Delta servo drives and servos. - Page 3


Page 3 of 5 FirstFirst 12345 LastLast
Results 41 to 60 of 81

Thread: Delta servo drives and servos.

  1. #41

    Default Re: Delta servo drives and servos.

    Quote Originally Posted by joeavaerage View Post
    Hi,



    You are correct, my calculations are correct for static thrust, but the accelaration calculation is an approximation and in effect ignores rotational inertia.
    With a very heavy axis the inertia is dominated by the linear acceleration of that mass, with a light axis then the rotational inertia of both
    the armature and ballscrew and whatever gearing is employed become significant.

    My understanding is that its common in engineering circles to 'translate' linear momentum to effective rotational inertia and that gives a more accurate
    picture. My own training is in electrical and electronic engineering and so my mechanical engineering calculations tend to be introductory or first
    approach affairs.

    This may be an appropriate time for me to extend my knowledge in this particular field.

    Such an approach would not be acceptable in a professional environment it is (ususally) sufficient to draw conclusions about a system, and that is
    good enough for me.



    But that makes no allowance for rotational inertia per the above nor does it allow for cutting forces. Note that when was calculating for the axes in
    my machine I allowed half the thrust be 'consumed' by cutting forces, whereas the 1/2g calculation did not. Note also that I said its not too shabby....
    but also implies thats its not that great either, in fact I would call it borderline. If it turns out your (or my) estimate of those countervailing forces
    are underestimated then once you've spent your money only to find that it performs sub-par.

    I paid nearly $3000NZD for my three servos.......a big, I mean very big chunk of my budget. I absolutely cannot afford to make a mistake here.
    Neither do I believe I have...but time will tell. What I've found over several years I've been fiddling with CNC is that if you get it right and chose
    the right piece of equipment even if its expensive, because its right youll use it and use it and use it again over many years. I've also had
    experience where I'll get something which is underspecified or poor quality because I was trying to save money, only to find that it in no way
    meets my needs and is in effect discarded. Despite being cheap to buy it is in fact the most expensive on the basis that I get no use of it.

    You have the time and a forum in which to conduct your research such that you'll have a very fair idea, even if not 'iron clad' idea about
    how your machine will perform BEFORE you spend your money. Use it well.

    Craig
    Craig, I don't know you and I am also new on the forum. Considering those circumstances you are really helpful and obviously extremely intelligent. I appreciate you taking the time to explain this to me and I hope I can return the favor some time!

    My original plan was to use 400W servos with a 2:1 belt reduction on 2010 ballcrews. When the servo motor rotates with 3000rpm, the ballscrew would rotate with 1500rpm (which should be fine considering whip). This results in a maximum feed rate of 15m/min with enough torque to handle my machine.

    My new plan, given the costs of 750W servos is not much higher (see links below), is to use 750W servos, still with a 2:1 reduction on 2020 ballscrews. In the end, same servo 3000rpm and ballscrew 1500rpm will be achieved. What I've done now is increased servo motor power by 100%. To compensate for this I've increased the ballscrew pitch by 100%, resulting in the same torque requirement. Anyway I can now have a speed of 30m/min instead of 15m/min, which is a huge win for me. What do you think? I repeat that I'd like to not go for the 1:1 drive because of ballscrew critical rpm. 3000rpm will definitely cause whip, hence the 2:1 reduction!

    Here are links to aliexpress to all the servos I've been looking at (shipping included in the price):
    - Delta 400W with brake, 500$: https://www.aliexpress.com/item/3267...dae27407OKwUgE
    - Delta 400W without brake, 400$: https://www.aliexpress.com/item/3267...dae27407OKwUgE
    - Delta 750W with brake, 625$: https://www.aliexpress.com/item/3267...491f3eb3Rd9wGf
    - Delta 750W without brake, 500$: https://www.aliexpress.com/item/3267...1ddb3eb3a6NyXB
    - JMC 400W with/without brake, 320$ / 270$: https://www.aliexpress.com/item/4000...dae27407OKwUgE
    - JMC 750W with/without brake, 410$ / 330$: https://www.aliexpress.com/item/4000...1ddb3eb3a6NyXB

    Last edited by NordicCnc; 04-21-2020 at 06:03 AM.


  2. #42
    Member
    Join Date
    Nov 2013
    Posts
    4280
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Hi NordicCnc,
    I have been investigating the motion model incorperating rotational and linear momentum and I am beginning to think that my calculations
    may be overly optimistic. I have a pro engineer, and forum member reviewing my calculation.

