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IndustryArena Forum > CNC Electronics > Servo Motors / Drives > Are Chinese servos a gamble? Servos vs Leadshine closed loop
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  1. #21
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    My voltage is all over the map, supposed to be 240 single phase. Just today my low voltage was 230, and the high was 246.8, I have seen it as low as 219 and as high as 250.2. So far nothing has blown up.
    Jim Dawson
    Sandy, Oregon, USA

  2. #22
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    If you did go with the Dmm system and use there high voltage Servo Drives, you would have to use a line reactor, or a Transformer so you can stabilize your line voltage, or you would kill the servo Drives with the over voltage that you are experiencing, this would be a must to get under control for any system you use
    Yes, DMM sent me an application note after I blew my drive the first time I powered it up. They say they are good to 240v + 10% (264V, but they are apparently very sensitive to spikes, as my voltage was about 245V at the time.
    I'm going to use a transformer to lower my voltage to 220V, and will also probably add the line reactor as well.

    They did repair the drive for free. I just had to ship it to them, which cost me $40.
    Gerry

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

  3. #23
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    Quote Originally Posted by RCaffin View Post
    Chuckle.
    I have seen 110VAC, 115 VAC, 120 VAC quoted for America, and even 220 VAC and 240 VAC in some places.
    Roger
    Yes quoted in words only, you can't change what people want to write, I have corrected you before about the NA power supply

    In 1967 the nominal voltage rose to 120/240v +/- 5%
    Today virtually all American homes and businesses have access to 120/240 V at 60 Hz. Both voltages are available on the three wires (two "hot" legs of opposite phase (split phase) and one "neutral" leg.

    NA. Mains power is sometimes spoken of as 110v; however, 120/240v is the nominal voltage.


    Quote Originally Posted by RCaffin View Post
    At one stage we were running on 245 VAC for most of the day, but it dropped to <220 VAC around dinner time when several houses up the road started cooking. Yeah, rural/farming area. Then someone else started to (try to) pull >60 A off a single phase, and essentially blew the local transformer. Well, the up-side of that was that we got a new and bigger pole transformer AND new aerials up the road. But the voltage still fluctuates.
    It shows how far behind your system is, 60amps should not of had any affect, I have 400A supply at my house, and could have more if I wanted it, all new homes built 2/3 thousand square feet, have a standard 120/240v 200A supply in the US

    Fluctuation can happen to anyone any where, this is not always a usage or supply problem
    Mactec54

  4. #24
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    Quote Originally Posted by ger21 View Post
    Yes, DMM sent me an application note after I blew my drive the first time I powered it up. They say they are good to 240v + 10% (264V, but they are apparently very sensitive to spikes, as my voltage was about 245V at the time.
    I'm going to use a transformer to lower my voltage to 220V, and will also probably add the line reactor as well.

    They did repair the drive for free. I just had to ship it to them, which cost me $40.
    May or may not help you, but I use a 500SV46B buck boost transformer, wired as an autotransformer, so that only the stepdown load is run through the transformer. In this case, I am able to lower 245V down to ~228V, while maintaining a 7.5 KVA capacity, but using only a 0.5 KVA transformer that is around 15 pounds.

    Kind of expensive new, but there is usually one on ebay for around $50 shipped, which is what I paid for mine.

  5. #25
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    I heard the chinese servos are difficult to tune without proper software (which probably doesn't exist for them in english, yet). This still means they can be tuned though, right?

  6. #26
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    Quote Originally Posted by j3dprints View Post
    I heard the chinese servos are difficult to tune without proper software (which probably doesn't exist for them in english, yet). This still means they can be tuned though, right?
    You would have to check that out with the supplier, to see if they have tuning/setup software, any of the good ones will have a PDF manual, and software, don't buy any that you can't get a good English manual with, or can down load before you buy
    Mactec54

  7. #27
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    Quote Originally Posted by RCaffin View Post
    I have seen 110VAC, 115 VAC, 120 VAC quoted for America, and even 220 VAC and 240 VAC in some places.
    Yeah, and oddly enough they use 120/240 in Richmond BC, where I believe DMM is situated. That's in Canada!
    N.A. in general has settled on 120/240 as a standard, you may still see appliances marked 110vac which is the old standard.
    It is normal for a power grid service to fluctuate and generally the accepted industrial standard for fluctuation for industrial machinery is ±10%.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  8. #28
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    This would make a great HM47/RM45 mill spindle motor if it does what they say it does

    https://www.ebay.com.au/itm/7-7NM-2K...MAAOSwxixZ5w~L

    Free shipping to Australia, 649.90 AUD similar price range to a class F 2.2kw motor and VFD. This provides approximately the same torque (at max RPM) but weighs 10kgs compared to 21,
    a big advantage when the z axis must deal with the mass of the motor. Might be a good way to test the quality of these servos where position control is not essential.
    I sent them a message asking for the manual, will post on here if they send me one.

