
  18. Gadget999

    Gadget999 Active Member

    Joined:
    Dec 27, 2015
    Messages:
    628
    Location:
    London
    Balance:
    4,930Coins
    Ratings:
    +117 / 4 / -0
    My Motion Simulator:
    2DOF, Arduino
    did you find the belts slips ?
  19. SeatTime

    SeatTime Well-Known Member

    Joined:
    Dec 27, 2013
    Messages:
    2,148
    Location:
    Newcastle Australia
    Balance:
    26,249Coins
    Ratings:
    +2,440 / 23 / -0
    My Motion Simulator:
    DC motor, Motion platform, 6DOF
    I used a toothed belt and wheel, so no slip. It worked, but more noise and unwanted side loads on the motor and ballscrew shaft, as there ends up being allot of force on those belts. The direct drive just worked better for my single support bearing ballscrew actuator setup.
    • Informative Informative x 3
  20. adgun

    adgun Member

    Joined:
    Jan 28, 2008
    Messages:
    358
    Occupation:
    mechanic
    Location:
    Netherlands
    Balance:
    4,491Coins
    Ratings:
    +77 / 3 / -0
    The 2 single row deep groove bearings in the motor can handle belt tension load easy, done milions of time without problems.
    Belt tension load up on a single row deep groove bearingblock fitted on a ballscrew can become a problem over time.
    When use a bk12/fk12 bearingblock on a ballscrew there are no problems
    This will be taken by the double row angular contact bearing fitted inside bk12/fk12 bearingblock they can handle side loads easy. and are made fore it
    Half the actuators in the world use belts this way without problems.

    If i remember correctly you did a 1 to 1 ratio and not a 2 to 1 ratio, so youre screw rpm did not slow down by half.
    The hunderds of actuators from different brands i fitted in machinery in the past become more sillent with lower rpm.
    With a 1 to 1 ratio the rpm and noice stay the same, with a 2 to 1 ratio the rpm and noice drops
    Mass interia builds up with rpm, with half the rpm the actuator will react faster.
    • Informative Informative x 2