    At this time I suspect because I've elected to use such a large ballscrew (32mm diameter) that the rotational inertia dominates the linear inertia.
    I suspect that you will have much less difficulty by virtue of using 20mm diameter screws with very much lower first moment of inertia.

    The prices for the Delta servos are good. I paid about the same but excluding shipping, and shipping was about $80USD each to New Zealand.

    Craig



  3. #43

    Default Re: Delta servo drives and servos.

    Quote Originally Posted by joeavaerage View Post
    Hi NordicCnc,
    I have been investigating the motion model incorperating rotational and linear momentum and I am beginning to think that my calculations
    may be overly optimistic. I have a pro engineer, and forum member reviewing my calculation.

    At this time I suspect because I've elected to use such a large ballscrew (32mm diameter) that the rotational inertia dominates the linear inertia.
    I suspect that you will have much less difficulty by virtue of using 20mm diameter screws with very much lower first moment of inertia.

    The prices for the Delta servos are good. I paid about the same but excluding shipping, and shipping was about $80USD each to New Zealand.

    Craig
    Hello,

    Nice to hear that my questions has lead to some further investigation. Yes you are right about the 32mm diameter ballscrew. The moments of inertia will be extremely high when trying to rotate it 3000rpm. I can't wait to hear the results from the people reviewing your calculations! Perhaps all this could end up in an excel file that can be used by the forum members to select appropriate servo motor size for their applications.

    I agree that the prices are good. Those JMC servo motor prices are even lower for some reason. I checked the specs and everything seems to be identical, even the 17 bit absolute encoder. The manufacturer of the JMC is chinese, while Delta is Taiwanese. I suspect the price different may be because of that, and also the software. Apparently the delta motors can be auto-tuned by running the motor back and forth (software does this) and then it will adjust the parameters according to the feedback. The JMC servo motor software on the other hand is using "real-time" auto-tuning. It allows you to adjust for example the rigidity in real-time, and then the software adjusts related parameters automatically. This means that you can jog the JMC servo around while adjusting the parameters at the same time. Anyway I think that the Delta servo motor tuning software may be more advanced.

    Nordic



  4. #44
    Member mactec54's Avatar
    Join Date
    Jan 2005
    Location
    USA
    Posts
    15362
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Quote Originally Posted by joeavaerage View Post
    Hi,
    my calculation was done with a 32mm ballscrew with 5mm pitch. the mechanical advantage is (within a very close approximation):

    mech avd. = circumference / pitch
    = 32 x pi / 5
    =20.1

    Most mechanical enginners will recognise that I have made an approximation here. The precise formula is:
    mech adv. = 1 / sin(tan-1 pitch / circumference)
    =1 / sin( tan-1 (5 / 32 x pi)
    =1 / sin ( tan-1 (0.04973))
    =1/sin (2.847 degrees)
    =1/ 0.0496
    =20.13

    So the difference between the approximation and the precisce formula are very very close indeed. As the pitch to diameter ratio decreases however
    the approximation gets worse. Lets takes NordicCnc's example of 20mm diameter and 20mm pitch.

    The approximation is:
    mech adv.= circumference/ pitch
    =20 x pi /20
    = 3.141
    The precise formula is:
    mech adv. =1/sin (tan-1(pitch /circuference)
    = 1/sin (17.65 degrees)
    =3.296

    So the variation between the approximation and the precise forumla is 5%

    Let say we have a servo (or other motor) that applies a 1Nm torque to NordicCnc's 20mm diameter 20mm pitch screw:
    The force at 10mm radius:
    Force @0.01m=1/0.01
    =100N
    With a mechanical advantage ( previously calculated) of 3.296 means a thrust of:
    thrust= 100 x 3.296
    =329.6N

    Note also the the Yaskawa calculation applies a 'ballscrew efficiency' of 0.9, so in interests of comparison lets do the same:
    thrust =329.6 x 0.9
    =296.6

    If NordicCnc's gantry weighs 60 kg then the acceleration is:

    accel= force/ mass
    =296.6/ 60
    =4.944m/s2
    or 1/2g, not shabby for a hobby machine but not great either, and this is for a 1Nm input.

    A 400W servo has 1.27Nm, so an accel of 6.2m/s2 results.

    A 750W servo has 2.4Nm so an accel of 11.9m/s2 results.

    Clearly with such a coarse pitched screw then a 750W servo is indicated.