    Ed
    Perth

  9. #29
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    They got back to me in about 5 minutes.

    https://1drv.ms/b/s!ArjCcDfiJFt0fm4tmJyHfblBVm0

  10. #30
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    They do indeed seem good. You can get them for 600 shipped.

    Is 2500 ppr really a big deal on these servos?

    Also servos outperform a leadshine in every respect, really? I am not after super fast rapids, I would like Tormach potential which boast under 150ipm for their ipm speeds on their mills and good ACCURACY. I am aware they use open loop with torque reserve and good engineering to not miss steps. With leadshine closed loop steppers I could achieve no missed steps and similar IPM / accuracy I think. Or with their clones. I have read steppers if they don't miss steps can actually be more accurate than servos (in my price range).

    Prices for Aussie customers and pros/cons I've noted are as follows:
    Leadshine CLONE CLOSED LOOP steppers for like $700 AUD delivered (clones so.... not as great drivers?)

    Leadshine closed loop genuine (chinese models) are more like $900 (steppers, not servos, but is this really a disadvantage if you're not chasing massive IPM)

    Chinese Servos come in at 1000 to 1200 (good but 2500ppr, and bad manuals),

    Chinese servos with better encoders - around 1500-1600

    DMM for just under $2000 delivered to Aus.

    I am really really looking toward option 1 - leadshine clones. Save 1400 over DMM. I reckon they will equal whatever Tormach has and the money I'll save will be better spent on other things - better ballscrews later, hiwin rails for x and y, A nice surface table, or even money off a Skyfire / Tormach / VMC which I might upgrade too later.

  11. #31
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    Quote Originally Posted by j3dprints View Post

    Is 2500 ppr really a big deal on these servos?
    .
    Keep in mind that that is the basic quadrature count, most controllers will times this by 4 by counting all four edges.
    Resulting in 10k pulses/rev in this case.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  12. #32
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    Quote Originally Posted by edmunns View Post
    They got back to me in about 5 minutes.

    https://1drv.ms/b/s!ArjCcDfiJFt0fm4tmJyHfblBVm0
    These servo motors are OK but there servo drives users have had problems with them, I would not touch that brand
    Mactec54

  13. #33
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    Quote Originally Posted by j3dprints View Post
    They do indeed seem good. You can get them for 600 shipped.

    Is 2500 ppr really a big deal on these servos?

    Also servos outperform a leadshine in every respect, really? I am not after super fast rapids, I would like Tormach potential which boast under 150ipm for their ipm speeds on their mills and good ACCURACY. I am aware they use open loop with torque reserve and good engineering to not miss steps. With leadshine closed loop steppers I could achieve no missed steps and similar IPM / accuracy I think. Or with their clones. I have read steppers if they don't miss steps can actually be more accurate than servos (in my price range).

    Prices for Aussie customers and pros/cons I've noted are as follows:
    Leadshine CLONE CLOSED LOOP steppers for like $700 AUD delivered (clones so.... not as great drivers?)

    Leadshine closed loop genuine (chinese models) are more like $900 (steppers, not servos, but is this really a disadvantage if you're not chasing massive IPM)

    Chinese Servos come in at 1000 to 1200 (good but 2500ppr, and bad manuals),

    Chinese servos with better encoders - around 1500-1600

    DMM for just under $2000 delivered to Aus.

    I am really really looking toward option 1 - leadshine clones. Save 1400 over DMM. I reckon they will equal whatever Tormach has and the money I'll save will be better spent on other things - better ballscrews later, hiwin rails for x and y, A nice surface table, or even money off a Skyfire / Tormach / VMC which I might upgrade too later.
    You heard wrong they could never be as accurate as AC Servos, even the cheap ones, when you have to chase your dollars as I said before buy what you can afford, but don't get the servos that Edmunns just listed, if these where the ones you looked at

    It looks like the genuine Leadshine is your best bet , with there encoders at,2500=10,000ppr if they are incremental, yes Encoders are a big deal, these servo's are not worth the extra money to buy them, the Dmm Encoder is 65,384ppr standard
    Mactec54

  14. #34
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    Yeah, I wasn't suggesting to go down that path, you get what you pay for, especially with servos. That manual looks like a nightmare haha.

  15. #35
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    With encoder resolution, you can calculate your Least Input Increment, this is the smallest value the machine can position to.
    For example, if the quadrature encoders are 2500 = 10,000 pulses/rev when x4, and you have a motor driving a 0.2" lead Ball screw direct, then the Least Input Increment = 0.2"/10k =0.00002", or 0.5 Micrometer.
    To go much smaller L.I.I. with any accuracy would also require very precise machine mechanics.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  16. #36
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    With leadshine closed loop steppers I could achieve no missed steps and similar IPM / accuracy I think.
    There is really no comparison between closed loop steppers and servos. Look at a torque curve for a closed loop stepper. At 1000 rpm, it will have lost at least half of it's rated torque. A servo will have full torque up to 3000rpm, with 3x peak torque still in reserve.