    The problem here is that the pitch of the screw is high therefore the mechaincal advantage is low. To counteract the low mechaincal advantage
    a belt reduction is in order. The other alternative is to use a lower pitched screw direct coupled. The same calculation but with 5mm pitch and the
    same 20mm diameter:
    mech adv.=12.5
    thrust (per N applied torque)=1130.4N (allowing ballscrew efficieny of 0.9)
    accel (60kg axis)=18.8m/s2 per N applied torque
    accel (400W servo)=23.9m/s2
    accel (750W servo)=45.2m/s2

    Clearly reducing the pitch of the ballscrew has markedly increased the achievable acceleration.

    This would be my recomendation to NordicCnc, reduce the pitch of your screws to 5mm and then direct couple the servos. As you have established
    400W is adequate, even more than adequate, then 750W is doubly 'more than adequate' and costs as little as $30 extra each.

    Craig
    Reducing the pitch to 5mm is not an option for a machine like he is building between 12mm pitch and 25mm is normal for a machine like this

    Mactec54


  5. #45
    Member
    Join Date
    Nov 2013
    Posts
    4280
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Hi,
    JMC is a 'johnny come lately' to the market and speialize in being the cheapest.
    Delta have been around for years and specialize in quality at an affordable price.

    Craig



  6. #46
    Member ger21's Avatar
    Join Date
    Mar 2003
    Location
    Shelby Township
    Posts
    35538
    Downloads
    1
    Uploads
    0

    Default Re: Delta servo drives and servos.

    The JMC are only about $100 cheaper. So is saving $300 worth it to deal with poor documentation and unknown tuning software??

    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)


  7. #47
    Member
    Join Date
    Nov 2013
    Posts
    4280
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Hi,

    The JMC are only about $100 cheaper. So is saving $300 worth it to deal with poor documentation and unknown tuning software??
    I have no idea what JMC documentation or software is like, it might be OK......then again it might be rubbish.

    I do have and use Delta documentation and software. It is an English translation so it has a few quirks but is in every other respect very good indeed.
    I would rate it 9 out of 10 by comparison to Allen Bradley documentation which I also use and am familiar with.

    Likewise I use both Allen Bradley (now-a-days called Rockwell) and Delta software. I had to pay ($200NZD) for the Rockwell software, its good. Delta
    software is free and also good. There are sublte differences but both are excellent products.

    I regard that Delta has taken the time and effort and has the experience to compose software and documentation to match the likes of Rockwell
    a very good sign that Delta seek to produce quality products.

    Craig



  8. #48
    Member
    Join Date
    Nov 2013
    Posts
    4280
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Hi,
    I've done the calclations for the acceleration potential of my machine including rotational inertia. I've had my calculation checked
    by peteeng, a professional mechanical engineer. Additionally I have Hiwins calculation formulas and can double check all the calculations
    and they all point to the same conclusion.

    My previous calculations are widly optimistic.

    The full calculation is:
    Torque= Ieff. dw/dt

    dw/dt is the angular acceleration.
    Ieff is the total effective first moment of inertia.

    Ieff is the sum of the individual components.

    1)The rotational inertia of the armature of the servo. For my 750W 34size Delta servo that is (from the spec sheet)=1.13 .10-4 kg.m2
    2)The rotational inertia of the ballscrew. For my 32mm dia screw of 650mm length =5.252 .10-4 kg.m2
    Note that I got this figure from the THK spec sheet but both I and peteeng calculated it from first principles and all agree.
    3)The effective rotational inertia implied by the axis mass. This forumla I derived from first principles and agrees with the theoretical treatment
    published by Hiwin and also agrees with peteengs analysis.
    Ilinear= m.(p/2pi)2 where p=pitch in meters and m is the axis mass.
    Using numbers for my machine, p=0.005m and m=110kg:
    Ilinear=110. (.005/2 x 3.141)2
    =0.69 kg.m2

    Ieff is the sum of these components:
    Ieff= (1.13 + 5.252 + 0.69) .10-4
    =7.07 .10-4 kg.m2

    dw/dt= 2.4 /7.07 .10-4
    =3395 rad/s2

    And to convert that to linear acceleration:
    Alinear= dw/dt x p/2pi
    =2.7 m/s2

    This figure is less than 1/10th of what I had calculated previously, and is my error. Note how despite the heavy axis, its contribution
    to the first moment of inertia is small, even the first moment of the servo armature exceeds it, but both are dwarfed by the first moment of the ballscrew.
    I had not made allowance for that factor previously.

    The take away feature is that with my machine at least 'the rotational mass of the ballscrew dominates the acceleration equation'.

    Craig



  9. #49

    Default Re: Delta servo drives and servos.

    Quote Originally Posted by ger21 View Post
    The JMC are only about $100 cheaper. So is saving $300 worth it to deal with poor documentation and unknown tuning software??
    You right. The poor documentation outweighs the price difference in my opinion.



  10. #50

    Default Re: Delta servo drives and servos.

    Quote Originally Posted by joeavaerage View Post
    Hi,
    I've done the calclations for the acceleration potential of my machine including rotational inertia. I've had my calculation checked
    by peteeng, a professional mechanical engineer. Additionally I have Hiwins calculation formulas and can double check all the calculations
    and they all point to the same conclusion.

    My previous calculations are widly optimistic.

    The full calculation is:
    Torque= Ieff. dw/dt

    dw/dt is the angular acceleration.
    Ieff is the total effective first moment of inertia.

    Ieff is the sum of the individual components.

    1)The rotational inertia of the armature of the servo. For my 750W 34size Delta servo that is (from the spec sheet)=1.13 .10-4 kg.m2
    2)The rotational inertia of the ballscrew. For my 32mm dia screw of 650mm length =5.252 .10-4 kg.m2
    Note that I got this figure from the THK spec sheet but both I and peteeng calculated it from first principles and all agree.
    3)The effective rotational inertia implied by the axis mass. This forumla I derived from first principles and agrees with the theoretical treatment
    published by Hiwin and also agrees with peteengs analysis.
    Ilinear= m.(p/2pi)2 where p=pitch in meters and m is the axis mass.
    Using numbers for my machine, p=0.005m and m=110kg:
    Ilinear=110. (.005/2 x 3.141)2
    =0.69 kg.m2

    Ieff is the sum of these components:
    Ieff= (1.13 + 5.252 + 0.69) .10-4
    =7.07 .10-4 kg.m2

    dw/dt= 2.4 /7.07 .10-4
    =3395 rad/s2

    And to convert that to linear acceleration:
    Alinear= dw/dt x p/2pi
    =2.7 m/s2

    This figure is less than 1/10th of what I had calculated previously, and is my error. Note how despite the heavy axis, its contribution
    to the first moment of inertia is small, even the first moment of the servo armature exceeds it, but both are dwarfed by the first moment of the ballscrew.
    I had not made allowance for that factor previously.

    The take away feature is that with my machine at least 'the rotational mass of the ballscrew dominates the acceleration equation'.

    Craig
    I checked the formulas you have used also in my mechanical engineering handbook that I used for my Bachelor's degree. The formula for Alinear is correct but you seem to have used one decimal too much for the pitch. It should be 0,005m (5mm pitch):

    Alinear = 3395rad/s2 * 0,005m / 2 * pi
    Alinear = 26,66m/s2

    Or did I miss something?



  11. #51
    Member
    Join Date
    Nov 2013
    Posts
    4280
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Hi,

    Alinear = 3395rad/s2 * 0,005m / 2 * pi
    Alinear = 26,66m/s2
    No you have misread the forumla.

    dw/dt=3395 rad/s2

    Arotational= dw/dt /2pi (revs/s2)....ie divide the angular acceleration in radians per sec2 by 2pi to
    get angular acceleration in revolutions per sec2. Now Alinear is trivial:

    Alinear= p x Arotational
    = dw/dt .p/2pi
    = 0.005 x 3395/2pi
    = 0.005 x 3395/6.283
    =0.005 x 540.33
    =2.701 m/s2

    Craig



  12. #52

    Default Re: Delta servo drives and servos.

    Quote Originally Posted by joeavaerage View Post
    Hi,



    No you have misread the forumla.

    dw/dt=3395 rad/s2

    Arotational= dw/dt /2pi (revs/s2)....ie divide the angular acceleration in radians per sec2 by 2pi to
    get angular acceleration in revolutions per sec2. Now Alinear is trivial:

    Alinear= p x Arotational
    = dw/dt .p/2pi
    = 0.005 x 3395/2pi
    = 0.005 x 3395/6.283
    =0.005 x 540.33
    =2.701 m/s2

    Craig
    That makes sense, my bad. I compared the calculations to the Yaskawa software and the results are spot on, if you use ballscrew efficiency of 1 (0,85-0,95 in reality).