    When used properly, an open loop stepper should give nearly identical performance to a closed loop stepper. They are both steppers, after all, with the same amount of power.
    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)

  17. #37
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    Quote Originally Posted by ger21 View Post
    There is really no comparison between closed loop steppers and servos. Look at a torque curve for a closed loop stepper. At 1000 rpm, it will have lost at least half of it's rated torque. A servo will have full torque up to 3000rpm, with 3x peak torque still in reserve.

    When used properly, an open loop stepper should give nearly identical performance to a closed loop stepper. They are both steppers, after all, with the same amount of power.
    I have leadshine easy servos. they don't "stall" and fault when you drift past your allowed error. beyond that, they are just steppers, with all of the performance benefits and drawbacks. id call them safety steppers, cause they are not at all like your typical ac servos.

    I was hoping someone in this thread would have some first hand info on these Chinese servos. I have a couple of brother tapping centres, and they take an unusual motor size - 86mm metric. the stock sanyo motors also pack a very big punch for a little motor. my drives are dead in one of the machines (previous owner was not too bright with his electricity knowledge) and new sanyo stuff makes yaskawa look like discount bin on prices. were talking 3k+ per axis for new motors and drives. oddly though, one of these Chinese brands makes a servo the exact right size and torque. its only lacking on speed, limited to 3000rpm. at $350-$400cdn per axis from a (seemingly) reputable seller, I'm kinda thinking they could be a good short term solution to get the machine running with linuxcnc. delta also makes a kits in the right size, but less torque, and $1000 per axis - id just go with sanyo when we get into that price range. of course, the delta and sanyo (and yaskawa etc) have very advanced dynamic auto tuning, 3khz bandwidth, 24 bit encoders, and all the most modern fluffy features you could ask. I expect little of the Chinese motors and drives other than to move where its been asked.

    on power - this may be where paying for good hardware is worth while sometimes. a good servo drive, like my now dead sanyo for example said to take in "200v" can often take anything from 190v single phase to 245v 3 phase and still run. a properly built industrial class machine (like my brother) also has a biasing transformer, which allows it to take in all sorts of voltage in 5% increments and spit out the desired level (220v in this machine). my power is stable 600v, plus or minus maybe 5% on a bad day. if you have very bad stability, you really need to have that taken care of, as it can damage things. the idiot who last tried to hook up my machine tried to convert it from 380v in, to 220v in, but did not wire the internal transformers correctly an poof. all drives dead on power up.

    anyhow, who has actually used those Chinese servo kits in a machine?

  18. #38
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    Quote Originally Posted by ihavenofish View Post
    I have leadshine easy servos. they don't "stall" and fault when you drift past your allowed error. beyond that, they are just steppers, with all of the performance benefits and drawbacks. id call them safety steppers, cause they are not at all like your typical ac servos.

    I was hoping someone in this thread would have some first hand info on these Chinese servos. I have a couple of brother tapping centres, and they take an unusual motor size - 86mm metric. the stock sanyo motors also pack a very big punch for a little motor. my drives are dead in one of the machines (previous owner was not too bright with his electricity knowledge) and new sanyo stuff makes yaskawa look like discount bin on prices. were talking 3k+ per axis for new motors and drives. oddly though, one of these Chinese brands makes a servo the exact right size and torque. its only lacking on speed, limited to 3000rpm. at $350-$400cdn per axis from a (seemingly) reputable seller, I'm kinda thinking they could be a good short term solution to get the machine running with linuxcnc. delta also makes a kits in the right size, but less torque, and $1000 per axis - id just go with sanyo when we get into that price range. of course, the delta and sanyo (and yaskawa etc) have very advanced dynamic auto tuning, 3khz bandwidth, 24 bit encoders, and all the most modern fluffy features you could ask. I expect little of the Chinese motors and drives other than to move where its been asked.

    on power - this may be where paying for good hardware is worth while sometimes. a good servo drive, like my now dead sanyo for example said to take in "200v" can often take anything from 190v single phase to 245v 3 phase and still run. a properly built industrial class machine (like my brother) also has a biasing transformer, which allows it to take in all sorts of voltage in 5% increments and spit out the desired level (220v in this machine). my power is stable 600v, plus or minus maybe 5% on a bad day. if you have very bad stability, you really need to have that taken care of, as it can damage things. the idiot who last tried to hook up my machine tried to convert it from 380v in, to 220v in, but did not wire the internal transformers correctly an poof. all drives dead on power up.

    anyhow, who has actually used those Chinese servo kits in a machine?