    Anyway, I quickly made and excel spreadsheet for calculating horizontal axis maximum acceleration, based on user inputs (yellow cells). You can even spec 1:1 direct drive (with coupling OR belt drive) and any other gear ratio with belt drive. Just insert rotation moment inertia for the pulleys OR the coupling. The calculations will include these values automatically.

    Attached Thumbnails Attached Thumbnails Delta servo drives and servos.-screenshot-jpg  
    Attached Files Attached Files


  13. #53
    Member
    Join Date
    Nov 2013
    Posts
    4280
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Hi,

    if you use ballscrew efficiency of 1 (0,85-0,95 in reality).
    Yes I forgot to include that factor.

    If need be I could use a low lash planetary gearbox of 3:1. That would increase acceleration at the expense of speed.

    At this point in time I not going to change anything. My current mini-mill has an acceleration, set in Machs motor tuning of
    375mm/s2. The steppers and gearbox combo mean I could have a lot more acceleration but the machine
    starts to throw itself around the room unless I tie it to the wall. I've found 375mm/s2 is entirely adequate for
    my mini-mill and it follows toolpaths I set it no problems.

    My inclination is to try acceleration of 2.7m/s2 and see how it goes.

    As you've shown it takes only 90ms to get to full speed or 12mm traveled. It might well be enough.

    Craig

    Last edited by joeavaerage; 04-22-2020 at 05:07 AM.


  14. #54

    Default Re: Delta servo drives and servos.

    Quote Originally Posted by joeavaerage View Post
    Hi,



    Yes I forgot to include that factor.

    If need be I could use a low lash planetary gearbox of 3:1. That would increase acceleration at the expense of speed.

    At this point in time I not going to change anything. My current mini-mill has an acceleration, set in Machs motor tuning of
    375mm/s2. The steppers and gearbox combo mean I could have a lot more acceleration but the machine
    starts to throw itself around the room unless I tie it to the wall. I've found 375mm/s2 is entirely adequate for
    my mini-mill and it follows toolpaths I set it no problems.

    My inclination is to try acceleration of 2.7m/s2 and see how it goes.

    As you've shown it takes only 90ms to get to full speed or 12mm traveled. It might well be enough.

    Craig
    Sounds like a good plan! Anyway the excel should help anyone who is not sure about what size of servo motor they need. Rule of thumb would be to use a safety factor of at least 2, which eliminates the need of friction coefficients, ballscrew efficiency and transmission efficiency. Also remember that what is critical is when the servo motor need to quickly accelerate/decelerate . Then you have a peak torque of 300% at your disposal anyway.



  15. #55
    Member
    Join Date
    Nov 2013
    Posts
    4280
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Hi,
    I thought I'd post my derivation of the forumla that combines linear momentum with rotational momentum. Its been many years since
    I opened a physics book let alone read one!

    My hypothesis is that there is some effective first moment of inertia, Jeff such that the total kinetic energy, Etot of a linearly
    accelerating axis AND rotating ballscrew/servo assembly is described by:

    Etot = 1/2 * Jeff * w2...............................equation [1]

    Note I use MKS units:
    Etot in Joules
    Jeff in kg*m2
    w in radians per second, rad/s

    But we know that the total kinetic energy has two components, first the translational energy of the axis mass and the rotational energy of the rotating components:

    Etot = 1/2 m*v2 + 1/2 Jcomb* w2.............. where Jcomb is the first moment of inertia of the rotating parts

    But the axis velocity v is related to the angular velocity of the ballscrew, after all thats why we use ballscrews to precisely translate rotoational position
    to linear position:

    v = w/2pi * l where l is the pitch of the ballscrew in meters. Substituting:

    Etot = 1/2 *m*(w*l/2pi)2 + 1/2 Jcomb*w2
    =1/2*w2 { m*(l/2pi)2 + Jcomb }...................................equation [2]

    Now we have two equations describing Etot, equation [1] and equation [2], using the principle of equating coefficents:

    1/2 *Jeff * w2 = 1/2*w2 { m*(l/2pi)2 + Jcomb }

    Jeff=m*(l/2pi)2 + Jcomb

    So the component of the total effective first moment of inertia that is due to the linear movement of the axis is:
    m*(l/2pi)2

    For example my axis is 110kg, and the ballscrew pitch is 5mm or 0.005m:

    =110 * (0.005/2pi)2
    =110 * (0.005/6.283)2
    =110 * (0.0007958)2
    =0.69 *10-4 kg*m2

    Craig



  16. #56
    Member
    Join Date
    Nov 2013
    Posts
    4280
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Hi,
    thought I would do some calculations about what a 2.7m/s2 acceleration would mean for my new build machine.

    While the mill beds (75kg grey cast iron) are 700mm long, the linear rails atop them are 650mm and the 32mm ballscrew are 650mm
    overall. The ballcrew (BNFN by THK) is double nut so the free travel of each ballscrew is 358mm.

    My design calls for travels between limit switches of 350mm x 350mm x 350mm.

    I had intended to use 'field weakening' that would allow my Delta servos to run at 5000 rpm despite being rated at 3000rpm.
    If I use this strategy then the nominal rated torque of 2.4Nm is available up to 3000 rpm but then it decreases linearly between
    3000 and 5000 rpm, to an end point of about 1.44Nm.

    This decreasing torque would prove a major complication in the simple claculations I wish to do. I have elected therefore to
    not utilise the field weakening operating regime.

    The overall parameters are:
    Servo: rated torque=2.4Nm
    rated speed=3000rpm
    Ballscrew: pitch =5mm or 0.005m

    G0, or maximum axis speed is 3000 x 0.005=15m/min or 0.25m/s

    Time to accelerate to 0.25m/s:
    t=v / a
    =0.25 /2.7
    =92ms
    Distance travelled is over that 92ms acceleration interval is:
    d=1/2 a t2
    =1/2 * 2.7 * 0.0922
    =0.0116m or 11.6mm

    The same time and distance would occurr at deceleration.

    The time take to traverse from one limit switch to the other (350mm) is:

    ttot= (0.35 -0.0116 -0.0116)/0.25 +92ms +92ms
    =1.49s

    So my machine will traverse it heaveist axis from one limit switch to the other in 1.5 seconds or so. I think I can wait that long!!

    Craig



  17. #57
    Member
    Join Date
    Nov 2013
    Posts
    4280
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Hi,
    in fact if a nominal 110kg axis can lurch 350mm in only 1.5 seconds I'm seriously going to have to tie my machine to the wall
    or bolt it to the floor!

    Craig



  18. #58
    Member mactec54's Avatar
    Join Date
    Jan 2005
    Location
    USA
    Posts
    15362
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Quote Originally Posted by joeavaerage View Post
    Hi,
    in fact if a nominal 110kg axis can lurch 350mm in only 1.5 seconds I'm seriously going to have to tie my machine to the wall
    or bolt it to the floor!

    Craig
    You don't have enough machine mass if this is a problem, or to much motor for what you are trying to do, dumbing down a motor so it won't move your machine around is as dumb as it gets this makes all your numbers meaningless

    Mactec54


  19. #59
    Member Hazron's Avatar
    Join Date
    Dec 2019
    Posts
    10
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Gents can I ask your option on running the late 90's Panasonic servos on my Bed Mill for a control retrofit. Will they achieve reasonable finishes given they are in effect around 5000 ppr for 5 mm screws. I found this post which indicates they would be adequate ("reasonable accuracy and smooth motion") but more resolution would be better. https://centroidcncforum.com/viewtop...9bf3846411d6d3

    Obviously later servos run much higher resolution and smoothing algorithms. So what's adequate mean and what the difference in finish compared to new servos?

    Do I go to the cost and time input and buy 3 new delta or Yaskawa systems? I assume I will see a marked difference??



  20. #60
    Member
    Join Date
    Nov 2013
    Posts
    4280
    Downloads
    0
    Uploads
    0

    Default Re: Delta servo drives and servos.

    Hi,

    Obviously later servos run much higher resolution and smoothing algorithms. So what's adequate mean and what the difference in finish compared to new servos?

    Do I go to the cost and time input and buy 3 new delta or Yaskawa systems? I assume I will see a marked difference??
    It too have 5mm pitch ballscrews and I use electronic gearing to arrive at 5000 pulse/rev or 1um per step. The finish is perfect. Just because the servos
    have a 160,000 count per rev does not mean you have to use it, and even if you did then you would require a motion controller that could produce
    step/direction signals in the low mega-Hertz range, at huge cost......and to what advantage.......none.

    If you went and bought new high resolution servos you would see no, or virtually no difference to surface finish or smoothness. Later model
    servos may have better tuning aids and control modes that may help but the extra encoder resolution will make no difference.

    Craig



Page 3 of 5 FirstFirst 12345 LastLast

Tags for this Thread

Posting Permissions

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


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

Delta servo drives and servos.

Delta servo drives and servos.