    Only feedback I have received is from this guy, who said "[COLOR=var(--ytd-comment-text-color)]Thanks, those you sent me link, are KRS. Those work fine. I would suggest you to go 750W because this servos dont have auto tunning option, and there is no pc software for them to have scope. So they can be a bit more tricky to tune. So you wouldnt want to push them, as you will have quite a bit of follow error. I can give you contact of my forwarder, and he will give you 750W set of motor, drive and cables for 250USD." See the youtube comments in this vid:[/COLOR]
    https://www.youtube.com/watch?v=_ztj...13526415759229

    So there are chinese price servos with 20 bit encoders, they're a bit more expensive though. Is this a big deal? You might want to look at them
    https://www.aliexpress.com/item/750W...ceBeautifyAB=0
    If you could elaborate on why 2500ppr is inadequate for a home gamer like me and I need 20 bit I'd appreciate it. Seems like a fair bit. Also if someone could explain why he basically says "Go big on the servos" above. Kind of worrying.

    Can I ask you a question? For $1000, I can grab 3 of these servos, with their 2500ppr encoders. Would you do that over spending $300 less on leadshine hybrid steppers for a home cnc? I almost think for a home game like me I could get more accuracy out of the steppers, which is my primary concern. But microstepping and blah blah stuff I don't totally understand, which servos don't suffer from. I don't like the idea of poor 'strength' between steps when microstepping.

  19. #39
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    Re: Are Chinese servos a gamble? Servos vs Leadshine closed loop

    Quote Originally Posted by j3dprints View Post



    Only feedback I have received is from this guy, who said "[COLOR=var(--ytd-comment-text-color)]Thanks, those you sent me link, are KRS. Those work fine. I would suggest you to go 750W because this servos dont have auto tunning option, and there is no pc software for them to have scope. So they can be a bit more tricky to tune. So you wouldnt want to push them, as you will have quite a bit of follow error. I can give you contact of my forwarder, and he will give you 750W set of motor, drive and cables for 250USD." See the youtube comments in this vid:[/COLOR]
    https://www.youtube.com/watch?v=_ztj...13526415759229

    So there are chinese price servos with 20 bit encoders, they're a bit more expensive though. Is this a big deal? You might want to look at them
    https://www.aliexpress.com/item/750W...ceBeautifyAB=0
    If you could elaborate on why 2500ppr is inadequate for a home gamer like me and I need 20 bit I'd appreciate it. Seems like a fair bit. Also if someone could explain why he basically says "Go big on the servos" above. Kind of worrying.

    Can I ask you a question? For $1000, I can grab 3 of these servos, with their 2500ppr encoders. Would you do that over spending $300 less on leadshine hybrid steppers for a home cnc? I almost think for a home game like me I could get more accuracy out of the steppers, which is my primary concern. But microstepping and blah blah stuff I don't totally understand, which servos don't suffer from. I don't like the idea of poor 'strength' between steps when microstepping.


    my sanyo servos are 2500 line and 1024 line. under the brother control, both are/were perfectly fine. under linuxcnc I am having issues tuning the 1024 line ones at its original 787ipm, 0.25g acceleration, but I do not know if that is in any way related to the encoders. as a reference, the 2500 line motors on the other machine run 1420ipm, 0.5g acceleration under the stock brother control. ive not tried them under Linux of course as the drives are dead.

    high resolution encoders are generally not that important unless your machine is of a very high performance. 2000ipm, 2g acceleration, high servo loop rates, etc. something you don't encounter much in the sub $100000 machine market. on the flip side, the extra encoder counts can help the drive run the motor more smoothly at very low speeds - imagine milling a line from x0y0 to x0.0001 y10 at 2ipm. lots of encoder counts help that x move to create an actual line, not a stair step. its hard to say how critical this is though if your mechanicals are not also super precision. even 0.0002" of backlash could erase many of the benefits.

    you also need to know what you get with each encoder in terms of precision. most of these 2500line types are glass. they are very precise, if not high resolution. encoders like the dmm ones, and similar types are magnetic, and not very precise in comparison, but have a lot of resolution. so, between the 2, the "precision" of your machine likely is the same. the higher resolution one might just run a little smoother, a little quieter, and track a little better going fast. 24 bit encoders like on new high end drives are a different matter. they are both precise and stupid high res, but also cost more for one encoder than a set of 3 Chinese drives and motors. example: siemens ~750w servo with "low precision" resolver $699. same motor with 24 bit endat multi turn absolute encoder $1999. eep!

    of course, then you go and run step and direction out of mach3 at 50khz and you may as well flush it all down the toilet

    I don't really have a suggestion for stepper vs servo for your performance target. its kinda right on the cusp where both have benefits and drawbacks.

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